Shared via mypy Playground

main.py

from typing import Protocol, ParamSpec, Callable, Concatenate

P = ParamSpec('P')

class FuncType(Protocol[P]):
    def __call__(self, *args: P.args, x: str, **kwargs: P.kwargs) -> str: ...

def wrapper(fp: Callable[P, str]) -> FuncType[P]:
    def inner(*args: P.args, x: str, **kwargs: P.kwargs) -> str:
        print(x)
        return fp(*args, **kwargs)
    return inner

def my_f(s: str, d: float) -> str:
    return f"{s}, {d}"


wrapped = wrapper(my_f)
wrapped(1.2, x="works?")