User-defined TypeGuard for Callable is coroutine function has errors

[EldarSehayekZenity]

Bug Report

Defining a TypeGuard for callable to check if coroutine doesn't work when passed a generic callable with Concatenate.

To Reproduce

1. Write this code

_PArgs = ParamSpec("_PArgs")

def iscoroutinefunc(func: Callable[_PArgs, Any]) -> TypeGuard[Callable[_PArgs, Coroutine[Any, Any, Any]]]:
    return inspect.iscoroutinefunction(func)

2. Call the type guard like this:

_PRouteParams = ParamSpec("_PRouteParams")
async def my_coro(x: int, y: int, z: int) -> str:
        await asyncio.sleep(1)
        return str(x + y + z)

    async def execute_if_coro(
        my_func_or_coro: Callable[Concatenate[int, _PRouteParams], Any], *args: _PRouteParams.args, **kwargs: _PRouteParams.kwargs
    ) -> None:
        if iscoroutinefunc(my_func_or_coro):
            await my_func_or_coro(3, *args, **kwargs)
        else:
            my_func_or_coro(3, *args, **kwargs)

    await execute_if_coro(my_coro, 5, z=6)

3. Run mypy on above code with "strict=True" setting

Expected Behavior

I expected mypy to infer in execute_if_coro that my_func_or_coro can receive an a positional integer before the additional *args and **kwargs and that the result will be awaitable using await keyword.

Actual Behavior

Mypy reports 2 errors

• Argument 1 to "iscoroutinefunc" has incompatible type "Callable[[int, **_PRouteParams], Any]"; expected "Callable[[int, **_PRouteParams], Any]
• Argument 1 has incompatible type "int"; expected "[int, **_PRouteParams.args]"

Your Environment

• Mypy version used: 0.971
• Mypy command-line flags: N/A
• Mypy configuration options from mypy.ini (and other config files):

follow_imports = "normal"
ignore_errors = false
implicit_reexport = false
warn_redundant_casts = true
warn_unused_ignores = true
disallow_any_generics = true
disallow_untyped_defs = true
check_untyped_defs = true
allow_redefinition = false
local_partial_types = true
strict_optional = true
strict_equality = true
warn_unused_configs = true
warn_unreachable = true
warn_no_return = true
no_implicit_optional = true
strict = true

• Python version used: 3.10.4
• Operating system and version: Windows 11

[A5rocks]

Just as a note, I've used this code to try to test this:

from typing import ParamSpec, Callable, TypeGuard, Any, Coroutine, Concatenate
import inspect
import asyncio

_PArgs = ParamSpec("_PArgs")

def iscoroutinefunc(func: Callable[_PArgs, Any]) -> TypeGuard[Callable[_PArgs, Coroutine[Any, Any, Any]]]:
    return inspect.iscoroutinefunction(func)

_PRouteParams = ParamSpec("_PRouteParams")
async def main() -> None:
    async def my_coro(x: int, y: int, z: int) -> str:
        await asyncio.sleep(1)
        return str(x + y + z)

    async def execute_if_coro(
        my_func_or_coro: Callable[Concatenate[int, _PRouteParams], Any], *args: _PRouteParams.args, **kwargs: _PRouteParams.kwargs
    ) -> None:
        if iscoroutinefunc(my_func_or_coro):
            await my_func_or_coro(3, *args, **kwargs)
        else:
            my_func_or_coro(3, *args, **kwargs)

    await execute_if_coro(my_coro, 5, z=6)

(Just posting so I do not need to change the code next time I check. Needed to add the imports and the async main + indentation.)

[EldarSehayekZenity]

@A5rocks Thank you very much for your PR I see all checks are approved will it be merged and released soon?

[A5rocks]

Hi :)

I haven't put in time recently to the PR but I have 2 main things I need to do before it can really be looked at for real:

1. Add a regression test for all fixed issues.
2. Go through mypy-primer's output and either fix things or say why the new change is correct.

I hope to have that done in a few days!

[A5rocks]

FYI this is fixed as of Mypy 1.2! Turns out some other changed fixed this, oops.

[hauntsaninja]

mypy_primer --bisect -p test.py --debug --old v1.0.0 bisects the change in behaviour to your #14677 :-)

[JelleZijlstra]

Should we add a new test case for this?