Open
Description
I have something like the following code:
from typing import Any, Union
class A:
pass
class B(A):
def __init__(self):
self.member = 1
class C(A):
def __init__(self):
self.member = 2
def f(obj: A) -> int:
if isinstance(obj, B):
pass
elif isinstance(obj, C):
pass
else:
raise ValueError()
return obj.member
mypy claims:
test.py:25: error: "A" has no attribute "member"
However, at line 25, it's clear that obj must be either a B or a C. If I remove the elif isinstance(obj, C) branch, then there is no error.
This similar code has a related error:
from typing import Any, Union
class A:
pass
class B(A):
def __init__(self):
self.member = 1
class C(A):
def __init__(self):
self.member = 2
def f(obj: A) -> Union[B, C]:
if isinstance(obj, B):
pass
elif isinstance(obj, C):
pass
else:
raise ValueError()
return obj
test.py:25: error: Incompatible return value type (got "A", expected "Union[B, C]")
Interestingly, if I remove the inheritance so that B and C are no longer subclasses of A, there is no error.
This happens on mypy 0.570 and current git (0.590-dev-3346cfad75374c096b1dd8024df24ce50f18a35c).