Inheritance with generics and nested record helper

Question

I'm trying to do the following in Delphi 10.1 Berlin, but the compiler return the message "F2084 Internal Error: AV0A785E48-R000000-10-0":

TMyType = (mtValue1, mtValue2);

TMyBaseClass = class
private
  FMyType: TMyType;
public
  property MyType: TMyType read FMyType write FMyType;
end;

TMyClass = class(TMyBaseClass)
private
  FOtherField: Integer;
public
  property OtherField: Integer read FOtherField write FOtherField;
end;

TMyBaseProcess1<T: TMyBaseClass> = class
strict private
  FMyClass: T;
strict protected
  type
    TMyTypeHelper = record Helper for TMyType
    public
      function ToString: string;
    end;
public
  constructor Create(AMyClass: T);
  procedure DoSomething;
end;

TMyProcess1 = class(TMyBaseProcess1<TMyClass>)
end;

TMyBaseProcess2<T: TMyBaseClass> = class
strict private
  FMyClass: T;
strict protected
  type
    TMyTypeHelper = record Helper for TMyType
    public
      function ToInteger: Integer;
    end;
public
  constructor Create(AMyClass: T);
  procedure DoSomethingElse;
end;

TMyProcess2 = class(TMyBaseProcess2<TMyClass>)
end;

The helper in TMyBaseProcess1 is totally different of the helper in TMyBaseProcess2. I can separate the helper and the class without problems. I only want to know why I can't leave them together.

Anyone knows what is the problem? Can I use generics, nested record helper and inheritance this way?

Answer 1

you can not have two helpers pointing to same class type in your case TMyType

from docs..

You can define and associate multiple helpers with a single type. However, only zero or one helper applies in any specific location in source code.

use helper outside that classes

TMyTypeHelper = record Helper for TMyType
    public
      function ToInteger: Integer;
      function ToString: string; 
    end;