diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000000..64fdb156d0
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,23 @@
+# files
+pp
+fpmake
+rtl/darwin/fpcmade.x86_64-darwin
+fpmake_proc1 copy.inc
+tests/*.x86_64-darwin
+rtl/Package.fpc
+tests/createlst
+tests/gparmake
+
+# directories
+lazbuild/
+x86_64-darwin/
+tests/tstunits/
+tests/utils
+
+# patterns
+*.app
+*.o
+*.ppu
+*.fpm
+*.rsj
+*.lst
\ No newline at end of file
diff --git a/compiler/defcmp.pas b/compiler/defcmp.pas
index 3f5882f762..793dbbbe76 100644
--- a/compiler/defcmp.pas
+++ b/compiler/defcmp.pas
@@ -175,7 +175,6 @@ implementation
       symtable,symsym,symcpu,
       defutil,symutil;
 
-
     function compare_defs_ext(def_from,def_to : tdef;
                               fromtreetype : tnodetype;
                               var doconv : tconverttype;
@@ -337,9 +336,13 @@ implementation
                        internalerror(2012091302);
                      symfrom:=ttypesym(tstoreddef(def_from).genericparas[i]);
                      symto:=ttypesym(tstoreddef(def_to).genericparas[i]);
-                     if not (symfrom.typ=typesym) or not (symto.typ=typesym) then
+                     if not (symfrom.typ in [typesym,constsym]) or not (symto.typ in [typesym,constsym]) then
                        internalerror(2012121401);
-                     if not equal_defs(ttypesym(symfrom).typedef,ttypesym(symto).typedef) then
+                     if symto.typ <> symfrom.typ then
+                       diff:=true
+                     else if (symfrom.typ=constsym) and (symto.typ=constsym) and not equal_constsym(tconstsym(symfrom),tconstsym(symto),true) then
+                       diff:=true
+                     else if not equal_defs(ttypesym(symfrom).typedef,ttypesym(symto).typedef) then
                        diff:=true;
                      if diff then
                        break;
diff --git a/compiler/htypechk.pas b/compiler/htypechk.pas
index 07c035dc26..bd51cebdf3 100644
--- a/compiler/htypechk.pas
+++ b/compiler/htypechk.pas
@@ -152,22 +152,22 @@ interface
     function token2managementoperator(optoken:ttoken):tmanagementoperator;
 
     { check operator args and result type }
-
-    type
-      toverload_check_flag = (
-        ocf_check_non_overloadable, { also check operators that are (currently) considered as
-                                      not overloadable (e.g. the "+" operator for dynamic arrays
-                                      if modeswitch arrayoperators is active) }
-        ocf_check_only              { only check whether the operator is overloaded, but don't
-                                      modify the passed in node (return true if the operator is
-                                      overloaded, false otherwise) }
-      );
-      toverload_check_flags = set of toverload_check_flag;
-
+
+    type
+      toverload_check_flag = (
+        ocf_check_non_overloadable, { also check operators that are (currently) considered as
+                                      not overloadable (e.g. the "+" operator for dynamic arrays
+                                      if modeswitch arrayoperators is active) }
+        ocf_check_only              { only check whether the operator is overloaded, but don't
+                                      modify the passed in node (return true if the operator is
+                                      overloaded, false otherwise) }
+      );
+      toverload_check_flags = set of toverload_check_flag;
+
     function isbinaryoperatoroverloadable(treetyp:tnodetype;ld:tdef;lt:tnodetype;rd:tdef;rt:tnodetype) : boolean;
     function isoperatoracceptable(pf : tprocdef; optoken : ttoken) : boolean;
-    function isunaryoverloaded(var t : tnode;ocf:toverload_check_flags) : boolean;
-    function isbinaryoverloaded(var t : tnode;ocf:toverload_check_flags) : boolean;
+    function isunaryoverloaded(var t : tnode;ocf:toverload_check_flags) : boolean;
+    function isbinaryoverloaded(var t : tnode;ocf:toverload_check_flags) : boolean;
 
     { Register Allocation }
     procedure make_not_regable(p : tnode; how: tregableinfoflags);
@@ -515,9 +515,9 @@ implementation
                     end;
 
                  { <dyn. array> + <dyn. array> is handled by the compiler }
-                 if (m_array_operators in current_settings.modeswitches) and
-                     (treetyp=addn) and
-                     (is_dynamic_array(ld) or is_dynamic_array(rd)) then
+                 if (m_array_operators in current_settings.modeswitches) and
+                     (treetyp=addn) and
+                     (is_dynamic_array(ld) or is_dynamic_array(rd)) then
                     begin
                       allowed:=false;
                       exit;
@@ -720,7 +720,7 @@ implementation
       end;
 
 
-    function isunaryoverloaded(var t : tnode;ocf:toverload_check_flags) : boolean;
+    function isunaryoverloaded(var t : tnode;ocf:toverload_check_flags) : boolean;
       var
         ld      : tdef;
         optoken : ttoken;
@@ -742,11 +742,11 @@ implementation
         else
           inlinenumber:=in_none;
 
-        if not (ocf_check_non_overloadable in ocf) and not isunaryoperatoroverloadable(t.nodetype,inlinenumber,ld) then
+        if not (ocf_check_non_overloadable in ocf) and not isunaryoperatoroverloadable(t.nodetype,inlinenumber,ld) then
           exit;
 
         { operator overload is possible }
-        result:=not (ocf_check_only in ocf);
+        result:=not (ocf_check_only in ocf);
 
         optoken:=NOTOKEN;
         case t.nodetype of
@@ -766,11 +766,11 @@ implementation
         end;
         if (optoken=NOTOKEN) then
           begin
-            if not (ocf_check_only in ocf) then
-              begin
-                CGMessage(parser_e_operator_not_overloaded);
-                t:=cnothingnode.create;
-              end;
+            if not (ocf_check_only in ocf) then
+              begin
+                CGMessage(parser_e_operator_not_overloaded);
+                t:=cnothingnode.create;
+              end;
             exit;
           end;
 
@@ -790,11 +790,11 @@ implementation
           begin
             candidates.free;
             ppn.free;
-            if not (ocf_check_only in ocf) then
-              begin
-                CGMessage2(parser_e_operator_not_overloaded_2,ld.typename,arraytokeninfo[optoken].str);
-                t:=cnothingnode.create;
-              end;
+            if not (ocf_check_only in ocf) then
+              begin
+                CGMessage2(parser_e_operator_not_overloaded_2,ld.typename,arraytokeninfo[optoken].str);
+                t:=cnothingnode.create;
+              end;
             exit;
           end;
 
@@ -811,16 +811,16 @@ implementation
           begin
             candidates.free;
             ppn.free;
-            if not (ocf_check_only in ocf) then
-              begin
-                CGMessage2(parser_e_operator_not_overloaded_2,ld.typename,arraytokeninfo[optoken].str);
-                t:=cnothingnode.create;
-              end;
+            if not (ocf_check_only in ocf) then
+              begin
+                CGMessage2(parser_e_operator_not_overloaded_2,ld.typename,arraytokeninfo[optoken].str);
+                t:=cnothingnode.create;
+              end;
             exit;
           end;
 
         { Multiple candidates left? }
-        if (cand_cnt>1) and not (ocf_check_only in ocf) then
+        if (cand_cnt>1) and not (ocf_check_only in ocf) then
           begin
             CGMessage(type_e_cant_choose_overload_function);
 {$ifdef EXTDEBUG}
@@ -833,13 +833,13 @@ implementation
           end;
         candidates.free;
 
-        if ocf_check_only in ocf then
-          begin
-            ppn.free;
-            result:=true;
-            exit;
-          end;
-
+        if ocf_check_only in ocf then
+          begin
+            ppn.free;
+            result:=true;
+            exit;
+          end;
+
         addsymref(operpd.procsym);
 
         { the nil as symtable signs firstcalln that this is
@@ -852,7 +852,7 @@ implementation
       end;
 
 
-    function isbinaryoverloaded(var t : tnode;ocf:toverload_check_flags) : boolean;
+    function isbinaryoverloaded(var t : tnode;ocf:toverload_check_flags) : boolean;
       var
         rd,ld   : tdef;
         optoken : ttoken;
@@ -945,14 +945,14 @@ implementation
         { load easier access variables }
         ld:=tbinarynode(t).left.resultdef;
         rd:=tbinarynode(t).right.resultdef;
-        if not (ocf_check_non_overloadable in ocf) and
-            not isbinaryoperatoroverloadable(t.nodetype,ld,tbinarynode(t).left.nodetype,rd,tbinarynode(t).right.nodetype) then
+        if not (ocf_check_non_overloadable in ocf) and
+            not isbinaryoperatoroverloadable(t.nodetype,ld,tbinarynode(t).left.nodetype,rd,tbinarynode(t).right.nodetype) then
           exit;
 
         { operator overload is possible }
-        { if we only check for the existance of the overload, then we assume that
-          it is not overloaded }
-        result:=not (ocf_check_only in ocf);
+        { if we only check for the existance of the overload, then we assume that
+          it is not overloaded }
+        result:=not (ocf_check_only in ocf);
 
         case t.nodetype of
            equaln:
@@ -997,19 +997,19 @@ implementation
              optoken:=_OP_IN;
            else
              begin
-               if not (ocf_check_only in ocf) then
-                 begin
-                   CGMessage(parser_e_operator_not_overloaded);
-                   t:=cnothingnode.create;
-                 end;
+               if not (ocf_check_only in ocf) then
+                 begin
+                   CGMessage(parser_e_operator_not_overloaded);
+                   t:=cnothingnode.create;
+                 end;
                exit;
              end;
         end;
 
-        cand_cnt:=search_operator(optoken,(optoken<>_NE) and not (ocf_check_only in ocf));
+        cand_cnt:=search_operator(optoken,(optoken<>_NE) and not (ocf_check_only in ocf));
 
         { no operator found for "<>" then search for "=" operator }
-        if (cand_cnt=0) and (optoken=_NE) and not (ocf_check_only in ocf) then
+        if (cand_cnt=0) and (optoken=_NE) and not (ocf_check_only in ocf) then
           begin
             ppn.free;
             ppn:=nil;
@@ -1021,15 +1021,15 @@ implementation
         if (cand_cnt=0) then
           begin
             ppn.free;
-            if not (ocf_check_only in ocf) then
-              t:=cnothingnode.create;
-            exit;
-          end;
-
-        if ocf_check_only in ocf then
-          begin
-            ppn.free;
-            result:=true;
+            if not (ocf_check_only in ocf) then
+              t:=cnothingnode.create;
+            exit;
+          end;
+
+        if ocf_check_only in ocf then
+          begin
+            ppn.free;
+            result:=true;
             exit;
           end;
 
@@ -2697,7 +2697,7 @@ implementation
               internalerror(2015060301);
             { check whether the given parameters are compatible
               to the def's constraints }
-            if not check_generic_constraints(pd,spezcontext.genericdeflist,spezcontext.poslist) then
+            if not check_generic_constraints(pd,spezcontext.paramlist,spezcontext.poslist) then
               exit;
             def:=generate_specialization_phase2(spezcontext,pd,false,'');
             case def.typ of
diff --git a/compiler/ncon.pas b/compiler/ncon.pas
index ae94637c28..e1617b3e96 100644
--- a/compiler/ncon.pas
+++ b/compiler/ncon.pas
@@ -311,11 +311,21 @@ implementation
             p1:=cpointerconstnode.create(p.value.valueordptr,p.constdef);
           constnil :
             p1:=cnilnode.create;
+          { constundefined is a placeholder for unrestricted generic const params
+            so we just treat it as a nil node. }
+          constundefined :
+            begin
+              p1:=cnilnode.create;
+              p1.resultdef := p.constdef;
+            end;
           constguid :
             p1:=cguidconstnode.create(pguid(p.value.valueptr)^);
           else
             internalerror(200205103);
         end;
+        { transfer generic param flag from symbol to node }
+        if sp_generic_para in p.symoptions then
+          include(p1.flags,nf_generic_para);
         genconstsymtree:=p1;
       end;
 
diff --git a/compiler/node.pas b/compiler/node.pas
index b8600000bf..f9ab8ec521 100644
--- a/compiler/node.pas
+++ b/compiler/node.pas
@@ -194,7 +194,8 @@ interface
           'loadparentfpn',
           'objcselectorn',
           'objcprotocoln',
-          'specializen');
+          'specializen'
+          );
 
       { a set containing all const nodes }
       nodetype_const = [ordconstn,
@@ -272,10 +273,13 @@ interface
          nf_block_with_exit,
 
          { tloadvmtaddrnode }
-         nf_ignore_for_wpo  { we know that this loadvmtaddrnode cannot be used to construct a class instance }
+         nf_ignore_for_wpo,  { we know that this loadvmtaddrnode cannot be used to construct a class instance }
 
-         { WARNING: there are now 31 elements in this type, and a set of this
-             type is written to the PPU. So before adding more than 32 elements,
+         { node is derived from generic parameter }
+         nf_generic_para
+
+         { WARNING: there are now 32 elements in this type, and a set of this
+             type is written to the PPU. So before adding more elements,
              either move some flags to specific nodes, or stream a normalset
              to the ppu
          }
@@ -1078,7 +1082,12 @@ implementation
     constructor tbinarynode.create(t:tnodetype;l,r : tnode);
       begin
          inherited create(t,l);
-         right:=r
+         { transfer generic paramater flag }
+         if assigned(l) and (nf_generic_para in l.flags) then
+           include(flags,nf_generic_para)
+         else if assigned(r) and (nf_generic_para in r.flags) then
+           include(flags,nf_generic_para);
+         right:=r;
       end;
 
 
diff --git a/compiler/nset.pas b/compiler/nset.pas
index 6270ec582e..bd031e6a86 100644
--- a/compiler/nset.pas
+++ b/compiler/nset.pas
@@ -239,7 +239,7 @@ implementation
            internalerror(20021126);
 
          t:=self;
-         if isbinaryoverloaded(t,[]) then
+         if isbinaryoverloaded(t,[]) then
            begin
              result:=t;
              exit;
@@ -392,8 +392,9 @@ implementation
          { both types must be compatible }
          if compare_defs(left.resultdef,right.resultdef,left.nodetype)=te_incompatible then
            IncompatibleTypes(left.resultdef,right.resultdef);
-         { Check if only when its a constant set }
-         if (left.nodetype=ordconstn) and (right.nodetype=ordconstn) then
+         { check if only when its a constant set and
+           ignore range nodes which are generic parameter derived }
+         if not (nf_generic_para in flags) and (left.nodetype=ordconstn) and (right.nodetype=ordconstn) then
           begin
             { upper limit must be greater or equal than lower limit }
             if (tordconstnode(left).value>tordconstnode(right).value) and
diff --git a/compiler/pdecl.pas b/compiler/pdecl.pas
index c5b5bcc921..583d00c17b 100644
--- a/compiler/pdecl.pas
+++ b/compiler/pdecl.pas
@@ -141,18 +141,18 @@ implementation
            typen :
              begin
                if is_interface(p.resultdef) then
-                begin
-                  if assigned(tobjectdef(p.resultdef).iidguid) then
-                   begin
-                     new(pg);
-                     pg^:=tobjectdef(p.resultdef).iidguid^;
-                     hp:=cconstsym.create_ptr(orgname,constguid,pg,p.resultdef);
-                   end
-                  else
-                   Message1(parser_e_interface_has_no_guid,tobjectdef(p.resultdef).objrealname^);
-                end
-               else
-                Message(parser_e_illegal_expression);
+                 begin
+                   if assigned(tobjectdef(p.resultdef).iidguid) then
+                     begin
+                       new(pg);
+                       pg^:=tobjectdef(p.resultdef).iidguid^;
+                       hp:=cconstsym.create_ptr(orgname,constguid,pg,p.resultdef);
+                     end
+                    else
+                      Message1(parser_e_interface_has_no_guid,tobjectdef(p.resultdef).objrealname^);
+                 end
+               else 
+                 Message(parser_e_illegal_expression);
              end;
            inlinen:
              begin
@@ -179,6 +179,9 @@ implementation
            else
              Message(parser_e_illegal_expression);
         end;
+        { transfer generic param flag from node to symbol }
+        if nf_generic_para in p.flags then
+          include(hp.symoptions,sp_generic_para);
         current_tokenpos:=storetokenpos;
         p.free;
         readconstant:=hp;
@@ -507,8 +510,9 @@ implementation
                { we are not freeing the type parameters, so register them }
                for i:=0 to generictypelist.count-1 do
                  begin
-                    ttypesym(generictypelist[i]).register_sym;
-                    tstoreddef(ttypesym(generictypelist[i]).typedef).register_def;
+                    tstoredsym(generictypelist[i]).register_sym;
+                    if tstoredsym(generictypelist[i]).typ=typesym then
+                      tstoreddef(ttypesym(generictypelist[i]).typedef).register_def;
                  end;
 
                str(generictypelist.Count,s);
diff --git a/compiler/pdecvar.pas b/compiler/pdecvar.pas
index 4d39397e46..8121d87853 100644
--- a/compiler/pdecvar.pas
+++ b/compiler/pdecvar.pas
@@ -1675,6 +1675,10 @@ implementation
                    end;
                end;
 
+             { field type is a generic param so set a flag in the struct }
+             if assigned(hdef.typesym) and (sp_generic_para in hdef.typesym.symoptions) then
+               include(current_structdef.defoptions,df_has_generic_fields);
+
              { Process procvar directives }
              if maybe_parse_proc_directives(hdef) then
                semicoloneaten:=true;
diff --git a/compiler/pexpr.pas b/compiler/pexpr.pas
index bc0606ed4b..e6d9633ebd 100644
--- a/compiler/pexpr.pas
+++ b/compiler/pexpr.pas
@@ -446,6 +446,9 @@ implementation
                   { no packed bit support for these things }
                   if l=in_bitsizeof_x then
                     statement_syssym:=caddnode.create(muln,statement_syssym,cordconstnode.create(8,sinttype,true));
+                  { type sym is a generic parameter }
+                  if assigned(p1.resultdef.typesym) and (sp_generic_para in p1.resultdef.typesym.symoptions) then
+                    include(statement_syssym.flags,nf_generic_para);
                 end
               else
                begin
@@ -466,6 +469,9 @@ implementation
                    end
                  else
                    statement_syssym:=cordconstnode.create(p1.resultdef.packedbitsize,sinttype,true);
+                 { type def is a struct with generic fields }
+                 if df_has_generic_fields in p1.resultdef.defoptions then
+                    include(statement_syssym.flags,nf_generic_para);
                  { p1 not needed !}
                  p1.destroy;
                end;
@@ -4078,7 +4084,10 @@ implementation
                 gendef:=generate_specialization_phase2(spezcontext,tstoreddef(gendef),false,'');
                 spezcontext.free;
                 spezcontext:=nil;
-                gensym:=gendef.typesym;
+                if gendef.typ=errordef then
+                  gensym:=generrorsym
+                else
+                  gensym:=gendef.typesym;
               end;
             procdef:
               begin
diff --git a/compiler/pgentype.pas b/compiler/pgentype.pas
index b2847c78f6..85270df256 100644
--- a/compiler/pgentype.pas
+++ b/compiler/pgentype.pas
@@ -28,7 +28,7 @@ interface
 uses
   cclasses,
   globtype,
-  symtype,symbase;
+  symconst,symtype,symbase;
 
 const
   inline_specialization_block_types = [bt_type,bt_var_type,bt_const_type,bt_body];
@@ -42,7 +42,7 @@ type
 
   tspecializationcontext=class
   public
-    genericdeflist : tfpobjectlist;
+    paramlist : tfpobjectlist;
     poslist : tfplist;
     prettyname : ansistring;
     specializename : ansistring;
@@ -58,7 +58,7 @@ implementation
 
 constructor tspecializationcontext.create;
 begin
-  genericdeflist:=tfpobjectlist.create(false);
+  paramlist:=tfpobjectlist.create(false);
   poslist:=tfplist.create;
 end;
 
@@ -66,7 +66,7 @@ destructor tspecializationcontext.destroy;
 var
   i : longint;
 begin
-  genericdeflist.free;
+  paramlist.free;
   for i:=0 to poslist.count-1 do
     dispose(pfileposinfo(poslist[i]));
   poslist.free;
diff --git a/compiler/pgenutil.pas b/compiler/pgenutil.pas
index 7760a4e134..33daf3b06a 100644
--- a/compiler/pgenutil.pas
+++ b/compiler/pgenutil.pas
@@ -42,9 +42,9 @@ uses
     function generate_specialization_phase1(out context:tspecializationcontext;genericdef:tdef;symname:string):tdef;inline;
     function generate_specialization_phase1(out context:tspecializationcontext;genericdef:tdef;parsedtype:tdef;symname:string;parsedpos:tfileposinfo):tdef;
     function generate_specialization_phase2(context:tspecializationcontext;genericdef:tstoreddef;parse_class_parent:boolean;_prettyname:ansistring):tdef;
-    function check_generic_constraints(genericdef:tstoreddef;paradeflist:tfpobjectlist;poslist:tfplist):boolean;
+    function check_generic_constraints(genericdef:tstoreddef;paramlist:tfpobjectlist;poslist:tfplist):boolean;
     function parse_generic_parameters(allowconstraints:boolean):tfphashobjectlist;
-    function parse_generic_specialization_types(genericdeflist:tfpobjectlist;poslist:tfplist;out prettyname,specializename:ansistring):boolean;
+    function parse_generic_specialization_types(paramlist:tfpobjectlist;poslist:tfplist;out prettyname,specializename:ansistring):boolean;
     procedure insert_generic_parameter_types(def:tstoreddef;genericdef:tstoreddef;genericlist:tfphashobjectlist);
     procedure maybe_insert_generic_rename_symbol(const name:tidstring;genericlist:tfphashobjectlist);
     function generate_generic_name(const name:tidstring;specializename:ansistring;owner_hierarchy:string):tidstring;
@@ -63,18 +63,163 @@ implementation
 
 uses
   { common }
-  cutils,fpccrc,
+  sysutils,cutils,fpccrc,
   { global }
-  globals,tokens,verbose,finput,
+  globals,tokens,verbose,finput,constexp,
   { symtable }
-  symconst,symsym,symtable,defcmp,procinfo,
+  symconst,symsym,symtable,defcmp,defutil,procinfo,
   { modules }
   fmodule,
-  node,nobj,
+  node,nobj,ncon,
   { parser }
   scanner,
   pbase,pexpr,pdecsub,ptype,psub;
 
+  type
+    tdeftypeset = set of tdeftyp;
+  const
+    tgeneric_param_const_types:tdeftypeset = [orddef,stringdef,arraydef,floatdef,setdef,pointerdef,undefineddef];
+    tgeneric_param_nodes: tnodetypeset = [typen,ordconstn,stringconstn,realconstn,setconstn,niln];
+
+    function get_generic_param_def(sym:tsym):tdef;
+      begin
+        if sym.typ = constsym then
+          result := tconstsym(sym).constdef
+        else
+          result := ttypesym(sym).typedef;
+      end;
+
+    function is_generic_param_const(sym:tsym):boolean;
+      begin
+        if sym.typ = constsym then
+          result := tconstsym(sym).consttyp<>constundefined
+        else
+          result := false;
+      end;
+
+    function compare_orddef_by_range(param1,param2:torddef;value:tconstvalue): boolean;
+      begin
+        if (value.len<param2.low) or (value.len>param2.high) then
+          result:=false
+        else
+          result:=true;
+      end;
+
+    function compare_generic_params(param1,param2:tdef;constparamsym:tconstsym):boolean;
+      begin
+        if (param1.typ=orddef) and (param2.typ=orddef) then
+          begin
+            if is_boolean(param2) then
+              result:=is_boolean(param1)
+            else if is_char(param2) then
+              result:=is_char(param1)
+            else if compare_orddef_by_range(torddef(param1),torddef(param2),constparamsym.value) then
+              result:=true
+            else
+              result:=false;
+          end
+        { arraydef is string constant so it's compatible with stringdef }
+        else if (param1.typ=arraydef) and (param2.typ=stringdef) then
+          result:=true
+        { integer ords are compatible with float }
+        else if (param1.typ=orddef) and is_integer(param1) and (param2.typ=floatdef) then
+          result:=true
+        { undefined def is compatible with all types }
+        else if param2.typ=undefineddef then
+          result:=true
+        { sets require stricter checks }
+        else if is_set(param2) then
+          result:=equal_defs(param1,param2)
+        else
+          result:=param1.typ=param2.typ;
+      end;
+
+    function create_generic_constsym(fromdef:tdef;node:tnode;out prettyname:string):tconstsym;
+      const
+        undefinedname = 'undefined';
+      var
+        sym : tconstsym;
+        setdef : tsetdef;
+        enumsym : tsym;
+        enumname : string;
+        sp : pchar;
+        ps : ^tconstset;
+        pd : ^bestreal;
+        i : integer;
+      begin
+        if node = nil then
+          begin
+            sym:=cconstsym.create_undefined(undefinedname,fromdef);
+            sym.owner:=fromdef.owner;
+            prettyname:='';
+            result:=sym;
+            exit;
+          end;
+        case node.nodetype of
+          ordconstn:
+            begin
+              sym:=cconstsym.create_ord(undefinedname,constord,tordconstnode(node).value,fromdef);
+              prettyname:=inttostr(tordconstnode(node).value.svalue);
+            end;
+          stringconstn:
+            begin
+              getmem(sp,tstringconstnode(node).len+1);
+              move(tstringconstnode(node).value_str^,sp^,tstringconstnode(node).len+1);
+              sym:=cconstsym.create_string(undefinedname,conststring,sp,tstringconstnode(node).len,fromdef);
+              prettyname:=''''+tstringconstnode(node).value_str+'''';
+            end;
+          realconstn:
+            begin
+              new(pd);
+              pd^:=trealconstnode(node).value_real;
+              sym:=cconstsym.create_ptr(undefinedname,constreal,pd,fromdef);
+              prettyname:=floattostr(trealconstnode(node).value_real);
+            end;
+          setconstn:
+            begin
+              new(ps);
+              ps^:=tsetconstnode(node).value_set^;
+              sym:=cconstsym.create_ptr(undefinedname,constset,ps,fromdef);
+              setdef:=tsetdef(tsetconstnode(node).resultdef);
+              prettyname:='[';
+              for i := setdef.setbase to setdef.setmax do
+                if i in tsetconstnode(node).value_set^ then
+                  begin
+                    if setdef.elementdef.typ=enumdef then
+                      enumsym:=tenumdef(setdef.elementdef).int2enumsym(i)
+                    else
+                      enumsym:=nil;
+                    if assigned(enumsym) then
+                      enumname:=enumsym.realname
+                    else if setdef.elementdef.typ=orddef then
+                      begin
+                        if torddef(setdef.elementdef).ordtype=uchar then
+                          enumname:=chr(i)
+                        else
+                          enumname:=tostr(i);
+                      end
+                    else
+                      enumname:=tostr(i);
+                    if length(prettyname) > 1 then
+                      prettyname:=prettyname+','+enumname
+                    else
+                      prettyname:=prettyname+enumname;
+                  end;
+              prettyname:=prettyname+']';
+            end;
+          niln:
+            begin
+              { only "nil" is available for pointer constants }
+              sym:=cconstsym.create_ord(undefinedname,constnil,0,fromdef);
+              prettyname:='nil';
+            end;
+          else
+            internalerror(2019021601);
+        end;
+        { the sym needs an owner for later checks so us the typeparam owner }
+        sym.owner:=fromdef.owner;
+        result:=sym;
+      end;
 
     procedure maybe_add_waiting_unit(tt:tdef);
       var
@@ -104,203 +249,232 @@ uses
           end;
       end;
 
-    function check_generic_constraints(genericdef:tstoreddef;paradeflist:tfpobjectlist;poslist:tfplist):boolean;
+    function check_generic_constraints(genericdef:tstoreddef;paramlist:tfpobjectlist;poslist:tfplist):boolean;
       var
         i,j,
         intfcount : longint;
         formaldef,
         paradef : tstoreddef;
+        genparadef : tdef;
         objdef,
         paraobjdef,
         formalobjdef : tobjectdef;
         intffound : boolean;
         filepos : tfileposinfo;
+        //paratype : tconsttyp;
+        is_const : boolean;
       begin
         { check whether the given specialization parameters fit to the eventual
           constraints of the generic }
         if not assigned(genericdef.genericparas) or (genericdef.genericparas.count=0) then
           internalerror(2012101001);
-        if genericdef.genericparas.count<>paradeflist.count then
+        if genericdef.genericparas.count<>paramlist.count then
           internalerror(2012101002);
-        if paradeflist.count<>poslist.count then
+        if paramlist.count<>poslist.count then
           internalerror(2012120801);
         result:=true;
         for i:=0 to genericdef.genericparas.count-1 do
           begin
             filepos:=pfileposinfo(poslist[i])^;
-            formaldef:=tstoreddef(ttypesym(genericdef.genericparas[i]).typedef);
-            if formaldef.typ=undefineddef then
-              { the parameter is of unspecified type, so no need to check }
-              continue;
-            if not (df_genconstraint in formaldef.defoptions) or
-                not assigned(formaldef.genconstraintdata) then
-              internalerror(2013021602);
-            paradef:=tstoreddef(paradeflist[i]);
-            { undefineddef is compatible with anything }
-            if formaldef.typ=undefineddef then
-              continue;
-            if paradef.typ<>formaldef.typ then
+            paradef:=tstoreddef(get_generic_param_def(tsym(paramlist[i])));
+            is_const:=is_generic_param_const(tsym(paramlist[i]));
+            genparadef:=genericdef.get_generic_param_def(i);
+            { validate const params }
+            if not genericdef.is_generic_param_const(i) and is_const then
               begin
-                case formaldef.typ of
-                  recorddef:
-                    { delphi has own fantasy about record constraint
-                      (almost non-nullable/non-nilable value type) }
-                    if m_delphi in current_settings.modeswitches then
-                      case paradef.typ of
-                        floatdef,enumdef,orddef:
-                          continue;
-                        objectdef:
-                          if tobjectdef(paradef).objecttype=odt_object then
-                            continue
-                          else
-                            MessagePos(filepos,type_e_record_type_expected);
+                MessagePos(filepos,type_e_mismatch);
+                exit(false);
+              end
+            else if genericdef.is_generic_param_const(i) then
+              begin
+                { param type mismatch (type <> const) }
+                 if genericdef.is_generic_param_const(i) <> is_const then
+                   begin
+                    MessagePos(filepos,type_e_mismatch);
+                    exit(false);
+                  end;
+                { type constrained param doesn't match type }
+                if not compare_generic_params(paradef,genericdef.get_generic_param_def(i),tconstsym(paramlist[i])) then
+                  begin
+                    MessagePos2(filepos,type_e_incompatible_types,FullTypeName(paradef,genparadef),FullTypeName(genparadef,paradef));
+                    exit(false);
+                  end;
+              end;
+            { test constraints for non-const params }
+            if not genericdef.is_generic_param_const(i) then
+              begin
+                formaldef:=tstoreddef(ttypesym(genericdef.genericparas[i]).typedef);
+                if formaldef.typ=undefineddef then
+                  { the parameter is of unspecified type, so no need to check }
+                  continue;
+                if not (df_genconstraint in formaldef.defoptions) or
+                    not assigned(formaldef.genconstraintdata) then
+                  internalerror(2013021602);
+                { undefineddef is compatible with anything }
+                if formaldef.typ=undefineddef then
+                  continue;
+                if paradef.typ<>formaldef.typ then
+                  begin
+                    case formaldef.typ of
+                      recorddef:
+                        { delphi has own fantasy about record constraint
+                          (almost non-nullable/non-nilable value type) }
+                        if m_delphi in current_settings.modeswitches then
+                          case paradef.typ of
+                            floatdef,enumdef,orddef:
+                              continue;
+                            objectdef:
+                              if tobjectdef(paradef).objecttype=odt_object then
+                                continue
+                              else
+                                MessagePos(filepos,type_e_record_type_expected);
+                            else
+                              MessagePos(filepos,type_e_record_type_expected);
+                          end
                         else
                           MessagePos(filepos,type_e_record_type_expected);
-                      end
-                    else
-                      MessagePos(filepos,type_e_record_type_expected);
-                  objectdef:
-                    case tobjectdef(formaldef).objecttype of
-                      odt_class,
-                      odt_javaclass:
-                        MessagePos1(filepos,type_e_class_type_expected,paradef.typename);
-                      odt_interfacecom,
-                      odt_interfacecorba,
-                      odt_dispinterface,
-                      odt_interfacejava:
-                        MessagePos1(filepos,type_e_interface_type_expected,paradef.typename);
+                      objectdef:
+                        case tobjectdef(formaldef).objecttype of
+                          odt_class,
+                          odt_javaclass:
+                            MessagePos1(filepos,type_e_class_type_expected,paradef.typename);
+                          odt_interfacecom,
+                          odt_interfacecorba,
+                          odt_dispinterface,
+                          odt_interfacejava:
+                            MessagePos1(filepos,type_e_interface_type_expected,paradef.typename);
+                          else
+                            internalerror(2012101003);
+                        end;
+                      errordef:
+                        { ignore }
+                        ;
                       else
-                        internalerror(2012101003);
+                        internalerror(2012101004);
                     end;
-                  errordef:
-                    { ignore }
-                    ;
-                  else
-                    internalerror(2012101004);
-                end;
-                result:=false;
-              end
-            else
-              begin
-                { the paradef types are the same, so do special checks for the
-                  cases in which they are needed }
-                if formaldef.typ=objectdef then
+                    result:=false;
+                  end
+                else
                   begin
-                    paraobjdef:=tobjectdef(paradef);
-                    formalobjdef:=tobjectdef(formaldef);
-                    if not (formalobjdef.objecttype in [odt_class,odt_javaclass,odt_interfacecom,odt_interfacecorba,odt_interfacejava,odt_dispinterface]) then
-                      internalerror(2012101102);
-                    if formalobjdef.objecttype in [odt_interfacecom,odt_interfacecorba,odt_interfacejava,odt_dispinterface] then
+                    { the paradef types are the same, so do special checks for the
+                      cases in which they are needed }
+                    if formaldef.typ=objectdef then
                       begin
-                        { this is either a concerete interface or class type (the
-                          latter without specific implemented interfaces) }
-                        case paraobjdef.objecttype of
-                          odt_interfacecom,
-                          odt_interfacecorba,
-                          odt_interfacejava,
-                          odt_dispinterface:
-                            begin
-                              if (oo_is_forward in paraobjdef.objectoptions) and
-                                  (paraobjdef.objecttype=formalobjdef.objecttype) and
-                                  (df_genconstraint in formalobjdef.defoptions) and
-                                  (
-                                    (formalobjdef.objecttype=odt_interfacecom) and
-                                    (formalobjdef.childof=interface_iunknown)
-                                  )
-                                  or
-                                  (
-                                    (formalobjdef.objecttype=odt_interfacecorba) and
-                                    (formalobjdef.childof=nil)
-                                  ) then
-                                continue;
-                              if not def_is_related(paraobjdef,formalobjdef.childof) then
+                        paraobjdef:=tobjectdef(paradef);
+                        formalobjdef:=tobjectdef(formaldef);
+                        if not (formalobjdef.objecttype in [odt_class,odt_javaclass,odt_interfacecom,odt_interfacecorba,odt_interfacejava,odt_dispinterface]) then
+                          internalerror(2012101102);
+                        if formalobjdef.objecttype in [odt_interfacecom,odt_interfacecorba,odt_interfacejava,odt_dispinterface] then
+                          begin
+                            { this is either a concerete interface or class type (the
+                              latter without specific implemented interfaces) }
+                            case paraobjdef.objecttype of
+                              odt_interfacecom,
+                              odt_interfacecorba,
+                              odt_interfacejava,
+                              odt_dispinterface:
                                 begin
-                                  MessagePos2(filepos,type_e_incompatible_types,paraobjdef.typename,formalobjdef.childof.typename);
-                                  result:=false;
+                                  if (oo_is_forward in paraobjdef.objectoptions) and
+                                      (paraobjdef.objecttype=formalobjdef.objecttype) and
+                                      (df_genconstraint in formalobjdef.defoptions) and
+                                      (
+                                        (formalobjdef.objecttype=odt_interfacecom) and
+                                        (formalobjdef.childof=interface_iunknown)
+                                      )
+                                      or
+                                      (
+                                        (formalobjdef.objecttype=odt_interfacecorba) and
+                                        (formalobjdef.childof=nil)
+                                      ) then
+                                    continue;
+                                  if not def_is_related(paraobjdef,formalobjdef.childof) then
+                                    begin
+                                      MessagePos2(filepos,type_e_incompatible_types,paraobjdef.typename,formalobjdef.childof.typename);
+                                      result:=false;
+                                    end;
                                 end;
-                            end;
-                          odt_class,
-                          odt_javaclass:
-                            begin
-                              objdef:=paraobjdef;
-                              intffound:=false;
-                              while assigned(objdef) do
+                              odt_class,
+                              odt_javaclass:
                                 begin
-                                  for j:=0 to objdef.implementedinterfaces.count-1 do
-                                    if timplementedinterface(objdef.implementedinterfaces[j]).intfdef=formalobjdef.childof then
-                                      begin
-                                        intffound:=true;
+                                  objdef:=paraobjdef;
+                                  intffound:=false;
+                                  while assigned(objdef) do
+                                    begin
+                                      for j:=0 to objdef.implementedinterfaces.count-1 do
+                                        if timplementedinterface(objdef.implementedinterfaces[j]).intfdef=formalobjdef.childof then
+                                          begin
+                                            intffound:=true;
+                                            break;
+                                          end;
+                                      if intffound then
                                         break;
-                                      end;
-                                  if intffound then
-                                    break;
-                                  objdef:=objdef.childof;
+                                      objdef:=objdef.childof;
+                                    end;
+                                  result:=intffound;
+                                  if not result then
+                                    MessagePos2(filepos,parser_e_class_doesnt_implement_interface,paraobjdef.typename,formalobjdef.childof.typename);
+                                end;
+                              else
+                                begin
+                                  MessagePos1(filepos,type_e_class_or_interface_type_expected,paraobjdef.typename);
+                                  result:=false;
                                 end;
-                              result:=intffound;
-                              if not result then
-                                MessagePos2(filepos,parser_e_class_doesnt_implement_interface,paraobjdef.typename,formalobjdef.childof.typename);
-                            end;
-                          else
-                            begin
-                              MessagePos1(filepos,type_e_class_or_interface_type_expected,paraobjdef.typename);
-                              result:=false;
                             end;
-                        end;
-                      end
-                    else
-                      begin
-                        { this is either a "class" or a concrete instance with
-                          or without implemented interfaces }
-                        if not (paraobjdef.objecttype in [odt_class,odt_javaclass]) then
-                          begin
-                            MessagePos1(filepos,type_e_class_type_expected,paraobjdef.typename);
-                            result:=false;
-                            continue;
-                          end;
-                        { for forward declared classes we allow pure TObject/class declarations }
-                        if (oo_is_forward in paraobjdef.objectoptions) and
-                            (df_genconstraint in formaldef.defoptions) then
-                          begin
-                            if (formalobjdef.childof=class_tobject) and
-                                not formalobjdef.implements_any_interfaces then
-                              continue;
-                          end;
-                        if assigned(formalobjdef.childof) and
-                            not def_is_related(paradef,formalobjdef.childof) then
-                          begin
-                            MessagePos2(filepos,type_e_incompatible_types,paraobjdef.typename,formalobjdef.childof.typename);
-                            result:=false;
-                          end;
-                        intfcount:=0;
-                        for j:=0 to formalobjdef.implementedinterfaces.count-1 do
+                          end
+                        else
                           begin
-                            objdef:=paraobjdef;
-                            while assigned(objdef) do
+                            { this is either a "class" or a concrete instance with
+                              or without implemented interfaces }
+                            if not (paraobjdef.objecttype in [odt_class,odt_javaclass]) then
                               begin
-                                intffound:=assigned(
-                                             find_implemented_interface(objdef,
-                                               timplementedinterface(formalobjdef.implementedinterfaces[j]).intfdef
-                                             )
-                                           );
+                                MessagePos1(filepos,type_e_class_type_expected,paraobjdef.typename);
+                                result:=false;
+                                continue;
+                              end;
+                            { for forward declared classes we allow pure TObject/class declarations }
+                            if (oo_is_forward in paraobjdef.objectoptions) and
+                                (df_genconstraint in formaldef.defoptions) then
+                              begin
+                                if (formalobjdef.childof=class_tobject) and
+                                    not formalobjdef.implements_any_interfaces then
+                                  continue;
+                              end;
+                            if assigned(formalobjdef.childof) and
+                                not def_is_related(paradef,formalobjdef.childof) then
+                              begin
+                                MessagePos2(filepos,type_e_incompatible_types,paraobjdef.typename,formalobjdef.childof.typename);
+                                result:=false;
+                              end;
+                            intfcount:=0;
+                            for j:=0 to formalobjdef.implementedinterfaces.count-1 do
+                              begin
+                                objdef:=paraobjdef;
+                                while assigned(objdef) do
+                                  begin
+                                    intffound:=assigned(
+                                                 find_implemented_interface(objdef,
+                                                   timplementedinterface(formalobjdef.implementedinterfaces[j]).intfdef
+                                                 )
+                                               );
+                                    if intffound then
+                                      break;
+                                    objdef:=objdef.childof;
+                                  end;
                                 if intffound then
-                                  break;
-                                objdef:=objdef.childof;
+                                  inc(intfcount)
+                                else
+                                  MessagePos2(filepos,parser_e_class_doesnt_implement_interface,paraobjdef.typename,timplementedinterface(formalobjdef.implementedinterfaces[j]).intfdef.typename);
                               end;
-                            if intffound then
-                              inc(intfcount)
-                            else
-                              MessagePos2(filepos,parser_e_class_doesnt_implement_interface,paraobjdef.typename,timplementedinterface(formalobjdef.implementedinterfaces[j]).intfdef.typename);
+                            if intfcount<>formalobjdef.implementedinterfaces.count then
+                              result:=false;
                           end;
-                        if intfcount<>formalobjdef.implementedinterfaces.count then
-                          result:=false;
                       end;
                   end;
               end;
           end;
       end;
 
-
-    function parse_generic_specialization_types_internal(genericdeflist:tfpobjectlist;poslist:tfplist;out prettyname,specializename:ansistring;parsedtype:tdef;parsedpos:tfileposinfo):boolean;
+    function parse_generic_specialization_types_internal(paramlist:tfpobjectlist;poslist:tfplist;out prettyname,specializename:ansistring;parsedtype:tdef;parsedpos:tfileposinfo):boolean;
       var
         old_block_type : tblock_type;
         first : boolean;
@@ -310,9 +484,12 @@ uses
         namepart : string;
         prettynamepart : ansistring;
         module : tmodule;
+        //paramdef : tgenericparamdef;
+        constprettyname : string;
+        validparam : boolean;
       begin
         result:=true;
-        if genericdeflist=nil then
+        if paramlist=nil then
           internalerror(2012061401);
         { set the block type to type, so that the parsed type are returned as
           ttypenode (e.g. classes are in non type-compatible blocks returned as
@@ -324,7 +501,7 @@ uses
         first:=not assigned(parsedtype);
         if assigned(parsedtype) then
           begin
-            genericdeflist.Add(parsedtype);
+            paramlist.Add(parsedtype.typesym);
             module:=find_module_from_symtable(parsedtype.owner);
             if not assigned(module) then
               internalerror(2016112801);
@@ -351,7 +528,9 @@ uses
             block_type:=bt_type;
             tmpparampos:=current_filepos;
             typeparam:=factor(false,[ef_type_only]);
-            if typeparam.nodetype=typen then
+            { determine if the typeparam node is a valid type or const }
+            validparam:=typeparam.nodetype in tgeneric_param_nodes;
+            if validparam then
               begin
                 if tstoreddef(typeparam.resultdef).is_generic and
                     (
@@ -367,31 +546,47 @@ uses
                   end;
                 if typeparam.resultdef.typ<>errordef then
                   begin
-                    if not assigned(typeparam.resultdef.typesym) then
+                    if (typeparam.nodetype = typen) and not assigned(typeparam.resultdef.typesym) then
                       message(type_e_generics_cannot_reference_itself)
-                    else if (typeparam.resultdef.typ<>errordef) then
+                    else 
+                    if (typeparam.resultdef.typ<>errordef) then
                       begin
-                        genericdeflist.Add(typeparam.resultdef);
+                        { all non-type nodes are considered const }
+                        if typeparam.nodetype <> typen then
+                          paramlist.Add(create_generic_constsym(typeparam.resultdef,typeparam,constprettyname))
+                        else
+                          begin
+                            constprettyname:='';
+                            paramlist.Add(typeparam.resultdef.typesym);
+                          end;
                         module:=find_module_from_symtable(typeparam.resultdef.owner);
                         if not assigned(module) then
                           internalerror(2016112802);
                         namepart:='_$'+hexstr(module.moduleid,8)+'$$'+typeparam.resultdef.unique_id_str;
+                        if constprettyname <> '' then
+                          namepart:=namepart+'$$'+constprettyname;
                         { we use the full name of the type to uniquely identify it }
-                        if (symtablestack.top.symtabletype=parasymtable) and
-                            (symtablestack.top.defowner.typ=procdef) and
-                            (typeparam.resultdef.owner=symtablestack.top) then
-                          begin
-                            { special handling for specializations inside generic function declarations }
-                            prettynamepart:=tdef(symtablestack.top.defowner).fullownerhierarchyname(true)+tprocdef(symtablestack.top.defowner).procsym.prettyname;
-                          end
-                        else
+                        if typeparam.nodetype = typen then
                           begin
-                            prettynamepart:=typeparam.resultdef.fullownerhierarchyname(true);
+                            if (symtablestack.top.symtabletype=parasymtable) and
+                                (symtablestack.top.defowner.typ=procdef) and
+                                (typeparam.resultdef.owner=symtablestack.top) then
+                              begin
+                                { special handling for specializations inside generic function declarations }
+                                prettynamepart:=tdef(symtablestack.top.defowner).fullownerhierarchyname(true)+tprocdef(symtablestack.top.defowner).procsym.prettyname;
+                              end
+                            else
+                              begin
+                                prettynamepart:=typeparam.resultdef.fullownerhierarchyname(true);
+                              end;
                           end;
                         specializename:=specializename+namepart;
                         if not first then
                           prettyname:=prettyname+',';
-                        prettyname:=prettyname+prettynamepart+typeparam.resultdef.typesym.prettyname;
+                        if constprettyname <> '' then
+                          prettyname:=prettyname+constprettyname
+                        else
+                          prettyname:=prettyname+prettynamepart+typeparam.resultdef.typesym.prettyname;
                       end;
                   end
                 else
@@ -411,12 +606,12 @@ uses
       end;
 
 
-    function parse_generic_specialization_types(genericdeflist:tfpobjectlist;poslist:tfplist;out prettyname,specializename:ansistring):boolean;
+    function parse_generic_specialization_types(paramlist:tfpobjectlist;poslist:tfplist;out prettyname,specializename:ansistring):boolean;
       var
         dummypos : tfileposinfo;
       begin
         FillChar(dummypos, SizeOf(tfileposinfo), 0);
-        result:=parse_generic_specialization_types_internal(genericdeflist,poslist,prettyname,specializename,nil,dummypos);
+        result:=parse_generic_specialization_types_internal(paramlist,poslist,prettyname,specializename,nil,dummypos);
       end;
 
 
@@ -578,7 +773,7 @@ uses
         context:=tspecializationcontext.create;
 
         { Parse type parameters }
-        err:=not parse_generic_specialization_types_internal(context.genericdeflist,context.poslist,context.prettyname,context.specializename,parsedtype,parsedpos);
+        err:=not parse_generic_specialization_types_internal(context.paramlist,context.poslist,context.prettyname,context.specializename,parsedtype,parsedpos);
         if err then
           begin
             if not try_to_consume(_GT) then
@@ -627,7 +822,7 @@ uses
 
         { search a generic with the given count of params }
         countstr:='';
-        str(context.genericdeflist.Count,countstr);
+        str(context.paramlist.Count,countstr);
 
         genname:=genname+'$'+countstr;
         ugenname:=upper(genname);
@@ -656,7 +851,7 @@ uses
             result:=generrordef;
             exit;
           end;
-
+        
         { we've found the correct def }
         if context.sym.typ=typesym then
           result:=tstoreddef(ttypesym(context.sym).typedef)
@@ -747,6 +942,7 @@ uses
         hintsprocessed : boolean;
         pd : tprocdef;
         pdflags : tpdflags;
+        typedef : tstoreddef;
       begin
         if not assigned(context) then
           internalerror(2015052203);
@@ -755,7 +951,7 @@ uses
 
         pd:=nil;
 
-        if not check_generic_constraints(genericdef,context.genericdeflist,context.poslist) then
+        if not check_generic_constraints(genericdef,context.paramlist,context.poslist) then
           begin
             { the parameters didn't fit the constraints, so don't continue with the
               specialization }
@@ -771,20 +967,19 @@ uses
         else
           prettyname:=genericdef.typesym.prettyname;
         prettyname:=prettyname+'<'+context.prettyname+'>';
-
         generictypelist:=tfphashobjectlist.create(false);
 
         { build the list containing the types for the generic params }
         if not assigned(genericdef.genericparas) then
           internalerror(2013092601);
-        if context.genericdeflist.count<>genericdef.genericparas.count then
+        if context.paramlist.count<>genericdef.genericparas.count then
           internalerror(2013092603);
         for i:=0 to genericdef.genericparas.Count-1 do
           begin
             srsym:=tsym(genericdef.genericparas[i]);
             if not (sp_generic_para in srsym.symoptions) then
               internalerror(2013092602);
-            generictypelist.add(srsym.realname,tdef(context.genericdeflist[i]).typesym);
+            generictypelist.add(srsym.realname,context.paramlist[i]);
           end;
 
         { Special case if we are referencing the current defined object }
@@ -1196,8 +1391,8 @@ uses
 
     function parse_generic_parameters(allowconstraints:boolean):tfphashobjectlist;
       var
-        generictype : ttypesym;
-        i,firstidx : longint;
+        generictype : tstoredsym;
+        i,firstidx,const_list_index : longint;
         srsymtable : tsymtable;
         basedef,def : tdef;
         defname : tidstring;
@@ -1205,22 +1400,87 @@ uses
         doconsume : boolean;
         constraintdata : tgenericconstraintdata;
         old_block_type : tblock_type;
+        is_const,last_is_const : boolean;
+        last_token : ttoken;
+        last_type_pos : tfileposinfo;
       begin
         result:=tfphashobjectlist.create(false);
         firstidx:=0;
+        const_list_index:=0;
         old_block_type:=block_type;
         block_type:=bt_type;
+        is_const:=false;
+        last_is_const:=false;
+        last_token:=NOTOKEN;
         repeat
+          if try_to_consume(_CONST) then
+            begin
+              { last param was const without semicolon terminator }
+              if (result.count>0) and last_is_const and (last_token<>_SEMICOLON) then
+                MessagePos2(last_type_pos,scan_f_syn_expected,arraytokeninfo[_SEMICOLON].str,arraytokeninfo[last_token].str);
+              is_const := true;
+              const_list_index := result.count;
+            end;
           if token=_ID then
             begin
-              generictype:=ctypesym.create(orgpattern,cundefinedtype,false);
+              if is_const then
+                begin
+                  { last param was type without semicolon terminator }
+                  if (result.count>0) and not last_is_const and (last_token<>_SEMICOLON) then
+                    MessagePos2(last_type_pos,scan_f_syn_expected,arraytokeninfo[_SEMICOLON].str,arraytokeninfo[last_token].str);
+                  generictype:=tconstsym.create_undefined(orgpattern,cundefinedtype);
+                end
+              else
+                begin
+                  { last param was const without semicolon terminator }
+                  if (result.count>0) and last_is_const and (last_token<>_SEMICOLON) then
+                    MessagePos2(last_type_pos,scan_f_syn_expected,arraytokeninfo[_SEMICOLON].str,arraytokeninfo[last_token].str);
+                  generictype:=ttypesym.create(orgpattern,cundefinedtype,false);
+                end;
               { type parameters need to be added as strict private }
               generictype.visibility:=vis_strictprivate;
               include(generictype.symoptions,sp_generic_para);
               result.add(orgpattern,generictype);
+              last_is_const:=is_const;
             end;
           consume(_ID);
-          if try_to_consume(_COLON) then
+          { const restriction }
+          if is_const then
+            begin
+              if try_to_consume(_COLON) then
+                begin
+                  def := nil;
+                  { parse the type and assign the const type to generictype  }
+                  single_type(def,[]);
+                  for i:=const_list_index to result.count-1 do
+                    begin
+                      { finalize constant information once type is known }
+                      if assigned(def) and (def.typ in tgeneric_param_const_types) then
+                        begin
+                          case def.typ of
+                            orddef:
+                              tconstsym(result[i]).consttyp:=constord;
+                            stringdef:
+                              tconstsym(result[i]).consttyp:=conststring;
+                            floatdef:
+                              tconstsym(result[i]).consttyp:=constreal;
+                            setdef:
+                              tconstsym(result[i]).consttyp:=constset;
+                            { pointer always refers to nil with constants }
+                            pointerdef:
+                              tconstsym(result[i]).consttyp:=constnil;
+                          end;
+                          tconstsym(result[i]).constdef:=def;
+                        end
+                      else
+                        Message(type_e_mismatch);
+                    end;
+                  { after type restriction const list terminates }
+                  is_const:=false;
+                end;
+            end
+          { type restriction }
+          else if try_to_consume(_COLON) then
             begin
               if not allowconstraints then
                 { TODO }
@@ -1335,6 +1595,7 @@ uses
                     basedef:=cobjectdef.create(tobjectdef(def).objecttype,defname,tobjectdef(def),false);
                     constraintdata.interfaces.delete(0);
                   end;
+
               if basedef.typ<>errordef then
                 with tstoreddef(basedef) do
                   begin
@@ -1360,21 +1621,27 @@ uses
                 begin
                   { two different typeless parameters are considered as incompatible }
                   for i:=firstidx to result.count-1 do
-                    begin
-                      ttypesym(result[i]).typedef:=cundefineddef.create(false);
-                      ttypesym(result[i]).typedef.typesym:=ttypesym(result[i]);
-                    end;
+                    if tsym(result[i]).typ<>constsym then
+                      begin
+                        ttypesym(result[i]).typedef:=cundefineddef.create(false);
+                        ttypesym(result[i]).typedef.typesym:=ttypesym(result[i]);
+                      end;
                   { a semicolon terminates a type parameter group }
                   firstidx:=result.count;
                 end;
             end;
+          if token = _SEMICOLON then
+            is_const:=false;
+          last_token:=token;
+          last_type_pos:=current_filepos;
         until not (try_to_consume(_COMMA) or try_to_consume(_SEMICOLON));
         { two different typeless parameters are considered as incompatible }
         for i:=firstidx to result.count-1 do
-          begin
-            ttypesym(result[i]).typedef:=cundefineddef.create(false);
-            ttypesym(result[i]).typedef.typesym:=ttypesym(result[i]);
-          end;
+          if tsym(result[i]).typ<>constsym then
+            begin
+              ttypesym(result[i]).typedef:=cundefineddef.create(false);
+              ttypesym(result[i]).typedef.typesym:=ttypesym(result[i]);
+            end;
         block_type:=old_block_type;
       end;
 
@@ -1382,7 +1649,9 @@ uses
     procedure insert_generic_parameter_types(def:tstoreddef;genericdef:tstoreddef;genericlist:tfphashobjectlist);
       var
         i : longint;
-        generictype,sym : ttypesym;
+        generictype : tstoredsym;
+        generictypedef : tdef;
+        sym : tsym;
         st : tsymtable;
       begin
         def.genericdef:=genericdef;
@@ -1407,10 +1676,22 @@ uses
           def.genericparas:=tfphashobjectlist.create(false);
         for i:=0 to genericlist.count-1 do
           begin
-            generictype:=ttypesym(genericlist[i]);
+            generictype:=tstoredsym(genericlist[i]);
             if assigned(generictype.owner) then
               begin
-                sym:=ctypesym.create(genericlist.nameofindex(i),generictype.typedef,true);
+                if generictype.typ=typesym then
+                  sym:=ctypesym.create(genericlist.nameofindex(i),ttypesym(generictype).typedef,true)
+                else if generictype.typ=constsym then
+                  { generictype is a constsym that was created in create_generic_constsym 
+                    during phase 1 so we pass this directly without copying }
+                  begin
+                    sym:=generictype;
+                    { the sym name is still undefined so we set it to match
+                      the generic param name so it's accessible }
+                    sym.realname:=genericlist.nameofindex(i);
+                  end
+                else
+                  internalerror(2019021602);
                 { type parameters need to be added as strict private }
                 sym.visibility:=vis_strictprivate;
                 st.insert(sym);
@@ -1418,13 +1699,17 @@ uses
               end
             else
               begin
-                if (generictype.typedef.typ=undefineddef) and (generictype.typedef<>cundefinedtype) then
+                if generictype.typ=typesym then
                   begin
-                    { the generic parameters were parsed before the genericdef existed thus the
-                      undefineddefs were added as part of the parent symtable }
-                    if assigned(generictype.typedef.owner) then
-                      generictype.typedef.owner.DefList.Extract(generictype.typedef);
-                    generictype.typedef.changeowner(st);
+                    generictypedef:=ttypesym(generictype).typedef;
+                    if (generictypedef.typ=undefineddef) and (generictypedef<>cundefinedtype) then
+                      begin
+                        { the generic parameters were parsed before the genericdef existed thus the
+                          undefineddefs were added as part of the parent symtable }
+                        if assigned(generictypedef.owner) then
+                          generictypedef.owner.DefList.Extract(generictypedef);
+                        generictypedef.changeowner(st);
+                      end;
                   end;
                 st.insert(generictype);
                 include(generictype.symoptions,sp_generic_para);
diff --git a/compiler/ppu.pas b/compiler/ppu.pas
index 10c42e7eb8..31011be3e8 100644
--- a/compiler/ppu.pas
+++ b/compiler/ppu.pas
@@ -43,7 +43,7 @@ type
 {$endif Test_Double_checksum}
 
 const
-  CurrentPPUVersion = 201;
+  CurrentPPUVersion = 203;
 
 { unit flags }
   uf_init                = $000001; { unit has initialization section }
diff --git a/compiler/ptype.pas b/compiler/ptype.pas
index 38e2526e9f..28cd0f94f8 100644
--- a/compiler/ptype.pas
+++ b/compiler/ptype.pas
@@ -1436,7 +1436,9 @@ implementation
                                  highval:=tordconstnode(trangenode(pt).right).value;
                                  if highval<lowval then
                                   begin
-                                    Message(parser_e_array_lower_less_than_upper_bound);
+                                    { ignore error if node is generic param }
+                                    if not (nf_generic_para in pt.flags) then
+                                      Message(parser_e_array_lower_less_than_upper_bound);
                                     highval:=lowval;
                                   end
                                  else if (lowval<int64(low(asizeint))) or
diff --git a/compiler/ryan_ppcx64.lpi b/compiler/ryan_ppcx64.lpi
new file mode 100644
index 0000000000..68008e4ab3
--- /dev/null
+++ b/compiler/ryan_ppcx64.lpi
@@ -0,0 +1,77 @@
+<?xml version="1.0"?>
+<CONFIG>
+  <ProjectOptions>
+    <Version Value="9"/>
+    <PathDelim Value="\"/>
+    <General>
+      <Flags>
+        <MainUnitHasUsesSectionForAllUnits Value="False"/>
+        <MainUnitHasCreateFormStatements Value="False"/>
+        <MainUnitHasTitleStatement Value="False"/>
+        <LRSInOutputDirectory Value="False"/>
+      </Flags>
+      <SessionStorage Value="InProjectDir"/>
+      <MainUnit Value="0"/>
+      <Title Value="ppcx64"/>
+    </General>
+    <BuildModes Count="1">
+      <Item1 Name="default" Default="True"/>
+    </BuildModes>
+    <PublishOptions>
+      <Version Value="2"/>
+      <DestinationDirectory Value="$(TestDir)\publishedproject\"/>
+      <IncludeFileFilter Value="*.(pas|pp|inc|lfm|lpr|lrs|lpi|lpk|sh|xml)"/>
+      <ExcludeFileFilter Value="*.(bak|ppu|ppw|o|so);*~;backup"/>
+    </PublishOptions>
+    <RunParams>
+      <local>
+        <FormatVersion Value="1"/>
+        <LaunchingApplication PathPlusParams="/usr/X11R6/bin/xterm -T 'Lazarus Run Output' -e $(LazarusDir)/tools/runwait.sh $(TargetCmdLine)"/>
+      </local>
+    </RunParams>
+    <Units Count="2">
+      <Unit0>
+        <Filename Value="pp.pas"/>
+        <IsPartOfProject Value="True"/>
+        <UnitName Value="pp"/>
+      </Unit0>
+      <Unit1>
+        <Filename Value="x86\aasmcpu.pas"/>
+        <IsPartOfProject Value="True"/>
+        <UnitName Value="aasmcpu"/>
+      </Unit1>
+    </Units>
+  </ProjectOptions>
+  <CompilerOptions>
+    <Version Value="11"/>
+    <PathDelim Value="\"/>
+    <Target>
+      <Filename Value="x86_64\pp"/>
+    </Target>
+    <SearchPaths>
+      <IncludeFiles Value="x86_64"/>
+      <OtherUnitFiles Value="x86_64;x86;systems"/>
+      <UnitOutputDirectory Value="x86_64\lazbuild"/>
+    </SearchPaths>
+    <Parsing>
+      <SyntaxOptions>
+        <CStyleOperator Value="False"/>
+        <AllowLabel Value="False"/>
+        <CPPInline Value="False"/>
+        <UseAnsiStrings Value="False"/>
+      </SyntaxOptions>
+    </Parsing>
+    <Other>
+      <Verbosity>
+        <ShowWarn Value="False"/>
+        <ShowNotes Value="False"/>
+        <ShowHints Value="False"/>
+      </Verbosity>
+      <ConfigFile>
+        <StopAfterErrCount Value="50"/>
+      </ConfigFile>
+      <CustomOptions Value="-dx86_64 -gw -godwarfcpp -Fl/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/lib"/>
+      <CompilerPath Value="$(CompPath)"/>
+    </Other>
+  </CompilerOptions>
+</CONFIG>
diff --git a/compiler/symconst.pas b/compiler/symconst.pas
index a5ae7e0fb9..e02ce3a8ca 100644
--- a/compiler/symconst.pas
+++ b/compiler/symconst.pas
@@ -232,7 +232,10 @@ type
       because we have to access this information in the symtable unit }
     df_llvm_no_struct_packing,
     { internal def that's not for any export }
-    df_internal
+    df_internal,
+    { the def was derived with generic type or const fields so the size
+      of the def can not be determined }
+    df_has_generic_fields
   );
   tdefoptions=set of tdefoption;
 
@@ -651,7 +654,7 @@ type
     arraydef,recorddef,pointerdef,orddef,
     stringdef,enumdef,procdef,objectdef,errordef,
     filedef,formaldef,setdef,procvardef,floatdef,
-    classrefdef,forwarddef,variantdef,undefineddef
+    classrefdef,forwarddef,variantdef,genericconstdef,undefineddef
   );
 
   { possible types for symtable entries }
@@ -692,7 +695,8 @@ type
   tconsttyp = (constnone,
     constord,conststring,constreal,
     constset,constpointer,constnil,
-    constresourcestring,constwstring,constguid
+    constresourcestring,constwstring,constguid,
+    constundefined
   );
 
   { RTTI information to store }
@@ -831,7 +835,7 @@ inherited_objectoptions : tobjectoptions = [oo_has_virtual,oo_has_private,oo_has
        'abstractdef','arraydef','recorddef','pointerdef','orddef',
        'stringdef','enumdef','procdef','objectdef','errordef',
        'filedef','formaldef','setdef','procvardef','floatdef',
-       'classrefdef','forwarddef','variantdef','undefineddef'
+       'classrefdef','forwarddef','variantdef','genconstdef','undefineddef'
      );
 
      EqualTypeName : array[tequaltype] of string[16] = (
diff --git a/compiler/symdef.pas b/compiler/symdef.pas
index 4a260c46b9..0f7a2e4c06 100644
--- a/compiler/symdef.pas
+++ b/compiler/symdef.pas
@@ -129,6 +129,9 @@ interface
           function is_generic:boolean;inline;
           { same as above for specializations }
           function is_specialization:boolean;inline;
+          { generic utilities }
+          function is_generic_param_const(index:integer):boolean;inline;
+          function get_generic_param_def(index:integer):tdef;inline;
           { registers this def in the unit's deflist; no-op if already registered }
           procedure register_def; override;
           { add the def to the top of the symtable stack if it's not yet owned
@@ -2197,13 +2200,26 @@ implementation
          for i:=0 to genericparas.count-1 do
            begin
              sym:=tsym(genericparas[i]);
-             if sym.typ<>symconst.typesym then
+             { sym must be either a type or const }
+             if not (sym.typ in [symconst.typesym,symconst.constsym]) then
                internalerror(2014050903);
              if sym.owner.defowner<>self then
                exit(false);
            end;
      end;
 
+   function tstoreddef.is_generic_param_const(index:integer):boolean;
+     begin
+       result := tsym(genericparas[index]).typ = constsym;
+     end;  
+
+   function tstoreddef.get_generic_param_def(index:integer):tdef;
+     begin
+       if tsym(genericparas[index]).typ = constsym then
+         result := tconstsym(genericparas[index]).constdef
+       else
+         result := ttypesym(genericparas[index]).typedef;
+     end;
 
    function tstoreddef.is_specialization: boolean;
      var
@@ -2220,12 +2236,12 @@ implementation
            for i:=0 to genericparas.count-1 do
              begin
                sym:=tsym(genericparas[i]);
-               if sym.typ<>symconst.typesym then
+               { sym must be either a type or const }
+               if not (sym.typ in [symconst.typesym,symconst.constsym]) then
                  internalerror(2014050904);
                if sym.owner.defowner<>self then
                  exit(true);
              end;
-           result:=false;
          end;
      end;
 
diff --git a/compiler/symsym.pas b/compiler/symsym.pas
index b21a5f9de9..04c07a5ec7 100644
--- a/compiler/symsym.pas
+++ b/compiler/symsym.pas
@@ -157,7 +157,7 @@ interface
           fprettyname : ansistring;
           constructor create(const n : string;def:tdef;doregister:boolean);virtual;
           destructor destroy;override;
-          constructor ppuload(ppufile:tcompilerppufile);
+          constructor ppuload(ppufile:tcompilerppufile);virtual;
           { do not override this routine in platform-specific subclasses,
             override ppuwrite_platform instead }
           procedure ppuwrite(ppufile:tcompilerppufile);override;final;
@@ -392,6 +392,7 @@ interface
           constructor create_ptr(const n : string;t : tconsttyp;v : pointer;def:tdef);virtual;
           constructor create_string(const n : string;t : tconsttyp;str:pchar;l:longint;def:tdef);virtual;
           constructor create_wstring(const n : string;t : tconsttyp;pw:pcompilerwidestring);virtual;
+          constructor create_undefined(const n : string;def: tdef);
           constructor ppuload(ppufile:tcompilerppufile);
           destructor  destroy;override;
           procedure buildderef;override;
@@ -1581,7 +1582,6 @@ implementation
           tparasymtable(parast).ppuwrite(ppufile);
       end;
 
-
 {****************************************************************************
                             TABSTRACTVARSYM
 ****************************************************************************}
@@ -2344,6 +2344,13 @@ implementation
          value.len:=getlengthwidestring(pw);
       end;
 
+    constructor tconstsym.create_undefined(const n : string;def: tdef);
+      begin
+        inherited create(constsym,n,true);
+        fillchar(value, sizeof(value), #0);
+        consttyp:=constundefined;
+        constdef:=def;
+      end;
 
     constructor tconstsym.ppuload(ppufile:tcompilerppufile);
       var
@@ -2416,7 +2423,8 @@ implementation
                new(pguid(value.valueptr));
                ppufile.getdata(value.valueptr^,sizeof(tguid));
              end;
-           constnil :
+           constnil,
+           constundefined :
              ppufile.getderef(constdefderef);
            else
              Message1(unit_f_ppu_invalid_entry,tostr(ord(consttyp)));
@@ -2448,7 +2456,7 @@ implementation
       begin
         inherited;
         case consttyp  of
-          constnil,constord,constreal,constpointer,constset,conststring,constresourcestring,constguid:
+          constnil,constord,constreal,constpointer,constset,conststring,constresourcestring,constguid,constundefined:
             constdefderef.build(constdef);
           constwstring:
             ;
@@ -2461,7 +2469,7 @@ implementation
     procedure tconstsym.deref;
       begin
         case consttyp of
-          constnil,constord,constreal,constpointer,constset,conststring,constresourcestring,constguid:
+          constnil,constord,constreal,constpointer,constset,conststring,constresourcestring,constguid,constundefined:
             constdef:=tdef(constdefderef.resolve);
           constwstring:
             constdef:=carraydef.getreusable(cwidechartype,getlengthwidestring(pcompilerwidestring(value.valueptr)));
@@ -2476,7 +2484,8 @@ implementation
          inherited ppuwrite(ppufile);
          ppufile.putbyte(byte(consttyp));
          case consttyp of
-           constnil :
+           constnil,
+           constundefined :
              ppufile.putderef(constdefderef);
            constord :
              begin
@@ -2627,7 +2636,6 @@ implementation
           result:=inherited prettyname;
       end;
 
-
 {****************************************************************************
                                   TSYSSYM
 ****************************************************************************}
diff --git a/compiler/symtable.pas b/compiler/symtable.pas
index 796b2d6736..ae82024b03 100644
--- a/compiler/symtable.pas
+++ b/compiler/symtable.pas
@@ -2781,7 +2781,7 @@ implementation
 
     function generate_objectpascal_helper_key(def:tdef):string;
       begin
-        if not assigned(def) then
+        if not assigned(def) or (def.typ = errordef) then
           internalerror(2013020501);
         if def.typ in [recorddef,objectdef] then
           result:=make_mangledname('',tabstractrecorddef(def).symtable,'')
diff --git a/tests/test/tgenconst1.pp b/tests/test/tgenconst1.pp
new file mode 100644
index 0000000000..297b982b0f
--- /dev/null
+++ b/tests/test/tgenconst1.pp
@@ -0,0 +1,33 @@
+{$mode objfpc}
+program tgenconst1;
+
+type
+	kNames = set of (Blaise,Pascal);
+	kChars = set of char;
+type
+	generic TBoolean<const U: boolean> = record end;
+	generic TString<const U: string> = record end;
+	generic TFloat<const U: single> = record end;
+	generic TInteger<const U: integer> = record end;
+	generic TChar<const U: char> = record end;
+	generic TByte<const U: byte> = record end;
+	generic TQWord<const U: QWord> = record end;
+	generic TUndefined<const U> = record end;
+	generic TNames<const U: kNames> = record end;
+	generic TChars<const U: kChars> = record end;
+	generic TPointer<const U: pointer> = record end;
+
+var
+	a: specialize TBoolean<true>;
+	b: specialize TString<'string'>;
+	c: specialize TFloat<1>;
+	d: specialize TInteger<10>;
+	e: specialize TByte<255>;
+	f: specialize TChar<'a'>;
+	g: specialize TUndefined<nil>;
+	h: specialize TNames<[Blaise,Pascal]>;
+	i: specialize TChars<['a','b']>;
+	j: specialize TQWord<10>;
+	k: specialize TPointer<nil>;
+begin
+end.
diff --git a/tests/test/tgenconst10.pp b/tests/test/tgenconst10.pp
new file mode 100644
index 0000000000..f05a27718c
--- /dev/null
+++ b/tests/test/tgenconst10.pp
@@ -0,0 +1,13 @@
+{%FAIL}
+
+{$mode objfpc}
+
+program tgenconst10;
+
+type
+	generic TByte<T> = record end;
+	
+var
+	a: specialize TByte<10>;
+begin
+end.
diff --git a/tests/test/tgenconst11.pp b/tests/test/tgenconst11.pp
new file mode 100644
index 0000000000..ea409bec9b
--- /dev/null
+++ b/tests/test/tgenconst11.pp
@@ -0,0 +1,21 @@
+{%FAIL}
+{$mode objfpc}
+program tgenconst11;
+type
+	TEnum = (aaa,bbb,ccc,ddd);
+type
+	generic TConst<const U> = class end;
+
+var
+	a:specialize TConst<10>;
+	b:specialize TConst<10.5>;
+	c:specialize TConst<'string'>;
+	d:specialize TConst<[1,2,3]>;
+	e:specialize TConst<[aaa,bbb,ccc]>;
+begin
+	a:=specialize TConst<20>.Create;
+	b:=specialize TConst<10.1>.Create;
+	c:=specialize TConst<'_string'>.Create;
+	d:=specialize TConst<[1,2,3,4]>.Create;
+	e:=specialize TConst<[aaa,bbb,ccc,ddd]>.Create;
+end.
\ No newline at end of file
diff --git a/tests/test/tgenconst12.pp b/tests/test/tgenconst12.pp
new file mode 100644
index 0000000000..8f591f6867
--- /dev/null
+++ b/tests/test/tgenconst12.pp
@@ -0,0 +1,16 @@
+{$mode objfpc}
+program tgenconst12;
+
+type
+  generic TTest<const U> = class
+  		class procedure DoThis;
+  end;
+
+class procedure TTest.DoThis;
+begin
+end;
+
+type
+	ATest = specialize TTest<100>;
+begin 
+end.
diff --git a/tests/test/tgenconst13.pp b/tests/test/tgenconst13.pp
new file mode 100644
index 0000000000..0d5f8b1813
--- /dev/null
+++ b/tests/test/tgenconst13.pp
@@ -0,0 +1,20 @@
+{$mode objfpc}
+program tgenconst13;
+type
+	TEnum = (aaa,bbb,ccc);
+type
+	generic TConst<const U> = class end;
+
+var
+	a:specialize TConst<10>;
+	b:specialize TConst<10.5>;
+	c:specialize TConst<'string'>;
+	d:specialize TConst<[1,2,3]>;
+	e:specialize TConst<[aaa,bbb,ccc]>;
+begin
+	a:=specialize TConst<10>.Create;
+	b:=specialize TConst<10.5>.Create;
+	c:=specialize TConst<'string'>.Create;
+	d:=specialize TConst<[1,2,3]>.Create;
+	e:=specialize TConst<[aaa,bbb,ccc]>.Create;
+end.
diff --git a/tests/test/tgenconst2.pp b/tests/test/tgenconst2.pp
new file mode 100644
index 0000000000..aa3a960634
--- /dev/null
+++ b/tests/test/tgenconst2.pp
@@ -0,0 +1,12 @@
+{$mode objfpc}
+program tgenconst2;
+
+type
+	generic TStuff1<T1,T2;const U1,U2> = record end;
+	generic TStuff2<T1,T2;const U1,U2:integer> = record end;
+	
+var
+	a: specialize TStuff1<integer,string,10,'string'>;
+	b: specialize TStuff2<integer,string,10,10>;
+begin
+end.
diff --git a/tests/test/tgenconst3.pp b/tests/test/tgenconst3.pp
new file mode 100644
index 0000000000..aea0e307e2
--- /dev/null
+++ b/tests/test/tgenconst3.pp
@@ -0,0 +1,16 @@
+{$mode objfpc}
+{$modeswitch advancedrecords}
+program tgenconst3;
+
+type
+	generic TList<T;const U:integer> = record
+		const
+			max = U;
+		public
+			m_list: array[0..max-1] of T;
+	end;
+
+var
+	list: specialize TList<integer,128>;
+begin
+end.
diff --git a/tests/test/tgenconst4.pp b/tests/test/tgenconst4.pp
new file mode 100644
index 0000000000..a1fae00c43
--- /dev/null
+++ b/tests/test/tgenconst4.pp
@@ -0,0 +1,11 @@
+{$mode objfpc}
+program tgenconst4;
+
+generic procedure DoThis<T;const U:string>(msg:string = U);
+begin
+	writeln(msg, ' sizeof:',sizeof(t), ' default: ', U);
+end;
+
+begin
+	specialize DoThis<integer,'genparam'>('hello world');
+end.
diff --git a/tests/test/tgenconst5.pp b/tests/test/tgenconst5.pp
new file mode 100644
index 0000000000..63514a976c
--- /dev/null
+++ b/tests/test/tgenconst5.pp
@@ -0,0 +1,24 @@
+{$mode objfpc}
+program tgenconst5;
+
+type
+	generic THelperA<const U:integer> = record
+		list: array[0..U-1] of byte;
+	end;
+
+type
+	generic THelperB<T> = record
+		value: T;
+	end;
+
+type
+	generic TList<T; const U:integer> = record
+		helperA: specialize THelperA<U>;
+		helperB: specialize THelperB<T>;
+	end;
+
+var
+	list: specialize TList<integer,32>;
+begin
+	writeln('sizeof:',sizeof(list));
+end.
diff --git a/tests/test/tgenconst6.pp b/tests/test/tgenconst6.pp
new file mode 100644
index 0000000000..3ee3785423
--- /dev/null
+++ b/tests/test/tgenconst6.pp
@@ -0,0 +1,21 @@
+{$mode delphi}
+program tgenconst6;
+
+type
+	TList<T;const U> = class
+		list: array[0..U-1] of T;
+		function capacity: integer;
+	end;
+
+function TList<T,U>.capacity: integer;
+begin
+	result := U;	
+end;	
+
+var
+	nums:TList<integer,16>;
+	strs:TList<string,16>;
+begin
+	nums := TList<integer,16>.Create;
+	strs := TList<string,16>.Create;
+end.
diff --git a/tests/test/tgenconst7.pp b/tests/test/tgenconst7.pp
new file mode 100644
index 0000000000..9d8e81ef05
--- /dev/null
+++ b/tests/test/tgenconst7.pp
@@ -0,0 +1,11 @@
+{%FAIL}
+{$mode objfpc}
+program tgenconst7;
+
+type
+	generic TInteger<const U: integer> = record end;
+
+var
+	a: specialize TInteger<'string'>;
+begin
+end.
diff --git a/tests/test/tgenconst8.pp b/tests/test/tgenconst8.pp
new file mode 100644
index 0000000000..75844f7181
--- /dev/null
+++ b/tests/test/tgenconst8.pp
@@ -0,0 +1,11 @@
+{%FAIL}
+{$mode objfpc}
+program tgenconst8;
+
+type
+	generic TByte<const U: Byte> = record end;
+	
+var
+	a: specialize TByte<300>;
+begin
+end.
diff --git a/tests/test/tgenconst9.pp b/tests/test/tgenconst9.pp
new file mode 100644
index 0000000000..939cb90302
--- /dev/null
+++ b/tests/test/tgenconst9.pp
@@ -0,0 +1,11 @@
+{%FAIL}
+{$mode objfpc}
+program tgenconst9;
+
+type
+	generic TByte<const U: Byte> = record end;
+	
+var
+	a: specialize TByte<string>;
+begin
+end.

