False negative: covariant `TypeVar`s not rejected in function signatures

To Reproduce

mypy accepts the following code without issues:

from typing import Generic, TypeVar

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

class FooGeneric(Generic[T_co]):
    pass

def accepts_foo(x: FooGeneric[T_co]) -> None:
    pass

Expected Behavior

My understanding is that covariant and contravariant are only allowed on type variables used to parameterise generics.

As such anything other than accepts_foo(x: FooGeneric[T]) (or accepts_foo(x: FooGeneric)) should be rejected. For example accepts_foo(x: FooGeneric[T_contra]) is also accepted, but this makes no sense: accepts_foo cannot define its own version of FooGeneric that acts contravariantly in its type variable.

Your Environment

• Mypy version used: 0.950
• Python version used: 3.10.0
• Operating system and version: Ubuntu 20.04.2 on WSL2 on Windows 10

No source file or test is named. Start by reproducing the provided snippet with mypy and then trace the type-variable variance validation; done means signatures using covariant or contravariant TypeVars are rejected while the stated valid forms remain accepted.