Svelte 5: Using CSS selector function fails if they contain new line

[minht11]

Describe the bug

Following code snippet fails in svelte 5, but works in svelte 4.

<style>
	:is(
		button
	) {
		background: blue;
	}
</style>

Reproduction

Svelte 4 works
Svelte 5 fails

Logs

Expected a valid CSS identifier

System Info

no need

Severity

annoyance