svelte 5: Can't use destructuring with @const and use the value inside an event handler

[bfanger]

Describe the bug

<script>
  let structured = $state({ handler() {} })
</script>

{#if structured}
  {@const { handler } = structured}

  <button onclick={() => handler()}>click me</button>
{/if}

Generates a corrupted component which fails with Error: handler is not defined
This is due to the generated code:

const computed_const = $.derived(() => {
  const { handler } = structured;

  return { handler };
});

button.__click = [on_click, handler];

where handler is not available outside the lexical scope of the derived closure.

Reproduction

REPL

Logs

Error: handler is not defined

System Info

svelte: 5.0.0-next.40
generate: "client"

Severity

blocking an upgrade