mypy seems to lose the type of an async AsyncIterator function that overrides a superclass #12662
Description
Getting this both with 0.942 as well as latest master:
from typing import AsyncIterator from typing import Sequence class AsyncResultWorking: "a class with two async methods." async def _some_impl(self) -> str: ... async def partitions(self) -> AsyncIterator[str]: ... class AsyncResultBroken: """a class with the identical two async methods as AsyncResultWorking, but the 'partitions' method is now implemented.""" async def _some_impl(self) -> str: ... async def partitions(self) -> AsyncIterator[str]: while True: partition = await self._some_impl() if partition: yield partition else: break class AsyncResultSubclassWorking(AsyncResultWorking): """subclassing the working class is fine""" async def partitions(self) -> AsyncIterator[str]: ... class AsyncResultSubclassBroken(AsyncResultBroken): """subclassing the broken class expresses confusion over the 'partitions' method signature. """ async def partitions(self) -> AsyncIterator[str]: ...error:
test3.py:43: error: Return type "Coroutine[Any, Any, AsyncIterator[str]]" of "partitions" incompatible with return type "AsyncIterator[str]" in supertype "AsyncResultBroken" [override] Found 1 error in 1 file (checked 1 source file) if you remove the implementation from AsyncResultBroken.partitions, then it passes. So, I'm wondering am I not using AsyncIterator correctly? but if I'm not, neither mypy nor pyright are saying anything. Also, even if the method body of partitions were wrong, the signatures match exactly.