UP045 fixes None | Optional[None | int] to None | None | int | None #23429
Description
Summary
The underlying issue behind #18508 still exists. The following example is contrived, but it implies that the implementation of non-pep604-annotation-optional (UP045) doesn’t properly model the rules of None and |, instead special-casing specific patterns.
$ cat >up045.py <<'# EOF'
from typing import Optional
foo: None | Optional[None | int] = None
# EOF
$ ruff --isolated check --select UP045 up045.py --target-version py313 --fix
Found 1 error (1 fixed, 0 remaining).
$ cat up045.py
from typing import Optional
foo: None | None | int | None = None
$ python3.13 up045.py 2>&1 | tail -n 1
TypeError: unsupported operand type(s) for |: 'NoneType' and 'NoneType'Version
ruff 0.15.1 (a2f11d2 2026-02-12)