`unreachable` false positive when using `isinstance` on class with `__call__` when function parameter uses `ParamSpec`

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from typing import Callable, ParamSpec

P = ParamSpec("P")


class Foo:
    def __call__(self) -> None:
        ...


def foo(fn: Callable[P, None]) -> None:
    if isinstance(fn, Foo):
        print("reached") # error: Statement is unreachable  [unreachable]


foo(Foo())

playground

in this example, that line is always reached at runtime

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minified further:

from typing import Callable

def foo(fn: Callable[[], object]) -> None:
    if isinstance(fn, type):
        print(fn)

[sterliakov]

Works since v1.11.0, resolved in #17389.