allow using modules as a type

[DetachHead]

Feature

from __future__ import annotations

from typing import TYPE_CHECKING

if TYPE_CHECKING:
    from Sandpit import foo


def asdf() -> foo: # or Module[foo]
    from Sandpit import foo

    return foo

Pitch
this pattern is useful as a quick hack for resolving circular imports, also pycharm allows it

[erictraut]

I don't think modules should be allowed in the type system. The semantics of a module type are not well defined.

PEP 544 provides a potential solution here. It allows a protocol to describe a module's interface. This is how this would be solved in other languages like TypeScript.

It looks like mypy doesn't support this part of PEP 544 though. See this issue for details.

The other solution, of course, is to eliminate the circular dependency in your code. ;)

[emmatyping]

I think in the past people have used types.ModuleType then used hasattr etc. But I would agree that modules as types are tricky, and I think #5018 is a better solution.