program HelperBug;

{$modeswitch advancedrecords}
{$modeswitch typehelpers}

type

  TTestInner = record
    A: Integer;
    B: array of Integer;
    procedure SetBWithoutHelper(Value: Integer); inline;
  end;

  TTest = record
    A: Integer;
    B: array of Integer;
    TestInner: TTestInner;
  end;

  TTestHelper = record helper for TTest
    procedure SetBWithHelper(Value: Integer); inline;
  end;

  TTestInnerHelper = record helper for TTestInner
    procedure SetBWithHelper(Value: Integer); inline; //inline is needed for error
  end;

  procedure TTestInner.SetBWithoutHelper(Value: Integer);
  begin
    B[0] := Value;
  end;

  procedure TTestInnerHelper.SetBWithHelper(Value: Integer);
  begin
    B[0] := Value;
  end;

  procedure TTestHelper.SetBWithHelper(Value: Integer);
  begin
    B[0] := Value;
  end;

var
  Test: TTest;
begin

  Test.B := nil; //Otherwise compiler warns, despite setlength initializes everything to 0 according to documentation

  //Setting lengths
  setlength(Test.B, 1);
  setlength(Test.TestInner.B, 1); //Note: Curiously compiler does NOT warn here about no initialization

  //First tests all fine
  Test.B[0] := 1;
  Test.SetBWithHelper(1);
  with Test do
    SetBWithHelper(1);

  //Still all fine here
  Test.TestInner.B[0] := 1;
  Test.TestInner.SetBWithHelper(1);
  Test.TestInner.SetBWithoutHelper(1);
  with Test.TestInner do
    SetBWithoutHelper(1);

  //Causes range check error or crashes without checks
  with Test.TestInner do
    SetBWithHelper(1);
end.