From e298c138a26964a9e960f868c8f821564ac52e55 Mon Sep 17 00:00:00 2001
From: Ryan Joseph <genericptr@gmail.com>
Date: Tue, 6 Nov 2018 13:58:49 +0700
Subject: [PATCH] constants in generics

---
 compiler/defcmp.pas       |   9 +-
 compiler/htypechk.pas     |   2 +-
 compiler/ncon.pas         |  10 +
 compiler/node.pas         |  16 +-
 compiler/nset.pas         |   5 +-
 compiler/pdecl.pas        |  32 ++-
 compiler/pexpr.pas        |  11 +-
 compiler/pgentype.pas     |   8 +-
 compiler/pgenutil.pas     | 540 ++++++++++++++++++++++++--------------
 compiler/ptype.pas        |   4 +-
 compiler/symconst.pas     |  12 +-
 compiler/symdef.pas       |  19 +-
 compiler/symsym.pas       |  22 +-
 compiler/symtable.pas     |   2 +-
 tests/test/tgenconst1.pp  |  33 +++
 tests/test/tgenconst10.pp |  13 +
 tests/test/tgenconst11.pp |  21 ++
 tests/test/tgenconst12.pp |  16 ++
 tests/test/tgenconst13.pp |  20 ++
 tests/test/tgenconst2.pp  |  12 +
 tests/test/tgenconst3.pp  |  16 ++
 tests/test/tgenconst4.pp  |  11 +
 tests/test/tgenconst5.pp  |  24 ++
 tests/test/tgenconst6.pp  |  21 ++
 tests/test/tgenconst7.pp  |  11 +
 tests/test/tgenconst8.pp  |  11 +
 tests/test/tgenconst9.pp  |  11 +
 27 files changed, 667 insertions(+), 245 deletions(-)
 create mode 100644 tests/test/tgenconst1.pp
 create mode 100644 tests/test/tgenconst10.pp
 create mode 100644 tests/test/tgenconst11.pp
 create mode 100644 tests/test/tgenconst12.pp
 create mode 100644 tests/test/tgenconst13.pp
 create mode 100644 tests/test/tgenconst2.pp
 create mode 100644 tests/test/tgenconst3.pp
 create mode 100644 tests/test/tgenconst4.pp
 create mode 100644 tests/test/tgenconst5.pp
 create mode 100644 tests/test/tgenconst6.pp
 create mode 100644 tests/test/tgenconst7.pp
 create mode 100644 tests/test/tgenconst8.pp
 create mode 100644 tests/test/tgenconst9.pp

diff --git a/compiler/defcmp.pas b/compiler/defcmp.pas
index 9fc5b29119..87797faf3e 100644
--- a/compiler/defcmp.pas
+++ b/compiler/defcmp.pas
@@ -175,7 +175,6 @@ implementation
       symtable,symsym,symcpu,
       defutil,symutil;
 
-
     function compare_defs_ext(def_from,def_to : tdef;
                               fromtreetype : tnodetype;
                               var doconv : tconverttype;
@@ -345,9 +344,13 @@ implementation
                        internalerror(2012091302);
                      symfrom:=ttypesym(tstoreddef(def_from).genericparas[i]);
                      symto:=ttypesym(tstoreddef(def_to).genericparas[i]);
-                     if not (symfrom.typ=typesym) or not (symto.typ=typesym) then
+                     if not (symfrom.typ in [typesym,constsym]) or not (symto.typ in [typesym,constsym]) then
                        internalerror(2012121401);
-                     if not equal_defs(ttypesym(symfrom).typedef,ttypesym(symto).typedef) then
+                     if symto.typ <> symfrom.typ then
+                       diff:=true
+                     else if (symfrom.typ=constsym) and (symto.typ=constsym) and not equal_constsym(tconstsym(symfrom),tconstsym(symto),true) then
+                       diff:=true
+                     else if not equal_defs(ttypesym(symfrom).typedef,ttypesym(symto).typedef) then
                        diff:=true;
                      if diff then
                        break;
diff --git a/compiler/htypechk.pas b/compiler/htypechk.pas
index 4e97f903a9..89d32fa966 100644
--- a/compiler/htypechk.pas
+++ b/compiler/htypechk.pas
@@ -2705,7 +2705,7 @@ implementation
               internalerror(2015060301);
             { check whether the given parameters are compatible
               to the def's constraints }
-            if not check_generic_constraints(pd,spezcontext.genericdeflist,spezcontext.poslist) then
+            if not check_generic_constraints(pd,spezcontext.paramlist,spezcontext.poslist) then
               exit;
             def:=generate_specialization_phase2(spezcontext,pd,false,'');
             case def.typ of
diff --git a/compiler/ncon.pas b/compiler/ncon.pas
index 392e11ea1d..90087c265f 100644
--- a/compiler/ncon.pas
+++ b/compiler/ncon.pas
@@ -311,11 +311,21 @@ implementation
             p1:=cpointerconstnode.create(p.value.valueordptr,p.constdef);
           constnil :
             p1:=cnilnode.create;
+          { constundefined is a placeholder for unrestricted generic const params
+            so we just treat it as a nil node. }
+          constundefined :
+            begin
+              p1:=cnilnode.create;
+              p1.resultdef := p.constdef;
+            end;
           constguid :
             p1:=cguidconstnode.create(pguid(p.value.valueptr)^);
           else
             internalerror(200205103);
         end;
+        { transfer generic param flag from symbol to node }
+        if sp_generic_para in p.symoptions then
+          include(p1.flags,nf_generic_para);
         genconstsymtree:=p1;
       end;
 
diff --git a/compiler/node.pas b/compiler/node.pas
index a0aad228eb..468907a886 100644
--- a/compiler/node.pas
+++ b/compiler/node.pas
@@ -274,10 +274,13 @@ interface
          nf_block_with_exit,
 
          { tloadvmtaddrnode }
-         nf_ignore_for_wpo  { we know that this loadvmtaddrnode cannot be used to construct a class instance }
+         nf_ignore_for_wpo,  { we know that this loadvmtaddrnode cannot be used to construct a class instance }
 
-         { WARNING: there are now 31 elements in this type, and a set of this
-             type is written to the PPU. So before adding more than 32 elements,
+         { node is derived from generic parameter }
+         nf_generic_para
+
+         { WARNING: there are now 32 elements in this type, and a set of this
+             type is written to the PPU. So before adding more elements,
              either move some flags to specific nodes, or stream a normalset
              to the ppu
          }
@@ -1080,7 +1083,12 @@ implementation
     constructor tbinarynode.create(t:tnodetype;l,r : tnode);
       begin
          inherited create(t,l);
-         right:=r
+         { transfer generic paramater flag }
+         if assigned(l) and (nf_generic_para in l.flags) then
+           include(flags,nf_generic_para)
+         else if assigned(r) and (nf_generic_para in r.flags) then
+           include(flags,nf_generic_para);
+         right:=r;
       end;
 
 
diff --git a/compiler/nset.pas b/compiler/nset.pas
index 684eafd79a..e6e1d51a16 100644
--- a/compiler/nset.pas
+++ b/compiler/nset.pas
@@ -401,8 +401,9 @@ implementation
          { both types must be compatible }
          if compare_defs(left.resultdef,right.resultdef,left.nodetype)=te_incompatible then
            IncompatibleTypes(left.resultdef,right.resultdef);
-         { Check if only when its a constant set }
-         if (left.nodetype=ordconstn) and (right.nodetype=ordconstn) then
+         { check if only when its a constant set and
+           ignore range nodes which are generic parameter derived }
+         if not (nf_generic_para in flags) and (left.nodetype=ordconstn) and (right.nodetype=ordconstn) then
           begin
             { upper limit must be greater or equal than lower limit }
             if (tordconstnode(left).value>tordconstnode(right).value) and
diff --git a/compiler/pdecl.pas b/compiler/pdecl.pas
index fcb19c2c3d..82c0160805 100644
--- a/compiler/pdecl.pas
+++ b/compiler/pdecl.pas
@@ -141,18 +141,18 @@ implementation
            typen :
              begin
                if is_interface(p.resultdef) then
-                begin
-                  if assigned(tobjectdef(p.resultdef).iidguid) then
-                   begin
-                     new(pg);
-                     pg^:=tobjectdef(p.resultdef).iidguid^;
-                     hp:=cconstsym.create_ptr(orgname,constguid,pg,p.resultdef);
-                   end
-                  else
-                   Message1(parser_e_interface_has_no_guid,tobjectdef(p.resultdef).objrealname^);
-                end
-               else
-                Message(parser_e_illegal_expression);
+                 begin
+                   if assigned(tobjectdef(p.resultdef).iidguid) then
+                     begin
+                       new(pg);
+                       pg^:=tobjectdef(p.resultdef).iidguid^;
+                       hp:=cconstsym.create_ptr(orgname,constguid,pg,p.resultdef);
+                     end
+                    else
+                      Message1(parser_e_interface_has_no_guid,tobjectdef(p.resultdef).objrealname^);
+                 end
+               else 
+                 Message(parser_e_illegal_expression);
              end;
            inlinen:
              begin
@@ -179,6 +179,9 @@ implementation
            else
              Message(parser_e_illegal_expression);
         end;
+        { transfer generic param flag from node to symbol }
+        if nf_generic_para in p.flags then
+          include(hp.symoptions,sp_generic_para);
         current_tokenpos:=storetokenpos;
         p.free;
         readconstant:=hp;
@@ -510,8 +513,9 @@ implementation
                { we are not freeing the type parameters, so register them }
                for i:=0 to generictypelist.count-1 do
                  begin
-                    ttypesym(generictypelist[i]).register_sym;
-                    tstoreddef(ttypesym(generictypelist[i]).typedef).register_def;
+                    tstoredsym(generictypelist[i]).register_sym;
+                    if tstoredsym(generictypelist[i]).typ=typesym then
+                      tstoreddef(ttypesym(generictypelist[i]).typedef).register_def;
                  end;
 
                str(generictypelist.Count,s);
diff --git a/compiler/pexpr.pas b/compiler/pexpr.pas
index 251c613ef1..caf1ef2774 100644
--- a/compiler/pexpr.pas
+++ b/compiler/pexpr.pas
@@ -446,6 +446,9 @@ implementation
                   { no packed bit support for these things }
                   if l=in_bitsizeof_x then
                     statement_syssym:=caddnode.create(muln,statement_syssym,cordconstnode.create(8,sinttype,true));
+                  { type sym is a generic parameter }
+                  if assigned(p1.resultdef.typesym) and (sp_generic_para in p1.resultdef.typesym.symoptions) then
+                    include(statement_syssym.flags,nf_generic_para);
                 end
               else
                begin
@@ -466,6 +469,9 @@ implementation
                    end
                  else
                    statement_syssym:=cordconstnode.create(p1.resultdef.packedbitsize,sinttype,true);
+                 { type def is a struct with generic fields }
+                 if df_has_generic_fields in p1.resultdef.defoptions then
+                    include(statement_syssym.flags,nf_generic_para);
                  { p1 not needed !}
                  p1.destroy;
                end;
@@ -4167,7 +4173,10 @@ implementation
                 gendef:=generate_specialization_phase2(spezcontext,tstoreddef(gendef),false,'');
                 spezcontext.free;
                 spezcontext:=nil;
-                gensym:=gendef.typesym;
+                if gendef.typ=errordef then
+                  gensym:=generrorsym
+                else
+                  gensym:=gendef.typesym;
               end;
             procdef:
               begin
diff --git a/compiler/pgentype.pas b/compiler/pgentype.pas
index b2847c78f6..85270df256 100644
--- a/compiler/pgentype.pas
+++ b/compiler/pgentype.pas
@@ -28,7 +28,7 @@ interface
 uses
   cclasses,
   globtype,
-  symtype,symbase;
+  symconst,symtype,symbase;
 
 const
   inline_specialization_block_types = [bt_type,bt_var_type,bt_const_type,bt_body];
@@ -42,7 +42,7 @@ type
 
   tspecializationcontext=class
   public
-    genericdeflist : tfpobjectlist;
+    paramlist : tfpobjectlist;
     poslist : tfplist;
     prettyname : ansistring;
     specializename : ansistring;
@@ -58,7 +58,7 @@ implementation
 
 constructor tspecializationcontext.create;
 begin
-  genericdeflist:=tfpobjectlist.create(false);
+  paramlist:=tfpobjectlist.create(false);
   poslist:=tfplist.create;
 end;
 
@@ -66,7 +66,7 @@ destructor tspecializationcontext.destroy;
 var
   i : longint;
 begin
-  genericdeflist.free;
+  paramlist.free;
   for i:=0 to poslist.count-1 do
     dispose(pfileposinfo(poslist[i]));
   poslist.free;
diff --git a/compiler/pgenutil.pas b/compiler/pgenutil.pas
index 4e52761d73..4c634904a6 100644
--- a/compiler/pgenutil.pas
+++ b/compiler/pgenutil.pas
@@ -42,9 +42,9 @@ uses
     function generate_specialization_phase1(out context:tspecializationcontext;genericdef:tdef;symname:string):tdef;inline;
     function generate_specialization_phase1(out context:tspecializationcontext;genericdef:tdef;parsedtype:tdef;symname:string;parsedpos:tfileposinfo):tdef;
     function generate_specialization_phase2(context:tspecializationcontext;genericdef:tstoreddef;parse_class_parent:boolean;_prettyname:ansistring):tdef;
-    function check_generic_constraints(genericdef:tstoreddef;paradeflist:tfpobjectlist;poslist:tfplist):boolean;
+    function check_generic_constraints(genericdef:tstoreddef;paramlist:tfpobjectlist;poslist:tfplist):boolean;
     function parse_generic_parameters(allowconstraints:boolean):tfphashobjectlist;
-    function parse_generic_specialization_types(genericdeflist:tfpobjectlist;poslist:tfplist;out prettyname,specializename:ansistring):boolean;
+    function parse_generic_specialization_types(paramlist:tfpobjectlist;poslist:tfplist;out prettyname,specializename:ansistring):boolean;
     procedure insert_generic_parameter_types(def:tstoreddef;genericdef:tstoreddef;genericlist:tfphashobjectlist);
     procedure maybe_insert_generic_rename_symbol(const name:tidstring;genericlist:tfphashobjectlist);
     function generate_generic_name(const name:tidstring;specializename:ansistring;owner_hierarchy:string):tidstring;
@@ -104,203 +104,232 @@ uses
           end;
       end;
 
-    function check_generic_constraints(genericdef:tstoreddef;paradeflist:tfpobjectlist;poslist:tfplist):boolean;
+    function check_generic_constraints(genericdef:tstoreddef;paramlist:tfpobjectlist;poslist:tfplist):boolean;
       var
         i,j,
         intfcount : longint;
         formaldef,
         paradef : tstoreddef;
+        genparadef : tdef;
         objdef,
         paraobjdef,
         formalobjdef : tobjectdef;
         intffound : boolean;
         filepos : tfileposinfo;
+        //paratype : tconsttyp;
+        is_const : boolean;
       begin
         { check whether the given specialization parameters fit to the eventual
           constraints of the generic }
         if not assigned(genericdef.genericparas) or (genericdef.genericparas.count=0) then
           internalerror(2012101001);
-        if genericdef.genericparas.count<>paradeflist.count then
+        if genericdef.genericparas.count<>paramlist.count then
           internalerror(2012101002);
-        if paradeflist.count<>poslist.count then
+        if paramlist.count<>poslist.count then
           internalerror(2012120801);
         result:=true;
         for i:=0 to genericdef.genericparas.count-1 do
           begin
             filepos:=pfileposinfo(poslist[i])^;
-            formaldef:=tstoreddef(ttypesym(genericdef.genericparas[i]).typedef);
-            if formaldef.typ=undefineddef then
-              { the parameter is of unspecified type, so no need to check }
-              continue;
-            if not (df_genconstraint in formaldef.defoptions) or
-                not assigned(formaldef.genconstraintdata) then
-              internalerror(2013021602);
-            paradef:=tstoreddef(paradeflist[i]);
-            { undefineddef is compatible with anything }
-            if formaldef.typ=undefineddef then
-              continue;
-            if paradef.typ<>formaldef.typ then
+            paradef:=tstoreddef(get_generic_param_def(tsym(paramlist[i])));
+            is_const:=is_generic_param_const(tsym(paramlist[i]));
+            genparadef:=genericdef.get_generic_param_def(i);
+            { validate const params }
+            if not genericdef.is_generic_param_const(i) and is_const then
               begin
-                case formaldef.typ of
-                  recorddef:
-                    { delphi has own fantasy about record constraint
-                      (almost non-nullable/non-nilable value type) }
-                    if m_delphi in current_settings.modeswitches then
-                      case paradef.typ of
-                        floatdef,enumdef,orddef:
-                          continue;
-                        objectdef:
-                          if tobjectdef(paradef).objecttype=odt_object then
-                            continue
-                          else
-                            MessagePos(filepos,type_e_record_type_expected);
+                MessagePos(filepos,type_e_mismatch);
+                exit(false);
+              end
+            else if genericdef.is_generic_param_const(i) then
+              begin
+                { param type mismatch (type <> const) }
+                 if genericdef.is_generic_param_const(i) <> is_const then
+                   begin
+                    MessagePos(filepos,type_e_mismatch);
+                    exit(false);
+                  end;
+                { type constrained param doesn't match type }
+                if not compare_generic_params(paradef,genericdef.get_generic_param_def(i),tconstsym(paramlist[i])) then
+                  begin
+                    MessagePos2(filepos,type_e_incompatible_types,FullTypeName(paradef,genparadef),FullTypeName(genparadef,paradef));
+                    exit(false);
+                  end;
+              end;
+            { test constraints for non-const params }
+            if not genericdef.is_generic_param_const(i) then
+              begin
+                formaldef:=tstoreddef(ttypesym(genericdef.genericparas[i]).typedef);
+                if formaldef.typ=undefineddef then
+                  { the parameter is of unspecified type, so no need to check }
+                  continue;
+                if not (df_genconstraint in formaldef.defoptions) or
+                    not assigned(formaldef.genconstraintdata) then
+                  internalerror(2013021602);
+                { undefineddef is compatible with anything }
+                if formaldef.typ=undefineddef then
+                  continue;
+                if paradef.typ<>formaldef.typ then
+                  begin
+                    case formaldef.typ of
+                      recorddef:
+                        { delphi has own fantasy about record constraint
+                          (almost non-nullable/non-nilable value type) }
+                        if m_delphi in current_settings.modeswitches then
+                          case paradef.typ of
+                            floatdef,enumdef,orddef:
+                              continue;
+                            objectdef:
+                              if tobjectdef(paradef).objecttype=odt_object then
+                                continue
+                              else
+                                MessagePos(filepos,type_e_record_type_expected);
+                            else
+                              MessagePos(filepos,type_e_record_type_expected);
+                          end
                         else
                           MessagePos(filepos,type_e_record_type_expected);
-                      end
-                    else
-                      MessagePos(filepos,type_e_record_type_expected);
-                  objectdef:
-                    case tobjectdef(formaldef).objecttype of
-                      odt_class,
-                      odt_javaclass:
-                        MessagePos1(filepos,type_e_class_type_expected,paradef.typename);
-                      odt_interfacecom,
-                      odt_interfacecorba,
-                      odt_dispinterface,
-                      odt_interfacejava:
-                        MessagePos1(filepos,type_e_interface_type_expected,paradef.typename);
+                      objectdef:
+                        case tobjectdef(formaldef).objecttype of
+                          odt_class,
+                          odt_javaclass:
+                            MessagePos1(filepos,type_e_class_type_expected,paradef.typename);
+                          odt_interfacecom,
+                          odt_interfacecorba,
+                          odt_dispinterface,
+                          odt_interfacejava:
+                            MessagePos1(filepos,type_e_interface_type_expected,paradef.typename);
+                          else
+                            internalerror(2012101003);
+                        end;
+                      errordef:
+                        { ignore }
+                        ;
                       else
-                        internalerror(2012101003);
+                        internalerror(2012101004);
                     end;
-                  errordef:
-                    { ignore }
-                    ;
-                  else
-                    internalerror(2012101004);
-                end;
-                result:=false;
-              end
-            else
-              begin
-                { the paradef types are the same, so do special checks for the
-                  cases in which they are needed }
-                if formaldef.typ=objectdef then
+                    result:=false;
+                  end
+                else
                   begin
-                    paraobjdef:=tobjectdef(paradef);
-                    formalobjdef:=tobjectdef(formaldef);
-                    if not (formalobjdef.objecttype in [odt_class,odt_javaclass,odt_interfacecom,odt_interfacecorba,odt_interfacejava,odt_dispinterface]) then
-                      internalerror(2012101102);
-                    if formalobjdef.objecttype in [odt_interfacecom,odt_interfacecorba,odt_interfacejava,odt_dispinterface] then
+                    { the paradef types are the same, so do special checks for the
+                      cases in which they are needed }
+                    if formaldef.typ=objectdef then
                       begin
-                        { this is either a concerete interface or class type (the
-                          latter without specific implemented interfaces) }
-                        case paraobjdef.objecttype of
-                          odt_interfacecom,
-                          odt_interfacecorba,
-                          odt_interfacejava,
-                          odt_dispinterface:
-                            begin
-                              if (oo_is_forward in paraobjdef.objectoptions) and
-                                  (paraobjdef.objecttype=formalobjdef.objecttype) and
-                                  (df_genconstraint in formalobjdef.defoptions) and
-                                  (
-                                    (formalobjdef.objecttype=odt_interfacecom) and
-                                    (formalobjdef.childof=interface_iunknown)
-                                  )
-                                  or
-                                  (
-                                    (formalobjdef.objecttype=odt_interfacecorba) and
-                                    (formalobjdef.childof=nil)
-                                  ) then
-                                continue;
-                              if not def_is_related(paraobjdef,formalobjdef.childof) then
+                        paraobjdef:=tobjectdef(paradef);
+                        formalobjdef:=tobjectdef(formaldef);
+                        if not (formalobjdef.objecttype in [odt_class,odt_javaclass,odt_interfacecom,odt_interfacecorba,odt_interfacejava,odt_dispinterface]) then
+                          internalerror(2012101102);
+                        if formalobjdef.objecttype in [odt_interfacecom,odt_interfacecorba,odt_interfacejava,odt_dispinterface] then
+                          begin
+                            { this is either a concerete interface or class type (the
+                              latter without specific implemented interfaces) }
+                            case paraobjdef.objecttype of
+                              odt_interfacecom,
+                              odt_interfacecorba,
+                              odt_interfacejava,
+                              odt_dispinterface:
                                 begin
-                                  MessagePos2(filepos,type_e_incompatible_types,paraobjdef.typename,formalobjdef.childof.typename);
-                                  result:=false;
+                                  if (oo_is_forward in paraobjdef.objectoptions) and
+                                      (paraobjdef.objecttype=formalobjdef.objecttype) and
+                                      (df_genconstraint in formalobjdef.defoptions) and
+                                      (
+                                        (formalobjdef.objecttype=odt_interfacecom) and
+                                        (formalobjdef.childof=interface_iunknown)
+                                      )
+                                      or
+                                      (
+                                        (formalobjdef.objecttype=odt_interfacecorba) and
+                                        (formalobjdef.childof=nil)
+                                      ) then
+                                    continue;
+                                  if not def_is_related(paraobjdef,formalobjdef.childof) then
+                                    begin
+                                      MessagePos2(filepos,type_e_incompatible_types,paraobjdef.typename,formalobjdef.childof.typename);
+                                      result:=false;
+                                    end;
                                 end;
-                            end;
-                          odt_class,
-                          odt_javaclass:
-                            begin
-                              objdef:=paraobjdef;
-                              intffound:=false;
-                              while assigned(objdef) do
+                              odt_class,
+                              odt_javaclass:
                                 begin
-                                  for j:=0 to objdef.implementedinterfaces.count-1 do
-                                    if timplementedinterface(objdef.implementedinterfaces[j]).intfdef=formalobjdef.childof then
-                                      begin
-                                        intffound:=true;
+                                  objdef:=paraobjdef;
+                                  intffound:=false;
+                                  while assigned(objdef) do
+                                    begin
+                                      for j:=0 to objdef.implementedinterfaces.count-1 do
+                                        if timplementedinterface(objdef.implementedinterfaces[j]).intfdef=formalobjdef.childof then
+                                          begin
+                                            intffound:=true;
+                                            break;
+                                          end;
+                                      if intffound then
                                         break;
-                                      end;
-                                  if intffound then
-                                    break;
-                                  objdef:=objdef.childof;
+                                      objdef:=objdef.childof;
+                                    end;
+                                  result:=intffound;
+                                  if not result then
+                                    MessagePos2(filepos,parser_e_class_doesnt_implement_interface,paraobjdef.typename,formalobjdef.childof.typename);
+                                end;
+                              else
+                                begin
+                                  MessagePos1(filepos,type_e_class_or_interface_type_expected,paraobjdef.typename);
+                                  result:=false;
                                 end;
-                              result:=intffound;
-                              if not result then
-                                MessagePos2(filepos,parser_e_class_doesnt_implement_interface,paraobjdef.typename,formalobjdef.childof.typename);
-                            end;
-                          else
-                            begin
-                              MessagePos1(filepos,type_e_class_or_interface_type_expected,paraobjdef.typename);
-                              result:=false;
                             end;
-                        end;
-                      end
-                    else
-                      begin
-                        { this is either a "class" or a concrete instance with
-                          or without implemented interfaces }
-                        if not (paraobjdef.objecttype in [odt_class,odt_javaclass]) then
-                          begin
-                            MessagePos1(filepos,type_e_class_type_expected,paraobjdef.typename);
-                            result:=false;
-                            continue;
-                          end;
-                        { for forward declared classes we allow pure TObject/class declarations }
-                        if (oo_is_forward in paraobjdef.objectoptions) and
-                            (df_genconstraint in formaldef.defoptions) then
-                          begin
-                            if (formalobjdef.childof=class_tobject) and
-                                not formalobjdef.implements_any_interfaces then
-                              continue;
-                          end;
-                        if assigned(formalobjdef.childof) and
-                            not def_is_related(paradef,formalobjdef.childof) then
-                          begin
-                            MessagePos2(filepos,type_e_incompatible_types,paraobjdef.typename,formalobjdef.childof.typename);
-                            result:=false;
-                          end;
-                        intfcount:=0;
-                        for j:=0 to formalobjdef.implementedinterfaces.count-1 do
+                          end
+                        else
                           begin
-                            objdef:=paraobjdef;
-                            while assigned(objdef) do
+                            { this is either a "class" or a concrete instance with
+                              or without implemented interfaces }
+                            if not (paraobjdef.objecttype in [odt_class,odt_javaclass]) then
+                              begin
+                                MessagePos1(filepos,type_e_class_type_expected,paraobjdef.typename);
+                                result:=false;
+                                continue;
+                              end;
+                            { for forward declared classes we allow pure TObject/class declarations }
+                            if (oo_is_forward in paraobjdef.objectoptions) and
+                                (df_genconstraint in formaldef.defoptions) then
                               begin
-                                intffound:=assigned(
-                                             find_implemented_interface(objdef,
-                                               timplementedinterface(formalobjdef.implementedinterfaces[j]).intfdef
-                                             )
-                                           );
+                                if (formalobjdef.childof=class_tobject) and
+                                    not formalobjdef.implements_any_interfaces then
+                                  continue;
+                              end;
+                            if assigned(formalobjdef.childof) and
+                                not def_is_related(paradef,formalobjdef.childof) then
+                              begin
+                                MessagePos2(filepos,type_e_incompatible_types,paraobjdef.typename,formalobjdef.childof.typename);
+                                result:=false;
+                              end;
+                            intfcount:=0;
+                            for j:=0 to formalobjdef.implementedinterfaces.count-1 do
+                              begin
+                                objdef:=paraobjdef;
+                                while assigned(objdef) do
+                                  begin
+                                    intffound:=assigned(
+                                                 find_implemented_interface(objdef,
+                                                   timplementedinterface(formalobjdef.implementedinterfaces[j]).intfdef
+                                                 )
+                                               );
+                                    if intffound then
+                                      break;
+                                    objdef:=objdef.childof;
+                                  end;
                                 if intffound then
-                                  break;
-                                objdef:=objdef.childof;
+                                  inc(intfcount)
+                                else
+                                  MessagePos2(filepos,parser_e_class_doesnt_implement_interface,paraobjdef.typename,timplementedinterface(formalobjdef.implementedinterfaces[j]).intfdef.typename);
                               end;
-                            if intffound then
-                              inc(intfcount)
-                            else
-                              MessagePos2(filepos,parser_e_class_doesnt_implement_interface,paraobjdef.typename,timplementedinterface(formalobjdef.implementedinterfaces[j]).intfdef.typename);
+                            if intfcount<>formalobjdef.implementedinterfaces.count then
+                              result:=false;
                           end;
-                        if intfcount<>formalobjdef.implementedinterfaces.count then
-                          result:=false;
                       end;
                   end;
               end;
           end;
       end;
 
-
-    function parse_generic_specialization_types_internal(genericdeflist:tfpobjectlist;poslist:tfplist;out prettyname,specializename:ansistring;parsedtype:tdef;parsedpos:tfileposinfo):boolean;
+    function parse_generic_specialization_types_internal(paramlist:tfpobjectlist;poslist:tfplist;out prettyname,specializename:ansistring;parsedtype:tdef;parsedpos:tfileposinfo):boolean;
       var
         old_block_type : tblock_type;
         first : boolean;
@@ -310,9 +339,12 @@ uses
         namepart : string;
         prettynamepart : ansistring;
         module : tmodule;
+        //paramdef : tgenericparamdef;
+        constprettyname : string;
+        validparam : boolean;
       begin
         result:=true;
-        if genericdeflist=nil then
+        if paramlist=nil then
           internalerror(2012061401);
         { set the block type to type, so that the parsed type are returned as
           ttypenode (e.g. classes are in non type-compatible blocks returned as
@@ -324,7 +356,7 @@ uses
         first:=not assigned(parsedtype);
         if assigned(parsedtype) then
           begin
-            genericdeflist.Add(parsedtype);
+            paramlist.Add(parsedtype.typesym);
             module:=find_module_from_symtable(parsedtype.owner);
             if not assigned(module) then
               internalerror(2016112801);
@@ -351,7 +383,9 @@ uses
             block_type:=bt_type;
             tmpparampos:=current_filepos;
             typeparam:=factor(false,[ef_type_only]);
-            if typeparam.nodetype=typen then
+            { determine if the typeparam node is a valid type or const }
+            validparam:=typeparam.nodetype in tgeneric_param_nodes;
+            if validparam then
               begin
                 if tstoreddef(typeparam.resultdef).is_generic and
                     (
@@ -367,31 +401,47 @@ uses
                   end;
                 if typeparam.resultdef.typ<>errordef then
                   begin
-                    if not assigned(typeparam.resultdef.typesym) then
+                    if (typeparam.nodetype = typen) and not assigned(typeparam.resultdef.typesym) then
                       message(type_e_generics_cannot_reference_itself)
-                    else if (typeparam.resultdef.typ<>errordef) then
+                    else 
+                    if (typeparam.resultdef.typ<>errordef) then
                       begin
-                        genericdeflist.Add(typeparam.resultdef);
+                        { all non-type nodes are considered const }
+                        if typeparam.nodetype <> typen then
+                          paramlist.Add(create_generic_constsym(typeparam.resultdef,typeparam,constprettyname))
+                        else
+                          begin
+                            constprettyname:='';
+                            paramlist.Add(typeparam.resultdef.typesym);
+                          end;
                         module:=find_module_from_symtable(typeparam.resultdef.owner);
                         if not assigned(module) then
                           internalerror(2016112802);
                         namepart:='_$'+hexstr(module.moduleid,8)+'$$'+typeparam.resultdef.unique_id_str;
+                        if constprettyname <> '' then
+                          namepart:=namepart+'$$'+constprettyname;
                         { we use the full name of the type to uniquely identify it }
-                        if (symtablestack.top.symtabletype=parasymtable) and
-                            (symtablestack.top.defowner.typ=procdef) and
-                            (typeparam.resultdef.owner=symtablestack.top) then
+                        if typeparam.nodetype = typen then
                           begin
-                            { special handling for specializations inside generic function declarations }
-                            prettynamepart:=tdef(symtablestack.top.defowner).fullownerhierarchyname(true)+tprocdef(symtablestack.top.defowner).procsym.prettyname;
-                          end
-                        else
-                          begin
-                            prettynamepart:=typeparam.resultdef.fullownerhierarchyname(true);
+                            if (symtablestack.top.symtabletype=parasymtable) and
+                                (symtablestack.top.defowner.typ=procdef) and
+                                (typeparam.resultdef.owner=symtablestack.top) then
+                              begin
+                                { special handling for specializations inside generic function declarations }
+                                prettynamepart:=tdef(symtablestack.top.defowner).fullownerhierarchyname(true)+tprocdef(symtablestack.top.defowner).procsym.prettyname;
+                              end
+                            else
+                              begin
+                                prettynamepart:=typeparam.resultdef.fullownerhierarchyname(true);
+                              end;
                           end;
                         specializename:=specializename+namepart;
                         if not first then
                           prettyname:=prettyname+',';
-                        prettyname:=prettyname+prettynamepart+typeparam.resultdef.typesym.prettyname;
+                        if constprettyname <> '' then
+                          prettyname:=prettyname+constprettyname
+                        else
+                          prettyname:=prettyname+prettynamepart+typeparam.resultdef.typesym.prettyname;
                       end;
                   end
                 else
@@ -411,12 +461,12 @@ uses
       end;
 
 
-    function parse_generic_specialization_types(genericdeflist:tfpobjectlist;poslist:tfplist;out prettyname,specializename:ansistring):boolean;
+    function parse_generic_specialization_types(paramlist:tfpobjectlist;poslist:tfplist;out prettyname,specializename:ansistring):boolean;
       var
         dummypos : tfileposinfo;
       begin
         FillChar(dummypos, SizeOf(tfileposinfo), 0);
-        result:=parse_generic_specialization_types_internal(genericdeflist,poslist,prettyname,specializename,nil,dummypos);
+        result:=parse_generic_specialization_types_internal(paramlist,poslist,prettyname,specializename,nil,dummypos);
       end;
 
 
@@ -578,7 +628,7 @@ uses
         context:=tspecializationcontext.create;
 
         { Parse type parameters }
-        err:=not parse_generic_specialization_types_internal(context.genericdeflist,context.poslist,context.prettyname,context.specializename,parsedtype,parsedpos);
+        err:=not parse_generic_specialization_types_internal(context.paramlist,context.poslist,context.prettyname,context.specializename,parsedtype,parsedpos);
         if err then
           begin
             if not try_to_consume(_GT) then
@@ -627,7 +677,7 @@ uses
 
         { search a generic with the given count of params }
         countstr:='';
-        str(context.genericdeflist.Count,countstr);
+        str(context.paramlist.Count,countstr);
 
         genname:=genname+'$'+countstr;
         ugenname:=upper(genname);
@@ -656,7 +706,7 @@ uses
             result:=generrordef;
             exit;
           end;
-
+        
         { we've found the correct def }
         if context.sym.typ=typesym then
           result:=tstoreddef(ttypesym(context.sym).typedef)
@@ -747,6 +797,7 @@ uses
         hintsprocessed : boolean;
         pd : tprocdef;
         pdflags : tpdflags;
+        typedef : tstoreddef;
       begin
         if not assigned(context) then
           internalerror(2015052203);
@@ -755,7 +806,7 @@ uses
 
         pd:=nil;
 
-        if not check_generic_constraints(genericdef,context.genericdeflist,context.poslist) then
+        if not check_generic_constraints(genericdef,context.paramlist,context.poslist) then
           begin
             { the parameters didn't fit the constraints, so don't continue with the
               specialization }
@@ -771,20 +822,19 @@ uses
         else
           prettyname:=genericdef.typesym.prettyname;
         prettyname:=prettyname+'<'+context.prettyname+'>';
-
         generictypelist:=tfphashobjectlist.create(false);
 
         { build the list containing the types for the generic params }
         if not assigned(genericdef.genericparas) then
           internalerror(2013092601);
-        if context.genericdeflist.count<>genericdef.genericparas.count then
+        if context.paramlist.count<>genericdef.genericparas.count then
           internalerror(2013092603);
         for i:=0 to genericdef.genericparas.Count-1 do
           begin
             srsym:=tsym(genericdef.genericparas[i]);
             if not (sp_generic_para in srsym.symoptions) then
               internalerror(2013092602);
-            generictypelist.add(srsym.realname,tdef(context.genericdeflist[i]).typesym);
+            generictypelist.add(srsym.realname,context.paramlist[i]);
           end;
 
         { Special case if we are referencing the current defined object }
@@ -1199,8 +1249,8 @@ uses
 
     function parse_generic_parameters(allowconstraints:boolean):tfphashobjectlist;
       var
-        generictype : ttypesym;
-        i,firstidx : longint;
+        generictype : tstoredsym;
+        i,firstidx,const_list_index : longint;
         srsymtable : tsymtable;
         basedef,def : tdef;
         defname : tidstring;
@@ -1208,22 +1258,87 @@ uses
         doconsume : boolean;
         constraintdata : tgenericconstraintdata;
         old_block_type : tblock_type;
+        is_const,last_is_const : boolean;
+        last_token : ttoken;
+        last_type_pos : tfileposinfo;
       begin
         result:=tfphashobjectlist.create(false);
         firstidx:=0;
+        const_list_index:=0;
         old_block_type:=block_type;
         block_type:=bt_type;
+        is_const:=false;
+        last_is_const:=false;
+        last_token:=NOTOKEN;
         repeat
+          if try_to_consume(_CONST) then
+            begin
+              { last param was const without semicolon terminator }
+              if (result.count>0) and last_is_const and (last_token<>_SEMICOLON) then
+                MessagePos2(last_type_pos,scan_f_syn_expected,arraytokeninfo[_SEMICOLON].str,arraytokeninfo[last_token].str);
+              is_const := true;
+              const_list_index := result.count;
+            end;
           if token=_ID then
             begin
-              generictype:=ctypesym.create(orgpattern,cundefinedtype,false);
+              if is_const then
+                begin
+                  { last param was type without semicolon terminator }
+                  if (result.count>0) and not last_is_const and (last_token<>_SEMICOLON) then
+                    MessagePos2(last_type_pos,scan_f_syn_expected,arraytokeninfo[_SEMICOLON].str,arraytokeninfo[last_token].str);
+                  generictype:=tconstsym.create_undefined(orgpattern,cundefinedtype);
+                end
+              else
+                begin
+                  { last param was const without semicolon terminator }
+                  if (result.count>0) and last_is_const and (last_token<>_SEMICOLON) then
+                    MessagePos2(last_type_pos,scan_f_syn_expected,arraytokeninfo[_SEMICOLON].str,arraytokeninfo[last_token].str);
+                  generictype:=ttypesym.create(orgpattern,cundefinedtype,false);
+                end;
               { type parameters need to be added as strict private }
               generictype.visibility:=vis_strictprivate;
               include(generictype.symoptions,sp_generic_para);
               result.add(orgpattern,generictype);
+              last_is_const:=is_const;
             end;
           consume(_ID);
-          if try_to_consume(_COLON) then
+          { const restriction }
+          if is_const then
+            begin
+              if try_to_consume(_COLON) then
+                begin
+                  def := nil;
+                  { parse the type and assign the const type to generictype  }
+                  single_type(def,[]);
+                  for i:=const_list_index to result.count-1 do
+                    begin
+                      { finalize constant information once type is known }
+                      if assigned(def) and (def.typ in tgeneric_param_const_types) then
+                        begin
+                          case def.typ of
+                            orddef:
+                              tconstsym(result[i]).consttyp:=constord;
+                            stringdef:
+                              tconstsym(result[i]).consttyp:=conststring;
+                            floatdef:
+                              tconstsym(result[i]).consttyp:=constreal;
+                            setdef:
+                              tconstsym(result[i]).consttyp:=constset;
+                            { pointer always refers to nil with constants }
+                            pointerdef:
+                              tconstsym(result[i]).consttyp:=constnil;
+                          end;
+                          tconstsym(result[i]).constdef:=def;
+                        end
+                      else
+                        Message(type_e_mismatch);
+                    end;
+                  { after type restriction const list terminates }
+                  is_const:=false;
+                end;
+            end
+          { type restriction }
+          else if try_to_consume(_COLON) then
             begin
               if not allowconstraints then
                 { TODO }
@@ -1338,6 +1453,7 @@ uses
                     basedef:=cobjectdef.create(tobjectdef(def).objecttype,defname,tobjectdef(def),false);
                     constraintdata.interfaces.delete(0);
                   end;
+
               if basedef.typ<>errordef then
                 with tstoreddef(basedef) do
                   begin
@@ -1363,21 +1479,27 @@ uses
                 begin
                   { two different typeless parameters are considered as incompatible }
                   for i:=firstidx to result.count-1 do
-                    begin
-                      ttypesym(result[i]).typedef:=cundefineddef.create(false);
-                      ttypesym(result[i]).typedef.typesym:=ttypesym(result[i]);
-                    end;
+                    if tsym(result[i]).typ<>constsym then
+                      begin
+                        ttypesym(result[i]).typedef:=cundefineddef.create(false);
+                        ttypesym(result[i]).typedef.typesym:=ttypesym(result[i]);
+                      end;
                   { a semicolon terminates a type parameter group }
                   firstidx:=result.count;
                 end;
             end;
+          if token = _SEMICOLON then
+            is_const:=false;
+          last_token:=token;
+          last_type_pos:=current_filepos;
         until not (try_to_consume(_COMMA) or try_to_consume(_SEMICOLON));
         { two different typeless parameters are considered as incompatible }
         for i:=firstidx to result.count-1 do
-          begin
-            ttypesym(result[i]).typedef:=cundefineddef.create(false);
-            ttypesym(result[i]).typedef.typesym:=ttypesym(result[i]);
-          end;
+          if tsym(result[i]).typ<>constsym then
+            begin
+              ttypesym(result[i]).typedef:=cundefineddef.create(false);
+              ttypesym(result[i]).typedef.typesym:=ttypesym(result[i]);
+            end;
         block_type:=old_block_type;
       end;
 
@@ -1385,7 +1507,9 @@ uses
     procedure insert_generic_parameter_types(def:tstoreddef;genericdef:tstoreddef;genericlist:tfphashobjectlist);
       var
         i : longint;
-        generictype,sym : ttypesym;
+        generictype : tstoredsym;
+        generictypedef : tdef;
+        sym : tsym;
         st : tsymtable;
       begin
         def.genericdef:=genericdef;
@@ -1410,10 +1534,22 @@ uses
           def.genericparas:=tfphashobjectlist.create(false);
         for i:=0 to genericlist.count-1 do
           begin
-            generictype:=ttypesym(genericlist[i]);
+            generictype:=tstoredsym(genericlist[i]);
             if assigned(generictype.owner) then
               begin
-                sym:=ctypesym.create(genericlist.nameofindex(i),generictype.typedef,true);
+                if generictype.typ=typesym then
+                  sym:=ctypesym.create(genericlist.nameofindex(i),ttypesym(generictype).typedef,true)
+                else if generictype.typ=constsym then
+                  { generictype is a constsym that was created in create_generic_constsym 
+                    during phase 1 so we pass this directly without copying }
+                  begin
+                    sym:=generictype;
+                    { the sym name is still undefined so we set it to match
+                      the generic param name so it's accessible }
+                    sym.realname:=genericlist.nameofindex(i);
+                  end
+                else
+                  internalerror(2019021602);
                 { type parameters need to be added as strict private }
                 sym.visibility:=vis_strictprivate;
                 st.insert(sym);
@@ -1421,13 +1557,17 @@ uses
               end
             else
               begin
-                if (generictype.typedef.typ=undefineddef) and (generictype.typedef<>cundefinedtype) then
+                if generictype.typ=typesym then
                   begin
-                    { the generic parameters were parsed before the genericdef existed thus the
-                      undefineddefs were added as part of the parent symtable }
-                    if assigned(generictype.typedef.owner) then
-                      generictype.typedef.owner.DefList.Extract(generictype.typedef);
-                    generictype.typedef.changeowner(st);
+                    generictypedef:=ttypesym(generictype).typedef;
+                    if (generictypedef.typ=undefineddef) and (generictypedef<>cundefinedtype) then
+                      begin
+                        { the generic parameters were parsed before the genericdef existed thus the
+                          undefineddefs were added as part of the parent symtable }
+                        if assigned(generictypedef.owner) then
+                          generictypedef.owner.DefList.Extract(generictypedef);
+                        generictypedef.changeowner(st);
+                      end;
                   end;
                 st.insert(generictype);
                 include(generictype.symoptions,sp_generic_para);
diff --git a/compiler/ptype.pas b/compiler/ptype.pas
index 5236f253f1..6b642803b8 100644
--- a/compiler/ptype.pas
+++ b/compiler/ptype.pas
@@ -1436,7 +1436,9 @@ implementation
                                  highval:=tordconstnode(trangenode(pt).right).value;
                                  if highval<lowval then
                                   begin
-                                    Message(parser_e_array_lower_less_than_upper_bound);
+                                    { ignore error if node is generic param }
+                                    if not (nf_generic_para in pt.flags) then
+                                      Message(parser_e_array_lower_less_than_upper_bound);
                                     highval:=lowval;
                                   end
                                  else if (lowval<int64(low(asizeint))) or
diff --git a/compiler/symconst.pas b/compiler/symconst.pas
index bf284cb58f..ad7424f60a 100644
--- a/compiler/symconst.pas
+++ b/compiler/symconst.pas
@@ -231,7 +231,10 @@ type
       because we have to access this information in the symtable unit }
     df_llvm_no_struct_packing,
     { internal def that's not for any export }
-    df_internal
+    df_internal,
+    { the def was derived with generic type or const fields so the size
+      of the def can not be determined }
+    df_has_generic_fields
   );
   tdefoptions=set of tdefoption;
 
@@ -659,7 +662,7 @@ type
     arraydef,recorddef,pointerdef,orddef,
     stringdef,enumdef,procdef,objectdef,errordef,
     filedef,formaldef,setdef,procvardef,floatdef,
-    classrefdef,forwarddef,variantdef,undefineddef
+    classrefdef,forwarddef,variantdef,genericconstdef,undefineddef
   );
 
   { possible types for symtable entries }
@@ -700,7 +703,8 @@ type
   tconsttyp = (constnone,
     constord,conststring,constreal,
     constset,constpointer,constnil,
-    constresourcestring,constwstring,constguid
+    constresourcestring,constwstring,constguid,
+    constundefined
   );
 
   { RTTI information to store }
@@ -840,7 +844,7 @@ inherited_objectoptions : tobjectoptions = [oo_has_virtual,oo_has_private,oo_has
        'abstractdef','arraydef','recorddef','pointerdef','orddef',
        'stringdef','enumdef','procdef','objectdef','errordef',
        'filedef','formaldef','setdef','procvardef','floatdef',
-       'classrefdef','forwarddef','variantdef','undefineddef'
+       'classrefdef','forwarddef','variantdef','genconstdef','undefineddef'
      );
 
      EqualTypeName : array[tequaltype] of string[16] = (
diff --git a/compiler/symdef.pas b/compiler/symdef.pas
index 7db695005e..4be6f572af 100644
--- a/compiler/symdef.pas
+++ b/compiler/symdef.pas
@@ -2293,13 +2293,26 @@ implementation
          for i:=0 to genericparas.count-1 do
            begin
              sym:=tsym(genericparas[i]);
-             if sym.typ<>symconst.typesym then
+             { sym must be either a type or const }
+             if not (sym.typ in [symconst.typesym,symconst.constsym]) then
                internalerror(2014050903);
              if sym.owner.defowner<>self then
                exit(false);
            end;
      end;
 
+   function tstoreddef.is_generic_param_const(index:integer):boolean;
+     begin
+       result := tsym(genericparas[index]).typ = constsym;
+     end;  
+
+   function tstoreddef.get_generic_param_def(index:integer):tdef;
+     begin
+       if tsym(genericparas[index]).typ = constsym then
+         result := tconstsym(genericparas[index]).constdef
+       else
+         result := ttypesym(genericparas[index]).typedef;
+     end;
 
    function tstoreddef.is_specialization: boolean;
      var
@@ -2316,12 +2329,12 @@ implementation
            for i:=0 to genericparas.count-1 do
              begin
                sym:=tsym(genericparas[i]);
-               if sym.typ<>symconst.typesym then
+               { sym must be either a type or const }
+               if not (sym.typ in [symconst.typesym,symconst.constsym]) then
                  internalerror(2014050904);
                if sym.owner.defowner<>self then
                  exit(true);
              end;
-           result:=false;
          end;
      end;
 
diff --git a/compiler/symsym.pas b/compiler/symsym.pas
index 2384509f47..2d0e499f54 100644
--- a/compiler/symsym.pas
+++ b/compiler/symsym.pas
@@ -157,7 +157,7 @@ interface
           fprettyname : ansistring;
           constructor create(const n : string;def:tdef;doregister:boolean);virtual;
           destructor destroy;override;
-          constructor ppuload(ppufile:tcompilerppufile);
+          constructor ppuload(ppufile:tcompilerppufile);virtual;
           { do not override this routine in platform-specific subclasses,
             override ppuwrite_platform instead }
           procedure ppuwrite(ppufile:tcompilerppufile);override;final;
@@ -392,6 +392,7 @@ interface
           constructor create_ptr(const n : string;t : tconsttyp;v : pointer;def:tdef);virtual;
           constructor create_string(const n : string;t : tconsttyp;str:pchar;l:longint;def:tdef);virtual;
           constructor create_wstring(const n : string;t : tconsttyp;pw:pcompilerwidestring);virtual;
+          constructor create_undefined(const n : string;def: tdef);
           constructor ppuload(ppufile:tcompilerppufile);
           destructor  destroy;override;
           procedure buildderef;override;
@@ -1584,7 +1585,6 @@ implementation
           tparasymtable(parast).ppuwrite(ppufile);
       end;
 
-
 {****************************************************************************
                             TABSTRACTVARSYM
 ****************************************************************************}
@@ -2356,6 +2356,13 @@ implementation
          value.len:=getlengthwidestring(pw);
       end;
 
+    constructor tconstsym.create_undefined(const n : string;def: tdef);
+      begin
+        inherited create(constsym,n,true);
+        fillchar(value, sizeof(value), #0);
+        consttyp:=constundefined;
+        constdef:=def;
+      end;
 
     constructor tconstsym.ppuload(ppufile:tcompilerppufile);
       var
@@ -2428,7 +2435,8 @@ implementation
                new(pguid(value.valueptr));
                ppufile.getdata(value.valueptr^,sizeof(tguid));
              end;
-           constnil :
+           constnil,
+           constundefined :
              ppufile.getderef(constdefderef);
            else
              Message1(unit_f_ppu_invalid_entry,tostr(ord(consttyp)));
@@ -2460,7 +2468,7 @@ implementation
       begin
         inherited;
         case consttyp  of
-          constnil,constord,constreal,constpointer,constset,conststring,constresourcestring,constguid:
+          constnil,constord,constreal,constpointer,constset,conststring,constresourcestring,constguid,constundefined:
             constdefderef.build(constdef);
           constwstring:
             ;
@@ -2473,7 +2481,7 @@ implementation
     procedure tconstsym.deref;
       begin
         case consttyp of
-          constnil,constord,constreal,constpointer,constset,conststring,constresourcestring,constguid:
+          constnil,constord,constreal,constpointer,constset,conststring,constresourcestring,constguid,constundefined:
             constdef:=tdef(constdefderef.resolve);
           constwstring:
             constdef:=carraydef.getreusable(cwidechartype,getlengthwidestring(pcompilerwidestring(value.valueptr)));
@@ -2488,7 +2496,8 @@ implementation
          inherited ppuwrite(ppufile);
          ppufile.putbyte(byte(consttyp));
          case consttyp of
-           constnil :
+           constnil,
+           constundefined :
              ppufile.putderef(constdefderef);
            constord :
              begin
@@ -2641,7 +2650,6 @@ implementation
           result:=inherited prettyname;
       end;
 
-
 {****************************************************************************
                                   TSYSSYM
 ****************************************************************************}
diff --git a/compiler/symtable.pas b/compiler/symtable.pas
index c7abd7da58..906e2da4a3 100644
--- a/compiler/symtable.pas
+++ b/compiler/symtable.pas
@@ -2916,7 +2916,7 @@ implementation
 
     function generate_objectpascal_helper_key(def:tdef):string;
       begin
-        if not assigned(def) then
+        if not assigned(def) or (def.typ = errordef) then
           internalerror(2013020501);
         if def.typ in [recorddef,objectdef] then
           result:=make_mangledname('',tabstractrecorddef(def).symtable,'')
diff --git a/tests/test/tgenconst1.pp b/tests/test/tgenconst1.pp
new file mode 100644
index 0000000000..297b982b0f
--- /dev/null
+++ b/tests/test/tgenconst1.pp
@@ -0,0 +1,33 @@
+{$mode objfpc}
+program tgenconst1;
+
+type
+	kNames = set of (Blaise,Pascal);
+	kChars = set of char;
+type
+	generic TBoolean<const U: boolean> = record end;
+	generic TString<const U: string> = record end;
+	generic TFloat<const U: single> = record end;
+	generic TInteger<const U: integer> = record end;
+	generic TChar<const U: char> = record end;
+	generic TByte<const U: byte> = record end;
+	generic TQWord<const U: QWord> = record end;
+	generic TUndefined<const U> = record end;
+	generic TNames<const U: kNames> = record end;
+	generic TChars<const U: kChars> = record end;
+	generic TPointer<const U: pointer> = record end;
+
+var
+	a: specialize TBoolean<true>;
+	b: specialize TString<'string'>;
+	c: specialize TFloat<1>;
+	d: specialize TInteger<10>;
+	e: specialize TByte<255>;
+	f: specialize TChar<'a'>;
+	g: specialize TUndefined<nil>;
+	h: specialize TNames<[Blaise,Pascal]>;
+	i: specialize TChars<['a','b']>;
+	j: specialize TQWord<10>;
+	k: specialize TPointer<nil>;
+begin
+end.
diff --git a/tests/test/tgenconst10.pp b/tests/test/tgenconst10.pp
new file mode 100644
index 0000000000..f05a27718c
--- /dev/null
+++ b/tests/test/tgenconst10.pp
@@ -0,0 +1,13 @@
+{%FAIL}
+
+{$mode objfpc}
+
+program tgenconst10;
+
+type
+	generic TByte<T> = record end;
+	
+var
+	a: specialize TByte<10>;
+begin
+end.
diff --git a/tests/test/tgenconst11.pp b/tests/test/tgenconst11.pp
new file mode 100644
index 0000000000..ea409bec9b
--- /dev/null
+++ b/tests/test/tgenconst11.pp
@@ -0,0 +1,21 @@
+{%FAIL}
+{$mode objfpc}
+program tgenconst11;
+type
+	TEnum = (aaa,bbb,ccc,ddd);
+type
+	generic TConst<const U> = class end;
+
+var
+	a:specialize TConst<10>;
+	b:specialize TConst<10.5>;
+	c:specialize TConst<'string'>;
+	d:specialize TConst<[1,2,3]>;
+	e:specialize TConst<[aaa,bbb,ccc]>;
+begin
+	a:=specialize TConst<20>.Create;
+	b:=specialize TConst<10.1>.Create;
+	c:=specialize TConst<'_string'>.Create;
+	d:=specialize TConst<[1,2,3,4]>.Create;
+	e:=specialize TConst<[aaa,bbb,ccc,ddd]>.Create;
+end.
\ No newline at end of file
diff --git a/tests/test/tgenconst12.pp b/tests/test/tgenconst12.pp
new file mode 100644
index 0000000000..8f591f6867
--- /dev/null
+++ b/tests/test/tgenconst12.pp
@@ -0,0 +1,16 @@
+{$mode objfpc}
+program tgenconst12;
+
+type
+  generic TTest<const U> = class
+  		class procedure DoThis;
+  end;
+
+class procedure TTest.DoThis;
+begin
+end;
+
+type
+	ATest = specialize TTest<100>;
+begin 
+end.
diff --git a/tests/test/tgenconst13.pp b/tests/test/tgenconst13.pp
new file mode 100644
index 0000000000..0d5f8b1813
--- /dev/null
+++ b/tests/test/tgenconst13.pp
@@ -0,0 +1,20 @@
+{$mode objfpc}
+program tgenconst13;
+type
+	TEnum = (aaa,bbb,ccc);
+type
+	generic TConst<const U> = class end;
+
+var
+	a:specialize TConst<10>;
+	b:specialize TConst<10.5>;
+	c:specialize TConst<'string'>;
+	d:specialize TConst<[1,2,3]>;
+	e:specialize TConst<[aaa,bbb,ccc]>;
+begin
+	a:=specialize TConst<10>.Create;
+	b:=specialize TConst<10.5>.Create;
+	c:=specialize TConst<'string'>.Create;
+	d:=specialize TConst<[1,2,3]>.Create;
+	e:=specialize TConst<[aaa,bbb,ccc]>.Create;
+end.
diff --git a/tests/test/tgenconst2.pp b/tests/test/tgenconst2.pp
new file mode 100644
index 0000000000..aa3a960634
--- /dev/null
+++ b/tests/test/tgenconst2.pp
@@ -0,0 +1,12 @@
+{$mode objfpc}
+program tgenconst2;
+
+type
+	generic TStuff1<T1,T2;const U1,U2> = record end;
+	generic TStuff2<T1,T2;const U1,U2:integer> = record end;
+	
+var
+	a: specialize TStuff1<integer,string,10,'string'>;
+	b: specialize TStuff2<integer,string,10,10>;
+begin
+end.
diff --git a/tests/test/tgenconst3.pp b/tests/test/tgenconst3.pp
new file mode 100644
index 0000000000..aea0e307e2
--- /dev/null
+++ b/tests/test/tgenconst3.pp
@@ -0,0 +1,16 @@
+{$mode objfpc}
+{$modeswitch advancedrecords}
+program tgenconst3;
+
+type
+	generic TList<T;const U:integer> = record
+		const
+			max = U;
+		public
+			m_list: array[0..max-1] of T;
+	end;
+
+var
+	list: specialize TList<integer,128>;
+begin
+end.
diff --git a/tests/test/tgenconst4.pp b/tests/test/tgenconst4.pp
new file mode 100644
index 0000000000..a1fae00c43
--- /dev/null
+++ b/tests/test/tgenconst4.pp
@@ -0,0 +1,11 @@
+{$mode objfpc}
+program tgenconst4;
+
+generic procedure DoThis<T;const U:string>(msg:string = U);
+begin
+	writeln(msg, ' sizeof:',sizeof(t), ' default: ', U);
+end;
+
+begin
+	specialize DoThis<integer,'genparam'>('hello world');
+end.
diff --git a/tests/test/tgenconst5.pp b/tests/test/tgenconst5.pp
new file mode 100644
index 0000000000..63514a976c
--- /dev/null
+++ b/tests/test/tgenconst5.pp
@@ -0,0 +1,24 @@
+{$mode objfpc}
+program tgenconst5;
+
+type
+	generic THelperA<const U:integer> = record
+		list: array[0..U-1] of byte;
+	end;
+
+type
+	generic THelperB<T> = record
+		value: T;
+	end;
+
+type
+	generic TList<T; const U:integer> = record
+		helperA: specialize THelperA<U>;
+		helperB: specialize THelperB<T>;
+	end;
+
+var
+	list: specialize TList<integer,32>;
+begin
+	writeln('sizeof:',sizeof(list));
+end.
diff --git a/tests/test/tgenconst6.pp b/tests/test/tgenconst6.pp
new file mode 100644
index 0000000000..3ee3785423
--- /dev/null
+++ b/tests/test/tgenconst6.pp
@@ -0,0 +1,21 @@
+{$mode delphi}
+program tgenconst6;
+
+type
+	TList<T;const U> = class
+		list: array[0..U-1] of T;
+		function capacity: integer;
+	end;
+
+function TList<T,U>.capacity: integer;
+begin
+	result := U;	
+end;	
+
+var
+	nums:TList<integer,16>;
+	strs:TList<string,16>;
+begin
+	nums := TList<integer,16>.Create;
+	strs := TList<string,16>.Create;
+end.
diff --git a/tests/test/tgenconst7.pp b/tests/test/tgenconst7.pp
new file mode 100644
index 0000000000..9d8e81ef05
--- /dev/null
+++ b/tests/test/tgenconst7.pp
@@ -0,0 +1,11 @@
+{%FAIL}
+{$mode objfpc}
+program tgenconst7;
+
+type
+	generic TInteger<const U: integer> = record end;
+
+var
+	a: specialize TInteger<'string'>;
+begin
+end.
diff --git a/tests/test/tgenconst8.pp b/tests/test/tgenconst8.pp
new file mode 100644
index 0000000000..75844f7181
--- /dev/null
+++ b/tests/test/tgenconst8.pp
@@ -0,0 +1,11 @@
+{%FAIL}
+{$mode objfpc}
+program tgenconst8;
+
+type
+	generic TByte<const U: Byte> = record end;
+	
+var
+	a: specialize TByte<300>;
+begin
+end.
diff --git a/tests/test/tgenconst9.pp b/tests/test/tgenconst9.pp
new file mode 100644
index 0000000000..939cb90302
--- /dev/null
+++ b/tests/test/tgenconst9.pp
@@ -0,0 +1,11 @@
+{%FAIL}
+{$mode objfpc}
+program tgenconst9;
+
+type
+	generic TByte<const U: Byte> = record end;
+	
+var
+	a: specialize TByte<string>;
+begin
+end.
-- 
2.17.2 (Apple Git-113)

From 57a8c0589a5c881dd55d36dbf03832cb024e3cf3 Mon Sep 17 00:00:00 2001
From: Ryan Joseph <genericptr@gmail.com>
Date: Sun, 17 Mar 2019 16:57:25 -0400
Subject: [PATCH] constants in generics

---
 compiler/defcmp.pas                |   9 +-
 compiler/htypechk.pas              |   2 +-
 compiler/ncon.pas                  |  38 +-
 compiler/nmat.pas                  |   5 +-
 compiler/node.pas                  |  19 +-
 compiler/nset.pas                  |   5 +-
 compiler/pdecl.pas                 |  43 +-
 compiler/pdecvar.pas               |   4 +
 compiler/pexpr.pas                 |  11 +-
 compiler/pgentype.pas              |   8 +-
 compiler/pgenutil.pas              | 693 ++++++++++++++++++++---------
 compiler/ppu.pas                   |   2 +-
 compiler/ptype.pas                 |   4 +-
 compiler/symconst.pas              |  12 +-
 compiler/symdef.pas                |  22 +-
 compiler/symsym.pas                |  22 +-
 compiler/symtable.pas              |   2 +-
 compiler/utils/ppuutils/ppudump.pp |   3 +-
 tests/test/tgenconst1.pp           |  33 ++
 tests/test/tgenconst10.pp          |  13 +
 tests/test/tgenconst11.pp          |  21 +
 tests/test/tgenconst12.pp          |  16 +
 tests/test/tgenconst13.pp          |  20 +
 tests/test/tgenconst14.pp          |  29 ++
 tests/test/tgenconst15.pp          |  30 ++
 tests/test/tgenconst2.pp           |  12 +
 tests/test/tgenconst3.pp           |  16 +
 tests/test/tgenconst4.pp           |  11 +
 tests/test/tgenconst5.pp           |  24 +
 tests/test/tgenconst6.pp           |  21 +
 tests/test/tgenconst7.pp           |  11 +
 tests/test/tgenconst8.pp           |  11 +
 tests/test/tgenconst9.pp           |  11 +
 33 files changed, 923 insertions(+), 260 deletions(-)
 create mode 100644 tests/test/tgenconst1.pp
 create mode 100644 tests/test/tgenconst10.pp
 create mode 100644 tests/test/tgenconst11.pp
 create mode 100644 tests/test/tgenconst12.pp
 create mode 100644 tests/test/tgenconst13.pp
 create mode 100644 tests/test/tgenconst14.pp
 create mode 100644 tests/test/tgenconst15.pp
 create mode 100644 tests/test/tgenconst2.pp
 create mode 100644 tests/test/tgenconst3.pp
 create mode 100644 tests/test/tgenconst4.pp
 create mode 100644 tests/test/tgenconst5.pp
 create mode 100644 tests/test/tgenconst6.pp
 create mode 100644 tests/test/tgenconst7.pp
 create mode 100644 tests/test/tgenconst8.pp
 create mode 100644 tests/test/tgenconst9.pp

diff --git a/compiler/defcmp.pas b/compiler/defcmp.pas
index 3f5882f762..793dbbbe76 100644
--- a/compiler/defcmp.pas
+++ b/compiler/defcmp.pas
@@ -175,7 +175,6 @@ implementation
       symtable,symsym,symcpu,
       defutil,symutil;
 
-
     function compare_defs_ext(def_from,def_to : tdef;
                               fromtreetype : tnodetype;
                               var doconv : tconverttype;
@@ -337,9 +336,13 @@ implementation
                        internalerror(2012091302);
                      symfrom:=ttypesym(tstoreddef(def_from).genericparas[i]);
                      symto:=ttypesym(tstoreddef(def_to).genericparas[i]);
-                     if not (symfrom.typ=typesym) or not (symto.typ=typesym) then
+                     if not (symfrom.typ in [typesym,constsym]) or not (symto.typ in [typesym,constsym]) then
                        internalerror(2012121401);
-                     if not equal_defs(ttypesym(symfrom).typedef,ttypesym(symto).typedef) then
+                     if symto.typ <> symfrom.typ then
+                       diff:=true
+                     else if (symfrom.typ=constsym) and (symto.typ=constsym) and not equal_constsym(tconstsym(symfrom),tconstsym(symto),true) then
+                       diff:=true
+                     else if not equal_defs(ttypesym(symfrom).typedef,ttypesym(symto).typedef) then
                        diff:=true;
                      if diff then
                        break;
diff --git a/compiler/htypechk.pas b/compiler/htypechk.pas
index 07c035dc26..2358ea4b6d 100644
--- a/compiler/htypechk.pas
+++ b/compiler/htypechk.pas
@@ -2697,7 +2697,7 @@ implementation
               internalerror(2015060301);
             { check whether the given parameters are compatible
               to the def's constraints }
-            if not check_generic_constraints(pd,spezcontext.genericdeflist,spezcontext.poslist) then
+            if not check_generic_constraints(pd,spezcontext.paramlist,spezcontext.poslist) then
               exit;
             def:=generate_specialization_phase2(spezcontext,pd,false,'');
             case def.typ of
diff --git a/compiler/ncon.pas b/compiler/ncon.pas
index ae94637c28..fb5e94c09f 100644
--- a/compiler/ncon.pas
+++ b/compiler/ncon.pas
@@ -304,18 +304,48 @@ implementation
           constwstring :
             p1:=cstringconstnode.createunistr(pcompilerwidestring(p.value.valueptr));
           constreal :
-            p1:=crealconstnode.create(pbestreal(p.value.valueptr)^,p.constdef);
+            begin
+              if sp_generic_para in p.symoptions then
+                p1:=crealconstnode.create(default(bestreal),p.constdef)
+              else
+                p1:=crealconstnode.create(pbestreal(p.value.valueptr)^,p.constdef);
+            end;
           constset :
-            p1:=csetconstnode.create(pconstset(p.value.valueptr),p.constdef);
+            begin
+              if sp_generic_para in p.symoptions then
+                p1:=csetconstnode.create(default(pconstset),p.constdef)
+              else
+                p1:=csetconstnode.create(pconstset(p.value.valueptr),p.constdef);
+            end;
           constpointer :
-            p1:=cpointerconstnode.create(p.value.valueordptr,p.constdef);
+            begin
+              if sp_generic_para in p.symoptions then
+                p1:=cpointerconstnode.create(default(tconstptruint),p.constdef)
+              else
+                p1:=cpointerconstnode.create(p.value.valueordptr,p.constdef);
+            end;
           constnil :
             p1:=cnilnode.create;
+          { constundefined is a placeholder for unrestricted generic const params
+            so we just treat it as a nil node. }
+          constundefined :
+            begin
+              p1:=cnilnode.create;
+              p1.resultdef := p.constdef;
+            end;
           constguid :
-            p1:=cguidconstnode.create(pguid(p.value.valueptr)^);
+            begin
+              if sp_generic_para in p.symoptions then
+                p1:=cguidconstnode.create(default(tguid))
+              else
+                p1:=cguidconstnode.create(pguid(p.value.valueptr)^);
+            end;
           else
             internalerror(200205103);
         end;
+        { transfer generic param flag from symbol to node }
+        if sp_generic_para in p.symoptions then
+          include(p1.flags,nf_generic_para);
         genconstsymtree:=p1;
       end;
 
diff --git a/compiler/nmat.pas b/compiler/nmat.pas
index 355b493da4..d10dff6128 100644
--- a/compiler/nmat.pas
+++ b/compiler/nmat.pas
@@ -129,7 +129,10 @@ implementation
               end;
             if rv = 0 then
               begin
-                Message(parser_e_division_by_zero);
+                { if the node is derived from a generic const parameter
+                  then don't issue an error }
+                if not (nf_generic_para in flags) then
+                  Message(parser_e_division_by_zero);
                 { recover }
                 tordconstnode(right).value := 1;
               end;
diff --git a/compiler/node.pas b/compiler/node.pas
index b8600000bf..f9ab8ec521 100644
--- a/compiler/node.pas
+++ b/compiler/node.pas
@@ -194,7 +194,8 @@ interface
           'loadparentfpn',
           'objcselectorn',
           'objcprotocoln',
-          'specializen');
+          'specializen'
+          );
 
       { a set containing all const nodes }
       nodetype_const = [ordconstn,
@@ -272,10 +273,13 @@ interface
          nf_block_with_exit,
 
          { tloadvmtaddrnode }
-         nf_ignore_for_wpo  { we know that this loadvmtaddrnode cannot be used to construct a class instance }
+         nf_ignore_for_wpo,  { we know that this loadvmtaddrnode cannot be used to construct a class instance }
 
-         { WARNING: there are now 31 elements in this type, and a set of this
-             type is written to the PPU. So before adding more than 32 elements,
+         { node is derived from generic parameter }
+         nf_generic_para
+
+         { WARNING: there are now 32 elements in this type, and a set of this
+             type is written to the PPU. So before adding more elements,
              either move some flags to specific nodes, or stream a normalset
              to the ppu
          }
@@ -1078,7 +1082,12 @@ implementation
     constructor tbinarynode.create(t:tnodetype;l,r : tnode);
       begin
          inherited create(t,l);
-         right:=r
+         { transfer generic paramater flag }
+         if assigned(l) and (nf_generic_para in l.flags) then
+           include(flags,nf_generic_para)
+         else if assigned(r) and (nf_generic_para in r.flags) then
+           include(flags,nf_generic_para);
+         right:=r;
       end;
 
 
diff --git a/compiler/nset.pas b/compiler/nset.pas
index 6270ec582e..4360a7340d 100644
--- a/compiler/nset.pas
+++ b/compiler/nset.pas
@@ -392,8 +392,9 @@ implementation
          { both types must be compatible }
          if compare_defs(left.resultdef,right.resultdef,left.nodetype)=te_incompatible then
            IncompatibleTypes(left.resultdef,right.resultdef);
-         { Check if only when its a constant set }
-         if (left.nodetype=ordconstn) and (right.nodetype=ordconstn) then
+         { check if only when its a constant set and
+           ignore range nodes which are generic parameter derived }
+         if not (nf_generic_para in flags) and (left.nodetype=ordconstn) and (right.nodetype=ordconstn) then
           begin
             { upper limit must be greater or equal than lower limit }
             if (tordconstnode(left).value>tordconstnode(right).value) and
diff --git a/compiler/pdecl.pas b/compiler/pdecl.pas
index c5b5bcc921..767eec22f7 100644
--- a/compiler/pdecl.pas
+++ b/compiler/pdecl.pas
@@ -126,9 +126,14 @@ implementation
              end;
            setconstn :
              begin
-               new(ps);
-               ps^:=tsetconstnode(p).value_set^;
-               hp:=cconstsym.create_ptr(orgname,constset,ps,p.resultdef);
+               if nf_generic_para in p.flags then
+                 hp:=cconstsym.create_ptr(orgname,constset,nil,p.resultdef)
+               else
+                 begin
+                   new(ps);
+                   ps^:=tsetconstnode(p).value_set^;
+                   hp:=cconstsym.create_ptr(orgname,constset,ps,p.resultdef);
+                 end;
              end;
            pointerconstn :
              begin
@@ -141,18 +146,18 @@ implementation
            typen :
              begin
                if is_interface(p.resultdef) then
-                begin
-                  if assigned(tobjectdef(p.resultdef).iidguid) then
-                   begin
-                     new(pg);
-                     pg^:=tobjectdef(p.resultdef).iidguid^;
-                     hp:=cconstsym.create_ptr(orgname,constguid,pg,p.resultdef);
-                   end
-                  else
-                   Message1(parser_e_interface_has_no_guid,tobjectdef(p.resultdef).objrealname^);
-                end
-               else
-                Message(parser_e_illegal_expression);
+                 begin
+                   if assigned(tobjectdef(p.resultdef).iidguid) then
+                     begin
+                       new(pg);
+                       pg^:=tobjectdef(p.resultdef).iidguid^;
+                       hp:=cconstsym.create_ptr(orgname,constguid,pg,p.resultdef);
+                     end
+                    else
+                      Message1(parser_e_interface_has_no_guid,tobjectdef(p.resultdef).objrealname^);
+                 end
+               else 
+                 Message(parser_e_illegal_expression);
              end;
            inlinen:
              begin
@@ -179,6 +184,9 @@ implementation
            else
              Message(parser_e_illegal_expression);
         end;
+        { transfer generic param flag from node to symbol }
+        if nf_generic_para in p.flags then
+          include(hp.symoptions,sp_generic_para);
         current_tokenpos:=storetokenpos;
         p.free;
         readconstant:=hp;
@@ -507,8 +515,9 @@ implementation
                { we are not freeing the type parameters, so register them }
                for i:=0 to generictypelist.count-1 do
                  begin
-                    ttypesym(generictypelist[i]).register_sym;
-                    tstoreddef(ttypesym(generictypelist[i]).typedef).register_def;
+                    tstoredsym(generictypelist[i]).register_sym;
+                    if tstoredsym(generictypelist[i]).typ=typesym then
+                      tstoreddef(ttypesym(generictypelist[i]).typedef).register_def;
                  end;
 
                str(generictypelist.Count,s);
diff --git a/compiler/pdecvar.pas b/compiler/pdecvar.pas
index 4d39397e46..8121d87853 100644
--- a/compiler/pdecvar.pas
+++ b/compiler/pdecvar.pas
@@ -1675,6 +1675,10 @@ implementation
                    end;
                end;
 
