Concatenate false negative (caught by pyright, but not mypy)

[supersergiy]

Bug Report
False negative in the following example:

To Reproduce
Playground Link

from typing import Protocol
from typing_extensions import ParamSpec, Concatenate

P = ParamSpec("P")

class A(Protocol[P]):
    def foo(self, *args: P.args, **kwargs: P.kwargs):
        ...
    
def bar(b: A[P]) -> A[Concatenate[int, P]]:
    return b # no error

Expected Behavior

Type error on return b, which is what pyright does (pyright playground)

Actual Behavior

No type error.

Your Environment

• Mypy version used: 0.991