Svelte 5: Syntax error on snippets with inline typing with optional properties

[7nik]

Describe the bug

Syntax error on snippets with inline typing with optional properties.

<script lang="ts"></script>
{#snippet snip({a}: {a?: string})} <!-- Error: Expected token ) -->
  {a}
{/snippet}

Reproduction

REPL

Logs

No response

System Info

Svelte 5.0.0-next.157

Severity

annoyance

[paoloricciuti]

The problem is this line:

svelte/packages/svelte/src/compiler/phases/1-parse/read/context.js

Line 127 in cabdf97

parser.template.slice(parser.index).replace(/\?\s*:/g, ':');

it replace ?: with : and that works fine for optional function parameters but it messes with non optional function parameters that have an optional field in them (i assume the same is true for functions types too).

[paoloricciuti]

This will basically break whenever theere's one or more ?: in the type itself. So this

<script lang="ts"></script>
{#snippet snip(a: "cool?:")}
  {a}
{/snippet}

is also broken

[paoloricciuti]

This should be fixed by #12070 (the repl seems fine now)