Shadowed variable breaks `{#await}` block

[GauBen]

Describe the bug

Hey! I just found a new bug

This does not work:

<script>
	const x = Promise.resolve(10)
</script>

<div>
	{#await x}
		Loading...
	{:then x}
		{x}
	{/await}
</div>

Not shadowing x fixes the issue:

	{:then y}
		{y}
	{/await}

Thanks!

Reproduction

• Broken: https://svelte-5-preview.vercel.app/#H4sIAAAAAAAACkWOwQrCMAyGX2XEi4J0ei1T8O7Bu_VQ1kwDW1vabCql7-46QW_58uf7SYKOeowgrwmsHhAknLyHLfDbF4gT9owzRzeGtmya2AbyfFRWcets5OpVHapLcANFFAGj6ydc73cbZZv6f2sbQ9MipZV-apq1XEjx2WlD9i6EWFLJD7S_MH2HVC9OLp2lZ35ocIY6QgOSw4j5lj-ei6sdywAAAA==
• Working: https://svelte-5-preview.vercel.app/#H4sIAAAAAAAACkWOwQrCMAyGX6XEi4Jsei1T8O7Bu_VQ1qiBrS1tNh2l7-46BW_58uf7SYI7dRhBXhNY3SNIOHkPW-DJF4gjdowzRzeEtmya2AbyfFRWcetsZPEWB3EJrqeIVcDouhHX-91G2ab-39rG0LhIaaVfmmYtF1J8dtqQfVRVtaSSn2jF9AvTd0j14uTSWXrmh3pn6E5oQHIYMN_yB-P8rHbLAAAA

Logs

No response

System Info

Svelte 5 next 229

Severity

blocking an upgrade

[GauBen]

I'd love to submit a fix for this bug but I'm not really sure what needs to be changed. My understanding so far is that we run context.visit(node.then) before context.visit(node.expression), making the parser thinks x already exists in the scope. How can I declare two different scopes?

[GauBen]

I tried my best 😄

[Rich-Harris]

closed by #12945