Positional-or-kw arg considered incompatible with positional-only argument

Bug Report

from typing_extensions import Protocol


class Func(Protocol):
    def __call__(self, __a: int, **kwargs: str) -> None:
        #              ^^^ positional-only arg
        ...
    # Same error when using PEP 570 positional-only syntax:
    # def __call__(self, a: int, /, **kwargs: str) -> None:


def myfunc(a: int, **kwargs: str) -> None:
    pass


f: Func = myfunc

Expected Behavior

In my view this should be allowed. Anyone calling f() promises to pass the 1st argument as positional. And myfunc accepts the 1st argument as positional or kwarg, so it should be considered compatible.

Actual Behavior

Mypy output:

positional_only.py:12: error: Incompatible types in assignment (expression has type "Callable[[int, KwArg(str)], Any]", variable has type "Func")
positional_only.py:12: note: "Func.__call__" has type "Callable[[int, KwArg(str)], Any]"

Your Environment

• Mypy version used: 0.942
• Mypy command-line flags: (none)
• Mypy configuration options from mypy.ini (and other config files): (none)
• Python version used: 3.10.2
• Operating system and version: macOS

Esegui l'esempio Python fornito con mypy e conferma la diagnostica dell'assegnazione incompatibile per il callable di Protocol. Traccia la gestione della compatibilità dei callable per i parametri positional-only e positional-or-keyword, quindi aggiungi un test di regressione che mostri che questa assegnazione viene accettata, mentre le chiamate incompatibili continuano a essere rifiutate.