Summary

Consider the following snippet. ty, mypy, pyright and pyrefly all agree on the type of B1().x, but ty disagrees with the other three on the type of B2().x:

class A:
    x: int

class B1(A):
    x: bool

class B2(A):
    def __init__(self) -> None:
        self.x: bool = True


reveal_type(B1().x)  # Ty, mypy, pyright, pyrefly: bool
reveal_type(B2().x)  # Mypy, pyright, pyrefly: bool. Ty: int!

• Ty
• Pyright
• Mypy
• Pyrefly

I think for compatibility, it would be better if we followed what the other type checkers do here.

I spotted this by looking at the ecosystem report in astral-sh/ruff#20723 (comment) (all 4 new unresolved-attribute errors on aiohttp in the ecosystem report are caused by this).

Version

No response