Fix patch() used as decorator (#4592)

Closes: #4591

Author: srittau

stdlib/3/unittest/mock.pyi

@@ -4,6 +4,7 @@ from typing import Any, Callable, Generic, List, Mapping, Optional, Sequence, Te
 _F = TypeVar("_F", bound=Callable[..., Any])
 _T = TypeVar("_T")
 _TT = TypeVar("_TT", bound=Type[Any])
+_R = TypeVar("_R")
 
 __all__ = [
     "Mock",
@@ -193,7 +194,7 @@ class _patch(Generic[_T]):
         kwargs: Mapping[str, Any],
     ) -> None: ...
     def copy(self) -> _patch[_T]: ...
-    def __call__(self, func: _F) -> _F: ...
+    def __call__(self, func: Callable[..., _R]) -> Callable[..., _R]: ...
     def decorate_class(self, klass: _TT) -> _TT: ...
     def decorate_callable(self, func: _F) -> _F: ...
     def get_original(self) -> Tuple[Any, bool]: ...

third_party/2and3/mock.pyi

@@ -4,6 +4,7 @@ from typing import Any, Callable, Generic, List, Mapping, Optional, Sequence, Te
 _F = TypeVar("_F", bound=Callable[..., Any])
 _T = TypeVar("_T")
 _TT = TypeVar("_TT", bound=Type[Any])
+_R = TypeVar("_R")
 
 __all__ = [
     "Mock",
@@ -193,7 +194,7 @@ class _patch(Generic[_T]):
         kwargs: Mapping[str, Any],
     ) -> None: ...
     def copy(self) -> _patch[_T]: ...
-    def __call__(self, func: _F) -> _F: ...
+    def __call__(self, func: Callable[..., _R]) -> Callable[..., _R]: ...
     def decorate_class(self, klass: _TT) -> _TT: ...
     def decorate_callable(self, func: _F) -> _F: ...
     def get_original(self) -> Tuple[Any, bool]: ...