Invalidating functions cannot be declared as @const (continuation)

[molily]

Describe the bug

I believe this is a continuation of #7843.

The problem seems to be fixed for the original case but it still appears in 4.2.0 when there is a function that does not use the loop variable.

Thanks a lot for looking into this!

Reproduction

https://svelte.dev/repl/d573469069254061b887fb45cc3f0d18?version=4.2.0

<script>
  const items = [1, 2, 3, 4, 5, 6];

  /** @type {number | undefined} */
  let highlightedItem = undefined;
</script>

{#each items as item}
  {@const highlight = () => {
    highlightedItem = item;
  }}
  {@const unhighlight = () => {
    highlightedItem = undefined;
  }}
  <button
    on:pointermove={highlight}
    on:pointerleave={unhighlight}
  >
    {item}
  </button>
{/each}

<p>
  Highlighted: {#if highlightedItem !== undefined}{highlightedItem}{:else}n/a{/if}
</p>

Note: I understand that unhighlight probably should not be in the loop scope in this simple example. Nonetheless, this should not throw a runtime error in my opinion.

Logs

App.svelte:20 Uncaught ReferenceError: $$invalidate is not defined
    at HTMLButtonElement.constants_1 (eval at handle_message (about:srcdoc:21:8), <anonymous>:757:4)
    at HTMLButtonElement.eval (eval at handle_message (about:srcdoc:21:8), <anonymous>:796:73)

here:

const constants_1 = () => {
  $$invalidate(0, /*highlightedItem*/ child_ctx[0] = undefined);
};

---

For comparison, the first function is hoisted to instance and passed through the ctx:

const func = item => {
  $$invalidate(0, highlightedItem = item);
};

return [highlightedItem, items, func];

Call site:

const constants_1 = function func() {
  return /*func*/ ctx[2](/*item*/ child_ctx[3]);
};

The second (failing) function does not use the loop item variable. Probably that is why it is not treated the same?

System Info

REPL / Chrome & Firefox

Severity

annoyance

[dummdidumm]

Fixed in Svelte 5