Svelte 5: `Cannot reassign or bind to each block argument in runes mode.` What should I use instead?

[frederikhors]

Describe the bug

In Svelte 4 app I was using:

{#each players || [] as player, i}
    <FormPlayer index={i} bind:player />
{/each}

Now with Svelte 5 it errors with:

Cannot reassign or bind to each block argument in runes mode. Use the array and index variables instead (e.g. `array[i] = value` instead of `entry = value`)

Why?

Should I use the below instead?

{#each players || [] as player, i}
    <FormPlayer index={i} bind:player={players[i]} />
{/each}

Also if I use the latter one player is unused and I get the ts warning:

'player' is declared but its value is never read. ts(6133)

Plus, with the latter one I get another typscript warning:

'players' is possibly 'null' or 'undefined'. ts(18049)

even if I'm already inside an {#each players.

There is no docs on this on https://svelte-5-preview.vercel.app/docs, right?

System Info

`"svelte": "5.0.0-next.120"`

Severity

blocking an upgrade