[fpc-devel] Attn: Sven Can not use "specialize" to resolve forward declaration

[Sven Barth]

Martin Frb via fpc-devel <fpc-devel at lists.freepascal.org> schrieb am Do.,
9. Dez. 2021, 00:15:

> https://gitlab.com/freepascal.org/fpc/source/-/issues/39459
> You wrote
> >> No, this can not and this will never work. When a generic parameter has
> a constraint that constraint *must* be adhered to and a forward
> declaration is *not* a valid type for such a constraint (except for
> *class* / TObject constraints).
>
> Using TObject for just any class is nice here.
>
> What to use for interface?
> https://gitlab.com/freepascal.org/fpc/source/-/issues/39459#note_758496897
>
> Sorry replied on the wrong issue.
>
>
> How can I restrain a generic param, so it must be an interface, but leave
> open the exact type, so I can later use a forward declaration?
>

For interfaces you can use IInterface/IUnknown though that will work only
for COM interfaces. For raw interfaces there is no solution currently.

In my opinion you should rethink your code structure however. I don't know
right now what would be better, but as it is now it feels bad.

Regards,
Sven

>
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