{ %fail } {$mode objfpc} type generic TList<_T>=class(TObject) data : _T; procedure Add(item: _T); end; procedure TList.Add(item: _T); var i : integer; begin { The next line should fail for TList(string) } i:=item; data:=item; end; type TMyStringList = specialize TList; var slist : TMyStringList; begin slist := TMyStringList.Create; slist.Add('Test'); writeln(slist.data); end.