ParamSpec and protocols

[mehdigmira]

Bug Report

ParamSpec feature doesn't seem to work well when used with Protocol.

To Reproduce

from typing import Any, ParamSpec, Protocol

P = ParamSpec("P")


class Runnable(Protocol[P]):
    def run(self, *args: P.args, **kwargs: P.kwargs) -> Any:
        ...


def foo(func: Runnable) -> int:
    ...


class A:
    def run(self, i: int) -> Any:
        ...


foo(A())

Expected Behavior

IMO, mypy shouldn't report any bug, do you agree ?

Actual Behavior

mypy logs an error, which means mypy doesn't recognize A as implementing the Runnableprotocol (which it does)

commands/typing_debug.py:20: error: Argument 1 to "foo" has incompatible type "A"; expected "Runnable[Any]"
commands/typing_debug.py:20: note: Following member(s) of "A" have conflicts:
commands/typing_debug.py:20: note:     Expected:
commands/typing_debug.py:20: note:         def run(self, *args: Any, **kwargs: Any) -> Any
commands/typing_debug.py:20: note:     Got:
commands/typing_debug.py:20: note:         def run(self, i: int) -> Any

However if foo is defined as

def foo(func: Runnable[int]) -> int:
    ...

mypy doesn't report any error.

Your Environment

• Mypy version used: 0.971
• Mypy command-line flags: no flag
• Mypy configuration options from mypy.ini (and other config files): no config file
• Python version used: 3.10.2
• Operating system and version: MacOS 12.6

[mehdigmira]

If a maintainer can acknowledge this is a bug, and give some hints on where to start digging, I'm willing to give fixing this a shot :)

[erictraut]

I'm able to type check the code above without errors using the latest published version of mypy (0.981), so I think this bug has been fixed already.

[hauntsaninja]

Yes, I fixed this in #11203. Let me know if you see anything bad with ParamSpec + Protocols on mypy 0.981