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error: Return type of <functionName> incompatible with supertype <ClassName> #3576
Description
I got a code that looks like this:
from typing import NamedTuple, Dict, Optional, List, Any
class Object1(object, metaclass=ABCMeta):
def __init__(self) -> None:
pass
@abstractmethod
def get_logo(self) -> Optional[str]:
pass
class Object2(Object1):
def __init__(self) -> None:
super().__init__()
async def get_logo(self) -> Optional[str]:
return ''
class Object3(Object1):
def __init__(self) -> None:
super().__init__()
async def get_logo(self) -> Optional[str]:
return None
And the mypy alerts me that:
test.py:19: error: Return type of "get_logo" incompatible with supertype "Object1"
test.py:27: error: Return type of "get_logo" incompatible with supertype "Object1"
But it's look OK to me, because they return the same type...
I run it with: mypy --strict-optional --ignore-missing-imports <file>
Activity
JukkaL commentedon Jun 20, 2017
Objectdoesn't useasync defbut subclasses use it, so the actual return types are different, though the annotations look the same.YuvalPruss commentedon Jun 20, 2017
Great! It's corrects my errors, but let me get that straight- what is the difference in the type annotations between
async defanddef? Should I wrote something differently? Maybe use thetyping.Coroutineas the returned type from theasync defs?JukkaL commentedon Jun 20, 2017
Mypy internally uses
typing.Awaitable[x]as the return type forasync def, but this wrapping happens automatically so your signatures are fine. You can usereveal_type(obj.method)to display the signature of a method as mypy sees it.