Svelte 5 migration script: Props TS interface is reduced to `{ [key: string]: any }` when `$$restProps` is used

[gwennlbh]

Describe the bug

A component that uses {...$$restProps} is migrated to svelte 5 with

interface Props { [key: string]: any; }

instead of something like

interface Props {
      prop1: string;
      /** docs for prop2 */
     prop2: number;
     [key: string]: any;
}

This way of defining the interface works really well, see an example is the TS playground

Reproduction

Svelte 5 REPL -- click "MIGRATE" on the Example.svelte component

Logs

No response

System Info

(https://svelte-5-preview.vercel.app)

Severity

blocking an upgrade