+             { field type is a generic param so set a flag in the struct }
+             if assigned(hdef.typesym) and (sp_generic_para in hdef.typesym.symoptions) then
+               include(current_structdef.defoptions,df_has_generic_fields);
+
              { Process procvar directives }
              if maybe_parse_proc_directives(hdef) then
                semicoloneaten:=true;
diff --git a/compiler/pexpr.pas b/compiler/pexpr.pas
index bc0606ed4b..e6d9633ebd 100644
--- a/compiler/pexpr.pas
+++ b/compiler/pexpr.pas
@@ -446,6 +446,9 @@ implementation
                   { no packed bit support for these things }
                   if l=in_bitsizeof_x then
                     statement_syssym:=caddnode.create(muln,statement_syssym,cordconstnode.create(8,sinttype,true));
+                  { type sym is a generic parameter }
+                  if assigned(p1.resultdef.typesym) and (sp_generic_para in p1.resultdef.typesym.symoptions) then
+                    include(statement_syssym.flags,nf_generic_para);
                 end
               else
                begin
@@ -466,6 +469,9 @@ implementation
                    end
                  else
                    statement_syssym:=cordconstnode.create(p1.resultdef.packedbitsize,sinttype,true);
+                 { type def is a struct with generic fields }
+                 if df_has_generic_fields in p1.resultdef.defoptions then
+                    include(statement_syssym.flags,nf_generic_para);
                  { p1 not needed !}
                  p1.destroy;
                end;
@@ -4078,7 +4084,10 @@ implementation
                 gendef:=generate_specialization_phase2(spezcontext,tstoreddef(gendef),false,'');
                 spezcontext.free;
                 spezcontext:=nil;
-                gensym:=gendef.typesym;
+                if gendef.typ=errordef then
+                  gensym:=generrorsym
+                else
+                  gensym:=gendef.typesym;
               end;
             procdef:
               begin
diff --git a/compiler/pgentype.pas b/compiler/pgentype.pas
index b2847c78f6..85270df256 100644
--- a/compiler/pgentype.pas
+++ b/compiler/pgentype.pas
@@ -28,7 +28,7 @@ interface
 uses
   cclasses,
   globtype,
-  symtype,symbase;
+  symconst,symtype,symbase;
 
 const
   inline_specialization_block_types = [bt_type,bt_var_type,bt_const_type,bt_body];
@@ -42,7 +42,7 @@ type
 
   tspecializationcontext=class
   public
-    genericdeflist : tfpobjectlist;
+    paramlist : tfpobjectlist;
     poslist : tfplist;
     prettyname : ansistring;
     specializename : ansistring;
@@ -58,7 +58,7 @@ implementation
 
 constructor tspecializationcontext.create;
 begin
-  genericdeflist:=tfpobjectlist.create(false);
+  paramlist:=tfpobjectlist.create(false);
   poslist:=tfplist.create;
 end;
 
@@ -66,7 +66,7 @@ destructor tspecializationcontext.destroy;
 var
   i : longint;
 begin
-  genericdeflist.free;
+  paramlist.free;
   for i:=0 to poslist.count-1 do
     dispose(pfileposinfo(poslist[i]));
   poslist.free;
diff --git a/compiler/pgenutil.pas b/compiler/pgenutil.pas
index 7760a4e134..33daf3b06a 100644
--- a/compiler/pgenutil.pas
+++ b/compiler/pgenutil.pas
@@ -42,9 +42,9 @@ uses
     function generate_specialization_phase1(out context:tspecializationcontext;genericdef:tdef;symname:string):tdef;inline;
     function generate_specialization_phase1(out context:tspecializationcontext;genericdef:tdef;parsedtype:tdef;symname:string;parsedpos:tfileposinfo):tdef;
     function generate_specialization_phase2(context:tspecializationcontext;genericdef:tstoreddef;parse_class_parent:boolean;_prettyname:ansistring):tdef;
-    function check_generic_constraints(genericdef:tstoreddef;paradeflist:tfpobjectlist;poslist:tfplist):boolean;
+    function check_generic_constraints(genericdef:tstoreddef;paramlist:tfpobjectlist;poslist:tfplist):boolean;
     function parse_generic_parameters(allowconstraints:boolean):tfphashobjectlist;
-    function parse_generic_specialization_types(genericdeflist:tfpobjectlist;poslist:tfplist;out prettyname,specializename:ansistring):boolean;
+    function parse_generic_specialization_types(paramlist:tfpobjectlist;poslist:tfplist;out prettyname,specializename:ansistring):boolean;
     procedure insert_generic_parameter_types(def:tstoreddef;genericdef:tstoreddef;genericlist:tfphashobjectlist);
     procedure maybe_insert_generic_rename_symbol(const name:tidstring;genericlist:tfphashobjectlist);
     function generate_generic_name(const name:tidstring;specializename:ansistring;owner_hierarchy:string):tidstring;
@@ -63,18 +63,163 @@ implementation
 
 uses
   { common }
-  cutils,fpccrc,
+  sysutils,cutils,fpccrc,
   { global }
-  globals,tokens,verbose,finput,
+  globals,tokens,verbose,finput,constexp,
   { symtable }
-  symconst,symsym,symtable,defcmp,procinfo,
+  symconst,symsym,symtable,defcmp,defutil,procinfo,
   { modules }
   fmodule,
-  node,nobj,
+  node,nobj,ncon,
   { parser }
   scanner,
   pbase,pexpr,pdecsub,ptype,psub;
 
+  type
+    tdeftypeset = set of tdeftyp;
+  const
+    tgeneric_param_const_types:tdeftypeset = [orddef,stringdef,arraydef,floatdef,setdef,pointerdef,undefineddef];
+    tgeneric_param_nodes: tnodetypeset = [typen,ordconstn,stringconstn,realconstn,setconstn,niln];
+
+    function get_generic_param_def(sym:tsym):tdef;
+      begin
+        if sym.typ = constsym then
+          result := tconstsym(sym).constdef
+        else
+          result := ttypesym(sym).typedef;
+      end;
+
+    function is_generic_param_const(sym:tsym):boolean;
+      begin
+        if sym.typ = constsym then
+          result := tconstsym(sym).consttyp<>constundefined
+        else
+          result := false;
+      end;
+
+    function compare_orddef_by_range(param1,param2:torddef;value:tconstvalue): boolean;
+      begin
+        if (value.len<param2.low) or (value.len>param2.high) then
+          result:=false
+        else
+          result:=true;
+      end;
+
+    function compare_generic_params(param1,param2:tdef;constparamsym:tconstsym):boolean;
+      begin
+        if (param1.typ=orddef) and (param2.typ=orddef) then
+          begin
+            if is_boolean(param2) then
+              result:=is_boolean(param1)
+            else if is_char(param2) then
+              result:=is_char(param1)
+            else if compare_orddef_by_range(torddef(param1),torddef(param2),constparamsym.value) then
+              result:=true
+            else
+              result:=false;
+          end
+        { arraydef is string constant so it's compatible with stringdef }
+        else if (param1.typ=arraydef) and (param2.typ=stringdef) then
+          result:=true
+        { integer ords are compatible with float }
+        else if (param1.typ=orddef) and is_integer(param1) and (param2.typ=floatdef) then
+          result:=true
+        { undefined def is compatible with all types }
+        else if param2.typ=undefineddef then
+          result:=true
+        { sets require stricter checks }
+        else if is_set(param2) then
+          result:=equal_defs(param1,param2)
+        else
+          result:=param1.typ=param2.typ;
+      end;
+
+    function create_generic_constsym(fromdef:tdef;node:tnode;out prettyname:string):tconstsym;
+      const
+        undefinedname = 'undefined';
+      var
+        sym : tconstsym;
+        setdef : tsetdef;
+        enumsym : tsym;
+        enumname : string;
+        sp : pchar;
+        ps : ^tconstset;
+        pd : ^bestreal;
+        i : integer;
+      begin
+        if node = nil then
+          begin
+            sym:=cconstsym.create_undefined(undefinedname,fromdef);
+            sym.owner:=fromdef.owner;
+            prettyname:='';
+            result:=sym;
+            exit;
+          end;
+        case node.nodetype of
+          ordconstn:
+            begin
+              sym:=cconstsym.create_ord(undefinedname,constord,tordconstnode(node).value,fromdef);
+              prettyname:=inttostr(tordconstnode(node).value.svalue);
+            end;
+          stringconstn:
+            begin
+              getmem(sp,tstringconstnode(node).len+1);
+              move(tstringconstnode(node).value_str^,sp^,tstringconstnode(node).len+1);
+              sym:=cconstsym.create_string(undefinedname,conststring,sp,tstringconstnode(node).len,fromdef);
+              prettyname:=''''+tstringconstnode(node).value_str+'''';
+            end;
+          realconstn:
+            begin
+              new(pd);
+              pd^:=trealconstnode(node).value_real;
+              sym:=cconstsym.create_ptr(undefinedname,constreal,pd,fromdef);
+              prettyname:=floattostr(trealconstnode(node).value_real);
+            end;
+          setconstn:
+            begin
+              new(ps);
+              ps^:=tsetconstnode(node).value_set^;
+              sym:=cconstsym.create_ptr(undefinedname,constset,ps,fromdef);
+              setdef:=tsetdef(tsetconstnode(node).resultdef);
+              prettyname:='[';
+              for i := setdef.setbase to setdef.setmax do
+                if i in tsetconstnode(node).value_set^ then
+                  begin
+                    if setdef.elementdef.typ=enumdef then
+                      enumsym:=tenumdef(setdef.elementdef).int2enumsym(i)
+                    else
+                      enumsym:=nil;
+                    if assigned(enumsym) then
+                      enumname:=enumsym.realname
+                    else if setdef.elementdef.typ=orddef then
+                      begin
+                        if torddef(setdef.elementdef).ordtype=uchar then
+                          enumname:=chr(i)
+                        else
+                          enumname:=tostr(i);
+                      end
+                    else
+                      enumname:=tostr(i);
+                    if length(prettyname) > 1 then
+                      prettyname:=prettyname+','+enumname
+                    else
+                      prettyname:=prettyname+enumname;
+                  end;
+              prettyname:=prettyname+']';
+            end;
+          niln:
+            begin
+              { only "nil" is available for pointer constants }
+              sym:=cconstsym.create_ord(undefinedname,constnil,0,fromdef);
+              prettyname:='nil';
+            end;
+          else
+            internalerror(2019021601);
+        end;
+        { the sym needs an owner for later checks so us the typeparam owner }
+        sym.owner:=fromdef.owner;
+        result:=sym;
+      end;
 
     procedure maybe_add_waiting_unit(tt:tdef);
       var
@@ -104,203 +249,232 @@ uses
           end;
       end;
 
-    function check_generic_constraints(genericdef:tstoreddef;paradeflist:tfpobjectlist;poslist:tfplist):boolean;
+    function check_generic_constraints(genericdef:tstoreddef;paramlist:tfpobjectlist;poslist:tfplist):boolean;
       var
         i,j,
         intfcount : longint;
         formaldef,
         paradef : tstoreddef;
+        genparadef : tdef;
         objdef,
         paraobjdef,
         formalobjdef : tobjectdef;
         intffound : boolean;
         filepos : tfileposinfo;
+        //paratype : tconsttyp;
+        is_const : boolean;
       begin
         { check whether the given specialization parameters fit to the eventual
           constraints of the generic }
         if not assigned(genericdef.genericparas) or (genericdef.genericparas.count=0) then
           internalerror(2012101001);
-        if genericdef.genericparas.count<>paradeflist.count then
+        if genericdef.genericparas.count<>paramlist.count then
           internalerror(2012101002);
-        if paradeflist.count<>poslist.count then
+        if paramlist.count<>poslist.count then
           internalerror(2012120801);
         result:=true;
         for i:=0 to genericdef.genericparas.count-1 do
           begin
             filepos:=pfileposinfo(poslist[i])^;
-            formaldef:=tstoreddef(ttypesym(genericdef.genericparas[i]).typedef);
-            if formaldef.typ=undefineddef then
-              { the parameter is of unspecified type, so no need to check }
-              continue;
-            if not (df_genconstraint in formaldef.defoptions) or
-                not assigned(formaldef.genconstraintdata) then
-              internalerror(2013021602);
-            paradef:=tstoreddef(paradeflist[i]);
-            { undefineddef is compatible with anything }
-            if formaldef.typ=undefineddef then
-              continue;
-            if paradef.typ<>formaldef.typ then
+            paradef:=tstoreddef(get_generic_param_def(tsym(paramlist[i])));
+            is_const:=is_generic_param_const(tsym(paramlist[i]));
+            genparadef:=genericdef.get_generic_param_def(i);
+            { validate const params }
+            if not genericdef.is_generic_param_const(i) and is_const then
               begin
-                case formaldef.typ of
-                  recorddef:
-                    { delphi has own fantasy about record constraint
-                      (almost non-nullable/non-nilable value type) }
-                    if m_delphi in current_settings.modeswitches then
-                      case paradef.typ of
-                        floatdef,enumdef,orddef:
-                          continue;
-                        objectdef:
-                          if tobjectdef(paradef).objecttype=odt_object then
-                            continue
-                          else
-                            MessagePos(filepos,type_e_record_type_expected);
+                MessagePos(filepos,type_e_mismatch);
+                exit(false);
+              end
+            else if genericdef.is_generic_param_const(i) then
+              begin
+                { param type mismatch (type <> const) }
+                 if genericdef.is_generic_param_const(i) <> is_const then
+                   begin
+                    MessagePos(filepos,type_e_mismatch);
+                    exit(false);
+                  end;
+                { type constrained param doesn't match type }
+                if not compare_generic_params(paradef,genericdef.get_generic_param_def(i),tconstsym(paramlist[i])) then
+                  begin
+                    MessagePos2(filepos,type_e_incompatible_types,FullTypeName(paradef,genparadef),FullTypeName(genparadef,paradef));
+                    exit(false);
+                  end;
+              end;
+            { test constraints for non-const params }
+            if not genericdef.is_generic_param_const(i) then
+              begin
+                formaldef:=tstoreddef(ttypesym(genericdef.genericparas[i]).typedef);
+                if formaldef.typ=undefineddef then
+                  { the parameter is of unspecified type, so no need to check }
+                  continue;
+                if not (df_genconstraint in formaldef.defoptions) or
+                    not assigned(formaldef.genconstraintdata) then
+                  internalerror(2013021602);
+                { undefineddef is compatible with anything }
+                if formaldef.typ=undefineddef then
+                  continue;
+                if paradef.typ<>formaldef.typ then
+                  begin
+                    case formaldef.typ of
+                      recorddef:
+                        { delphi has own fantasy about record constraint
+                          (almost non-nullable/non-nilable value type) }
+                        if m_delphi in current_settings.modeswitches then
+                          case paradef.typ of
+                            floatdef,enumdef,orddef:
+                              continue;
+                            objectdef:
+                              if tobjectdef(paradef).objecttype=odt_object then
+                                continue
+                              else
+                                MessagePos(filepos,type_e_record_type_expected);
+                            else
+                              MessagePos(filepos,type_e_record_type_expected);
+                          end
                         else
                           MessagePos(filepos,type_e_record_type_expected);
-                      end
-                    else
-                      MessagePos(filepos,type_e_record_type_expected);
-                  objectdef:
-                    case tobjectdef(formaldef).objecttype of
-                      odt_class,
-                      odt_javaclass:
-                        MessagePos1(filepos,type_e_class_type_expected,paradef.typename);
-                      odt_interfacecom,
-                      odt_interfacecorba,
-                      odt_dispinterface,
-                      odt_interfacejava:
-                        MessagePos1(filepos,type_e_interface_type_expected,paradef.typename);
+                      objectdef:
+                        case tobjectdef(formaldef).objecttype of
+                          odt_class,
+                          odt_javaclass:
+                            MessagePos1(filepos,type_e_class_type_expected,paradef.typename);
+                          odt_interfacecom,
+                          odt_interfacecorba,
+                          odt_dispinterface,
+                          odt_interfacejava:
+                            MessagePos1(filepos,type_e_interface_type_expected,paradef.typename);
+                          else
+                            internalerror(2012101003);
+                        end;
+                      errordef:
+                        { ignore }
+                        ;
                       else
-                        internalerror(2012101003);
+                        internalerror(2012101004);
                     end;
-                  errordef:
-                    { ignore }
-                    ;
-                  else
-                    internalerror(2012101004);
-                end;
-                result:=false;
-              end
-            else
-              begin
-                { the paradef types are the same, so do special checks for the
-                  cases in which they are needed }
-                if formaldef.typ=objectdef then
+                    result:=false;
+                  end
+                else
                   begin
-                    paraobjdef:=tobjectdef(paradef);
-                    formalobjdef:=tobjectdef(formaldef);
-                    if not (formalobjdef.objecttype in [odt_class,odt_javaclass,odt_interfacecom,odt_interfacecorba,odt_interfacejava,odt_dispinterface]) then
-                      internalerror(2012101102);
-                    if formalobjdef.objecttype in [odt_interfacecom,odt_interfacecorba,odt_interfacejava,odt_dispinterface] then
+                    { the paradef types are the same, so do special checks for the
+                      cases in which they are needed }
+                    if formaldef.typ=objectdef then
                       begin
-                        { this is either a concerete interface or class type (the
-                          latter without specific implemented interfaces) }
-                        case paraobjdef.objecttype of
-                          odt_interfacecom,
-                          odt_interfacecorba,
-                          odt_interfacejava,
-                          odt_dispinterface:
-                            begin
-                              if (oo_is_forward in paraobjdef.objectoptions) and
-                                  (paraobjdef.objecttype=formalobjdef.objecttype) and
-                                  (df_genconstraint in formalobjdef.defoptions) and
-                                  (
-                                    (formalobjdef.objecttype=odt_interfacecom) and
-                                    (formalobjdef.childof=interface_iunknown)
-                                  )
-                                  or
-                                  (
-                                    (formalobjdef.objecttype=odt_interfacecorba) and
-                                    (formalobjdef.childof=nil)
-                                  ) then
-                                continue;
-                              if not def_is_related(paraobjdef,formalobjdef.childof) then
+                        paraobjdef:=tobjectdef(paradef);
+                        formalobjdef:=tobjectdef(formaldef);
+                        if not (formalobjdef.objecttype in [odt_class,odt_javaclass,odt_interfacecom,odt_interfacecorba,odt_interfacejava,odt_dispinterface]) then
+                          internalerror(2012101102);
+                        if formalobjdef.objecttype in [odt_interfacecom,odt_interfacecorba,odt_interfacejava,odt_dispinterface] then
+                          begin
+                            { this is either a concerete interface or class type (the
+                              latter without specific implemented interfaces) }
+                            case paraobjdef.objecttype of
+                              odt_interfacecom,
+                              odt_interfacecorba,
+                              odt_interfacejava,
+                              odt_dispinterface:
                                 begin
-                                  MessagePos2(filepos,type_e_incompatible_types,paraobjdef.typename,formalobjdef.childof.typename);
-                                  result:=false;
+                                  if (oo_is_forward in paraobjdef.objectoptions) and
+                                      (paraobjdef.objecttype=formalobjdef.objecttype) and
+                                      (df_genconstraint in formalobjdef.defoptions) and
+                                      (
+                                        (formalobjdef.objecttype=odt_interfacecom) and
+                                        (formalobjdef.childof=interface_iunknown)
+                                      )
+                                      or
+                                      (
+                                        (formalobjdef.objecttype=odt_interfacecorba) and
+                                        (formalobjdef.childof=nil)
+                                      ) then
+                                    continue;
+                                  if not def_is_related(paraobjdef,formalobjdef.childof) then
+                                    begin
+                                      MessagePos2(filepos,type_e_incompatible_types,paraobjdef.typename,formalobjdef.childof.typename);
+                                      result:=false;
+                                    end;
                                 end;
-                            end;
-                          odt_class,
-                          odt_javaclass:
-                            begin
-                              objdef:=paraobjdef;
-                              intffound:=false;
-                              while assigned(objdef) do
+                              odt_class,
+                              odt_javaclass:
                                 begin
-                                  for j:=0 to objdef.implementedinterfaces.count-1 do
-                                    if timplementedinterface(objdef.implementedinterfaces[j]).intfdef=formalobjdef.childof then
-                                      begin
-                                        intffound:=true;
+                                  objdef:=paraobjdef;
+                                  intffound:=false;
+                                  while assigned(objdef) do
+                                    begin
+                                      for j:=0 to objdef.implementedinterfaces.count-1 do
+                                        if timplementedinterface(objdef.implementedinterfaces[j]).intfdef=formalobjdef.childof then
+                                          begin
+                                            intffound:=true;
+                                            break;
+                                          end;
+                                      if intffound then
                                         break;
-                                      end;
-                                  if intffound then
-                                    break;
-                                  objdef:=objdef.childof;
+                                      objdef:=objdef.childof;
+                                    end;
+                                  result:=intffound;
+                                  if not result then
+                                    MessagePos2(filepos,parser_e_class_doesnt_implement_interface,paraobjdef.typename,formalobjdef.childof.typename);
+                                end;
+                              else
+                                begin
+                                  MessagePos1(filepos,type_e_class_or_interface_type_expected,paraobjdef.typename);
+                                  result:=false;
                                 end;
-                              result:=intffound;
-                              if not result then
-                                MessagePos2(filepos,parser_e_class_doesnt_implement_interface,paraobjdef.typename,formalobjdef.childof.typename);
-                            end;
-                          else
-                            begin
-                              MessagePos1(filepos,type_e_class_or_interface_type_expected,paraobjdef.typename);
-                              result:=false;
                             end;
-                        end;
-                      end
-                    else
-                      begin
-                        { this is either a "class" or a concrete instance with
-                          or without implemented interfaces }
-                        if not (paraobjdef.objecttype in [odt_class,odt_javaclass]) then
-                          begin
-                            MessagePos1(filepos,type_e_class_type_expected,paraobjdef.typename);
-                            result:=false;
-                            continue;
-                          end;
-                        { for forward declared classes we allow pure TObject/class declarations }
-                        if (oo_is_forward in paraobjdef.objectoptions) and
-                            (df_genconstraint in formaldef.defoptions) then
-                          begin
-                            if (formalobjdef.childof=class_tobject) and
-                                not formalobjdef.implements_any_interfaces then
-                              continue;
-                          end;
-                        if assigned(formalobjdef.childof) and
-                            not def_is_related(paradef,formalobjdef.childof) then
-                          begin
-                            MessagePos2(filepos,type_e_incompatible_types,paraobjdef.typename,formalobjdef.childof.typename);
-                            result:=false;
-                          end;
-                        intfcount:=0;
-                        for j:=0 to formalobjdef.implementedinterfaces.count-1 do
+                          end
+                        else
                           begin
-                            objdef:=paraobjdef;
-                            while assigned(objdef) do
+                            { this is either a "class" or a concrete instance with
+                              or without implemented interfaces }
+                            if not (paraobjdef.objecttype in [odt_class,odt_javaclass]) then
                               begin
-                                intffound:=assigned(
-                                             find_implemented_interface(objdef,
-                                               timplementedinterface(formalobjdef.implementedinterfaces[j]).intfdef
-                                             )
-                                           );
+                                MessagePos1(filepos,type_e_class_type_expected,paraobjdef.typename);
+                                result:=false;
+                                continue;
+                              end;
+                            { for forward declared classes we allow pure TObject/class declarations }
+                            if (oo_is_forward in paraobjdef.objectoptions) and
+                                (df_genconstraint in formaldef.defoptions) then
+                              begin
+                                if (formalobjdef.childof=class_tobject) and
+                                    not formalobjdef.implements_any_interfaces then
+                                  continue;
+                              end;
+                            if assigned(formalobjdef.childof) and
+                                not def_is_related(paradef,formalobjdef.childof) then
+                              begin
+                                MessagePos2(filepos,type_e_incompatible_types,paraobjdef.typename,formalobjdef.childof.typename);
+                                result:=false;
+                              end;
+                            intfcount:=0;
+                            for j:=0 to formalobjdef.implementedinterfaces.count-1 do
+                              begin
+                                objdef:=paraobjdef;
+                                while assigned(objdef) do
+                                  begin
+                                    intffound:=assigned(
+                                                 find_implemented_interface(objdef,
+                                                   timplementedinterface(formalobjdef.implementedinterfaces[j]).intfdef
+                                                 )
+                                               );
+                                    if intffound then
+                                      break;
+                                    objdef:=objdef.childof;
+                                  end;
                                 if intffound then
-                                  break;
-                                objdef:=objdef.childof;
+                                  inc(intfcount)
+                                else
+                                  MessagePos2(filepos,parser_e_class_doesnt_implement_interface,paraobjdef.typename,timplementedinterface(formalobjdef.implementedinterfaces[j]).intfdef.typename);
                               end;
-                            if intffound then
-                              inc(intfcount)
-                            else
-                              MessagePos2(filepos,parser_e_class_doesnt_implement_interface,paraobjdef.typename,timplementedinterface(formalobjdef.implementedinterfaces[j]).intfdef.typename);
+                            if intfcount<>formalobjdef.implementedinterfaces.count then
+                              result:=false;
                           end;
-                        if intfcount<>formalobjdef.implementedinterfaces.count then
-                          result:=false;
                       end;
                   end;
               end;
           end;
       end;
 
-
-    function parse_generic_specialization_types_internal(genericdeflist:tfpobjectlist;poslist:tfplist;out prettyname,specializename:ansistring;parsedtype:tdef;parsedpos:tfileposinfo):boolean;
+    function parse_generic_specialization_types_internal(paramlist:tfpobjectlist;poslist:tfplist;out prettyname,specializename:ansistring;parsedtype:tdef;parsedpos:tfileposinfo):boolean;
       var
         old_block_type : tblock_type;
         first : boolean;
@@ -310,9 +484,12 @@ uses
         namepart : string;
         prettynamepart : ansistring;
         module : tmodule;
+        //paramdef : tgenericparamdef;
+        constprettyname : string;
+        validparam : boolean;
       begin
         result:=true;
-        if genericdeflist=nil then
+        if paramlist=nil then
           internalerror(2012061401);
         { set the block type to type, so that the parsed type are returned as
           ttypenode (e.g. classes are in non type-compatible blocks returned as
@@ -324,7 +501,7 @@ uses
         first:=not assigned(parsedtype);
         if assigned(parsedtype) then
           begin
-            genericdeflist.Add(parsedtype);
+            paramlist.Add(parsedtype.typesym);
             module:=find_module_from_symtable(parsedtype.owner);
             if not assigned(module) then
               internalerror(2016112801);
@@ -351,7 +528,9 @@ uses
             block_type:=bt_type;
             tmpparampos:=current_filepos;
             typeparam:=factor(false,[ef_type_only]);
-            if typeparam.nodetype=typen then
+            { determine if the typeparam node is a valid type or const }
+            validparam:=typeparam.nodetype in tgeneric_param_nodes;
+            if validparam then
               begin
                 if tstoreddef(typeparam.resultdef).is_generic and
                     (
@@ -367,31 +546,47 @@ uses
                   end;
                 if typeparam.resultdef.typ<>errordef then
                   begin
-                    if not assigned(typeparam.resultdef.typesym) then
+                    if (typeparam.nodetype = typen) and not assigned(typeparam.resultdef.typesym) then
                       message(type_e_generics_cannot_reference_itself)
-                    else if (typeparam.resultdef.typ<>errordef) then
+                    else 
+                    if (typeparam.resultdef.typ<>errordef) then
                       begin
-                        genericdeflist.Add(typeparam.resultdef);
+                        { all non-type nodes are considered const }
+                        if typeparam.nodetype <> typen then
+                          paramlist.Add(create_generic_constsym(typeparam.resultdef,typeparam,constprettyname))
+                        else
+                          begin
+                            constprettyname:='';
+                            paramlist.Add(typeparam.resultdef.typesym);
+                          end;
                         module:=find_module_from_symtable(typeparam.resultdef.owner);
                         if not assigned(module) then
                           internalerror(2016112802);
                         namepart:='_$'+hexstr(module.moduleid,8)+'$$'+typeparam.resultdef.unique_id_str;
+                        if constprettyname <> '' then
+                          namepart:=namepart+'$$'+constprettyname;
                         { we use the full name of the type to uniquely identify it }
-                        if (symtablestack.top.symtabletype=parasymtable) and
-                            (symtablestack.top.defowner.typ=procdef) and
-                            (typeparam.resultdef.owner=symtablestack.top) then
-                          begin
-                            { special handling for specializations inside generic function declarations }
-                            prettynamepart:=tdef(symtablestack.top.defowner).fullownerhierarchyname(true)+tprocdef(symtablestack.top.defowner).procsym.prettyname;
-                          end
-                        else
+                        if typeparam.nodetype = typen then
                           begin
-                            prettynamepart:=typeparam.resultdef.fullownerhierarchyname(true);
+                            if (symtablestack.top.symtabletype=parasymtable) and
+                                (symtablestack.top.defowner.typ=procdef) and
+                                (typeparam.resultdef.owner=symtablestack.top) then
+                              begin
+                                { special handling for specializations inside generic function declarations }
+                                prettynamepart:=tdef(symtablestack.top.defowner).fullownerhierarchyname(true)+tprocdef(symtablestack.top.defowner).procsym.prettyname;
+                              end
+                            else
+                              begin
+                                prettynamepart:=typeparam.resultdef.fullownerhierarchyname(true);
+                              end;
                           end;
                         specializename:=specializename+namepart;
                         if not first then
                           prettyname:=prettyname+',';
-                        prettyname:=prettyname+prettynamepart+typeparam.resultdef.typesym.prettyname;
+                        if constprettyname <> '' then
+                          prettyname:=prettyname+constprettyname
+                        else
+                          prettyname:=prettyname+prettynamepart+typeparam.resultdef.typesym.prettyname;
                       end;
                   end
                 else
@@ -411,12 +606,12 @@ uses
       end;
 
 
-    function parse_generic_specialization_types(genericdeflist:tfpobjectlist;poslist:tfplist;out prettyname,specializename:ansistring):boolean;
+    function parse_generic_specialization_types(paramlist:tfpobjectlist;poslist:tfplist;out prettyname,specializename:ansistring):boolean;
       var
         dummypos : tfileposinfo;
       begin
         FillChar(dummypos, SizeOf(tfileposinfo), 0);
-        result:=parse_generic_specialization_types_internal(genericdeflist,poslist,prettyname,specializename,nil,dummypos);
+        result:=parse_generic_specialization_types_internal(paramlist,poslist,prettyname,specializename,nil,dummypos);
       end;
 
 
@@ -578,7 +773,7 @@ uses
         context:=tspecializationcontext.create;
 
         { Parse type parameters }
-        err:=not parse_generic_specialization_types_internal(context.genericdeflist,context.poslist,context.prettyname,context.specializename,parsedtype,parsedpos);
+        err:=not parse_generic_specialization_types_internal(context.paramlist,context.poslist,context.prettyname,context.specializename,parsedtype,parsedpos);
         if err then
           begin
             if not try_to_consume(_GT) then
@@ -627,7 +822,7 @@ uses
 
         { search a generic with the given count of params }
         countstr:='';
-        str(context.genericdeflist.Count,countstr);
+        str(context.paramlist.Count,countstr);
 
         genname:=genname+'$'+countstr;
         ugenname:=upper(genname);
@@ -656,7 +851,7 @@ uses
             result:=generrordef;
             exit;
           end;
-
+        
         { we've found the correct def }
         if context.sym.typ=typesym then
           result:=tstoreddef(ttypesym(context.sym).typedef)
@@ -747,6 +942,7 @@ uses
         hintsprocessed : boolean;
         pd : tprocdef;
         pdflags : tpdflags;
+        typedef : tstoreddef;
       begin
         if not assigned(context) then
           internalerror(2015052203);
@@ -755,7 +951,7 @@ uses
 
         pd:=nil;
 
-        if not check_generic_constraints(genericdef,context.genericdeflist,context.poslist) then
+        if not check_generic_constraints(genericdef,context.paramlist,context.poslist) then
           begin
             { the parameters didn't fit the constraints, so don't continue with the
               specialization }
@@ -771,20 +967,19 @@ uses
         else
           prettyname:=genericdef.typesym.prettyname;
         prettyname:=prettyname+'<'+context.prettyname+'>';
-
         generictypelist:=tfphashobjectlist.create(false);
 
         { build the list containing the types for the generic params }
         if not assigned(genericdef.genericparas) then
           internalerror(2013092601);
-        if context.genericdeflist.count<>genericdef.genericparas.count then
+        if context.paramlist.count<>genericdef.genericparas.count then
           internalerror(2013092603);
         for i:=0 to genericdef.genericparas.Count-1 do
           begin
             srsym:=tsym(genericdef.genericparas[i]);
             if not (sp_generic_para in srsym.symoptions) then
               internalerror(2013092602);
-            generictypelist.add(srsym.realname,tdef(context.genericdeflist[i]).typesym);
+            generictypelist.add(srsym.realname,context.paramlist[i]);
           end;
 
         { Special case if we are referencing the current defined object }
@@ -1196,8 +1391,8 @@ uses
 
     function parse_generic_parameters(allowconstraints:boolean):tfphashobjectlist;
       var
-        generictype : ttypesym;
-        i,firstidx : longint;
+        generictype : tstoredsym;
+        i,firstidx,const_list_index : longint;
         srsymtable : tsymtable;
         basedef,def : tdef;
         defname : tidstring;
@@ -1205,22 +1400,87 @@ uses
         doconsume : boolean;
         constraintdata : tgenericconstraintdata;
         old_block_type : tblock_type;
+        is_const,last_is_const : boolean;
+        last_token : ttoken;
+        last_type_pos : tfileposinfo;
       begin
         result:=tfphashobjectlist.create(false);
         firstidx:=0;
+        const_list_index:=0;
         old_block_type:=block_type;
         block_type:=bt_type;
+        is_const:=false;
+        last_is_const:=false;
+        last_token:=NOTOKEN;
         repeat
+          if try_to_consume(_CONST) then
+            begin
+              { last param was const without semicolon terminator }
+              if (result.count>0) and last_is_const and (last_token<>_SEMICOLON) then
+                MessagePos2(last_type_pos,scan_f_syn_expected,arraytokeninfo[_SEMICOLON].str,arraytokeninfo[last_token].str);
+              is_const := true;
+              const_list_index := result.count;
+            end;
           if token=_ID then
             begin
-              generictype:=ctypesym.create(orgpattern,cundefinedtype,false);
+              if is_const then
+                begin
+                  { last param was type without semicolon terminator }
+                  if (result.count>0) and not last_is_const and (last_token<>_SEMICOLON) then
+                    MessagePos2(last_type_pos,scan_f_syn_expected,arraytokeninfo[_SEMICOLON].str,arraytokeninfo[last_token].str);
+                  generictype:=tconstsym.create_undefined(orgpattern,cundefinedtype);
+                end
+              else
+                begin
+                  { last param was const without semicolon terminator }
+                  if (result.count>0) and last_is_const and (last_token<>_SEMICOLON) then
+                    MessagePos2(last_type_pos,scan_f_syn_expected,arraytokeninfo[_SEMICOLON].str,arraytokeninfo[last_token].str);
+                  generictype:=ttypesym.create(orgpattern,cundefinedtype,false);
+                end;
               { type parameters need to be added as strict private }
               generictype.visibility:=vis_strictprivate;
               include(generictype.symoptions,sp_generic_para);
               result.add(orgpattern,generictype);
+              last_is_const:=is_const;
             end;
           consume(_ID);
-          if try_to_consume(_COLON) then
+          { const restriction }
+          if is_const then
+            begin
+              if try_to_consume(_COLON) then
+                begin
+                  def := nil;
+                  { parse the type and assign the const type to generictype  }
+                  single_type(def,[]);
+                  for i:=const_list_index to result.count-1 do
+                    begin
+                      { finalize constant information once type is known }
+                      if assigned(def) and (def.typ in tgeneric_param_const_types) then
+                        begin
+                          case def.typ of
+                            orddef:
+                              tconstsym(result[i]).consttyp:=constord;
+                            stringdef:
+                              tconstsym(result[i]).consttyp:=conststring;
+                            floatdef:
+                              tconstsym(result[i]).consttyp:=constreal;
+                            setdef:
+                              tconstsym(result[i]).consttyp:=constset;
+                            { pointer always refers to nil with constants }
+                            pointerdef:
+                              tconstsym(result[i]).consttyp:=constnil;
+                          end;
+                          tconstsym(result[i]).constdef:=def;
+                        end
+                      else
+                        Message(type_e_mismatch);
+                    end;
+                  { after type restriction const list terminates }
+                  is_const:=false;
+                end;
+            end
+          { type restriction }
+          else if try_to_consume(_COLON) then
             begin
               if not allowconstraints then
                 { TODO }
@@ -1335,6 +1595,7 @@ uses
                     basedef:=cobjectdef.create(tobjectdef(def).objecttype,defname,tobjectdef(def),false);
                     constraintdata.interfaces.delete(0);
                   end;
+
               if basedef.typ<>errordef then
                 with tstoreddef(basedef) do
                   begin
@@ -1360,21 +1621,27 @@ uses
                 begin
                   { two different typeless parameters are considered as incompatible }
                   for i:=firstidx to result.count-1 do
-                    begin
-                      ttypesym(result[i]).typedef:=cundefineddef.create(false);
-                      ttypesym(result[i]).typedef.typesym:=ttypesym(result[i]);
-                    end;
+                    if tsym(result[i]).typ<>constsym then
+                      begin
+                        ttypesym(result[i]).typedef:=cundefineddef.create(false);
+                        ttypesym(result[i]).typedef.typesym:=ttypesym(result[i]);
+                      end;
                   { a semicolon terminates a type parameter group }
                   firstidx:=result.count;
                 end;
             end;
+          if token = _SEMICOLON then
+            is_const:=false;
+          last_token:=token;
+          last_type_pos:=current_filepos;
         until not (try_to_consume(_COMMA) or try_to_consume(_SEMICOLON));
         { two different typeless parameters are considered as incompatible }
         for i:=firstidx to result.count-1 do
-          begin
-            ttypesym(result[i]).typedef:=cundefineddef.create(false);
-            ttypesym(result[i]).typedef.typesym:=ttypesym(result[i]);
-          end;
+          if tsym(result[i]).typ<>constsym then
+            begin
+              ttypesym(result[i]).typedef:=cundefineddef.create(false);
+              ttypesym(result[i]).typedef.typesym:=ttypesym(result[i]);
+            end;
         block_type:=old_block_type;
       end;
 
@@ -1382,7 +1649,9 @@ uses
     procedure insert_generic_parameter_types(def:tstoreddef;genericdef:tstoreddef;genericlist:tfphashobjectlist);
       var
         i : longint;
-        generictype,sym : ttypesym;
+        generictype : tstoredsym;
+        generictypedef : tdef;
+        sym : tsym;
         st : tsymtable;
       begin
         def.genericdef:=genericdef;
@@ -1407,10 +1676,22 @@ uses
           def.genericparas:=tfphashobjectlist.create(false);
         for i:=0 to genericlist.count-1 do
           begin
-            generictype:=ttypesym(genericlist[i]);
+            generictype:=tstoredsym(genericlist[i]);
             if assigned(generictype.owner) then
               begin
-                sym:=ctypesym.create(genericlist.nameofindex(i),generictype.typedef,true);
+                if generictype.typ=typesym then
+                  sym:=ctypesym.create(genericlist.nameofindex(i),ttypesym(generictype).typedef,true)
+                else if generictype.typ=constsym then
+                  { generictype is a constsym that was created in create_generic_constsym 
+                    during phase 1 so we pass this directly without copying }
+                  begin
+                    sym:=generictype;
+                    { the sym name is still undefined so we set it to match
+                      the generic param name so it's accessible }
+                    sym.realname:=genericlist.nameofindex(i);
+                  end
+                else
+                  internalerror(2019021602);
                 { type parameters need to be added as strict private }
                 sym.visibility:=vis_strictprivate;
                 st.insert(sym);
@@ -1418,13 +1699,17 @@ uses
               end
             else
               begin
-                if (generictype.typedef.typ=undefineddef) and (generictype.typedef<>cundefinedtype) then
+                if generictype.typ=typesym then
                   begin
-                    { the generic parameters were parsed before the genericdef existed thus the
-                      undefineddefs were added as part of the parent symtable }
-                    if assigned(generictype.typedef.owner) then
-                      generictype.typedef.owner.DefList.Extract(generictype.typedef);
-                    generictype.typedef.changeowner(st);
+                    generictypedef:=ttypesym(generictype).typedef;
+                    if (generictypedef.typ=undefineddef) and (generictypedef<>cundefinedtype) then
+                      begin
+                        { the generic parameters were parsed before the genericdef existed thus the
+                          undefineddefs were added as part of the parent symtable }
+                        if assigned(generictypedef.owner) then
+                          generictypedef.owner.DefList.Extract(generictypedef);
+                        generictypedef.changeowner(st);
+                      end;
                   end;
                 st.insert(generictype);
                 include(generictype.symoptions,sp_generic_para);
diff --git a/compiler/ppu.pas b/compiler/ppu.pas
index 10c42e7eb8..31011be3e8 100644
--- a/compiler/ppu.pas
+++ b/compiler/ppu.pas
@@ -43,7 +43,7 @@ type
 {$endif Test_Double_checksum}
 
 const
-  CurrentPPUVersion = 201;
+  CurrentPPUVersion = 203;
 
 { unit flags }
   uf_init                = $000001; { unit has initialization section }
diff --git a/compiler/ptype.pas b/compiler/ptype.pas
index 38e2526e9f..28cd0f94f8 100644
--- a/compiler/ptype.pas
+++ b/compiler/ptype.pas
@@ -1436,7 +1436,9 @@ implementation
                                  highval:=tordconstnode(trangenode(pt).right).value;
                                  if highval<lowval then
                                   begin
-                                    Message(parser_e_array_lower_less_than_upper_bound);
+                                    { ignore error if node is generic param }
+                                    if not (nf_generic_para in pt.flags) then
+                                      Message(parser_e_array_lower_less_than_upper_bound);
                                     highval:=lowval;
                                   end
                                  else if (lowval<int64(low(asizeint))) or
diff --git a/compiler/symconst.pas b/compiler/symconst.pas
index a5ae7e0fb9..e02ce3a8ca 100644
--- a/compiler/symconst.pas
+++ b/compiler/symconst.pas
@@ -232,7 +232,10 @@ type
       because we have to access this information in the symtable unit }
     df_llvm_no_struct_packing,
     { internal def that's not for any export }
-    df_internal
+    df_internal,
+    { the def was derived with generic type or const fields so the size
+      of the def can not be determined }
+    df_has_generic_fields
   );
   tdefoptions=set of tdefoption;
 
@@ -651,7 +654,7 @@ type
     arraydef,recorddef,pointerdef,orddef,
     stringdef,enumdef,procdef,objectdef,errordef,
     filedef,formaldef,setdef,procvardef,floatdef,
-    classrefdef,forwarddef,variantdef,undefineddef
+    classrefdef,forwarddef,variantdef,genericconstdef,undefineddef
   );
 
   { possible types for symtable entries }
@@ -692,7 +695,8 @@ type
   tconsttyp = (constnone,
     constord,conststring,constreal,
     constset,constpointer,constnil,
-    constresourcestring,constwstring,constguid
+    constresourcestring,constwstring,constguid,
+    constundefined
   );
 
   { RTTI information to store }
@@ -831,7 +835,7 @@ inherited_objectoptions : tobjectoptions = [oo_has_virtual,oo_has_private,oo_has
        'abstractdef','arraydef','recorddef','pointerdef','orddef',
        'stringdef','enumdef','procdef','objectdef','errordef',
        'filedef','formaldef','setdef','procvardef','floatdef',
-       'classrefdef','forwarddef','variantdef','undefineddef'
+       'classrefdef','forwarddef','variantdef','genconstdef','undefineddef'
      );
 
      EqualTypeName : array[tequaltype] of string[16] = (
diff --git a/compiler/symdef.pas b/compiler/symdef.pas
index 4a260c46b9..0f7a2e4c06 100644
--- a/compiler/symdef.pas
+++ b/compiler/symdef.pas
@@ -129,6 +129,9 @@ interface
           function is_generic:boolean;inline;
           { same as above for specializations }
           function is_specialization:boolean;inline;
+          { generic utilities }
+          function is_generic_param_const(index:integer):boolean;inline;
+          function get_generic_param_def(index:integer):tdef;inline;
           { registers this def in the unit's deflist; no-op if already registered }
           procedure register_def; override;
           { add the def to the top of the symtable stack if it's not yet owned
@@ -2197,13 +2200,26 @@ implementation
          for i:=0 to genericparas.count-1 do
            begin
              sym:=tsym(genericparas[i]);
-             if sym.typ<>symconst.typesym then
+             { sym must be either a type or const }
+             if not (sym.typ in [symconst.typesym,symconst.constsym]) then
                internalerror(2014050903);
              if sym.owner.defowner<>self then
                exit(false);
            end;
      end;
 
+   function tstoreddef.is_generic_param_const(index:integer):boolean;
+     begin
+       result := tsym(genericparas[index]).typ = constsym;
+     end;  
+
+   function tstoreddef.get_generic_param_def(index:integer):tdef;
+     begin
+       if tsym(genericparas[index]).typ = constsym then
+         result := tconstsym(genericparas[index]).constdef
+       else
+         result := ttypesym(genericparas[index]).typedef;
+     end;
 
    function tstoreddef.is_specialization: boolean;
      var
@@ -2220,12 +2236,12 @@ implementation
            for i:=0 to genericparas.count-1 do
              begin
                sym:=tsym(genericparas[i]);
-               if sym.typ<>symconst.typesym then
+               { sym must be either a type or const }
+               if not (sym.typ in [symconst.typesym,symconst.constsym]) then
                  internalerror(2014050904);
                if sym.owner.defowner<>self then
                  exit(true);
              end;
-           result:=false;
          end;
      end;
 
diff --git a/compiler/symsym.pas b/compiler/symsym.pas
index b21a5f9de9..04c07a5ec7 100644
--- a/compiler/symsym.pas
+++ b/compiler/symsym.pas
@@ -157,7 +157,7 @@ interface
           fprettyname : ansistring;
           constructor create(const n : string;def:tdef;doregister:boolean);virtual;
           destructor destroy;override;
-          constructor ppuload(ppufile:tcompilerppufile);
+          constructor ppuload(ppufile:tcompilerppufile);virtual;
           { do not override this routine in platform-specific subclasses,
             override ppuwrite_platform instead }
           procedure ppuwrite(ppufile:tcompilerppufile);override;final;
@@ -392,6 +392,7 @@ interface
           constructor create_ptr(const n : string;t : tconsttyp;v : pointer;def:tdef);virtual;
           constructor create_string(const n : string;t : tconsttyp;str:pchar;l:longint;def:tdef);virtual;
           constructor create_wstring(const n : string;t : tconsttyp;pw:pcompilerwidestring);virtual;
+          constructor create_undefined(const n : string;def: tdef);
           constructor ppuload(ppufile:tcompilerppufile);
           destructor  destroy;override;
           procedure buildderef;override;
@@ -1581,7 +1582,6 @@ implementation
           tparasymtable(parast).ppuwrite(ppufile);
       end;
 
-
 {****************************************************************************
                             TABSTRACTVARSYM
 ****************************************************************************}
@@ -2344,6 +2344,13 @@ implementation
          value.len:=getlengthwidestring(pw);
       end;
 
+    constructor tconstsym.create_undefined(const n : string;def: tdef);
+      begin
+        inherited create(constsym,n,true);
+        fillchar(value, sizeof(value), #0);
+        consttyp:=constundefined;
+        constdef:=def;
+      end;
 
     constructor tconstsym.ppuload(ppufile:tcompilerppufile);
       var
@@ -2416,7 +2423,8 @@ implementation
                new(pguid(value.valueptr));
                ppufile.getdata(value.valueptr^,sizeof(tguid));
              end;
-           constnil :
+           constnil,
+           constundefined :
              ppufile.getderef(constdefderef);
            else
              Message1(unit_f_ppu_invalid_entry,tostr(ord(consttyp)));
@@ -2448,7 +2456,7 @@ implementation
       begin
         inherited;
         case consttyp  of
-          constnil,constord,constreal,constpointer,constset,conststring,constresourcestring,constguid:
+          constnil,constord,constreal,constpointer,constset,conststring,constresourcestring,constguid,constundefined:
             constdefderef.build(constdef);
           constwstring:
             ;
@@ -2461,7 +2469,7 @@ implementation
     procedure tconstsym.deref;
       begin
         case consttyp of
-          constnil,constord,constreal,constpointer,constset,conststring,constresourcestring,constguid:
+          constnil,constord,constreal,constpointer,constset,conststring,constresourcestring,constguid,constundefined:
             constdef:=tdef(constdefderef.resolve);
           constwstring:
             constdef:=carraydef.getreusable(cwidechartype,getlengthwidestring(pcompilerwidestring(value.valueptr)));
@@ -2476,7 +2484,8 @@ implementation
          inherited ppuwrite(ppufile);
          ppufile.putbyte(byte(consttyp));
          case consttyp of
-           constnil :
+           constnil,
+           constundefined :
              ppufile.putderef(constdefderef);
            constord :
              begin
@@ -2627,7 +2636,6 @@ implementation
           result:=inherited prettyname;
       end;
 
-
 {****************************************************************************
                                   TSYSSYM
 ****************************************************************************}
diff --git a/compiler/symtable.pas b/compiler/symtable.pas
index 796b2d6736..ae82024b03 100644
--- a/compiler/symtable.pas
+++ b/compiler/symtable.pas
@@ -2781,7 +2781,7 @@ implementation
 
     function generate_objectpascal_helper_key(def:tdef):string;
       begin
-        if not assigned(def) then
+        if not assigned(def) or (def.typ = errordef) then
           internalerror(2013020501);
         if def.typ in [recorddef,objectdef] then
           result:=make_mangledname('',tabstractrecorddef(def).symtable,'')
diff --git a/compiler/utils/ppuutils/ppudump.pp b/compiler/utils/ppuutils/ppudump.pp
index 74fde5c6c2..80d9d4df11 100644
--- a/compiler/utils/ppuutils/ppudump.pp
+++ b/compiler/utils/ppuutils/ppudump.pp
@@ -1552,7 +1552,8 @@ const
      { this should never happen for defs stored to a ppu file }
      (mask:df_not_registered_no_free;  str:'Unregistered/No free (invalid)'),
      (mask:df_llvm_no_struct_packing;  str:'LLVM unpacked struct'),
-     (mask:df_internal;       str:'Internal')
+     (mask:df_internal;       str:'Internal'),
+     (mask:df_has_generic_fields; str:'Has generic fields')
   );
   defstate : array[1..ord(high(tdefstate))] of tdefstateinfo=(
      (mask:ds_vmt_written;           str:'VMT Written'),
diff --git a/tests/test/tgenconst1.pp b/tests/test/tgenconst1.pp
new file mode 100644
index 0000000000..297b982b0f
--- /dev/null
+++ b/tests/test/tgenconst1.pp
@@ -0,0 +1,33 @@
+{$mode objfpc}
+program tgenconst1;
+
+type
+	kNames = set of (Blaise,Pascal);
+	kChars = set of char;
+type
+	generic TBoolean<const U: boolean> = record end;
+	generic TString<const U: string> = record end;
+	generic TFloat<const U: single> = record end;
+	generic TInteger<const U: integer> = record end;
+	generic TChar<const U: char> = record end;
+	generic TByte<const U: byte> = record end;
+	generic TQWord<const U: QWord> = record end;
+	generic TUndefined<const U> = record end;
+	generic TNames<const U: kNames> = record end;
+	generic TChars<const U: kChars> = record end;
+	generic TPointer<const U: pointer> = record end;
+
+var
+	a: specialize TBoolean<true>;
+	b: specialize TString<'string'>;
+	c: specialize TFloat<1>;
+	d: specialize TInteger<10>;
+	e: specialize TByte<255>;
+	f: specialize TChar<'a'>;
+	g: specialize TUndefined<nil>;
+	h: specialize TNames<[Blaise,Pascal]>;
+	i: specialize TChars<['a','b']>;
+	j: specialize TQWord<10>;
+	k: specialize TPointer<nil>;
+begin
+end.
diff --git a/tests/test/tgenconst10.pp b/tests/test/tgenconst10.pp
new file mode 100644
index 0000000000..f05a27718c
--- /dev/null
+++ b/tests/test/tgenconst10.pp
@@ -0,0 +1,13 @@
+{%FAIL}
+
+{$mode objfpc}
+
+program tgenconst10;
+
+type
+	generic TByte<T> = record end;
+	
+var
+	a: specialize TByte<10>;
+begin
+end.
diff --git a/tests/test/tgenconst11.pp b/tests/test/tgenconst11.pp
new file mode 100644
index 0000000000..ea409bec9b
--- /dev/null
+++ b/tests/test/tgenconst11.pp
@@ -0,0 +1,21 @@
+{%FAIL}
+{$mode objfpc}
+program tgenconst11;
+type
+	TEnum = (aaa,bbb,ccc,ddd);
+type
+	generic TConst<const U> = class end;
+
+var
+	a:specialize TConst<10>;
+	b:specialize TConst<10.5>;
+	c:specialize TConst<'string'>;
+	d:specialize TConst<[1,2,3]>;
+	e:specialize TConst<[aaa,bbb,ccc]>;
+begin
+	a:=specialize TConst<20>.Create;
+	b:=specialize TConst<10.1>.Create;
+	c:=specialize TConst<'_string'>.Create;
+	d:=specialize TConst<[1,2,3,4]>.Create;
+	e:=specialize TConst<[aaa,bbb,ccc,ddd]>.Create;
+end.
\ No newline at end of file
diff --git a/tests/test/tgenconst12.pp b/tests/test/tgenconst12.pp
new file mode 100644
index 0000000000..8f591f6867
--- /dev/null
+++ b/tests/test/tgenconst12.pp
@@ -0,0 +1,16 @@
+{$mode objfpc}
+program tgenconst12;
+
+type
+  generic TTest<const U> = class
+  		class procedure DoThis;
+  end;
+
+class procedure TTest.DoThis;
+begin
+end;
+
+type
+	ATest = specialize TTest<100>;
+begin 
+end.
diff --git a/tests/test/tgenconst13.pp b/tests/test/tgenconst13.pp
new file mode 100644
index 0000000000..0d5f8b1813
--- /dev/null
+++ b/tests/test/tgenconst13.pp
@@ -0,0 +1,20 @@
+{$mode objfpc}
+program tgenconst13;
+type
+	TEnum = (aaa,bbb,ccc);
+type
+	generic TConst<const U> = class end;
+
+var
+	a:specialize TConst<10>;
+	b:specialize TConst<10.5>;
+	c:specialize TConst<'string'>;
+	d:specialize TConst<[1,2,3]>;
+	e:specialize TConst<[aaa,bbb,ccc]>;
+begin
+	a:=specialize TConst<10>.Create;
+	b:=specialize TConst<10.5>.Create;
+	c:=specialize TConst<'string'>.Create;
+	d:=specialize TConst<[1,2,3]>.Create;
+	e:=specialize TConst<[aaa,bbb,ccc]>.Create;
+end.
diff --git a/tests/test/tgenconst14.pp b/tests/test/tgenconst14.pp
new file mode 100644
index 0000000000..7f98086630
--- /dev/null
+++ b/tests/test/tgenconst14.pp
@@ -0,0 +1,29 @@
+{$mode objfpc}
+{$modeswitch advancedrecords}
+program tgenconst14;
+
+type
+  generic TBinaryOp<const I: Integer> = record
+    const
+    	d0 = I + I;
+    	d1 = I - I; 
+    	d2 = I * I; 
+    	d3 = I / I; 
+    	d4 = I div I; 
+    	d5 = I mod I; 
+    	d6 = I and I;
+    	d7 = I or I;
+  end;
+
+var
+	op: specialize TBinaryOp<100>;
+begin
+	writeln(op.d0);
+	writeln(op.d1);
+	writeln(op.d2);
+	writeln(op.d3:1:1);
+	writeln(op.d4);
+	writeln(op.d5);
+	writeln(op.d6);
+	writeln(op.d7);
+end.
\ No newline at end of file
diff --git a/tests/test/tgenconst15.pp b/tests/test/tgenconst15.pp
new file mode 100644
index 0000000000..56744cd0a7
--- /dev/null
+++ b/tests/test/tgenconst15.pp
@@ -0,0 +1,30 @@
+{$mode objfpc}
+{$modeswitch advancedrecords}
+program tgenconst15;
+
+type
+	kNames = set of (Blaise, Pascal);
+  generic TSet<const I: kNames> = record
+    const c = I;
+  end;
+  generic TString<const I: String> = record
+    const c = I;
+  end;
+  generic TWideString<const I: WideString> = record
+    const c = I;
+  end;
+  generic TSingle<const I: Single> = record
+    const c = I; 
+  end;
+  generic TDouble<const I: Double> = record
+    const c = I; 
+  end;
+  generic TReal<const I: Real> = record
+    const c = I; 
+  end;
+
+var
+	a0: specialize TReal<100>;
+begin
+	writeln(a0.c);
+end.
\ No newline at end of file
diff --git a/tests/test/tgenconst2.pp b/tests/test/tgenconst2.pp
new file mode 100644
index 0000000000..aa3a960634
--- /dev/null
+++ b/tests/test/tgenconst2.pp
@@ -0,0 +1,12 @@
+{$mode objfpc}
+program tgenconst2;
+
+type
+	generic TStuff1<T1,T2;const U1,U2> = record end;
+	generic TStuff2<T1,T2;const U1,U2:integer> = record end;
+	
+var
+	a: specialize TStuff1<integer,string,10,'string'>;
+	b: specialize TStuff2<integer,string,10,10>;
+begin
+end.
diff --git a/tests/test/tgenconst3.pp b/tests/test/tgenconst3.pp
new file mode 100644
index 0000000000..aea0e307e2
--- /dev/null
+++ b/tests/test/tgenconst3.pp
@@ -0,0 +1,16 @@
+{$mode objfpc}
+{$modeswitch advancedrecords}
+program tgenconst3;
+
+type
+	generic TList<T;const U:integer> = record
+		const
+			max = U;
+		public
+			m_list: array[0..max-1] of T;
+	end;
+
+var
+	list: specialize TList<integer,128>;
+begin
+end.
diff --git a/tests/test/tgenconst4.pp b/tests/test/tgenconst4.pp
new file mode 100644
index 0000000000..a1fae00c43
--- /dev/null
+++ b/tests/test/tgenconst4.pp
@@ -0,0 +1,11 @@
+{$mode objfpc}
+program tgenconst4;
+
+generic procedure DoThis<T;const U:string>(msg:string = U);
+begin
+	writeln(msg, ' sizeof:',sizeof(t), ' default: ', U);
+end;
+
+begin
+	specialize DoThis<integer,'genparam'>('hello world');
+end.
diff --git a/tests/test/tgenconst5.pp b/tests/test/tgenconst5.pp
new file mode 100644
index 0000000000..63514a976c
--- /dev/null
+++ b/tests/test/tgenconst5.pp
@@ -0,0 +1,24 @@
+{$mode objfpc}
+program tgenconst5;
+
+type
+	generic THelperA<const U:integer> = record
+		list: array[0..U-1] of byte;
+	end;
+
+type
+	generic THelperB<T> = record
+		value: T;
+	end;
+
+type
+	generic TList<T; const U:integer> = record
+		helperA: specialize THelperA<U>;
+		helperB: specialize THelperB<T>;
+	end;
+
+var
+	list: specialize TList<integer,32>;
+begin
+	writeln('sizeof:',sizeof(list));
+end.
diff --git a/tests/test/tgenconst6.pp b/tests/test/tgenconst6.pp
new file mode 100644
index 0000000000..3ee3785423
--- /dev/null
+++ b/tests/test/tgenconst6.pp
@@ -0,0 +1,21 @@
+{$mode delphi}
+program tgenconst6;
+
+type
+	TList<T;const U> = class
+		list: array[0..U-1] of T;
+		function capacity: integer;
+	end;
+
+function TList<T,U>.capacity: integer;
+begin
+	result := U;	
+end;	
+
+var
+	nums:TList<integer,16>;
+	strs:TList<string,16>;
+begin
+	nums := TList<integer,16>.Create;
+	strs := TList<string,16>.Create;
+end.
diff --git a/tests/test/tgenconst7.pp b/tests/test/tgenconst7.pp
new file mode 100644
index 0000000000..9d8e81ef05
--- /dev/null
+++ b/tests/test/tgenconst7.pp
@@ -0,0 +1,11 @@
+{%FAIL}
+{$mode objfpc}
+program tgenconst7;
+
+type
+	generic TInteger<const U: integer> = record end;
+
+var
+	a: specialize TInteger<'string'>;
+begin
+end.
diff --git a/tests/test/tgenconst8.pp b/tests/test/tgenconst8.pp
new file mode 100644
index 0000000000..75844f7181
--- /dev/null
+++ b/tests/test/tgenconst8.pp
@@ -0,0 +1,11 @@
+{%FAIL}
+{$mode objfpc}
+program tgenconst8;
+
+type
+	generic TByte<const U: Byte> = record end;
+	
+var
+	a: specialize TByte<300>;
+begin
+end.
diff --git a/tests/test/tgenconst9.pp b/tests/test/tgenconst9.pp
new file mode 100644
index 0000000000..939cb90302
--- /dev/null
+++ b/tests/test/tgenconst9.pp
@@ -0,0 +1,11 @@
+{%FAIL}
+{$mode objfpc}
+program tgenconst9;
+
+type
+	generic TByte<const U: Byte> = record end;
+	
+var
+	a: specialize TByte<string>;
+begin
+end.
-- 
2.17.2 (Apple Git-113)

From 376a757c8340f9c8995c9ba25cc09400d0ce9280 Mon Sep 17 00:00:00 2001
From: Ryan Joseph <genericptr@gmail.com>
Date: Tue, 6 Nov 2018 13:58:49 +0700
Subject: [PATCH] constants in generics

---
 .gitignore                         |  24 +
 compiler/defcmp.pas                |   9 +-
 compiler/htypechk.pas              | 132 +++---
 compiler/ncon.pas                  |  42 +-
 compiler/nmat.pas                  |   5 +-
 compiler/node.pas                  |  22 +-
 compiler/nset.pas                  |   7 +-
 compiler/pdecl.pas                 |  53 ++-
 compiler/pdecvar.pas               |   4 +
 compiler/pexpr.pas                 |  11 +-
 compiler/pgentype.pas              |   8 +-
 compiler/pgenutil.pas              | 693 ++++++++++++++++++++---------
 compiler/ppu.pas                   |   2 +-
 compiler/ptype.pas                 |   4 +-
 compiler/symconst.pas              |  12 +-
 compiler/symdef.pas                |  22 +-
 compiler/symsym.pas                |  22 +-
 compiler/symtable.pas              |   2 +-
 compiler/utils/ppuutils/ppudump.pp |   3 +-
 tests/test/tgenconst1.pp           |  33 ++
 tests/test/tgenconst10.pp          |  13 +
 tests/test/tgenconst11.pp          |  21 +
 tests/test/tgenconst12.pp          |  16 +
 tests/test/tgenconst13.pp          |  20 +
 tests/test/tgenconst14.pp          |  29 ++
 tests/test/tgenconst15.pp          |  30 ++
 tests/test/tgenconst16.pp          |  86 ++++
 tests/test/tgenconst17.pp          |  36 ++
 tests/test/tgenconst18.pp          |  12 +
 tests/test/tgenconst2.pp           |  12 +
 tests/test/tgenconst3.pp           |  16 +
 tests/test/tgenconst4.pp           |  11 +
 tests/test/tgenconst5.pp           |  24 +
 tests/test/tgenconst6.pp           |  21 +
 tests/test/tgenconst7.pp           |  11 +
 tests/test/tgenconst8.pp           |  11 +
 tests/test/tgenconst9.pp           |  11 +
 37 files changed, 1163 insertions(+), 327 deletions(-)
 create mode 100644 .gitignore
 create mode 100644 tests/test/tgenconst1.pp
 create mode 100644 tests/test/tgenconst10.pp
 create mode 100644 tests/test/tgenconst11.pp
 create mode 100644 tests/test/tgenconst12.pp
 create mode 100644 tests/test/tgenconst13.pp
 create mode 100644 tests/test/tgenconst14.pp
 create mode 100644 tests/test/tgenconst15.pp
 create mode 100644 tests/test/tgenconst16.pp
 create mode 100644 tests/test/tgenconst17.pp
 create mode 100644 tests/test/tgenconst18.pp
 create mode 100644 tests/test/tgenconst2.pp
 create mode 100644 tests/test/tgenconst3.pp
 create mode 100644 tests/test/tgenconst4.pp
 create mode 100644 tests/test/tgenconst5.pp
 create mode 100644 tests/test/tgenconst6.pp
 create mode 100644 tests/test/tgenconst7.pp
 create mode 100644 tests/test/tgenconst8.pp
 create mode 100644 tests/test/tgenconst9.pp

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000000..a82c960cbe
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,24 @@
+# files
+.gitignore
+pp
+fpmake
+rtl/darwin/fpcmade.x86_64-darwin
+fpmake_proc1 copy.inc
+tests/*.x86_64-darwin
+rtl/Package.fpc
+tests/createlst
+tests/gparmake
+
+# directories
+lazbuild/
+x86_64-darwin/
+tests/tstunits/
+tests/utils
+
+# patterns
+*.app
+*.o
+*.ppu
+*.fpm
+*.rsj
+*.lst
\ No newline at end of file
diff --git a/compiler/defcmp.pas b/compiler/defcmp.pas
index 3f5882f762..793dbbbe76 100644
--- a/compiler/defcmp.pas
+++ b/compiler/defcmp.pas
@@ -175,7 +175,6 @@ implementation
       symtable,symsym,symcpu,
       defutil,symutil;
 
-
     function compare_defs_ext(def_from,def_to : tdef;
                               fromtreetype : tnodetype;
                               var doconv : tconverttype;
@@ -337,9 +336,13 @@ implementation
                        internalerror(2012091302);
                      symfrom:=ttypesym(tstoreddef(def_from).genericparas[i]);
                      symto:=ttypesym(tstoreddef(def_to).genericparas[i]);
-                     if not (symfrom.typ=typesym) or not (symto.typ=typesym) then
+                     if not (symfrom.typ in [typesym,constsym]) or not (symto.typ in [typesym,constsym]) then
                        internalerror(2012121401);
-                     if not equal_defs(ttypesym(symfrom).typedef,ttypesym(symto).typedef) then
+                     if symto.typ <> symfrom.typ then
+                       diff:=true
+                     else if (symfrom.typ=constsym) and (symto.typ=constsym) and not equal_constsym(tconstsym(symfrom),tconstsym(symto),true) then
+                       diff:=true
+                     else if not equal_defs(ttypesym(symfrom).typedef,ttypesym(symto).typedef) then
                        diff:=true;
                      if diff then
                        break;
diff --git a/compiler/htypechk.pas b/compiler/htypechk.pas
index 07c035dc26..bd51cebdf3 100644
--- a/compiler/htypechk.pas
+++ b/compiler/htypechk.pas
@@ -152,22 +152,22 @@ interface
     function token2managementoperator(optoken:ttoken):tmanagementoperator;
 
     { check operator args and result type }
-
-    type
-      toverload_check_flag = (
-        ocf_check_non_overloadable, { also check operators that are (currently) considered as
-                                      not overloadable (e.g. the "+" operator for dynamic arrays
-                                      if modeswitch arrayoperators is active) }
-        ocf_check_only              { only check whether the operator is overloaded, but don't
-                                      modify the passed in node (return true if the operator is
-                                      overloaded, false otherwise) }
-      );
-      toverload_check_flags = set of toverload_check_flag;
-
+
+    type
+      toverload_check_flag = (
+        ocf_check_non_overloadable, { also check operators that are (currently) considered as
+                                      not overloadable (e.g. the "+" operator for dynamic arrays
+                                      if modeswitch arrayoperators is active) }
+        ocf_check_only              { only check whether the operator is overloaded, but don't
+                                      modify the passed in node (return true if the operator is
+                                      overloaded, false otherwise) }
+      );
+      toverload_check_flags = set of toverload_check_flag;
+
     function isbinaryoperatoroverloadable(treetyp:tnodetype;ld:tdef;lt:tnodetype;rd:tdef;rt:tnodetype) : boolean;
     function isoperatoracceptable(pf : tprocdef; optoken : ttoken) : boolean;
-    function isunaryoverloaded(var t : tnode;ocf:toverload_check_flags) : boolean;
-    function isbinaryoverloaded(var t : tnode;ocf:toverload_check_flags) : boolean;
+    function isunaryoverloaded(var t : tnode;ocf:toverload_check_flags) : boolean;
+    function isbinaryoverloaded(var t : tnode;ocf:toverload_check_flags) : boolean;
 
     { Register Allocation }
     procedure make_not_regable(p : tnode; how: tregableinfoflags);
@@ -515,9 +515,9 @@ implementation
                     end;
 
                  { <dyn. array> + <dyn. array> is handled by the compiler }
-                 if (m_array_operators in current_settings.modeswitches) and
-                     (treetyp=addn) and
-                     (is_dynamic_array(ld) or is_dynamic_array(rd)) then
+                 if (m_array_operators in current_settings.modeswitches) and
+                     (treetyp=addn) and
+                     (is_dynamic_array(ld) or is_dynamic_array(rd)) then
                     begin
                       allowed:=false;
                       exit;
@@ -720,7 +720,7 @@ implementation
       end;
 
 
-    function isunaryoverloaded(var t : tnode;ocf:toverload_check_flags) : boolean;
+    function isunaryoverloaded(var t : tnode;ocf:toverload_check_flags) : boolean;
       var
         ld      : tdef;
         optoken : ttoken;
@@ -742,11 +742,11 @@ implementation
         else
           inlinenumber:=in_none;
 
-        if not (ocf_check_non_overloadable in ocf) and not isunaryoperatoroverloadable(t.nodetype,inlinenumber,ld) then
+        if not (ocf_check_non_overloadable in ocf) and not isunaryoperatoroverloadable(t.nodetype,inlinenumber,ld) then
           exit;
 
         { operator overload is possible }
-        result:=not (ocf_check_only in ocf);
+        result:=not (ocf_check_only in ocf);
 
         optoken:=NOTOKEN;
         case t.nodetype of
@@ -766,11 +766,11 @@ implementation
         end;
         if (optoken=NOTOKEN) then
           begin
-            if not (ocf_check_only in ocf) then
-              begin
-                CGMessage(parser_e_operator_not_overloaded);
-                t:=cnothingnode.create;
-              end;
+            if not (ocf_check_only in ocf) then
+              begin
+                CGMessage(parser_e_operator_not_overloaded);
+                t:=cnothingnode.create;
+              end;
             exit;
           end;
 
@@ -790,11 +790,11 @@ implementation
           begin
             candidates.free;
             ppn.free;
-            if not (ocf_check_only in ocf) then
-              begin
-                CGMessage2(parser_e_operator_not_overloaded_2,ld.typename,arraytokeninfo[optoken].str);
-                t:=cnothingnode.create;
-              end;
+            if not (ocf_check_only in ocf) then
+              begin
+                CGMessage2(parser_e_operator_not_overloaded_2,ld.typename,arraytokeninfo[optoken].str);
+                t:=cnothingnode.create;
+              end;
             exit;
           end;
 
@@ -811,16 +811,16 @@ implementation
           begin
             candidates.free;
             ppn.free;
-            if not (ocf_check_only in ocf) then
-              begin
-                CGMessage2(parser_e_operator_not_overloaded_2,ld.typename,arraytokeninfo[optoken].str);
-                t:=cnothingnode.create;
-              end;
+            if not (ocf_check_only in ocf) then
+              begin
+                CGMessage2(parser_e_operator_not_overloaded_2,ld.typename,arraytokeninfo[optoken].str);
+                t:=cnothingnode.create;
+              end;
             exit;
           end;
 
         { Multiple candidates left? }
-        if (cand_cnt>1) and not (ocf_check_only in ocf) then
+        if (cand_cnt>1) and not (ocf_check_only in ocf) then
           begin
             CGMessage(type_e_cant_choose_overload_function);
 {$ifdef EXTDEBUG}
@@ -833,13 +833,13 @@ implementation
           end;
         candidates.free;
 
-        if ocf_check_only in ocf then
-          begin
-            ppn.free;
-            result:=true;
-            exit;
-          end;
-
+        if ocf_check_only in ocf then
+          begin
+            ppn.free;
+            result:=true;
+            exit;
+          end;
+
         addsymref(operpd.procsym);
 
         { the nil as symtable signs firstcalln that this is
@@ -852,7 +852,7 @@ implementation
       end;
 
 
-    function isbinaryoverloaded(var t : tnode;ocf:toverload_check_flags) : boolean;
+    function isbinaryoverloaded(var t : tnode;ocf:toverload_check_flags) : boolean;
       var
         rd,ld   : tdef;
         optoken : ttoken;
@@ -945,14 +945,14 @@ implementation
         { load easier access variables }
         ld:=tbinarynode(t).left.resultdef;
         rd:=tbinarynode(t).right.resultdef;
-        if not (ocf_check_non_overloadable in ocf) and
-            not isbinaryoperatoroverloadable(t.nodetype,ld,tbinarynode(t).left.nodetype,rd,tbinarynode(t).right.nodetype) then
+        if not (ocf_check_non_overloadable in ocf) and
+            not isbinaryoperatoroverloadable(t.nodetype,ld,tbinarynode(t).left.nodetype,rd,tbinarynode(t).right.nodetype) then
           exit;
 
         { operator overload is possible }
-        { if we only check for the existance of the overload, then we assume that
-          it is not overloaded }
-        result:=not (ocf_check_only in ocf);
+        { if we only check for the existance of the overload, then we assume that
+          it is not overloaded }
+        result:=not (ocf_check_only in ocf);
 
         case t.nodetype of
            equaln:
@@ -997,19 +997,19 @@ implementation
              optoken:=_OP_IN;
            else
              begin
-               if not (ocf_check_only in ocf) then
-                 begin
-                   CGMessage(parser_e_operator_not_overloaded);
-                   t:=cnothingnode.create;
-                 end;
+               if not (ocf_check_only in ocf) then
+                 begin
+                   CGMessage(parser_e_operator_not_overloaded);
+                   t:=cnothingnode.create;
+                 end;
                exit;
              end;
         end;
 
-        cand_cnt:=search_operator(optoken,(optoken<>_NE) and not (ocf_check_only in ocf));
+        cand_cnt:=search_operator(optoken,(optoken<>_NE) and not (ocf_check_only in ocf));
 
         { no operator found for "<>" then search for "=" operator }
-        if (cand_cnt=0) and (optoken=_NE) and not (ocf_check_only in ocf) then
+        if (cand_cnt=0) and (optoken=_NE) and not (ocf_check_only in ocf) then
           begin
             ppn.free;
             ppn:=nil;
@@ -1021,15 +1021,15 @@ implementation
         if (cand_cnt=0) then
           begin
             ppn.free;
-            if not (ocf_check_only in ocf) then
-              t:=cnothingnode.create;
-            exit;
-          end;
-
-        if ocf_check_only in ocf then
-          begin
-            ppn.free;
-            result:=true;
+            if not (ocf_check_only in ocf) then
+              t:=cnothingnode.create;
+            exit;
+          end;
+
+        if ocf_check_only in ocf then
+          begin
+            ppn.free;
+            result:=true;
             exit;
           end;
 
