class BaseCallableTests:
    ...
    def test_determine_new_args(self):
        Callable = self.Callable
        T = TypeVar("T")
        P = TypeVar("P")

        class C(Generic[T]): ...

        S = Callable[[C], P]
        U = S[T]
        if self.Callable is collections.abc.Callable:
            self.assertEqual(U, Callable[[C[T]], T])
        else:
            self.assertEqual(U, Callable[[C], T])
    ...

from typing import TypeVar, Generic
from collections.abc import Callable
from typing import Callable as TypingCallable


T = TypeVar("T")
P = TypeVar("P")
Z = TypeVar("Z")

class C(Generic[Z]): ...

S = Callable[[C], P]
U = S[T]
U
> collections.abc.Callable[[__main__.C[~Z]], ~T]
S_T = TypingCallable[[C], P]
U_T = S_T[T]
U_T
> typing.Callable[[__main__.C], ~T]