Using default parameters object and destructuring, results in error: Assigning to rvalue

[enyo]

Describe the bug

This code in the typescript block of a svelte component fails:

  const increment = ({ increment } : { increment?: number } = {}) => {
    count += 1
  }

with error Assigning to rvalue svelte(js_parse_error)

Workarounds:

• Removing the default object
• Removing the destructuring: (params: { increment?: number } = {})
• Removing the type annotation: ({ increment } = {})

Reproduction

https://stackblitz.com/edit/vitejs-vite-dcqkxf?file=src%2Flib%2FCounter.svelte%3AL7

Logs

No response

System Info

Latest Svelte 5 version

Severity

annoyance

[Conduitry]

Likely to be the same sort of thing as #13409, which is blocked by the upstream acorn-typescript, which no longer seems to be maintained, and which we'll probably have to fork and take over maintenance of at some point.

[harrisi]

Another workaround, you can use a normal function:

function increment({ increment }: { increment?: number } = {}) {
  count += 1
}