@@ -2697,7 +2697,7 @@ implementation
               internalerror(2015060301);
             { check whether the given parameters are compatible
               to the def's constraints }
-            if not check_generic_constraints(pd,spezcontext.genericdeflist,spezcontext.poslist) then
+            if not check_generic_constraints(pd,spezcontext.paramlist,spezcontext.poslist) then
               exit;
             def:=generate_specialization_phase2(spezcontext,pd,false,'');
             case def.typ of
diff --git a/compiler/ncon.pas b/compiler/ncon.pas
index ae94637c28..1e203f74d6 100644
--- a/compiler/ncon.pas
+++ b/compiler/ncon.pas
@@ -279,6 +279,7 @@ implementation
         p1  : tnode;
         len : longint;
         pc  : pchar;
+        value_set : pconstset;
       begin
         p1:=nil;
         case p.consttyp of
@@ -304,18 +305,51 @@ implementation
           constwstring :
             p1:=cstringconstnode.createunistr(pcompilerwidestring(p.value.valueptr));
           constreal :
-            p1:=crealconstnode.create(pbestreal(p.value.valueptr)^,p.constdef);
+            begin
+              if sp_generic_para in p.symoptions then
+                p1:=crealconstnode.create(default(bestreal),p.constdef)
+              else
+                p1:=crealconstnode.create(pbestreal(p.value.valueptr)^,p.constdef);
+            end;
           constset :
-            p1:=csetconstnode.create(pconstset(p.value.valueptr),p.constdef);
+            begin
+              if sp_generic_para in p.symoptions then
+                begin
+                  new(value_set);
+                  p1:=csetconstnode.create(value_set,p.constdef);
+                end
+              else
+                p1:=csetconstnode.create(pconstset(p.value.valueptr),p.constdef);
+            end;
           constpointer :
-            p1:=cpointerconstnode.create(p.value.valueordptr,p.constdef);
+            begin
+              if sp_generic_para in p.symoptions then
+                p1:=cpointerconstnode.create(default(tconstptruint),p.constdef)
+              else
+                p1:=cpointerconstnode.create(p.value.valueordptr,p.constdef);
+            end;
           constnil :
             p1:=cnilnode.create;
+          { constundefined is a placeholder for unrestricted generic const params
+            so we just treat it as a nil node. }
+          constundefined :
+            begin
+              p1:=cnilnode.create;
+              p1.resultdef:=p.constdef;
+            end;
           constguid :
-            p1:=cguidconstnode.create(pguid(p.value.valueptr)^);
+            begin
+              if sp_generic_para in p.symoptions then
+                p1:=cguidconstnode.create(default(tguid))
+              else
+                p1:=cguidconstnode.create(pguid(p.value.valueptr)^);
+            end;
           else
             internalerror(200205103);
         end;
+        { transfer generic param flag from symbol to node }
+        if sp_generic_para in p.symoptions then
+          include(p1.flags,nf_generic_para);
         genconstsymtree:=p1;
       end;
 
diff --git a/compiler/nmat.pas b/compiler/nmat.pas
index 355b493da4..d10dff6128 100644
--- a/compiler/nmat.pas
+++ b/compiler/nmat.pas
@@ -129,7 +129,10 @@ implementation
               end;
             if rv = 0 then
               begin
-                Message(parser_e_division_by_zero);
+                { if the node is derived from a generic const parameter
+                  then don't issue an error }
+                if not (nf_generic_para in flags) then
+                  Message(parser_e_division_by_zero);
                 { recover }
                 tordconstnode(right).value := 1;
               end;
diff --git a/compiler/node.pas b/compiler/node.pas
index b8600000bf..33a85b1493 100644
--- a/compiler/node.pas
+++ b/compiler/node.pas
@@ -194,7 +194,8 @@ interface
           'loadparentfpn',
           'objcselectorn',
           'objcprotocoln',
-          'specializen');
+          'specializen'
+          );
 
       { a set containing all const nodes }
       nodetype_const = [ordconstn,
@@ -272,10 +273,13 @@ interface
          nf_block_with_exit,
 
          { tloadvmtaddrnode }
-         nf_ignore_for_wpo  { we know that this loadvmtaddrnode cannot be used to construct a class instance }
+         nf_ignore_for_wpo,  { we know that this loadvmtaddrnode cannot be used to construct a class instance }
 
-         { WARNING: there are now 31 elements in this type, and a set of this
-             type is written to the PPU. So before adding more than 32 elements,
+         { node is derived from generic parameter }
+         nf_generic_para
+
+         { WARNING: there are now 32 elements in this type, and a set of this
+             type is written to the PPU. So before adding more elements,
              either move some flags to specific nodes, or stream a normalset
              to the ppu
          }
@@ -983,6 +987,9 @@ implementation
     constructor tunarynode.create(t:tnodetype;l : tnode);
       begin
          inherited create(t);
+         { transfer generic paramater flag }
+         if assigned(l) and (nf_generic_para in l.flags) then
+           include(flags,nf_generic_para);
          left:=l;
       end;
 
@@ -1078,7 +1085,12 @@ implementation
     constructor tbinarynode.create(t:tnodetype;l,r : tnode);
       begin
          inherited create(t,l);
-         right:=r
+         { transfer generic paramater flag }
+         if assigned(l) and (nf_generic_para in l.flags) then
+           include(flags,nf_generic_para)
+         else if assigned(r) and (nf_generic_para in r.flags) then
+           include(flags,nf_generic_para);
+         right:=r;
       end;
 
 
diff --git a/compiler/nset.pas b/compiler/nset.pas
index 6270ec582e..bd031e6a86 100644
--- a/compiler/nset.pas
+++ b/compiler/nset.pas
@@ -239,7 +239,7 @@ implementation
            internalerror(20021126);
 
          t:=self;
-         if isbinaryoverloaded(t,[]) then
+         if isbinaryoverloaded(t,[]) then
            begin
              result:=t;
              exit;
@@ -392,8 +392,9 @@ implementation
          { both types must be compatible }
          if compare_defs(left.resultdef,right.resultdef,left.nodetype)=te_incompatible then
            IncompatibleTypes(left.resultdef,right.resultdef);
-         { Check if only when its a constant set }
-         if (left.nodetype=ordconstn) and (right.nodetype=ordconstn) then
+         { check if only when its a constant set and
+           ignore range nodes which are generic parameter derived }
+         if not (nf_generic_para in flags) and (left.nodetype=ordconstn) and (right.nodetype=ordconstn) then
           begin
             { upper limit must be greater or equal than lower limit }
             if (tordconstnode(left).value>tordconstnode(right).value) and
diff --git a/compiler/pdecl.pas b/compiler/pdecl.pas
index c5b5bcc921..d7e80b928f 100644
--- a/compiler/pdecl.pas
+++ b/compiler/pdecl.pas
@@ -126,9 +126,14 @@ implementation
              end;
            setconstn :
              begin
-               new(ps);
-               ps^:=tsetconstnode(p).value_set^;
-               hp:=cconstsym.create_ptr(orgname,constset,ps,p.resultdef);
+               if nf_generic_para in p.flags then
+                 hp:=cconstsym.create_ptr(orgname,constset,nil,p.resultdef)
+               else
+                 begin
+                   new(ps);
+                   ps^:=tsetconstnode(p).value_set^;
+                   hp:=cconstsym.create_ptr(orgname,constset,ps,p.resultdef);
+                 end;
              end;
            pointerconstn :
              begin
@@ -141,18 +146,18 @@ implementation
            typen :
              begin
                if is_interface(p.resultdef) then
-                begin
-                  if assigned(tobjectdef(p.resultdef).iidguid) then
-                   begin
-                     new(pg);
-                     pg^:=tobjectdef(p.resultdef).iidguid^;
-                     hp:=cconstsym.create_ptr(orgname,constguid,pg,p.resultdef);
-                   end
-                  else
-                   Message1(parser_e_interface_has_no_guid,tobjectdef(p.resultdef).objrealname^);
-                end
-               else
-                Message(parser_e_illegal_expression);
+                 begin
+                   if assigned(tobjectdef(p.resultdef).iidguid) then
+                     begin
+                       new(pg);
+                       pg^:=tobjectdef(p.resultdef).iidguid^;
+                       hp:=cconstsym.create_ptr(orgname,constguid,pg,p.resultdef);
+                     end
+                    else
+                      Message1(parser_e_interface_has_no_guid,tobjectdef(p.resultdef).objrealname^);
+                 end
+               else 
+                 Message(parser_e_illegal_expression);
              end;
            inlinen:
              begin
@@ -177,8 +182,19 @@ implementation
                end;
              end;
            else
-             Message(parser_e_illegal_expression);
+             begin
+               { the node is from a generic parameter constant and is 
+                 untyped so we need to pass a placeholder constant 
+                 instead of givng an error }
+               if nf_generic_para in p.flags then 
+                 hp:=cconstsym.create_ord(orgname,constnil,0,p.resultdef)
+               else
+                 Message(parser_e_illegal_expression);
+             end;
         end;
+        { transfer generic param flag from node to symbol }
+        if nf_generic_para in p.flags then
+          include(hp.symoptions,sp_generic_para);
         current_tokenpos:=storetokenpos;
         p.free;
         readconstant:=hp;
@@ -507,8 +523,9 @@ implementation
                { we are not freeing the type parameters, so register them }
                for i:=0 to generictypelist.count-1 do
                  begin
-                    ttypesym(generictypelist[i]).register_sym;
-                    tstoreddef(ttypesym(generictypelist[i]).typedef).register_def;
+                    tstoredsym(generictypelist[i]).register_sym;
+                    if tstoredsym(generictypelist[i]).typ=typesym then
+                      tstoreddef(ttypesym(generictypelist[i]).typedef).register_def;
                  end;
 
                str(generictypelist.Count,s);
diff --git a/compiler/pdecvar.pas b/compiler/pdecvar.pas
index 4d39397e46..8121d87853 100644
--- a/compiler/pdecvar.pas
+++ b/compiler/pdecvar.pas
@@ -1675,6 +1675,10 @@ implementation
                    end;
                end;
 
+             { field type is a generic param so set a flag in the struct }
+             if assigned(hdef.typesym) and (sp_generic_para in hdef.typesym.symoptions) then
+               include(current_structdef.defoptions,df_has_generic_fields);
+
              { Process procvar directives }
              if maybe_parse_proc_directives(hdef) then
                semicoloneaten:=true;
diff --git a/compiler/pexpr.pas b/compiler/pexpr.pas
index bc0606ed4b..e6d9633ebd 100644
--- a/compiler/pexpr.pas
+++ b/compiler/pexpr.pas
@@ -446,6 +446,9 @@ implementation
                   { no packed bit support for these things }
                   if l=in_bitsizeof_x then
                     statement_syssym:=caddnode.create(muln,statement_syssym,cordconstnode.create(8,sinttype,true));
+                  { type sym is a generic parameter }
+                  if assigned(p1.resultdef.typesym) and (sp_generic_para in p1.resultdef.typesym.symoptions) then
+                    include(statement_syssym.flags,nf_generic_para);
                 end
               else
                begin
@@ -466,6 +469,9 @@ implementation
                    end
                  else
                    statement_syssym:=cordconstnode.create(p1.resultdef.packedbitsize,sinttype,true);
+                 { type def is a struct with generic fields }
+                 if df_has_generic_fields in p1.resultdef.defoptions then
+                    include(statement_syssym.flags,nf_generic_para);
                  { p1 not needed !}
                  p1.destroy;
                end;
@@ -4078,7 +4084,10 @@ implementation
                 gendef:=generate_specialization_phase2(spezcontext,tstoreddef(gendef),false,'');
                 spezcontext.free;
                 spezcontext:=nil;
-                gensym:=gendef.typesym;
+                if gendef.typ=errordef then
+                  gensym:=generrorsym
+                else
+                  gensym:=gendef.typesym;
               end;
             procdef:
               begin
diff --git a/compiler/pgentype.pas b/compiler/pgentype.pas
index b2847c78f6..85270df256 100644
--- a/compiler/pgentype.pas
+++ b/compiler/pgentype.pas
@@ -28,7 +28,7 @@ interface
 uses
   cclasses,
   globtype,
-  symtype,symbase;
+  symconst,symtype,symbase;
 
 const
   inline_specialization_block_types = [bt_type,bt_var_type,bt_const_type,bt_body];
@@ -42,7 +42,7 @@ type
 
   tspecializationcontext=class
   public
-    genericdeflist : tfpobjectlist;
+    paramlist : tfpobjectlist;
     poslist : tfplist;
     prettyname : ansistring;
     specializename : ansistring;
@@ -58,7 +58,7 @@ implementation
 
 constructor tspecializationcontext.create;
 begin
-  genericdeflist:=tfpobjectlist.create(false);
+  paramlist:=tfpobjectlist.create(false);
   poslist:=tfplist.create;
 end;
 
@@ -66,7 +66,7 @@ destructor tspecializationcontext.destroy;
 var
   i : longint;
 begin
-  genericdeflist.free;
+  paramlist.free;
   for i:=0 to poslist.count-1 do
     dispose(pfileposinfo(poslist[i]));
   poslist.free;
diff --git a/compiler/pgenutil.pas b/compiler/pgenutil.pas
index 7760a4e134..ac6e59ce98 100644
--- a/compiler/pgenutil.pas
+++ b/compiler/pgenutil.pas
@@ -42,9 +42,9 @@ uses
     function generate_specialization_phase1(out context:tspecializationcontext;genericdef:tdef;symname:string):tdef;inline;
     function generate_specialization_phase1(out context:tspecializationcontext;genericdef:tdef;parsedtype:tdef;symname:string;parsedpos:tfileposinfo):tdef;
     function generate_specialization_phase2(context:tspecializationcontext;genericdef:tstoreddef;parse_class_parent:boolean;_prettyname:ansistring):tdef;
-    function check_generic_constraints(genericdef:tstoreddef;paradeflist:tfpobjectlist;poslist:tfplist):boolean;
+    function check_generic_constraints(genericdef:tstoreddef;paramlist:tfpobjectlist;poslist:tfplist):boolean;
     function parse_generic_parameters(allowconstraints:boolean):tfphashobjectlist;
-    function parse_generic_specialization_types(genericdeflist:tfpobjectlist;poslist:tfplist;out prettyname,specializename:ansistring):boolean;
+    function parse_generic_specialization_types(paramlist:tfpobjectlist;poslist:tfplist;out prettyname,specializename:ansistring):boolean;
     procedure insert_generic_parameter_types(def:tstoreddef;genericdef:tstoreddef;genericlist:tfphashobjectlist);
     procedure maybe_insert_generic_rename_symbol(const name:tidstring;genericlist:tfphashobjectlist);
     function generate_generic_name(const name:tidstring;specializename:ansistring;owner_hierarchy:string):tidstring;
@@ -63,18 +63,163 @@ implementation
 
 uses
   { common }
-  cutils,fpccrc,
+  sysutils,cutils,fpccrc,
   { global }
-  globals,tokens,verbose,finput,
+  globals,tokens,verbose,finput,constexp,
   { symtable }
-  symconst,symsym,symtable,defcmp,procinfo,
+  symconst,symsym,symtable,defcmp,defutil,procinfo,
   { modules }
   fmodule,
-  node,nobj,
+  node,nobj,ncon,
   { parser }
   scanner,
   pbase,pexpr,pdecsub,ptype,psub;
 
+  type
+    tdeftypeset = set of tdeftyp;
+  const
+    tgeneric_param_const_types : tdeftypeset = [orddef,stringdef,arraydef,floatdef,setdef,pointerdef,undefineddef];
+    tgeneric_param_nodes : tnodetypeset = [typen,ordconstn,stringconstn,realconstn,setconstn,niln];
+
+    function get_generic_param_def(sym:tsym):tdef;
+      begin
+        if sym.typ=constsym then
+          result:=tconstsym(sym).constdef
+        else
+          result:=ttypesym(sym).typedef;
+      end;
+
+    function is_generic_param_const(sym:tsym):boolean;
+      begin
+        if sym.typ=constsym then
+          result:=tconstsym(sym).consttyp<>constundefined
+        else
+          result:=false;
+      end;
+
+    function compare_orddef_by_range(param1,param2:torddef;value:tconstvalue):boolean;
+      begin
+        if (value.len<param2.low) or (value.len>param2.high) then
+          result:=false
+        else
+          result:=true;
+      end;
+
+    function compare_generic_params(param1,param2:tdef;constparamsym:tconstsym):boolean;
+      begin
+        if (param1.typ=orddef) and (param2.typ=orddef) then
+          begin
+            if is_boolean(param2) then
+              result:=is_boolean(param1)
+            else if is_char(param2) then
+              result:=is_char(param1)
+            else if compare_orddef_by_range(torddef(param1),torddef(param2),constparamsym.value) then
+              result:=true
+            else
+              result:=false;
+          end
+        { arraydef is string constant so it's compatible with stringdef }
+        else if (param1.typ=arraydef) and (param2.typ=stringdef) then
+          result:=true
+        { integer ords are compatible with float }
+        else if (param1.typ=orddef) and is_integer(param1) and (param2.typ=floatdef) then
+          result:=true
+        { undefined def is compatible with all types }
+        else if param2.typ=undefineddef then
+          result:=true
+        { sets require stricter checks }
+        else if is_set(param2) then
+          result:=equal_defs(param1,param2)
+        else
+          result:=param1.typ=param2.typ;
+      end;
+
+    function create_generic_constsym(fromdef:tdef;node:tnode;out prettyname:string):tconstsym;
+      const
+        undefinedname = 'undefined';
+      var
+        sym : tconstsym;
+        setdef : tsetdef;
+        enumsym : tsym;
+        enumname : string;
+        sp : pchar;
+        ps : ^tconstset;
+        pd : ^bestreal;
+        i : integer;
+      begin
+        if node=nil then
+          begin
+            sym:=cconstsym.create_undefined(undefinedname,fromdef);
+            sym.owner:=fromdef.owner;
+            prettyname:='';
+            result:=sym;
+            exit;
+          end;
+        case node.nodetype of
+          ordconstn:
+            begin
+              sym:=cconstsym.create_ord(undefinedname,constord,tordconstnode(node).value,fromdef);
+              prettyname:=inttostr(tordconstnode(node).value.svalue);
+            end;
+          stringconstn:
+            begin
+              getmem(sp,tstringconstnode(node).len+1);
+              move(tstringconstnode(node).value_str^,sp^,tstringconstnode(node).len+1);
+              sym:=cconstsym.create_string(undefinedname,conststring,sp,tstringconstnode(node).len,fromdef);
+              prettyname:=''''+tstringconstnode(node).value_str+'''';
+            end;
+          realconstn:
+            begin
+              new(pd);
+              pd^:=trealconstnode(node).value_real;
+              sym:=cconstsym.create_ptr(undefinedname,constreal,pd,fromdef);
+              prettyname:=floattostr(trealconstnode(node).value_real);
+            end;
+          setconstn:
+            begin
+              new(ps);
+              ps^:=tsetconstnode(node).value_set^;
+              sym:=cconstsym.create_ptr(undefinedname,constset,ps,fromdef);
+              setdef:=tsetdef(tsetconstnode(node).resultdef);
+              prettyname:='[';
+              for i := setdef.setbase to setdef.setmax do
+                if i in tsetconstnode(node).value_set^ then
+                  begin
+                    if setdef.elementdef.typ=enumdef then
+                      enumsym:=tenumdef(setdef.elementdef).int2enumsym(i)
+                    else
+                      enumsym:=nil;
+                    if assigned(enumsym) then
+                      enumname:=enumsym.realname
+                    else if setdef.elementdef.typ=orddef then
+                      begin
+                        if torddef(setdef.elementdef).ordtype=uchar then
+                          enumname:=chr(i)
+                        else
+                          enumname:=tostr(i);
+                      end
+                    else
+                      enumname:=tostr(i);
+                    if length(prettyname) > 1 then
+                      prettyname:=prettyname+','+enumname
+                    else
+                      prettyname:=prettyname+enumname;
+                  end;
+              prettyname:=prettyname+']';
+            end;
+          niln:
+            begin
+              { only "nil" is available for pointer constants }
+              sym:=cconstsym.create_ord(undefinedname,constnil,0,fromdef);
+              prettyname:='nil';
+            end;
+          else
+            internalerror(2019021601);
+        end;
+        { the sym needs an owner for later checks so us the typeparam owner }
+        sym.owner:=fromdef.owner;
+        result:=sym;
+      end;
 
     procedure maybe_add_waiting_unit(tt:tdef);
       var
@@ -104,203 +249,232 @@ uses
           end;
       end;
 
-    function check_generic_constraints(genericdef:tstoreddef;paradeflist:tfpobjectlist;poslist:tfplist):boolean;
+    function check_generic_constraints(genericdef:tstoreddef;paramlist:tfpobjectlist;poslist:tfplist):boolean;
       var
         i,j,
         intfcount : longint;
         formaldef,
         paradef : tstoreddef;
+        genparadef : tdef;
         objdef,
         paraobjdef,
         formalobjdef : tobjectdef;
         intffound : boolean;
         filepos : tfileposinfo;
+        //paratype : tconsttyp;
+        is_const : boolean;
       begin
         { check whether the given specialization parameters fit to the eventual
           constraints of the generic }
         if not assigned(genericdef.genericparas) or (genericdef.genericparas.count=0) then
           internalerror(2012101001);
-        if genericdef.genericparas.count<>paradeflist.count then
+        if genericdef.genericparas.count<>paramlist.count then
           internalerror(2012101002);
-        if paradeflist.count<>poslist.count then
+        if paramlist.count<>poslist.count then
           internalerror(2012120801);
         result:=true;
         for i:=0 to genericdef.genericparas.count-1 do
           begin
             filepos:=pfileposinfo(poslist[i])^;
-            formaldef:=tstoreddef(ttypesym(genericdef.genericparas[i]).typedef);
-            if formaldef.typ=undefineddef then
-              { the parameter is of unspecified type, so no need to check }
-              continue;
-            if not (df_genconstraint in formaldef.defoptions) or
-                not assigned(formaldef.genconstraintdata) then
-              internalerror(2013021602);
-            paradef:=tstoreddef(paradeflist[i]);
-            { undefineddef is compatible with anything }
-            if formaldef.typ=undefineddef then
-              continue;
-            if paradef.typ<>formaldef.typ then
+            paradef:=tstoreddef(get_generic_param_def(tsym(paramlist[i])));
+            is_const:=is_generic_param_const(tsym(paramlist[i]));
+            genparadef:=genericdef.get_generic_param_def(i);
+            { validate const params }
+            if not genericdef.is_generic_param_const(i) and is_const then
               begin
-                case formaldef.typ of
-                  recorddef:
-                    { delphi has own fantasy about record constraint
-                      (almost non-nullable/non-nilable value type) }
-                    if m_delphi in current_settings.modeswitches then
-                      case paradef.typ of
-                        floatdef,enumdef,orddef:
-                          continue;
-                        objectdef:
-                          if tobjectdef(paradef).objecttype=odt_object then
-                            continue
-                          else
-                            MessagePos(filepos,type_e_record_type_expected);
+                MessagePos(filepos,type_e_mismatch);
+                exit(false);
+              end
+            else if genericdef.is_generic_param_const(i) then
+              begin
+                { param type mismatch (type <> const) }
+                 if genericdef.is_generic_param_const(i) <> is_const then
+                   begin
+                    MessagePos(filepos,type_e_mismatch);
+                    exit(false);
+                  end;
+                { type constrained param doesn't match type }
+                if not compare_generic_params(paradef,genericdef.get_generic_param_def(i),tconstsym(paramlist[i])) then
+                  begin
+                    MessagePos2(filepos,type_e_incompatible_types,FullTypeName(paradef,genparadef),FullTypeName(genparadef,paradef));
+                    exit(false);
+                  end;
+              end;
+            { test constraints for non-const params }
+            if not genericdef.is_generic_param_const(i) then
+              begin
+                formaldef:=tstoreddef(ttypesym(genericdef.genericparas[i]).typedef);
+                if formaldef.typ=undefineddef then
+                  { the parameter is of unspecified type, so no need to check }
+                  continue;
+                if not (df_genconstraint in formaldef.defoptions) or
+                    not assigned(formaldef.genconstraintdata) then
+                  internalerror(2013021602);
+                { undefineddef is compatible with anything }
+                if formaldef.typ=undefineddef then
+                  continue;
+                if paradef.typ<>formaldef.typ then
+                  begin
+                    case formaldef.typ of
+                      recorddef:
+                        { delphi has own fantasy about record constraint
+                          (almost non-nullable/non-nilable value type) }
+                        if m_delphi in current_settings.modeswitches then
+                          case paradef.typ of
+                            floatdef,enumdef,orddef:
+                              continue;
+                            objectdef:
+                              if tobjectdef(paradef).objecttype=odt_object then
+                                continue
+                              else
+                                MessagePos(filepos,type_e_record_type_expected);
+                            else
+                              MessagePos(filepos,type_e_record_type_expected);
+                          end
                         else
                           MessagePos(filepos,type_e_record_type_expected);
-                      end
-                    else
-                      MessagePos(filepos,type_e_record_type_expected);
-                  objectdef:
-                    case tobjectdef(formaldef).objecttype of
-                      odt_class,
-                      odt_javaclass:
-                        MessagePos1(filepos,type_e_class_type_expected,paradef.typename);
-                      odt_interfacecom,
-                      odt_interfacecorba,
-                      odt_dispinterface,
-                      odt_interfacejava:
-                        MessagePos1(filepos,type_e_interface_type_expected,paradef.typename);
+                      objectdef:
+                        case tobjectdef(formaldef).objecttype of
+                          odt_class,
+                          odt_javaclass:
+                            MessagePos1(filepos,type_e_class_type_expected,paradef.typename);
+                          odt_interfacecom,
+                          odt_interfacecorba,
+                          odt_dispinterface,
+                          odt_interfacejava:
+                            MessagePos1(filepos,type_e_interface_type_expected,paradef.typename);
+                          else
+                            internalerror(2012101003);
+                        end;
+                      errordef:
+                        { ignore }
+                        ;
                       else
-                        internalerror(2012101003);
+                        internalerror(2012101004);
                     end;
-                  errordef:
-                    { ignore }
-                    ;
-                  else
-                    internalerror(2012101004);
-                end;
-                result:=false;
-              end
-            else
-              begin
-                { the paradef types are the same, so do special checks for the
-                  cases in which they are needed }
-                if formaldef.typ=objectdef then
+                    result:=false;
+                  end
+                else
                   begin
-                    paraobjdef:=tobjectdef(paradef);
-                    formalobjdef:=tobjectdef(formaldef);
-                    if not (formalobjdef.objecttype in [odt_class,odt_javaclass,odt_interfacecom,odt_interfacecorba,odt_interfacejava,odt_dispinterface]) then
-                      internalerror(2012101102);
-                    if formalobjdef.objecttype in [odt_interfacecom,odt_interfacecorba,odt_interfacejava,odt_dispinterface] then
+                    { the paradef types are the same, so do special checks for the
+                      cases in which they are needed }
+                    if formaldef.typ=objectdef then
                       begin
-                        { this is either a concerete interface or class type (the
-                          latter without specific implemented interfaces) }
-                        case paraobjdef.objecttype of
-                          odt_interfacecom,
-                          odt_interfacecorba,
-                          odt_interfacejava,
-                          odt_dispinterface:
-                            begin
-                              if (oo_is_forward in paraobjdef.objectoptions) and
-                                  (paraobjdef.objecttype=formalobjdef.objecttype) and
-                                  (df_genconstraint in formalobjdef.defoptions) and
-                                  (
-                                    (formalobjdef.objecttype=odt_interfacecom) and
-                                    (formalobjdef.childof=interface_iunknown)
-                                  )
-                                  or
-                                  (
-                                    (formalobjdef.objecttype=odt_interfacecorba) and
-                                    (formalobjdef.childof=nil)
-                                  ) then
-                                continue;
-                              if not def_is_related(paraobjdef,formalobjdef.childof) then
+                        paraobjdef:=tobjectdef(paradef);
+                        formalobjdef:=tobjectdef(formaldef);
+                        if not (formalobjdef.objecttype in [odt_class,odt_javaclass,odt_interfacecom,odt_interfacecorba,odt_interfacejava,odt_dispinterface]) then
+                          internalerror(2012101102);
+                        if formalobjdef.objecttype in [odt_interfacecom,odt_interfacecorba,odt_interfacejava,odt_dispinterface] then
+                          begin
+                            { this is either a concerete interface or class type (the
+                              latter without specific implemented interfaces) }
+                            case paraobjdef.objecttype of
+                              odt_interfacecom,
+                              odt_interfacecorba,
+                              odt_interfacejava,
+                              odt_dispinterface:
                                 begin
-                                  MessagePos2(filepos,type_e_incompatible_types,paraobjdef.typename,formalobjdef.childof.typename);
-                                  result:=false;
+                                  if (oo_is_forward in paraobjdef.objectoptions) and
+                                      (paraobjdef.objecttype=formalobjdef.objecttype) and
+                                      (df_genconstraint in formalobjdef.defoptions) and
+                                      (
+                                        (formalobjdef.objecttype=odt_interfacecom) and
+                                        (formalobjdef.childof=interface_iunknown)
+                                      )
+                                      or
+                                      (
+                                        (formalobjdef.objecttype=odt_interfacecorba) and
+                                        (formalobjdef.childof=nil)
+                                      ) then
+                                    continue;
+                                  if not def_is_related(paraobjdef,formalobjdef.childof) then
+                                    begin
+                                      MessagePos2(filepos,type_e_incompatible_types,paraobjdef.typename,formalobjdef.childof.typename);
+                                      result:=false;
+                                    end;
                                 end;
-                            end;
-                          odt_class,
-                          odt_javaclass:
-                            begin
-                              objdef:=paraobjdef;
-                              intffound:=false;
-                              while assigned(objdef) do
+                              odt_class,
+                              odt_javaclass:
                                 begin
-                                  for j:=0 to objdef.implementedinterfaces.count-1 do
-                                    if timplementedinterface(objdef.implementedinterfaces[j]).intfdef=formalobjdef.childof then
-                                      begin
-                                        intffound:=true;
+                                  objdef:=paraobjdef;
+                                  intffound:=false;
+                                  while assigned(objdef) do
+                                    begin
+                                      for j:=0 to objdef.implementedinterfaces.count-1 do
+                                        if timplementedinterface(objdef.implementedinterfaces[j]).intfdef=formalobjdef.childof then
+                                          begin
+                                            intffound:=true;
+                                            break;
+                                          end;
+                                      if intffound then
                                         break;
-                                      end;
-                                  if intffound then
-                                    break;
-                                  objdef:=objdef.childof;
+                                      objdef:=objdef.childof;
+                                    end;
+                                  result:=intffound;
+                                  if not result then
+                                    MessagePos2(filepos,parser_e_class_doesnt_implement_interface,paraobjdef.typename,formalobjdef.childof.typename);
+                                end;
+                              else
+                                begin
+                                  MessagePos1(filepos,type_e_class_or_interface_type_expected,paraobjdef.typename);
+                                  result:=false;
                                 end;
-                              result:=intffound;
-                              if not result then
-                                MessagePos2(filepos,parser_e_class_doesnt_implement_interface,paraobjdef.typename,formalobjdef.childof.typename);
-                            end;
-                          else
-                            begin
-                              MessagePos1(filepos,type_e_class_or_interface_type_expected,paraobjdef.typename);
-                              result:=false;
                             end;
-                        end;
-                      end
-                    else
-                      begin
-                        { this is either a "class" or a concrete instance with
-                          or without implemented interfaces }
-                        if not (paraobjdef.objecttype in [odt_class,odt_javaclass]) then
-                          begin
-                            MessagePos1(filepos,type_e_class_type_expected,paraobjdef.typename);
-                            result:=false;
-                            continue;
-                          end;
-                        { for forward declared classes we allow pure TObject/class declarations }
-                        if (oo_is_forward in paraobjdef.objectoptions) and
-                            (df_genconstraint in formaldef.defoptions) then
-                          begin
-                            if (formalobjdef.childof=class_tobject) and
-                                not formalobjdef.implements_any_interfaces then
-                              continue;
-                          end;
-                        if assigned(formalobjdef.childof) and
-                            not def_is_related(paradef,formalobjdef.childof) then
-                          begin
-                            MessagePos2(filepos,type_e_incompatible_types,paraobjdef.typename,formalobjdef.childof.typename);
-                            result:=false;
-                          end;
-                        intfcount:=0;
-                        for j:=0 to formalobjdef.implementedinterfaces.count-1 do
+                          end
+                        else
                           begin
-                            objdef:=paraobjdef;
-                            while assigned(objdef) do
+                            { this is either a "class" or a concrete instance with
+                              or without implemented interfaces }
+                            if not (paraobjdef.objecttype in [odt_class,odt_javaclass]) then
                               begin
-                                intffound:=assigned(
-                                             find_implemented_interface(objdef,
-                                               timplementedinterface(formalobjdef.implementedinterfaces[j]).intfdef
-                                             )
-                                           );
+                                MessagePos1(filepos,type_e_class_type_expected,paraobjdef.typename);
+                                result:=false;
+                                continue;
+                              end;
+                            { for forward declared classes we allow pure TObject/class declarations }
+                            if (oo_is_forward in paraobjdef.objectoptions) and
+                                (df_genconstraint in formaldef.defoptions) then
+                              begin
+                                if (formalobjdef.childof=class_tobject) and
+                                    not formalobjdef.implements_any_interfaces then
+                                  continue;
+                              end;
+                            if assigned(formalobjdef.childof) and
+                                not def_is_related(paradef,formalobjdef.childof) then
+                              begin
+                                MessagePos2(filepos,type_e_incompatible_types,paraobjdef.typename,formalobjdef.childof.typename);
+                                result:=false;
+                              end;
+                            intfcount:=0;
+                            for j:=0 to formalobjdef.implementedinterfaces.count-1 do
+                              begin
+                                objdef:=paraobjdef;
+                                while assigned(objdef) do
+                                  begin
+                                    intffound:=assigned(
+                                                 find_implemented_interface(objdef,
+                                                   timplementedinterface(formalobjdef.implementedinterfaces[j]).intfdef
+                                                 )
+                                               );
+                                    if intffound then
+                                      break;
+                                    objdef:=objdef.childof;
+                                  end;
                                 if intffound then
-                                  break;
-                                objdef:=objdef.childof;
+                                  inc(intfcount)
+                                else
+                                  MessagePos2(filepos,parser_e_class_doesnt_implement_interface,paraobjdef.typename,timplementedinterface(formalobjdef.implementedinterfaces[j]).intfdef.typename);
                               end;
-                            if intffound then
-                              inc(intfcount)
-                            else
-                              MessagePos2(filepos,parser_e_class_doesnt_implement_interface,paraobjdef.typename,timplementedinterface(formalobjdef.implementedinterfaces[j]).intfdef.typename);
+                            if intfcount<>formalobjdef.implementedinterfaces.count then
+                              result:=false;
                           end;
-                        if intfcount<>formalobjdef.implementedinterfaces.count then
-                          result:=false;
                       end;
                   end;
               end;
           end;
       end;
 
-
-    function parse_generic_specialization_types_internal(genericdeflist:tfpobjectlist;poslist:tfplist;out prettyname,specializename:ansistring;parsedtype:tdef;parsedpos:tfileposinfo):boolean;
+    function parse_generic_specialization_types_internal(paramlist:tfpobjectlist;poslist:tfplist;out prettyname,specializename:ansistring;parsedtype:tdef;parsedpos:tfileposinfo):boolean;
       var
         old_block_type : tblock_type;
         first : boolean;
@@ -310,9 +484,12 @@ uses
         namepart : string;
         prettynamepart : ansistring;
         module : tmodule;
+        //paramdef : tgenericparamdef;
+        constprettyname : string;
+        validparam : boolean;
       begin
         result:=true;
-        if genericdeflist=nil then
+        if paramlist=nil then
           internalerror(2012061401);
         { set the block type to type, so that the parsed type are returned as
           ttypenode (e.g. classes are in non type-compatible blocks returned as
@@ -324,7 +501,7 @@ uses
         first:=not assigned(parsedtype);
         if assigned(parsedtype) then
           begin
-            genericdeflist.Add(parsedtype);
+            paramlist.Add(parsedtype.typesym);
             module:=find_module_from_symtable(parsedtype.owner);
             if not assigned(module) then
               internalerror(2016112801);
@@ -351,7 +528,9 @@ uses
             block_type:=bt_type;
             tmpparampos:=current_filepos;
             typeparam:=factor(false,[ef_type_only]);
-            if typeparam.nodetype=typen then
+            { determine if the typeparam node is a valid type or const }
+            validparam:=typeparam.nodetype in tgeneric_param_nodes;
+            if validparam then
               begin
                 if tstoreddef(typeparam.resultdef).is_generic and
                     (
@@ -367,31 +546,47 @@ uses
                   end;
                 if typeparam.resultdef.typ<>errordef then
                   begin
-                    if not assigned(typeparam.resultdef.typesym) then
+                    if (typeparam.nodetype = typen) and not assigned(typeparam.resultdef.typesym) then
                       message(type_e_generics_cannot_reference_itself)
-                    else if (typeparam.resultdef.typ<>errordef) then
+                    else 
+                    if (typeparam.resultdef.typ<>errordef) then
                       begin
-                        genericdeflist.Add(typeparam.resultdef);
+                        { all non-type nodes are considered const }
+                        if typeparam.nodetype <> typen then
+                          paramlist.Add(create_generic_constsym(typeparam.resultdef,typeparam,constprettyname))
+                        else
+                          begin
+                            constprettyname:='';
+                            paramlist.Add(typeparam.resultdef.typesym);
+                          end;
                         module:=find_module_from_symtable(typeparam.resultdef.owner);
                         if not assigned(module) then
                           internalerror(2016112802);
                         namepart:='_$'+hexstr(module.moduleid,8)+'$$'+typeparam.resultdef.unique_id_str;
+                        if constprettyname <> '' then
+                          namepart:=namepart+'$$'+constprettyname;
                         { we use the full name of the type to uniquely identify it }
-                        if (symtablestack.top.symtabletype=parasymtable) and
-                            (symtablestack.top.defowner.typ=procdef) and
-                            (typeparam.resultdef.owner=symtablestack.top) then
-                          begin
-                            { special handling for specializations inside generic function declarations }
-                            prettynamepart:=tdef(symtablestack.top.defowner).fullownerhierarchyname(true)+tprocdef(symtablestack.top.defowner).procsym.prettyname;
-                          end
-                        else
+                        if typeparam.nodetype = typen then
                           begin
-                            prettynamepart:=typeparam.resultdef.fullownerhierarchyname(true);
+                            if (symtablestack.top.symtabletype=parasymtable) and
+                                (symtablestack.top.defowner.typ=procdef) and
+                                (typeparam.resultdef.owner=symtablestack.top) then
+                              begin
+                                { special handling for specializations inside generic function declarations }
+                                prettynamepart:=tdef(symtablestack.top.defowner).fullownerhierarchyname(true)+tprocdef(symtablestack.top.defowner).procsym.prettyname;
+                              end
+                            else
+                              begin
+                                prettynamepart:=typeparam.resultdef.fullownerhierarchyname(true);
+                              end;
                           end;
                         specializename:=specializename+namepart;
                         if not first then
                           prettyname:=prettyname+',';
-                        prettyname:=prettyname+prettynamepart+typeparam.resultdef.typesym.prettyname;
+                        if constprettyname <> '' then
+                          prettyname:=prettyname+constprettyname
+                        else
+                          prettyname:=prettyname+prettynamepart+typeparam.resultdef.typesym.prettyname;
                       end;
                   end
                 else
@@ -411,12 +606,12 @@ uses
       end;
 
 
-    function parse_generic_specialization_types(genericdeflist:tfpobjectlist;poslist:tfplist;out prettyname,specializename:ansistring):boolean;
+    function parse_generic_specialization_types(paramlist:tfpobjectlist;poslist:tfplist;out prettyname,specializename:ansistring):boolean;
       var
         dummypos : tfileposinfo;
       begin
         FillChar(dummypos, SizeOf(tfileposinfo), 0);
-        result:=parse_generic_specialization_types_internal(genericdeflist,poslist,prettyname,specializename,nil,dummypos);
+        result:=parse_generic_specialization_types_internal(paramlist,poslist,prettyname,specializename,nil,dummypos);
       end;
 
 
@@ -578,7 +773,7 @@ uses
         context:=tspecializationcontext.create;
 
         { Parse type parameters }
-        err:=not parse_generic_specialization_types_internal(context.genericdeflist,context.poslist,context.prettyname,context.specializename,parsedtype,parsedpos);
+        err:=not parse_generic_specialization_types_internal(context.paramlist,context.poslist,context.prettyname,context.specializename,parsedtype,parsedpos);
         if err then
           begin
             if not try_to_consume(_GT) then
@@ -627,7 +822,7 @@ uses
 
         { search a generic with the given count of params }
         countstr:='';
-        str(context.genericdeflist.Count,countstr);
+        str(context.paramlist.Count,countstr);
 
         genname:=genname+'$'+countstr;
         ugenname:=upper(genname);
@@ -656,7 +851,7 @@ uses
             result:=generrordef;
             exit;
           end;
-
+        
         { we've found the correct def }
         if context.sym.typ=typesym then
           result:=tstoreddef(ttypesym(context.sym).typedef)
@@ -747,6 +942,7 @@ uses
         hintsprocessed : boolean;
         pd : tprocdef;
         pdflags : tpdflags;
+        typedef : tstoreddef;
       begin
         if not assigned(context) then
           internalerror(2015052203);
@@ -755,7 +951,7 @@ uses
 
         pd:=nil;
 
-        if not check_generic_constraints(genericdef,context.genericdeflist,context.poslist) then
+        if not check_generic_constraints(genericdef,context.paramlist,context.poslist) then
           begin
             { the parameters didn't fit the constraints, so don't continue with the
               specialization }
@@ -771,20 +967,19 @@ uses
         else
           prettyname:=genericdef.typesym.prettyname;
         prettyname:=prettyname+'<'+context.prettyname+'>';
-
         generictypelist:=tfphashobjectlist.create(false);
 
         { build the list containing the types for the generic params }
         if not assigned(genericdef.genericparas) then
           internalerror(2013092601);
-        if context.genericdeflist.count<>genericdef.genericparas.count then
+        if context.paramlist.count<>genericdef.genericparas.count then
           internalerror(2013092603);
         for i:=0 to genericdef.genericparas.Count-1 do
           begin
             srsym:=tsym(genericdef.genericparas[i]);
             if not (sp_generic_para in srsym.symoptions) then
               internalerror(2013092602);
-            generictypelist.add(srsym.realname,tdef(context.genericdeflist[i]).typesym);
+            generictypelist.add(srsym.realname,context.paramlist[i]);
           end;
 
         { Special case if we are referencing the current defined object }
@@ -1196,8 +1391,8 @@ uses
 
     function parse_generic_parameters(allowconstraints:boolean):tfphashobjectlist;
       var
-        generictype : ttypesym;
-        i,firstidx : longint;
+        generictype : tstoredsym;
+        i,firstidx,const_list_index : longint;
         srsymtable : tsymtable;
         basedef,def : tdef;
         defname : tidstring;
@@ -1205,22 +1400,87 @@ uses
         doconsume : boolean;
         constraintdata : tgenericconstraintdata;
         old_block_type : tblock_type;
+        is_const,last_is_const : boolean;
+        last_token : ttoken;
+        last_type_pos : tfileposinfo;
       begin
         result:=tfphashobjectlist.create(false);
         firstidx:=0;
+        const_list_index:=0;
         old_block_type:=block_type;
         block_type:=bt_type;
+        is_const:=false;
+        last_is_const:=false;
+        last_token:=NOTOKEN;
         repeat
+          if try_to_consume(_CONST) then
+            begin
+              { last param was const without semicolon terminator }
+              if (result.count>0) and last_is_const and (last_token<>_SEMICOLON) then
+                MessagePos2(last_type_pos,scan_f_syn_expected,arraytokeninfo[_SEMICOLON].str,arraytokeninfo[last_token].str);
+              is_const := true;
+              const_list_index := result.count;
+            end;
           if token=_ID then
             begin
-              generictype:=ctypesym.create(orgpattern,cundefinedtype,false);
+              if is_const then
+                begin
+                  { last param was type without semicolon terminator }
+                  if (result.count>0) and not last_is_const and (last_token<>_SEMICOLON) then
+                    MessagePos2(last_type_pos,scan_f_syn_expected,arraytokeninfo[_SEMICOLON].str,arraytokeninfo[last_token].str);
+                  generictype:=tconstsym.create_undefined(orgpattern,cundefinedtype);
+                end
+              else
+                begin
+                  { last param was const without semicolon terminator }
+                  if (result.count>0) and last_is_const and (last_token<>_SEMICOLON) then
+                    MessagePos2(last_type_pos,scan_f_syn_expected,arraytokeninfo[_SEMICOLON].str,arraytokeninfo[last_token].str);
+                  generictype:=ttypesym.create(orgpattern,cundefinedtype,false);
+                end;
               { type parameters need to be added as strict private }
               generictype.visibility:=vis_strictprivate;
               include(generictype.symoptions,sp_generic_para);
               result.add(orgpattern,generictype);
+              last_is_const:=is_const;
             end;
           consume(_ID);
-          if try_to_consume(_COLON) then
+          { const restriction }
+          if is_const then
+            begin
+              if try_to_consume(_COLON) then
+                begin
+                  def := nil;
+                  { parse the type and assign the const type to generictype  }
+                  single_type(def,[]);
+                  for i:=const_list_index to result.count-1 do
+                    begin
+                      { finalize constant information once type is known }
+                      if assigned(def) and (def.typ in tgeneric_param_const_types) then
+                        begin
+                          case def.typ of
+                            orddef:
+                              tconstsym(result[i]).consttyp:=constord;
+                            stringdef:
+                              tconstsym(result[i]).consttyp:=conststring;
+                            floatdef:
+                              tconstsym(result[i]).consttyp:=constreal;
+                            setdef:
+                              tconstsym(result[i]).consttyp:=constset;
+                            { pointer always refers to nil with constants }
+                            pointerdef:
+                              tconstsym(result[i]).consttyp:=constnil;
+                          end;
+                          tconstsym(result[i]).constdef:=def;
+                        end
+                      else
+                        Message(type_e_mismatch);
+                    end;
+                  { after type restriction const list terminates }
+                  is_const:=false;
+                end;
+            end
+          { type restriction }
+          else if try_to_consume(_COLON) then
             begin
               if not allowconstraints then
                 { TODO }
@@ -1335,6 +1595,7 @@ uses
                     basedef:=cobjectdef.create(tobjectdef(def).objecttype,defname,tobjectdef(def),false);
                     constraintdata.interfaces.delete(0);
                   end;
+
               if basedef.typ<>errordef then
                 with tstoreddef(basedef) do
                   begin
@@ -1360,21 +1621,27 @@ uses
                 begin
                   { two different typeless parameters are considered as incompatible }
                   for i:=firstidx to result.count-1 do
-                    begin
-                      ttypesym(result[i]).typedef:=cundefineddef.create(false);
-                      ttypesym(result[i]).typedef.typesym:=ttypesym(result[i]);
-                    end;
+                    if tsym(result[i]).typ<>constsym then
+                      begin
+                        ttypesym(result[i]).typedef:=cundefineddef.create(false);
+                        ttypesym(result[i]).typedef.typesym:=ttypesym(result[i]);
+                      end;
                   { a semicolon terminates a type parameter group }
                   firstidx:=result.count;
                 end;
             end;
+          if token = _SEMICOLON then
+            is_const:=false;
+          last_token:=token;
+          last_type_pos:=current_filepos;
         until not (try_to_consume(_COMMA) or try_to_consume(_SEMICOLON));
         { two different typeless parameters are considered as incompatible }
         for i:=firstidx to result.count-1 do
-          begin
-            ttypesym(result[i]).typedef:=cundefineddef.create(false);
-            ttypesym(result[i]).typedef.typesym:=ttypesym(result[i]);
-          end;
+          if tsym(result[i]).typ<>constsym then
+            begin
+              ttypesym(result[i]).typedef:=cundefineddef.create(false);
+              ttypesym(result[i]).typedef.typesym:=ttypesym(result[i]);
+            end;
         block_type:=old_block_type;
       end;
 
@@ -1382,7 +1649,9 @@ uses
     procedure insert_generic_parameter_types(def:tstoreddef;genericdef:tstoreddef;genericlist:tfphashobjectlist);
       var
         i : longint;
-        generictype,sym : ttypesym;
+        generictype : tstoredsym;
+        generictypedef : tdef;
+        sym : tsym;
         st : tsymtable;
       begin
         def.genericdef:=genericdef;
@@ -1407,10 +1676,22 @@ uses
           def.genericparas:=tfphashobjectlist.create(false);
         for i:=0 to genericlist.count-1 do
           begin
-            generictype:=ttypesym(genericlist[i]);
+            generictype:=tstoredsym(genericlist[i]);
             if assigned(generictype.owner) then
               begin
-                sym:=ctypesym.create(genericlist.nameofindex(i),generictype.typedef,true);
+                if generictype.typ=typesym then
+                  sym:=ctypesym.create(genericlist.nameofindex(i),ttypesym(generictype).typedef,true)
+                else if generictype.typ=constsym then
+                  { generictype is a constsym that was created in create_generic_constsym 
+                    during phase 1 so we pass this directly without copying }
+                  begin
+                    sym:=generictype;
+                    { the sym name is still undefined so we set it to match
+                      the generic param name so it's accessible }
+                    sym.realname:=genericlist.nameofindex(i);
+                  end
+                else
+                  internalerror(2019021602);
                 { type parameters need to be added as strict private }
                 sym.visibility:=vis_strictprivate;
                 st.insert(sym);
@@ -1418,13 +1699,17 @@ uses
               end
             else
               begin
-                if (generictype.typedef.typ=undefineddef) and (generictype.typedef<>cundefinedtype) then
+                if generictype.typ=typesym then
                   begin
-                    { the generic parameters were parsed before the genericdef existed thus the
-                      undefineddefs were added as part of the parent symtable }
-                    if assigned(generictype.typedef.owner) then
-                      generictype.typedef.owner.DefList.Extract(generictype.typedef);
-                    generictype.typedef.changeowner(st);
+                    generictypedef:=ttypesym(generictype).typedef;
+                    if (generictypedef.typ=undefineddef) and (generictypedef<>cundefinedtype) then
+                      begin
+                        { the generic parameters were parsed before the genericdef existed thus the
+                          undefineddefs were added as part of the parent symtable }
+                        if assigned(generictypedef.owner) then
+                          generictypedef.owner.DefList.Extract(generictypedef);
+                        generictypedef.changeowner(st);
+                      end;
                   end;
                 st.insert(generictype);
                 include(generictype.symoptions,sp_generic_para);
diff --git a/compiler/ppu.pas b/compiler/ppu.pas
index 10c42e7eb8..31011be3e8 100644
--- a/compiler/ppu.pas
+++ b/compiler/ppu.pas
@@ -43,7 +43,7 @@ type
 {$endif Test_Double_checksum}
 
 const
-  CurrentPPUVersion = 201;
+  CurrentPPUVersion = 203;
 
 { unit flags }
   uf_init                = $000001; { unit has initialization section }
diff --git a/compiler/ptype.pas b/compiler/ptype.pas
index 38e2526e9f..28cd0f94f8 100644
--- a/compiler/ptype.pas
+++ b/compiler/ptype.pas
@@ -1436,7 +1436,9 @@ implementation
                                  highval:=tordconstnode(trangenode(pt).right).value;
                                  if highval<lowval then
                                   begin
-                                    Message(parser_e_array_lower_less_than_upper_bound);
+                                    { ignore error if node is generic param }
+                                    if not (nf_generic_para in pt.flags) then
+                                      Message(parser_e_array_lower_less_than_upper_bound);
                                     highval:=lowval;
                                   end
                                  else if (lowval<int64(low(asizeint))) or
diff --git a/compiler/symconst.pas b/compiler/symconst.pas
index a5ae7e0fb9..e02ce3a8ca 100644
--- a/compiler/symconst.pas
+++ b/compiler/symconst.pas
@@ -232,7 +232,10 @@ type
       because we have to access this information in the symtable unit }
     df_llvm_no_struct_packing,
     { internal def that's not for any export }
-    df_internal
+    df_internal,
+    { the def was derived with generic type or const fields so the size
+      of the def can not be determined }
+    df_has_generic_fields
   );
   tdefoptions=set of tdefoption;
 
@@ -651,7 +654,7 @@ type
     arraydef,recorddef,pointerdef,orddef,
     stringdef,enumdef,procdef,objectdef,errordef,
     filedef,formaldef,setdef,procvardef,floatdef,
-    classrefdef,forwarddef,variantdef,undefineddef
+    classrefdef,forwarddef,variantdef,genericconstdef,undefineddef
   );
 
   { possible types for symtable entries }
@@ -692,7 +695,8 @@ type
   tconsttyp = (constnone,
     constord,conststring,constreal,
     constset,constpointer,constnil,
-    constresourcestring,constwstring,constguid
+    constresourcestring,constwstring,constguid,
+    constundefined
   );
 
   { RTTI information to store }
@@ -831,7 +835,7 @@ inherited_objectoptions : tobjectoptions = [oo_has_virtual,oo_has_private,oo_has
        'abstractdef','arraydef','recorddef','pointerdef','orddef',
        'stringdef','enumdef','procdef','objectdef','errordef',
        'filedef','formaldef','setdef','procvardef','floatdef',
-       'classrefdef','forwarddef','variantdef','undefineddef'
+       'classrefdef','forwarddef','variantdef','genconstdef','undefineddef'
      );
 
      EqualTypeName : array[tequaltype] of string[16] = (
diff --git a/compiler/symdef.pas b/compiler/symdef.pas
index 4a260c46b9..0f7a2e4c06 100644
--- a/compiler/symdef.pas
+++ b/compiler/symdef.pas
@@ -129,6 +129,9 @@ interface
           function is_generic:boolean;inline;
           { same as above for specializations }
           function is_specialization:boolean;inline;
+          { generic utilities }
+          function is_generic_param_const(index:integer):boolean;inline;
+          function get_generic_param_def(index:integer):tdef;inline;
           { registers this def in the unit's deflist; no-op if already registered }
           procedure register_def; override;
           { add the def to the top of the symtable stack if it's not yet owned
@@ -2197,13 +2200,26 @@ implementation
          for i:=0 to genericparas.count-1 do
            begin
              sym:=tsym(genericparas[i]);
-             if sym.typ<>symconst.typesym then
+             { sym must be either a type or const }
+             if not (sym.typ in [symconst.typesym,symconst.constsym]) then
                internalerror(2014050903);
              if sym.owner.defowner<>self then
                exit(false);
            end;
      end;
 
+   function tstoreddef.is_generic_param_const(index:integer):boolean;
+     begin
+       result := tsym(genericparas[index]).typ = constsym;
+     end;  
+
+   function tstoreddef.get_generic_param_def(index:integer):tdef;
+     begin
+       if tsym(genericparas[index]).typ = constsym then
+         result := tconstsym(genericparas[index]).constdef
+       else
+         result := ttypesym(genericparas[index]).typedef;
+     end;
 
    function tstoreddef.is_specialization: boolean;
      var
@@ -2220,12 +2236,12 @@ implementation
            for i:=0 to genericparas.count-1 do
              begin
                sym:=tsym(genericparas[i]);
-               if sym.typ<>symconst.typesym then
+               { sym must be either a type or const }
+               if not (sym.typ in [symconst.typesym,symconst.constsym]) then
                  internalerror(2014050904);
                if sym.owner.defowner<>self then
                  exit(true);
              end;
-           result:=false;
          end;
      end;
 
diff --git a/compiler/symsym.pas b/compiler/symsym.pas
index b21a5f9de9..04c07a5ec7 100644
--- a/compiler/symsym.pas
+++ b/compiler/symsym.pas
@@ -157,7 +157,7 @@ interface
           fprettyname : ansistring;
           constructor create(const n : string;def:tdef;doregister:boolean);virtual;
           destructor destroy;override;
-          constructor ppuload(ppufile:tcompilerppufile);
+          constructor ppuload(ppufile:tcompilerppufile);virtual;
           { do not override this routine in platform-specific subclasses,
             override ppuwrite_platform instead }
           procedure ppuwrite(ppufile:tcompilerppufile);override;final;
@@ -392,6 +392,7 @@ interface
           constructor create_ptr(const n : string;t : tconsttyp;v : pointer;def:tdef);virtual;
           constructor create_string(const n : string;t : tconsttyp;str:pchar;l:longint;def:tdef);virtual;
           constructor create_wstring(const n : string;t : tconsttyp;pw:pcompilerwidestring);virtual;
+          constructor create_undefined(const n : string;def: tdef);
           constructor ppuload(ppufile:tcompilerppufile);
           destructor  destroy;override;
           procedure buildderef;override;
@@ -1581,7 +1582,6 @@ implementation
           tparasymtable(parast).ppuwrite(ppufile);
       end;
 
-
 {****************************************************************************
                             TABSTRACTVARSYM
 ****************************************************************************}
@@ -2344,6 +2344,13 @@ implementation
          value.len:=getlengthwidestring(pw);
       end;
 
+    constructor tconstsym.create_undefined(const n : string;def: tdef);
+      begin
+        inherited create(constsym,n,true);
+        fillchar(value, sizeof(value), #0);
+        consttyp:=constundefined;
+        constdef:=def;
+      end;
 
     constructor tconstsym.ppuload(ppufile:tcompilerppufile);
       var
@@ -2416,7 +2423,8 @@ implementation
                new(pguid(value.valueptr));
                ppufile.getdata(value.valueptr^,sizeof(tguid));
              end;
-           constnil :
+           constnil,
+           constundefined :
              ppufile.getderef(constdefderef);
            else
              Message1(unit_f_ppu_invalid_entry,tostr(ord(consttyp)));
@@ -2448,7 +2456,7 @@ implementation
       begin
         inherited;
         case consttyp  of
-          constnil,constord,constreal,constpointer,constset,conststring,constresourcestring,constguid:
+          constnil,constord,constreal,constpointer,constset,conststring,constresourcestring,constguid,constundefined:
             constdefderef.build(constdef);
           constwstring:
             ;
@@ -2461,7 +2469,7 @@ implementation
     procedure tconstsym.deref;
       begin
         case consttyp of
-          constnil,constord,constreal,constpointer,constset,conststring,constresourcestring,constguid:
+          constnil,constord,constreal,constpointer,constset,conststring,constresourcestring,constguid,constundefined:
             constdef:=tdef(constdefderef.resolve);
           constwstring:
             constdef:=carraydef.getreusable(cwidechartype,getlengthwidestring(pcompilerwidestring(value.valueptr)));
@@ -2476,7 +2484,8 @@ implementation
          inherited ppuwrite(ppufile);
          ppufile.putbyte(byte(consttyp));
          case consttyp of
-           constnil :
+           constnil,
+           constundefined :
              ppufile.putderef(constdefderef);
            constord :
              begin
@@ -2627,7 +2636,6 @@ implementation
           result:=inherited prettyname;
       end;
 
-
 {****************************************************************************
                                   TSYSSYM
 ****************************************************************************}
diff --git a/compiler/symtable.pas b/compiler/symtable.pas
index 796b2d6736..ae82024b03 100644
--- a/compiler/symtable.pas
+++ b/compiler/symtable.pas
@@ -2781,7 +2781,7 @@ implementation
 
     function generate_objectpascal_helper_key(def:tdef):string;
       begin
-        if not assigned(def) then
+        if not assigned(def) or (def.typ = errordef) then
           internalerror(2013020501);
         if def.typ in [recorddef,objectdef] then
           result:=make_mangledname('',tabstractrecorddef(def).symtable,'')
diff --git a/compiler/utils/ppuutils/ppudump.pp b/compiler/utils/ppuutils/ppudump.pp
index 74fde5c6c2..80d9d4df11 100644
--- a/compiler/utils/ppuutils/ppudump.pp
+++ b/compiler/utils/ppuutils/ppudump.pp
@@ -1552,7 +1552,8 @@ const
      { this should never happen for defs stored to a ppu file }
      (mask:df_not_registered_no_free;  str:'Unregistered/No free (invalid)'),
      (mask:df_llvm_no_struct_packing;  str:'LLVM unpacked struct'),
-     (mask:df_internal;       str:'Internal')
+     (mask:df_internal;       str:'Internal'),
+     (mask:df_has_generic_fields; str:'Has generic fields')
   );
   defstate : array[1..ord(high(tdefstate))] of tdefstateinfo=(
      (mask:ds_vmt_written;           str:'VMT Written'),
diff --git a/tests/test/tgenconst1.pp b/tests/test/tgenconst1.pp
new file mode 100644
index 0000000000..297b982b0f
--- /dev/null
+++ b/tests/test/tgenconst1.pp
@@ -0,0 +1,33 @@
+{$mode objfpc}
+program tgenconst1;
+
+type
+	kNames = set of (Blaise,Pascal);
+	kChars = set of char;
+type
+	generic TBoolean<const U: boolean> = record end;
+	generic TString<const U: string> = record end;
+	generic TFloat<const U: single> = record end;
+	generic TInteger<const U: integer> = record end;
+	generic TChar<const U: char> = record end;
+	generic TByte<const U: byte> = record end;
+	generic TQWord<const U: QWord> = record end;
+	generic TUndefined<const U> = record end;
+	generic TNames<const U: kNames> = record end;
+	generic TChars<const U: kChars> = record end;
+	generic TPointer<const U: pointer> = record end;
+
+var
+	a: specialize TBoolean<true>;
+	b: specialize TString<'string'>;
+	c: specialize TFloat<1>;
+	d: specialize TInteger<10>;
+	e: specialize TByte<255>;
+	f: specialize TChar<'a'>;
+	g: specialize TUndefined<nil>;
+	h: specialize TNames<[Blaise,Pascal]>;
+	i: specialize TChars<['a','b']>;
+	j: specialize TQWord<10>;
+	k: specialize TPointer<nil>;
+begin
+end.
diff --git a/tests/test/tgenconst10.pp b/tests/test/tgenconst10.pp
new file mode 100644
index 0000000000..f05a27718c
--- /dev/null
+++ b/tests/test/tgenconst10.pp
@@ -0,0 +1,13 @@
+{%FAIL}
+
+{$mode objfpc}
+
+program tgenconst10;
+
+type
+	generic TByte<T> = record end;
+	
+var
+	a: specialize TByte<10>;
+begin
+end.
diff --git a/tests/test/tgenconst11.pp b/tests/test/tgenconst11.pp
new file mode 100644
index 0000000000..ea409bec9b
--- /dev/null
+++ b/tests/test/tgenconst11.pp
@@ -0,0 +1,21 @@
+{%FAIL}
+{$mode objfpc}
+program tgenconst11;
+type
+	TEnum = (aaa,bbb,ccc,ddd);
+type
+	generic TConst<const U> = class end;
+
+var
+	a:specialize TConst<10>;
+	b:specialize TConst<10.5>;
+	c:specialize TConst<'string'>;
+	d:specialize TConst<[1,2,3]>;
+	e:specialize TConst<[aaa,bbb,ccc]>;
+begin
+	a:=specialize TConst<20>.Create;
+	b:=specialize TConst<10.1>.Create;
+	c:=specialize TConst<'_string'>.Create;
+	d:=specialize TConst<[1,2,3,4]>.Create;
+	e:=specialize TConst<[aaa,bbb,ccc,ddd]>.Create;
+end.
\ No newline at end of file
diff --git a/tests/test/tgenconst12.pp b/tests/test/tgenconst12.pp
new file mode 100644
index 0000000000..8f591f6867
--- /dev/null
+++ b/tests/test/tgenconst12.pp
@@ -0,0 +1,16 @@
+{$mode objfpc}
+program tgenconst12;
+
+type
+  generic TTest<const U> = class
+  		class procedure DoThis;
+  end;
+
+class procedure TTest.DoThis;
+begin
+end;
+
+type
+	ATest = specialize TTest<100>;
+begin 
+end.
diff --git a/tests/test/tgenconst13.pp b/tests/test/tgenconst13.pp
new file mode 100644
index 0000000000..0d5f8b1813
--- /dev/null
+++ b/tests/test/tgenconst13.pp
@@ -0,0 +1,20 @@
+{$mode objfpc}
+program tgenconst13;
+type
+	TEnum = (aaa,bbb,ccc);
+type
+	generic TConst<const U> = class end;
+
+var
+	a:specialize TConst<10>;
+	b:specialize TConst<10.5>;
+	c:specialize TConst<'string'>;
+	d:specialize TConst<[1,2,3]>;
+	e:specialize TConst<[aaa,bbb,ccc]>;
+begin
+	a:=specialize TConst<10>.Create;
+	b:=specialize TConst<10.5>.Create;
+	c:=specialize TConst<'string'>.Create;
+	d:=specialize TConst<[1,2,3]>.Create;
+	e:=specialize TConst<[aaa,bbb,ccc]>.Create;
+end.
diff --git a/tests/test/tgenconst14.pp b/tests/test/tgenconst14.pp
new file mode 100644
index 0000000000..7f98086630
--- /dev/null
+++ b/tests/test/tgenconst14.pp
@@ -0,0 +1,29 @@
+{$mode objfpc}
+{$modeswitch advancedrecords}
+program tgenconst14;
+
+type
+  generic TBinaryOp<const I: Integer> = record
+    const
+    	d0 = I + I;
+    	d1 = I - I; 
+    	d2 = I * I; 
+    	d3 = I / I; 
+    	d4 = I div I; 
+    	d5 = I mod I; 
+    	d6 = I and I;
+    	d7 = I or I;
+  end;
+
+var
+	op: specialize TBinaryOp<100>;
+begin
+	writeln(op.d0);
+	writeln(op.d1);
+	writeln(op.d2);
+	writeln(op.d3:1:1);
+	writeln(op.d4);
+	writeln(op.d5);
+	writeln(op.d6);
+	writeln(op.d7);
+end.
\ No newline at end of file
diff --git a/tests/test/tgenconst15.pp b/tests/test/tgenconst15.pp
new file mode 100644
index 0000000000..56744cd0a7
--- /dev/null
+++ b/tests/test/tgenconst15.pp
@@ -0,0 +1,30 @@
+{$mode objfpc}
+{$modeswitch advancedrecords}
+program tgenconst15;
+
+type
+	kNames = set of (Blaise, Pascal);
+  generic TSet<const I: kNames> = record
+    const c = I;
+  end;
+  generic TString<const I: String> = record
+    const c = I;
+  end;
+  generic TWideString<const I: WideString> = record
+    const c = I;
+  end;
+  generic TSingle<const I: Single> = record
+    const c = I; 
+  end;
+  generic TDouble<const I: Double> = record
+    const c = I; 
+  end;
+  generic TReal<const I: Real> = record
+    const c = I; 
+  end;
+
+var
+	a0: specialize TReal<100>;
+begin
+	writeln(a0.c);
+end.
\ No newline at end of file
diff --git a/tests/test/tgenconst16.pp b/tests/test/tgenconst16.pp
new file mode 100644
index 0000000000..275867ce25
--- /dev/null
+++ b/tests/test/tgenconst16.pp
@@ -0,0 +1,86 @@
+{$mode objfpc}
+{$modeswitch advancedrecords}
+program tgenconst16;
+
+type
+  Day = (mon,tue,wed,thu,fri,sat,sun);  
+  Days = set of Day;  
+  generic TSet<const I: Days> = record
+    const
+      d0 = I + I;   // Union
+      d1 = I - I;   // Difference
+      d2 = I * I;   // Intersection
+      d3 = I >< I;  // Symmetric difference
+      d4 = I <= I;  // Contains
+      d5 = mon in I;
+  end;
+  generic TArray<const I> = record
+    type
+      t0 = array[0..I - 1] of integer;
+      t1 = array[0..high(I)] of integer;
+      t2 = array[0..low(I)] of integer;
+      t3 = array[0..sizeof(I)] of integer;
+    public
+      d0: array[0..I - 1] of integer;
+      d1: array[0..high(I)] of integer;
+      d2: array[0..low(I)] of integer;
+      d3: array[0..sizeof(I)] of integer;
+  end;
+  generic TUnaryOp<const I> = record
+    const
+      d0 = -I;
+      d1 = +I;
+      d2 = not I;
+  end;
+  generic TBinaryOp<const I> = record
+    const
+      // Arithmetic operators
+      // https://freepascal.org/docs-html/ref/refsu45.html
+      d0 = I + I;
+      d1 = I - I;
+      d2 = I * I; 
+      d3 = I / I; 
+      d4 = I div I; 
+      d5 = I mod I; 
+      // Boolean operators
+      // https://freepascal.org/docs-html/ref/refsu47.html
+      d6 = I and I;
+      d7 = I or I;
+      d8 = I xor I;
+      // Logical operators
+      // https://freepascal.org/docs-html/ref/refsu46.html
+      d9 = I shl I;
+      d10 = I shr I;
+      d11 = I << I;
+      d12 = I >> I;
+      // Relational operators
+      // https://freepascal.org/docs-html/ref/refsu50.html#x153-17500012.8.6
+      d13 = I <> I;
+      d14 = I < I;
+      d15 = I > I;
+      d16 = I <= I;
+      d17 = I >= I;
+      d18 = I = I;
+  end;
+  generic TOther<const I> = record
+    procedure DoThis(param: integer = I);
+  end;
+
+procedure TOther.DoThis(param: integer = I);
+begin
+  writeln(param, ' default:', I);
+end;
+
+var
+  t0: specialize TBinaryOp<100>;
+  t1: specialize TOther<100>;
+begin
+  //writeln(op.d0);
+  //writeln(op.d1);
+  //writeln(op.d2);
+  //writeln(op.d3:1:1);
+  //writeln(op.d4);
+  //writeln(op.d5);
+  //writeln(op.d6);
+  //writeln(op.d7);
+end.
\ No newline at end of file
diff --git a/tests/test/tgenconst17.pp b/tests/test/tgenconst17.pp
new file mode 100644
index 0000000000..26dc2ee21f
--- /dev/null
+++ b/tests/test/tgenconst17.pp
@@ -0,0 +1,36 @@
+{$mode objfpc}
+{$modeswitch advancedrecords}
+program tgenconst17;
+
+type
+  generic TUnaryOp<const I: integer> = record
+    const
+      d0 = -I;
+      d1 = +I;
+      d2 = not I;
+  end;
+  generic TBinaryOp<const I: integer> = record
+    const
+      d0 = I + I;
+      d1 = I - I;
+      d2 = I * I; 
+      d3 = I / I; 
+      d4 = I div I; 
+      d5 = I mod I; 
+      d6 = I and I;
+      d7 = I or I;
+      d8 = I xor I;
+      d9 = I shl I;
+      d10 = I shr I;
+      d11 = I << I;
+      d12 = I >> I;
+      d13 = I <> I;
+      d14 = I < I;
+      d15 = I > I;
+      d16 = I <= I;
+      d17 = I >= I;
+      d18 = I = I;
+  end;
+
+begin
+end.
\ No newline at end of file
diff --git a/tests/test/tgenconst18.pp b/tests/test/tgenconst18.pp
new file mode 100644
index 0000000000..a4ba526803
--- /dev/null
+++ b/tests/test/tgenconst18.pp
@@ -0,0 +1,12 @@
+{%FAIL}
+{$mode objfpc}
+{$modeswitch advancedrecords}
+program tgenconst18;
+
+type
+  generic TInt<const I: string> = record
+    const c = I div I;
+  end;
+
+begin
+end.
\ No newline at end of file
diff --git a/tests/test/tgenconst2.pp b/tests/test/tgenconst2.pp
new file mode 100644
index 0000000000..aa3a960634
--- /dev/null
+++ b/tests/test/tgenconst2.pp
@@ -0,0 +1,12 @@
+{$mode objfpc}
+program tgenconst2;
+
+type
+	generic TStuff1<T1,T2;const U1,U2> = record end;
+	generic TStuff2<T1,T2;const U1,U2:integer> = record end;
+	
+var
+	a: specialize TStuff1<integer,string,10,'string'>;
+	b: specialize TStuff2<integer,string,10,10>;
+begin
+end.
diff --git a/tests/test/tgenconst3.pp b/tests/test/tgenconst3.pp
new file mode 100644
index 0000000000..aea0e307e2
--- /dev/null
+++ b/tests/test/tgenconst3.pp
@@ -0,0 +1,16 @@
+{$mode objfpc}
+{$modeswitch advancedrecords}
+program tgenconst3;
+
+type
+	generic TList<T;const U:integer> = record
+		const
+			max = U;
+		public
+			m_list: array[0..max-1] of T;
+	end;
+
+var
+	list: specialize TList<integer,128>;
+begin
+end.
diff --git a/tests/test/tgenconst4.pp b/tests/test/tgenconst4.pp
new file mode 100644
index 0000000000..a1fae00c43
--- /dev/null
+++ b/tests/test/tgenconst4.pp
@@ -0,0 +1,11 @@
+{$mode objfpc}
+program tgenconst4;
+
+generic procedure DoThis<T;const U:string>(msg:string = U);
+begin
+	writeln(msg, ' sizeof:',sizeof(t), ' default: ', U);
+end;
+
+begin
+	specialize DoThis<integer,'genparam'>('hello world');
+end.
diff --git a/tests/test/tgenconst5.pp b/tests/test/tgenconst5.pp
new file mode 100644
index 0000000000..63514a976c
--- /dev/null
+++ b/tests/test/tgenconst5.pp
@@ -0,0 +1,24 @@
+{$mode objfpc}
+program tgenconst5;
+
+type
+	generic THelperA<const U:integer> = record
+		list: array[0..U-1] of byte;
+	end;
+
+type
+	generic THelperB<T> = record
+		value: T;
+	end;
+
+type
+	generic TList<T; const U:integer> = record
+		helperA: specialize THelperA<U>;
+		helperB: specialize THelperB<T>;
+	end;
+
+var
+	list: specialize TList<integer,32>;
+begin
+	writeln('sizeof:',sizeof(list));
+end.
diff --git a/tests/test/tgenconst6.pp b/tests/test/tgenconst6.pp
new file mode 100644
index 0000000000..3ee3785423
--- /dev/null
+++ b/tests/test/tgenconst6.pp
@@ -0,0 +1,21 @@
+{$mode delphi}
+program tgenconst6;
+
+type
+	TList<T;const U> = class
+		list: array[0..U-1] of T;
+		function capacity: integer;
+	end;
+
+function TList<T,U>.capacity: integer;
+begin
+	result := U;	
+end;	
+
+var
+	nums:TList<integer,16>;
+	strs:TList<string,16>;
+begin
+	nums := TList<integer,16>.Create;
+	strs := TList<string,16>.Create;
+end.
diff --git a/tests/test/tgenconst7.pp b/tests/test/tgenconst7.pp
new file mode 100644
index 0000000000..9d8e81ef05
--- /dev/null
+++ b/tests/test/tgenconst7.pp
@@ -0,0 +1,11 @@
+{%FAIL}
+{$mode objfpc}
+program tgenconst7;
+
+type
+	generic TInteger<const U: integer> = record end;
+
+var
+	a: specialize TInteger<'string'>;
+begin
+end.
diff --git a/tests/test/tgenconst8.pp b/tests/test/tgenconst8.pp
new file mode 100644
index 0000000000..75844f7181
--- /dev/null
+++ b/tests/test/tgenconst8.pp
@@ -0,0 +1,11 @@
+{%FAIL}
+{$mode objfpc}
+program tgenconst8;
+
+type
+	generic TByte<const U: Byte> = record end;
+	
+var
+	a: specialize TByte<300>;
+begin
+end.
diff --git a/tests/test/tgenconst9.pp b/tests/test/tgenconst9.pp
new file mode 100644
index 0000000000..939cb90302
--- /dev/null
+++ b/tests/test/tgenconst9.pp
@@ -0,0 +1,11 @@
+{%FAIL}
+{$mode objfpc}
+program tgenconst9;
+
+type
+	generic TByte<const U: Byte> = record end;
+	
+var
+	a: specialize TByte<string>;
+begin
+end.
-- 
2.17.2 (Apple Git-113)

From c80227ed7597385d240aa7bdc1556798aa15ec20 Mon Sep 17 00:00:00 2001
From: Ryan Joseph <genericptr@gmail.com>
Date: Tue, 6 Nov 2018 13:58:49 +0700
Subject: [PATCH] constants in generics

---
 .gitignore                         |  23 +
 compiler/defcmp.pas                |   9 +-
 compiler/htypechk.pas              |   2 +-
 compiler/ncon.pas                  |  42 +-
 compiler/nmat.pas                  |   5 +-
 compiler/node.pas                  |  22 +-
 compiler/nset.pas                  |   7 +-
 compiler/pdecl.pas                 |  53 ++-
 compiler/pdecvar.pas               |   4 +
 compiler/pexpr.pas                 |  11 +-
 compiler/pgentype.pas              |   8 +-
 compiler/pgenutil.pas              | 693 ++++++++++++++++++++---------
 compiler/ppu.pas                   |   2 +-
 compiler/ptype.pas                 |   4 +-
 compiler/symconst.pas              |  12 +-
 compiler/symdef.pas                |  22 +-
 compiler/symsym.pas                |  22 +-
 compiler/symtable.pas              |   2 +-
 compiler/utils/ppuutils/ppudump.pp |   3 +-
 tests/test/tgenconst1.pp           |  33 ++
 tests/test/tgenconst10.pp          |  13 +
 tests/test/tgenconst11.pp          |  21 +
 tests/test/tgenconst12.pp          |  16 +
 tests/test/tgenconst13.pp          |  20 +
 tests/test/tgenconst14.pp          |  29 ++
 tests/test/tgenconst15.pp          |  30 ++
 tests/test/tgenconst16.pp          |  86 ++++
 tests/test/tgenconst17.pp          |  36 ++
 tests/test/tgenconst18.pp          |  12 +
 tests/test/tgenconst2.pp           |  12 +
 tests/test/tgenconst3.pp           |  16 +
 tests/test/tgenconst4.pp           |  11 +
 tests/test/tgenconst5.pp           |  24 +
 tests/test/tgenconst6.pp           |  21 +
 tests/test/tgenconst7.pp           |  11 +
 tests/test/tgenconst8.pp           |  11 +
 tests/test/tgenconst9.pp           |  11 +
 37 files changed, 1097 insertions(+), 262 deletions(-)
 create mode 100644 .gitignore
 create mode 100644 tests/test/tgenconst1.pp
 create mode 100644 tests/test/tgenconst10.pp
 create mode 100644 tests/test/tgenconst11.pp
 create mode 100644 tests/test/tgenconst12.pp
 create mode 100644 tests/test/tgenconst13.pp
 create mode 100644 tests/test/tgenconst14.pp
 create mode 100644 tests/test/tgenconst15.pp
 create mode 100644 tests/test/tgenconst16.pp
 create mode 100644 tests/test/tgenconst17.pp
 create mode 100644 tests/test/tgenconst18.pp
 create mode 100644 tests/test/tgenconst2.pp
 create mode 100644 tests/test/tgenconst3.pp
 create mode 100644 tests/test/tgenconst4.pp
 create mode 100644 tests/test/tgenconst5.pp
 create mode 100644 tests/test/tgenconst6.pp
 create mode 100644 tests/test/tgenconst7.pp
 create mode 100644 tests/test/tgenconst8.pp
 create mode 100644 tests/test/tgenconst9.pp

