Repository navigation
First overload picked overeagerly when overloading on self type #14070
Description
Consider this example:
from typing import Generic, TypeVar, Any, overload
AnyStr = TypeVar("AnyStr", str, bytes)
class Popen(Generic[AnyStr]):
@overload
def communicate(self: Popen[str], buf: str = ...) -> float: ...
@overload
def communicate(self: Popen[bytes], buf: memoryview | bytes = ...) -> range: ...
def communicate(self, buf: object = None) -> Any: raise NotImplementedError
p = Popen()
reveal_type(p.communicate())This currently reveals float. I think it should either be the union float | range or Any. This came up in python/typeshed#9100.
Activity
mr-c commentedon Feb 5, 2025
I can confirm that this is still an issue with mypy 1.15, especially for mypyc users when
subprocess.Popen(or similar) is called withstdout=subprocess.DEVNULLilevkivskyi commentedon Sep 20, 2026
Btw I think a bigger issue (in this particular example) is that we randomly choose first constraint when a type argument is not given instead of
Any(i.e.reveal_type(p)givesPopen[str]in this example). Changing this may be risky, but something that we could potentially try at some point.The overload selection part will be fixed by #22011 when it is ready.