Svelte 5: Use index as key breaks each block

[Thiagolino8]

Describe the bug

Simply using index does not change anything in the code, but if you use index in the key in some other way it adds a function but does not provide the index for that function

Reproduction

https://svelte-5-preview.vercel.app/#H4sIAAAAAAAAChWMQQqDMBAAv7Jse2hBEHoMpdB3NILBrHUhicFEoSz795rjDMwIzhyooPkIJhcJDb5zxg7rLzcoB4VKJ5d136Zm5EJuWkACpW9dDDwUXAGuFDtguI1XYR3vapOtT89H_7JJ-pboeYmr55nJo6nbTjroH6WtwoOAAAAA

Logs

No response

System Info

App.svelte (Svelte v5.0.0-next.22)

Severity

blocking an upgrade

[Conduitry]

There are a couple things going on here. One is that your code isn't using the index as the key, it's using the literal string i. Your component doesn't work in Svelte 4 either. If you use (i) instead, it works in both 4 and 5

I do think the error message in Svelte 5 is wrong, though. It should say 'i', not 'undefined'.

[Thiagolino8]

There are a couple things going on here. One is that your code isn't using the index as the key, it's using the literal string i. Your component doesn't work in Svelte 4 either. If you use (i) instead, it works in both 4 and 5

I do think the error message in Svelte 5 is wrong, though. It should say 'i', not 'undefined'.

Yes, the code was incorrect but the problem is real, I edited the issue to include the correct screenshot and repl
I had this problem in a real app and when creating a simplified repl I ended up writing it wrong