Svelte 5: two TS quirks

[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 I need to use:

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

But now 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}.

[jasonlyu123]

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

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

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

This is because TypeScript doesn't narrow the type like this. It's not something we can fix. You can move the players || [] part to another derived/reactive variable so it'll always be not nullable, or use the ! operator to tell TS "I know what I'm doing this is not null" (now possible in SVelte 5): bind:player={players![i]}