[fpc-devel] Templates / Generics Problems

[Mattias Gaertner]

There are some unsolved problems of generics in free pascal:

1.
See wiki:
http://www.freepascal.org/wiki/index.php/Generics#Notes
The generic should not use private parts of a unit:

 interface
   generictype declar
 implementation
   procedure helper;
   begin
   end
   constructor generictype.create
   begin
     helper
   end
 end.

IMO this can be allowed. But maybe it is a problem for the compiler?


2. Circle dependencies:

unit a;
interface
  generictypeA
implementation
uses B
end.

unit b;
interface
uses a
implemenation
begin
  generictypeA<integer>.create
end.

Same: a problem for the compiler?



3.
Name space.

The unit, where the template is defined, has different uses clauses, than
the unit, where the template is declared.
In which order are the units searched?
a) Ignore uses clause of template unit
b) First uses clause of template unit, then uses clause of using unit.
c) ?


4.
Automatic generic parameters:

var List: TGenericList<integer>;
begin
  List:=TGenericList.Create;
  // Note:          ^  missing <integer>
end;

I'm against automatic generic parameters.
I don't even like the generic declaration without a type name.
I would only allow named types:

type TListOfInteger = TGenericList<integer>;


Mattias