from typing import Callable, overload, reveal_type

@overload
def foo(x: int) -> int: ...
@overload
def foo(x: str) -> str: ...
def foo(x: int | str) -> int | str: ...

def copy[A, B](c: Callable[[A], B]) -> Callable[[A], B]: ...

foo_copy = copy(foo)
reveal_type(foo_copy) # (int) -> int
foo_copy(1)
foo_copy("42") # should not error here