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no error when using covariant or contravariant TypeVar on class with writable attribute #14588
Closed as not planned
Description
from typing import Generic, TypeVar
T = TypeVar("T", covariant=True)
class Foo(Generic[T]):
def __init__(self, value: T) -> None:
self.foo = valuehere, T is used in both an in and out position as the value can be modified as well.
jailbreak:
objects = Foo[object](None)
ints = Foo[int](1)
def do_thing(value: Foo[object]) -> None:
value.foo = "asdf"
do_thing(ints)
if TYPE_CHECKING:
reveal_type(ints.foo) # int
print(ints.foo) # "asdf" (hacked!!!!!!)
Activity
[-]no error when using `covariant` or `contravariant` `TypeVar` on class with readable & writable attribute[/-][+]no error when using `covariant` or `contravariant` `TypeVar` on class with writable attribute[/+]hauntsaninja commentedon Feb 2, 2023
Thanks, I think this is basically just a special case of #3208
hauntsaninja commentedon Feb 2, 2023
Posted a comment in that issue, so if we ever do something about that we will also do something about this