bug: ts rest parameters syntax (...args) not properly parsed in Svelte components

[rxliuli]

Describe the bug

I'm trying to define an async function with rest parameters in a Svelte component using TypeScript:

<script lang="ts">
const f = async (...args: any) => {
}
</script>

Svelte's parser throws an "Unexpected token" error when trying to parse the rest parameters syntax:

Unexpected token 
https://svelte.dev/e/js_parse_error
(js_parse_error)

Reproduction

https://svelte.dev/playground/hello-world?version=5.20.0#H4sIAAAAAAAAE3WRTWvDMAyG_4owOyQQsntIArvtsEMZudU9qInSGVy5WOraUPLfh9ePrfu4ydL7SK_kk2HckqnMM3kf4BCiHyCjwSkNuSnM6DyJqZYno9Mu6VLCFFfqabcr5Z28ptwahf7K94GVWMVUppY-up2CR9401qhY01ruA4vCCA2gTNxDVpYlxo1UgDzl0LRwsmzV8my5fjy3aC1bNoVROqqpNO5pLv4xqSR6cVOq3Bv9Vftm1qonBR9wcLwRaOBBFJXqV-pDHGrR6HhTwDoET8htm53m3DLAuOdeXWA4OH17OeN1B3RU4kHut1uuPvdbxLB1QjXy1LZZagIwcgVdcY7dUH3jFhhxS0pR6q795C9ekjivoEv3Slgk3UeG7OdZfze4AHBbd-mGqz5fQQPpwleNxukLuE3BAzqFkW_YVTHD6Bi9v4P-mzOil9ug-RzMOaBAlx7z_Zev5g-1TUS9wQIAAA==

Logs

System Info

System:
    OS: macOS 15.2
    CPU: (12) arm64 Apple M2 Max
    Memory: 3.30 GB / 64.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 22.14.0 - /usr/local/bin/node
    npm: 10.9.2 - /usr/local/bin/npm
    pnpm: 10.3.0 - /usr/local/bin/pnpm
    bun: 1.1.6 - ~/.bun/bin/bun
    Watchman: 2024.12.02.00 - /opt/homebrew/bin/watchman
  Browsers:
    Brave Browser: 131.1.73.105
    Chrome: 133.0.6943.55
    Safari: 18.2

Severity

annoyance

[JeanJPNM]

This seems to be an issue with acorn. I can reproduce the issue on deno with the versions currently used by svelte of acorn and acorn-typescript:

svelte/pnpm-lock.yaml

Lines 71 to 76 in 8b97725

	acorn:
	specifier: ^8.12.1
	version: 8.12.1
	acorn-typescript:
	specifier: ^1.4.13
	version: 1.4.13(acorn@8.12.1)

// both used by svelte according to the repo's lockfile
import * as acorn from "npm:acorn@8.12.1"; 
import tsPlugin from "npm:acorn-typescript@1.4.13";

const node = acorn.Parser.extend(tsPlugin({ allowSatisfies: true })).parse(
  "const f = (...args: any) => {}",
  {
    sourceType: "module",
    ecmaVersion: 13,
    locations: true,
  }
);
console.log(node);

Produces the same error. But the problem is fixed when using acorn@8.14.0