[fpc-devel] (class) helper questions

[Sven Barth]

Hello together!

I'm coming along with the class helpers rather well, but I've got still 
a few questions. :)

1. As I'm going to implement record helpers in the next time I've 
noticed that I need the modeswitch for advanced records only for 
declaring such a record.
So how should I proceed regarding record helpers: Should the declaration 
of record helpers be restricted to that mode switch or should I allow it 
always?

2. I've done some tests regardings generics in Delphi XE and have found 
out, that the following example does not compile there:

=== source begin ===
   TFoo<T> = class
     Field: T;
   end;

   TFooInteger = TFoo<Integer>;

   TFooHelper = class helper for TFooInteger
   end;
=== source end ===

The compiler complains here that TFoo<T> is not yet completely defined. 
If I introduce an alias it does not work either, but if I subclass from 
TFooInteger and extend that class it does work (maybe the declaration of 
TFooInteger is treated like an alias in Delphi?).
In FPC the above example currently compiles (there was no change needed 
for that). While I might file a bug report at Embarcadero, I'd like to 
know what your opinion regarding the correct behavior is.

3. Virtual methods and class helpers are another topic where a question 
is left. For correctly checking "override", etc. for helpers in mode 
Delphi I'm leaving the flags for virtual, etc. in the procdef although 
they should be ignored at the end. But the compiler checks them in some 
parts to do some special things for virtual methods (VMT, debug 
information, special code generation in the backends).
The first two are solved rather easy, but should I introduce a check for 
helpers in the backends (calling "is_objectpascal_helper" for the owner 
of the procdef of the symbol) or should I introduce a "ignorevirtual" 
flag? I personally don't want the special virtual code to be generated 
for class helper methods, because it's unnecessary.

4. The syntax that was introduced by Borland is not very pascalish in my 
opinion. So I'd like to change the syntax for mode ObjFPC a bit (sadly 
this won't simplify the parser anymore because of the Delphi compatibility).

Delphi syntax:

TypeIdentifier = class|record helper(ParentHelper) for ExtendedType

Proposed FPC syntax:

TypeIdentifier = helper(ParentHelper) for class|record ExtendedType

What do you think? Maybe also the "class|record" part can be left out, 
because this part is not saved in the objectdef and can be determined by 
the compiler automatically.

Regards,
Sven