Declaration order of svelte 4 slot variables broken in Svelte 5.38+ when using `@const` directive

[psyirius]

Describe the bug

Svelte 4 slots using inline @const declaration resulting in error at runtime
Cannot access 'index' before initialization

<div slot="item" let:index let:style {style}>
	<!-- This results in error: ❌ -->
	<!-- `Cannot access 'index' before initialization` -->
	{@const item = list[index]}
	XOXO: {item}
	
	<!-- This works ✅ -->
	XOXO: {list[index]}
</div>

Reproduction

<div slot="item" let:index let:style {style}>
	<!-- This works ✅ -->
	XOXO: {list[index]}
</div>

Emits:

<div slot="item" let:index let:style {style}>
	<!-- This results in error: ❌ -->
	<!-- `Cannot access 'index' before initialization` -->
	{@const item = list[index]}
	XOXO: {item}
</div>

Emits:

Here, const is emitted before any slot variable declaration

Here is an example project:
https://svelte.dev/playground/69d51ef1910347c4823c3e1c201d90f6?version=5.38.0

Logs

Cannot access 'index' before initialization in <unknown> in VList.svelte in App.svelte in

System Info

irrelevant

Severity

blocking an upgrade

[psyirius]

Here's my Svelte 5 fix using snippets in your own code. (but it affects svelte packages)

<div slot="item" let:index let:style {style}>
	<!-- This results in error: ❌ -->
	<!-- `Cannot access 'index' before initialization` -->
	{@const item = list[index]}
	XOXO: {item}
</div>

to

{#snippet item({ index, style })}
    {@const item = list[index]}

    <div {style}>
        XOXO: {item}
    </div>
{/snippet}