SWC produces invalid code if types have a trailing coma

[skutyepov]

Describe the bug

If types contain a trailing coma, swc adds to the actual code, which is a syntax error.

For reference, TSC handles it correctly. TSC playground ref.

Input code

export function func({
  a,
  b,
  ...rest
}: {
  a: string,
  b: string,
}) {
 console.log(a,b, rest)
}

Config

{
  "jsc": {
    "parser": {
      "syntax": "typescript",
      "tsx": false
    },
    "target": "es2022"
  }
}

Playground link

https://play.swc.rs/?version=1.3.21&code=H4sIAAAAAAAAA0utKMgvKlFIK81LLsnMzwMzNKq5FBQSdYBEEojQ09MrSi0u4aq1UgBLWCkUlxRl5qWDFSA4tZog6eT8vOL8nFS9nPx0jUSdJB0FkFZNrloAL7Tel2gAAAA%3D&config=H4sIAAAAAAAAAxWKQQqAMAwE%2F7JnD5JjfxNKFEWkZHNoKfm79TYzzMTNijLR1Gn%2BE8cb2lEQoxmrXy2wIbjSoQ8tl6ifFmsxyi6CzA%2Br99KJSAAAAA%3D%3D

Expected behavior

SWC should not add trailing coma after ...rest

Actual behavior

SWC adds trailing coma: { a, b, ...rest,}, which isn't valid syntax

Version

1.3.21

Additional context

The issue goes away if trailing coma from types is removed.

export function func({
  a,
  b,
  ...rest
}: {
  a: string,
  b: string // (no coma here)
}) {
 console.log(a,b, rest)
}

[alexander-akait]

ts playground does the same

[skutyepov]

@alexander-akait in your example TSC produces the following error:

A rest parameter or binding pattern may not have a trailing comma.

Also, input in your example is invalid, the issue with SWC is a bit different. Given valid input, SWC produces invalid output.
Below is a screenshot that shows a difference between SWC (top) and TSC (bottom) outputs.

[alexander-akait]

Yeah, I see, let's fix it 👍

[swc-bot]

This closed issue has been automatically locked because it had no new activity for a month. If you are running into a similar issue, please create a new issue with the steps to reproduce. Thank you.