Fix contextlib.asynccontextmanager to work with coroutine functions

stdlib/contextlib.pyi

@@ -2,7 +2,7 @@ import abc
 import sys
 from _typeshed import FileDescriptorOrPath, Unused
 from abc import abstractmethod
-from collections.abc import AsyncGenerator, AsyncIterator, Awaitable, Callable, Generator, Iterator
+from collections.abc import AsyncGenerator, AsyncIterator, Awaitable, Callable, Coroutine, Generator, Iterator
 from types import TracebackType
 from typing import IO, Any, Generic, Protocol, TypeVar, overload, runtime_checkable
 from typing_extensions import ParamSpec, Self, TypeAlias
@@ -104,6 +104,11 @@ else:
             self, typ: type[BaseException] | None, value: BaseException | None, traceback: TracebackType | None
         ) -> bool | None: ...
 
+@overload
+def asynccontextmanager(
+    func: Callable[_P, Coroutine[Any, Any, AsyncIterator[_T_co]]]
+) -> Callable[_P, _AsyncGeneratorContextManager[_T_co]]: ...
+@overload
 def asynccontextmanager(func: Callable[_P, AsyncIterator[_T_co]]) -> Callable[_P, _AsyncGeneratorContextManager[_T_co]]: ...
 
 class _SupportsClose(Protocol):

test_cases/stdlib/check_contextlib.py

@@ -1,6 +1,7 @@
 from __future__ import annotations
 
-from contextlib import ExitStack
+from contextlib import ExitStack, asynccontextmanager
+from typing import AsyncGenerator
 from typing_extensions import assert_type
 
 
@@ -18,3 +19,17 @@ class Thing(ExitStack):
     assert_type(cm, ExitStack)
 with thing as cm2:
     assert_type(cm2, Thing)
+
+
+@asynccontextmanager
+async def async_context() -> AsyncGenerator[str, None]:
+    yield "example"
+
+
+async def async_gen() -> AsyncGenerator[str, None]:
+    yield "async gen"
+
+
+@asynccontextmanager
+def async_cm_func() -> AsyncGenerator[str, None]:
+    return async_gen()