Generic type alias?

[desmond-dsouza]

Not sure if this is Question or Issue. Is the IterFunc alias below allowed? There is no other way to alias a complex generic types.

from typing import TypeVar, Callable, Iterator, Iterable

T = TypeVar("T")

IterFunc = Callable[[], Iterator[T]]

def s_map(f: Callable[[T], T], l: Iterable[T]) -> IterFunc:
    return lambda: map(f, l)

Mypy rejects it with:

 Invalid type "__main__.T"

Thanks.

[JukkaL]

It's not supported yet, but I think that PEP 484 allows it.

There is another possible interpretation of the alias that was discussed before (I can't find the issue), in which X = Dict[str, T] would make X[int] mean Dict[str, int], for example.

[gvanrossum]

Yes, PEP 484 explicitly allows this. I think the other issue you're thinking of is in typehinting: python/typing#115. Also that mentions #606 here, which this is probably a duplicate of.

[JukkaL]

Yeah, this looks like a duplicate of #606. Closing this.