[ruff] Do not report when Optional has no type arguments (RUF013)

[InSyncWithFoo]

Summary

Resolves #13833.

Test Plan

cargo nextest run and cargo insta test.

[github-actions]

ruff-ecosystem results

Linter (stable)

✅ ecosystem check detected no linter changes.

Linter (preview)

✅ ecosystem check detected no linter changes.

[MichaReiser]

Thank you for looking into this issue.

The check looks good to me, but I think we should move it into type_hint_explicitly_allows_none so that Annotated[Optional, "bla"] also works

[henryiii]

I'm confused, bare Optional still isn't a valid type annotation for type checkers, isn't it? Optional would be Optional[Any], which expands to Union[None, Any], but a Union with Any is just Any. I thought the problem was the suggested fix, Optional[Optional] was nonsense. Optional[Any] would make more sense and I believe type checkers are okay with that (even if it's no different than just Any).

[charliermarsh]

That’s correct but seems outside the scope of the rule? Like a bare Optional being invalid should be its own rule.

[henryiii]

Ah, yes, that makes sense.