from abc import ABC, abstractmethod from typing import AsyncIterator, Protocol class BaseClass(ABC): @abstractmethod async def async_generator(self) -> AsyncIterator[int]: raise NotImplementedError class SubClass(BaseClass): async def async_generator(self) -> AsyncIterator[int]: yield 1 # -> Error message: Return type "AsyncIterator[int]" of "async_generator" incompatible with return type "Coroutine[Any, Any, AsyncIterator[int]]" in supertype "BaseClass" class PBaseClass(Protocol): async def async_generator(self) -> AsyncIterator[int]: pass class PSubClass(PBaseClass): async def async_generator(self) -> AsyncIterator[int]: yield 1 # -> Error message: Return type "AsyncIterator[int]" of "async_generator" incompatible with return type "Coroutine[Any, Any, AsyncIterator[int]]" in supertype "PBaseClass"  **Your Environment** - Mypy version used: 1.5.1 - Mypy command-line flags: `mypy --ignore-missing-imports --config-file tox.ini $src` - Mypy configuration options from `mypy.ini` (and other config files):