Shared via mypy Playground

main.py

from typing import Literal, Optional, overload

@overload
def gimme(x: Literal[True]) -> str: ...
@overload
def gimme(x: Literal[False]) -> None: ...
@overload
def gimme(x: bool) -> Optional[str]: ...

def gimme(x: bool) -> Optional[str]:
    if x:
        return "yes"
    else:
        return None

a: int = gimme(True)
b: int = gimme(False)
c: int = gimme(3 % 2 == 0)