Incompatible type when using asynccontextmanager and ParamSpec in generics.

[matiuszka]

Bug Report

Usage of asynccontexmanager together with ParamSpec casues mypy errors.

To Reproduce

from contextlib import asynccontextmanager
from dataclasses import dataclass
from typing import (
    AsyncContextManager,
    AsyncIterator,
    Callable,
    Generic,
    ParamSpec,
    TypeVar,
)

_Input = ParamSpec("_Input")
_Result = TypeVar("_Result")


@dataclass
class Foo(Generic[_Input, _Result]):
    func: Callable[_Input, AsyncContextManager[_Result]]

    @asynccontextmanager
    async def boo(
        self, *args: _Input.args, **kwargs: _Input.kwargs
    ) -> AsyncIterator[_Result]:
        async with self.func(*args, **kwargs) as fr:
            yield fr

Actual Behavior

Error:

error: Argument 1 to "asynccontextmanager" has incompatible type "Callable[[Arg(Foo[_Input, _Result], 'self'), **_Input], AsyncIterator[_Result]]"; expected "Callable[[Arg(Foo[_Input, _Result], 'self'), **_Input], AsyncIterator[_Result]]"

Environment

Mypy version: 0.950
Python version: 3.10.3

[erictraut]

This bug appears to have been fixed in mypy 1.2.0.