Xcode 15 b2 Dispatch has been broken

Hi,

Sorry to hear you are having problems getting previews working as expected. What you are encountering here is a known issue in Seed 2. From the release notes:

#Preview can’t reference symbols in Swift type extensions when they are defined in the same module as the Preview (110671628)

Workaround: Revert to using PreviewProvider, or copy the implementation of the extension directly in to the #Preview itself or make it a global symbol