"Untyped decorator makes function untyped" false positive on decorator with union type

from typing import Callable, ParamSpec, TypeVar

T = TypeVar("T")
P = ParamSpec("P")

class C:
    def __call__(self, arg: Callable[P, T]) -> Callable[P, T]:
        return arg

foo: C | Callable[[Callable[P, T]], Callable[P, T]]

@foo
def bar() -> None:...

playground

use case: i have to define a decorator conditionally that can be either one of these two very similar types

Start by running the linked mypy-play example with the supplied strictness flags and inspect the decorator type-checking path for the union of callable types. Done means this reproducer no longer reports the false positive while still preserving the expected typing of bar; add or update regression coverage if the repository's existing tests expose the relevant case.