Can I use the @preconcurrency directive and still build on Xcode 15?

Yes, you can use the @preconcurrency directive and still build on Xcode 15. The @preconcurrency attribute is used to mark code that was written before Swift's concurrency model was introduced, and it helps the compiler understand how to handle such code in a concurrency-safe manner.

However, if you are migrating to Swift 6 and enabling strict concurrency checking, you might encounter warnings related to the @preconcurrency attribute. For example, in the session "Migrate your app to Swift 6," it is mentioned that once the compiler can see that a protocol is guaranteed to be on the main actor, it may warn that the @preconcurrency attribute is no longer needed, and you can remove it (Migrate your app to Swift 6).

For more details on how to handle concurrency and the @preconcurrency attribute in Swift 6, you can refer to the session "Migrate your app to Swift 6," particularly the chapters on enabling complete checking and handling delegate callbacks and concurrency.

Relevant Sessions

1. What’s new in Xcode 16
2. Migrate your app to Swift 6