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000000..64fdb156d0
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,23 @@
+# files
+pp
+fpmake
+rtl/darwin/fpcmade.x86_64-darwin
+fpmake_proc1 copy.inc
+tests/*.x86_64-darwin
+rtl/Package.fpc
+tests/createlst
+tests/gparmake
+
+# directories
+lazbuild/
+x86_64-darwin/
+tests/tstunits/
+tests/utils
+
+# patterns
+*.app
+*.o
+*.ppu
+*.fpm
+*.rsj
+*.lst
\ No newline at end of file
diff --git a/compiler/defcmp.pas b/compiler/defcmp.pas
index 3f5882f762..793dbbbe76 100644
--- a/compiler/defcmp.pas
+++ b/compiler/defcmp.pas
@@ -175,7 +175,6 @@ implementation
       symtable,symsym,symcpu,
       defutil,symutil;
 
-
     function compare_defs_ext(def_from,def_to : tdef;
                               fromtreetype : tnodetype;
                               var doconv : tconverttype;
@@ -337,9 +336,13 @@ implementation
                        internalerror(2012091302);
                      symfrom:=ttypesym(tstoreddef(def_from).genericparas[i]);
                      symto:=ttypesym(tstoreddef(def_to).genericparas[i]);
-                     if not (symfrom.typ=typesym) or not (symto.typ=typesym) then
+                     if not (symfrom.typ in [typesym,constsym]) or not (symto.typ in [typesym,constsym]) then
                        internalerror(2012121401);
-                     if not equal_defs(ttypesym(symfrom).typedef,ttypesym(symto).typedef) then
+                     if symto.typ <> symfrom.typ then
+                       diff:=true
+                     else if (symfrom.typ=constsym) and (symto.typ=constsym) and not equal_constsym(tconstsym(symfrom),tconstsym(symto),true) then
+                       diff:=true
+                     else if not equal_defs(ttypesym(symfrom).typedef,ttypesym(symto).typedef) then
                        diff:=true;
                      if diff then
                        break;
diff --git a/compiler/htypechk.pas b/compiler/htypechk.pas
index 07c035dc26..2358ea4b6d 100644
--- a/compiler/htypechk.pas
+++ b/compiler/htypechk.pas
@@ -2697,7 +2697,7 @@ implementation
               internalerror(2015060301);
             { check whether the given parameters are compatible
               to the def's constraints }
-            if not check_generic_constraints(pd,spezcontext.genericdeflist,spezcontext.poslist) then
+            if not check_generic_constraints(pd,spezcontext.paramlist,spezcontext.poslist) then
               exit;
             def:=generate_specialization_phase2(spezcontext,pd,false,'');
             case def.typ of
diff --git a/compiler/ncon.pas b/compiler/ncon.pas
index ae94637c28..1e203f74d6 100644
--- a/compiler/ncon.pas
+++ b/compiler/ncon.pas
@@ -279,6 +279,7 @@ implementation
         p1  : tnode;
         len : longint;
         pc  : pchar;
+        value_set : pconstset;
       begin
         p1:=nil;
         case p.consttyp of
@@ -304,18 +305,51 @@ implementation
           constwstring :
             p1:=cstringconstnode.createunistr(pcompilerwidestring(p.value.valueptr));
           constreal :
-            p1:=crealconstnode.create(pbestreal(p.value.valueptr)^,p.constdef);
+            begin
+              if sp_generic_para in p.symoptions then
+                p1:=crealconstnode.create(default(bestreal),p.constdef)
+              else
+                p1:=crealconstnode.create(pbestreal(p.value.valueptr)^,p.constdef);
+            end;
           constset :
-            p1:=csetconstnode.create(pconstset(p.value.valueptr),p.constdef);
+            begin
+              if sp_generic_para in p.symoptions then
+                begin
+                  new(value_set);
+                  p1:=csetconstnode.create(value_set,p.constdef);
+                end
+              else
+                p1:=csetconstnode.create(pconstset(p.value.valueptr),p.constdef);
+            end;
           constpointer :
-            p1:=cpointerconstnode.create(p.value.valueordptr,p.constdef);
+            begin
+              if sp_generic_para in p.symoptions then
+                p1:=cpointerconstnode.create(default(tconstptruint),p.constdef)
+              else
+                p1:=cpointerconstnode.create(p.value.valueordptr,p.constdef);
+            end;
           constnil :
             p1:=cnilnode.create;
+          { constundefined is a placeholder for unrestricted generic const params
+            so we just treat it as a nil node. }
+          constundefined :
+            begin
+              p1:=cnilnode.create;
+              p1.resultdef:=p.constdef;
+            end;
           constguid :
-            p1:=cguidconstnode.create(pguid(p.value.valueptr)^);
+            begin
+              if sp_generic_para in p.symoptions then
+                p1:=cguidconstnode.create(default(tguid))
+              else
+                p1:=cguidconstnode.create(pguid(p.value.valueptr)^);
+            end;
           else
             internalerror(200205103);
         end;
+        { transfer generic param flag from symbol to node }
+        if sp_generic_para in p.symoptions then
+          include(p1.flags,nf_generic_para);
         genconstsymtree:=p1;
       end;
 
diff --git a/compiler/nmat.pas b/compiler/nmat.pas
index 355b493da4..d10dff6128 100644
--- a/compiler/nmat.pas
+++ b/compiler/nmat.pas
@@ -129,7 +129,10 @@ implementation
               end;
             if rv = 0 then
               begin
-                Message(parser_e_division_by_zero);
+                { if the node is derived from a generic const parameter
+                  then don't issue an error }
+                if not (nf_generic_para in flags) then
+                  Message(parser_e_division_by_zero);
                 { recover }
                 tordconstnode(right).value := 1;
               end;
diff --git a/compiler/node.pas b/compiler/node.pas
index b8600000bf..33a85b1493 100644
--- a/compiler/node.pas
+++ b/compiler/node.pas
@@ -194,7 +194,8 @@ interface
           'loadparentfpn',
           'objcselectorn',
           'objcprotocoln',
-          'specializen');
+          'specializen'
+          );
 
       { a set containing all const nodes }
       nodetype_const = [ordconstn,
@@ -272,10 +273,13 @@ interface
          nf_block_with_exit,
 
          { tloadvmtaddrnode }
-         nf_ignore_for_wpo  { we know that this loadvmtaddrnode cannot be used to construct a class instance }
+         nf_ignore_for_wpo,  { we know that this loadvmtaddrnode cannot be used to construct a class instance }
 
-         { WARNING: there are now 31 elements in this type, and a set of this
-             type is written to the PPU. So before adding more than 32 elements,
+         { node is derived from generic parameter }
+         nf_generic_para
+
+         { WARNING: there are now 32 elements in this type, and a set of this
+             type is written to the PPU. So before adding more elements,
              either move some flags to specific nodes, or stream a normalset
              to the ppu
          }
@@ -983,6 +987,9 @@ implementation
     constructor tunarynode.create(t:tnodetype;l : tnode);
       begin
          inherited create(t);
+         { transfer generic paramater flag }
+         if assigned(l) and (nf_generic_para in l.flags) then
+           include(flags,nf_generic_para);
          left:=l;
       end;
 
@@ -1078,7 +1085,12 @@ implementation
     constructor tbinarynode.create(t:tnodetype;l,r : tnode);
       begin
          inherited create(t,l);
-         right:=r
+         { transfer generic paramater flag }
+         if assigned(l) and (nf_generic_para in l.flags) then
+           include(flags,nf_generic_para)
+         else if assigned(r) and (nf_generic_para in r.flags) then
+           include(flags,nf_generic_para);
+         right:=r;
       end;
 
 
diff --git a/compiler/nset.pas b/compiler/nset.pas
index 6270ec582e..bd031e6a86 100644
--- a/compiler/nset.pas
+++ b/compiler/nset.pas
@@ -239,7 +239,7 @@ implementation
            internalerror(20021126);
 
          t:=self;
-         if isbinaryoverloaded(t,[]) then
+         if isbinaryoverloaded(t,[]) then
            begin
              result:=t;
              exit;
@@ -392,8 +392,9 @@ implementation
          { both types must be compatible }
          if compare_defs(left.resultdef,right.resultdef,left.nodetype)=te_incompatible then
            IncompatibleTypes(left.resultdef,right.resultdef);
-         { Check if only when its a constant set }
-         if (left.nodetype=ordconstn) and (right.nodetype=ordconstn) then
+         { check if only when its a constant set and
+           ignore range nodes which are generic parameter derived }
+         if not (nf_generic_para in flags) and (left.nodetype=ordconstn) and (right.nodetype=ordconstn) then
           begin
             { upper limit must be greater or equal than lower limit }
             if (tordconstnode(left).value>tordconstnode(right).value) and
diff --git a/compiler/pdecl.pas b/compiler/pdecl.pas
index c5b5bcc921..d7e80b928f 100644
--- a/compiler/pdecl.pas
+++ b/compiler/pdecl.pas
@@ -126,9 +126,14 @@ implementation
              end;
            setconstn :
              begin
-               new(ps);
-               ps^:=tsetconstnode(p).value_set^;
-               hp:=cconstsym.create_ptr(orgname,constset,ps,p.resultdef);
+               if nf_generic_para in p.flags then
+                 hp:=cconstsym.create_ptr(orgname,constset,nil,p.resultdef)
+               else
+                 begin
+                   new(ps);
+                   ps^:=tsetconstnode(p).value_set^;
+                   hp:=cconstsym.create_ptr(orgname,constset,ps,p.resultdef);
+                 end;
              end;
            pointerconstn :
              begin
@@ -141,18 +146,18 @@ implementation
            typen :
              begin
                if is_interface(p.resultdef) then
-                begin
-                  if assigned(tobjectdef(p.resultdef).iidguid) then
-                   begin
-                     new(pg);
-                     pg^:=tobjectdef(p.resultdef).iidguid^;
-                     hp:=cconstsym.create_ptr(orgname,constguid,pg,p.resultdef);
-                   end
-                  else
-                   Message1(parser_e_interface_has_no_guid,tobjectdef(p.resultdef).objrealname^);
-                end
-               else
-                Message(parser_e_illegal_expression);
+                 begin
+                   if assigned(tobjectdef(p.resultdef).iidguid) then
+                     begin
+                       new(pg);
+                       pg^:=tobjectdef(p.resultdef).iidguid^;
+                       hp:=cconstsym.create_ptr(orgname,constguid,pg,p.resultdef);
+                     end
+                    else
+                      Message1(parser_e_interface_has_no_guid,tobjectdef(p.resultdef).objrealname^);
+                 end
+               else 
+                 Message(parser_e_illegal_expression);
              end;
            inlinen:
              begin
@@ -177,8 +182,19 @@ implementation
                end;
              end;
            else
-             Message(parser_e_illegal_expression);
+             begin
+               { the node is from a generic parameter constant and is 
+                 untyped so we need to pass a placeholder constant 
+                 instead of givng an error }
+               if nf_generic_para in p.flags then 
+                 hp:=cconstsym.create_ord(orgname,constnil,0,p.resultdef)
+               else
+                 Message(parser_e_illegal_expression);
+             end;
         end;
+        { transfer generic param flag from node to symbol }
+        if nf_generic_para in p.flags then
+          include(hp.symoptions,sp_generic_para);
         current_tokenpos:=storetokenpos;
         p.free;
         readconstant:=hp;
@@ -507,8 +523,9 @@ implementation
                { we are not freeing the type parameters, so register them }
                for i:=0 to generictypelist.count-1 do
                  begin
-                    ttypesym(generictypelist[i]).register_sym;
-                    tstoreddef(ttypesym(generictypelist[i]).typedef).register_def;
+                    tstoredsym(generictypelist[i]).register_sym;
+                    if tstoredsym(generictypelist[i]).typ=typesym then
+                      tstoreddef(ttypesym(generictypelist[i]).typedef).register_def;
                  end;
 
                str(generictypelist.Count,s);
diff --git a/compiler/pdecvar.pas b/compiler/pdecvar.pas
index 4d39397e46..8121d87853 100644
--- a/compiler/pdecvar.pas
+++ b/compiler/pdecvar.pas
@@ -1675,6 +1675,10 @@ implementation
                    end;
                end;
 
+             { field type is a generic param so set a flag in the struct }
+             if assigned(hdef.typesym) and (sp_generic_para in hdef.typesym.symoptions) then
+               include(current_structdef.defoptions,df_has_generic_fields);
+
              { Process procvar directives }
              if maybe_parse_proc_directives(hdef) then
                semicoloneaten:=true;
diff --git a/compiler/pexpr.pas b/compiler/pexpr.pas
index bc0606ed4b..e6d9633ebd 100644
--- a/compiler/pexpr.pas
+++ b/compiler/pexpr.pas
@@ -446,6 +446,9 @@ implementation
                   { no packed bit support for these things }
                   if l=in_bitsizeof_x then
                     statement_syssym:=caddnode.create(muln,statement_syssym,cordconstnode.create(8,sinttype,true));
+                  { type sym is a generic parameter }
+                  if assigned(p1.resultdef.typesym) and (sp_generic_para in p1.resultdef.typesym.symoptions) then
+                    include(statement_syssym.flags,nf_generic_para);
                 end
               else
                begin
@@ -466,6 +469,9 @@ implementation
                    end
                  else
                    statement_syssym:=cordconstnode.create(p1.resultdef.packedbitsize,sinttype,true);
+                 { type def is a struct with generic fields }
+                 if df_has_generic_fields in p1.resultdef.defoptions then
+                    include(statement_syssym.flags,nf_generic_para);
                  { p1 not needed !}
                  p1.destroy;
                end;
@@ -4078,7 +4084,10 @@ implementation
                 gendef:=generate_specialization_phase2(spezcontext,tstoreddef(gendef),false,'');
                 spezcontext.free;
                 spezcontext:=nil;
-                gensym:=gendef.typesym;
+                if gendef.typ=errordef then
+                  gensym:=generrorsym
+                else
+                  gensym:=gendef.typesym;
               end;
             procdef:
               begin
diff --git a/compiler/pgentype.pas b/compiler/pgentype.pas
index b2847c78f6..85270df256 100644
--- a/compiler/pgentype.pas
+++ b/compiler/pgentype.pas
@@ -28,7 +28,7 @@ interface
 uses
   cclasses,
   globtype,
-  symtype,symbase;
+  symconst,symtype,symbase;
 
 const
   inline_specialization_block_types = [bt_type,bt_var_type,bt_const_type,bt_body];
@@ -42,7 +42,7 @@ type
 
   tspecializationcontext=class
   public
-    genericdeflist : tfpobjectlist;
+    paramlist : tfpobjectlist;
     poslist : tfplist;
     prettyname : ansistring;
     specializename : ansistring;
@@ -58,7 +58,7 @@ implementation
 
 constructor tspecializationcontext.create;
 begin
-  genericdeflist:=tfpobjectlist.create(false);
+  paramlist:=tfpobjectlist.create(false);
   poslist:=tfplist.create;
 end;
 
@@ -66,7 +66,7 @@ destructor tspecializationcontext.destroy;
 var
   i : longint;
 begin
-  genericdeflist.free;
+  paramlist.free;
   for i:=0 to poslist.count-1 do
     dispose(pfileposinfo(poslist[i]));
   poslist.free;
diff --git a/compiler/pgenutil.pas b/compiler/pgenutil.pas
index 7760a4e134..ac6e59ce98 100644
--- a/compiler/pgenutil.pas
+++ b/compiler/pgenutil.pas
@@ -42,9 +42,9 @@ uses
     function generate_specialization_phase1(out context:tspecializationcontext;genericdef:tdef;symname:string):tdef;inline;
     function generate_specialization_phase1(out context:tspecializationcontext;genericdef:tdef;parsedtype:tdef;symname:string;parsedpos:tfileposinfo):tdef;
     function generate_specialization_phase2(context:tspecializationcontext;genericdef:tstoreddef;parse_class_parent:boolean;_prettyname:ansistring):tdef;
-    function check_generic_constraints(genericdef:tstoreddef;paradeflist:tfpobjectlist;poslist:tfplist):boolean;
+    function check_generic_constraints(genericdef:tstoreddef;paramlist:tfpobjectlist;poslist:tfplist):boolean;
     function parse_generic_parameters(allowconstraints:boolean):tfphashobjectlist;
-    function parse_generic_specialization_types(genericdeflist:tfpobjectlist;poslist:tfplist;out prettyname,specializename:ansistring):boolean;
+    function parse_generic_specialization_types(paramlist:tfpobjectlist;poslist:tfplist;out prettyname,specializename:ansistring):boolean;
     procedure insert_generic_parameter_types(def:tstoreddef;genericdef:tstoreddef;genericlist:tfphashobjectlist);
     procedure maybe_insert_generic_rename_symbol(const name:tidstring;genericlist:tfphashobjectlist);
     function generate_generic_name(const name:tidstring;specializename:ansistring;owner_hierarchy:string):tidstring;
@@ -63,18 +63,163 @@ implementation
 
 uses
   { common }
-  cutils,fpccrc,
+  sysutils,cutils,fpccrc,
   { global }
-  globals,tokens,verbose,finput,
+  globals,tokens,verbose,finput,constexp,
   { symtable }
-  symconst,symsym,symtable,defcmp,procinfo,
+  symconst,symsym,symtable,defcmp,defutil,procinfo,
   { modules }
   fmodule,
-  node,nobj,
+  node,nobj,ncon,
   { parser }
   scanner,
   pbase,pexpr,pdecsub,ptype,psub;
 
+  type
+    tdeftypeset = set of tdeftyp;
+  const
+    tgeneric_param_const_types : tdeftypeset = [orddef,stringdef,arraydef,floatdef,setdef,pointerdef,undefineddef];
+    tgeneric_param_nodes : tnodetypeset = [typen,ordconstn,stringconstn,realconstn,setconstn,niln];
+
+    function get_generic_param_def(sym:tsym):tdef;
+      begin
+        if sym.typ=constsym then
+          result:=tconstsym(sym).constdef
+        else
+          result:=ttypesym(sym).typedef;
+      end;
+
+    function is_generic_param_const(sym:tsym):boolean;
+      begin
+        if sym.typ=constsym then
+          result:=tconstsym(sym).consttyp<>constundefined
+        else
+          result:=false;
+      end;
+
+    function compare_orddef_by_range(param1,param2:torddef;value:tconstvalue):boolean;
+      begin
+        if (value.len<param2.low) or (value.len>param2.high) then
+          result:=false
+        else
+          result:=true;
+      end;
+
+    function compare_generic_params(param1,param2:tdef;constparamsym:tconstsym):boolean;
+      begin
+        if (param1.typ=orddef) and (param2.typ=orddef) then
+          begin
+            if is_boolean(param2) then
+              result:=is_boolean(param1)
+            else if is_char(param2) then
+              result:=is_char(param1)
+            else if compare_orddef_by_range(torddef(param1),torddef(param2),constparamsym.value) then
+              result:=true
+            else
+              result:=false;
+          end
+        { arraydef is string constant so it's compatible with stringdef }
+        else if (param1.typ=arraydef) and (param2.typ=stringdef) then
+          result:=true
+        { integer ords are compatible with float }
+        else if (param1.typ=orddef) and is_integer(param1) and (param2.typ=floatdef) then
+          result:=true
+        { undefined def is compatible with all types }
+        else if param2.typ=undefineddef then
+          result:=true
+        { sets require stricter checks }
+        else if is_set(param2) then
+          result:=equal_defs(param1,param2)
+        else
+          result:=param1.typ=param2.typ;
+      end;
+
+    function create_generic_constsym(fromdef:tdef;node:tnode;out prettyname:string):tconstsym;
+      const
+        undefinedname = 'undefined';
+      var
+        sym : tconstsym;
+        setdef : tsetdef;
+        enumsym : tsym;
+        enumname : string;
+        sp : pchar;
+        ps : ^tconstset;
+        pd : ^bestreal;
+        i : integer;
+      begin
+        if node=nil then
+          begin
+            sym:=cconstsym.create_undefined(undefinedname,fromdef);
+            sym.owner:=fromdef.owner;
+            prettyname:='';
+            result:=sym;
+            exit;
+          end;
+        case node.nodetype of
+          ordconstn:
+            begin
+              sym:=cconstsym.create_ord(undefinedname,constord,tordconstnode(node).value,fromdef);
+              prettyname:=inttostr(tordconstnode(node).value.svalue);
+            end;
+          stringconstn:
+            begin
+              getmem(sp,tstringconstnode(node).len+1);
+              move(tstringconstnode(node).value_str^,sp^,tstringconstnode(node).len+1);
+              sym:=cconstsym.create_string(undefinedname,conststring,sp,tstringconstnode(node).len,fromdef);
+              prettyname:=''''+tstringconstnode(node).value_str+'''';
+            end;
+          realconstn:
+            begin
+              new(pd);
+              pd^:=trealconstnode(node).value_real;
+              sym:=cconstsym.create_ptr(undefinedname,constreal,pd,fromdef);
+              prettyname:=floattostr(trealconstnode(node).value_real);
+            end;
+          setconstn:
+            begin
+              new(ps);
+              ps^:=tsetconstnode(node).value_set^;
+              sym:=cconstsym.create_ptr(undefinedname,constset,ps,fromdef);
+              setdef:=tsetdef(tsetconstnode(node).resultdef);
+              prettyname:='[';
+              for i := setdef.setbase to setdef.setmax do
+                if i in tsetconstnode(node).value_set^ then
+                  begin
+                    if setdef.elementdef.typ=enumdef then
+                      enumsym:=tenumdef(setdef.elementdef).int2enumsym(i)
+                    else
+                      enumsym:=nil;
+                    if assigned(enumsym) then
+                      enumname:=enumsym.realname
+                    else if setdef.elementdef.typ=orddef then
+                      begin
+                        if torddef(setdef.elementdef).ordtype=uchar then
+                          enumname:=chr(i)
+                        else
+                          enumname:=tostr(i);
+                      end
+                    else
+                      enumname:=tostr(i);
+                    if length(prettyname) > 1 then
+                      prettyname:=prettyname+','+enumname
+                    else
+                      prettyname:=prettyname+enumname;
+                  end;
+              prettyname:=prettyname+']';
+            end;
+          niln:
+            begin
+              { only "nil" is available for pointer constants }
+              sym:=cconstsym.create_ord(undefinedname,constnil,0,fromdef);
+              prettyname:='nil';
+            end;
+          else
+            internalerror(2019021601);
+        end;
+        { the sym needs an owner for later checks so us the typeparam owner }
+        sym.owner:=fromdef.owner;
+        result:=sym;
+      end;
 
     procedure maybe_add_waiting_unit(tt:tdef);
       var
@@ -104,203 +249,232 @@ uses
           end;
       end;
 
-    function check_generic_constraints(genericdef:tstoreddef;paradeflist:tfpobjectlist;poslist:tfplist):boolean;
+    function check_generic_constraints(genericdef:tstoreddef;paramlist:tfpobjectlist;poslist:tfplist):boolean;
       var
         i,j,
         intfcount : longint;
         formaldef,
         paradef : tstoreddef;
+        genparadef : tdef;
         objdef,
         paraobjdef,
         formalobjdef : tobjectdef;
         intffound : boolean;
         filepos : tfileposinfo;
+        //paratype : tconsttyp;
+        is_const : boolean;
       begin
         { check whether the given specialization parameters fit to the eventual
           constraints of the generic }
         if not assigned(genericdef.genericparas) or (genericdef.genericparas.count=0) then
           internalerror(2012101001);
-        if genericdef.genericparas.count<>paradeflist.count then
+        if genericdef.genericparas.count<>paramlist.count then
           internalerror(2012101002);
-        if paradeflist.count<>poslist.count then
+        if paramlist.count<>poslist.count then
           internalerror(2012120801);
         result:=true;
         for i:=0 to genericdef.genericparas.count-1 do
           begin
             filepos:=pfileposinfo(poslist[i])^;
-            formaldef:=tstoreddef(ttypesym(genericdef.genericparas[i]).typedef);
-            if formaldef.typ=undefineddef then
-              { the parameter is of unspecified type, so no need to check }
-              continue;
-            if not (df_genconstraint in formaldef.defoptions) or
-                not assigned(formaldef.genconstraintdata) then
-              internalerror(2013021602);
-            paradef:=tstoreddef(paradeflist[i]);
-            { undefineddef is compatible with anything }
-            if formaldef.typ=undefineddef then
-              continue;
-            if paradef.typ<>formaldef.typ then
+            paradef:=tstoreddef(get_generic_param_def(tsym(paramlist[i])));
+            is_const:=is_generic_param_const(tsym(paramlist[i]));
+            genparadef:=genericdef.get_generic_param_def(i);
+            { validate const params }
+            if not genericdef.is_generic_param_const(i) and is_const then
               begin
-                case formaldef.typ of
-                  recorddef:
-                    { delphi has own fantasy about record constraint
-                      (almost non-nullable/non-nilable value type) }
-                    if m_delphi in current_settings.modeswitches then
-                      case paradef.typ of
-                        floatdef,enumdef,orddef:
-                          continue;
-                        objectdef:
-                          if tobjectdef(paradef).objecttype=odt_object then
-                            continue
-                          else
-                            MessagePos(filepos,type_e_record_type_expected);
+                MessagePos(filepos,type_e_mismatch);
+                exit(false);
+              end
+            else if genericdef.is_generic_param_const(i) then
+              begin
+                { param type mismatch (type <> const) }
+                 if genericdef.is_generic_param_const(i) <> is_const then
+                   begin
+                    MessagePos(filepos,type_e_mismatch);
+                    exit(false);
+                  end;
+                { type constrained param doesn't match type }
+                if not compare_generic_params(paradef,genericdef.get_generic_param_def(i),tconstsym(paramlist[i])) then
+                  begin
+                    MessagePos2(filepos,type_e_incompatible_types,FullTypeName(paradef,genparadef),FullTypeName(genparadef,paradef));
+                    exit(false);
+                  end;
+              end;
+            { test constraints for non-const params }
+            if not genericdef.is_generic_param_const(i) then
+              begin
+                formaldef:=tstoreddef(ttypesym(genericdef.genericparas[i]).typedef);
+                if formaldef.typ=undefineddef then
+                  { the parameter is of unspecified type, so no need to check }
+                  continue;
+                if not (df_genconstraint in formaldef.defoptions) or
+                    not assigned(formaldef.genconstraintdata) then
+                  internalerror(2013021602);
+                { undefineddef is compatible with anything }
+                if formaldef.typ=undefineddef then
+                  continue;
+                if paradef.typ<>formaldef.typ then
+                  begin
+                    case formaldef.typ of
+                      recorddef:
+                        { delphi has own fantasy about record constraint
+                          (almost non-nullable/non-nilable value type) }
+                        if m_delphi in current_settings.modeswitches then
+                          case paradef.typ of
+                            floatdef,enumdef,orddef:
+                              continue;
+                            objectdef:
+                              if tobjectdef(paradef).objecttype=odt_object then
+                                continue
+                              else
+                                MessagePos(filepos,type_e_record_type_expected);
+                            else
+                              MessagePos(filepos,type_e_record_type_expected);
+                          end
                         else
                           MessagePos(filepos,type_e_record_type_expected);
-                      end
-                    else
-                      MessagePos(filepos,type_e_record_type_expected);
-                  objectdef:
-                    case tobjectdef(formaldef).objecttype of
-                      odt_class,
-                      odt_javaclass:
-                        MessagePos1(filepos,type_e_class_type_expected,paradef.typename);
-                      odt_interfacecom,
-                      odt_interfacecorba,
-                      odt_dispinterface,
-                      odt_interfacejava:
-                        MessagePos1(filepos,type_e_interface_type_expected,paradef.typename);
+                      objectdef:
+                        case tobjectdef(formaldef).objecttype of
+                          odt_class,
+                          odt_javaclass:
+                            MessagePos1(filepos,type_e_class_type_expected,paradef.typename);
+                          odt_interfacecom,
+                          odt_interfacecorba,
+                          odt_dispinterface,
+                          odt_interfacejava:
+                            MessagePos1(filepos,type_e_interface_type_expected,paradef.typename);
+                          else
+                            internalerror(2012101003);
+                        end;
+                      errordef:
+                        { ignore }
+                        ;
                       else
-                        internalerror(2012101003);
+                        internalerror(2012101004);
                     end;
-                  errordef:
-                    { ignore }
-                    ;
-                  else
-                    internalerror(2012101004);
-                end;
-                result:=false;
-              end
-            else
-              begin
-                { the paradef types are the same, so do special checks for the
-                  cases in which they are needed }
-                if formaldef.typ=objectdef then
+                    result:=false;
+                  end
+                else
                   begin
-                    paraobjdef:=tobjectdef(paradef);
-                    formalobjdef:=tobjectdef(formaldef);
-                    if not (formalobjdef.objecttype in [odt_class,odt_javaclass,odt_interfacecom,odt_interfacecorba,odt_interfacejava,odt_dispinterface]) then
-                      internalerror(2012101102);
-                    if formalobjdef.objecttype in [odt_interfacecom,odt_interfacecorba,odt_interfacejava,odt_dispinterface] then
+                    { the paradef types are the same, so do special checks for the
+                      cases in which they are needed }
+                    if formaldef.typ=objectdef then
                       begin
-                        { this is either a concerete interface or class type (the
-                          latter without specific implemented interfaces) }
-                        case paraobjdef.objecttype of
-                          odt_interfacecom,
-                          odt_interfacecorba,
-                          odt_interfacejava,
-                          odt_dispinterface:
-                            begin
-                              if (oo_is_forward in paraobjdef.objectoptions) and
-                                  (paraobjdef.objecttype=formalobjdef.objecttype) and
-                                  (df_genconstraint in formalobjdef.defoptions) and
-                                  (
-                                    (formalobjdef.objecttype=odt_interfacecom) and
-                                    (formalobjdef.childof=interface_iunknown)
-                                  )
-                                  or
-                                  (
-                                    (formalobjdef.objecttype=odt_interfacecorba) and
-                                    (formalobjdef.childof=nil)
-                                  ) then
-                                continue;
-                              if not def_is_related(paraobjdef,formalobjdef.childof) then
+                        paraobjdef:=tobjectdef(paradef);
+                        formalobjdef:=tobjectdef(formaldef);
+                        if not (formalobjdef.objecttype in [odt_class,odt_javaclass,odt_interfacecom,odt_interfacecorba,odt_interfacejava,odt_dispinterface]) then
+                          internalerror(2012101102);
+                        if formalobjdef.objecttype in [odt_interfacecom,odt_interfacecorba,odt_interfacejava,odt_dispinterface] then
+                          begin
+                            { this is either a concerete interface or class type (the
+                              latter without specific implemented interfaces) }
+                            case paraobjdef.objecttype of
+                              odt_interfacecom,
+                              odt_interfacecorba,
+                              odt_interfacejava,
+                              odt_dispinterface:
                                 begin
-                                  MessagePos2(filepos,type_e_incompatible_types,paraobjdef.typename,formalobjdef.childof.typename);
-                                  result:=false;
+                                  if (oo_is_forward in paraobjdef.objectoptions) and
+                                      (paraobjdef.objecttype=formalobjdef.objecttype) and
+                                      (df_genconstraint in formalobjdef.defoptions) and
+                                      (
+                                        (formalobjdef.objecttype=odt_interfacecom) and
+                                        (formalobjdef.childof=interface_iunknown)
+                                      )
+                                      or
+                                      (
+                                        (formalobjdef.objecttype=odt_interfacecorba) and
+                                        (formalobjdef.childof=nil)
+                                      ) then
+                                    continue;
+                                  if not def_is_related(paraobjdef,formalobjdef.childof) then
+                                    begin
+                                      MessagePos2(filepos,type_e_incompatible_types,paraobjdef.typename,formalobjdef.childof.typename);
+                                      result:=false;
+                                    end;
                                 end;
-                            end;
-                          odt_class,
-                          odt_javaclass:
-                            begin
-                              objdef:=paraobjdef;
-                              intffound:=false;
-                              while assigned(objdef) do
+                              odt_class,
+                              odt_javaclass:
                                 begin
-                                  for j:=0 to objdef.implementedinterfaces.count-1 do
-                                    if timplementedinterface(objdef.implementedinterfaces[j]).intfdef=formalobjdef.childof then
-                                      begin
-                                        intffound:=true;
+                                  objdef:=paraobjdef;
+                                  intffound:=false;
+                                  while assigned(objdef) do
+                                    begin
+                                      for j:=0 to objdef.implementedinterfaces.count-1 do
+                                        if timplementedinterface(objdef.implementedinterfaces[j]).intfdef=formalobjdef.childof then
+                                          begin
+                                            intffound:=true;
+                                            break;
+                                          end;
+                                      if intffound then
                                         break;
-                                      end;
-                                  if intffound then
-                                    break;
-                                  objdef:=objdef.childof;
+                                      objdef:=objdef.childof;
+                                    end;
+                                  result:=intffound;
+                                  if not result then
+                                    MessagePos2(filepos,parser_e_class_doesnt_implement_interface,paraobjdef.typename,formalobjdef.childof.typename);
+                                end;
+                              else
+                                begin
+                                  MessagePos1(filepos,type_e_class_or_interface_type_expected,paraobjdef.typename);
+                                  result:=false;
                                 end;
-                              result:=intffound;
-                              if not result then
-                                MessagePos2(filepos,parser_e_class_doesnt_implement_interface,paraobjdef.typename,formalobjdef.childof.typename);
-                            end;
-                          else
-                            begin
-                              MessagePos1(filepos,type_e_class_or_interface_type_expected,paraobjdef.typename);
-                              result:=false;
                             end;
-                        end;
-                      end
-                    else
-                      begin
-                        { this is either a "class" or a concrete instance with
-                          or without implemented interfaces }
-                        if not (paraobjdef.objecttype in [odt_class,odt_javaclass]) then
-                          begin
-                            MessagePos1(filepos,type_e_class_type_expected,paraobjdef.typename);
-                            result:=false;
-                            continue;
-                          end;
-                        { for forward declared classes we allow pure TObject/class declarations }
-                        if (oo_is_forward in paraobjdef.objectoptions) and
-                            (df_genconstraint in formaldef.defoptions) then
-                          begin
-                            if (formalobjdef.childof=class_tobject) and
-                                not formalobjdef.implements_any_interfaces then
-                              continue;
-                          end;
-                        if assigned(formalobjdef.childof) and
-                            not def_is_related(paradef,formalobjdef.childof) then
-                          begin
-                            MessagePos2(filepos,type_e_incompatible_types,paraobjdef.typename,formalobjdef.childof.typename);
-                            result:=false;
-                          end;
-                        intfcount:=0;
-                        for j:=0 to formalobjdef.implementedinterfaces.count-1 do
+                          end
+                        else
                           begin
-                            objdef:=paraobjdef;
-                            while assigned(objdef) do
+                            { this is either a "class" or a concrete instance with
+                              or without implemented interfaces }
+                            if not (paraobjdef.objecttype in [odt_class,odt_javaclass]) then
                               begin
-                                intffound:=assigned(
-                                             find_implemented_interface(objdef,
-                                               timplementedinterface(formalobjdef.implementedinterfaces[j]).intfdef
-                                             )
-                                           );
+                                MessagePos1(filepos,type_e_class_type_expected,paraobjdef.typename);
+                                result:=false;
+                                continue;
+                              end;
+                            { for forward declared classes we allow pure TObject/class declarations }
+                            if (oo_is_forward in paraobjdef.objectoptions) and
+                                (df_genconstraint in formaldef.defoptions) then
+                              begin
+                                if (formalobjdef.childof=class_tobject) and
+                                    not formalobjdef.implements_any_interfaces then
+                                  continue;
+                              end;
+                            if assigned(formalobjdef.childof) and
+                                not def_is_related(paradef,formalobjdef.childof) then
+                              begin
+                                MessagePos2(filepos,type_e_incompatible_types,paraobjdef.typename,formalobjdef.childof.typename);
+                                result:=false;
+                              end;
+                            intfcount:=0;
+                            for j:=0 to formalobjdef.implementedinterfaces.count-1 do
+                              begin
+                                objdef:=paraobjdef;
+                                while assigned(objdef) do
+                                  begin
+                                    intffound:=assigned(
+                                                 find_implemented_interface(objdef,
+                                                   timplementedinterface(formalobjdef.implementedinterfaces[j]).intfdef
+                                                 )
+                                               );
+                                    if intffound then
+                                      break;
+                                    objdef:=objdef.childof;
+                                  end;
                                 if intffound then
-                                  break;
-                                objdef:=objdef.childof;
+                                  inc(intfcount)
+                                else
+                                  MessagePos2(filepos,parser_e_class_doesnt_implement_interface,paraobjdef.typename,timplementedinterface(formalobjdef.implementedinterfaces[j]).intfdef.typename);
                               end;
-                            if intffound then
-                              inc(intfcount)
-                            else
-                              MessagePos2(filepos,parser_e_class_doesnt_implement_interface,paraobjdef.typename,timplementedinterface(formalobjdef.implementedinterfaces[j]).intfdef.typename);
+                            if intfcount<>formalobjdef.implementedinterfaces.count then
+                              result:=false;
                           end;
-                        if intfcount<>formalobjdef.implementedinterfaces.count then
-                          result:=false;
                       end;
                   end;
               end;
           end;
       end;
 
-
-    function parse_generic_specialization_types_internal(genericdeflist:tfpobjectlist;poslist:tfplist;out prettyname,specializename:ansistring;parsedtype:tdef;parsedpos:tfileposinfo):boolean;
+    function parse_generic_specialization_types_internal(paramlist:tfpobjectlist;poslist:tfplist;out prettyname,specializename:ansistring;parsedtype:tdef;parsedpos:tfileposinfo):boolean;
       var
         old_block_type : tblock_type;
         first : boolean;
@@ -310,9 +484,12 @@ uses
         namepart : string;
         prettynamepart : ansistring;
         module : tmodule;
+        //paramdef : tgenericparamdef;
+        constprettyname : string;
+        validparam : boolean;
       begin
         result:=true;
-        if genericdeflist=nil then
+        if paramlist=nil then
           internalerror(2012061401);
         { set the block type to type, so that the parsed type are returned as
           ttypenode (e.g. classes are in non type-compatible blocks returned as
@@ -324,7 +501,7 @@ uses
         first:=not assigned(parsedtype);
         if assigned(parsedtype) then
           begin
-            genericdeflist.Add(parsedtype);
+            paramlist.Add(parsedtype.typesym);
             module:=find_module_from_symtable(parsedtype.owner);
             if not assigned(module) then
               internalerror(2016112801);
@@ -351,7 +528,9 @@ uses
             block_type:=bt_type;
             tmpparampos:=current_filepos;
             typeparam:=factor(false,[ef_type_only]);
-            if typeparam.nodetype=typen then
+            { determine if the typeparam node is a valid type or const }
+            validparam:=typeparam.nodetype in tgeneric_param_nodes;
+            if validparam then
               begin
                 if tstoreddef(typeparam.resultdef).is_generic and
                     (
@@ -367,31 +546,47 @@ uses
                   end;
                 if typeparam.resultdef.typ<>errordef then
                   begin
-                    if not assigned(typeparam.resultdef.typesym) then
+                    if (typeparam.nodetype = typen) and not assigned(typeparam.resultdef.typesym) then
                       message(type_e_generics_cannot_reference_itself)
-                    else if (typeparam.resultdef.typ<>errordef) then
+                    else 
+                    if (typeparam.resultdef.typ<>errordef) then
                       begin
-                        genericdeflist.Add(typeparam.resultdef);
+                        { all non-type nodes are considered const }
+                        if typeparam.nodetype <> typen then
+                          paramlist.Add(create_generic_constsym(typeparam.resultdef,typeparam,constprettyname))
+                        else
+                          begin
+                            constprettyname:='';
+                            paramlist.Add(typeparam.resultdef.typesym);
+                          end;
                         module:=find_module_from_symtable(typeparam.resultdef.owner);
                         if not assigned(module) then
                           internalerror(2016112802);
                         namepart:='_$'+hexstr(module.moduleid,8)+'$$'+typeparam.resultdef.unique_id_str;
+                        if constprettyname <> '' then
+                          namepart:=namepart+'$$'+constprettyname;
                         { we use the full name of the type to uniquely identify it }
-                        if (symtablestack.top.symtabletype=parasymtable) and
-                            (symtablestack.top.defowner.typ=procdef) and
-                            (typeparam.resultdef.owner=symtablestack.top) then
-                          begin
-                            { special handling for specializations inside generic function declarations }
-                            prettynamepart:=tdef(symtablestack.top.defowner).fullownerhierarchyname(true)+tprocdef(symtablestack.top.defowner).procsym.prettyname;
-                          end
-                        else
+                        if typeparam.nodetype = typen then
                           begin
-                            prettynamepart:=typeparam.resultdef.fullownerhierarchyname(true);
+                            if (symtablestack.top.symtabletype=parasymtable) and
+                                (symtablestack.top.defowner.typ=procdef) and
+                                (typeparam.resultdef.owner=symtablestack.top) then
+                              begin
+                                { special handling for specializations inside generic function declarations }
+                                prettynamepart:=tdef(symtablestack.top.defowner).fullownerhierarchyname(true)+tprocdef(symtablestack.top.defowner).procsym.prettyname;
+                              end
+                            else
+                              begin
+                                prettynamepart:=typeparam.resultdef.fullownerhierarchyname(true);
+                              end;
                           end;
                         specializename:=specializename+namepart;
                         if not first then
                           prettyname:=prettyname+',';
-                        prettyname:=prettyname+prettynamepart+typeparam.resultdef.typesym.prettyname;
+                        if constprettyname <> '' then
+                          prettyname:=prettyname+constprettyname
+                        else
+                          prettyname:=prettyname+prettynamepart+typeparam.resultdef.typesym.prettyname;
                       end;
                   end
                 else
@@ -411,12 +606,12 @@ uses
       end;
 
 
-    function parse_generic_specialization_types(genericdeflist:tfpobjectlist;poslist:tfplist;out prettyname,specializename:ansistring):boolean;
+    function parse_generic_specialization_types(paramlist:tfpobjectlist;poslist:tfplist;out prettyname,specializename:ansistring):boolean;
       var
         dummypos : tfileposinfo;
       begin
         FillChar(dummypos, SizeOf(tfileposinfo), 0);
-        result:=parse_generic_specialization_types_internal(genericdeflist,poslist,prettyname,specializename,nil,dummypos);
+        result:=parse_generic_specialization_types_internal(paramlist,poslist,prettyname,specializename,nil,dummypos);
       end;
 
 
@@ -578,7 +773,7 @@ uses
         context:=tspecializationcontext.create;
 
         { Parse type parameters }
-        err:=not parse_generic_specialization_types_internal(context.genericdeflist,context.poslist,context.prettyname,context.specializename,parsedtype,parsedpos);
+        err:=not parse_generic_specialization_types_internal(context.paramlist,context.poslist,context.prettyname,context.specializename,parsedtype,parsedpos);
         if err then
           begin
             if not try_to_consume(_GT) then
@@ -627,7 +822,7 @@ uses
 
         { search a generic with the given count of params }
         countstr:='';
-        str(context.genericdeflist.Count,countstr);
+        str(context.paramlist.Count,countstr);
 
         genname:=genname+'$'+countstr;
         ugenname:=upper(genname);
@@ -656,7 +851,7 @@ uses
             result:=generrordef;
             exit;
           end;
-
+        
         { we've found the correct def }
         if context.sym.typ=typesym then
           result:=tstoreddef(ttypesym(context.sym).typedef)
@@ -747,6 +942,7 @@ uses
         hintsprocessed : boolean;
         pd : tprocdef;
         pdflags : tpdflags;
+        typedef : tstoreddef;
       begin
         if not assigned(context) then
           internalerror(2015052203);
@@ -755,7 +951,7 @@ uses
 
         pd:=nil;
 
-        if not check_generic_constraints(genericdef,context.genericdeflist,context.poslist) then
+        if not check_generic_constraints(genericdef,context.paramlist,context.poslist) then
           begin
             { the parameters didn't fit the constraints, so don't continue with the
               specialization }
@@ -771,20 +967,19 @@ uses
         else
           prettyname:=genericdef.typesym.prettyname;
         prettyname:=prettyname+'<'+context.prettyname+'>';
-
         generictypelist:=tfphashobjectlist.create(false);
 
         { build the list containing the types for the generic params }
         if not assigned(genericdef.genericparas) then
           internalerror(2013092601);
-        if context.genericdeflist.count<>genericdef.genericparas.count then
+        if context.paramlist.count<>genericdef.genericparas.count then
           internalerror(2013092603);
         for i:=0 to genericdef.genericparas.Count-1 do
           begin
             srsym:=tsym(genericdef.genericparas[i]);
             if not (sp_generic_para in srsym.symoptions) then
               internalerror(2013092602);
-            generictypelist.add(srsym.realname,tdef(context.genericdeflist[i]).typesym);
+            generictypelist.add(srsym.realname,context.paramlist[i]);
           end;
 
         { Special case if we are referencing the current defined object }
@@ -1196,8 +1391,8 @@ uses
 
     function parse_generic_parameters(allowconstraints:boolean):tfphashobjectlist;
       var
-        generictype : ttypesym;
-        i,firstidx : longint;
+        generictype : tstoredsym;
+        i,firstidx,const_list_index : longint;
         srsymtable : tsymtable;
         basedef,def : tdef;
         defname : tidstring;
@@ -1205,22 +1400,87 @@ uses
         doconsume : boolean;
         constraintdata : tgenericconstraintdata;
         old_block_type : tblock_type;
+        is_const,last_is_const : boolean;
+        last_token : ttoken;
+        last_type_pos : tfileposinfo;
       begin
         result:=tfphashobjectlist.create(false);
         firstidx:=0;
+        const_list_index:=0;
         old_block_type:=block_type;
         block_type:=bt_type;
+        is_const:=false;
+        last_is_const:=false;
+        last_token:=NOTOKEN;
         repeat
+          if try_to_consume(_CONST) then
+            begin
+              { last param was const without semicolon terminator }
+              if (result.count>0) and last_is_const and (last_token<>_SEMICOLON) then
+                MessagePos2(last_type_pos,scan_f_syn_expected,arraytokeninfo[_SEMICOLON].str,arraytokeninfo[last_token].str);
+              is_const := true;
+              const_list_index := result.count;
+            end;
           if token=_ID then
             begin
-              generictype:=ctypesym.create(orgpattern,cundefinedtype,false);
+              if is_const then
+                begin
+                  { last param was type without semicolon terminator }
+                  if (result.count>0) and not last_is_const and (last_token<>_SEMICOLON) then
+                    MessagePos2(last_type_pos,scan_f_syn_expected,arraytokeninfo[_SEMICOLON].str,arraytokeninfo[last_token].str);
+                  generictype:=tconstsym.create_undefined(orgpattern,cundefinedtype);
+                end
+              else
+                begin
+                  { last param was const without semicolon terminator }
+                  if (result.count>0) and last_is_const and (last_token<>_SEMICOLON) then
+                    MessagePos2(last_type_pos,scan_f_syn_expected,arraytokeninfo[_SEMICOLON].str,arraytokeninfo[last_token].str);
+                  generictype:=ttypesym.create(orgpattern,cundefinedtype,false);
+                end;
               { type parameters need to be added as strict private }
               generictype.visibility:=vis_strictprivate;
               include(generictype.symoptions,sp_generic_para);
               result.add(orgpattern,generictype);
+              last_is_const:=is_const;
             end;
           consume(_ID);
-          if try_to_consume(_COLON) then
+          { const restriction }
+          if is_const then
+            begin
+              if try_to_consume(_COLON) then
+                begin
+                  def := nil;
+                  { parse the type and assign the const type to generictype  }
+                  single_type(def,[]);
+                  for i:=const_list_index to result.count-1 do
+                    begin
+                      { finalize constant information once type is known }
+                      if assigned(def) and (def.typ in tgeneric_param_const_types) then
+                        begin
+                          case def.typ of
+                            orddef:
+                              tconstsym(result[i]).consttyp:=constord;
+                            stringdef:
+                              tconstsym(result[i]).consttyp:=conststring;
+                            floatdef:
+                              tconstsym(result[i]).consttyp:=constreal;
+                            setdef:
+                              tconstsym(result[i]).consttyp:=constset;
+                            { pointer always refers to nil with constants }
+                            pointerdef:
+                              tconstsym(result[i]).consttyp:=constnil;
+                          end;
+                          tconstsym(result[i]).constdef:=def;
+                        end
+                      else
+                        Message(type_e_mismatch);
+                    end;
+                  { after type restriction const list terminates }
+                  is_const:=false;
+                end;
+            end
+          { type restriction }
+          else if try_to_consume(_COLON) then
             begin
               if not allowconstraints then
                 { TODO }
@@ -1335,6 +1595,7 @@ uses
                     basedef:=cobjectdef.create(tobjectdef(def).objecttype,defname,tobjectdef(def),false);
                     constraintdata.interfaces.delete(0);
                   end;
+
               if basedef.typ<>errordef then
                 with tstoreddef(basedef) do
                   begin
@@ -1360,21 +1621,27 @@ uses
                 begin
                   { two different typeless parameters are considered as incompatible }
                   for i:=firstidx to result.count-1 do
-                    begin
-                      ttypesym(result[i]).typedef:=cundefineddef.create(false);
-                      ttypesym(result[i]).typedef.typesym:=ttypesym(result[i]);
-                    end;
+                    if tsym(result[i]).typ<>constsym then
+                      begin
+                        ttypesym(result[i]).typedef:=cundefineddef.create(false);
+                        ttypesym(result[i]).typedef.typesym:=ttypesym(result[i]);
+                      end;
                   { a semicolon terminates a type parameter group }
                   firstidx:=result.count;
                 end;
             end;
+          if token = _SEMICOLON then
+            is_const:=false;
+          last_token:=token;
+          last_type_pos:=current_filepos;
         until not (try_to_consume(_COMMA) or try_to_consume(_SEMICOLON));
         { two different typeless parameters are considered as incompatible }
         for i:=firstidx to result.count-1 do
-          begin
-            ttypesym(result[i]).typedef:=cundefineddef.create(false);
-            ttypesym(result[i]).typedef.typesym:=ttypesym(result[i]);
-          end;
+          if tsym(result[i]).typ<>constsym then
+            begin
+              ttypesym(result[i]).typedef:=cundefineddef.create(false);
+              ttypesym(result[i]).typedef.typesym:=ttypesym(result[i]);
+            end;
         block_type:=old_block_type;
       end;
 
@@ -1382,7 +1649,9 @@ uses
     procedure insert_generic_parameter_types(def:tstoreddef;genericdef:tstoreddef;genericlist:tfphashobjectlist);
       var
         i : longint;
-        generictype,sym : ttypesym;
+        generictype : tstoredsym;
+        generictypedef : tdef;
+        sym : tsym;
         st : tsymtable;
       begin
         def.genericdef:=genericdef;
@@ -1407,10 +1676,22 @@ uses
           def.genericparas:=tfphashobjectlist.create(false);
         for i:=0 to genericlist.count-1 do
           begin
-            generictype:=ttypesym(genericlist[i]);
+            generictype:=tstoredsym(genericlist[i]);
             if assigned(generictype.owner) then
               begin
-                sym:=ctypesym.create(genericlist.nameofindex(i),generictype.typedef,true);
+                if generictype.typ=typesym then
+                  sym:=ctypesym.create(genericlist.nameofindex(i),ttypesym(generictype).typedef,true)
+                else if generictype.typ=constsym then
+                  { generictype is a constsym that was created in create_generic_constsym 
+                    during phase 1 so we pass this directly without copying }
+                  begin
+                    sym:=generictype;
+                    { the sym name is still undefined so we set it to match
+                      the generic param name so it's accessible }
+                    sym.realname:=genericlist.nameofindex(i);
+                  end
+                else
+                  internalerror(2019021602);
                 { type parameters need to be added as strict private }
                 sym.visibility:=vis_strictprivate;
                 st.insert(sym);
@@ -1418,13 +1699,17 @@ uses
               end
             else
               begin
-                if (generictype.typedef.typ=undefineddef) and (generictype.typedef<>cundefinedtype) then
+                if generictype.typ=typesym then
                   begin
-                    { the generic parameters were parsed before the genericdef existed thus the
-                      undefineddefs were added as part of the parent symtable }
-                    if assigned(generictype.typedef.owner) then
-                      generictype.typedef.owner.DefList.Extract(generictype.typedef);
-                    generictype.typedef.changeowner(st);
+                    generictypedef:=ttypesym(generictype).typedef;
+                    if (generictypedef.typ=undefineddef) and (generictypedef<>cundefinedtype) then
+                      begin
+                        { the generic parameters were parsed before the genericdef existed thus the
+                          undefineddefs were added as part of the parent symtable }
+                        if assigned(generictypedef.owner) then
+                          generictypedef.owner.DefList.Extract(generictypedef);
+                        generictypedef.changeowner(st);
+                      end;
                   end;
                 st.insert(generictype);
                 include(generictype.symoptions,sp_generic_para);
diff --git a/compiler/ppu.pas b/compiler/ppu.pas
index 10c42e7eb8..31011be3e8 100644
--- a/compiler/ppu.pas
+++ b/compiler/ppu.pas
@@ -43,7 +43,7 @@ type
 {$endif Test_Double_checksum}
 
 const
-  CurrentPPUVersion = 201;
+  CurrentPPUVersion = 203;
 
 { unit flags }
   uf_init                = $000001; { unit has initialization section }
diff --git a/compiler/ptype.pas b/compiler/ptype.pas
index 38e2526e9f..28cd0f94f8 100644
--- a/compiler/ptype.pas
+++ b/compiler/ptype.pas
@@ -1436,7 +1436,9 @@ implementation
                                  highval:=tordconstnode(trangenode(pt).right).value;
                                  if highval<lowval then
                                   begin
-                                    Message(parser_e_array_lower_less_than_upper_bound);
+                                    { ignore error if node is generic param }
+                                    if not (nf_generic_para in pt.flags) then
+                                      Message(parser_e_array_lower_less_than_upper_bound);
                                     highval:=lowval;
                                   end
                                  else if (lowval<int64(low(asizeint))) or
diff --git a/compiler/symconst.pas b/compiler/symconst.pas
index a5ae7e0fb9..e02ce3a8ca 100644
--- a/compiler/symconst.pas
+++ b/compiler/symconst.pas
@@ -232,7 +232,10 @@ type
       because we have to access this information in the symtable unit }
     df_llvm_no_struct_packing,
     { internal def that's not for any export }
-    df_internal
+    df_internal,
+    { the def was derived with generic type or const fields so the size
+      of the def can not be determined }
+    df_has_generic_fields
   );
   tdefoptions=set of tdefoption;
 
@@ -651,7 +654,7 @@ type
     arraydef,recorddef,pointerdef,orddef,
     stringdef,enumdef,procdef,objectdef,errordef,
     filedef,formaldef,setdef,procvardef,floatdef,
-    classrefdef,forwarddef,variantdef,undefineddef
+    classrefdef,forwarddef,variantdef,genericconstdef,undefineddef
   );
 
   { possible types for symtable entries }
@@ -692,7 +695,8 @@ type
   tconsttyp = (constnone,
     constord,conststring,constreal,
     constset,constpointer,constnil,
-    constresourcestring,constwstring,constguid
+    constresourcestring,constwstring,constguid,
+    constundefined
   );
 
   { RTTI information to store }
@@ -831,7 +835,7 @@ inherited_objectoptions : tobjectoptions = [oo_has_virtual,oo_has_private,oo_has
        'abstractdef','arraydef','recorddef','pointerdef','orddef',
        'stringdef','enumdef','procdef','objectdef','errordef',
        'filedef','formaldef','setdef','procvardef','floatdef',
-       'classrefdef','forwarddef','variantdef','undefineddef'
+       'classrefdef','forwarddef','variantdef','genconstdef','undefineddef'
      );
 
      EqualTypeName : array[tequaltype] of string[16] = (
diff --git a/compiler/symdef.pas b/compiler/symdef.pas
index 4a260c46b9..0f7a2e4c06 100644
--- a/compiler/symdef.pas
+++ b/compiler/symdef.pas
@@ -129,6 +129,9 @@ interface
           function is_generic:boolean;inline;
           { same as above for specializations }
           function is_specialization:boolean;inline;
+          { generic utilities }
+          function is_generic_param_const(index:integer):boolean;inline;
+          function get_generic_param_def(index:integer):tdef;inline;
           { registers this def in the unit's deflist; no-op if already registered }
           procedure register_def; override;
           { add the def to the top of the symtable stack if it's not yet owned
@@ -2197,13 +2200,26 @@ implementation
          for i:=0 to genericparas.count-1 do
            begin
              sym:=tsym(genericparas[i]);
-             if sym.typ<>symconst.typesym then
+             { sym must be either a type or const }
+             if not (sym.typ in [symconst.typesym,symconst.constsym]) then
                internalerror(2014050903);
              if sym.owner.defowner<>self then
                exit(false);
            end;
      end;
 
+   function tstoreddef.is_generic_param_const(index:integer):boolean;
+     begin
+       result := tsym(genericparas[index]).typ = constsym;
+     end;  
+
+   function tstoreddef.get_generic_param_def(index:integer):tdef;
+     begin
+       if tsym(genericparas[index]).typ = constsym then
+         result := tconstsym(genericparas[index]).constdef
+       else
+         result := ttypesym(genericparas[index]).typedef;
+     end;
 
    function tstoreddef.is_specialization: boolean;
      var
@@ -2220,12 +2236,12 @@ implementation
            for i:=0 to genericparas.count-1 do
              begin
                sym:=tsym(genericparas[i]);
-               if sym.typ<>symconst.typesym then
+               { sym must be either a type or const }
+               if not (sym.typ in [symconst.typesym,symconst.constsym]) then
                  internalerror(2014050904);
                if sym.owner.defowner<>self then
                  exit(true);
              end;
-           result:=false;
          end;
      end;
 
diff --git a/compiler/symsym.pas b/compiler/symsym.pas
index b21a5f9de9..04c07a5ec7 100644
--- a/compiler/symsym.pas
+++ b/compiler/symsym.pas
@@ -157,7 +157,7 @@ interface
           fprettyname : ansistring;
           constructor create(const n : string;def:tdef;doregister:boolean);virtual;
           destructor destroy;override;
-          constructor ppuload(ppufile:tcompilerppufile);
+          constructor ppuload(ppufile:tcompilerppufile);virtual;
           { do not override this routine in platform-specific subclasses,
             override ppuwrite_platform instead }
           procedure ppuwrite(ppufile:tcompilerppufile);override;final;
@@ -392,6 +392,7 @@ interface
           constructor create_ptr(const n : string;t : tconsttyp;v : pointer;def:tdef);virtual;
           constructor create_string(const n : string;t : tconsttyp;str:pchar;l:longint;def:tdef);virtual;
           constructor create_wstring(const n : string;t : tconsttyp;pw:pcompilerwidestring);virtual;
+          constructor create_undefined(const n : string;def: tdef);
           constructor ppuload(ppufile:tcompilerppufile);
           destructor  destroy;override;
           procedure buildderef;override;
@@ -1581,7 +1582,6 @@ implementation
           tparasymtable(parast).ppuwrite(ppufile);
       end;
 
-
 {****************************************************************************
                             TABSTRACTVARSYM
 ****************************************************************************}
@@ -2344,6 +2344,13 @@ implementation
          value.len:=getlengthwidestring(pw);
       end;
 
+    constructor tconstsym.create_undefined(const n : string;def: tdef);
+      begin
+        inherited create(constsym,n,true);
+        fillchar(value, sizeof(value), #0);
+        consttyp:=constundefined;
+        constdef:=def;
+      end;
 
     constructor tconstsym.ppuload(ppufile:tcompilerppufile);
       var
@@ -2416,7 +2423,8 @@ implementation
                new(pguid(value.valueptr));
                ppufile.getdata(value.valueptr^,sizeof(tguid));
              end;
-           constnil :
+           constnil,
+           constundefined :
              ppufile.getderef(constdefderef);
            else
              Message1(unit_f_ppu_invalid_entry,tostr(ord(consttyp)));
@@ -2448,7 +2456,7 @@ implementation
       begin
         inherited;
         case consttyp  of
-          constnil,constord,constreal,constpointer,constset,conststring,constresourcestring,constguid:
+          constnil,constord,constreal,constpointer,constset,conststring,constresourcestring,constguid,constundefined:
             constdefderef.build(constdef);
           constwstring:
             ;
@@ -2461,7 +2469,7 @@ implementation
     procedure tconstsym.deref;
       begin
         case consttyp of
-          constnil,constord,constreal,constpointer,constset,conststring,constresourcestring,constguid:
+          constnil,constord,constreal,constpointer,constset,conststring,constresourcestring,constguid,constundefined:
             constdef:=tdef(constdefderef.resolve);
           constwstring:
             constdef:=carraydef.getreusable(cwidechartype,getlengthwidestring(pcompilerwidestring(value.valueptr)));
@@ -2476,7 +2484,8 @@ implementation
          inherited ppuwrite(ppufile);
          ppufile.putbyte(byte(consttyp));
          case consttyp of
-           constnil :
+           constnil,
+           constundefined :
              ppufile.putderef(constdefderef);
            constord :
              begin
@@ -2627,7 +2636,6 @@ implementation
           result:=inherited prettyname;
       end;
 
-
 {****************************************************************************
                                   TSYSSYM
 ****************************************************************************}
diff --git a/compiler/symtable.pas b/compiler/symtable.pas
index 796b2d6736..ae82024b03 100644
--- a/compiler/symtable.pas
+++ b/compiler/symtable.pas
@@ -2781,7 +2781,7 @@ implementation
 
     function generate_objectpascal_helper_key(def:tdef):string;
       begin
-        if not assigned(def) then
+        if not assigned(def) or (def.typ = errordef) then
           internalerror(2013020501);
         if def.typ in [recorddef,objectdef] then
           result:=make_mangledname('',tabstractrecorddef(def).symtable,'')
diff --git a/compiler/utils/ppuutils/ppudump.pp b/compiler/utils/ppuutils/ppudump.pp
index 74fde5c6c2..80d9d4df11 100644
--- a/compiler/utils/ppuutils/ppudump.pp
+++ b/compiler/utils/ppuutils/ppudump.pp
@@ -1552,7 +1552,8 @@ const
      { this should never happen for defs stored to a ppu file }
      (mask:df_not_registered_no_free;  str:'Unregistered/No free (invalid)'),
      (mask:df_llvm_no_struct_packing;  str:'LLVM unpacked struct'),
-     (mask:df_internal;       str:'Internal')
+     (mask:df_internal;       str:'Internal'),
+     (mask:df_has_generic_fields; str:'Has generic fields')
   );
   defstate : array[1..ord(high(tdefstate))] of tdefstateinfo=(
      (mask:ds_vmt_written;           str:'VMT Written'),
diff --git a/tests/test/tgenconst1.pp b/tests/test/tgenconst1.pp
new file mode 100644
index 0000000000..297b982b0f
--- /dev/null
+++ b/tests/test/tgenconst1.pp
@@ -0,0 +1,33 @@
+{$mode objfpc}
+program tgenconst1;
+
+type
+	kNames = set of (Blaise,Pascal);
+	kChars = set of char;
+type
+	generic TBoolean<const U: boolean> = record end;
+	generic TString<const U: string> = record end;
+	generic TFloat<const U: single> = record end;
+	generic TInteger<const U: integer> = record end;
+	generic TChar<const U: char> = record end;
+	generic TByte<const U: byte> = record end;
+	generic TQWord<const U: QWord> = record end;
+	generic TUndefined<const U> = record end;
+	generic TNames<const U: kNames> = record end;
+	generic TChars<const U: kChars> = record end;
+	generic TPointer<const U: pointer> = record end;
+
+var
+	a: specialize TBoolean<true>;
+	b: specialize TString<'string'>;
+	c: specialize TFloat<1>;
+	d: specialize TInteger<10>;
+	e: specialize TByte<255>;
+	f: specialize TChar<'a'>;
+	g: specialize TUndefined<nil>;
+	h: specialize TNames<[Blaise,Pascal]>;
+	i: specialize TChars<['a','b']>;
+	j: specialize TQWord<10>;
+	k: specialize TPointer<nil>;
+begin
+end.
diff --git a/tests/test/tgenconst10.pp b/tests/test/tgenconst10.pp
new file mode 100644
index 0000000000..f05a27718c
--- /dev/null
+++ b/tests/test/tgenconst10.pp
@@ -0,0 +1,13 @@
+{%FAIL}
+
+{$mode objfpc}
+
+program tgenconst10;
+
+type
+	generic TByte<T> = record end;
+	
+var
+	a: specialize TByte<10>;
+begin
+end.
diff --git a/tests/test/tgenconst11.pp b/tests/test/tgenconst11.pp
new file mode 100644
index 0000000000..ea409bec9b
--- /dev/null
+++ b/tests/test/tgenconst11.pp
@@ -0,0 +1,21 @@
+{%FAIL}
+{$mode objfpc}
+program tgenconst11;
+type
+	TEnum = (aaa,bbb,ccc,ddd);
+type
+	generic TConst<const U> = class end;
+
+var
+	a:specialize TConst<10>;
+	b:specialize TConst<10.5>;
+	c:specialize TConst<'string'>;
+	d:specialize TConst<[1,2,3]>;
+	e:specialize TConst<[aaa,bbb,ccc]>;
+begin
+	a:=specialize TConst<20>.Create;
+	b:=specialize TConst<10.1>.Create;
+	c:=specialize TConst<'_string'>.Create;
+	d:=specialize TConst<[1,2,3,4]>.Create;
+	e:=specialize TConst<[aaa,bbb,ccc,ddd]>.Create;
+end.
\ No newline at end of file
diff --git a/tests/test/tgenconst12.pp b/tests/test/tgenconst12.pp
new file mode 100644
index 0000000000..8f591f6867
--- /dev/null
+++ b/tests/test/tgenconst12.pp
@@ -0,0 +1,16 @@
+{$mode objfpc}
+program tgenconst12;
+
+type
+  generic TTest<const U> = class
+  		class procedure DoThis;
+  end;
+
+class procedure TTest.DoThis;
+begin
+end;
+
+type
+	ATest = specialize TTest<100>;
+begin 
+end.
diff --git a/tests/test/tgenconst13.pp b/tests/test/tgenconst13.pp
new file mode 100644
index 0000000000..0d5f8b1813
--- /dev/null
+++ b/tests/test/tgenconst13.pp
@@ -0,0 +1,20 @@
+{$mode objfpc}
+program tgenconst13;
+type
+	TEnum = (aaa,bbb,ccc);
+type
+	generic TConst<const U> = class end;
+
+var
+	a:specialize TConst<10>;
+	b:specialize TConst<10.5>;
+	c:specialize TConst<'string'>;
+	d:specialize TConst<[1,2,3]>;
+	e:specialize TConst<[aaa,bbb,ccc]>;
+begin
+	a:=specialize TConst<10>.Create;
+	b:=specialize TConst<10.5>.Create;
+	c:=specialize TConst<'string'>.Create;
+	d:=specialize TConst<[1,2,3]>.Create;
+	e:=specialize TConst<[aaa,bbb,ccc]>.Create;
+end.
diff --git a/tests/test/tgenconst14.pp b/tests/test/tgenconst14.pp
new file mode 100644
index 0000000000..7f98086630
--- /dev/null
+++ b/tests/test/tgenconst14.pp
@@ -0,0 +1,29 @@
+{$mode objfpc}
+{$modeswitch advancedrecords}
+program tgenconst14;
+
+type
+  generic TBinaryOp<const I: Integer> = record
+    const
+    	d0 = I + I;
+    	d1 = I - I; 
+    	d2 = I * I; 
+    	d3 = I / I; 
+    	d4 = I div I; 
+    	d5 = I mod I; 
+    	d6 = I and I;
+    	d7 = I or I;
+  end;
+
+var
+	op: specialize TBinaryOp<100>;
+begin
+	writeln(op.d0);
+	writeln(op.d1);
+	writeln(op.d2);
+	writeln(op.d3:1:1);
+	writeln(op.d4);
+	writeln(op.d5);
+	writeln(op.d6);
+	writeln(op.d7);
+end.
\ No newline at end of file
diff --git a/tests/test/tgenconst15.pp b/tests/test/tgenconst15.pp
new file mode 100644
index 0000000000..56744cd0a7
--- /dev/null
+++ b/tests/test/tgenconst15.pp
@@ -0,0 +1,30 @@
+{$mode objfpc}
+{$modeswitch advancedrecords}
+program tgenconst15;
+
+type
+	kNames = set of (Blaise, Pascal);
+  generic TSet<const I: kNames> = record
+    const c = I;
+  end;
+  generic TString<const I: String> = record
+    const c = I;
+  end;
+  generic TWideString<const I: WideString> = record
+    const c = I;
+  end;
+  generic TSingle<const I: Single> = record
+    const c = I; 
+  end;
+  generic TDouble<const I: Double> = record
+    const c = I; 
+  end;
+  generic TReal<const I: Real> = record
+    const c = I; 
+  end;
+
+var
+	a0: specialize TReal<100>;
+begin
+	writeln(a0.c);
+end.
\ No newline at end of file
diff --git a/tests/test/tgenconst16.pp b/tests/test/tgenconst16.pp
new file mode 100644
index 0000000000..275867ce25
--- /dev/null
+++ b/tests/test/tgenconst16.pp
@@ -0,0 +1,86 @@
+{$mode objfpc}
+{$modeswitch advancedrecords}
+program tgenconst16;
+
+type
+  Day = (mon,tue,wed,thu,fri,sat,sun);  
+  Days = set of Day;  
+  generic TSet<const I: Days> = record
+    const
+      d0 = I + I;   // Union
+      d1 = I - I;   // Difference
+      d2 = I * I;   // Intersection
+      d3 = I >< I;  // Symmetric difference
+      d4 = I <= I;  // Contains
+      d5 = mon in I;
+  end;
+  generic TArray<const I> = record
+    type
+      t0 = array[0..I - 1] of integer;
+      t1 = array[0..high(I)] of integer;
+      t2 = array[0..low(I)] of integer;
+      t3 = array[0..sizeof(I)] of integer;
+    public
+      d0: array[0..I - 1] of integer;
+      d1: array[0..high(I)] of integer;
+      d2: array[0..low(I)] of integer;
+      d3: array[0..sizeof(I)] of integer;
+  end;
+  generic TUnaryOp<const I> = record
+    const
+      d0 = -I;
+      d1 = +I;
+      d2 = not I;
+  end;
+  generic TBinaryOp<const I> = record
+    const
+      // Arithmetic operators
+      // https://freepascal.org/docs-html/ref/refsu45.html
+      d0 = I + I;
+      d1 = I - I;
+      d2 = I * I; 
+      d3 = I / I; 
+      d4 = I div I; 
+      d5 = I mod I; 
+      // Boolean operators
+      // https://freepascal.org/docs-html/ref/refsu47.html
+      d6 = I and I;
+      d7 = I or I;
+      d8 = I xor I;
+      // Logical operators
+      // https://freepascal.org/docs-html/ref/refsu46.html
+      d9 = I shl I;
+      d10 = I shr I;
+      d11 = I << I;
+      d12 = I >> I;
+      // Relational operators
+      // https://freepascal.org/docs-html/ref/refsu50.html#x153-17500012.8.6
+      d13 = I <> I;
+      d14 = I < I;
+      d15 = I > I;
+      d16 = I <= I;
+      d17 = I >= I;
+      d18 = I = I;
+  end;
+  generic TOther<const I> = record
+    procedure DoThis(param: integer = I);
+  end;
+
+procedure TOther.DoThis(param: integer = I);
+begin
+  writeln(param, ' default:', I);
+end;
+
+var
+  t0: specialize TBinaryOp<100>;
+  t1: specialize TOther<100>;
+begin
+  //writeln(op.d0);
+  //writeln(op.d1);
+  //writeln(op.d2);
+  //writeln(op.d3:1:1);
+  //writeln(op.d4);
+  //writeln(op.d5);
+  //writeln(op.d6);
+  //writeln(op.d7);
+end.
\ No newline at end of file
diff --git a/tests/test/tgenconst17.pp b/tests/test/tgenconst17.pp
new file mode 100644
index 0000000000..26dc2ee21f
--- /dev/null
+++ b/tests/test/tgenconst17.pp
@@ -0,0 +1,36 @@
+{$mode objfpc}
+{$modeswitch advancedrecords}
+program tgenconst17;
+
+type
+  generic TUnaryOp<const I: integer> = record
+    const
+      d0 = -I;
+      d1 = +I;
+      d2 = not I;
+  end;
+  generic TBinaryOp<const I: integer> = record
+    const
+      d0 = I + I;
+      d1 = I - I;
+      d2 = I * I; 
+      d3 = I / I; 
+      d4 = I div I; 
+      d5 = I mod I; 
+      d6 = I and I;
+      d7 = I or I;
+      d8 = I xor I;
+      d9 = I shl I;
+      d10 = I shr I;
+      d11 = I << I;
+      d12 = I >> I;
+      d13 = I <> I;
+      d14 = I < I;
+      d15 = I > I;
+      d16 = I <= I;
+      d17 = I >= I;
+      d18 = I = I;
+  end;
+
+begin
+end.
\ No newline at end of file
diff --git a/tests/test/tgenconst18.pp b/tests/test/tgenconst18.pp
new file mode 100644
index 0000000000..a4ba526803
--- /dev/null
+++ b/tests/test/tgenconst18.pp
@@ -0,0 +1,12 @@
+{%FAIL}
+{$mode objfpc}
+{$modeswitch advancedrecords}
+program tgenconst18;
+
+type
+  generic TInt<const I: string> = record
+    const c = I div I;
+  end;
+
+begin
+end.
\ No newline at end of file
diff --git a/tests/test/tgenconst2.pp b/tests/test/tgenconst2.pp
new file mode 100644
index 0000000000..aa3a960634
--- /dev/null
+++ b/tests/test/tgenconst2.pp
@@ -0,0 +1,12 @@
+{$mode objfpc}
+program tgenconst2;
+
+type
+	generic TStuff1<T1,T2;const U1,U2> = record end;
+	generic TStuff2<T1,T2;const U1,U2:integer> = record end;
+	
+var
+	a: specialize TStuff1<integer,string,10,'string'>;
+	b: specialize TStuff2<integer,string,10,10>;
+begin
+end.
diff --git a/tests/test/tgenconst3.pp b/tests/test/tgenconst3.pp
new file mode 100644
index 0000000000..aea0e307e2
--- /dev/null
+++ b/tests/test/tgenconst3.pp
@@ -0,0 +1,16 @@
+{$mode objfpc}
+{$modeswitch advancedrecords}
+program tgenconst3;
+
+type
+	generic TList<T;const U:integer> = record
+		const
+			max = U;
+		public
+			m_list: array[0..max-1] of T;
+	end;
+
+var
+	list: specialize TList<integer,128>;
+begin
+end.
diff --git a/tests/test/tgenconst4.pp b/tests/test/tgenconst4.pp
new file mode 100644
index 0000000000..a1fae00c43
--- /dev/null
+++ b/tests/test/tgenconst4.pp
@@ -0,0 +1,11 @@
+{$mode objfpc}
+program tgenconst4;
+
+generic procedure DoThis<T;const U:string>(msg:string = U);
+begin
+	writeln(msg, ' sizeof:',sizeof(t), ' default: ', U);
+end;
+
+begin
+	specialize DoThis<integer,'genparam'>('hello world');
+end.
diff --git a/tests/test/tgenconst5.pp b/tests/test/tgenconst5.pp
new file mode 100644
index 0000000000..63514a976c
--- /dev/null
+++ b/tests/test/tgenconst5.pp
@@ -0,0 +1,24 @@
+{$mode objfpc}
+program tgenconst5;
+
+type
+	generic THelperA<const U:integer> = record
+		list: array[0..U-1] of byte;
+	end;
+
+type
+	generic THelperB<T> = record
+		value: T;
+	end;
+
+type
+	generic TList<T; const U:integer> = record
+		helperA: specialize THelperA<U>;
+		helperB: specialize THelperB<T>;
+	end;
+
+var
+	list: specialize TList<integer,32>;
+begin
+	writeln('sizeof:',sizeof(list));
+end.
diff --git a/tests/test/tgenconst6.pp b/tests/test/tgenconst6.pp
new file mode 100644
index 0000000000..3ee3785423
--- /dev/null
+++ b/tests/test/tgenconst6.pp
@@ -0,0 +1,21 @@
+{$mode delphi}
+program tgenconst6;
+
+type
+	TList<T;const U> = class
+		list: array[0..U-1] of T;
+		function capacity: integer;
+	end;
+
+function TList<T,U>.capacity: integer;
+begin
+	result := U;	
+end;	
+
+var
+	nums:TList<integer,16>;
+	strs:TList<string,16>;
+begin
+	nums := TList<integer,16>.Create;
+	strs := TList<string,16>.Create;
+end.
diff --git a/tests/test/tgenconst7.pp b/tests/test/tgenconst7.pp
new file mode 100644
index 0000000000..9d8e81ef05
--- /dev/null
+++ b/tests/test/tgenconst7.pp
@@ -0,0 +1,11 @@
+{%FAIL}
+{$mode objfpc}
+program tgenconst7;
+
+type
+	generic TInteger<const U: integer> = record end;
+
+var
+	a: specialize TInteger<'string'>;
+begin
+end.
diff --git a/tests/test/tgenconst8.pp b/tests/test/tgenconst8.pp
new file mode 100644
index 0000000000..75844f7181
--- /dev/null
+++ b/tests/test/tgenconst8.pp
@@ -0,0 +1,11 @@
+{%FAIL}
+{$mode objfpc}
+program tgenconst8;
+
+type
+	generic TByte<const U: Byte> = record end;
+	
+var
+	a: specialize TByte<300>;
+begin
+end.
diff --git a/tests/test/tgenconst9.pp b/tests/test/tgenconst9.pp
new file mode 100644
index 0000000000..939cb90302
--- /dev/null
+++ b/tests/test/tgenconst9.pp
@@ -0,0 +1,11 @@
+{%FAIL}
+{$mode objfpc}
+program tgenconst9;
+
+type
+	generic TByte<const U: Byte> = record end;
+	
+var
+	a: specialize TByte<string>;
+begin
+end.
-- 
2.17.2 (Apple Git-113)

diff -ur compiler/defcmp.pas compiler/defcmp.pas
--- compiler/defcmp.pas	2019-05-04 11:21:35.506321600 -0400
+++ compiler/defcmp.pas	2019-05-04 10:02:12.755701000 -0400
@@ -175,7 +175,6 @@
       symtable,symsym,symcpu,
       defutil,symutil;
 
