[fpc-pascal] bug or feature?

[Michael Van Canneyt]

On Sat, 12 Feb 2022, Sven Barth via fpc-pascal wrote:

> Michael Van Canneyt via fpc-pascal <fpc-pascal at lists.freepascal.org>
> schrieb am Sa., 12. Feb. 2022, 12:14:
>
>>
>>
>> On Sat, 12 Feb 2022, Mattias Gaertner via fpc-pascal wrote:
>>
>>> Hi,
>>>
>>> This can't be right, can it?
>>>
>>> type
>>>  TBird = class
>>>    procedure Fly;
>>>  end;
>>>  TEagle = TBird; // alias
>>>
>>> procedure TEagle.Fly;
>>> begin
>>> end;
>>
>> Personally, I would not allow this.
>> But Delphi compiles and runs it...
>>
>> Maybe something to check for {$mode objfpc} =-)
>>
>
> The compiler does not have any real tracking for non-type aliases... As far
> as the compiler is concerned these are interchangeable...

I think Mattias just got some more gray hairs :-)

So if I understand this correctly, I can do

---
Interface

Type
   TSomeReallyAnnoyingIncrediblyLongClassName = Class
     Procedure DoSomething;
   end;

implementation

Type
   T1 = TSomeReallyAnnoyingUltraLongClassName;

procedure T1.DoSomething;

begin
end;
---

And consequently also

---
Interface

Type
   TSomeReallyAnnoyingIncrediblyLongClassName = Class
   Type
      TSomeReallyAnnoyingSubClass = class
         Procedure DoSomething;
      end;
   end;

implementation

Type
   T1 = TSomeReallyAnnoyingIncrediblyLongClassName.TSomeReallyAnnoyingSubClass;

procedure T1.DoSomething;

begin
end;
---

The lazarus code tools maintainer will have a field day with this one ;-)

Michael.

PS. Just tested, the compiler accepts both... Amazing, I never thought this
would be possible. I'd better update the docs :-)