fix: error for rune usage in {@const} tag initialization

[paoloricciuti]

Closes #15042

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[Rich-Harris]

preview: https://svelte-dev-git-preview-svelte-15044-svelte.vercel.app/

this is an automated message

[github-actions]

Playground

pnpm add https://pkg.pr.new/svelte@15044

[dummdidumm]

should we start with the more generic "rune X cannot be used here" errors that already exist? that way we don't need to invent another error code

[paoloricciuti]

Oh i knew we had an error like this...i tried to search for it and miserably failed 😄

[paoloricciuti]

Oh actually we don't have a generic one...we only have specific ones (i think)...i'll check better after TWIS!

[paoloricciuti]

Yeah confirmed there's no generic rune X cannot be used here...should we create a generic error like this instead of the specific one?

[dummdidumm]

My thinking was that you check which rune it is and then throw one of the more specific "X can only be used at ..." errors - I haven't checked the error message itself though, so if you find that's not possible then yes maybe a more generic error message.

[paoloricciuti]

Yeah the other error messages are very specific... I'll create a rune_cannot_be_used error

[svelte-docs-bot]

Preview: https://svelte-dev-git-preview-svelte-15044-svelte.vercel.app/

[Rich-Harris]

This doesn't seem right to me. It should be totally fine to do this for example:

{#snippet test()}
  {@const der = $state.snapshot(blah)}
{/snippet}

Let's just fix up the existing logic around state_invalid_placement so that variable declarations inside {@const ...} tags are excluded

[Rich-Harris]

Opened #15115

[theonlypwner]

This doesn't seem right to me. It should be totally fine to do this for example:

{#snippet test()}
  {@const der = $state.snapshot(blah)}
{/snippet}

Let's just fix up the existing logic around state_invalid_placement so that variable declarations inside {@const ...} tags are excluded

@Rich-Harris this seems to be disallowed in 5.19.3

[Rich-Harris]

no it isn't

[theonlypwner]

never mind, I clicked your original link and saw "running Svelte compiler version 5.19.3" in the console but forgot to look at the URL, which contained version=pr-15044