[pyupgrade] Don't introduce invalid syntax when upgrading old-style type aliases with parenthesized multiline values (UP040)

[AlexWaygood]

Summary

We previously autofixed this:

from typing import TypeAlias

T: TypeAlias = (
    int
    | str
)

to this:

type T = int
    | str

When we should be autofixing it to this:

type T = (
    int
    | str
)

This PR fixes the bug. Closes #16023

Test Plan

New fixture added that repros the issue on main.

[AlexWaygood]

I think this is a small regression from #15840 (cc. @ntBre) -- totally one I should have caught in review, though!

[github-actions]

ruff-ecosystem results

Linter (stable)

✅ ecosystem check detected no linter changes.

Linter (preview)

✅ ecosystem check detected no linter changes.

[InSyncWithFoo]

This might be a good test case to add:

T: TypeAlias = (  # This comment should not make the fix unsafe
	int | str
)

[AlexWaygood]

Thanks! However, all fixes for this rule are unsafe (because you can't use PEP-695 type aliases as the second argument in isinstance() calls, whereas you can with old-style type aliases that use TypeAlias)

[InSyncWithFoo]

However, all fixes for this rule are unsafe

Aren't they safe in stubs?

[AlexWaygood]

Aren't they safe in stubs?

hmm, good point. Want to make a followup PR?

[InSyncWithFoo]

Sure. I'm ready whenever you are.

[ntBre]

Sorry about that! Thanks for the quick fix! I don't have anything to add on top of the other reviews, LGTM.