Parse failure: await isn't allowed in non-async function when using await with @const inside svelte:boundary

[yuki0418]

Describe the bug

Similar to #16811

<script>
  async function getOne() {
    return 1;
  }
</script>

<svelte:boundary>
	{@const one = await getOne()}
</svelte:boundary>

However, with pending snippet, it works.

<script>
  async function getOne() {
    return 1;
  }
</script>

<svelte:boundary>
	{@const one = await getOne()}
        {#snippet pending()}
		<p>loading...</p>
	{/snippet}
</svelte:boundary>

Reproduction

https://www.sveltelab.dev/bz2hl12ptw022ry

Logs

[vite] (ssr) Error when evaluating SSR module /src/routes/+page.svelte: Parse failure: await isn't allowed in non-async function
At file: /src/routes/+page.svelte:17:17
  File: /src/routes/+page.svelte:17:17
  15 |  
  16 |                          {
  17 |                                  const one = (await $.save(getOne()))();
     |                   ^
  18 |                          }
  19 |

System Info

N/A

Severity

blocking an upgrade