[fpc-pascal]forward declaration of classes

[Peter Vreman]

> Hi all,
> 
> If I forward define a class, e.g. 'TMyForwardClass = class;', in the interface section
and
put the real definition in the implementation section, the compiler gives a
> 
> test1.pas(144) Warning: test1.ppu Interface CRC changed 1718528929<>2054119697
> 
> but it compiles.
> I'm not sure if this is wanted. Definitions in the implementation section should not be
visible, but this way I could use the class internals of TMyForwardClass in an another
unit, as if the class is defined completely in the interface section.
> 
> What is the bug and what should be the right behaviour?
> 
> I think, bug 1599 is something similar.

I guess it's a bug, but what does Delphi give?