Fix SupportsAnext & contextlib._SupportsAclose.

Co-authored-by: https//@graingert.co.uk

Author: AlexWaygood

stdlib/_typeshed/__init__.pyi

@@ -7,7 +7,7 @@ import ctypes
 import mmap
 import sys
 from os import PathLike
-from typing import AbstractSet, Any, Container, Generic, Iterable, Protocol, TypeVar, Union
+from typing import AbstractSet, Any, Awaitable, Container, Generic, Iterable, Protocol, TypeVar, Union
 from typing_extensions import Final, Literal, final
 
 _KT = TypeVar("_KT")
@@ -33,7 +33,7 @@ class SupportsNext(Protocol[_T_co]):
 
 # stable
 class SupportsAnext(Protocol[_T_co]):
-    async def __anext__(self) -> _T_co: ...
+    def __anext__(self) -> Awaitable[_T_co]: ...
 
 # Comparison protocols
 

stdlib/builtins.pyi

@@ -29,6 +29,7 @@ from typing import (
     IO,
     AbstractSet,
     Any,
+    Awaitable,
     BinaryIO,
     ByteString,
     Generic,
@@ -72,6 +73,8 @@ _T4 = TypeVar("_T4")
 _T5 = TypeVar("_T5")
 _SupportsNextT = TypeVar("_SupportsNextT", bound=SupportsNext[Any], covariant=True)
 _SupportsAnextT = TypeVar("_SupportsAnextT", bound=SupportsAnext[Any], covariant=True)
+_AwaitableT = TypeVar("_AwaitableT", bound=Awaitable[Any])
+_AwaitableT_co = TypeVar("_AwaitableT_co", bound=Awaitable[Any], covariant=True)
 
 class _SupportsIter(Protocol[_T_co]):
     def __iter__(self) -> _T_co: ...
@@ -1068,10 +1071,17 @@ class _PathLike(Protocol[_AnyStr_co]):
 
 if sys.version_info >= (3, 10):
     def aiter(__async_iterable: _SupportsAiter[_SupportsAnextT]) -> _SupportsAnextT: ...
+
+    class _SupportsSynchronousAnext(Protocol[_AwaitableT_co]):
+        def __anext__(self) -> _AwaitableT_co: ...
+
+    class _SupportsAwaitableAnext(Protocol[_T_co]):
+        def __anext__(self) -> Awaitable[_T_co]: ...
+
     @overload
-    async def anext(__i: SupportsAnext[_T]) -> _T: ...
+    def anext(__i: _SupportsSynchronousAnext[_AwaitableT]) -> _AwaitableT: ...
     @overload
-    async def anext(__i: SupportsAnext[_T], default: _VT) -> _T | _VT: ...
+    async def anext(__i: _SupportsAwaitableAnext[_T], default: _VT) -> _T | _VT: ...
 
 # TODO: `compile` has a more precise return type in reality; work on a way of expressing that?
 if sys.version_info >= (3, 8):

stdlib/contextlib.pyi

@@ -155,7 +155,7 @@ class closing(AbstractContextManager[_SupportsCloseT]):
 
 if sys.version_info >= (3, 10):
     class _SupportsAclose(Protocol):
-        async def aclose(self) -> object: ...
+        def aclose(self) -> Awaitable[object]: ...
     _SupportsAcloseT = TypeVar("_SupportsAcloseT", bound=_SupportsAclose)
 
     class aclosing(AbstractAsyncContextManager[_SupportsAcloseT]):