Improve [Async]ContextDecorator type hinting (#13416)

Updated annotations allow access to `__wrapped__` on
decorated callables without complaints from typecheckers.

Author: ncoghlan

stdlib/contextlib.pyi

@@ -32,9 +32,9 @@ _T = TypeVar("_T")
 _T_co = TypeVar("_T_co", covariant=True)
 _T_io = TypeVar("_T_io", bound=IO[str] | None)
 _ExitT_co = TypeVar("_ExitT_co", covariant=True, bound=bool | None, default=bool | None)
-_F = TypeVar("_F", bound=Callable[..., Any])
 _G = TypeVar("_G", bound=Generator[Any, Any, Any] | AsyncGenerator[Any, Any], covariant=True)
 _P = ParamSpec("_P")
+_R = TypeVar("_R")
 
 _SendT_contra = TypeVar("_SendT_contra", contravariant=True, default=None)
 _ReturnT_co = TypeVar("_ReturnT_co", covariant=True, default=None)
@@ -64,9 +64,13 @@ class AbstractAsyncContextManager(ABC, Protocol[_T_co, _ExitT_co]):  # type: ign
         self, exc_type: type[BaseException] | None, exc_value: BaseException | None, traceback: TracebackType | None, /
     ) -> _ExitT_co: ...
 
+class _WrappedCallable(Generic[_P, _R]):
+    __wrapped__: Callable[_P, _R]
+    def __call__(self, *args: _P.args, **kwargs: _P.kwargs) -> _R: ...
+
 class ContextDecorator:
     def _recreate_cm(self) -> Self: ...
-    def __call__(self, func: _F) -> _F: ...
+    def __call__(self, func: Callable[_P, _R]) -> _WrappedCallable[_P, _R]: ...
 
 class _GeneratorContextManagerBase(Generic[_G]):
     # Ideally this would use ParamSpec, but that requires (*args, **kwargs), which this isn't. see #6676
@@ -93,11 +97,11 @@ class _GeneratorContextManager(
 def contextmanager(func: Callable[_P, Iterator[_T_co]]) -> Callable[_P, _GeneratorContextManager[_T_co]]: ...
 
 if sys.version_info >= (3, 10):
-    _AF = TypeVar("_AF", bound=Callable[..., Awaitable[Any]])
+    _AR = TypeVar("_AR", bound=Awaitable[Any])
 
     class AsyncContextDecorator:
         def _recreate_cm(self) -> Self: ...
-        def __call__(self, func: _AF) -> _AF: ...
+        def __call__(self, func: Callable[_P, _AR]) -> _WrappedCallable[_P, _AR]: ...
 
     class _AsyncGeneratorContextManager(
         _GeneratorContextManagerBase[AsyncGenerator[_T_co, _SendT_contra]],

stubs/decorator/decorator.pyi

@@ -7,7 +7,6 @@ from re import Pattern
 from typing import Any, Literal, TypeVar
 from typing_extensions import ParamSpec
 
-_C = TypeVar("_C", bound=Callable[..., Any])
 _Func = TypeVar("_Func", bound=Callable[..., Any])
 _T = TypeVar("_T")
 _P = ParamSpec("_P")
@@ -65,8 +64,7 @@ def decorator(
     caller: Callable[..., Any], _func: Callable[..., Any] | None = ...
 ) -> Callable[[Callable[..., Any]], Callable[..., Any]]: ...
 
-class ContextManager(_GeneratorContextManager[_T]):
-    def __call__(self, func: _C) -> _C: ...
+class ContextManager(_GeneratorContextManager[_T]): ...
 
 def contextmanager(func: Callable[_P, Iterator[_T]]) -> Callable[_P, ContextManager[_T]]: ...
 def append(a: type, vancestors: list[type]) -> None: ...