False positive: redis.async.PubSub.listen() #8960

Stub for redis.async.PubSub.listen():

Actual Implementation:

    async def listen(self) -> AsyncIterator:
        """Listen for messages on channels this client has been subscribed to"""
        while self.subscribed:
            response = await self.handle_message(await self.parse_response(block=True))
            if response is not None:
                yield response

Even though signatures are equivalent, mypy interprets the stub to be a coroutine that returns an AsyncIterator.

For example, this is runtime valid, but mypy finds an error:

async for message in pubsub.listen():
    ...

error: "Coroutine[Any, Any, AsyncIterator[Any]]" has no attribute "__aiter__" (not async iterable) [attr-defined]

This is invalid code, but passes mypy:

async for message in await pubsub.listen():
    ...

TypeError: object async_generator can't be used in 'await' expression

References:

• false "not async iterable" on use of overload with async iterable mypy#10301 (comment)
• Must yield when declaring an AsyncIterator for a Protocol. mypy#5385 (comment)