Given the following python code:

from typing import Protocol, TypeVar


class A:
    pass


class B(A):
    pass

class C(A):
    pass


T = TypeVar("T", B, C, contravariant=True)


class X(Protocol[T]):

    def f(self, t: T) -> None:
        ...


class XTImpl(X[T]):

    def f(self, t: T) -> None:
        pass


class XBImpl(X[B]):

    def f(self, t: B) -> None:
        pass

How can I type a variable that accepts only a XTimpl instance and not XBImpl instances ?

My true use case is that I have functions

def fB(x: type[X[B]]):
    ...


def fC(x: type[X[C]]):
    ...


def fT(x):
    fB(x)
    fC(x)

And I would like to type argument x in fT

I would like something like just X for instance (for which I get error “Expected type arguments for generic class”).

If we changed T = TypeVar("T", B, C, contravariant=True) into T = TypeVar("T", A, contravariant=True) then we could just use X[A].
But in my true use case, B and C are not direct children of a common ancestor.

Thank you