Shared via mypy Playground

main.py

from enum import Enum


class Foo(Enum):
    A = 0
    B = 0



def bar(foo: Foo) -> None:
    if foo is Foo.A:
        ...
    elif foo is Foo.B:
        ...
    else:
        # some long other logic for whatever reason.
        # should be marked as unreachable
        message = "unknown Foo"
        raise ValueError(message, foo)