Parameterized protocol structure ignored as argument

Bug Report

Parameterized protocols seem to be largely or totally ignored when specified as argument types. Simple example:

from typing import Protocol, TypeVar

T = TypeVar("T")
T_co = TypeVar("T_co", covariant=True)


class Proto(Protocol[T_co]):
    def __call__(self, *, a: str) -> T_co:
        ...


class InvalidClass:
    def __init__(self, *, a: int) -> None:
        ...


def test(b: Proto[T]) -> T:
    return b(a="0")
    

test(InvalidClass)  # <-- should fail type checking

InvalidClass is accepted here even though it does not conform to the protocol. Here's a more detailed playground gist.

As demonstrated in the gist, the issue does not reproduce when a function is provided, only with a class. It also does not manifest with assignment, only with arguments. However, assigning with the parameter set to Any also produces an unexpected result, which might somehow be related.

• Mypy version used: 1.0
• Mypy command-line flags:
• Mypy configuration options from mypy.ini (and other config files):
• Python version used: 3.11

Start by reproducing the minimal example with mypy 1.0 on Python 3.11, then compare it with the linked playground gist and its strict flags. The fix is complete when mypy rejects test(InvalidClass) for failing to conform to Proto, while preserving the reported behavior for functions and assignments.