-
     function compare_defs_ext(def_from,def_to : tdef;
                               fromtreetype : tnodetype;
                               var doconv : tconverttype;
@@ -345,9 +344,13 @@
                        internalerror(2012091302);
                      symfrom:=ttypesym(tstoreddef(def_from).genericparas[i]);
                      symto:=ttypesym(tstoreddef(def_to).genericparas[i]);
-                     if not (symfrom.typ=typesym) or not (symto.typ=typesym) then
+                     if not (symfrom.typ in [typesym,constsym]) or not (symto.typ in [typesym,constsym]) then
                        internalerror(2012121401);
-                     if not equal_defs(ttypesym(symfrom).typedef,ttypesym(symto).typedef) then
+                     if symto.typ <> symfrom.typ then
+                       diff:=true
+                     else if (symfrom.typ=constsym) and (symto.typ=constsym) and not equal_constsym(tconstsym(symfrom),tconstsym(symto),true) then
+                       diff:=true
+                     else if not equal_defs(ttypesym(symfrom).typedef,ttypesym(symto).typedef) then
                        diff:=true;
                      if diff then
                        break;
diff -ur compiler/htypechk.pas compiler/htypechk.pas
--- compiler/htypechk.pas	2019-05-04 11:21:35.631332300 -0400
+++ compiler/htypechk.pas	2019-05-04 10:02:12.349417700 -0400
@@ -2723,7 +2723,7 @@
               internalerror(2015060301);
             { check whether the given parameters are compatible
               to the def's constraints }
-            if not check_generic_constraints(pd,spezcontext.genericdeflist,spezcontext.poslist) then
+            if not check_generic_constraints(pd,spezcontext.paramlist,spezcontext.poslist) then
               exit;
             def:=generate_specialization_phase2(spezcontext,pd,false,'');
             case def.typ of
diff -ur compiler/ncon.pas compiler/ncon.pas
--- compiler/ncon.pas	2019-05-04 11:21:35.709462700 -0400
+++ compiler/ncon.pas	2019-05-04 10:02:03.520316200 -0400
@@ -279,6 +279,7 @@
         p1  : tnode;
         len : longint;
         pc  : pchar;
+        value_set : pconstset;
       begin
         p1:=nil;
         case p.consttyp of
@@ -304,18 +305,51 @@
           constwstring :
             p1:=cstringconstnode.createunistr(pcompilerwidestring(p.value.valueptr));
           constreal :
-            p1:=crealconstnode.create(pbestreal(p.value.valueptr)^,p.constdef);
+            begin
+              if sp_generic_para in p.symoptions then
+                p1:=crealconstnode.create(default(bestreal),p.constdef)
+              else
+                p1:=crealconstnode.create(pbestreal(p.value.valueptr)^,p.constdef);
+            end;
           constset :
-            p1:=csetconstnode.create(pconstset(p.value.valueptr),p.constdef);
+            begin
+              if sp_generic_para in p.symoptions then
+                begin
+                  new(value_set);
+                  p1:=csetconstnode.create(value_set,p.constdef);
+                end
+              else
+                p1:=csetconstnode.create(pconstset(p.value.valueptr),p.constdef);
+            end;
           constpointer :
-            p1:=cpointerconstnode.create(p.value.valueordptr,p.constdef);
+            begin
+              if sp_generic_para in p.symoptions then
+                p1:=cpointerconstnode.create(default(tconstptruint),p.constdef)
+              else
+                p1:=cpointerconstnode.create(p.value.valueordptr,p.constdef);
+            end;
           constnil :
             p1:=cnilnode.create;
+          { constundefined is a placeholder for unrestricted generic const params
+            so we just treat it as a nil node. }
+          constundefined :
+            begin
+              p1:=cnilnode.create;
+              p1.resultdef:=p.constdef;
+            end;
           constguid :
-            p1:=cguidconstnode.create(pguid(p.value.valueptr)^);
+            begin
+              if sp_generic_para in p.symoptions then
+                p1:=cguidconstnode.create(default(tguid))
+              else
+                p1:=cguidconstnode.create(pguid(p.value.valueptr)^);
+            end;
           else
             internalerror(200205103);
         end;
+        { transfer generic param flag from symbol to node }
+        if sp_generic_para in p.symoptions then
+          include(p1.flags,nf_generic_para);
         genconstsymtree:=p1;
       end;
 
diff -ur compiler/nmat.pas compiler/nmat.pas
--- compiler/nmat.pas	2019-05-04 11:21:35.787594200 -0400
+++ compiler/nmat.pas	2019-05-04 10:02:02.879642000 -0400
@@ -129,7 +129,10 @@
               end;
             if rv = 0 then
               begin
-                Message(parser_e_division_by_zero);
+                { if the node is derived from a generic const parameter
+                  then don't issue an error }
+                if not (nf_generic_para in flags) then
+                  Message(parser_e_division_by_zero);
                 { recover }
                 tordconstnode(right).value := 1;
               end;
diff -ur compiler/node.pas compiler/node.pas
--- compiler/node.pas	2019-05-04 11:21:35.881351800 -0400
+++ compiler/node.pas	2019-05-04 10:02:47.741464800 -0400
@@ -274,10 +274,13 @@
          nf_block_with_exit,
 
          { tloadvmtaddrnode }
-         nf_ignore_for_wpo  { we know that this loadvmtaddrnode cannot be used to construct a class instance }
+         nf_ignore_for_wpo,  { we know that this loadvmtaddrnode cannot be used to construct a class instance }
 
-         { WARNING: there are now 31 elements in this type, and a set of this
-             type is written to the PPU. So before adding more than 32 elements,
+         { node is derived from generic parameter }
+         nf_generic_para
+
+         { WARNING: there are now 32 elements in this type, and a set of this
+             type is written to the PPU. So before adding more elements,
              either move some flags to specific nodes, or stream a normalset
              to the ppu
          }
@@ -985,6 +988,9 @@
     constructor tunarynode.create(t:tnodetype;l : tnode);
       begin
          inherited create(t);
+         { transfer generic paramater flag }
+         if assigned(l) and (nf_generic_para in l.flags) then
+           include(flags,nf_generic_para);
          left:=l;
       end;
 
@@ -1080,7 +1086,12 @@
     constructor tbinarynode.create(t:tnodetype;l,r : tnode);
       begin
          inherited create(t,l);
-         right:=r
+         { transfer generic paramater flag }
+         if assigned(l) and (nf_generic_para in l.flags) then
+           include(flags,nf_generic_para)
+         else if assigned(r) and (nf_generic_para in r.flags) then
+           include(flags,nf_generic_para);
+         right:=r;
       end;
 
 
diff -ur compiler/nset.pas compiler/nset.pas
--- compiler/nset.pas	2019-05-04 11:21:35.959483400 -0400
+++ compiler/nset.pas	2019-05-04 10:02:02.270218000 -0400
@@ -401,8 +401,9 @@
          { both types must be compatible }
          if compare_defs(left.resultdef,right.resultdef,left.nodetype)=te_incompatible then
            IncompatibleTypes(left.resultdef,right.resultdef);
-         { Check if only when its a constant set }
-         if (left.nodetype=ordconstn) and (right.nodetype=ordconstn) then
+         { check if only when its a constant set and
+           ignore range nodes which are generic parameter derived }
+         if not (nf_generic_para in flags) and (left.nodetype=ordconstn) and (right.nodetype=ordconstn) then
           begin
             { upper limit must be greater or equal than lower limit }
             if (tordconstnode(left).value>tordconstnode(right).value) and
diff -ur compiler/pdecl.pas compiler/pdecl.pas
--- compiler/pdecl.pas	2019-05-04 11:21:36.037614400 -0400
+++ compiler/pdecl.pas	2019-05-04 10:02:01.895188400 -0400
@@ -126,9 +126,14 @@
              end;
            setconstn :
              begin
-               new(ps);
-               ps^:=tsetconstnode(p).value_set^;
-               hp:=cconstsym.create_ptr(orgname,constset,ps,p.resultdef);
+               if nf_generic_para in p.flags then
+                 hp:=cconstsym.create_ptr(orgname,constset,nil,p.resultdef)
+               else
+                 begin
+                   new(ps);
+                   ps^:=tsetconstnode(p).value_set^;
+                   hp:=cconstsym.create_ptr(orgname,constset,ps,p.resultdef);
+                 end;
              end;
            pointerconstn :
              begin
@@ -141,18 +146,18 @@
            typen :
              begin
                if is_interface(p.resultdef) then
-                begin
-                  if assigned(tobjectdef(p.resultdef).iidguid) then
-                   begin
-                     new(pg);
-                     pg^:=tobjectdef(p.resultdef).iidguid^;
-                     hp:=cconstsym.create_ptr(orgname,constguid,pg,p.resultdef);
-                   end
-                  else
-                   Message1(parser_e_interface_has_no_guid,tobjectdef(p.resultdef).objrealname^);
-                end
-               else
-                Message(parser_e_illegal_expression);
+                 begin
+                   if assigned(tobjectdef(p.resultdef).iidguid) then
+                     begin
+                       new(pg);
+                       pg^:=tobjectdef(p.resultdef).iidguid^;
+                       hp:=cconstsym.create_ptr(orgname,constguid,pg,p.resultdef);
+                     end
+                    else
+                      Message1(parser_e_interface_has_no_guid,tobjectdef(p.resultdef).objrealname^);
+                 end
+               else 
+                 Message(parser_e_illegal_expression);
              end;
            inlinen:
              begin
@@ -177,8 +182,19 @@
                end;
              end;
            else
-             Message(parser_e_illegal_expression);
+             begin
+               { the node is from a generic parameter constant and is 
+                 untyped so we need to pass a placeholder constant 
+                 instead of givng an error }
+               if nf_generic_para in p.flags then 
+                 hp:=cconstsym.create_ord(orgname,constnil,0,p.resultdef)
+               else
+                 Message(parser_e_illegal_expression);
+             end;
         end;
+        { transfer generic param flag from node to symbol }
+        if nf_generic_para in p.flags then
+          include(hp.symoptions,sp_generic_para);
         current_tokenpos:=storetokenpos;
         p.free;
         readconstant:=hp;
@@ -510,8 +526,9 @@
                { we are not freeing the type parameters, so register them }
                for i:=0 to generictypelist.count-1 do
                  begin
-                    ttypesym(generictypelist[i]).register_sym;
-                    tstoreddef(ttypesym(generictypelist[i]).typedef).register_def;
+                    tstoredsym(generictypelist[i]).register_sym;
+                    if tstoredsym(generictypelist[i]).typ=typesym then
+                      tstoreddef(ttypesym(generictypelist[i]).typedef).register_def;
                  end;
 
                str(generictypelist.Count,s);
diff -ur compiler/pdecvar.pas compiler/pdecvar.pas
--- compiler/pdecvar.pas	2019-05-04 11:21:36.100120600 -0400
+++ compiler/pdecvar.pas	2019-05-04 10:02:01.567037900 -0400
@@ -1705,6 +1705,10 @@
                    hdef:=generrordef;
                end;
 
+             { field type is a generic param so set a flag in the struct }
+             if assigned(hdef.typesym) and (sp_generic_para in hdef.typesym.symoptions) then
+               include(current_structdef.defoptions,df_has_generic_fields);
+
              { Process procvar directives }
              if maybe_parse_proc_directives(hdef) then
                semicoloneaten:=true;
diff -ur compiler/pexpr.pas compiler/pexpr.pas
--- compiler/pexpr.pas	2019-05-04 11:21:36.178250700 -0400
+++ compiler/pexpr.pas	2019-05-04 10:02:01.192002400 -0400
@@ -446,6 +446,9 @@
                   { no packed bit support for these things }
                   if l=in_bitsizeof_x then
                     statement_syssym:=caddnode.create(muln,statement_syssym,cordconstnode.create(8,sinttype,true));
+                  { type sym is a generic parameter }
+                  if assigned(p1.resultdef.typesym) and (sp_generic_para in p1.resultdef.typesym.symoptions) then
+                    include(statement_syssym.flags,nf_generic_para);
                 end
               else
                begin
@@ -466,6 +469,9 @@
                    end
                  else
                    statement_syssym:=cordconstnode.create(p1.resultdef.packedbitsize,sinttype,true);
+                 { type def is a struct with generic fields }
+                 if df_has_generic_fields in p1.resultdef.defoptions then
+                    include(statement_syssym.flags,nf_generic_para);
                  { p1 not needed !}
                  p1.destroy;
                end;
@@ -4167,7 +4173,10 @@
                 gendef:=generate_specialization_phase2(spezcontext,tstoreddef(gendef),false,'');
                 spezcontext.free;
                 spezcontext:=nil;
-                gensym:=gendef.typesym;
+                if gendef.typ=errordef then
+                  gensym:=generrorsym
+                else
+                  gensym:=gendef.typesym;
               end;
             procdef:
               begin
diff -ur compiler/pgentype.pas compiler/pgentype.pas
--- compiler/pgentype.pas	2019-05-04 11:21:36.240755700 -0400
+++ compiler/pgentype.pas	2019-05-04 10:01:26.150428600 -0400
@@ -28,7 +28,7 @@
 uses
   cclasses,
   globtype,
-  symtype,symbase;
+  symconst,symtype,symbase;
 
 const
   inline_specialization_block_types = [bt_type,bt_var_type,bt_const_type,bt_body];
@@ -42,7 +42,7 @@
 
   tspecializationcontext=class
   public
-    genericdeflist : tfpobjectlist;
+    paramlist : tfpobjectlist;
     poslist : tfplist;
     prettyname : ansistring;
     specializename : ansistring;
@@ -58,7 +58,7 @@
 
 constructor tspecializationcontext.create;
 begin
-  genericdeflist:=tfpobjectlist.create(false);
+  paramlist:=tfpobjectlist.create(false);
   poslist:=tfplist.create;
 end;
 
@@ -66,7 +66,7 @@
 var
   i : longint;
 begin
-  genericdeflist.free;
+  paramlist.free;
   for i:=0 to poslist.count-1 do
     dispose(pfileposinfo(poslist[i]));
   poslist.free;
diff -ur compiler/pgenutil.pas compiler/pgenutil.pas
--- compiler/pgenutil.pas	2019-05-04 11:21:36.303260700 -0400
+++ compiler/pgenutil.pas	2019-05-04 11:12:01.223659000 -0400
@@ -42,9 +42,9 @@
     function generate_specialization_phase1(out context:tspecializationcontext;genericdef:tdef;symname:string):tdef;inline;
     function generate_specialization_phase1(out context:tspecializationcontext;genericdef:tdef;parsedtype:tdef;symname:string;parsedpos:tfileposinfo):tdef;
     function generate_specialization_phase2(context:tspecializationcontext;genericdef:tstoreddef;parse_class_parent:boolean;_prettyname:ansistring):tdef;
-    function check_generic_constraints(genericdef:tstoreddef;paradeflist:tfpobjectlist;poslist:tfplist):boolean;
+    function check_generic_constraints(genericdef:tstoreddef;paramlist:tfpobjectlist;poslist:tfplist):boolean;
     function parse_generic_parameters(allowconstraints:boolean):tfphashobjectlist;
-    function parse_generic_specialization_types(genericdeflist:tfpobjectlist;poslist:tfplist;out prettyname,specializename:ansistring):boolean;
+    function parse_generic_specialization_types(paramlist:tfpobjectlist;poslist:tfplist;out prettyname,specializename:ansistring):boolean;
     procedure insert_generic_parameter_types(def:tstoreddef;genericdef:tstoreddef;genericlist:tfphashobjectlist);
     procedure maybe_insert_generic_rename_symbol(const name:tidstring;genericlist:tfphashobjectlist);
     function generate_generic_name(const name:tidstring;specializename:ansistring;owner_hierarchy:string):tidstring;
@@ -63,18 +63,163 @@
 
 uses
   { common }
-  cutils,fpccrc,
+  sysutils,cutils,fpccrc,
   { global }
-  globals,tokens,verbose,finput,
+  globals,tokens,verbose,finput,constexp,
   { symtable }
-  symconst,symsym,symtable,defcmp,procinfo,
+  symconst,symsym,symtable,defcmp,defutil,procinfo,
   { modules }
   fmodule,
-  node,nobj,
+  node,nobj,ncon,
   { parser }
   scanner,
   pbase,pexpr,pdecsub,ptype,psub,pparautl;
 
+  type
+    tdeftypeset = set of tdeftyp;
+  const
+    tgeneric_param_const_types : tdeftypeset = [orddef,stringdef,arraydef,floatdef,setdef,pointerdef,undefineddef];
+    tgeneric_param_nodes : tnodetypeset = [typen,ordconstn,stringconstn,realconstn,setconstn,niln];
+
+    function get_generic_param_def(sym:tsym):tdef;
+      begin
+        if sym.typ=constsym then
+          result:=tconstsym(sym).constdef
+        else
+          result:=ttypesym(sym).typedef;
+      end;
+
+    function is_generic_param_const(sym:tsym):boolean;
+      begin
+        if sym.typ=constsym then
+          result:=tconstsym(sym).consttyp<>constundefined
+        else
+          result:=false;
+      end;
+
+    function compare_orddef_by_range(param1,param2:torddef;value:tconstvalue):boolean;
+      begin
+        if (value.len<param2.low) or (value.len>param2.high) then
+          result:=false
+        else
+          result:=true;
+      end;
+
+    function compare_generic_params(param1,param2:tdef;constparamsym:tconstsym):boolean;
+      begin
+        if (param1.typ=orddef) and (param2.typ=orddef) then
+          begin
+            if is_boolean(param2) then
+              result:=is_boolean(param1)
+            else if is_char(param2) then
+              result:=is_char(param1)
+            else if compare_orddef_by_range(torddef(param1),torddef(param2),constparamsym.value) then
+              result:=true
+            else
+              result:=false;
+          end
+        { arraydef is string constant so it's compatible with stringdef }
+        else if (param1.typ=arraydef) and (param2.typ=stringdef) then
+          result:=true
+        { integer ords are compatible with float }
+        else if (param1.typ=orddef) and is_integer(param1) and (param2.typ=floatdef) then
+          result:=true
+        { undefined def is compatible with all types }
+        else if param2.typ=undefineddef then
+          result:=true
+        { sets require stricter checks }
+        else if is_set(param2) then
+          result:=equal_defs(param1,param2)
+        else
+          result:=param1.typ=param2.typ;
+      end;
+
+    function create_generic_constsym(fromdef:tdef;node:tnode;out prettyname:string):tconstsym;
+      const
+        undefinedname = 'undefined';
+      var
+        sym : tconstsym;
+        setdef : tsetdef;
+        enumsym : tsym;
+        enumname : string;
+        sp : pchar;
+        ps : ^tconstset;
+        pd : ^bestreal;
+        i : integer;
+      begin
+        if node=nil then
+          begin
+            sym:=cconstsym.create_undefined(undefinedname,fromdef);
+            sym.owner:=fromdef.owner;
+            prettyname:='';
+            result:=sym;
+            exit;
+          end;
+        case node.nodetype of
+          ordconstn:
+            begin
+              sym:=cconstsym.create_ord(undefinedname,constord,tordconstnode(node).value,fromdef);
+              prettyname:=inttostr(tordconstnode(node).value.svalue);
+            end;
+          stringconstn:
+            begin
+              getmem(sp,tstringconstnode(node).len+1);
+              move(tstringconstnode(node).value_str^,sp^,tstringconstnode(node).len+1);
+              sym:=cconstsym.create_string(undefinedname,conststring,sp,tstringconstnode(node).len,fromdef);
+              prettyname:=''''+tstringconstnode(node).value_str+'''';
+            end;
+          realconstn:
+            begin
+              new(pd);
+              pd^:=trealconstnode(node).value_real;
+              sym:=cconstsym.create_ptr(undefinedname,constreal,pd,fromdef);
+              prettyname:=floattostr(trealconstnode(node).value_real);
+            end;
+          setconstn:
+            begin
+              new(ps);
+              ps^:=tsetconstnode(node).value_set^;
+              sym:=cconstsym.create_ptr(undefinedname,constset,ps,fromdef);
+              setdef:=tsetdef(tsetconstnode(node).resultdef);
+              prettyname:='[';
+              for i := setdef.setbase to setdef.setmax do
+                if i in tsetconstnode(node).value_set^ then
+                  begin
+                    if setdef.elementdef.typ=enumdef then
+                      enumsym:=tenumdef(setdef.elementdef).int2enumsym(i)
+                    else
+                      enumsym:=nil;
+                    if assigned(enumsym) then
+                      enumname:=enumsym.realname
+                    else if setdef.elementdef.typ=orddef then
+                      begin
+                        if torddef(setdef.elementdef).ordtype=uchar then
+                          enumname:=chr(i)
+                        else
+                          enumname:=tostr(i);
+                      end
+                    else
+                      enumname:=tostr(i);
+                    if length(prettyname) > 1 then
+                      prettyname:=prettyname+','+enumname
+                    else
+                      prettyname:=prettyname+enumname;
+                  end;
+              prettyname:=prettyname+']';
+            end;
+          niln:
+            begin
+              { only "nil" is available for pointer constants }
+              sym:=cconstsym.create_ord(undefinedname,constnil,0,fromdef);
+              prettyname:='nil';
+            end;
+          else
+            internalerror(2019021601);
+        end;
+        { the sym needs an owner for later checks so us the typeparam owner }
+        sym.owner:=fromdef.owner;
+        result:=sym;
+      end;
 
     procedure maybe_add_waiting_unit(tt:tdef);
       var
@@ -104,203 +249,232 @@
           end;
       end;
 
-    function check_generic_constraints(genericdef:tstoreddef;paradeflist:tfpobjectlist;poslist:tfplist):boolean;
+    function check_generic_constraints(genericdef:tstoreddef;paramlist:tfpobjectlist;poslist:tfplist):boolean;
       var
         i,j,
         intfcount : longint;
         formaldef,
         paradef : tstoreddef;
+        genparadef : tdef;
         objdef,
         paraobjdef,
         formalobjdef : tobjectdef;
         intffound : boolean;
         filepos : tfileposinfo;
+        //paratype : tconsttyp;
+        is_const : boolean;
       begin
         { check whether the given specialization parameters fit to the eventual
           constraints of the generic }
         if not assigned(genericdef.genericparas) or (genericdef.genericparas.count=0) then
           internalerror(2012101001);
-        if genericdef.genericparas.count<>paradeflist.count then
+        if genericdef.genericparas.count<>paramlist.count then
           internalerror(2012101002);
-        if paradeflist.count<>poslist.count then
+        if paramlist.count<>poslist.count then
           internalerror(2012120801);
         result:=true;
         for i:=0 to genericdef.genericparas.count-1 do
           begin
             filepos:=pfileposinfo(poslist[i])^;
-            formaldef:=tstoreddef(ttypesym(genericdef.genericparas[i]).typedef);
-            if formaldef.typ=undefineddef then
-              { the parameter is of unspecified type, so no need to check }
-              continue;
-            if not (df_genconstraint in formaldef.defoptions) or
-                not assigned(formaldef.genconstraintdata) then
-              internalerror(2013021602);
-            paradef:=tstoreddef(paradeflist[i]);
-            { undefineddef is compatible with anything }
-            if formaldef.typ=undefineddef then
-              continue;
-            if paradef.typ<>formaldef.typ then
+            paradef:=tstoreddef(get_generic_param_def(tsym(paramlist[i])));
+            is_const:=is_generic_param_const(tsym(paramlist[i]));
+            genparadef:=genericdef.get_generic_param_def(i);
+            { validate const params }
+            if not genericdef.is_generic_param_const(i) and is_const then
               begin
-                case formaldef.typ of
-                  recorddef:
-                    { delphi has own fantasy about record constraint
-                      (almost non-nullable/non-nilable value type) }
-                    if m_delphi in current_settings.modeswitches then
-                      case paradef.typ of
-                        floatdef,enumdef,orddef:
-                          continue;
-                        objectdef:
-                          if tobjectdef(paradef).objecttype=odt_object then
-                            continue
-                          else
-                            MessagePos(filepos,type_e_record_type_expected);
+                MessagePos(filepos,type_e_mismatch);
+                exit(false);
+              end
+            else if genericdef.is_generic_param_const(i) then
+              begin
+                { param type mismatch (type <> const) }
+                 if genericdef.is_generic_param_const(i) <> is_const then
+                   begin
+                    MessagePos(filepos,type_e_mismatch);
+                    exit(false);
+                  end;
+                { type constrained param doesn't match type }
+                if not compare_generic_params(paradef,genericdef.get_generic_param_def(i),tconstsym(paramlist[i])) then
+                  begin
+                    MessagePos2(filepos,type_e_incompatible_types,FullTypeName(paradef,genparadef),FullTypeName(genparadef,paradef));
+                    exit(false);
+                  end;
+              end;
+            { test constraints for non-const params }
+            if not genericdef.is_generic_param_const(i) then
+              begin
+                formaldef:=tstoreddef(ttypesym(genericdef.genericparas[i]).typedef);
+                if formaldef.typ=undefineddef then
+                  { the parameter is of unspecified type, so no need to check }
+                  continue;
+                if not (df_genconstraint in formaldef.defoptions) or
+                    not assigned(formaldef.genconstraintdata) then
+                  internalerror(2013021602);
+                { undefineddef is compatible with anything }
+                if formaldef.typ=undefineddef then
+                  continue;
+                if paradef.typ<>formaldef.typ then
+                  begin
+                    case formaldef.typ of
+                      recorddef:
+                        { delphi has own fantasy about record constraint
+                          (almost non-nullable/non-nilable value type) }
+                        if m_delphi in current_settings.modeswitches then
+                          case paradef.typ of
+                            floatdef,enumdef,orddef:
+                              continue;
+                            objectdef:
+                              if tobjectdef(paradef).objecttype=odt_object then
+                                continue
+                              else
+                                MessagePos(filepos,type_e_record_type_expected);
+                            else
+                              MessagePos(filepos,type_e_record_type_expected);
+                          end
                         else
                           MessagePos(filepos,type_e_record_type_expected);
-                      end
-                    else
-                      MessagePos(filepos,type_e_record_type_expected);
-                  objectdef:
-                    case tobjectdef(formaldef).objecttype of
-                      odt_class,
-                      odt_javaclass:
-                        MessagePos1(filepos,type_e_class_type_expected,paradef.typename);
-                      odt_interfacecom,
-                      odt_interfacecorba,
-                      odt_dispinterface,
-                      odt_interfacejava:
-                        MessagePos1(filepos,type_e_interface_type_expected,paradef.typename);
+                      objectdef:
+                        case tobjectdef(formaldef).objecttype of
+                          odt_class,
+                          odt_javaclass:
+                            MessagePos1(filepos,type_e_class_type_expected,paradef.typename);
+                          odt_interfacecom,
+                          odt_interfacecorba,
+                          odt_dispinterface,
+                          odt_interfacejava:
+                            MessagePos1(filepos,type_e_interface_type_expected,paradef.typename);
+                          else
+                            internalerror(2012101003);
+                        end;
+                      errordef:
+                        { ignore }
+                        ;
                       else
-                        internalerror(2012101003);
+                        internalerror(2012101004);
                     end;
-                  errordef:
-                    { ignore }
-                    ;
-                  else
-                    internalerror(2012101004);
-                end;
-                result:=false;
-              end
-            else
-              begin
-                { the paradef types are the same, so do special checks for the
-                  cases in which they are needed }
-                if formaldef.typ=objectdef then
-                  begin
-                    paraobjdef:=tobjectdef(paradef);
-                    formalobjdef:=tobjectdef(formaldef);
-                    if not (formalobjdef.objecttype in [odt_class,odt_javaclass,odt_interfacecom,odt_interfacecorba,odt_interfacejava,odt_dispinterface]) then
-                      internalerror(2012101102);
-                    if formalobjdef.objecttype in [odt_interfacecom,odt_interfacecorba,odt_interfacejava,odt_dispinterface] then
+                    result:=false;
+                  end
+                else
+                  begin
+                    { the paradef types are the same, so do special checks for the
+                      cases in which they are needed }
+                    if formaldef.typ=objectdef then
                       begin
-                        { this is either a concerete interface or class type (the
-                          latter without specific implemented interfaces) }
-                        case paraobjdef.objecttype of
-                          odt_interfacecom,
-                          odt_interfacecorba,
-                          odt_interfacejava,
-                          odt_dispinterface:
-                            begin
-                              if (oo_is_forward in paraobjdef.objectoptions) and
-                                  (paraobjdef.objecttype=formalobjdef.objecttype) and
-                                  (df_genconstraint in formalobjdef.defoptions) and
-                                  (
-                                    (formalobjdef.objecttype=odt_interfacecom) and
-                                    (formalobjdef.childof=interface_iunknown)
-                                  )
-                                  or
-                                  (
-                                    (formalobjdef.objecttype=odt_interfacecorba) and
-                                    (formalobjdef.childof=nil)
-                                  ) then
-                                continue;
-                              if not def_is_related(paraobjdef,formalobjdef.childof) then
+                        paraobjdef:=tobjectdef(paradef);
+                        formalobjdef:=tobjectdef(formaldef);
+                        if not (formalobjdef.objecttype in [odt_class,odt_javaclass,odt_interfacecom,odt_interfacecorba,odt_interfacejava,odt_dispinterface]) then
+                          internalerror(2012101102);
+                        if formalobjdef.objecttype in [odt_interfacecom,odt_interfacecorba,odt_interfacejava,odt_dispinterface] then
+                          begin
+                            { this is either a concerete interface or class type (the
+                              latter without specific implemented interfaces) }
+                            case paraobjdef.objecttype of
+                              odt_interfacecom,
+                              odt_interfacecorba,
+                              odt_interfacejava,
+                              odt_dispinterface:
                                 begin
-                                  MessagePos2(filepos,type_e_incompatible_types,paraobjdef.typename,formalobjdef.childof.typename);
-                                  result:=false;
+                                  if (oo_is_forward in paraobjdef.objectoptions) and
+                                      (paraobjdef.objecttype=formalobjdef.objecttype) and
+                                      (df_genconstraint in formalobjdef.defoptions) and
+                                      (
+                                        (formalobjdef.objecttype=odt_interfacecom) and
+                                        (formalobjdef.childof=interface_iunknown)
+                                      )
+                                      or
+                                      (
+                                        (formalobjdef.objecttype=odt_interfacecorba) and
+                                        (formalobjdef.childof=nil)
+                                      ) then
+                                    continue;
+                                  if not def_is_related(paraobjdef,formalobjdef.childof) then
+                                    begin
+                                      MessagePos2(filepos,type_e_incompatible_types,paraobjdef.typename,formalobjdef.childof.typename);
+                                      result:=false;
+                                    end;
                                 end;
-                            end;
-                          odt_class,
-                          odt_javaclass:
-                            begin
-                              objdef:=paraobjdef;
-                              intffound:=false;
-                              while assigned(objdef) do
+                              odt_class,
+                              odt_javaclass:
                                 begin
-                                  for j:=0 to objdef.implementedinterfaces.count-1 do
-                                    if timplementedinterface(objdef.implementedinterfaces[j]).intfdef=formalobjdef.childof then
-                                      begin
-                                        intffound:=true;
+                                  objdef:=paraobjdef;
+                                  intffound:=false;
+                                  while assigned(objdef) do
+                                    begin
+                                      for j:=0 to objdef.implementedinterfaces.count-1 do
+                                        if timplementedinterface(objdef.implementedinterfaces[j]).intfdef=formalobjdef.childof then
+                                          begin
+                                            intffound:=true;
+                                            break;
+                                          end;
+                                      if intffound then
                                         break;
-                                      end;
-                                  if intffound then
-                                    break;
-                                  objdef:=objdef.childof;
+                                      objdef:=objdef.childof;
+                                    end;
+                                  result:=intffound;
+                                  if not result then
+                                    MessagePos2(filepos,parser_e_class_doesnt_implement_interface,paraobjdef.typename,formalobjdef.childof.typename);
+                                end;
+                              else
+                                begin
+                                  MessagePos1(filepos,type_e_class_or_interface_type_expected,paraobjdef.typename);
+                                  result:=false;
                                 end;
-                              result:=intffound;
-                              if not result then
-                                MessagePos2(filepos,parser_e_class_doesnt_implement_interface,paraobjdef.typename,formalobjdef.childof.typename);
-                            end;
-                          else
-                            begin
-                              MessagePos1(filepos,type_e_class_or_interface_type_expected,paraobjdef.typename);
-                              result:=false;
                             end;
-                        end;
-                      end
-                    else
-                      begin
-                        { this is either a "class" or a concrete instance with
-                          or without implemented interfaces }
-                        if not (paraobjdef.objecttype in [odt_class,odt_javaclass]) then
-                          begin
-                            MessagePos1(filepos,type_e_class_type_expected,paraobjdef.typename);
-                            result:=false;
-                            continue;
-                          end;
-                        { for forward declared classes we allow pure TObject/class declarations }
-                        if (oo_is_forward in paraobjdef.objectoptions) and
-                            (df_genconstraint in formaldef.defoptions) then
-                          begin
-                            if (formalobjdef.childof=class_tobject) and
-                                not formalobjdef.implements_any_interfaces then
-                              continue;
-                          end;
-                        if assigned(formalobjdef.childof) and
-                            not def_is_related(paradef,formalobjdef.childof) then
-                          begin
-                            MessagePos2(filepos,type_e_incompatible_types,paraobjdef.typename,formalobjdef.childof.typename);
-                            result:=false;
-                          end;
-                        intfcount:=0;
-                        for j:=0 to formalobjdef.implementedinterfaces.count-1 do
+                          end
+                        else
                           begin
-                            objdef:=paraobjdef;
-                            while assigned(objdef) do
+                            { this is either a "class" or a concrete instance with
+                              or without implemented interfaces }
+                            if not (paraobjdef.objecttype in [odt_class,odt_javaclass]) then
+                              begin
+                                MessagePos1(filepos,type_e_class_type_expected,paraobjdef.typename);
+                                result:=false;
+                                continue;
+                              end;
+                            { for forward declared classes we allow pure TObject/class declarations }
+                            if (oo_is_forward in paraobjdef.objectoptions) and
+                                (df_genconstraint in formaldef.defoptions) then
                               begin
-                                intffound:=assigned(
-                                             find_implemented_interface(objdef,
-                                               timplementedinterface(formalobjdef.implementedinterfaces[j]).intfdef
-                                             )
-                                           );
+                                if (formalobjdef.childof=class_tobject) and
+                                    not formalobjdef.implements_any_interfaces then
+                                  continue;
+                              end;
+                            if assigned(formalobjdef.childof) and
+                                not def_is_related(paradef,formalobjdef.childof) then
+                              begin
+                                MessagePos2(filepos,type_e_incompatible_types,paraobjdef.typename,formalobjdef.childof.typename);
+                                result:=false;
+                              end;
+                            intfcount:=0;
+                            for j:=0 to formalobjdef.implementedinterfaces.count-1 do
+                              begin
+                                objdef:=paraobjdef;
+                                while assigned(objdef) do
+                                  begin
+                                    intffound:=assigned(
+                                                 find_implemented_interface(objdef,
+                                                   timplementedinterface(formalobjdef.implementedinterfaces[j]).intfdef
+                                                 )
+                                               );
+                                    if intffound then
+                                      break;
+                                    objdef:=objdef.childof;
+                                  end;
                                 if intffound then
-                                  break;
-                                objdef:=objdef.childof;
+                                  inc(intfcount)
+                                else
+                                  MessagePos2(filepos,parser_e_class_doesnt_implement_interface,paraobjdef.typename,timplementedinterface(formalobjdef.implementedinterfaces[j]).intfdef.typename);
                               end;
-                            if intffound then
-                              inc(intfcount)
-                            else
-                              MessagePos2(filepos,parser_e_class_doesnt_implement_interface,paraobjdef.typename,timplementedinterface(formalobjdef.implementedinterfaces[j]).intfdef.typename);
+                            if intfcount<>formalobjdef.implementedinterfaces.count then
+                              result:=false;
                           end;
-                        if intfcount<>formalobjdef.implementedinterfaces.count then
-                          result:=false;
                       end;
                   end;
               end;
           end;
       end;
 
-
-    function parse_generic_specialization_types_internal(genericdeflist:tfpobjectlist;poslist:tfplist;out prettyname,specializename:ansistring;parsedtype:tdef;parsedpos:tfileposinfo):boolean;
+    function parse_generic_specialization_types_internal(paramlist:tfpobjectlist;poslist:tfplist;out prettyname,specializename:ansistring;parsedtype:tdef;parsedpos:tfileposinfo):boolean;
       var
         old_block_type : tblock_type;
         first : boolean;
@@ -310,9 +484,12 @@
         namepart : string;
         prettynamepart : ansistring;
         module : tmodule;
+        //paramdef : tgenericparamdef;
+        constprettyname : string;
+        validparam : boolean;
       begin
         result:=true;
-        if genericdeflist=nil then
+        if paramlist=nil then
           internalerror(2012061401);
         { set the block type to type, so that the parsed type are returned as
           ttypenode (e.g. classes are in non type-compatible blocks returned as
@@ -324,7 +501,7 @@
         first:=not assigned(parsedtype);
         if assigned(parsedtype) then
           begin
-            genericdeflist.Add(parsedtype);
+            paramlist.Add(parsedtype.typesym);
             module:=find_module_from_symtable(parsedtype.owner);
             if not assigned(module) then
               internalerror(2016112801);
@@ -351,7 +528,9 @@
             block_type:=bt_type;
             tmpparampos:=current_filepos;
             typeparam:=factor(false,[ef_type_only]);
-            if typeparam.nodetype=typen then
+            { determine if the typeparam node is a valid type or const }
+            validparam:=typeparam.nodetype in tgeneric_param_nodes;
+            if validparam then
               begin
                 if tstoreddef(typeparam.resultdef).is_generic and
                     (
@@ -367,31 +546,47 @@
                   end;
                 if typeparam.resultdef.typ<>errordef then
                   begin
-                    if not assigned(typeparam.resultdef.typesym) then
+                    if (typeparam.nodetype = typen) and not assigned(typeparam.resultdef.typesym) then
                       message(type_e_generics_cannot_reference_itself)
-                    else if (typeparam.resultdef.typ<>errordef) then
+                    else 
+                    if (typeparam.resultdef.typ<>errordef) then
                       begin
-                        genericdeflist.Add(typeparam.resultdef);
+                        { all non-type nodes are considered const }
+                        if typeparam.nodetype <> typen then
+                          paramlist.Add(create_generic_constsym(typeparam.resultdef,typeparam,constprettyname))
+                        else
+                          begin
+                            constprettyname:='';
+                            paramlist.Add(typeparam.resultdef.typesym);
+                          end;
                         module:=find_module_from_symtable(typeparam.resultdef.owner);
                         if not assigned(module) then
                           internalerror(2016112802);
                         namepart:='_$'+hexstr(module.moduleid,8)+'$$'+typeparam.resultdef.unique_id_str;
+                        if constprettyname <> '' then
+                          namepart:=namepart+'$$'+constprettyname;
                         { we use the full name of the type to uniquely identify it }
-                        if (symtablestack.top.symtabletype=parasymtable) and
-                            (symtablestack.top.defowner.typ=procdef) and
-                            (typeparam.resultdef.owner=symtablestack.top) then
-                          begin
-                            { special handling for specializations inside generic function declarations }
-                            prettynamepart:=tdef(symtablestack.top.defowner).fullownerhierarchyname(true)+tprocdef(symtablestack.top.defowner).procsym.prettyname;
-                          end
-                        else
+                        if typeparam.nodetype = typen then
                           begin
-                            prettynamepart:=typeparam.resultdef.fullownerhierarchyname(true);
+                            if (symtablestack.top.symtabletype=parasymtable) and
+                                (symtablestack.top.defowner.typ=procdef) and
+                                (typeparam.resultdef.owner=symtablestack.top) then
+                              begin
+                                { special handling for specializations inside generic function declarations }
+                                prettynamepart:=tdef(symtablestack.top.defowner).fullownerhierarchyname(true)+tprocdef(symtablestack.top.defowner).procsym.prettyname;
+                              end
+                            else
+                              begin
+                                prettynamepart:=typeparam.resultdef.fullownerhierarchyname(true);
+                              end;
                           end;
                         specializename:=specializename+namepart;
                         if not first then
                           prettyname:=prettyname+',';
-                        prettyname:=prettyname+prettynamepart+typeparam.resultdef.typesym.prettyname;
+                        if constprettyname <> '' then
+                          prettyname:=prettyname+constprettyname
+                        else
+                          prettyname:=prettyname+prettynamepart+typeparam.resultdef.typesym.prettyname;
                       end;
                   end
                 else
@@ -411,12 +606,12 @@
       end;
 
 
-    function parse_generic_specialization_types(genericdeflist:tfpobjectlist;poslist:tfplist;out prettyname,specializename:ansistring):boolean;
+    function parse_generic_specialization_types(paramlist:tfpobjectlist;poslist:tfplist;out prettyname,specializename:ansistring):boolean;
       var
         dummypos : tfileposinfo;
       begin
         FillChar(dummypos, SizeOf(tfileposinfo), 0);
-        result:=parse_generic_specialization_types_internal(genericdeflist,poslist,prettyname,specializename,nil,dummypos);
+        result:=parse_generic_specialization_types_internal(paramlist,poslist,prettyname,specializename,nil,dummypos);
       end;
 
 
@@ -578,7 +773,7 @@
         context:=tspecializationcontext.create;
 
         { Parse type parameters }
-        err:=not parse_generic_specialization_types_internal(context.genericdeflist,context.poslist,context.prettyname,context.specializename,parsedtype,parsedpos);
+        err:=not parse_generic_specialization_types_internal(context.paramlist,context.poslist,context.prettyname,context.specializename,parsedtype,parsedpos);
         if err then
           begin
             if not try_to_consume(_GT) then
@@ -627,7 +822,7 @@
 
         { search a generic with the given count of params }
         countstr:='';
-        str(context.genericdeflist.Count,countstr);
+        str(context.paramlist.Count,countstr);
 
         genname:=genname+'$'+countstr;
         ugenname:=upper(genname);
@@ -656,7 +851,7 @@
             result:=generrordef;
             exit;
           end;
-
+        
         { we've found the correct def }
         if context.sym.typ=typesym then
           result:=tstoreddef(ttypesym(context.sym).typedef)
@@ -747,6 +942,7 @@
         hintsprocessed : boolean;
         pd : tprocdef;
         pdflags : tpdflags;
+        typedef : tstoreddef;
       begin
         if not assigned(context) then
           internalerror(2015052203);
@@ -755,7 +951,7 @@
 
         pd:=nil;
 
-        if not check_generic_constraints(genericdef,context.genericdeflist,context.poslist) then
+        if not check_generic_constraints(genericdef,context.paramlist,context.poslist) then
           begin
             { the parameters didn't fit the constraints, so don't continue with the
               specialization }
@@ -771,20 +967,19 @@
         else
           prettyname:=genericdef.typesym.prettyname;
         prettyname:=prettyname+'<'+context.prettyname+'>';
-
         generictypelist:=tfphashobjectlist.create(false);
 
         { build the list containing the types for the generic params }
         if not assigned(genericdef.genericparas) then
           internalerror(2013092601);
-        if context.genericdeflist.count<>genericdef.genericparas.count then
+        if context.paramlist.count<>genericdef.genericparas.count then
           internalerror(2013092603);
         for i:=0 to genericdef.genericparas.Count-1 do
           begin
             srsym:=tsym(genericdef.genericparas[i]);
             if not (sp_generic_para in srsym.symoptions) then
               internalerror(2013092602);
-            generictypelist.add(srsym.realname,tdef(context.genericdeflist[i]).typesym);
+            generictypelist.add(srsym.realname,context.paramlist[i]);
           end;
 
         { Special case if we are referencing the current defined object }
@@ -1199,8 +1394,8 @@
 
     function parse_generic_parameters(allowconstraints:boolean):tfphashobjectlist;
       var
-        generictype : ttypesym;
-        i,firstidx : longint;
+        generictype : tstoredsym;
+        i,firstidx,const_list_index : longint;
         srsymtable : tsymtable;
         basedef,def : tdef;
         defname : tidstring;
@@ -1208,22 +1403,88 @@
         doconsume : boolean;
         constraintdata : tgenericconstraintdata;
         old_block_type : tblock_type;
+        is_const,last_is_const : boolean;
+        last_token : ttoken;
+        last_type_pos : tfileposinfo;
       begin
         result:=tfphashobjectlist.create(false);
         firstidx:=0;
+        const_list_index:=0;
         old_block_type:=block_type;
         block_type:=bt_type;
+        is_const:=false;
+        last_is_const:=false;
+        last_token:=NOTOKEN;
+		last_type_pos:=default(tfileposinfo);
         repeat
+          if try_to_consume(_CONST) then
+            begin
+              { last param was const without semicolon terminator }
+              if (result.count>0) and last_is_const and (last_token<>_SEMICOLON) then
+                MessagePos2(last_type_pos,scan_f_syn_expected,arraytokeninfo[_SEMICOLON].str,arraytokeninfo[last_token].str);
+              is_const := true;
+              const_list_index := result.count;
+            end;
           if token=_ID then
             begin
-              generictype:=ctypesym.create(orgpattern,cundefinedtype,false);
+              if is_const then
+                begin
+                  { last param was type without semicolon terminator }
+                  if (result.count>0) and not last_is_const and (last_token<>_SEMICOLON) then
+                    MessagePos2(last_type_pos,scan_f_syn_expected,arraytokeninfo[_SEMICOLON].str,arraytokeninfo[last_token].str);
+                  generictype:=tconstsym.create_undefined(orgpattern,cundefinedtype);
+                end
+              else
+                begin
+                  { last param was const without semicolon terminator }
+                  if (result.count>0) and last_is_const and (last_token<>_SEMICOLON) then
+                    MessagePos2(last_type_pos,scan_f_syn_expected,arraytokeninfo[_SEMICOLON].str,arraytokeninfo[last_token].str);
+                  generictype:=ttypesym.create(orgpattern,cundefinedtype,false);
+                end;
               { type parameters need to be added as strict private }
               generictype.visibility:=vis_strictprivate;
               include(generictype.symoptions,sp_generic_para);
               result.add(orgpattern,generictype);
+              last_is_const:=is_const;
             end;
           consume(_ID);
-          if try_to_consume(_COLON) then
+          { const restriction }
+          if is_const then
+            begin
+              if try_to_consume(_COLON) then
+                begin
+                  def := nil;
+                  { parse the type and assign the const type to generictype  }
+                  single_type(def,[]);
+                  for i:=const_list_index to result.count-1 do
+                    begin
+                      { finalize constant information once type is known }
+                      if assigned(def) and (def.typ in tgeneric_param_const_types) then
+                        begin
+                          case def.typ of
+                            orddef:
+                              tconstsym(result[i]).consttyp:=constord;
+                            stringdef:
+                              tconstsym(result[i]).consttyp:=conststring;
+                            floatdef:
+                              tconstsym(result[i]).consttyp:=constreal;
+                            setdef:
+                              tconstsym(result[i]).consttyp:=constset;
+                            { pointer always refers to nil with constants }
+                            pointerdef:
+                              tconstsym(result[i]).consttyp:=constnil;
+                          end;
+                          tconstsym(result[i]).constdef:=def;
+                        end
+                      else
+                        Message(type_e_mismatch);
+                    end;
+                  { after type restriction const list terminates }
+                  is_const:=false;
+                end;
+            end
+          { type restriction }
+          else if try_to_consume(_COLON) then
             begin
               if not allowconstraints then
                 { TODO }
@@ -1338,6 +1599,7 @@
                     basedef:=cobjectdef.create(tobjectdef(def).objecttype,defname,tobjectdef(def),false);
                     constraintdata.interfaces.delete(0);
                   end;
+
               if basedef.typ<>errordef then
                 with tstoreddef(basedef) do
                   begin
@@ -1363,21 +1625,27 @@
                 begin
                   { two different typeless parameters are considered as incompatible }
                   for i:=firstidx to result.count-1 do
-                    begin
-                      ttypesym(result[i]).typedef:=cundefineddef.create(false);
-                      ttypesym(result[i]).typedef.typesym:=ttypesym(result[i]);
-                    end;
+                    if tsym(result[i]).typ<>constsym then
+                      begin
+                        ttypesym(result[i]).typedef:=cundefineddef.create(false);
+                        ttypesym(result[i]).typedef.typesym:=ttypesym(result[i]);
+                      end;
                   { a semicolon terminates a type parameter group }
                   firstidx:=result.count;
                 end;
             end;
+          if token = _SEMICOLON then
+            is_const:=false;
+          last_token:=token;
+          last_type_pos:=current_filepos;
         until not (try_to_consume(_COMMA) or try_to_consume(_SEMICOLON));
         { two different typeless parameters are considered as incompatible }
         for i:=firstidx to result.count-1 do
-          begin
-            ttypesym(result[i]).typedef:=cundefineddef.create(false);
-            ttypesym(result[i]).typedef.typesym:=ttypesym(result[i]);
-          end;
+          if tsym(result[i]).typ<>constsym then
+            begin
+              ttypesym(result[i]).typedef:=cundefineddef.create(false);
+              ttypesym(result[i]).typedef.typesym:=ttypesym(result[i]);
+            end;
         block_type:=old_block_type;
       end;
 
@@ -1385,7 +1653,9 @@
     procedure insert_generic_parameter_types(def:tstoreddef;genericdef:tstoreddef;genericlist:tfphashobjectlist);
       var
         i : longint;
-        generictype,sym : ttypesym;
+        generictype : tstoredsym;
+        generictypedef : tdef;
+        sym : tsym;
         st : tsymtable;
       begin
         def.genericdef:=genericdef;
@@ -1410,10 +1680,22 @@
           def.genericparas:=tfphashobjectlist.create(false);
         for i:=0 to genericlist.count-1 do
           begin
-            generictype:=ttypesym(genericlist[i]);
+            generictype:=tstoredsym(genericlist[i]);
             if assigned(generictype.owner) then
               begin
-                sym:=ctypesym.create(genericlist.nameofindex(i),generictype.typedef,true);
+                if generictype.typ=typesym then
+                  sym:=ctypesym.create(genericlist.nameofindex(i),ttypesym(generictype).typedef,true)
+                else if generictype.typ=constsym then
+                  { generictype is a constsym that was created in create_generic_constsym 
+                    during phase 1 so we pass this directly without copying }
+                  begin
+                    sym:=generictype;
+                    { the sym name is still undefined so we set it to match
+                      the generic param name so it's accessible }
+                    sym.realname:=genericlist.nameofindex(i);
+                  end
+                else
+                  internalerror(2019021602);
                 { type parameters need to be added as strict private }
                 sym.visibility:=vis_strictprivate;
                 st.insert(sym);
@@ -1421,13 +1703,17 @@
               end
             else
               begin
-                if (generictype.typedef.typ=undefineddef) and (generictype.typedef<>cundefinedtype) then
+                if generictype.typ=typesym then
                   begin
-                    { the generic parameters were parsed before the genericdef existed thus the
-                      undefineddefs were added as part of the parent symtable }
-                    if assigned(generictype.typedef.owner) then
-                      generictype.typedef.owner.DefList.Extract(generictype.typedef);
-                    generictype.typedef.changeowner(st);
+                    generictypedef:=ttypesym(generictype).typedef;
+                    if (generictypedef.typ=undefineddef) and (generictypedef<>cundefinedtype) then
+                      begin
+                        { the generic parameters were parsed before the genericdef existed thus the
+                          undefineddefs were added as part of the parent symtable }
+                        if assigned(generictypedef.owner) then
+                          generictypedef.owner.DefList.Extract(generictypedef);
+                        generictypedef.changeowner(st);
+                      end;
                   end;
                 st.insert(generictype);
                 include(generictype.symoptions,sp_generic_para);
diff -ur compiler/ptype.pas compiler/ptype.pas
--- compiler/ptype.pas	2019-05-04 11:21:36.365935500 -0400
+++ compiler/ptype.pas	2019-05-04 10:02:00.801275500 -0400
@@ -1436,7 +1436,9 @@
                                  highval:=tordconstnode(trangenode(pt).right).value;
                                  if highval<lowval then
                                   begin
-                                    Message(parser_e_array_lower_less_than_upper_bound);
+                                    { ignore error if node is generic param }
+                                    if not (nf_generic_para in pt.flags) then
+                                      Message(parser_e_array_lower_less_than_upper_bound);
                                     highval:=lowval;
                                   end
                                  else if (lowval<int64(low(asizeint))) or
Only in compiler: ryan_ppcx64.lpi
diff -ur compiler/symconst.pas compiler/symconst.pas
--- compiler/symconst.pas	2019-05-04 11:21:36.428440800 -0400
+++ compiler/symconst.pas	2019-05-04 10:02:00.598133900 -0400
@@ -231,7 +231,10 @@
       because we have to access this information in the symtable unit }
     df_llvm_no_struct_packing,
     { internal def that's not for any export }
-    df_internal
+    df_internal,
+    { the def was derived with generic type or const fields so the size
+      of the def can not be determined }
+    df_has_generic_fields
   );
   tdefoptions=set of tdefoption;
 
@@ -659,7 +662,7 @@
     arraydef,recorddef,pointerdef,orddef,
     stringdef,enumdef,procdef,objectdef,errordef,
     filedef,formaldef,setdef,procvardef,floatdef,
-    classrefdef,forwarddef,variantdef,undefineddef
+    classrefdef,forwarddef,variantdef,genericconstdef,undefineddef
   );
 
   { possible types for symtable entries }
@@ -700,7 +703,8 @@
   tconsttyp = (constnone,
     constord,conststring,constreal,
     constset,constpointer,constnil,
-    constresourcestring,constwstring,constguid
+    constresourcestring,constwstring,constguid,
+    constundefined
   );
 
   { RTTI information to store }
@@ -840,7 +844,7 @@
        'abstractdef','arraydef','recorddef','pointerdef','orddef',
        'stringdef','enumdef','procdef','objectdef','errordef',
        'filedef','formaldef','setdef','procvardef','floatdef',
-       'classrefdef','forwarddef','variantdef','undefineddef'
+       'classrefdef','forwarddef','variantdef','genconstdef','undefineddef'
      );
 
      EqualTypeName : array[tequaltype] of string[16] = (
diff -ur compiler/symdef.pas compiler/symdef.pas
--- compiler/symdef.pas	2019-05-04 11:21:36.490945500 -0400
+++ compiler/symdef.pas	2019-05-04 10:03:49.892616700 -0400
@@ -129,6 +129,9 @@
           function is_generic:boolean;
           { same as above for specializations }
           function is_specialization:boolean;
+          { generic utilities }
+          function is_generic_param_const(index:integer):boolean;inline;
+          function get_generic_param_def(index:integer):tdef;inline;
           { registers this def in the unit's deflist; no-op if already registered }
           procedure register_def; override;
           { add the def to the top of the symtable stack if it's not yet owned
@@ -2295,13 +2298,26 @@
          for i:=0 to genericparas.count-1 do
            begin
              sym:=tsym(genericparas[i]);
-             if sym.typ<>symconst.typesym then
+             { sym must be either a type or const }
+             if not (sym.typ in [symconst.typesym,symconst.constsym]) then
                internalerror(2014050903);
              if sym.owner.defowner<>self then
                exit(false);
            end;
      end;
 
+   function tstoreddef.is_generic_param_const(index:integer):boolean;
+     begin
+       result := tsym(genericparas[index]).typ = constsym;
+     end;  
+
+   function tstoreddef.get_generic_param_def(index:integer):tdef;
+     begin
+       if tsym(genericparas[index]).typ = constsym then
+         result := tconstsym(genericparas[index]).constdef
+       else
+         result := ttypesym(genericparas[index]).typedef;
+     end;
 
    function tstoreddef.is_specialization: boolean;
      var
@@ -2318,12 +2334,12 @@
            for i:=0 to genericparas.count-1 do
              begin
                sym:=tsym(genericparas[i]);
-               if sym.typ<>symconst.typesym then
+               { sym must be either a type or const }
+               if not (sym.typ in [symconst.typesym,symconst.constsym]) then
                  internalerror(2014050904);
                if sym.owner.defowner<>self then
                  exit(true);
              end;
-           result:=false;
          end;
      end;
 
diff -ur compiler/symsym.pas compiler/symsym.pas
--- compiler/symsym.pas	2019-05-04 11:21:36.537824600 -0400
+++ compiler/symsym.pas	2019-05-04 10:01:59.785568500 -0400
@@ -157,7 +157,7 @@
           fprettyname : ansistring;
           constructor create(const n : string;def:tdef;doregister:boolean);virtual;
           destructor destroy;override;
-          constructor ppuload(ppufile:tcompilerppufile);
+          constructor ppuload(ppufile:tcompilerppufile);virtual;
           { do not override this routine in platform-specific subclasses,
             override ppuwrite_platform instead }
           procedure ppuwrite(ppufile:tcompilerppufile);override;final;
@@ -392,6 +392,7 @@
           constructor create_ptr(const n : string;t : tconsttyp;v : pointer;def:tdef);virtual;
           constructor create_string(const n : string;t : tconsttyp;str:pchar;l:longint;def:tdef);virtual;
           constructor create_wstring(const n : string;t : tconsttyp;pw:pcompilerwidestring);virtual;
+          constructor create_undefined(const n : string;def: tdef);
           constructor ppuload(ppufile:tcompilerppufile);
           destructor  destroy;override;
           procedure buildderef;override;
@@ -1584,7 +1585,6 @@
           tparasymtable(parast).ppuwrite(ppufile);
       end;
 
-
 {****************************************************************************
                             TABSTRACTVARSYM
 ****************************************************************************}
@@ -2356,6 +2356,13 @@
          value.len:=getlengthwidestring(pw);
       end;
 
+    constructor tconstsym.create_undefined(const n : string;def: tdef);
+      begin
+        inherited create(constsym,n,true);
+        fillchar(value, sizeof(value), #0);
+        consttyp:=constundefined;
+        constdef:=def;
+      end;
 
     constructor tconstsym.ppuload(ppufile:tcompilerppufile);
       var
@@ -2428,7 +2435,8 @@
                new(pguid(value.valueptr));
                ppufile.getdata(value.valueptr^,sizeof(tguid));
              end;
-           constnil :
+           constnil,
+           constundefined :
              ppufile.getderef(constdefderef);
            else
              Message1(unit_f_ppu_invalid_entry,tostr(ord(consttyp)));
@@ -2460,7 +2468,7 @@
       begin
         inherited;
         case consttyp  of
-          constnil,constord,constreal,constpointer,constset,conststring,constresourcestring,constguid:
+          constnil,constord,constreal,constpointer,constset,conststring,constresourcestring,constguid,constundefined:
             constdefderef.build(constdef);
           constwstring:
             ;
@@ -2473,7 +2481,7 @@
     procedure tconstsym.deref;
       begin
         case consttyp of
-          constnil,constord,constreal,constpointer,constset,conststring,constresourcestring,constguid:
+          constnil,constord,constreal,constpointer,constset,conststring,constresourcestring,constguid,constundefined:
             constdef:=tdef(constdefderef.resolve);
           constwstring:
             constdef:=carraydef.getreusable(cwidechartype,getlengthwidestring(pcompilerwidestring(value.valueptr)));
@@ -2488,7 +2496,8 @@
          inherited ppuwrite(ppufile);
          ppufile.putbyte(byte(consttyp));
          case consttyp of
-           constnil :
+           constnil,
+           constundefined :
              ppufile.putderef(constdefderef);
            constord :
              begin
@@ -2641,7 +2650,6 @@
           result:=inherited prettyname;
       end;
 
-
 {****************************************************************************
                                   TSYSSYM
 ****************************************************************************}
diff -ur compiler/symtable.pas compiler/symtable.pas
--- compiler/symtable.pas	2019-05-04 11:21:36.584702800 -0400
+++ compiler/symtable.pas	2019-05-04 10:01:59.738689700 -0400
@@ -2916,7 +2916,7 @@
 
     function generate_objectpascal_helper_key(def:tdef):string;
       begin
-        if not assigned(def) then
+        if not assigned(def) or (def.typ = errordef) then
           internalerror(2013020501);
         if def.typ in [recorddef,objectdef] then
           result:=make_mangledname('',tabstractrecorddef(def).symtable,'')
diff -ur compiler/utils/ppuutils/ppudump.pp compiler/utils/ppuutils/ppudump.pp
--- compiler/utils/ppuutils/ppudump.pp	2019-05-04 11:21:36.631582400 -0400
+++ compiler/utils/ppuutils/ppudump.pp	2019-05-04 10:01:59.707422300 -0400
@@ -1561,7 +1561,8 @@
      { this should never happen for defs stored to a ppu file }
      (mask:df_not_registered_no_free;  str:'Unregistered/No free (invalid)'),
      (mask:df_llvm_no_struct_packing;  str:'LLVM unpacked struct'),
-     (mask:df_internal;       str:'Internal')
+     (mask:df_internal;       str:'Internal'),
+     (mask:df_has_generic_fields; str:'Has generic fields')
   );
   defstate : array[1..ord(high(tdefstate))] of tdefstateinfo=(
      (mask:ds_vmt_written;           str:'VMT Written'),

From 173ee8d64e4dec40db5f7346e311bd26d4bf3766 Mon Sep 17 00:00:00 2001
From: Ryan Joseph <genericptr@gmail.com>
Date: Tue, 6 Nov 2018 13:58:49 +0700
Subject: [PATCH] constants in generics

---
 compiler/defcmp.pas                |   9 +-
 compiler/htypechk.pas              |   2 +-
 compiler/ncnv.pas                  |   2 +-
 compiler/ncon.pas                  |  48 +-
 compiler/nmat.pas                  |   5 +-
 compiler/node.pas                  |  22 +-
 compiler/nset.pas                  |   7 +-
 compiler/pass_1.pas                |   5 +
 compiler/pdecl.pas                 |  54 ++-
 compiler/pdecvar.pas               |   4 +
 compiler/pexpr.pas                 |  17 +-
 compiler/pgentype.pas              |   8 +-
 compiler/pgenutil.pas              | 697 ++++++++++++++++++++---------
 compiler/ppu.pas                   |   2 +-
 compiler/pstatmnt.pas              |   7 +-
 compiler/ptype.pas                 |   4 +-
 compiler/symconst.pas              |  15 +-
 compiler/symdef.pas                |  22 +-
 compiler/symsym.pas                |  22 +-
 compiler/symtable.pas              |   2 +-
 compiler/utils/ppuutils/ppudump.pp |   4 +-
 tests/test/tgenconst1.pp           |  33 ++
 tests/test/tgenconst10.pp          |  13 +
 tests/test/tgenconst11.pp          |  21 +
 tests/test/tgenconst12.pp          |  16 +
 tests/test/tgenconst13.pp          |  20 +
 tests/test/tgenconst14.pp          |  29 ++
 tests/test/tgenconst15.pp          |  30 ++
 tests/test/tgenconst16.pp          |  86 ++++
 tests/test/tgenconst17.pp          |  36 ++
 tests/test/tgenconst18.pp          |  12 +
 tests/test/tgenconst19.pp          |  49 ++
 tests/test/tgenconst2.pp           |  12 +
 tests/test/tgenconst20.pp          |  24 +
 tests/test/tgenconst3.pp           |  16 +
 tests/test/tgenconst4.pp           |  11 +
 tests/test/tgenconst5.pp           |  24 +
 tests/test/tgenconst6.pp           |  21 +
 tests/test/tgenconst7.pp           |  11 +
 tests/test/tgenconst8.pp           |  11 +
 tests/test/tgenconst9.pp           |  11 +
 41 files changed, 1176 insertions(+), 268 deletions(-)
 create mode 100644 tests/test/tgenconst1.pp
 create mode 100644 tests/test/tgenconst10.pp
 create mode 100644 tests/test/tgenconst11.pp
 create mode 100644 tests/test/tgenconst12.pp
 create mode 100644 tests/test/tgenconst13.pp
 create mode 100644 tests/test/tgenconst14.pp
 create mode 100644 tests/test/tgenconst15.pp
 create mode 100644 tests/test/tgenconst16.pp
 create mode 100644 tests/test/tgenconst17.pp
 create mode 100644 tests/test/tgenconst18.pp
 create mode 100644 tests/test/tgenconst19.pp
 create mode 100644 tests/test/tgenconst2.pp
 create mode 100644 tests/test/tgenconst20.pp
 create mode 100644 tests/test/tgenconst3.pp
 create mode 100644 tests/test/tgenconst4.pp
 create mode 100644 tests/test/tgenconst5.pp
 create mode 100644 tests/test/tgenconst6.pp
 create mode 100644 tests/test/tgenconst7.pp
 create mode 100644 tests/test/tgenconst8.pp
 create mode 100644 tests/test/tgenconst9.pp

diff --git a/compiler/defcmp.pas b/compiler/defcmp.pas
index 3f5882f762..793dbbbe76 100644
--- a/compiler/defcmp.pas
+++ b/compiler/defcmp.pas
@@ -175,7 +175,6 @@ implementation
       symtable,symsym,symcpu,
       defutil,symutil;
 
-
     function compare_defs_ext(def_from,def_to : tdef;
                               fromtreetype : tnodetype;
                               var doconv : tconverttype;
@@ -337,9 +336,13 @@ implementation
                        internalerror(2012091302);
                      symfrom:=ttypesym(tstoreddef(def_from).genericparas[i]);
                      symto:=ttypesym(tstoreddef(def_to).genericparas[i]);
-                     if not (symfrom.typ=typesym) or not (symto.typ=typesym) then
+                     if not (symfrom.typ in [typesym,constsym]) or not (symto.typ in [typesym,constsym]) then
                        internalerror(2012121401);
-                     if not equal_defs(ttypesym(symfrom).typedef,ttypesym(symto).typedef) then
+                     if symto.typ <> symfrom.typ then
+                       diff:=true
+                     else if (symfrom.typ=constsym) and (symto.typ=constsym) and not equal_constsym(tconstsym(symfrom),tconstsym(symto),true) then
+                       diff:=true
+                     else if not equal_defs(ttypesym(symfrom).typedef,ttypesym(symto).typedef) then
                        diff:=true;
                      if diff then
                        break;
diff --git a/compiler/htypechk.pas b/compiler/htypechk.pas
index 07c035dc26..2358ea4b6d 100644
--- a/compiler/htypechk.pas
+++ b/compiler/htypechk.pas
@@ -2697,7 +2697,7 @@ implementation
               internalerror(2015060301);
             { check whether the given parameters are compatible
               to the def's constraints }
-            if not check_generic_constraints(pd,spezcontext.genericdeflist,spezcontext.poslist) then
+            if not check_generic_constraints(pd,spezcontext.paramlist,spezcontext.poslist) then
               exit;
             def:=generate_specialization_phase2(spezcontext,pd,false,'');
             case def.typ of
diff --git a/compiler/ncnv.pas b/compiler/ncnv.pas
index 31135872da..cb246b6fc6 100644
--- a/compiler/ncnv.pas
+++ b/compiler/ncnv.pas
@@ -3033,7 +3033,7 @@ implementation
                        { for constant values on absolute variables, swaping is required }
                        if (target_info.endian = endian_big) and (nf_absolute in flags) then
                          swap_const_value(tordconstnode(left).value,tordconstnode(left).resultdef.size);
-                       if not(nf_internal in flags) then
+                       if not((nf_internal in flags) or (nf_generic_para in flags)) then
                          testrange(resultdef,tordconstnode(left).value,(nf_explicit in flags)
                                    or (nf_absolute in flags),false);
                        { swap value back, but according to new type }
diff --git a/compiler/ncon.pas b/compiler/ncon.pas
index ae94637c28..fadf704935 100644
--- a/compiler/ncon.pas
+++ b/compiler/ncon.pas
@@ -279,6 +279,7 @@ implementation
         p1  : tnode;
         len : longint;
         pc  : pchar;
+        value_set : pconstset;
       begin
         p1:=nil;
         case p.consttyp of
@@ -304,18 +305,57 @@ implementation
           constwstring :
             p1:=cstringconstnode.createunistr(pcompilerwidestring(p.value.valueptr));
           constreal :
-            p1:=crealconstnode.create(pbestreal(p.value.valueptr)^,p.constdef);
+            begin
+              if (sp_generic_para in p.symoptions) and not (sp_generic_const in p.symoptions) then
+                p1:=crealconstnode.create(default(bestreal),p.constdef)
+              else
+                p1:=crealconstnode.create(pbestreal(p.value.valueptr)^,p.constdef);
+            end;
           constset :
-            p1:=csetconstnode.create(pconstset(p.value.valueptr),p.constdef);
+            begin
+              if sp_generic_const in p.symoptions then
+                begin
+                  new(value_set);
+                  value_set^:=pconstset(p.value.valueptr)^;
+                  p1:=csetconstnode.create(value_set,p.constdef);
+                end
+              else if sp_generic_para in p.symoptions then
+                begin
+                  new(value_set);
+                  p1:=csetconstnode.create(value_set,p.constdef);
+                end
+              else
+                p1:=csetconstnode.create(pconstset(p.value.valueptr),p.constdef);
+            end;
           constpointer :
-            p1:=cpointerconstnode.create(p.value.valueordptr,p.constdef);
+            begin
+              if sp_generic_para in p.symoptions then
+                p1:=cpointerconstnode.create(default(tconstptruint),p.constdef)
+              else
+                p1:=cpointerconstnode.create(p.value.valueordptr,p.constdef);
+            end;
           constnil :
             p1:=cnilnode.create;
+          { constundefined is a placeholder for unrestricted generic const params
+            so we just treat it as a nil node. }
+          constundefined :
+            begin
+              p1:=cnilnode.create;
+              p1.resultdef:=p.constdef;
+            end;
           constguid :
-            p1:=cguidconstnode.create(pguid(p.value.valueptr)^);
+            begin
+              if sp_generic_para in p.symoptions then
+                p1:=cguidconstnode.create(default(tguid))
+              else
+                p1:=cguidconstnode.create(pguid(p.value.valueptr)^);
+            end;
           else
             internalerror(200205103);
         end;
+        { transfer generic param flag from symbol to node }
+        if sp_generic_para in p.symoptions then
+          include(p1.flags,nf_generic_para);
         genconstsymtree:=p1;
       end;
 
diff --git a/compiler/nmat.pas b/compiler/nmat.pas
index 355b493da4..d10dff6128 100644
--- a/compiler/nmat.pas
+++ b/compiler/nmat.pas
@@ -129,7 +129,10 @@ implementation
               end;
             if rv = 0 then
               begin
-                Message(parser_e_division_by_zero);
+                { if the node is derived from a generic const parameter
+                  then don't issue an error }
+                if not (nf_generic_para in flags) then
+                  Message(parser_e_division_by_zero);
                 { recover }
                 tordconstnode(right).value := 1;
               end;
diff --git a/compiler/node.pas b/compiler/node.pas
index b8600000bf..33a85b1493 100644
--- a/compiler/node.pas
+++ b/compiler/node.pas
@@ -194,7 +194,8 @@ interface
           'loadparentfpn',
           'objcselectorn',
           'objcprotocoln',
-          'specializen');
+          'specializen'
+          );
 
       { a set containing all const nodes }
       nodetype_const = [ordconstn,
@@ -272,10 +273,13 @@ interface
          nf_block_with_exit,
 
          { tloadvmtaddrnode }
-         nf_ignore_for_wpo  { we know that this loadvmtaddrnode cannot be used to construct a class instance }
+         nf_ignore_for_wpo,  { we know that this loadvmtaddrnode cannot be used to construct a class instance }
 
-         { WARNING: there are now 31 elements in this type, and a set of this
-             type is written to the PPU. So before adding more than 32 elements,
+         { node is derived from generic parameter }
+         nf_generic_para
+
+         { WARNING: there are now 32 elements in this type, and a set of this
+             type is written to the PPU. So before adding more elements,
              either move some flags to specific nodes, or stream a normalset
              to the ppu
          }
@@ -983,6 +987,9 @@ implementation
     constructor tunarynode.create(t:tnodetype;l : tnode);
       begin
          inherited create(t);
+         { transfer generic paramater flag }
+         if assigned(l) and (nf_generic_para in l.flags) then
+           include(flags,nf_generic_para);
          left:=l;
       end;
 
