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issubclass() doesn't narrow down types of type variables #7920
Description
Example:
from typing import *
TypeT = TypeVar("TypeT", bound=type)
class Base:
field: str = "Hey"
class C1:
def method(self, other: type) -> str:
if issubclass(other, Base):
# reveal_type(other) == Type[Base]
return other.field
return "Hi"
class C2(Generic[TypeT]):
def method(self, other: TypeT) -> str:
if issubclass(other, Base):
# reveal_type(other) == TypeT`1
return other.field # mypy error: "TypeT" has no attribute "field"
return "Hi"Actual behavior as of 0.740 included in the comments above. Expected behavior would be to not raise an error on the penultimate line.
Activity
ilevkivskyi commentedon Nov 11, 2019
Looks like an issue in
checker.py(the logic aroundissubclass()is pretty ad-hoc there). One needs to add aneliffor type variables infind_isinstance_check()there.This might potentially need also an adjustment in
meet.pyeither innarrow_declared_type()or inis_overlapping_types()or inmeet_types().TH3CHARLie commentedon Nov 11, 2019
@ilevkivskyi I'd like to take this
ilevkivskyi commentedon Nov 11, 2019
OK, go ahead.
Fix `issubclass()` to narrow down types of type variables (#7930)