make GeneratorType inherit from Generator (#5474)

Fixes #5496

Author: JelleZijlstra

stdlib/types.pyi

@@ -2,7 +2,23 @@ import sys
 import typing
 from importlib.abc import _LoaderProtocol
 from importlib.machinery import ModuleSpec
-from typing import Any, Awaitable, Callable, Dict, Generic, Iterable, Iterator, Mapping, Optional, Tuple, Type, TypeVar, overload
+from typing import (
+    Any,
+    AsyncGenerator,
+    Awaitable,
+    Callable,
+    Dict,
+    Generator,
+    Generic,
+    Iterable,
+    Iterator,
+    Mapping,
+    Optional,
+    Tuple,
+    Type,
+    TypeVar,
+    overload,
+)
 from typing_extensions import Literal, final
 
 # Note, all classes "defined" here require special handling.
@@ -12,6 +28,7 @@ _T_co = TypeVar("_T_co", covariant=True)
 _T_contra = TypeVar("_T_contra", contravariant=True)
 _KT = TypeVar("_KT")
 _VT = TypeVar("_VT")
+_V_co = TypeVar("_V_co", covariant=True)
 
 class _Cell:
     cell_contents: Any
@@ -142,28 +159,28 @@ class ModuleType:
     __spec__: Optional[ModuleSpec]
     def __init__(self, name: str, doc: Optional[str] = ...) -> None: ...
 
-class GeneratorType:
+class GeneratorType(Generator[_T_co, _T_contra, _V_co]):
     gi_code: CodeType
     gi_frame: FrameType
     gi_running: bool
-    gi_yieldfrom: Optional[GeneratorType]
-    def __iter__(self) -> GeneratorType: ...
-    def __next__(self) -> Any: ...
+    gi_yieldfrom: Optional[GeneratorType[_T_co, _T_contra, Any]]
+    def __iter__(self) -> GeneratorType[_T_co, _T_contra, _V_co]: ...
+    def __next__(self) -> _T_co: ...
     def close(self) -> None: ...
-    def send(self, __arg: Any) -> Any: ...
+    def send(self, __arg: _T_contra) -> _T_co: ...
     @overload
     def throw(
         self, __typ: Type[BaseException], __val: typing.Union[BaseException, object] = ..., __tb: Optional[TracebackType] = ...
-    ) -> Any: ...
+    ) -> _T_co: ...
     @overload
-    def throw(self, __typ: BaseException, __val: None = ..., __tb: Optional[TracebackType] = ...) -> Any: ...
+    def throw(self, __typ: BaseException, __val: None = ..., __tb: Optional[TracebackType] = ...) -> _T_co: ...
 
-class AsyncGeneratorType(Generic[_T_co, _T_contra]):
+class AsyncGeneratorType(AsyncGenerator[_T_co, _T_contra]):
     ag_await: Optional[Awaitable[Any]]
     ag_frame: FrameType
     ag_running: bool
     ag_code: CodeType
-    def __aiter__(self) -> Awaitable[AsyncGeneratorType[_T_co, _T_contra]]: ...
+    def __aiter__(self) -> AsyncGeneratorType[_T_co, _T_contra]: ...
     def __anext__(self) -> Awaitable[_T_co]: ...
     def asend(self, __val: _T_contra) -> Awaitable[_T_co]: ...
     @overload