@@ -1078,7 +1085,12 @@ implementation
     constructor tbinarynode.create(t:tnodetype;l,r : tnode);
       begin
          inherited create(t,l);
-         right:=r
+         { transfer generic paramater flag }
+         if assigned(l) and (nf_generic_para in l.flags) then
+           include(flags,nf_generic_para)
+         else if assigned(r) and (nf_generic_para in r.flags) then
+           include(flags,nf_generic_para);
+         right:=r;
       end;
 
 
diff --git a/compiler/nset.pas b/compiler/nset.pas
index 6270ec582e..bd031e6a86 100644
--- a/compiler/nset.pas
+++ b/compiler/nset.pas
@@ -239,7 +239,7 @@ implementation
            internalerror(20021126);
 
          t:=self;
-         if isbinaryoverloaded(t,[]) then
+         if isbinaryoverloaded(t,[]) then
            begin
              result:=t;
              exit;
@@ -392,8 +392,9 @@ implementation
          { both types must be compatible }
          if compare_defs(left.resultdef,right.resultdef,left.nodetype)=te_incompatible then
            IncompatibleTypes(left.resultdef,right.resultdef);
-         { Check if only when its a constant set }
-         if (left.nodetype=ordconstn) and (right.nodetype=ordconstn) then
+         { check if only when its a constant set and
+           ignore range nodes which are generic parameter derived }
+         if not (nf_generic_para in flags) and (left.nodetype=ordconstn) and (right.nodetype=ordconstn) then
           begin
             { upper limit must be greater or equal than lower limit }
             if (tordconstnode(left).value>tordconstnode(right).value) and
diff --git a/compiler/pass_1.pas b/compiler/pass_1.pas
index b9f7f847ee..ed314072e1 100644
--- a/compiler/pass_1.pas
+++ b/compiler/pass_1.pas
@@ -66,6 +66,7 @@ implementation
          oldverbosity     : longint;
          oldpos    : tfileposinfo;
          hp        : tnode;
+         oldflags  : tnodeflags;
       begin
         node_changed:=false;
         if (p.resultdef=nil) then
@@ -83,9 +84,13 @@ implementation
            if assigned(hp) then
             begin
                node_changed:=true;
+               oldflags:=p.flags;
                p.free;
                { switch to new node }
                p:=hp;
+               { transfer generic paramter flag }
+               if nf_generic_para in oldflags then
+                 include(p.flags,nf_generic_para);
                { run typecheckpass }
                typecheckpass(p);
             end;
diff --git a/compiler/pdecl.pas b/compiler/pdecl.pas
index c5b5bcc921..81c71a09a3 100644
--- a/compiler/pdecl.pas
+++ b/compiler/pdecl.pas
@@ -120,14 +120,15 @@ implementation
              end;
            realconstn :
              begin
-                new(pd);
-                pd^:=trealconstnode(p).value_real;
-                hp:=cconstsym.create_ptr(orgname,constreal,pd,p.resultdef);
+               new(pd);
+               pd^:=trealconstnode(p).value_real;
+               hp:=cconstsym.create_ptr(orgname,constreal,pd,p.resultdef);
              end;
            setconstn :
              begin
                new(ps);
-               ps^:=tsetconstnode(p).value_set^;
+               if assigned(tsetconstnode(p).value_set) then
+                 ps^:=tsetconstnode(p).value_set^;
                hp:=cconstsym.create_ptr(orgname,constset,ps,p.resultdef);
              end;
            pointerconstn :
@@ -141,18 +142,18 @@ implementation
            typen :
              begin
                if is_interface(p.resultdef) then
-                begin
-                  if assigned(tobjectdef(p.resultdef).iidguid) then
-                   begin
-                     new(pg);
-                     pg^:=tobjectdef(p.resultdef).iidguid^;
-                     hp:=cconstsym.create_ptr(orgname,constguid,pg,p.resultdef);
-                   end
-                  else
-                   Message1(parser_e_interface_has_no_guid,tobjectdef(p.resultdef).objrealname^);
-                end
-               else
-                Message(parser_e_illegal_expression);
+                 begin
+                   if assigned(tobjectdef(p.resultdef).iidguid) then
+                     begin
+                       new(pg);
+                       pg^:=tobjectdef(p.resultdef).iidguid^;
+                       hp:=cconstsym.create_ptr(orgname,constguid,pg,p.resultdef);
+                     end
+                    else
+                      Message1(parser_e_interface_has_no_guid,tobjectdef(p.resultdef).objrealname^);
+                 end
+               else 
+                 Message(parser_e_illegal_expression);
              end;
            inlinen:
              begin
@@ -177,8 +178,22 @@ implementation
                end;
              end;
            else
-             Message(parser_e_illegal_expression);
+             begin
+               { the node is from a generic parameter constant and is 
+                 untyped so we need to pass a placeholder constant 
+                 instead of givng an error }
+               if nf_generic_para in p.flags then 
+                 hp:=cconstsym.create_ord(orgname,constnil,0,p.resultdef)
+               else
+                 Message(parser_e_illegal_expression);
+             end;
         end;
+        { transfer generic param flag from node to symbol }
+        if nf_generic_para in p.flags then
+          begin
+            include(hp.symoptions,sp_generic_const);
+            include(hp.symoptions,sp_generic_para);
+          end;
         current_tokenpos:=storetokenpos;
         p.free;
         readconstant:=hp;
@@ -507,8 +522,9 @@ implementation
                { we are not freeing the type parameters, so register them }
                for i:=0 to generictypelist.count-1 do
                  begin
-                    ttypesym(generictypelist[i]).register_sym;
-                    tstoreddef(ttypesym(generictypelist[i]).typedef).register_def;
+                    tstoredsym(generictypelist[i]).register_sym;
+                    if tstoredsym(generictypelist[i]).typ=typesym then
+                      tstoreddef(ttypesym(generictypelist[i]).typedef).register_def;
                  end;
 
                str(generictypelist.Count,s);
diff --git a/compiler/pdecvar.pas b/compiler/pdecvar.pas
index 4d39397e46..8121d87853 100644
--- a/compiler/pdecvar.pas
+++ b/compiler/pdecvar.pas
@@ -1675,6 +1675,10 @@ implementation
                    end;
                end;
 
+             { field type is a generic param so set a flag in the struct }
+             if assigned(hdef.typesym) and (sp_generic_para in hdef.typesym.symoptions) then
+               include(current_structdef.defoptions,df_has_generic_fields);
+
              { Process procvar directives }
              if maybe_parse_proc_directives(hdef) then
                semicoloneaten:=true;
diff --git a/compiler/pexpr.pas b/compiler/pexpr.pas
index bc0606ed4b..3c1c527297 100644
--- a/compiler/pexpr.pas
+++ b/compiler/pexpr.pas
@@ -446,6 +446,9 @@ implementation
                   { no packed bit support for these things }
                   if l=in_bitsizeof_x then
                     statement_syssym:=caddnode.create(muln,statement_syssym,cordconstnode.create(8,sinttype,true));
+                  { type sym is a generic parameter }
+                  if assigned(p1.resultdef.typesym) and (sp_generic_para in p1.resultdef.typesym.symoptions) then
+                    include(statement_syssym.flags,nf_generic_para);
                 end
               else
                begin
@@ -466,6 +469,9 @@ implementation
                    end
                  else
                    statement_syssym:=cordconstnode.create(p1.resultdef.packedbitsize,sinttype,true);
+                 { type def is a struct with generic fields }
+                 if df_has_generic_fields in p1.resultdef.defoptions then
+                    include(statement_syssym.flags,nf_generic_para);
                  { p1 not needed !}
                  p1.destroy;
                end;
@@ -4078,7 +4084,10 @@ implementation
                 gendef:=generate_specialization_phase2(spezcontext,tstoreddef(gendef),false,'');
                 spezcontext.free;
                 spezcontext:=nil;
-                gensym:=gendef.typesym;
+                if gendef.typ=errordef then
+                  gensym:=generrorsym
+                else
+                  gensym:=gendef.typesym;
               end;
             procdef:
               begin
@@ -4417,7 +4426,7 @@ implementation
          filepos : tfileposinfo;
          oldafterassignment,
          updatefpos          : boolean;
-
+         oldflags : tnodeflags;
       begin
          oldafterassignment:=afterassignment;
          p1:=sub_expr(opcompare,[ef_accept_equal],nil);
@@ -4474,6 +4483,10 @@ implementation
           else
             updatefpos:=false;
          end;
+         oldflags:=p1.flags;
+         { transfer generic paramter flag }
+         if nf_generic_para in oldflags then
+           include(p1.flags,nf_generic_para);
          { get the resultdef for this expression }
          if not assigned(p1.resultdef) and
             dotypecheck then
diff --git a/compiler/pgentype.pas b/compiler/pgentype.pas
index b2847c78f6..85270df256 100644
--- a/compiler/pgentype.pas
+++ b/compiler/pgentype.pas
@@ -28,7 +28,7 @@ interface
 uses
   cclasses,
   globtype,
-  symtype,symbase;
+  symconst,symtype,symbase;
 
 const
   inline_specialization_block_types = [bt_type,bt_var_type,bt_const_type,bt_body];
@@ -42,7 +42,7 @@ type
 
   tspecializationcontext=class
   public
-    genericdeflist : tfpobjectlist;
+    paramlist : tfpobjectlist;
     poslist : tfplist;
     prettyname : ansistring;
     specializename : ansistring;
@@ -58,7 +58,7 @@ implementation
 
 constructor tspecializationcontext.create;
 begin
-  genericdeflist:=tfpobjectlist.create(false);
+  paramlist:=tfpobjectlist.create(false);
   poslist:=tfplist.create;
 end;
 
@@ -66,7 +66,7 @@ destructor tspecializationcontext.destroy;
 var
   i : longint;
 begin
-  genericdeflist.free;
+  paramlist.free;
   for i:=0 to poslist.count-1 do
     dispose(pfileposinfo(poslist[i]));
   poslist.free;
diff --git a/compiler/pgenutil.pas b/compiler/pgenutil.pas
index 7760a4e134..5addd281fd 100644
--- a/compiler/pgenutil.pas
+++ b/compiler/pgenutil.pas
@@ -42,9 +42,9 @@ uses
     function generate_specialization_phase1(out context:tspecializationcontext;genericdef:tdef;symname:string):tdef;inline;
     function generate_specialization_phase1(out context:tspecializationcontext;genericdef:tdef;parsedtype:tdef;symname:string;parsedpos:tfileposinfo):tdef;
     function generate_specialization_phase2(context:tspecializationcontext;genericdef:tstoreddef;parse_class_parent:boolean;_prettyname:ansistring):tdef;
-    function check_generic_constraints(genericdef:tstoreddef;paradeflist:tfpobjectlist;poslist:tfplist):boolean;
+    function check_generic_constraints(genericdef:tstoreddef;paramlist:tfpobjectlist;poslist:tfplist):boolean;
     function parse_generic_parameters(allowconstraints:boolean):tfphashobjectlist;
-    function parse_generic_specialization_types(genericdeflist:tfpobjectlist;poslist:tfplist;out prettyname,specializename:ansistring):boolean;
+    function parse_generic_specialization_types(paramlist:tfpobjectlist;poslist:tfplist;out prettyname,specializename:ansistring):boolean;
     procedure insert_generic_parameter_types(def:tstoreddef;genericdef:tstoreddef;genericlist:tfphashobjectlist);
     procedure maybe_insert_generic_rename_symbol(const name:tidstring;genericlist:tfphashobjectlist);
     function generate_generic_name(const name:tidstring;specializename:ansistring;owner_hierarchy:string):tidstring;
@@ -63,18 +63,164 @@ implementation
 
 uses
   { common }
-  cutils,fpccrc,
+  sysutils,cutils,fpccrc,
   { global }
-  globals,tokens,verbose,finput,
+  globals,tokens,verbose,finput,constexp,
   { symtable }
-  symconst,symsym,symtable,defcmp,procinfo,
+  symconst,symsym,symtable,defcmp,defutil,procinfo,
   { modules }
   fmodule,
-  node,nobj,
+  node,nobj,ncon,
   { parser }
   scanner,
   pbase,pexpr,pdecsub,ptype,psub;
 
+  type
+    tdeftypeset = set of tdeftyp;
+  const
+    tgeneric_param_const_types : tdeftypeset = [orddef,stringdef,arraydef,floatdef,setdef,pointerdef,undefineddef];
+    tgeneric_param_nodes : tnodetypeset = [typen,ordconstn,stringconstn,realconstn,setconstn,niln];
+
+    function get_generic_param_def(sym:tsym):tdef;
+      begin
+        if sym.typ=constsym then
+          result:=tconstsym(sym).constdef
+        else
+          result:=ttypesym(sym).typedef;
+      end;
+
+    function is_generic_param_const(sym:tsym):boolean;
+      begin
+        if sym.typ=constsym then
+          result:=tconstsym(sym).consttyp<>constundefined
+        else
+          result:=false;
+      end;
+
+    function compare_orddef_by_range(param1,param2:torddef;value:tconstvalue):boolean;
+      begin
+        if (value.len<param2.low) or (value.len>param2.high) then
+          result:=false
+        else
+          result:=true;
+      end;
+
+    function compare_generic_params(param1,param2:tdef;constparamsym:tconstsym):boolean;
+      begin
+        if (param1.typ=orddef) and (param2.typ=orddef) then
+          begin
+            if is_boolean(param2) then
+              result:=is_boolean(param1)
+            else if is_char(param2) then
+              result:=is_char(param1)
+            else if compare_orddef_by_range(torddef(param1),torddef(param2),constparamsym.value) then
+              result:=true
+            else
+              result:=false;
+          end
+        { arraydef is string constant so it's compatible with stringdef }
+        else if (param1.typ=arraydef) and (param2.typ=stringdef) then
+          result:=true
+        { integer ords are compatible with float }
+        else if (param1.typ=orddef) and is_integer(param1) and (param2.typ=floatdef) then
+          result:=true
+        { undefined def is compatible with all types }
+        else if param2.typ=undefineddef then
+          result:=true
+        { sets require stricter checks }
+        else if is_set(param2) then
+          result:=equal_defs(param1,param2)
+        else
+          result:=param1.typ=param2.typ;
+      end;
+
+    function create_generic_constsym(fromdef:tdef;node:tnode;out prettyname:string):tconstsym;
+      const
+        undefinedname = 'undefined';
+      var
+        sym : tconstsym;
+        setdef : tsetdef;
+        enumsym : tsym;
+        enumname : string;
+        sp : pchar;
+        ps : ^tconstset;
+        pd : ^bestreal;
+        i : integer;
+      begin
+        if node=nil then
+          begin
+            sym:=cconstsym.create_undefined(undefinedname,fromdef);
+            sym.owner:=fromdef.owner;
+            prettyname:='';
+            result:=sym;
+            exit;
+          end;
+        case node.nodetype of
+          ordconstn:
+            begin
+              sym:=cconstsym.create_ord(undefinedname,constord,tordconstnode(node).value,fromdef);
+              prettyname:=inttostr(tordconstnode(node).value.svalue);
+            end;
+          stringconstn:
+            begin
+              getmem(sp,tstringconstnode(node).len+1);
+              move(tstringconstnode(node).value_str^,sp^,tstringconstnode(node).len+1);
+              sym:=cconstsym.create_string(undefinedname,conststring,sp,tstringconstnode(node).len,fromdef);
+              prettyname:=''''+tstringconstnode(node).value_str+'''';
+            end;
+          realconstn:
+            begin
+              new(pd);
+              pd^:=trealconstnode(node).value_real;
+              sym:=cconstsym.create_ptr(undefinedname,constreal,pd,fromdef);
+              prettyname:=floattostr(trealconstnode(node).value_real);
+            end;
+          setconstn:
+            begin
+              new(ps);
+              ps^:=tsetconstnode(node).value_set^;
+              sym:=cconstsym.create_ptr(undefinedname,constset,ps,fromdef);
+              setdef:=tsetdef(tsetconstnode(node).resultdef);
+              prettyname:='[';
+              for i := setdef.setbase to setdef.setmax do
+                if i in tsetconstnode(node).value_set^ then
+                  begin
+                    if setdef.elementdef.typ=enumdef then
+                      enumsym:=tenumdef(setdef.elementdef).int2enumsym(i)
+                    else
+                      enumsym:=nil;
+                    if assigned(enumsym) then
+                      enumname:=enumsym.realname
+                    else if setdef.elementdef.typ=orddef then
+                      begin
+                        if torddef(setdef.elementdef).ordtype=uchar then
+                          enumname:=chr(i)
+                        else
+                          enumname:=tostr(i);
+                      end
+                    else
+                      enumname:=tostr(i);
+                    if length(prettyname) > 1 then
+                      prettyname:=prettyname+','+enumname
+                    else
+                      prettyname:=prettyname+enumname;
+                  end;
+              prettyname:=prettyname+']';
+            end;
+          niln:
+            begin
+              { only "nil" is available for pointer constants }
+              sym:=cconstsym.create_ord(undefinedname,constnil,0,fromdef);
+              prettyname:='nil';
+            end;
+          else
+            internalerror(2019021601);
+        end;
+        { the sym needs an owner for later checks so us the typeparam owner }
+        sym.owner:=fromdef.owner;
+        include(sym.symoptions,sp_generic_const);
+        result:=sym;
+      end;
 
     procedure maybe_add_waiting_unit(tt:tdef);
       var
@@ -104,203 +250,232 @@ uses
           end;
       end;
 
-    function check_generic_constraints(genericdef:tstoreddef;paradeflist:tfpobjectlist;poslist:tfplist):boolean;
+    function check_generic_constraints(genericdef:tstoreddef;paramlist:tfpobjectlist;poslist:tfplist):boolean;
       var
         i,j,
         intfcount : longint;
         formaldef,
         paradef : tstoreddef;
+        genparadef : tdef;
         objdef,
         paraobjdef,
         formalobjdef : tobjectdef;
         intffound : boolean;
         filepos : tfileposinfo;
+        //paratype : tconsttyp;
+        is_const : boolean;
       begin
         { check whether the given specialization parameters fit to the eventual
           constraints of the generic }
         if not assigned(genericdef.genericparas) or (genericdef.genericparas.count=0) then
           internalerror(2012101001);
-        if genericdef.genericparas.count<>paradeflist.count then
+        if genericdef.genericparas.count<>paramlist.count then
           internalerror(2012101002);
-        if paradeflist.count<>poslist.count then
+        if paramlist.count<>poslist.count then
           internalerror(2012120801);
         result:=true;
         for i:=0 to genericdef.genericparas.count-1 do
           begin
             filepos:=pfileposinfo(poslist[i])^;
-            formaldef:=tstoreddef(ttypesym(genericdef.genericparas[i]).typedef);
-            if formaldef.typ=undefineddef then
-              { the parameter is of unspecified type, so no need to check }
-              continue;
-            if not (df_genconstraint in formaldef.defoptions) or
-                not assigned(formaldef.genconstraintdata) then
-              internalerror(2013021602);
-            paradef:=tstoreddef(paradeflist[i]);
-            { undefineddef is compatible with anything }
-            if formaldef.typ=undefineddef then
-              continue;
-            if paradef.typ<>formaldef.typ then
+            paradef:=tstoreddef(get_generic_param_def(tsym(paramlist[i])));
+            is_const:=is_generic_param_const(tsym(paramlist[i]));
+            genparadef:=genericdef.get_generic_param_def(i);
+            { validate const params }
+            if not genericdef.is_generic_param_const(i) and is_const then
               begin
-                case formaldef.typ of
-                  recorddef:
-                    { delphi has own fantasy about record constraint
-                      (almost non-nullable/non-nilable value type) }
-                    if m_delphi in current_settings.modeswitches then
-                      case paradef.typ of
-                        floatdef,enumdef,orddef:
-                          continue;
-                        objectdef:
-                          if tobjectdef(paradef).objecttype=odt_object then
-                            continue
-                          else
-                            MessagePos(filepos,type_e_record_type_expected);
+                MessagePos(filepos,type_e_mismatch);
+                exit(false);
+              end
+            else if genericdef.is_generic_param_const(i) then
+              begin
+                { param type mismatch (type <> const) }
+                 if genericdef.is_generic_param_const(i) <> is_const then
+                   begin
+                    MessagePos(filepos,type_e_mismatch);
+                    exit(false);
+                  end;
+                { type constrained param doesn't match type }
+                if not compare_generic_params(paradef,genericdef.get_generic_param_def(i),tconstsym(paramlist[i])) then
+                  begin
+                    MessagePos2(filepos,type_e_incompatible_types,FullTypeName(paradef,genparadef),FullTypeName(genparadef,paradef));
+                    exit(false);
+                  end;
+              end;
+            { test constraints for non-const params }
+            if not genericdef.is_generic_param_const(i) then
+              begin
+                formaldef:=tstoreddef(ttypesym(genericdef.genericparas[i]).typedef);
+                if formaldef.typ=undefineddef then
+                  { the parameter is of unspecified type, so no need to check }
+                  continue;
+                if not (df_genconstraint in formaldef.defoptions) or
+                    not assigned(formaldef.genconstraintdata) then
+                  internalerror(2013021602);
+                { undefineddef is compatible with anything }
+                if formaldef.typ=undefineddef then
+                  continue;
+                if paradef.typ<>formaldef.typ then
+                  begin
+                    case formaldef.typ of
+                      recorddef:
+                        { delphi has own fantasy about record constraint
+                          (almost non-nullable/non-nilable value type) }
+                        if m_delphi in current_settings.modeswitches then
+                          case paradef.typ of
+                            floatdef,enumdef,orddef:
+                              continue;
+                            objectdef:
+                              if tobjectdef(paradef).objecttype=odt_object then
+                                continue
+                              else
+                                MessagePos(filepos,type_e_record_type_expected);
+                            else
+                              MessagePos(filepos,type_e_record_type_expected);
+                          end
                         else
                           MessagePos(filepos,type_e_record_type_expected);
-                      end
-                    else
-                      MessagePos(filepos,type_e_record_type_expected);
-                  objectdef:
-                    case tobjectdef(formaldef).objecttype of
-                      odt_class,
-                      odt_javaclass:
-                        MessagePos1(filepos,type_e_class_type_expected,paradef.typename);
-                      odt_interfacecom,
-                      odt_interfacecorba,
-                      odt_dispinterface,
-                      odt_interfacejava:
-                        MessagePos1(filepos,type_e_interface_type_expected,paradef.typename);
+                      objectdef:
+                        case tobjectdef(formaldef).objecttype of
+                          odt_class,
+                          odt_javaclass:
+                            MessagePos1(filepos,type_e_class_type_expected,paradef.typename);
+                          odt_interfacecom,
+                          odt_interfacecorba,
+                          odt_dispinterface,
+                          odt_interfacejava:
+                            MessagePos1(filepos,type_e_interface_type_expected,paradef.typename);
+                          else
+                            internalerror(2012101003);
+                        end;
+                      errordef:
+                        { ignore }
+                        ;
                       else
-                        internalerror(2012101003);
+                        internalerror(2012101004);
                     end;
-                  errordef:
-                    { ignore }
-                    ;
-                  else
-                    internalerror(2012101004);
-                end;
-                result:=false;
-              end
-            else
-              begin
-                { the paradef types are the same, so do special checks for the
-                  cases in which they are needed }
-                if formaldef.typ=objectdef then
+                    result:=false;
+                  end
+                else
                   begin
-                    paraobjdef:=tobjectdef(paradef);
-                    formalobjdef:=tobjectdef(formaldef);
-                    if not (formalobjdef.objecttype in [odt_class,odt_javaclass,odt_interfacecom,odt_interfacecorba,odt_interfacejava,odt_dispinterface]) then
-                      internalerror(2012101102);
-                    if formalobjdef.objecttype in [odt_interfacecom,odt_interfacecorba,odt_interfacejava,odt_dispinterface] then
+                    { the paradef types are the same, so do special checks for the
+                      cases in which they are needed }
+                    if formaldef.typ=objectdef then
                       begin
-                        { this is either a concerete interface or class type (the
-                          latter without specific implemented interfaces) }
-                        case paraobjdef.objecttype of
-                          odt_interfacecom,
-                          odt_interfacecorba,
-                          odt_interfacejava,
-                          odt_dispinterface:
-                            begin
-                              if (oo_is_forward in paraobjdef.objectoptions) and
-                                  (paraobjdef.objecttype=formalobjdef.objecttype) and
-                                  (df_genconstraint in formalobjdef.defoptions) and
-                                  (
-                                    (formalobjdef.objecttype=odt_interfacecom) and
-                                    (formalobjdef.childof=interface_iunknown)
-                                  )
-                                  or
-                                  (
-                                    (formalobjdef.objecttype=odt_interfacecorba) and
-                                    (formalobjdef.childof=nil)
-                                  ) then
-                                continue;
-                              if not def_is_related(paraobjdef,formalobjdef.childof) then
+                        paraobjdef:=tobjectdef(paradef);
+                        formalobjdef:=tobjectdef(formaldef);
+                        if not (formalobjdef.objecttype in [odt_class,odt_javaclass,odt_interfacecom,odt_interfacecorba,odt_interfacejava,odt_dispinterface]) then
+                          internalerror(2012101102);
+                        if formalobjdef.objecttype in [odt_interfacecom,odt_interfacecorba,odt_interfacejava,odt_dispinterface] then
+                          begin
+                            { this is either a concerete interface or class type (the
+                              latter without specific implemented interfaces) }
+                            case paraobjdef.objecttype of
+                              odt_interfacecom,
+                              odt_interfacecorba,
+                              odt_interfacejava,
+                              odt_dispinterface:
                                 begin
-                                  MessagePos2(filepos,type_e_incompatible_types,paraobjdef.typename,formalobjdef.childof.typename);
-                                  result:=false;
+                                  if (oo_is_forward in paraobjdef.objectoptions) and
+                                      (paraobjdef.objecttype=formalobjdef.objecttype) and
+                                      (df_genconstraint in formalobjdef.defoptions) and
+                                      (
+                                        (formalobjdef.objecttype=odt_interfacecom) and
+                                        (formalobjdef.childof=interface_iunknown)
+                                      )
+                                      or
+                                      (
+                                        (formalobjdef.objecttype=odt_interfacecorba) and
+                                        (formalobjdef.childof=nil)
+                                      ) then
+                                    continue;
+                                  if not def_is_related(paraobjdef,formalobjdef.childof) then
+                                    begin
+                                      MessagePos2(filepos,type_e_incompatible_types,paraobjdef.typename,formalobjdef.childof.typename);
+                                      result:=false;
+                                    end;
                                 end;
-                            end;
-                          odt_class,
-                          odt_javaclass:
-                            begin
-                              objdef:=paraobjdef;
-                              intffound:=false;
-                              while assigned(objdef) do
+                              odt_class,
+                              odt_javaclass:
                                 begin
-                                  for j:=0 to objdef.implementedinterfaces.count-1 do
-                                    if timplementedinterface(objdef.implementedinterfaces[j]).intfdef=formalobjdef.childof then
-                                      begin
-                                        intffound:=true;
+                                  objdef:=paraobjdef;
+                                  intffound:=false;
+                                  while assigned(objdef) do
+                                    begin
+                                      for j:=0 to objdef.implementedinterfaces.count-1 do
+                                        if timplementedinterface(objdef.implementedinterfaces[j]).intfdef=formalobjdef.childof then
+                                          begin
+                                            intffound:=true;
+                                            break;
+                                          end;
+                                      if intffound then
                                         break;
-                                      end;
-                                  if intffound then
-                                    break;
-                                  objdef:=objdef.childof;
+                                      objdef:=objdef.childof;
+                                    end;
+                                  result:=intffound;
+                                  if not result then
+                                    MessagePos2(filepos,parser_e_class_doesnt_implement_interface,paraobjdef.typename,formalobjdef.childof.typename);
+                                end;
+                              else
+                                begin
+                                  MessagePos1(filepos,type_e_class_or_interface_type_expected,paraobjdef.typename);
+                                  result:=false;
                                 end;
-                              result:=intffound;
-                              if not result then
-                                MessagePos2(filepos,parser_e_class_doesnt_implement_interface,paraobjdef.typename,formalobjdef.childof.typename);
-                            end;
-                          else
-                            begin
-                              MessagePos1(filepos,type_e_class_or_interface_type_expected,paraobjdef.typename);
-                              result:=false;
                             end;
-                        end;
-                      end
-                    else
-                      begin
-                        { this is either a "class" or a concrete instance with
-                          or without implemented interfaces }
-                        if not (paraobjdef.objecttype in [odt_class,odt_javaclass]) then
-                          begin
-                            MessagePos1(filepos,type_e_class_type_expected,paraobjdef.typename);
-                            result:=false;
-                            continue;
-                          end;
-                        { for forward declared classes we allow pure TObject/class declarations }
-                        if (oo_is_forward in paraobjdef.objectoptions) and
-                            (df_genconstraint in formaldef.defoptions) then
-                          begin
-                            if (formalobjdef.childof=class_tobject) and
-                                not formalobjdef.implements_any_interfaces then
-                              continue;
-                          end;
-                        if assigned(formalobjdef.childof) and
-                            not def_is_related(paradef,formalobjdef.childof) then
-                          begin
-                            MessagePos2(filepos,type_e_incompatible_types,paraobjdef.typename,formalobjdef.childof.typename);
-                            result:=false;
-                          end;
-                        intfcount:=0;
-                        for j:=0 to formalobjdef.implementedinterfaces.count-1 do
+                          end
+                        else
                           begin
-                            objdef:=paraobjdef;
-                            while assigned(objdef) do
+                            { this is either a "class" or a concrete instance with
+                              or without implemented interfaces }
+                            if not (paraobjdef.objecttype in [odt_class,odt_javaclass]) then
                               begin
-                                intffound:=assigned(
-                                             find_implemented_interface(objdef,
-                                               timplementedinterface(formalobjdef.implementedinterfaces[j]).intfdef
-                                             )
-                                           );
+                                MessagePos1(filepos,type_e_class_type_expected,paraobjdef.typename);
+                                result:=false;
+                                continue;
+                              end;
+                            { for forward declared classes we allow pure TObject/class declarations }
+                            if (oo_is_forward in paraobjdef.objectoptions) and
+                                (df_genconstraint in formaldef.defoptions) then
+                              begin
+                                if (formalobjdef.childof=class_tobject) and
+                                    not formalobjdef.implements_any_interfaces then
+                                  continue;
+                              end;
+                            if assigned(formalobjdef.childof) and
+                                not def_is_related(paradef,formalobjdef.childof) then
+                              begin
+                                MessagePos2(filepos,type_e_incompatible_types,paraobjdef.typename,formalobjdef.childof.typename);
+                                result:=false;
+                              end;
+                            intfcount:=0;
+                            for j:=0 to formalobjdef.implementedinterfaces.count-1 do
+                              begin
+                                objdef:=paraobjdef;
+                                while assigned(objdef) do
+                                  begin
+                                    intffound:=assigned(
+                                                 find_implemented_interface(objdef,
+                                                   timplementedinterface(formalobjdef.implementedinterfaces[j]).intfdef
+                                                 )
+                                               );
+                                    if intffound then
+                                      break;
+                                    objdef:=objdef.childof;
+                                  end;
                                 if intffound then
-                                  break;
-                                objdef:=objdef.childof;
+                                  inc(intfcount)
+                                else
+                                  MessagePos2(filepos,parser_e_class_doesnt_implement_interface,paraobjdef.typename,timplementedinterface(formalobjdef.implementedinterfaces[j]).intfdef.typename);
                               end;
-                            if intffound then
-                              inc(intfcount)
-                            else
-                              MessagePos2(filepos,parser_e_class_doesnt_implement_interface,paraobjdef.typename,timplementedinterface(formalobjdef.implementedinterfaces[j]).intfdef.typename);
+                            if intfcount<>formalobjdef.implementedinterfaces.count then
+                              result:=false;
                           end;
-                        if intfcount<>formalobjdef.implementedinterfaces.count then
-                          result:=false;
                       end;
                   end;
               end;
           end;
       end;
 
-
-    function parse_generic_specialization_types_internal(genericdeflist:tfpobjectlist;poslist:tfplist;out prettyname,specializename:ansistring;parsedtype:tdef;parsedpos:tfileposinfo):boolean;
+    function parse_generic_specialization_types_internal(paramlist:tfpobjectlist;poslist:tfplist;out prettyname,specializename:ansistring;parsedtype:tdef;parsedpos:tfileposinfo):boolean;
       var
         old_block_type : tblock_type;
         first : boolean;
@@ -310,9 +485,12 @@ uses
         namepart : string;
         prettynamepart : ansistring;
         module : tmodule;
+        //paramdef : tgenericparamdef;
+        constprettyname : string;
+        validparam : boolean;
       begin
         result:=true;
-        if genericdeflist=nil then
+        if paramlist=nil then
           internalerror(2012061401);
         { set the block type to type, so that the parsed type are returned as
           ttypenode (e.g. classes are in non type-compatible blocks returned as
@@ -324,7 +502,7 @@ uses
         first:=not assigned(parsedtype);
         if assigned(parsedtype) then
           begin
-            genericdeflist.Add(parsedtype);
+            paramlist.Add(parsedtype.typesym);
             module:=find_module_from_symtable(parsedtype.owner);
             if not assigned(module) then
               internalerror(2016112801);
@@ -350,8 +528,10 @@ uses
               consume(_COMMA);
             block_type:=bt_type;
             tmpparampos:=current_filepos;
-            typeparam:=factor(false,[ef_type_only]);
-            if typeparam.nodetype=typen then
+            typeparam:=factor(false,[ef_accept_equal]);
+            { determine if the typeparam node is a valid type or const }
+            validparam:=typeparam.nodetype in tgeneric_param_nodes;
+            if validparam then
               begin
                 if tstoreddef(typeparam.resultdef).is_generic and
                     (
@@ -367,31 +547,47 @@ uses
                   end;
                 if typeparam.resultdef.typ<>errordef then
                   begin
-                    if not assigned(typeparam.resultdef.typesym) then
+                    if (typeparam.nodetype = typen) and not assigned(typeparam.resultdef.typesym) then
                       message(type_e_generics_cannot_reference_itself)
-                    else if (typeparam.resultdef.typ<>errordef) then
+                    else 
+                    if (typeparam.resultdef.typ<>errordef) then
                       begin
-                        genericdeflist.Add(typeparam.resultdef);
+                        { all non-type nodes are considered const }
+                        if typeparam.nodetype<>typen then
+                          paramlist.Add(create_generic_constsym(typeparam.resultdef,typeparam,constprettyname))
+                        else
+                          begin
+                            constprettyname:='';
+                            paramlist.Add(typeparam.resultdef.typesym);
+                          end;
                         module:=find_module_from_symtable(typeparam.resultdef.owner);
                         if not assigned(module) then
                           internalerror(2016112802);
                         namepart:='_$'+hexstr(module.moduleid,8)+'$$'+typeparam.resultdef.unique_id_str;
+                        if constprettyname <> '' then
+                          namepart:=namepart+'$$'+constprettyname;
                         { we use the full name of the type to uniquely identify it }
-                        if (symtablestack.top.symtabletype=parasymtable) and
-                            (symtablestack.top.defowner.typ=procdef) and
-                            (typeparam.resultdef.owner=symtablestack.top) then
-                          begin
-                            { special handling for specializations inside generic function declarations }
-                            prettynamepart:=tdef(symtablestack.top.defowner).fullownerhierarchyname(true)+tprocdef(symtablestack.top.defowner).procsym.prettyname;
-                          end
-                        else
+                        if typeparam.nodetype = typen then
                           begin
-                            prettynamepart:=typeparam.resultdef.fullownerhierarchyname(true);
+                            if (symtablestack.top.symtabletype=parasymtable) and
+                                (symtablestack.top.defowner.typ=procdef) and
+                                (typeparam.resultdef.owner=symtablestack.top) then
+                              begin
+                                { special handling for specializations inside generic function declarations }
+                                prettynamepart:=tdef(symtablestack.top.defowner).fullownerhierarchyname(true)+tprocdef(symtablestack.top.defowner).procsym.prettyname;
+                              end
+                            else
+                              begin
+                                prettynamepart:=typeparam.resultdef.fullownerhierarchyname(true);
+                              end;
                           end;
                         specializename:=specializename+namepart;
                         if not first then
                           prettyname:=prettyname+',';
-                        prettyname:=prettyname+prettynamepart+typeparam.resultdef.typesym.prettyname;
+                        if constprettyname <> '' then
+                          prettyname:=prettyname+constprettyname
+                        else
+                          prettyname:=prettyname+prettynamepart+typeparam.resultdef.typesym.prettyname;
                       end;
                   end
                 else
@@ -411,12 +607,12 @@ uses
       end;
 
 
-    function parse_generic_specialization_types(genericdeflist:tfpobjectlist;poslist:tfplist;out prettyname,specializename:ansistring):boolean;
+    function parse_generic_specialization_types(paramlist:tfpobjectlist;poslist:tfplist;out prettyname,specializename:ansistring):boolean;
       var
         dummypos : tfileposinfo;
       begin
         FillChar(dummypos, SizeOf(tfileposinfo), 0);
-        result:=parse_generic_specialization_types_internal(genericdeflist,poslist,prettyname,specializename,nil,dummypos);
+        result:=parse_generic_specialization_types_internal(paramlist,poslist,prettyname,specializename,nil,dummypos);
       end;
 
 
@@ -578,7 +774,7 @@ uses
         context:=tspecializationcontext.create;
 
         { Parse type parameters }
-        err:=not parse_generic_specialization_types_internal(context.genericdeflist,context.poslist,context.prettyname,context.specializename,parsedtype,parsedpos);
+        err:=not parse_generic_specialization_types_internal(context.paramlist,context.poslist,context.prettyname,context.specializename,parsedtype,parsedpos);
         if err then
           begin
             if not try_to_consume(_GT) then
@@ -627,7 +823,7 @@ uses
 
         { search a generic with the given count of params }
         countstr:='';
-        str(context.genericdeflist.Count,countstr);
+        str(context.paramlist.Count,countstr);
 
         genname:=genname+'$'+countstr;
         ugenname:=upper(genname);
@@ -656,7 +852,7 @@ uses
             result:=generrordef;
             exit;
           end;
-
+        
         { we've found the correct def }
         if context.sym.typ=typesym then
           result:=tstoreddef(ttypesym(context.sym).typedef)
@@ -747,6 +943,7 @@ uses
         hintsprocessed : boolean;
         pd : tprocdef;
         pdflags : tpdflags;
+        typedef : tstoreddef;
       begin
         if not assigned(context) then
           internalerror(2015052203);
@@ -755,7 +952,7 @@ uses
 
         pd:=nil;
 
-        if not check_generic_constraints(genericdef,context.genericdeflist,context.poslist) then
+        if not check_generic_constraints(genericdef,context.paramlist,context.poslist) then
           begin
             { the parameters didn't fit the constraints, so don't continue with the
               specialization }
@@ -771,20 +968,19 @@ uses
         else
           prettyname:=genericdef.typesym.prettyname;
         prettyname:=prettyname+'<'+context.prettyname+'>';
-
         generictypelist:=tfphashobjectlist.create(false);
 
         { build the list containing the types for the generic params }
         if not assigned(genericdef.genericparas) then
           internalerror(2013092601);
-        if context.genericdeflist.count<>genericdef.genericparas.count then
+        if context.paramlist.count<>genericdef.genericparas.count then
           internalerror(2013092603);
         for i:=0 to genericdef.genericparas.Count-1 do
           begin
             srsym:=tsym(genericdef.genericparas[i]);
             if not (sp_generic_para in srsym.symoptions) then
               internalerror(2013092602);
-            generictypelist.add(srsym.realname,tdef(context.genericdeflist[i]).typesym);
+            generictypelist.add(srsym.realname,context.paramlist[i]);
           end;
 
         { Special case if we are referencing the current defined object }
@@ -1196,8 +1392,8 @@ uses
 
     function parse_generic_parameters(allowconstraints:boolean):tfphashobjectlist;
       var
-        generictype : ttypesym;
-        i,firstidx : longint;
+        generictype : tstoredsym;
+        i,firstidx,const_list_index : longint;
         srsymtable : tsymtable;
         basedef,def : tdef;
         defname : tidstring;
@@ -1205,22 +1401,87 @@ uses
         doconsume : boolean;
         constraintdata : tgenericconstraintdata;
         old_block_type : tblock_type;
+        is_const,last_is_const : boolean;
+        last_token : ttoken;
+        last_type_pos : tfileposinfo;
       begin
         result:=tfphashobjectlist.create(false);
         firstidx:=0;
+        const_list_index:=0;
         old_block_type:=block_type;
         block_type:=bt_type;
+        is_const:=false;
+        last_is_const:=false;
+        last_token:=NOTOKEN;
         repeat
+          if try_to_consume(_CONST) then
+            begin
+              { last param was const without semicolon terminator }
+              if (result.count>0) and last_is_const and (last_token<>_SEMICOLON) then
+                MessagePos2(last_type_pos,scan_f_syn_expected,arraytokeninfo[_SEMICOLON].str,arraytokeninfo[last_token].str);
+              is_const:=true;
+              const_list_index:=result.count;
+            end;
           if token=_ID then
             begin
-              generictype:=ctypesym.create(orgpattern,cundefinedtype,false);
+              if is_const then
+                begin
+                  { last param was type without semicolon terminator }
+                  if (result.count>0) and not last_is_const and (last_token<>_SEMICOLON) then
+                    MessagePos2(last_type_pos,scan_f_syn_expected,arraytokeninfo[_SEMICOLON].str,arraytokeninfo[last_token].str);
+                  generictype:=tconstsym.create_undefined(orgpattern,cundefinedtype);
+                end
+              else
+                begin
+                  { last param was const without semicolon terminator }
+                  if (result.count>0) and last_is_const and (last_token<>_SEMICOLON) then
+                    MessagePos2(last_type_pos,scan_f_syn_expected,arraytokeninfo[_SEMICOLON].str,arraytokeninfo[last_token].str);
+                  generictype:=ttypesym.create(orgpattern,cundefinedtype,false);
+                end;
               { type parameters need to be added as strict private }
               generictype.visibility:=vis_strictprivate;
               include(generictype.symoptions,sp_generic_para);
               result.add(orgpattern,generictype);
+              last_is_const:=is_const;
             end;
           consume(_ID);
-          if try_to_consume(_COLON) then
+          { const restriction }
+          if is_const then
+            begin
+              if try_to_consume(_COLON) then
+                begin
+                  def := nil;
+                  { parse the type and assign the const type to generictype  }
+                  single_type(def,[]);
+                  for i:=const_list_index to result.count-1 do
+                    begin
+                      { finalize constant information once type is known }
+                      if assigned(def) and (def.typ in tgeneric_param_const_types) then
+                        begin
+                          case def.typ of
+                            orddef:
+                              tconstsym(result[i]).consttyp:=constord;
+                            stringdef:
+                              tconstsym(result[i]).consttyp:=conststring;
+                            floatdef:
+                              tconstsym(result[i]).consttyp:=constreal;
+                            setdef:
+                              tconstsym(result[i]).consttyp:=constset;
+                            { pointer always refers to nil with constants }
+                            pointerdef:
+                              tconstsym(result[i]).consttyp:=constnil;
+                          end;
+                          tconstsym(result[i]).constdef:=def;
+                        end
+                      else
+                        Message(type_e_mismatch);
+                    end;
+                  { after type restriction const list terminates }
+                  is_const:=false;
+                end;
+            end
+          { type restriction }
+          else if try_to_consume(_COLON) then
             begin
               if not allowconstraints then
                 { TODO }
@@ -1335,6 +1596,7 @@ uses
                     basedef:=cobjectdef.create(tobjectdef(def).objecttype,defname,tobjectdef(def),false);
                     constraintdata.interfaces.delete(0);
                   end;
+
               if basedef.typ<>errordef then
                 with tstoreddef(basedef) do
                   begin
@@ -1360,21 +1622,27 @@ uses
                 begin
                   { two different typeless parameters are considered as incompatible }
                   for i:=firstidx to result.count-1 do
-                    begin
-                      ttypesym(result[i]).typedef:=cundefineddef.create(false);
-                      ttypesym(result[i]).typedef.typesym:=ttypesym(result[i]);
-                    end;
+                    if tsym(result[i]).typ<>constsym then
+                      begin
+                        ttypesym(result[i]).typedef:=cundefineddef.create(false);
+                        ttypesym(result[i]).typedef.typesym:=ttypesym(result[i]);
+                      end;
                   { a semicolon terminates a type parameter group }
                   firstidx:=result.count;
                 end;
             end;
+          if token = _SEMICOLON then
+            is_const:=false;
+          last_token:=token;
+          last_type_pos:=current_filepos;
         until not (try_to_consume(_COMMA) or try_to_consume(_SEMICOLON));
         { two different typeless parameters are considered as incompatible }
         for i:=firstidx to result.count-1 do
-          begin
-            ttypesym(result[i]).typedef:=cundefineddef.create(false);
-            ttypesym(result[i]).typedef.typesym:=ttypesym(result[i]);
-          end;
+          if tsym(result[i]).typ<>constsym then
+            begin
+              ttypesym(result[i]).typedef:=cundefineddef.create(false);
+              ttypesym(result[i]).typedef.typesym:=ttypesym(result[i]);
+            end;
         block_type:=old_block_type;
       end;
 
@@ -1382,7 +1650,9 @@ uses
     procedure insert_generic_parameter_types(def:tstoreddef;genericdef:tstoreddef;genericlist:tfphashobjectlist);
       var
         i : longint;
-        generictype,sym : ttypesym;
+        generictype : tstoredsym;
+        generictypedef : tdef;
+        sym : tsym;
         st : tsymtable;
       begin
         def.genericdef:=genericdef;
@@ -1407,10 +1677,23 @@ uses
           def.genericparas:=tfphashobjectlist.create(false);
         for i:=0 to genericlist.count-1 do
           begin
-            generictype:=ttypesym(genericlist[i]);
+            generictype:=tstoredsym(genericlist[i]);
             if assigned(generictype.owner) then
               begin
-                sym:=ctypesym.create(genericlist.nameofindex(i),generictype.typedef,true);
+                if generictype.typ=typesym then
+                  sym:=ctypesym.create(genericlist.nameofindex(i),ttypesym(generictype).typedef,true)
+                else if generictype.typ=constsym then
+                  { generictype is a constsym that was created in create_generic_constsym 
+                    during phase 1 so we pass this directly without copying }
+                  begin
+                    sym:=generictype;
+                    { the sym name is still undefined so we set it to match
+                      the generic param name so it's accessible }
+                    sym.realname:=genericlist.nameofindex(i);
+                    include(sym.symoptions,sp_generic_const);
+                  end
+                else
+                  internalerror(2019021602);
                 { type parameters need to be added as strict private }
                 sym.visibility:=vis_strictprivate;
                 st.insert(sym);
@@ -1418,13 +1701,17 @@ uses
               end
             else
               begin
-                if (generictype.typedef.typ=undefineddef) and (generictype.typedef<>cundefinedtype) then
+                if generictype.typ=typesym then
                   begin
-                    { the generic parameters were parsed before the genericdef existed thus the
-                      undefineddefs were added as part of the parent symtable }
-                    if assigned(generictype.typedef.owner) then
-                      generictype.typedef.owner.DefList.Extract(generictype.typedef);
-                    generictype.typedef.changeowner(st);
+                    generictypedef:=ttypesym(generictype).typedef;
+                    if (generictypedef.typ=undefineddef) and (generictypedef<>cundefinedtype) then
+                      begin
+                        { the generic parameters were parsed before the genericdef existed thus the
+                          undefineddefs were added as part of the parent symtable }
+                        if assigned(generictypedef.owner) then
+                          generictypedef.owner.DefList.Extract(generictypedef);
+                        generictypedef.changeowner(st);
+                      end;
                   end;
                 st.insert(generictype);
                 include(generictype.symoptions,sp_generic_para);
diff --git a/compiler/ppu.pas b/compiler/ppu.pas
index 10c42e7eb8..31011be3e8 100644
--- a/compiler/ppu.pas
+++ b/compiler/ppu.pas
@@ -43,7 +43,7 @@ type
 {$endif Test_Double_checksum}
 
 const
-  CurrentPPUVersion = 201;
+  CurrentPPUVersion = 203;
 
 { unit flags }
   uf_init                = $000001; { unit has initialization section }
diff --git a/compiler/pstatmnt.pas b/compiler/pstatmnt.pas
index f528168733..16b5860e9d 100644
--- a/compiler/pstatmnt.pas
+++ b/compiler/pstatmnt.pas
@@ -360,7 +360,12 @@ implementation
           begin
             if (hp.nodetype=ordconstn) and
                (fordef.typ<>errordef) then
-              testrange(fordef,tordconstnode(hp).value,false,true);
+              begin
+                { the node was derived from a generic parameter so ignore range check }
+                if nf_generic_para in hp.flags then
+                  exit;
+                testrange(fordef,tordconstnode(hp).value,false,true);
+              end;
           end;
 
         function for_loop_create(hloopvar: tnode): tnode;
diff --git a/compiler/ptype.pas b/compiler/ptype.pas
index 38e2526e9f..28cd0f94f8 100644
--- a/compiler/ptype.pas
+++ b/compiler/ptype.pas
@@ -1436,7 +1436,9 @@ implementation
                                  highval:=tordconstnode(trangenode(pt).right).value;
                                  if highval<lowval then
                                   begin
-                                    Message(parser_e_array_lower_less_than_upper_bound);
+                                    { ignore error if node is generic param }
+                                    if not (nf_generic_para in pt.flags) then
+                                      Message(parser_e_array_lower_less_than_upper_bound);
                                     highval:=lowval;
                                   end
                                  else if (lowval<int64(low(asizeint))) or
diff --git a/compiler/symconst.pas b/compiler/symconst.pas
index a5ae7e0fb9..d1411039fd 100644
--- a/compiler/symconst.pas
+++ b/compiler/symconst.pas
@@ -205,8 +205,9 @@ type
                               generic is encountered to ease inline
                               specializations, etc; those symbols can be
                               "overridden" with a completely different symbol }
-    sp_explicitrename       { this is used to keep track of type renames created
+    sp_explicitrename,      { this is used to keep track of type renames created
                               by the user }
+    sp_generic_const
   );
   tsymoptions=set of tsymoption;
 
@@ -232,7 +233,10 @@ type
       because we have to access this information in the symtable unit }
     df_llvm_no_struct_packing,
     { internal def that's not for any export }
-    df_internal
+    df_internal,
+    { the def was derived with generic type or const fields so the size
+      of the def can not be determined }
+    df_has_generic_fields
   );
   tdefoptions=set of tdefoption;
 
@@ -651,7 +655,7 @@ type
     arraydef,recorddef,pointerdef,orddef,
     stringdef,enumdef,procdef,objectdef,errordef,
     filedef,formaldef,setdef,procvardef,floatdef,
-    classrefdef,forwarddef,variantdef,undefineddef
+    classrefdef,forwarddef,variantdef,genericconstdef,undefineddef
   );
 
   { possible types for symtable entries }
@@ -692,7 +696,8 @@ type
   tconsttyp = (constnone,
     constord,conststring,constreal,
     constset,constpointer,constnil,
-    constresourcestring,constwstring,constguid
+    constresourcestring,constwstring,constguid,
+    constundefined
   );
 
   { RTTI information to store }
@@ -831,7 +836,7 @@ inherited_objectoptions : tobjectoptions = [oo_has_virtual,oo_has_private,oo_has
        'abstractdef','arraydef','recorddef','pointerdef','orddef',
        'stringdef','enumdef','procdef','objectdef','errordef',
        'filedef','formaldef','setdef','procvardef','floatdef',
-       'classrefdef','forwarddef','variantdef','undefineddef'
+       'classrefdef','forwarddef','variantdef','genconstdef','undefineddef'
      );
 
      EqualTypeName : array[tequaltype] of string[16] = (
diff --git a/compiler/symdef.pas b/compiler/symdef.pas
index 4a260c46b9..0f7a2e4c06 100644
--- a/compiler/symdef.pas
+++ b/compiler/symdef.pas
@@ -129,6 +129,9 @@ interface
           function is_generic:boolean;inline;
           { same as above for specializations }
           function is_specialization:boolean;inline;
+          { generic utilities }
+          function is_generic_param_const(index:integer):boolean;inline;
+          function get_generic_param_def(index:integer):tdef;inline;
           { registers this def in the unit's deflist; no-op if already registered }
           procedure register_def; override;
           { add the def to the top of the symtable stack if it's not yet owned
@@ -2197,13 +2200,26 @@ implementation
          for i:=0 to genericparas.count-1 do
            begin
              sym:=tsym(genericparas[i]);
-             if sym.typ<>symconst.typesym then
+             { sym must be either a type or const }
+             if not (sym.typ in [symconst.typesym,symconst.constsym]) then
                internalerror(2014050903);
              if sym.owner.defowner<>self then
                exit(false);
            end;
      end;
 
+   function tstoreddef.is_generic_param_const(index:integer):boolean;
+     begin
+       result := tsym(genericparas[index]).typ = constsym;
+     end;  
+
+   function tstoreddef.get_generic_param_def(index:integer):tdef;
+     begin
+       if tsym(genericparas[index]).typ = constsym then
+         result := tconstsym(genericparas[index]).constdef
+       else
+         result := ttypesym(genericparas[index]).typedef;
+     end;
 
    function tstoreddef.is_specialization: boolean;
      var
@@ -2220,12 +2236,12 @@ implementation
            for i:=0 to genericparas.count-1 do
              begin
                sym:=tsym(genericparas[i]);
-               if sym.typ<>symconst.typesym then
+               { sym must be either a type or const }
+               if not (sym.typ in [symconst.typesym,symconst.constsym]) then
                  internalerror(2014050904);
                if sym.owner.defowner<>self then
                  exit(true);
              end;
-           result:=false;
          end;
      end;
 
diff --git a/compiler/symsym.pas b/compiler/symsym.pas
index b21a5f9de9..04c07a5ec7 100644
--- a/compiler/symsym.pas
+++ b/compiler/symsym.pas
@@ -157,7 +157,7 @@ interface
           fprettyname : ansistring;
           constructor create(const n : string;def:tdef;doregister:boolean);virtual;
           destructor destroy;override;
-          constructor ppuload(ppufile:tcompilerppufile);
+          constructor ppuload(ppufile:tcompilerppufile);virtual;
           { do not override this routine in platform-specific subclasses,
             override ppuwrite_platform instead }
           procedure ppuwrite(ppufile:tcompilerppufile);override;final;
@@ -392,6 +392,7 @@ interface
           constructor create_ptr(const n : string;t : tconsttyp;v : pointer;def:tdef);virtual;
           constructor create_string(const n : string;t : tconsttyp;str:pchar;l:longint;def:tdef);virtual;
           constructor create_wstring(const n : string;t : tconsttyp;pw:pcompilerwidestring);virtual;
+          constructor create_undefined(const n : string;def: tdef);
           constructor ppuload(ppufile:tcompilerppufile);
           destructor  destroy;override;
           procedure buildderef;override;
@@ -1581,7 +1582,6 @@ implementation
           tparasymtable(parast).ppuwrite(ppufile);
       end;
 
-
 {****************************************************************************
                             TABSTRACTVARSYM
 ****************************************************************************}
@@ -2344,6 +2344,13 @@ implementation
          value.len:=getlengthwidestring(pw);
       end;
 
+    constructor tconstsym.create_undefined(const n : string;def: tdef);
+      begin
+        inherited create(constsym,n,true);
+        fillchar(value, sizeof(value), #0);
+        consttyp:=constundefined;
+        constdef:=def;
+      end;
 
     constructor tconstsym.ppuload(ppufile:tcompilerppufile);
       var
@@ -2416,7 +2423,8 @@ implementation
                new(pguid(value.valueptr));
                ppufile.getdata(value.valueptr^,sizeof(tguid));
              end;
-           constnil :
+           constnil,
+           constundefined :
              ppufile.getderef(constdefderef);
            else
              Message1(unit_f_ppu_invalid_entry,tostr(ord(consttyp)));
@@ -2448,7 +2456,7 @@ implementation
       begin
         inherited;
         case consttyp  of
-          constnil,constord,constreal,constpointer,constset,conststring,constresourcestring,constguid:
+          constnil,constord,constreal,constpointer,constset,conststring,constresourcestring,constguid,constundefined:
             constdefderef.build(constdef);
           constwstring:
             ;
@@ -2461,7 +2469,7 @@ implementation
     procedure tconstsym.deref;
       begin
         case consttyp of
-          constnil,constord,constreal,constpointer,constset,conststring,constresourcestring,constguid:
+          constnil,constord,constreal,constpointer,constset,conststring,constresourcestring,constguid,constundefined:
             constdef:=tdef(constdefderef.resolve);
           constwstring:
             constdef:=carraydef.getreusable(cwidechartype,getlengthwidestring(pcompilerwidestring(value.valueptr)));
@@ -2476,7 +2484,8 @@ implementation
          inherited ppuwrite(ppufile);
          ppufile.putbyte(byte(consttyp));
          case consttyp of
-           constnil :
+           constnil,
+           constundefined :
              ppufile.putderef(constdefderef);
            constord :
              begin
@@ -2627,7 +2636,6 @@ implementation
           result:=inherited prettyname;
       end;
 
-
 {****************************************************************************
                                   TSYSSYM
 ****************************************************************************}
diff --git a/compiler/symtable.pas b/compiler/symtable.pas
index 796b2d6736..ae82024b03 100644
--- a/compiler/symtable.pas
+++ b/compiler/symtable.pas
@@ -2781,7 +2781,7 @@ implementation
 
     function generate_objectpascal_helper_key(def:tdef):string;
       begin
-        if not assigned(def) then
+        if not assigned(def) or (def.typ = errordef) then
           internalerror(2013020501);
         if def.typ in [recorddef,objectdef] then
           result:=make_mangledname('',tabstractrecorddef(def).symtable,'')
diff --git a/compiler/utils/ppuutils/ppudump.pp b/compiler/utils/ppuutils/ppudump.pp
index 74fde5c6c2..dd1db81af7 100644
--- a/compiler/utils/ppuutils/ppudump.pp
+++ b/compiler/utils/ppuutils/ppudump.pp
@@ -1389,6 +1389,7 @@ const
      (mask:sp_has_deprecated_msg; str:'Has Deprecated Message'),
      (mask:sp_generic_dummy;      str:'Generic Dummy'),
      (mask:sp_explicitrename;     str:'Explicit Rename')
+     (mask:sp_generic_const;      str:'Generic Constant Parameter'),
   );
 var
   symoptions : tsymoptions;
@@ -1552,7 +1553,8 @@ const
      { this should never happen for defs stored to a ppu file }
      (mask:df_not_registered_no_free;  str:'Unregistered/No free (invalid)'),
      (mask:df_llvm_no_struct_packing;  str:'LLVM unpacked struct'),
-     (mask:df_internal;       str:'Internal')
+     (mask:df_internal;       str:'Internal'),
+     (mask:df_has_generic_fields; str:'Has generic fields')
   );
   defstate : array[1..ord(high(tdefstate))] of tdefstateinfo=(
      (mask:ds_vmt_written;           str:'VMT Written'),
diff --git a/tests/test/tgenconst1.pp b/tests/test/tgenconst1.pp
new file mode 100644
index 0000000000..297b982b0f
--- /dev/null
+++ b/tests/test/tgenconst1.pp
@@ -0,0 +1,33 @@
+{$mode objfpc}
+program tgenconst1;
+
+type
+	kNames = set of (Blaise,Pascal);
+	kChars = set of char;
+type
+	generic TBoolean<const U: boolean> = record end;
+	generic TString<const U: string> = record end;
+	generic TFloat<const U: single> = record end;
+	generic TInteger<const U: integer> = record end;
+	generic TChar<const U: char> = record end;
+	generic TByte<const U: byte> = record end;
+	generic TQWord<const U: QWord> = record end;
+	generic TUndefined<const U> = record end;
+	generic TNames<const U: kNames> = record end;
+	generic TChars<const U: kChars> = record end;
+	generic TPointer<const U: pointer> = record end;
+
+var
+	a: specialize TBoolean<true>;
+	b: specialize TString<'string'>;
+	c: specialize TFloat<1>;
+	d: specialize TInteger<10>;
+	e: specialize TByte<255>;
+	f: specialize TChar<'a'>;
+	g: specialize TUndefined<nil>;
+	h: specialize TNames<[Blaise,Pascal]>;
+	i: specialize TChars<['a','b']>;
+	j: specialize TQWord<10>;
+	k: specialize TPointer<nil>;
+begin
+end.
diff --git a/tests/test/tgenconst10.pp b/tests/test/tgenconst10.pp
new file mode 100644
index 0000000000..f05a27718c
--- /dev/null
+++ b/tests/test/tgenconst10.pp
@@ -0,0 +1,13 @@
+{%FAIL}
+
+{$mode objfpc}
+
+program tgenconst10;
+
+type
+	generic TByte<T> = record end;
+	
+var
+	a: specialize TByte<10>;
+begin
+end.
diff --git a/tests/test/tgenconst11.pp b/tests/test/tgenconst11.pp
new file mode 100644
index 0000000000..ea409bec9b
--- /dev/null
+++ b/tests/test/tgenconst11.pp
@@ -0,0 +1,21 @@
+{%FAIL}
+{$mode objfpc}
+program tgenconst11;
+type
+	TEnum = (aaa,bbb,ccc,ddd);
+type
+	generic TConst<const U> = class end;
+
+var
+	a:specialize TConst<10>;
+	b:specialize TConst<10.5>;
+	c:specialize TConst<'string'>;
+	d:specialize TConst<[1,2,3]>;
+	e:specialize TConst<[aaa,bbb,ccc]>;
+begin
+	a:=specialize TConst<20>.Create;
+	b:=specialize TConst<10.1>.Create;
+	c:=specialize TConst<'_string'>.Create;
+	d:=specialize TConst<[1,2,3,4]>.Create;
+	e:=specialize TConst<[aaa,bbb,ccc,ddd]>.Create;
+end.
\ No newline at end of file
diff --git a/tests/test/tgenconst12.pp b/tests/test/tgenconst12.pp
new file mode 100644
index 0000000000..8f591f6867
--- /dev/null
+++ b/tests/test/tgenconst12.pp
@@ -0,0 +1,16 @@
+{$mode objfpc}
+program tgenconst12;
+
+type
+  generic TTest<const U> = class
+  		class procedure DoThis;
+  end;
+
+class procedure TTest.DoThis;
+begin
+end;
+
+type
+	ATest = specialize TTest<100>;
+begin 
+end.
diff --git a/tests/test/tgenconst13.pp b/tests/test/tgenconst13.pp
new file mode 100644
index 0000000000..0d5f8b1813
--- /dev/null
+++ b/tests/test/tgenconst13.pp
@@ -0,0 +1,20 @@
+{$mode objfpc}
+program tgenconst13;
+type
+	TEnum = (aaa,bbb,ccc);
+type
+	generic TConst<const U> = class end;
+
+var
+	a:specialize TConst<10>;
+	b:specialize TConst<10.5>;
+	c:specialize TConst<'string'>;
+	d:specialize TConst<[1,2,3]>;
+	e:specialize TConst<[aaa,bbb,ccc]>;
+begin
+	a:=specialize TConst<10>.Create;
+	b:=specialize TConst<10.5>.Create;
+	c:=specialize TConst<'string'>.Create;
+	d:=specialize TConst<[1,2,3]>.Create;
+	e:=specialize TConst<[aaa,bbb,ccc]>.Create;
+end.
diff --git a/tests/test/tgenconst14.pp b/tests/test/tgenconst14.pp
new file mode 100644
index 0000000000..7f98086630
--- /dev/null
+++ b/tests/test/tgenconst14.pp
@@ -0,0 +1,29 @@
+{$mode objfpc}
+{$modeswitch advancedrecords}
+program tgenconst14;
+
+type
+  generic TBinaryOp<const I: Integer> = record
+    const
+    	d0 = I + I;
+    	d1 = I - I; 
+    	d2 = I * I; 
+    	d3 = I / I; 
+    	d4 = I div I; 
+    	d5 = I mod I; 
+    	d6 = I and I;
+    	d7 = I or I;
+  end;
+
+var
+	op: specialize TBinaryOp<100>;
+begin
+	writeln(op.d0);
+	writeln(op.d1);
+	writeln(op.d2);
+	writeln(op.d3:1:1);
+	writeln(op.d4);
+	writeln(op.d5);
+	writeln(op.d6);
+	writeln(op.d7);
+end.
\ No newline at end of file
diff --git a/tests/test/tgenconst15.pp b/tests/test/tgenconst15.pp
new file mode 100644
index 0000000000..56744cd0a7
--- /dev/null
+++ b/tests/test/tgenconst15.pp
@@ -0,0 +1,30 @@
+{$mode objfpc}
+{$modeswitch advancedrecords}
+program tgenconst15;
+
+type
+	kNames = set of (Blaise, Pascal);
+  generic TSet<const I: kNames> = record
+    const c = I;
+  end;
+  generic TString<const I: String> = record
+    const c = I;
+  end;
+  generic TWideString<const I: WideString> = record
+    const c = I;
+  end;
+  generic TSingle<const I: Single> = record
+    const c = I; 
+  end;
+  generic TDouble<const I: Double> = record
+    const c = I; 
+  end;
+  generic TReal<const I: Real> = record
+    const c = I; 
+  end;
+
+var
+	a0: specialize TReal<100>;
+begin
+	writeln(a0.c);
+end.
\ No newline at end of file
diff --git a/tests/test/tgenconst16.pp b/tests/test/tgenconst16.pp
new file mode 100644
index 0000000000..275867ce25
--- /dev/null
+++ b/tests/test/tgenconst16.pp
@@ -0,0 +1,86 @@
+{$mode objfpc}
+{$modeswitch advancedrecords}
+program tgenconst16;
+
+type
+  Day = (mon,tue,wed,thu,fri,sat,sun);  
+  Days = set of Day;  
+  generic TSet<const I: Days> = record
+    const
+      d0 = I + I;   // Union
+      d1 = I - I;   // Difference
+      d2 = I * I;   // Intersection
+      d3 = I >< I;  // Symmetric difference
+      d4 = I <= I;  // Contains
+      d5 = mon in I;
+  end;
+  generic TArray<const I> = record
+    type
+      t0 = array[0..I - 1] of integer;
+      t1 = array[0..high(I)] of integer;
+      t2 = array[0..low(I)] of integer;
+      t3 = array[0..sizeof(I)] of integer;
+    public
+      d0: array[0..I - 1] of integer;
+      d1: array[0..high(I)] of integer;
+      d2: array[0..low(I)] of integer;
+      d3: array[0..sizeof(I)] of integer;
+  end;
+  generic TUnaryOp<const I> = record
+    const
+      d0 = -I;
+      d1 = +I;
+      d2 = not I;
+  end;
+  generic TBinaryOp<const I> = record
+    const
+      // Arithmetic operators
+      // https://freepascal.org/docs-html/ref/refsu45.html
+      d0 = I + I;
+      d1 = I - I;
+      d2 = I * I; 
+      d3 = I / I; 
+      d4 = I div I; 
+      d5 = I mod I; 
+      // Boolean operators
+      // https://freepascal.org/docs-html/ref/refsu47.html
+      d6 = I and I;
+      d7 = I or I;
+      d8 = I xor I;
+      // Logical operators
+      // https://freepascal.org/docs-html/ref/refsu46.html
+      d9 = I shl I;
+      d10 = I shr I;
+      d11 = I << I;
+      d12 = I >> I;
+      // Relational operators
+      // https://freepascal.org/docs-html/ref/refsu50.html#x153-17500012.8.6
+      d13 = I <> I;
+      d14 = I < I;
+      d15 = I > I;
+      d16 = I <= I;
+      d17 = I >= I;
+      d18 = I = I;
+  end;
+  generic TOther<const I> = record
+    procedure DoThis(param: integer = I);
+  end;
+
+procedure TOther.DoThis(param: integer = I);
+begin
+  writeln(param, ' default:', I);
+end;
+
+var
+  t0: specialize TBinaryOp<100>;
+  t1: specialize TOther<100>;
+begin
+  //writeln(op.d0);
+  //writeln(op.d1);
+  //writeln(op.d2);
+  //writeln(op.d3:1:1);
+  //writeln(op.d4);
+  //writeln(op.d5);
+  //writeln(op.d6);
+  //writeln(op.d7);
+end.
\ No newline at end of file
diff --git a/tests/test/tgenconst17.pp b/tests/test/tgenconst17.pp
new file mode 100644
index 0000000000..26dc2ee21f
--- /dev/null
+++ b/tests/test/tgenconst17.pp
@@ -0,0 +1,36 @@
+{$mode objfpc}
+{$modeswitch advancedrecords}
+program tgenconst17;
+
+type
+  generic TUnaryOp<const I: integer> = record
+    const
+      d0 = -I;
+      d1 = +I;
+      d2 = not I;
+  end;
+  generic TBinaryOp<const I: integer> = record
+    const
+      d0 = I + I;
+      d1 = I - I;
+      d2 = I * I; 
+      d3 = I / I; 
+      d4 = I div I; 
+      d5 = I mod I; 
+      d6 = I and I;
+      d7 = I or I;
+      d8 = I xor I;
+      d9 = I shl I;
+      d10 = I shr I;
+      d11 = I << I;
+      d12 = I >> I;
+      d13 = I <> I;
+      d14 = I < I;
+      d15 = I > I;
+      d16 = I <= I;
+      d17 = I >= I;
+      d18 = I = I;
+  end;
+
+begin
+end.
\ No newline at end of file
diff --git a/tests/test/tgenconst18.pp b/tests/test/tgenconst18.pp
new file mode 100644
index 0000000000..a4ba526803
--- /dev/null
+++ b/tests/test/tgenconst18.pp
@@ -0,0 +1,12 @@
+{%FAIL}
+{$mode objfpc}
+{$modeswitch advancedrecords}
+program tgenconst18;
+
+type
+  generic TInt<const I: string> = record
+    const c = I div I;
+  end;
+
+begin
+end.
\ No newline at end of file
diff --git a/tests/test/tgenconst19.pp b/tests/test/tgenconst19.pp
new file mode 100644
index 0000000000..b7538b17a9
--- /dev/null
+++ b/tests/test/tgenconst19.pp
@@ -0,0 +1,49 @@
+{$mode objfpc}
+{$modeswitch advancedrecords}
+
+program tgenconst19;
+
+type
+	kNames = set of (Blaise,Pascal);
+	kChars = set of char;
+type
+	generic TBoolean<const U: boolean> = record const value = U; end;
+	generic TString<const U: string> = record const value = U; end;
+	generic TFloat<const U: single> = record const value = U; end;
+	generic TInteger<const U: integer> = record const value = U; end;
+	generic TByte<const U: byte> = record const value = U; end;
+	generic TChar<const U: char> = record const value = U; end;
+	generic TQWord<const U: QWord> = record const value = U; end;
+	generic TNames<const U: kNames> = record const value = U; end;
+	generic TChars<const U: kChars> = record const value = U; end;
+
+procedure Test(failed: boolean); inline;
+begin
+	if failed then
+		begin
+			writeln('failed!');
+			halt(-1);
+		end;
+end;
+
+var
+	g0: specialize TBoolean<true>;
+	g1: specialize TString<'string'>;
+	g2: specialize TFloat<10.5>;
+	g3: specialize TInteger<10>;
+	g4: specialize TByte<255>;
+	g5: specialize TChar<'a'>;
+	g6: specialize TQWord<1000000000>;
+	g7: specialize TNames<[Blaise,Pascal]>;
+	g8: specialize TChars<['a','b']>;
+begin
+	Test(g0.value <> true);
+	Test(g1.value <> 'string');
+	Test(g2.value <> 10.5);
+	Test(g3.value <> 10);
+	Test(g4.value <> 255);
+	Test(g5.value <> 'a');
+	Test(g6.value <> 1000000000);
+	Test(g7.value <> [Blaise,Pascal]);
+	Test(g8.value <> ['a','b']);
+end.
diff --git a/tests/test/tgenconst2.pp b/tests/test/tgenconst2.pp
new file mode 100644
index 0000000000..aa3a960634
--- /dev/null
+++ b/tests/test/tgenconst2.pp
@@ -0,0 +1,12 @@
+{$mode objfpc}
+program tgenconst2;
+
+type
+	generic TStuff1<T1,T2;const U1,U2> = record end;
+	generic TStuff2<T1,T2;const U1,U2:integer> = record end;
+	
+var
+	a: specialize TStuff1<integer,string,10,'string'>;
+	b: specialize TStuff2<integer,string,10,10>;
+begin
+end.
diff --git a/tests/test/tgenconst20.pp b/tests/test/tgenconst20.pp
new file mode 100644
index 0000000000..b87f0b2af1
--- /dev/null
+++ b/tests/test/tgenconst20.pp
@@ -0,0 +1,24 @@
+{$mode objfpc}
+{$modeswitch advancedrecords}
+
+program tgenconst20;
+
+{ testing range checking for arrays and for-loops }
+type
+	generic TStaticList<T; const Length: SizeUInt> = record
+	  Values: array[0..Length - 1] of T;
+	  procedure Display;
+	end;
+
+procedure TStaticList.Display;
+var 
+	I, n: SizeUInt;
+begin
+  for I := 0 to Length - 1 do
+  	WriteLn(Values[I]);
+end;
+
+var
+	list: specialize TStaticList<Integer, 20>;
+begin
+end.
diff --git a/tests/test/tgenconst3.pp b/tests/test/tgenconst3.pp
new file mode 100644
index 0000000000..aea0e307e2
--- /dev/null
+++ b/tests/test/tgenconst3.pp
@@ -0,0 +1,16 @@
+{$mode objfpc}
+{$modeswitch advancedrecords}
+program tgenconst3;
+
+type
+	generic TList<T;const U:integer> = record
+		const
+			max = U;
+		public
+			m_list: array[0..max-1] of T;
+	end;
+
+var
+	list: specialize TList<integer,128>;
+begin
+end.
diff --git a/tests/test/tgenconst4.pp b/tests/test/tgenconst4.pp
new file mode 100644
index 0000000000..a1fae00c43
--- /dev/null
+++ b/tests/test/tgenconst4.pp
@@ -0,0 +1,11 @@
+{$mode objfpc}
+program tgenconst4;
+
+generic procedure DoThis<T;const U:string>(msg:string = U);
+begin
+	writeln(msg, ' sizeof:',sizeof(t), ' default: ', U);
+end;
+
+begin
+	specialize DoThis<integer,'genparam'>('hello world');
+end.
diff --git a/tests/test/tgenconst5.pp b/tests/test/tgenconst5.pp
new file mode 100644
index 0000000000..63514a976c
--- /dev/null
+++ b/tests/test/tgenconst5.pp
@@ -0,0 +1,24 @@
+{$mode objfpc}
+program tgenconst5;
+
+type
+	generic THelperA<const U:integer> = record
+		list: array[0..U-1] of byte;
+	end;
+
+type
+	generic THelperB<T> = record
+		value: T;
+	end;
+
+type
+	generic TList<T; const U:integer> = record
+		helperA: specialize THelperA<U>;
+		helperB: specialize THelperB<T>;
+	end;
+
+var
+	list: specialize TList<integer,32>;
+begin
+	writeln('sizeof:',sizeof(list));
+end.
diff --git a/tests/test/tgenconst6.pp b/tests/test/tgenconst6.pp
new file mode 100644
index 0000000000..3ee3785423
--- /dev/null
+++ b/tests/test/tgenconst6.pp
@@ -0,0 +1,21 @@
+{$mode delphi}
+program tgenconst6;
+
+type
+	TList<T;const U> = class
+		list: array[0..U-1] of T;
+		function capacity: integer;
+	end;
+
+function TList<T,U>.capacity: integer;
+begin
+	result := U;	
+end;	
+
+var
+	nums:TList<integer,16>;
+	strs:TList<string,16>;
+begin
+	nums := TList<integer,16>.Create;
+	strs := TList<string,16>.Create;
+end.
diff --git a/tests/test/tgenconst7.pp b/tests/test/tgenconst7.pp
new file mode 100644
index 0000000000..9d8e81ef05
--- /dev/null
+++ b/tests/test/tgenconst7.pp
@@ -0,0 +1,11 @@
+{%FAIL}
+{$mode objfpc}
+program tgenconst7;
+
+type
+	generic TInteger<const U: integer> = record end;
+
+var
+	a: specialize TInteger<'string'>;
+begin
+end.
diff --git a/tests/test/tgenconst8.pp b/tests/test/tgenconst8.pp
new file mode 100644
index 0000000000..75844f7181
--- /dev/null
+++ b/tests/test/tgenconst8.pp
@@ -0,0 +1,11 @@
+{%FAIL}
+{$mode objfpc}
+program tgenconst8;
+
+type
+	generic TByte<const U: Byte> = record end;
+	
+var
+	a: specialize TByte<300>;
+begin
+end.
diff --git a/tests/test/tgenconst9.pp b/tests/test/tgenconst9.pp
new file mode 100644
index 0000000000..939cb90302
--- /dev/null
+++ b/tests/test/tgenconst9.pp
@@ -0,0 +1,11 @@
+{%FAIL}
+{$mode objfpc}
+program tgenconst9;
+
+type
+	generic TByte<const U: Byte> = record end;
+	
+var
+	a: specialize TByte<string>;
+begin
+end.
-- 
2.17.2 (Apple Git-113)

diff --git a/compiler/defcmp.pas b/compiler/defcmp.pas
index 67f3119557..a61988d770 100644
--- a/compiler/defcmp.pas
+++ b/compiler/defcmp.pas
@@ -175,7 +175,6 @@ implementation
       symtable,symsym,symcpu,
       defutil,symutil;
 
