Shared via mypy Playground

main.py

from collections.abc import Callable, Iterable, Iterator
from typing import TypeVar, TypeAlias
from contextlib import contextmanager

_T = TypeVar('_T')

GenericFn = Callable[[_T], _T]

@contextmanager
def make_generic() -> Iterator[GenericFn[_T]]:
    def rv(obj: _T) -> _T:
        return obj
    yield rv

ExplicitAliasGenericFn: TypeAlias = Callable[[_T], _T]
    
@contextmanager
def make_generic_explicit() -> Iterator[ExplicitAliasGenericFn[_T]]:
    def rv(obj: _T) -> _T:
        return obj
    yield rv

@contextmanager
def make_generic_inline() -> Iterator[Callable[[_T], _T]]:
    def rv(obj: _T) -> _T:
        return obj
    yield rv
 
NotGenericFn = Callable[[Callable[[], None]], None]

@contextmanager
def make_not_generic() -> Iterator[NotGenericFn]:
    def rv(fn: Callable[[], None]) -> None:
        return fn()
    yield rv