use Self in async context managers (#5724)

stdlib/asyncio/events.pyi

@@ -1,6 +1,6 @@
 import ssl
 import sys
-from _typeshed import FileDescriptorLike
+from _typeshed import FileDescriptorLike, Self
 from abc import ABCMeta, abstractmethod
 from socket import AddressFamily, SocketKind, _Address, _RetAddress, socket
 from typing import IO, Any, Awaitable, Callable, Dict, Generator, List, Optional, Sequence, Tuple, TypeVar, Union, overload
@@ -57,7 +57,7 @@ class TimerHandle(Handle):
 class AbstractServer:
     def close(self) -> None: ...
     if sys.version_info >= (3, 7):
-        async def __aenter__(self: _T) -> _T: ...
+        async def __aenter__(self: Self) -> Self: ...
         async def __aexit__(self, *exc: Any) -> None: ...
         def get_loop(self) -> AbstractEventLoop: ...
         def is_serving(self) -> bool: ...

stdlib/contextlib.pyi

@@ -72,14 +72,12 @@ class redirect_stderr(ContextManager[_T_io]):
 class ContextDecorator:
     def __call__(self, func: _F) -> _F: ...
 
-_U = TypeVar("_U", bound=ExitStack)
-
 class ExitStack(ContextManager[ExitStack]):
     def __init__(self) -> None: ...
     def enter_context(self, cm: ContextManager[_T]) -> _T: ...
     def push(self, exit: _CM_EF) -> _CM_EF: ...
     def callback(self, callback: Callable[..., Any], *args: Any, **kwds: Any) -> Callable[..., Any]: ...
-    def pop_all(self: _U) -> _U: ...
+    def pop_all(self: Self) -> Self: ...
     def close(self) -> None: ...
     def __enter__(self: Self) -> Self: ...
     def __exit__(
@@ -90,8 +88,6 @@ class ExitStack(ContextManager[ExitStack]):
     ) -> bool: ...
 
 if sys.version_info >= (3, 7):
-    _S = TypeVar("_S", bound=AsyncExitStack)
-
     _ExitCoroFunc = Callable[[Optional[Type[BaseException]], Optional[BaseException], Optional[TracebackType]], Awaitable[bool]]
     _CallbackCoroFunc = Callable[..., Awaitable[Any]]
     _ACM_EF = TypeVar("_ACM_EF", AsyncContextManager[Any], _ExitCoroFunc)
@@ -103,9 +99,9 @@ if sys.version_info >= (3, 7):
         def push_async_exit(self, exit: _ACM_EF) -> _ACM_EF: ...
         def callback(self, callback: Callable[..., Any], *args: Any, **kwds: Any) -> Callable[..., Any]: ...
         def push_async_callback(self, callback: _CallbackCoroFunc, *args: Any, **kwds: Any) -> _CallbackCoroFunc: ...
-        def pop_all(self: _S) -> _S: ...
+        def pop_all(self: Self) -> Self: ...
         def aclose(self) -> Awaitable[None]: ...
-        def __aenter__(self: _S) -> Awaitable[_S]: ...
+        def __aenter__(self: Self) -> Awaitable[Self]: ...
         def __aexit__(
             self,
             __exc_type: Optional[Type[BaseException]],

stubs/aiofiles/aiofiles/base.pyi

@@ -1,3 +1,4 @@
+from _typeshed import Self
 from types import CodeType, FrameType, TracebackType, coroutine
 from typing import Any, Coroutine, Generator, Generic, Iterator, Optional, Type, TypeVar, Union
 
@@ -8,7 +9,7 @@ _T_contra = TypeVar("_T_contra", contravariant=True)
 
 class AsyncBase(Generic[_T]):
     def __init__(self, file: str, loop: Any, executor: Any) -> None: ...
-    async def __aiter__(self) -> Iterator[_T]: ...
+    async def __aiter__(self: Self) -> Self: ...
     async def __anext__(self) -> _T: ...
 
 class AiofilesContextManager(Generic[_T_co, _T_contra, _V_co]):