Change return types of AsyncGenerator's methods to coroutines. This b…

…rings pytype's definition in line with the definition on typeshed and reflects the fact that asynchronous generators defined using the `async def`/`yield` syntax have methods returning coroutines rather than just arbitrary awaitables.

PiperOrigin-RevId: 677779617

pytype/stubs/builtins/builtins.pytd

@@ -968,9 +968,9 @@ class coroutine(Coroutine[_T, _T2, _V]):
 class asyncgenerator(AsyncGenerator[_T, _T2]):
     __slots__ = []
     def __aiter__(self) -> asyncgenerator[_T, _T2]: ...
-    def __anext__(self) -> Awaitable[_T]: ...
-    def asend(self, value: _T2) -> Awaitable[_T]: ...
-    def aclose(self) -> Awaitable[_T]: ...
+    def __anext__(self) -> coroutine[Any, Any, _T]: ...
+    def asend(self, value: _T2) -> coroutine[Any, Any, _T]: ...
+    def aclose(self) -> coroutine[Any, Any, None]: ...
 
 class instancemethod(object):
     __slots__ = []

pytype/stubs/builtins/typing.pytd

@@ -556,11 +556,13 @@ class AsyncContextManager(Generic[_T], Protocol):
 class AsyncGenerator(AsyncIterator[_T], Generic[_T, _T2]):
   __slots__ = []
   @abstractmethod
-  def asend(self, value: _T2) -> Awaitable[_T]: ...
+  def __anext__(self) -> Coroutine[Any, Any, _T]: ...
   @abstractmethod
-  def athrow(self, typ: Type[BaseException], val = ..., tb = ...) -> Awaitable[_T]: ...
+  def asend(self, value: _T2) -> Coroutine[Any, Any, _T]: ...
   @abstractmethod
-  def aclose(self) -> Awaitable[_T]: ...
+  def athrow(self, typ: Type[BaseException], val = ..., tb = ...) -> Coroutine[Any, Any, _T]: ...
+  @abstractmethod
+  def aclose(self) -> Coroutine[Any, Any, None]: ...
 
 TYPE_CHECKING = ...  # type: bool
 

pytype/tests/test_async_generators.py

@@ -401,6 +401,20 @@ def g(i: Awaitable[str]): pass
         },
     )
 
+  @test_utils.skipBeforePy((3, 10), "New in 3.10")
+  def test_async_gen_coroutines(self):
+    self.Check("""
+      from typing import Any, AsyncGenerator, Coroutine
+      async def gen():
+          yield 42
+
+      x0: AsyncGenerator[int, None] = gen()
+      x1: Coroutine[Any, Any, int] = gen().__anext__()
+      x2: Coroutine[Any, Any, int] = gen().asend(None)
+      x3: Coroutine[Any, Any, int] = gen().athrow(BaseException)
+      x4: Coroutine[Any, Any, None] = gen().aclose()
+    """)
+
 
 if __name__ == "__main__":
   test_base.main()