Describe the bug

This involves migration of a project to svelte 5. When Typescript compilation occurs after migration of components, the following type check error happens. Svelte 4 did not have this error and all the props were strictly verified.

Reproduction

• Clone https://github.com/Jojoshua/svelte5-issue1
• Run npm i
• Run npx tsc --noEmit

Another related issue for reference #14966

Logs

System Info

System:
    OS: Windows 11 10.0.26100
    CPU: (16) x64 AMD Ryzen 7 9800X3D 8-Core Processor
    Memory: 20.82 GB / 31.02 GB
  Binaries:
    Node: 22.13.1 - C:\Program Files\nodejs\node.EXE
    npm: 10.9.2 - C:\Program Files\nodejs\npm.CMD
  Browsers:
    Edge: Chromium (131.0.2903.112)

Severity

blocking an upgrade