Summary

Fixes #10340.

Currently, ruff emits no F821 rules on the following .py file, but the lines marked with XXX all fail at runtime due to undefined names, despite from __future__ import annotations being active:

from __future__ import annotations

from typing import TypeAlias, Optional, Union

MaybeCStr: TypeAlias = Optional[CStr]  # XXX
MaybeCStr2: TypeAlias = Optional["CStr"]  # always okay
CStr: TypeAlias = Union[C, str]  # XXX
CStr2: TypeAlias = Union["C", str]  # always okay

class C: ...

class Leaf: ...
class Tree(list[Tree | Leaf]): ...  # XXX
class Tree2(list["Tree | Leaf"]): ...  # always okay

This PR fixes that.

Much like #10341, it took me an annoying amount of time to figure out how to fix this, but it turned out to be hilariously easy to fix once I saw where to make the change 🙃

Test Plan

cargo test