`hasCustomPragma` does not work on generic types about nim HOT 2 OPEN

The type of Y[X].T is typedesc[X], but it also stores the info of the symbol T of the original unresolved generic param and this is what getTypeInst gives. This symbol is given to the type here and here (with linkTo).

From what I understand this shouldn't happen, a typedesc type should not have a bound symbol unless it is literally typedesc. But I don't know which makes the most sense to do:

1. Remove the linkTo lines in readTypeParameter and just return an nkType node; this might lose information or break stuff
2. To the and t.sym != nil condition in mapTypeToAstX, add and t.kind != tyTypeDesc; this seems too specific
3. To fix #23564 as well we can add and t.kind notin {tyTypeDesc, tyAlias} instead. That is, the only types where an "instantiation symbol" is ignored in favor of the implementation become typedescs or primitive alias types like type T = X. This has the caveat of defining new behavior for getTypeInst that might be incompatible with old behavior. We could also combine the first option with and t.kind != tyAlias instead but this seems more independent of compiler internals.

Edit: Actually I think hasCustomPragma should deal with tyAlias, getTypeInst shouldn't skip it.

from nim.

I don't understand the purpose of taking the generic T before hasCustomPragma

echo Y[X].T.hasCustomPragma(p) # why do you need to work on the typedesc ?
echo Y[X].t.hasCustomPragma(p) # Works 

from nim.