Shared via mypy Playground

main.py

from collections.abc import Callable

def typed[**P, T](f: Callable[P, T]) -> Callable[P, T]:
    return f

def untyped(f):
    return f
    

def foo(a: int, b: str) -> bool:
    return bool(a) and bool(b)

reveal_type(typed(foo))
reveal_type(untyped(foo))