Svelte 5: Misleading errors on non-existent sub-runes outside of Svelte files

[brunnerh]

Describe the bug

If a sub-rune like $state.x() does not exist, the error in a .svelte.js file states:

rune_outside_svelte
The $state rune is only available inside .svelte and .svelte.js/ts files

(Same for other runes like $effect, found via the now missing $effect.active().)

Reproduction

// test.svelte.js
export let count = $state.x({ value: 0 });

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Logs

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System Info

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Severity

annoyance