-
     function compare_defs_ext(def_from,def_to : tdef;
                               fromtreetype : tnodetype;
                               var doconv : tconverttype;
@@ -345,9 +344,13 @@ implementation
                        internalerror(2012091302);
                      symfrom:=ttypesym(tstoreddef(def_from).genericparas[i]);
                      symto:=ttypesym(tstoreddef(def_to).genericparas[i]);
-                     if not (symfrom.typ=typesym) or not (symto.typ=typesym) then
+                     if not (symfrom.typ in [typesym,constsym]) or not (symto.typ in [typesym,constsym]) then
                        internalerror(2012121401);
-                     if not equal_defs(ttypesym(symfrom).typedef,ttypesym(symto).typedef) then
+                     if symto.typ <> symfrom.typ then
+                       diff:=true
+                     else if (symfrom.typ=constsym) and (symto.typ=constsym) and not equal_constsym(tconstsym(symfrom),tconstsym(symto),true) then
+                       diff:=true
+                     else if not equal_defs(ttypesym(symfrom).typedef,ttypesym(symto).typedef) then
                        diff:=true;
                      if diff then
                        break;
diff --git a/compiler/htypechk.pas b/compiler/htypechk.pas
index e3b66a6f75..9ec84a240a 100644
--- a/compiler/htypechk.pas
+++ b/compiler/htypechk.pas
@@ -2775,7 +2775,7 @@ implementation
               internalerror(2015060301);
             { check whether the given parameters are compatible
               to the def's constraints }
-            if not check_generic_constraints(pd,spezcontext.genericdeflist,spezcontext.poslist) then
+            if not check_generic_constraints(pd,spezcontext.paramlist,spezcontext.poslist) then
               exit;
             def:=generate_specialization_phase2(spezcontext,pd,false,'');
             case def.typ of
diff --git a/compiler/ncnv.pas b/compiler/ncnv.pas
index 541e418d5d..863d3f60d5 100644
--- a/compiler/ncnv.pas
+++ b/compiler/ncnv.pas
@@ -3099,7 +3099,8 @@ implementation
                        { for constant values on absolute variables, swapping is required }
                        if (target_info.endian = endian_big) and (nf_absolute in flags) then
                          swap_const_value(tordconstnode(left).value,tordconstnode(left).resultdef.size);
-                       adaptrange(resultdef,tordconstnode(left).value,([nf_internal,nf_absolute]*flags)<>[],nf_explicit in flags,cs_check_range in localswitches);
+                       if not(nf_generic_para in flags) then
+                       	 adaptrange(resultdef,tordconstnode(left).value,([nf_internal,nf_absolute]*flags)<>[],nf_explicit in flags,cs_check_range in localswitches);
                        { swap value back, but according to new type }
                        if (target_info.endian = endian_big) and (nf_absolute in flags) then
                          swap_const_value(tordconstnode(left).value,resultdef.size);
diff --git a/compiler/ncon.pas b/compiler/ncon.pas
index 61255c6c48..f723750917 100644
--- a/compiler/ncon.pas
+++ b/compiler/ncon.pas
@@ -306,6 +306,7 @@ implementation
         p1  : tnode;
         len : longint;
         pc  : pchar;
+        value_set : pconstset;
       begin
         p1:=nil;
         case p.consttyp of
@@ -331,18 +332,50 @@ implementation
           constwstring :
             p1:=cstringconstnode.createunistr(pcompilerwidestring(p.value.valueptr));
           constreal :
-            p1:=crealconstnode.create(pbestreal(p.value.valueptr)^,p.constdef);
+            begin
+              if (sp_generic_para in p.symoptions) and not (sp_generic_const in p.symoptions) then
+                p1:=crealconstnode.create(default(bestreal),p.constdef)
+              else
+                p1:=crealconstnode.create(pbestreal(p.value.valueptr)^,p.constdef);
+            end;
           constset :
-            p1:=csetconstnode.create(pconstset(p.value.valueptr),p.constdef);
+            begin
+              if sp_generic_const in p.symoptions then
+                begin
+                  new(value_set);
+                  value_set^:=pconstset(p.value.valueptr)^;
+                  p1:=csetconstnode.create(value_set,p.constdef);
+                end
+              else if sp_generic_para in p.symoptions then
+                begin
+                  new(value_set);
+                  p1:=csetconstnode.create(value_set,p.constdef);
+                end
+              else
+                p1:=csetconstnode.create(pconstset(p.value.valueptr),p.constdef);
+            end;
           constpointer :
-            p1:=cpointerconstnode.create(p.value.valueordptr,p.constdef);
+            begin
+              if sp_generic_para in p.symoptions then
+                p1:=cpointerconstnode.create(default(tconstptruint),p.constdef)
+              else
+                p1:=cpointerconstnode.create(p.value.valueordptr,p.constdef);
+            end;
           constnil :
             p1:=cnilnode.create;
           constguid :
-            p1:=cguidconstnode.create(pguid(p.value.valueptr)^);
+            begin
+              if sp_generic_para in p.symoptions then
+                p1:=cguidconstnode.create(default(tguid))
+              else
+                p1:=cguidconstnode.create(pguid(p.value.valueptr)^);
+            end;
           else
             internalerror(200205103);
         end;
+        { transfer generic param flag from symbol to node }
+        if sp_generic_para in p.symoptions then
+          include(p1.flags,nf_generic_para);
         genconstsymtree:=p1;
       end;
 
diff --git a/compiler/nmat.pas b/compiler/nmat.pas
index fd452ab4a4..7846666e03 100644
--- a/compiler/nmat.pas
+++ b/compiler/nmat.pas
@@ -131,7 +131,10 @@ implementation
               end;
             if rv = 0 then
               begin
-                Message(parser_e_division_by_zero);
+                { if the node is derived from a generic const parameter
+                  then don't issue an error }
+                if not (nf_generic_para in flags) then
+                  Message(parser_e_division_by_zero);
                 { recover }
                 tordconstnode(right).value := 1;
               end;
diff --git a/compiler/node.pas b/compiler/node.pas
index 0c2ba4efbb..1d91cf887b 100644
--- a/compiler/node.pas
+++ b/compiler/node.pas
@@ -276,10 +276,13 @@ interface
          nf_block_with_exit,
 
          { tloadvmtaddrnode }
-         nf_ignore_for_wpo  { we know that this loadvmtaddrnode cannot be used to construct a class instance }
+         nf_ignore_for_wpo,  { we know that this loadvmtaddrnode cannot be used to construct a class instance }
 
-         { WARNING: there are now 31 elements in this type, and a set of this
-             type is written to the PPU. So before adding more than 32 elements,
+         { node is derived from generic parameter }
+         nf_generic_para
+
+         { WARNING: there are now 32 elements in this type, and a set of this
+             type is written to the PPU. So before adding more elements,
              either move some flags to specific nodes, or stream a normalset
              to the ppu
          }
@@ -1380,6 +1383,9 @@ implementation
     constructor tunarynode.create(t:tnodetype;l : tnode);
       begin
          inherited create(t);
+         { transfer generic paramater flag }
+         if assigned(l) and (nf_generic_para in l.flags) then
+           include(flags,nf_generic_para);
          left:=l;
       end;
 
@@ -1482,7 +1488,12 @@ implementation
     constructor tbinarynode.create(t:tnodetype;l,r : tnode);
       begin
          inherited create(t,l);
-         right:=r
+         { transfer generic paramater flag }
+         if assigned(l) and (nf_generic_para in l.flags) then
+           include(flags,nf_generic_para)
+         else if assigned(r) and (nf_generic_para in r.flags) then
+           include(flags,nf_generic_para);
+         right:=r;
       end;
 
 
diff --git a/compiler/nset.pas b/compiler/nset.pas
index 0832b97b20..0b31de9342 100644
--- a/compiler/nset.pas
+++ b/compiler/nset.pas
@@ -424,8 +424,9 @@ implementation
          { both types must be compatible }
          if compare_defs(left.resultdef,right.resultdef,left.nodetype)=te_incompatible then
            IncompatibleTypes(left.resultdef,right.resultdef);
-         { Check if only when its a constant set }
-         if (left.nodetype=ordconstn) and (right.nodetype=ordconstn) then
+         { check if only when its a constant set and
+           ignore range nodes which are generic parameter derived }
+         if not (nf_generic_para in flags) and (left.nodetype=ordconstn) and (right.nodetype=ordconstn) then
           begin
             { upper limit must be greater or equal than lower limit }
             if (tordconstnode(left).value>tordconstnode(right).value) and
diff --git a/compiler/pass_1.pas b/compiler/pass_1.pas
index adbc6d1a42..0e80d10f22 100644
--- a/compiler/pass_1.pas
+++ b/compiler/pass_1.pas
@@ -62,6 +62,7 @@ implementation
     procedure typecheckpass_internal_loop(var p : tnode; out node_changed: boolean);
       var
          hp        : tnode;
+         oldflags  : tnodeflags;
       begin
         codegenerror:=false;
         repeat
@@ -73,9 +74,13 @@ implementation
           if assigned(hp) then
             begin
               node_changed:=true;
+              oldflags:=p.flags;
               p.free;
               { switch to new node }
               p:=hp;
+              { transfer generic paramter flag }
+              if nf_generic_para in oldflags then
+                include(p.flags,nf_generic_para);
             end;
         until not assigned(hp) or
               assigned(hp.resultdef);
diff --git a/compiler/pdecl.pas b/compiler/pdecl.pas
index 872e820cee..d8baee109d 100644
--- a/compiler/pdecl.pas
+++ b/compiler/pdecl.pas
@@ -128,14 +128,15 @@ implementation
              end;
            realconstn :
              begin
-                new(pd);
-                pd^:=trealconstnode(p).value_real;
-                hp:=cconstsym.create_ptr(orgname,constreal,pd,p.resultdef);
+               new(pd);
+               pd^:=trealconstnode(p).value_real;
+               hp:=cconstsym.create_ptr(orgname,constreal,pd,p.resultdef);
              end;
            setconstn :
              begin
                new(ps);
-               ps^:=tsetconstnode(p).value_set^;
+               if assigned(tsetconstnode(p).value_set) then
+                 ps^:=tsetconstnode(p).value_set^;
                hp:=cconstsym.create_ptr(orgname,constset,ps,p.resultdef);
              end;
            pointerconstn :
@@ -185,8 +186,22 @@ implementation
                end;
              end;
            else
-             Message(parser_e_illegal_expression);
+             begin
+               { the node is from a generic parameter constant and is 
+                 untyped so we need to pass a placeholder constant 
+                 instead of givng an error }
+               if nf_generic_para in p.flags then 
+                 hp:=cconstsym.create_ord(orgname,constnil,0,p.resultdef)
+               else
+                 Message(parser_e_illegal_expression);
+             end;
         end;
+        { transfer generic param flag from node to symbol }
+        if nf_generic_para in p.flags then
+          begin
+            include(hp.symoptions,sp_generic_const);
+            include(hp.symoptions,sp_generic_para);
+          end;
         current_tokenpos:=storetokenpos;
         p.free;
         readconstant:=hp;
@@ -715,8 +730,9 @@ implementation
                { we are not freeing the type parameters, so register them }
                for i:=0 to generictypelist.count-1 do
                  begin
-                    ttypesym(generictypelist[i]).register_sym;
-                    tstoreddef(ttypesym(generictypelist[i]).typedef).register_def;
+                    tstoredsym(generictypelist[i]).register_sym;
+                    if tstoredsym(generictypelist[i]).typ=typesym then
+                      tstoreddef(ttypesym(generictypelist[i]).typedef).register_def;
                  end;
 
                str(generictypelist.Count,s);
diff --git a/compiler/pdecsub.pas b/compiler/pdecsub.pas
index c6e1252f49..8296bfa2f3 100644
--- a/compiler/pdecsub.pas
+++ b/compiler/pdecsub.pas
@@ -628,7 +628,7 @@ implementation
               for i:=0 to genericparams.count-1 do
                 begin
                   sym:=ttypesym(genericparams[i]);
-                  if tstoreddef(sym.typedef).is_registered then
+                  if (sym.typ<>constsym) and tstoreddef(sym.typedef).is_registered then
                     begin
                       sym.typedef.free;
                       sym.typedef:=nil;
diff --git a/compiler/pdecvar.pas b/compiler/pdecvar.pas
index 85c47b5132..57f2cf5c1f 100644
--- a/compiler/pdecvar.pas
+++ b/compiler/pdecvar.pas
@@ -1707,6 +1707,10 @@ implementation
                    hdef:=generrordef;
                end;
 
+             { field type is a generic param so set a flag in the struct }
+             if assigned(hdef.typesym) and (sp_generic_para in hdef.typesym.symoptions) then
+               include(current_structdef.defoptions,df_has_generic_fields);
+
              { Process procvar directives }
              if maybe_parse_proc_directives(hdef) then
                semicoloneaten:=true;
diff --git a/compiler/pexpr.pas b/compiler/pexpr.pas
index 3727aef828..ed127d7cbf 100644
--- a/compiler/pexpr.pas
+++ b/compiler/pexpr.pas
@@ -447,6 +447,9 @@ implementation
                   { no packed bit support for these things }
                   if l=in_bitsizeof_x then
                     statement_syssym:=caddnode.create(muln,statement_syssym,cordconstnode.create(8,sizesinttype,true));
+                  { type sym is a generic parameter }
+                  if assigned(p1.resultdef.typesym) and (sp_generic_para in p1.resultdef.typesym.symoptions) then
+                    include(statement_syssym.flags,nf_generic_para);
                 end
               else
                begin
@@ -467,6 +470,9 @@ implementation
                    end
                  else
                    statement_syssym:=cordconstnode.create(p1.resultdef.packedbitsize,sizesinttype,true);
+                 { type def is a struct with generic fields }
+                 if df_has_generic_fields in p1.resultdef.defoptions then
+                    include(statement_syssym.flags,nf_generic_para);
                  { p1 not needed !}
                  p1.destroy;
                end;
@@ -4237,7 +4243,10 @@ implementation
                 gendef:=generate_specialization_phase2(spezcontext,tstoreddef(gendef),false,'');
                 spezcontext.free;
                 spezcontext:=nil;
-                gensym:=gendef.typesym;
+                if gendef.typ=errordef then
+                  gensym:=generrorsym
+                else
+                  gensym:=gendef.typesym;
               end;
             procdef:
               begin
@@ -4591,7 +4600,7 @@ implementation
          filepos : tfileposinfo;
          oldafterassignment,
          updatefpos          : boolean;
-
+         oldflags : tnodeflags;
       begin
          oldafterassignment:=afterassignment;
          p1:=sub_expr(opcompare,[ef_accept_equal],nil);
@@ -4648,6 +4657,10 @@ implementation
           else
             updatefpos:=false;
          end;
+         oldflags:=p1.flags;
+         { transfer generic paramter flag }
+         if nf_generic_para in oldflags then
+           include(p1.flags,nf_generic_para);
          { get the resultdef for this expression }
          if not assigned(p1.resultdef) and
             dotypecheck then
diff --git a/compiler/pgentype.pas b/compiler/pgentype.pas
index b2847c78f6..85270df256 100644
--- a/compiler/pgentype.pas
+++ b/compiler/pgentype.pas
@@ -28,7 +28,7 @@ interface
 uses
   cclasses,
   globtype,
-  symtype,symbase;
+  symconst,symtype,symbase;
 
 const
   inline_specialization_block_types = [bt_type,bt_var_type,bt_const_type,bt_body];
@@ -42,7 +42,7 @@ type
 
   tspecializationcontext=class
   public
-    genericdeflist : tfpobjectlist;
+    paramlist : tfpobjectlist;
     poslist : tfplist;
     prettyname : ansistring;
     specializename : ansistring;
@@ -58,7 +58,7 @@ implementation
 
 constructor tspecializationcontext.create;
 begin
-  genericdeflist:=tfpobjectlist.create(false);
+  paramlist:=tfpobjectlist.create(false);
   poslist:=tfplist.create;
 end;
 
@@ -66,7 +66,7 @@ destructor tspecializationcontext.destroy;
 var
   i : longint;
 begin
-  genericdeflist.free;
+  paramlist.free;
   for i:=0 to poslist.count-1 do
     dispose(pfileposinfo(poslist[i]));
   poslist.free;
diff --git a/compiler/pgenutil.pas b/compiler/pgenutil.pas
index 1069fb7c14..990137e9ba 100644
--- a/compiler/pgenutil.pas
+++ b/compiler/pgenutil.pas
@@ -42,9 +42,9 @@ uses
     function generate_specialization_phase1(out context:tspecializationcontext;genericdef:tdef;symname:string):tdef;inline;
     function generate_specialization_phase1(out context:tspecializationcontext;genericdef:tdef;parsedtype:tdef;symname:string;parsedpos:tfileposinfo):tdef;
     function generate_specialization_phase2(context:tspecializationcontext;genericdef:tstoreddef;parse_class_parent:boolean;_prettyname:ansistring):tdef;
-    function check_generic_constraints(genericdef:tstoreddef;paradeflist:tfpobjectlist;poslist:tfplist):boolean;
+    function check_generic_constraints(genericdef:tstoreddef;paramlist:tfpobjectlist;poslist:tfplist):boolean;
     function parse_generic_parameters(allowconstraints:boolean):tfphashobjectlist;
-    function parse_generic_specialization_types(genericdeflist:tfpobjectlist;poslist:tfplist;out prettyname,specializename:ansistring):boolean;
+    function parse_generic_specialization_types(paramlist:tfpobjectlist;poslist:tfplist;out prettyname,specializename:ansistring):boolean;
     procedure insert_generic_parameter_types(def:tstoreddef;genericdef:tstoreddef;genericlist:tfphashobjectlist);
     procedure maybe_insert_generic_rename_symbol(const name:tidstring;genericlist:tfphashobjectlist);
     function generate_generic_name(const name:tidstring;specializename:ansistring;owner_hierarchy:string):tidstring;
@@ -63,18 +63,150 @@ implementation
 
 uses
   { common }
-  cutils,fpccrc,
+  sysutils,cutils,fpccrc,
   { global }
-  globals,tokens,verbose,finput,
+  globals,tokens,verbose,finput,constexp,
   { symtable }
-  symconst,symsym,symtable,defcmp,procinfo,
+  symconst,symsym,symtable,defcmp,defutil,procinfo,
   { modules }
   fmodule,
-  node,nobj,
+  node,nobj,ncon,
   { parser }
   scanner,
   pbase,pexpr,pdecsub,ptype,psub,pparautl;
 
+  type
+    tdeftypeset = set of tdeftyp;
+  const
+    tgeneric_param_const_types : tdeftypeset = [orddef,stringdef,arraydef,floatdef,setdef,pointerdef,enumdef];
+    tgeneric_param_nodes : tnodetypeset = [typen,ordconstn,stringconstn,realconstn,setconstn,niln];
+
+    function get_generic_param_def(sym:tsym):tdef;
+      begin
+        if sym.typ=constsym then
+          result:=tconstsym(sym).constdef
+        else
+          result:=ttypesym(sym).typedef;
+      end;
+
+    function compare_orddef_by_range(param1,param2:torddef;value:tconstvalue):boolean;
+      begin
+        if (value.len<param2.low) or (value.len>param2.high) then
+          result:=false
+        else
+          result:=true;
+      end;
+
+    function compare_generic_params(param1,param2:tdef;constparamsym:tconstsym):boolean;
+      begin
+        if (param1.typ=orddef) and (param2.typ=orddef) then
+          begin
+            if is_boolean(param2) then
+              result:=is_boolean(param1)
+            else if is_char(param2) then
+              result:=is_char(param1)
+            else if compare_orddef_by_range(torddef(param1),torddef(param2),constparamsym.value) then
+              result:=true
+            else
+              result:=false;
+          end
+        { arraydef is string constant so it's compatible with stringdef }
+        else if (param1.typ=arraydef) and (param2.typ=stringdef) then
+          result:=true
+        { integer ords are compatible with float }
+        else if (param1.typ=orddef) and is_integer(param1) and (param2.typ=floatdef) then
+          result:=true
+        { undefined def is compatible with all types }
+        else if param2.typ=undefineddef then
+          result:=true
+        { sets require stricter checks }
+        else if is_set(param2) then
+          result:=equal_defs(param1,param2)
+        else
+          result:=param1.typ=param2.typ;
+      end;
+
+    function create_generic_constsym(fromdef:tdef;node:tnode;out prettyname:string):tconstsym;
+      const
+        undefinedname = 'undefined';
+      var
+        sym : tconstsym;
+        setdef : tsetdef;
+        enumsym : tsym;
+        enumname : string;
+        sp : pchar;
+        ps : ^tconstset;
+        pd : ^bestreal;
+        i : integer;
+      begin
+        if node=nil then
+          internalerror(2020011401);
+        case node.nodetype of
+          ordconstn:
+            begin
+              sym:=cconstsym.create_ord(undefinedname,constord,tordconstnode(node).value,fromdef);
+              prettyname:=inttostr(tordconstnode(node).value.svalue);
+            end;
+          stringconstn:
+            begin
+              getmem(sp,tstringconstnode(node).len+1);
+              move(tstringconstnode(node).value_str^,sp^,tstringconstnode(node).len+1);
+              sym:=cconstsym.create_string(undefinedname,conststring,sp,tstringconstnode(node).len,fromdef);
+              prettyname:=''''+tstringconstnode(node).value_str+'''';
+            end;
+          realconstn:
+            begin
+              new(pd);
+              pd^:=trealconstnode(node).value_real;
+              sym:=cconstsym.create_ptr(undefinedname,constreal,pd,fromdef);
+              prettyname:=floattostr(trealconstnode(node).value_real);
+            end;
+          setconstn:
+            begin
+              new(ps);
+              ps^:=tsetconstnode(node).value_set^;
+              sym:=cconstsym.create_ptr(undefinedname,constset,ps,fromdef);
+              setdef:=tsetdef(tsetconstnode(node).resultdef);
+              prettyname:='[';
+              for i := setdef.setbase to setdef.setmax do
+                if i in tsetconstnode(node).value_set^ then
+                  begin
+                    if setdef.elementdef.typ=enumdef then
+                      enumsym:=tenumdef(setdef.elementdef).int2enumsym(i)
+                    else
+                      enumsym:=nil;
+                    if assigned(enumsym) then
+                      enumname:=enumsym.realname
+                    else if setdef.elementdef.typ=orddef then
+                      begin
+                        if torddef(setdef.elementdef).ordtype=uchar then
+                          enumname:=chr(i)
+                        else
+                          enumname:=tostr(i);
+                      end
+                    else
+                      enumname:=tostr(i);
+                    if length(prettyname) > 1 then
+                      prettyname:=prettyname+','+enumname
+                    else
+                      prettyname:=prettyname+enumname;
+                  end;
+              prettyname:=prettyname+']';
+            end;
+          niln:
+            begin
+              { only "nil" is available for pointer constants }
+              sym:=cconstsym.create_ord(undefinedname,constnil,0,fromdef);
+              prettyname:='nil';
+            end;
+          else
+            internalerror(2019021601);
+        end;
+        { the sym needs an owner for later checks so us the typeparam owner }
+        sym.owner:=fromdef.owner;
+        include(sym.symoptions,sp_generic_const);
+        result:=sym;
+      end;
 
     procedure maybe_add_waiting_unit(tt:tdef);
       var
@@ -104,203 +236,232 @@ uses
           end;
       end;
 
-    function check_generic_constraints(genericdef:tstoreddef;paradeflist:tfpobjectlist;poslist:tfplist):boolean;
+    function check_generic_constraints(genericdef:tstoreddef;paramlist:tfpobjectlist;poslist:tfplist):boolean;
       var
         i,j,
         intfcount : longint;
         formaldef,
         paradef : tstoreddef;
+        genparadef : tdef;
         objdef,
         paraobjdef,
         formalobjdef : tobjectdef;
         intffound : boolean;
         filepos : tfileposinfo;
+        //paratype : tconsttyp;
+        is_const : boolean;
       begin
         { check whether the given specialization parameters fit to the eventual
           constraints of the generic }
         if not assigned(genericdef.genericparas) or (genericdef.genericparas.count=0) then
           internalerror(2012101001);
-        if genericdef.genericparas.count<>paradeflist.count then
+        if genericdef.genericparas.count<>paramlist.count then
           internalerror(2012101002);
-        if paradeflist.count<>poslist.count then
+        if paramlist.count<>poslist.count then
           internalerror(2012120801);
         result:=true;
         for i:=0 to genericdef.genericparas.count-1 do
           begin
             filepos:=pfileposinfo(poslist[i])^;
-            formaldef:=tstoreddef(ttypesym(genericdef.genericparas[i]).typedef);
-            if formaldef.typ=undefineddef then
-              { the parameter is of unspecified type, so no need to check }
-              continue;
-            if not (df_genconstraint in formaldef.defoptions) or
-                not assigned(formaldef.genconstraintdata) then
-              internalerror(2013021602);
-            paradef:=tstoreddef(paradeflist[i]);
-            { undefineddef is compatible with anything }
-            if formaldef.typ=undefineddef then
-              continue;
-            if paradef.typ<>formaldef.typ then
+            paradef:=tstoreddef(get_generic_param_def(tsym(paramlist[i])));
+            is_const:=tsym(paramlist[i]).typ=constsym;
+            genparadef:=genericdef.get_generic_param_def(i);
+            { validate const params }
+            if not genericdef.is_generic_param_const(i) and is_const then
               begin
-                case formaldef.typ of
-                  recorddef:
-                    { delphi has own fantasy about record constraint
-                      (almost non-nullable/non-nilable value type) }
-                    if m_delphi in current_settings.modeswitches then
-                      case paradef.typ of
-                        floatdef,enumdef,orddef:
-                          continue;
-                        objectdef:
-                          if tobjectdef(paradef).objecttype=odt_object then
-                            continue
-                          else
-                            MessagePos(filepos,type_e_record_type_expected);
+                MessagePos(filepos,type_e_mismatch);
+                exit(false);
+              end
+            else if genericdef.is_generic_param_const(i) then
+              begin
+                { param type mismatch (type <> const) }
+                 if genericdef.is_generic_param_const(i) <> is_const then
+                   begin
+                    MessagePos(filepos,type_e_mismatch);
+                    exit(false);
+                  end;
+                { type constrained param doesn't match type }
+                if not compare_generic_params(paradef,genericdef.get_generic_param_def(i),tconstsym(paramlist[i])) then
+                  begin
+                    MessagePos2(filepos,type_e_incompatible_types,FullTypeName(paradef,genparadef),FullTypeName(genparadef,paradef));
+                    exit(false);
+                  end;
+              end;
+            { test constraints for non-const params }
+            if not genericdef.is_generic_param_const(i) then
+              begin
+                formaldef:=tstoreddef(ttypesym(genericdef.genericparas[i]).typedef);
+                if formaldef.typ=undefineddef then
+                  { the parameter is of unspecified type, so no need to check }
+                  continue;
+                if not (df_genconstraint in formaldef.defoptions) or
+                    not assigned(formaldef.genconstraintdata) then
+                  internalerror(2013021602);
+                { undefineddef is compatible with anything }
+                if formaldef.typ=undefineddef then
+                  continue;
+                if paradef.typ<>formaldef.typ then
+                  begin
+                    case formaldef.typ of
+                      recorddef:
+                        { delphi has own fantasy about record constraint
+                          (almost non-nullable/non-nilable value type) }
+                        if m_delphi in current_settings.modeswitches then
+                          case paradef.typ of
+                            floatdef,enumdef,orddef:
+                              continue;
+                            objectdef:
+                              if tobjectdef(paradef).objecttype=odt_object then
+                                continue
+                              else
+                                MessagePos(filepos,type_e_record_type_expected);
+                            else
+                              MessagePos(filepos,type_e_record_type_expected);
+                          end
                         else
                           MessagePos(filepos,type_e_record_type_expected);
-                      end
-                    else
-                      MessagePos(filepos,type_e_record_type_expected);
-                  objectdef:
-                    case tobjectdef(formaldef).objecttype of
-                      odt_class,
-                      odt_javaclass:
-                        MessagePos1(filepos,type_e_class_type_expected,paradef.typename);
-                      odt_interfacecom,
-                      odt_interfacecorba,
-                      odt_dispinterface,
-                      odt_interfacejava:
-                        MessagePos1(filepos,type_e_interface_type_expected,paradef.typename);
+                      objectdef:
+                        case tobjectdef(formaldef).objecttype of
+                          odt_class,
+                          odt_javaclass:
+                            MessagePos1(filepos,type_e_class_type_expected,paradef.typename);
+                          odt_interfacecom,
+                          odt_interfacecorba,
+                          odt_dispinterface,
+                          odt_interfacejava:
+                            MessagePos1(filepos,type_e_interface_type_expected,paradef.typename);
+                          else
+                            internalerror(2012101003);
+                        end;
+                      errordef:
+                        { ignore }
+                        ;
                       else
-                        internalerror(2012101003);
+                        internalerror(2012101004);
                     end;
-                  errordef:
-                    { ignore }
-                    ;
-                  else
-                    internalerror(2012101004);
-                end;
-                result:=false;
-              end
-            else
-              begin
-                { the paradef types are the same, so do special checks for the
-                  cases in which they are needed }
-                if formaldef.typ=objectdef then
+                    result:=false;
+                  end
+                else
                   begin
-                    paraobjdef:=tobjectdef(paradef);
-                    formalobjdef:=tobjectdef(formaldef);
-                    if not (formalobjdef.objecttype in [odt_class,odt_javaclass,odt_interfacecom,odt_interfacecorba,odt_interfacejava,odt_dispinterface]) then
-                      internalerror(2012101102);
-                    if formalobjdef.objecttype in [odt_interfacecom,odt_interfacecorba,odt_interfacejava,odt_dispinterface] then
+                    { the paradef types are the same, so do special checks for the
+                      cases in which they are needed }
+                    if formaldef.typ=objectdef then
                       begin
-                        { this is either a concerete interface or class type (the
-                          latter without specific implemented interfaces) }
-                        case paraobjdef.objecttype of
-                          odt_interfacecom,
-                          odt_interfacecorba,
-                          odt_interfacejava,
-                          odt_dispinterface:
-                            begin
-                              if (oo_is_forward in paraobjdef.objectoptions) and
-                                  (paraobjdef.objecttype=formalobjdef.objecttype) and
-                                  (df_genconstraint in formalobjdef.defoptions) and
-                                  (
-                                    (formalobjdef.objecttype=odt_interfacecom) and
-                                    (formalobjdef.childof=interface_iunknown)
-                                  )
-                                  or
-                                  (
-                                    (formalobjdef.objecttype=odt_interfacecorba) and
-                                    (formalobjdef.childof=nil)
-                                  ) then
-                                continue;
-                              if not def_is_related(paraobjdef,formalobjdef.childof) then
+                        paraobjdef:=tobjectdef(paradef);
+                        formalobjdef:=tobjectdef(formaldef);
+                        if not (formalobjdef.objecttype in [odt_class,odt_javaclass,odt_interfacecom,odt_interfacecorba,odt_interfacejava,odt_dispinterface]) then
+                          internalerror(2012101102);
+                        if formalobjdef.objecttype in [odt_interfacecom,odt_interfacecorba,odt_interfacejava,odt_dispinterface] then
+                          begin
+                            { this is either a concerete interface or class type (the
+                              latter without specific implemented interfaces) }
+                            case paraobjdef.objecttype of
+                              odt_interfacecom,
+                              odt_interfacecorba,
+                              odt_interfacejava,
+                              odt_dispinterface:
                                 begin
-                                  MessagePos2(filepos,type_e_incompatible_types,paraobjdef.typename,formalobjdef.childof.typename);
-                                  result:=false;
+                                  if (oo_is_forward in paraobjdef.objectoptions) and
+                                      (paraobjdef.objecttype=formalobjdef.objecttype) and
+                                      (df_genconstraint in formalobjdef.defoptions) and
+                                      (
+                                        (formalobjdef.objecttype=odt_interfacecom) and
+                                        (formalobjdef.childof=interface_iunknown)
+                                      )
+                                      or
+                                      (
+                                        (formalobjdef.objecttype=odt_interfacecorba) and
+                                        (formalobjdef.childof=nil)
+                                      ) then
+                                    continue;
+                                  if not def_is_related(paraobjdef,formalobjdef.childof) then
+                                    begin
+                                      MessagePos2(filepos,type_e_incompatible_types,paraobjdef.typename,formalobjdef.childof.typename);
+                                      result:=false;
+                                    end;
                                 end;
-                            end;
-                          odt_class,
-                          odt_javaclass:
-                            begin
-                              objdef:=paraobjdef;
-                              intffound:=false;
-                              while assigned(objdef) do
+                              odt_class,
+                              odt_javaclass:
                                 begin
-                                  for j:=0 to objdef.implementedinterfaces.count-1 do
-                                    if timplementedinterface(objdef.implementedinterfaces[j]).intfdef=formalobjdef.childof then
-                                      begin
-                                        intffound:=true;
+                                  objdef:=paraobjdef;
+                                  intffound:=false;
+                                  while assigned(objdef) do
+                                    begin
+                                      for j:=0 to objdef.implementedinterfaces.count-1 do
+                                        if timplementedinterface(objdef.implementedinterfaces[j]).intfdef=formalobjdef.childof then
+                                          begin
+                                            intffound:=true;
+                                            break;
+                                          end;
+                                      if intffound then
                                         break;
-                                      end;
-                                  if intffound then
-                                    break;
-                                  objdef:=objdef.childof;
+                                      objdef:=objdef.childof;
+                                    end;
+                                  result:=intffound;
+                                  if not result then
+                                    MessagePos2(filepos,parser_e_class_doesnt_implement_interface,paraobjdef.typename,formalobjdef.childof.typename);
+                                end;
+                              else
+                                begin
+                                  MessagePos1(filepos,type_e_class_or_interface_type_expected,paraobjdef.typename);
+                                  result:=false;
                                 end;
-                              result:=intffound;
-                              if not result then
-                                MessagePos2(filepos,parser_e_class_doesnt_implement_interface,paraobjdef.typename,formalobjdef.childof.typename);
-                            end;
-                          else
-                            begin
-                              MessagePos1(filepos,type_e_class_or_interface_type_expected,paraobjdef.typename);
-                              result:=false;
                             end;
-                        end;
-                      end
-                    else
-                      begin
-                        { this is either a "class" or a concrete instance with
-                          or without implemented interfaces }
-                        if not (paraobjdef.objecttype in [odt_class,odt_javaclass]) then
-                          begin
-                            MessagePos1(filepos,type_e_class_type_expected,paraobjdef.typename);
-                            result:=false;
-                            continue;
-                          end;
-                        { for forward declared classes we allow pure TObject/class declarations }
-                        if (oo_is_forward in paraobjdef.objectoptions) and
-                            (df_genconstraint in formaldef.defoptions) then
-                          begin
-                            if (formalobjdef.childof=class_tobject) and
-                                not formalobjdef.implements_any_interfaces then
-                              continue;
-                          end;
-                        if assigned(formalobjdef.childof) and
-                            not def_is_related(paradef,formalobjdef.childof) then
-                          begin
-                            MessagePos2(filepos,type_e_incompatible_types,paraobjdef.typename,formalobjdef.childof.typename);
-                            result:=false;
-                          end;
-                        intfcount:=0;
-                        for j:=0 to formalobjdef.implementedinterfaces.count-1 do
+                          end
+                        else
                           begin
-                            objdef:=paraobjdef;
-                            while assigned(objdef) do
+                            { this is either a "class" or a concrete instance with
+                              or without implemented interfaces }
+                            if not (paraobjdef.objecttype in [odt_class,odt_javaclass]) then
+                              begin
+                                MessagePos1(filepos,type_e_class_type_expected,paraobjdef.typename);
+                                result:=false;
+                                continue;
+                              end;
+                            { for forward declared classes we allow pure TObject/class declarations }
+                            if (oo_is_forward in paraobjdef.objectoptions) and
+                                (df_genconstraint in formaldef.defoptions) then
+                              begin
+                                if (formalobjdef.childof=class_tobject) and
+                                    not formalobjdef.implements_any_interfaces then
+                                  continue;
+                              end;
+                            if assigned(formalobjdef.childof) and
+                                not def_is_related(paradef,formalobjdef.childof) then
                               begin
-                                intffound:=assigned(
-                                             find_implemented_interface(objdef,
-                                               timplementedinterface(formalobjdef.implementedinterfaces[j]).intfdef
-                                             )
-                                           );
+                                MessagePos2(filepos,type_e_incompatible_types,paraobjdef.typename,formalobjdef.childof.typename);
+                                result:=false;
+                              end;
+                            intfcount:=0;
+                            for j:=0 to formalobjdef.implementedinterfaces.count-1 do
+                              begin
+                                objdef:=paraobjdef;
+                                while assigned(objdef) do
+                                  begin
+                                    intffound:=assigned(
+                                                 find_implemented_interface(objdef,
+                                                   timplementedinterface(formalobjdef.implementedinterfaces[j]).intfdef
+                                                 )
+                                               );
+                                    if intffound then
+                                      break;
+                                    objdef:=objdef.childof;
+                                  end;
                                 if intffound then
-                                  break;
-                                objdef:=objdef.childof;
+                                  inc(intfcount)
+                                else
+                                  MessagePos2(filepos,parser_e_class_doesnt_implement_interface,paraobjdef.typename,timplementedinterface(formalobjdef.implementedinterfaces[j]).intfdef.typename);
                               end;
-                            if intffound then
-                              inc(intfcount)
-                            else
-                              MessagePos2(filepos,parser_e_class_doesnt_implement_interface,paraobjdef.typename,timplementedinterface(formalobjdef.implementedinterfaces[j]).intfdef.typename);
+                            if intfcount<>formalobjdef.implementedinterfaces.count then
+                              result:=false;
                           end;
-                        if intfcount<>formalobjdef.implementedinterfaces.count then
-                          result:=false;
                       end;
                   end;
               end;
           end;
       end;
 
-
-    function parse_generic_specialization_types_internal(genericdeflist:tfpobjectlist;poslist:tfplist;out prettyname,specializename:ansistring;parsedtype:tdef;parsedpos:tfileposinfo):boolean;
+    function parse_generic_specialization_types_internal(paramlist:tfpobjectlist;poslist:tfplist;out prettyname,specializename:ansistring;parsedtype:tdef;parsedpos:tfileposinfo):boolean;
       var
         old_block_type : tblock_type;
         first : boolean;
@@ -310,9 +471,12 @@ uses
         namepart : string;
         prettynamepart : ansistring;
         module : tmodule;
+        //paramdef : tgenericparamdef;
+        constprettyname : string;
+        validparam : boolean;
       begin
         result:=true;
-        if genericdeflist=nil then
+        if paramlist=nil then
           internalerror(2012061401);
         { set the block type to type, so that the parsed type are returned as
           ttypenode (e.g. classes are in non type-compatible blocks returned as
@@ -324,7 +488,7 @@ uses
         first:=not assigned(parsedtype);
         if assigned(parsedtype) then
           begin
-            genericdeflist.Add(parsedtype);
+            paramlist.Add(parsedtype.typesym);
             module:=find_module_from_symtable(parsedtype.owner);
             if not assigned(module) then
               internalerror(2016112801);
@@ -350,8 +514,10 @@ uses
               consume(_COMMA);
             block_type:=bt_type;
             tmpparampos:=current_filepos;
-            typeparam:=factor(false,[ef_type_only]);
-            if typeparam.nodetype=typen then
+            typeparam:=factor(false,[ef_accept_equal]);
+            { determine if the typeparam node is a valid type or const }
+            validparam:=typeparam.nodetype in tgeneric_param_nodes;
+            if validparam then
               begin
                 if tstoreddef(typeparam.resultdef).is_generic and
                     (
@@ -367,31 +533,47 @@ uses
                   end;
                 if typeparam.resultdef.typ<>errordef then
                   begin
-                    if not assigned(typeparam.resultdef.typesym) then
+                    if (typeparam.nodetype = typen) and not assigned(typeparam.resultdef.typesym) then
                       message(type_e_generics_cannot_reference_itself)
-                    else if (typeparam.resultdef.typ<>errordef) then
+                    else 
+                    if (typeparam.resultdef.typ<>errordef) then
                       begin
-                        genericdeflist.Add(typeparam.resultdef);
+                        { all non-type nodes are considered const }
+                        if typeparam.nodetype<>typen then
+                          paramlist.Add(create_generic_constsym(typeparam.resultdef,typeparam,constprettyname))
+                        else
+                          begin
+                            constprettyname:='';
+                            paramlist.Add(typeparam.resultdef.typesym);
+                          end;
                         module:=find_module_from_symtable(typeparam.resultdef.owner);
                         if not assigned(module) then
                           internalerror(2016112802);
                         namepart:='_$'+hexstr(module.moduleid,8)+'$$'+typeparam.resultdef.unique_id_str;
+                        if constprettyname <> '' then
+                          namepart:=namepart+'$$'+constprettyname;
                         { we use the full name of the type to uniquely identify it }
-                        if (symtablestack.top.symtabletype=parasymtable) and
-                            (symtablestack.top.defowner.typ=procdef) and
-                            (typeparam.resultdef.owner=symtablestack.top) then
-                          begin
-                            { special handling for specializations inside generic function declarations }
-                            prettynamepart:=tdef(symtablestack.top.defowner).fullownerhierarchyname(true)+tprocdef(symtablestack.top.defowner).procsym.prettyname;
-                          end
-                        else
+                        if typeparam.nodetype = typen then
                           begin
-                            prettynamepart:=typeparam.resultdef.fullownerhierarchyname(true);
+                            if (symtablestack.top.symtabletype=parasymtable) and
+                                (symtablestack.top.defowner.typ=procdef) and
+                                (typeparam.resultdef.owner=symtablestack.top) then
+                              begin
+                                { special handling for specializations inside generic function declarations }
+                                prettynamepart:=tdef(symtablestack.top.defowner).fullownerhierarchyname(true)+tprocdef(symtablestack.top.defowner).procsym.prettyname;
+                              end
+                            else
+                              begin
+                                prettynamepart:=typeparam.resultdef.fullownerhierarchyname(true);
+                              end;
                           end;
                         specializename:=specializename+namepart;
                         if not first then
                           prettyname:=prettyname+',';
-                        prettyname:=prettyname+prettynamepart+typeparam.resultdef.typesym.prettyname;
+                        if constprettyname <> '' then
+                          prettyname:=prettyname+constprettyname
+                        else
+                          prettyname:=prettyname+prettynamepart+typeparam.resultdef.typesym.prettyname;
                       end;
                   end
                 else
@@ -411,12 +593,12 @@ uses
       end;
 
 
-    function parse_generic_specialization_types(genericdeflist:tfpobjectlist;poslist:tfplist;out prettyname,specializename:ansistring):boolean;
+    function parse_generic_specialization_types(paramlist:tfpobjectlist;poslist:tfplist;out prettyname,specializename:ansistring):boolean;
       var
         dummypos : tfileposinfo;
       begin
         FillChar(dummypos, SizeOf(tfileposinfo), 0);
-        result:=parse_generic_specialization_types_internal(genericdeflist,poslist,prettyname,specializename,nil,dummypos);
+        result:=parse_generic_specialization_types_internal(paramlist,poslist,prettyname,specializename,nil,dummypos);
       end;
 
 
@@ -507,7 +689,7 @@ uses
         context:=tspecializationcontext.create;
 
         { Parse type parameters }
-        err:=not parse_generic_specialization_types_internal(context.genericdeflist,context.poslist,context.prettyname,context.specializename,parsedtype,parsedpos);
+        err:=not parse_generic_specialization_types_internal(context.paramlist,context.poslist,context.prettyname,context.specializename,parsedtype,parsedpos);
         if err then
           begin
             if not try_to_consume(_GT) then
@@ -561,7 +743,7 @@ uses
 
         { search a generic with the given count of params }
         countstr:='';
-        str(context.genericdeflist.Count,countstr);
+        str(context.paramlist.Count,countstr);
 
         genname:=genname+'$'+countstr;
         ugenname:=upper(genname);
@@ -612,7 +794,7 @@ uses
             result:=generrordef;
             exit;
           end;
-
+        
         { we've found the correct def }
         if context.sym.typ=typesym then
           result:=tstoreddef(ttypesym(context.sym).typedef)
@@ -705,6 +887,7 @@ uses
         hintsprocessed : boolean;
         pd : tprocdef;
         pdflags : tpdflags;
+        typedef : tstoreddef;
       begin
         if not assigned(context) then
           internalerror(2015052203);
@@ -713,7 +896,7 @@ uses
 
         pd:=nil;
 
-        if not check_generic_constraints(genericdef,context.genericdeflist,context.poslist) then
+        if not check_generic_constraints(genericdef,context.paramlist,context.poslist) then
           begin
             { the parameters didn't fit the constraints, so don't continue with the
               specialization }
@@ -729,20 +912,19 @@ uses
         else
           prettyname:=genericdef.typesym.prettyname;
         prettyname:=prettyname+'<'+context.prettyname+'>';
-
         generictypelist:=tfphashobjectlist.create(false);
 
         { build the list containing the types for the generic params }
         if not assigned(genericdef.genericparas) then
           internalerror(2013092601);
-        if context.genericdeflist.count<>genericdef.genericparas.count then
+        if context.paramlist.count<>genericdef.genericparas.count then
           internalerror(2013092603);
         for i:=0 to genericdef.genericparas.Count-1 do
           begin
             srsym:=tsym(genericdef.genericparas[i]);
             if not (sp_generic_para in srsym.symoptions) then
               internalerror(2013092602);
-            generictypelist.add(srsym.realname,tdef(context.genericdeflist[i]).typesym);
+            generictypelist.add(srsym.realname,context.paramlist[i]);
           end;
 
         { Special case if we are referencing the current defined object }
@@ -1164,8 +1346,8 @@ uses
 
     function parse_generic_parameters(allowconstraints:boolean):tfphashobjectlist;
       var
-        generictype : ttypesym;
-        i,firstidx : longint;
+        generictype : tstoredsym;
+        i,firstidx,const_list_index : longint;
         srsymtable : tsymtable;
         basedef,def : tdef;
         defname : tidstring;
@@ -1173,22 +1355,91 @@ uses
         doconsume : boolean;
         constraintdata : tgenericconstraintdata;
         old_block_type : tblock_type;
+        is_const,last_is_const : boolean;
+        last_token : ttoken;
+        last_type_pos : tfileposinfo;
       begin
         result:=tfphashobjectlist.create(false);
         firstidx:=0;
+        const_list_index:=0;
         old_block_type:=block_type;
         block_type:=bt_type;
+        is_const:=false;
+        last_is_const:=false;
+        last_token:=NOTOKEN;
+        last_type_pos:=current_filepos;
         repeat
+          if try_to_consume(_CONST) then
+            begin
+              { last param was const without semicolon terminator }
+              if (result.count>0) and last_is_const and (last_token<>_SEMICOLON) then
+                MessagePos2(last_type_pos,scan_f_syn_expected,arraytokeninfo[_SEMICOLON].str,arraytokeninfo[last_token].str);
+              is_const:=true;
+              const_list_index:=result.count;
+            end;
           if token=_ID then
             begin
-              generictype:=ctypesym.create(orgpattern,cundefinedtype);
+              if is_const then
+                begin
+                  { last param was type without semicolon terminator }
+                  if (result.count>0) and not last_is_const and (last_token<>_SEMICOLON) then
+                    MessagePos2(last_type_pos,scan_f_syn_expected,arraytokeninfo[_SEMICOLON].str,arraytokeninfo[last_token].str);
+                  generictype:=cconstsym.create_undefined(orgpattern,cundefinedtype);
+                end
+              else
+                begin
+                  { last param was const without semicolon terminator }
+                  if (result.count>0) and last_is_const and (last_token<>_SEMICOLON) then
+                    MessagePos2(last_type_pos,scan_f_syn_expected,arraytokeninfo[_SEMICOLON].str,arraytokeninfo[last_token].str);
+                  generictype:=ctypesym.create(orgpattern,cundefinedtype);
+                end;
               { type parameters need to be added as strict private }
               generictype.visibility:=vis_strictprivate;
               include(generictype.symoptions,sp_generic_para);
               result.add(orgpattern,generictype);
+              last_is_const:=is_const;
             end;
           consume(_ID);
-          if try_to_consume(_COLON) then
+          { const restriction }
+          if is_const then
+            begin
+              if try_to_consume(_COLON) then
+                begin
+                  def := nil;
+                  { parse the type and assign the const type to generictype  }
+                  single_type(def,[]);
+                  for i:=const_list_index to result.count-1 do
+                    begin
+                      { finalize constant information once type is known }
+                      if assigned(def) and (def.typ in tgeneric_param_const_types) then
+                        begin
+                          case def.typ of
+                            orddef,
+                            enumdef:
+                              tconstsym(result[i]).consttyp:=constord;
+                            stringdef:
+                              tconstsym(result[i]).consttyp:=conststring;
+                            floatdef:
+                              tconstsym(result[i]).consttyp:=constreal;
+                            setdef:
+                              tconstsym(result[i]).consttyp:=constset;
+                            { pointer always refers to nil with constants }
+                            pointerdef:
+                              tconstsym(result[i]).consttyp:=constnil;
+                            else
+                              internalerror(2020011402);
+                          end;
+                          tconstsym(result[i]).constdef:=def;
+                        end
+                      else
+                        Message(type_e_mismatch);
+                    end;
+                  { after type restriction const list terminates }
+                  is_const:=false;
+                end;
+            end
+          { type restriction }
+          else if try_to_consume(_COLON) then
             begin
               if not allowconstraints then
                 { TODO }
@@ -1305,6 +1556,7 @@ uses
                     basedef:=cobjectdef.create(tobjectdef(def).objecttype,defname,tobjectdef(def),false);
                     constraintdata.interfaces.delete(0);
                   end;
+
               if basedef.typ<>errordef then
                 with tstoreddef(basedef) do
                   begin
@@ -1330,21 +1582,31 @@ uses
                 begin
                   { two different typeless parameters are considered as incompatible }
                   for i:=firstidx to result.count-1 do
-                    begin
-                      ttypesym(result[i]).typedef:=cundefineddef.create(false);
-                      ttypesym(result[i]).typedef.typesym:=ttypesym(result[i]);
-                    end;
+                    if tsym(result[i]).typ<>constsym then
+                      begin
+                        ttypesym(result[i]).typedef:=cundefineddef.create(false);
+                        ttypesym(result[i]).typedef.typesym:=ttypesym(result[i]);
+                      end;
                   { a semicolon terminates a type parameter group }
                   firstidx:=result.count;
                 end;
             end;
+          if token = _SEMICOLON then
+            is_const:=false;
+          last_token:=token;
+          last_type_pos:=current_filepos;
         until not (try_to_consume(_COMMA) or try_to_consume(_SEMICOLON));
+        { if the constant parameter is not terminated then the type restriction was 
+          not specified and we need to give an error }
+        if is_const then
+          consume(_COLON);
         { two different typeless parameters are considered as incompatible }
         for i:=firstidx to result.count-1 do
-          begin
-            ttypesym(result[i]).typedef:=cundefineddef.create(false);
-            ttypesym(result[i]).typedef.typesym:=ttypesym(result[i]);
-          end;
+          if tsym(result[i]).typ<>constsym then
+            begin
+              ttypesym(result[i]).typedef:=cundefineddef.create(false);
+              ttypesym(result[i]).typedef.typesym:=ttypesym(result[i]);
+            end;
         block_type:=old_block_type;
       end;
 
@@ -1352,7 +1614,9 @@ uses
     procedure insert_generic_parameter_types(def:tstoreddef;genericdef:tstoreddef;genericlist:tfphashobjectlist);
       var
         i : longint;
-        generictype,sym : ttypesym;
+        generictype : tstoredsym;
+        generictypedef : tdef;
+        sym : tsym;
         st : tsymtable;
       begin
         def.genericdef:=genericdef;
@@ -1377,10 +1641,23 @@ uses
           def.genericparas:=tfphashobjectlist.create(false);
         for i:=0 to genericlist.count-1 do
           begin
-            generictype:=ttypesym(genericlist[i]);
+            generictype:=tstoredsym(genericlist[i]);
             if assigned(generictype.owner) then
               begin
-                sym:=ctypesym.create(genericlist.nameofindex(i),generictype.typedef);
+                if generictype.typ=typesym then
+                  sym:=ctypesym.create(genericlist.nameofindex(i),ttypesym(generictype).typedef)
+                else if generictype.typ=constsym then
+                  { generictype is a constsym that was created in create_generic_constsym 
+                    during phase 1 so we pass this directly without copying }
+                  begin
+                    sym:=generictype;
+                    { the sym name is still undefined so we set it to match
+                      the generic param name so it's accessible }
+                    sym.realname:=genericlist.nameofindex(i);
+                    include(sym.symoptions,sp_generic_const);
+                  end
+                else
+                  internalerror(2019021602);
                 { type parameters need to be added as strict private }
                 sym.visibility:=vis_strictprivate;
                 st.insert(sym);
@@ -1388,13 +1665,17 @@ uses
               end
             else
               begin
-                if (generictype.typedef.typ=undefineddef) and (generictype.typedef<>cundefinedtype) then
+                if generictype.typ=typesym then
                   begin
-                    { the generic parameters were parsed before the genericdef existed thus the
-                      undefineddefs were added as part of the parent symtable }
-                    if assigned(generictype.typedef.owner) then
-                      generictype.typedef.owner.DefList.Extract(generictype.typedef);
-                    generictype.typedef.changeowner(st);
+                    generictypedef:=ttypesym(generictype).typedef;
+                    if (generictypedef.typ=undefineddef) and (generictypedef<>cundefinedtype) then
+                      begin
+                        { the generic parameters were parsed before the genericdef existed thus the
+                          undefineddefs were added as part of the parent symtable }
+                        if assigned(generictypedef.owner) then
+                          generictypedef.owner.DefList.Extract(generictypedef);
+                        generictypedef.changeowner(st);
+                      end;
                   end;
                 st.insert(generictype);
                 include(generictype.symoptions,sp_generic_para);
diff --git a/compiler/pstatmnt.pas b/compiler/pstatmnt.pas
index e62d164f74..9bf65d6713 100644
--- a/compiler/pstatmnt.pas
+++ b/compiler/pstatmnt.pas
@@ -361,7 +361,9 @@ implementation
         procedure check_range(hp:tnode; fordef: tdef);
           begin
             if (hp.nodetype=ordconstn) and
-               (fordef.typ<>errordef) then
+               (fordef.typ<>errordef) and
+               { the node was derived from a generic parameter so ignore range check }
+               not(nf_generic_para in hp.flags) then
               adaptrange(fordef,tordconstnode(hp).value,false,false,true);
           end;
 
diff --git a/compiler/ptype.pas b/compiler/ptype.pas
index ab3db2b048..4498af68a6 100644
--- a/compiler/ptype.pas
+++ b/compiler/ptype.pas
@@ -1446,7 +1446,9 @@ implementation
                                  highval:=tordconstnode(trangenode(pt).right).value;
                                  if highval<lowval then
                                   begin
-                                    Message(parser_e_array_lower_less_than_upper_bound);
+                                    { ignore error if node is generic param }
+                                    if not (nf_generic_para in pt.flags) then
+                                      Message(parser_e_array_lower_less_than_upper_bound);
                                     highval:=lowval;
                                   end
                                  else if (lowval<int64(low(asizeint))) or
diff --git a/compiler/symconst.pas b/compiler/symconst.pas
index 130fda9049..defbdce338 100644
--- a/compiler/symconst.pas
+++ b/compiler/symconst.pas
@@ -205,8 +205,9 @@ type
                               generic is encountered to ease inline
                               specializations, etc; those symbols can be
                               "overridden" with a completely different symbol }
-    sp_explicitrename       { this is used to keep track of type renames created
+    sp_explicitrename,      { this is used to keep track of type renames created
                               by the user }
+    sp_generic_const
   );
   tsymoptions=set of tsymoption;
 
@@ -234,7 +235,10 @@ type
     { internal def that's not for any export }
     df_internal,
     { the local def is referenced from a public function }
-    df_has_global_ref
+    df_has_global_ref,
+    { the def was derived with generic type or const fields so the size
+      of the def can not be determined }
+    df_has_generic_fields
   );
   tdefoptions=set of tdefoption;
 
@@ -681,7 +685,7 @@ type
     arraydef,recorddef,pointerdef,orddef,
     stringdef,enumdef,procdef,objectdef,errordef,
     filedef,formaldef,setdef,procvardef,floatdef,
-    classrefdef,forwarddef,variantdef,undefineddef
+    classrefdef,forwarddef,variantdef,genericconstdef,undefineddef
   );
 
   { possible types for symtable entries }
@@ -877,7 +881,7 @@ inherited_objectoptions : tobjectoptions = [oo_has_virtual,oo_has_private,oo_has
        'abstractdef','arraydef','recorddef','pointerdef','orddef',
        'stringdef','enumdef','procdef','objectdef','errordef',
        'filedef','formaldef','setdef','procvardef','floatdef',
-       'classrefdef','forwarddef','variantdef','undefineddef'
+       'classrefdef','forwarddef','variantdef','genconstdef','undefineddef'
      );
 
      EqualTypeName : array[tequaltype] of string[16] = (
diff --git a/compiler/symdef.pas b/compiler/symdef.pas
index 0d2653edb3..489fe2a22d 100644
--- a/compiler/symdef.pas
+++ b/compiler/symdef.pas
@@ -173,6 +173,9 @@ interface
           function is_generic:boolean;
           { same as above for specializations }
           function is_specialization:boolean;
+          { generic utilities }
+          function is_generic_param_const(index:integer):boolean;inline;
+          function get_generic_param_def(index:integer):tdef;inline;
           { registers this def in the unit's deflist; no-op if already registered }
           procedure register_def; override;
           { add the def to the top of the symtable stack if it's not yet owned
@@ -2396,13 +2399,26 @@ implementation
          for i:=0 to genericparas.count-1 do
            begin
              sym:=tsym(genericparas[i]);
-             if sym.typ<>symconst.typesym then
+             { sym must be either a type or const }
+             if not (sym.typ in [symconst.typesym,symconst.constsym]) then
                internalerror(2014050903);
              if sym.owner.defowner<>self then
                exit(false);
            end;
      end;
 
+   function tstoreddef.is_generic_param_const(index:integer):boolean;
+     begin
+       result := tsym(genericparas[index]).typ=constsym;
+     end;  
+
+   function tstoreddef.get_generic_param_def(index:integer):tdef;
+     begin
+       if tsym(genericparas[index]).typ=constsym then
+         result := tconstsym(genericparas[index]).constdef
+       else
+         result := ttypesym(genericparas[index]).typedef;
+     end;
 
    function tstoreddef.is_specialization: boolean;
      var
@@ -2419,12 +2435,12 @@ implementation
            for i:=0 to genericparas.count-1 do
              begin
                sym:=tsym(genericparas[i]);
-               if sym.typ<>symconst.typesym then
+               { sym must be either a type or const }
+               if not (sym.typ in [symconst.typesym,symconst.constsym]) then
                  internalerror(2014050904);
                if sym.owner.defowner<>self then
                  exit(true);
              end;
-           result:=false;
          end;
      end;
 
diff --git a/compiler/symsym.pas b/compiler/symsym.pas
index 30f6a10f14..3b23cd56c4 100644
--- a/compiler/symsym.pas
+++ b/compiler/symsym.pas
@@ -164,7 +164,7 @@ interface
           fprettyname : ansistring;
           constructor create(const n : string;def:tdef);virtual;
           destructor destroy;override;
-          constructor ppuload(ppufile:tcompilerppufile);
+          constructor ppuload(ppufile:tcompilerppufile);virtual;
           { do not override this routine in platform-specific subclasses,
             override ppuwrite_platform instead }
           procedure ppuwrite(ppufile:tcompilerppufile);override;final;
@@ -401,6 +401,7 @@ interface
           constructor create_ptr(const n : string;t : tconsttyp;v : pointer;def:tdef);virtual;
           constructor create_string(const n : string;t : tconsttyp;str:pchar;l:longint;def:tdef);virtual;
           constructor create_wstring(const n : string;t : tconsttyp;pw:pcompilerwidestring);virtual;
+          constructor create_undefined(const n : string;def: tdef);
           constructor ppuload(ppufile:tcompilerppufile);
           destructor  destroy;override;
           procedure buildderef;override;
@@ -1618,7 +1619,6 @@ implementation
           tparasymtable(parast).ppuwrite(ppufile);
       end;
 
-
 {****************************************************************************
                             TABSTRACTVARSYM
 ****************************************************************************}
@@ -2424,7 +2424,14 @@ implementation
          constdefderef.reset;
          value.len:=getlengthwidestring(pw);
       end;
-
+    
+    constructor tconstsym.create_undefined(const n : string;def: tdef);
+      begin
+        inherited create(constsym,n);
+        fillchar(value, sizeof(value), #0);
+        consttyp:=constnone;
+        constdef:=def;
+      end;
 
     constructor tconstsym.ppuload(ppufile:tcompilerppufile);
       var
@@ -2497,7 +2504,7 @@ implementation
                new(pguid(value.valueptr));
                ppufile.getdata(value.valueptr^,sizeof(tguid));
              end;
-           constnil :
+           constnil:
              ppufile.getderef(constdefderef);
            else
              Message1(unit_f_ppu_invalid_entry,tostr(ord(consttyp)));
@@ -2563,7 +2570,7 @@ implementation
          inherited ppuwrite(ppufile);
          ppufile.putbyte(byte(consttyp));
          case consttyp of
-           constnil :
+           constnil:
              ppufile.putderef(constdefderef);
            constord :
              begin
@@ -2716,7 +2723,6 @@ implementation
           result:=inherited prettyname;
       end;
 
-
 {****************************************************************************
                                   TSYSSYM
 ****************************************************************************}
diff --git a/compiler/symtable.pas b/compiler/symtable.pas
index 753c481109..4abbac76fe 100644
--- a/compiler/symtable.pas
+++ b/compiler/symtable.pas
@@ -2924,7 +2924,7 @@ implementation
 
     function generate_objectpascal_helper_key(def:tdef):string;
       begin
-        if not assigned(def) then
+        if not assigned(def) or (def.typ = errordef) then
           internalerror(2013020501);
         if def.typ in [recorddef,objectdef] then
           result:=make_mangledname('',tabstractrecorddef(def).symtable,'')
diff --git a/compiler/utils/ppuutils/ppudump.pp b/compiler/utils/ppuutils/ppudump.pp
index 916592f5ee..417e9169ce 100644
--- a/compiler/utils/ppuutils/ppudump.pp
+++ b/compiler/utils/ppuutils/ppudump.pp
@@ -1674,7 +1674,8 @@ const
      (mask:sp_generic_para;       str:'Generic Parameter'),
      (mask:sp_has_deprecated_msg; str:'Has Deprecated Message'),
      (mask:sp_generic_dummy;      str:'Generic Dummy'),
-     (mask:sp_explicitrename;     str:'Explicit Rename')
+     (mask:sp_explicitrename;     str:'Explicit Rename'),
+     (mask:sp_generic_const;      str:'Generic Constant Parameter')
   );
 var
   symoptions : tsymoptions;
@@ -2730,7 +2731,8 @@ const
      (mask:df_not_registered_no_free;  str:'Unregistered/No free (invalid)'),
      (mask:df_llvm_no_struct_packing;  str:'LLVM unpacked struct'),
      (mask:df_internal;       str:'Internal'),
-     (mask:df_has_global_ref; str:'Has Global Ref')
+     (mask:df_has_global_ref; str:'Has Global Ref'),
+     (mask:df_has_generic_fields; str:'Has generic fields')
   );
   defstate : array[1..ord(high(tdefstate))] of tdefstateinfo=(
      (mask:ds_vmt_written;           str:'VMT Written'),
diff --git a/tests/test/tgenconst1.pp b/tests/test/tgenconst1.pp
new file mode 100644
index 0000000000..4b2c455126
--- /dev/null
+++ b/tests/test/tgenconst1.pp
@@ -0,0 +1,38 @@
+{$mode objfpc}
+{
+	test all possible constants
+}
+program tgenconst1;
+
+type
+	TEnums = (Blaise, Pascal);
+	kNames = set of TEnums;
+	kChars = set of char;
+ 
+type
+	generic TBoolean<const U: boolean> = record end;
+	generic TString<const U: string> = record end;
+	generic TFloat<const U: single> = record end;
+	generic TInteger<const U: integer> = record end;
+	generic TChar<const U: char> = record end;
+	generic TByte<const U: byte> = record end;
+	generic TQWord<const U: QWord> = record end;
+	generic TEnum<const U: TEnums> = record end;
+	generic TNames<const U: kNames> = record end;
+	generic TChars<const U: kChars> = record end;
+	generic TPointer<const U: pointer> = record end;
+
+var
+	a: specialize TBoolean<true>;
+	b: specialize TString<'string'>;
+	c: specialize TFloat<1>;
+	d: specialize TInteger<10>;
+	e: specialize TByte<255>;
+	f: specialize TChar<'a'>;
+	g: specialize TEnum<Pascal>;
+	h: specialize TNames<[Blaise,Pascal]>;
+	i: specialize TChars<['a','b']>;
+	j: specialize TQWord<10>;
+	k: specialize TPointer<nil>;
+begin
+end.
diff --git a/tests/test/tgenconst10.pp b/tests/test/tgenconst10.pp
new file mode 100644
index 0000000000..eecb0bf162
--- /dev/null
+++ b/tests/test/tgenconst10.pp
@@ -0,0 +1,14 @@
+{%FAIL}
+{$mode objfpc}
+{
+  test type mismatch when specializing generic type with constant value
+}
+program tgenconst10;
+
+type
+	generic TByte<T> = record end;
+	
+var
+	a: specialize TByte<10>;
+begin
+end.
diff --git a/tests/test/tgenconst11.pp b/tests/test/tgenconst11.pp
new file mode 100644
index 0000000000..5895fd00c7
--- /dev/null
+++ b/tests/test/tgenconst11.pp
@@ -0,0 +1,13 @@
+{%FAIL}
+{$mode objfpc}
+{
+	test def compare fail with specialized types
+}
+program tgenconst11;
+type
+	generic TConst<const U: integer> = class end;
+var
+	a:specialize TConst<10>;
+begin
+	a:=specialize TConst<'string'>.Create;
+end
\ No newline at end of file
diff --git a/tests/test/tgenconst12.pp b/tests/test/tgenconst12.pp
new file mode 100644
index 0000000000..d92bc19466
--- /dev/null
+++ b/tests/test/tgenconst12.pp
@@ -0,0 +1,14 @@
+{$mode objfpc}
+{
+  test def compare with specialized types
+}
+program tgenconst12;
+
+type
+  generic TTest<const U: integer> = class
+  end;
+
+type
+	ATest = specialize TTest<100>;
+begin 
+end.
diff --git a/tests/test/tgenconst13.pp b/tests/test/tgenconst13.pp
new file mode 100644
index 0000000000..13235d1437
--- /dev/null
+++ b/tests/test/tgenconst13.pp
@@ -0,0 +1,51 @@
+{$mode objfpc}
+{$modeswitch advancedrecords}
+{
+	test advanced record constants assigned from generic constant values
+}
+program tgenconst13;
+
+type
+	kNames = set of (Blaise,Pascal);
+	kChars = set of char;
+type
+	generic TBoolean<const U: boolean> = record const value = U; end;
+	generic TString<const U: string> = record const value = U; end;
+	generic TFloat<const U: single> = record const value = U; end;
+	generic TInteger<const U: integer> = record const value = U; end;
+	generic TByte<const U: byte> = record const value = U; end;
+	generic TChar<const U: char> = record const value = U; end;
+	generic TQWord<const U: QWord> = record const value = U; end;
+	generic TNames<const U: kNames> = record const value = U; end;
+	generic TChars<const U: kChars> = record const value = U; end;
+
+procedure Test(failed: boolean); inline;
+begin
+	if failed then
+		begin
+			writeln('failed!');
+			halt(-1);
+		end;
+end;
+
+var
+	g0: specialize TBoolean<true>;
+	g1: specialize TString<'string'>;
+	g2: specialize TFloat<10.5>;
+	g3: specialize TInteger<10>;
+	g4: specialize TByte<255>;
+	g5: specialize TChar<'a'>;
+	g6: specialize TQWord<1000000000>;
+	g7: specialize TNames<[Blaise,Pascal]>;
+	g8: specialize TChars<['a','b']>;
+begin
+	Test(g0.value <> true);
+	Test(g1.value <> 'string');
+	Test(g2.value <> 10.5);
+	Test(g3.value <> 10);
+	Test(g4.value <> 255);
+	Test(g5.value <> 'a');
+	Test(g6.value <> 1000000000);
+	Test(g7.value <> [Blaise,Pascal]);
+	Test(g8.value <> ['a','b']);
+end.
diff --git a/tests/test/tgenconst14.pp b/tests/test/tgenconst14.pp
new file mode 100644
index 0000000000..0e4ad6e61a
--- /dev/null
+++ b/tests/test/tgenconst14.pp
@@ -0,0 +1,36 @@
+{$mode objfpc}
+{$modeswitch advancedrecords}
+{
+  test binary operators with generic constant params
+}
+program tgenconst14;
+
+type
+  generic TBinaryOp<const I: Integer> = record
+    const
+    	d0 = I + I;
+    	d1 = I - I; 
+    	d2 = I * I; 
+    	d3 = I / I; 
+    	d4 = I div I; 
+    	d5 = I mod I; 
+    	d6 = I and I;
+    	d7 = I or I;
+      d8 = I shl I;
+      d9 = I shr I;
+  end;
+
+var
+	op: specialize TBinaryOp<100>;
+begin
+	writeln(op.d0);
+	writeln(op.d1);
+	writeln(op.d2);
+	writeln(op.d3:1:1);
+	writeln(op.d4);
+	writeln(op.d5);
+	writeln(op.d6);
+	writeln(op.d7);
+  writeln(op.d8);
+  writeln(op.d9);
+end.
\ No newline at end of file
diff --git a/tests/test/tgenconst15.pp b/tests/test/tgenconst15.pp
new file mode 100644
index 0000000000..5eea8571b4
--- /dev/null
+++ b/tests/test/tgenconst15.pp
@@ -0,0 +1,15 @@
+{%FAIL}
+{$mode objfpc}
+{$modeswitch advancedrecords}
+{
+  test binary operator error with wrong constant type
+}
+program tgenconst15;
+
+type
+  generic TInt<const I: string> = record
+    const c = I div I;
+  end;
+
+begin
+end.
\ No newline at end of file
diff --git a/tests/test/tgenconst16.pp b/tests/test/tgenconst16.pp
new file mode 100644
index 0000000000..258301621a
--- /dev/null
+++ b/tests/test/tgenconst16.pp
@@ -0,0 +1,78 @@
+{$mode objfpc}
+{$modeswitch advancedrecords}
+{
+  various operator tests
+}
+program tgenconst16;
+
+type
+  Day = (mon,tue,wed,thu,fri,sat,sun);  
+  Days = set of Day;  
+  generic TSet<const I: Days> = record
+    const
+      d0 = I + I;   // Union
+      d1 = I - I;   // Difference
+      d2 = I * I;   // Intersection
+      d3 = I >< I;  // Symmetric difference
+      d4 = I <= I;  // Contains
+      d5 = mon in I;
+  end;
+  generic TArray<const I: integer> = record
+    type
+      t0 = array[0..I - 1] of integer;
+      t1 = array[0..high(I)] of integer;
+      t2 = array[0..low(I)] of integer;
+      t3 = array[0..sizeof(I)] of integer;
+    public
+      d0: array[0..I - 1] of integer;
+      d1: array[0..high(I)] of integer;
+      d2: array[0..low(I)] of integer;
+      d3: array[0..sizeof(I)] of integer;
+  end;
+  generic TUnaryOp<const I: integer> = record
+    const
+      d0 = -I;
+      d1 = +I;
+      d2 = not I;
+  end;
+  generic TBinaryOp<const I: integer> = record
+    const
+      // Arithmetic operators
+      // https://freepascal.org/docs-html/ref/refsu45.html
+      d0 = I + I;
+      d1 = I - I;
+      d2 = I * I; 
+      d3 = I / I; 
+      d4 = I div I; 
+      d5 = I mod I; 
+      // Boolean operators
+      // https://freepascal.org/docs-html/ref/refsu47.html
+      d6 = I and I;
+      d7 = I or I;
+      d8 = I xor I;
+      // Logical operators
+      // https://freepascal.org/docs-html/ref/refsu46.html
+      d9 = I shl I;
+      d10 = I shr I;
+      d11 = I << I;
+      d12 = I >> I;
+      // Relational operators
+      // https://freepascal.org/docs-html/ref/refsu50.html#x153-17500012.8.6
+      d13 = I <> I;
+      d14 = I < I;
+      d15 = I > I;
+      d16 = I <= I;
+      d17 = I >= I;
+      d18 = I = I;
+  end;
+  generic TOther<const I: integer> = record
+    procedure DoThis(param: integer = I);
+  end;
+
+procedure TOther.DoThis(param: integer = I);
+begin
+  writeln(param, ' default:', I);
+end;
+
+begin
+end.
\ No newline at end of file
diff --git a/tests/test/tgenconst17.pp b/tests/test/tgenconst17.pp
new file mode 100644
index 0000000000..57782afd6d
--- /dev/null
+++ b/tests/test/tgenconst17.pp
@@ -0,0 +1,26 @@
+{$mode objfpc}
+{$modeswitch advancedrecords}
+{ 
+  testing range checking for arrays and for-loops
+}
+
+program tgenconst17;
+
+type
+	generic TStaticList<T; const Length: SizeUInt> = record
+	  Values: array[0..Length - 1] of T;
+	  procedure Display;
+	end;
+
+procedure TStaticList.Display;
+var 
+	I, n: SizeUInt;
+begin
+  for I := 0 to Length - 1 do
+  	WriteLn(Values[I]);
+end;
+
+var
+	list: specialize TStaticList<Integer, 20>;
+begin
+end.
diff --git a/tests/test/tgenconst18.pp b/tests/test/tgenconst18.pp
new file mode 100644
index 0000000000..b539384759
--- /dev/null
+++ b/tests/test/tgenconst18.pp
@@ -0,0 +1,12 @@
+{%FAIL}
+{$mode objfpc}
+{
+  test undefined constants which must be typed
+}
+program tgenconst18;
+
+type
+	generic TUndefined<const U> = record end;
+
+begin
+end.
diff --git a/tests/test/tgenconst2.pp b/tests/test/tgenconst2.pp
new file mode 100644
index 0000000000..ccd68e4a40
--- /dev/null
+++ b/tests/test/tgenconst2.pp
@@ -0,0 +1,13 @@
+{$mode objfpc}
+{
+  test lists of types/contants
+}
+program tgenconst2;
+
+type
+	generic TMoreThanOne<T1,T2;const U1,U2:integer> = record end;
+	
+var
+	a: specialize TMoreThanOne<integer,string,10,10>;
+begin
+end.
diff --git a/tests/test/tgenconst3.pp b/tests/test/tgenconst3.pp
new file mode 100644
index 0000000000..c282e36f78
--- /dev/null
+++ b/tests/test/tgenconst3.pp
@@ -0,0 +1,19 @@
+{$mode objfpc}
+{$modeswitch advancedrecords}
+{
+  test integer constants in static array ranges
+}
+program tgenconst3;
+
+type
+	generic TList<T;const U:integer> = record
+		const
+			max = U;
+		public
+			m_list: array[0..max-1] of T;
+	end;
+
+var
+	list: specialize TList<integer,128>;
+begin
+end.
diff --git a/tests/test/tgenconst4.pp b/tests/test/tgenconst4.pp
new file mode 100644
index 0000000000..dfb66a19f5
--- /dev/null
+++ b/tests/test/tgenconst4.pp
@@ -0,0 +1,14 @@
+{$mode objfpc}
+{
+  test constants in generic procedures
+}
+program tgenconst4;
+
+generic procedure DoThis<T;const U:string>(msg: string = U);
+begin
+	writeln(msg, ' sizeof:',sizeof(t), ' default: ', U);
+end;
+
+begin
+	specialize DoThis<integer,'genparam'>('hello world');
+end.
diff --git a/tests/test/tgenconst5.pp b/tests/test/tgenconst5.pp
new file mode 100644
index 0000000000..1983bb7b19
--- /dev/null
+++ b/tests/test/tgenconst5.pp
@@ -0,0 +1,27 @@
+{$mode objfpc}
+{
+	test nested generic records with constants
+}
+program tgenconst5;
+
+type
+	generic THelperA<const U:integer> = record
+		list: array[0..U-1] of byte;
+	end;
+
+type
+	generic THelperB<T> = record
+		value: T;
+	end;
+
+type
+	generic TList<T; const U:integer> = record
+		helperA: specialize THelperA<U>;
+		helperB: specialize THelperB<T>;
+	end;
+
+var
+	list: specialize TList<integer,32>;
+begin
+	writeln('sizeof:',sizeof(list));
+end.
diff --git a/tests/test/tgenconst6.pp b/tests/test/tgenconst6.pp
new file mode 100644
index 0000000000..d51ef2fc06
--- /dev/null
+++ b/tests/test/tgenconst6.pp
@@ -0,0 +1,24 @@
+{$mode delphi}
+{
+  test delphi mode
+}
+program tgenconst6;
+
+type
+	TList<T; const U: integer> = class
+		list: array[0..U-1] of T;
+		function capacity: integer;
+	end;
+
+function TList<T; const U: integer>.capacity: integer;
+begin
+	result := U;	
+end;	
+
+var
+	nums:TList<integer,16>;
+	strs:TList<string,16>;
+begin
+	nums := TList<integer,16>.Create;
+	strs := TList<string,16>.Create;
+end.
diff --git a/tests/test/tgenconst7.pp b/tests/test/tgenconst7.pp
new file mode 100644
index 0000000000..22bd037ebf
--- /dev/null
+++ b/tests/test/tgenconst7.pp
@@ -0,0 +1,14 @@
+{%FAIL}
+{$mode objfpc}
+{
+  test type mismatch when specializing constant values
+}
+program tgenconst7;
+
+type
+	generic TInteger<const U: integer> = record end;
+
+var
+	a: specialize TInteger<'string'>;
+begin
+end.
diff --git a/tests/test/tgenconst8.pp b/tests/test/tgenconst8.pp
new file mode 100644
index 0000000000..418ba3c63e
--- /dev/null
+++ b/tests/test/tgenconst8.pp
@@ -0,0 +1,14 @@
+{%FAIL}
+{$mode objfpc}
+{
+  test out of range error with constants
+}
+program tgenconst8;
+
+type
+	generic TByte<const U: Byte> = record end;
+	
+var
+	a: specialize TByte<300>;
+begin
+end.
diff --git a/tests/test/tgenconst9.pp b/tests/test/tgenconst9.pp
new file mode 100644
index 0000000000..8438b70cb6
--- /dev/null
+++ b/tests/test/tgenconst9.pp
@@ -0,0 +1,12 @@
+{%FAIL}
+{$mode objfpc}
+{
+  test type mismatch when specializing constants with types
+}
+program tgenconst9;
+type
+	generic TByte<const U: Byte> = record end;
+var
+	a: specialize TByte<string>;
+begin
+end.