Sibling Combinator combined with `:has` can be improperly marked as unused

[craig-jennings]

Describe the bug

I've got some complex sibling combinator + :has css selectors that match the DOM but are reported as unused by Svelte. Through further testing, it appears that some trivial cases are incorrectly marked as unused.

Reproduction

1. Open ./packages/svelte/tests/css/samples/has/input.svelte
2. Add the following code to the bottom of the style block

x:has(+ c) {
  color: green;
}

x:has(~ c) {
  color: green;
}

Notice that these are valid selectors based on the given DOM structure

3. Run the test. It now fails with 2 css_unused_selector errors. I've found that wrapping c in :global() seems to get rid of the errors, but I'm not sure if that should be required to get this selector working.

Logs

No response

System Info

Svelte Version - 5.1.6

Severity

annoyance

[thebjorn]

Here is a REPL for a common use case:

<div class="form-field">
	<label for="a">label</label>
	<input id="a" type="text" required>
</div>

<style>
	label:has(+ [required])::after {
		content: '*';
	}
</style>

[johannesmutter]

@dummdidumm Could we please reopen?

Sibling :has() selectors are still reported as unused and rules don't apply (unless wrapped in :global(). Please see below basic example:

<section class="list">
	<div class="list-item">should be red</div>
	<div class="list-item"><h2>heading</h2></div>
	<div class="list-item">...</div>
</section>

/* reported as unused */
.list-item:has( + .list-item h2) {
    background: red ;
}

/* works only with global */
:global(.list-item:has( + .list-item h2)) {
    background: red ;
}

Tested in: Svelte Version: svelte@5.2.7

REPL

(I upgraded from 5.0.0-next.260 to svelte@5.2.7, in 260 this was not an issue)