Cannot instantiate type "Type[Callable[[int], int]]" [misc]

[randolf-scholz]

How to resolve this?

from typing import Callable, ParamSpec, Concatenate, TypeAlias

class Foo:
    def __call__(self, x: int) -> int:
        return x

A: type[Callable[[int], int]] = Foo
a: Callable[[int], int] = A()  # ✘ Cannot instantiate type

P = ParamSpec("P")
intfun: TypeAlias = Callable[Concatenate[int, P], int]

B: type[intfun] = Foo # ✘ Incompatible types in assignment
b: intfun = B() # ✘ Cannot instantiate type

• https://mypy-play.net/?mypy=latest&python=3.11&gist=99062a3e01ccb8c92b6c5ec57b6a0e12
• https://stackoverflow.com/questions/75390522

[randolf-scholz]

One could create a Protocol for the first part, but in that case, how do you add the ParamSpec to the Protocol? The best I could come up with is

class Proto(Protocol[P]):
    __call__: Callable[Concatenate[Tensor, P], Tensor]

which doesn't work for other reasons (raises [assignment] and "Protocol member Proto.__call__ expected settable variable, got read-only attribute" when trying to do A: type[Proto] = Foo)

[hmc-cs-mdrissi]

class Proto(Protocol[P]):
    def __call__(self, x: int, *args: P.args, **kwargs: P.kwargs) -> int:
        ...

def f(x: int, y: str) -> int:
    return 1


x: Proto[str] = f

works.