[fpc-devel] generic forward declaration?

[Mattias Gaertner]

On 7/30/25 13:01, Martin Frb via fpc-devel wrote:
> On 30/07/2025 12:23, Mattias Gaertner via fpc-devel wrote:
>>[...]
>> pas2js compiles it.
>> OTOH pas2js currently creates 3 internal specializations for each TFoo 
>> and TBar.
> 
> There should only be
> 
> TFoo<Byte, Boolean>
> TFoo<Boolean, Byte>

Yes.
Well, actually, in your example you don't use them, so pas2js omits a lot.

But internally while resolving the code it already creates a 
specialization for F

   generic TFoo<A, B> = class
     F:specialize TBar<A,B>;

with the generic template parameter A and B, so it can resolve and check 
the generic code. This specialization is never transpiled to code. It 
merely exists for type checking. It's a todo to create less of these 
internal specializations.


> If you got 3 then you got one of them twice. And if they are different 
> types, then at some point you get issues with assigning them to the fields?

Each generic type in pas2js has a list of specializations with each 
combination of parameters unique.
This is enough for simple programs, but for packages Delphi supports 
duplicate specializations.


Mattias