Running into this new issue in beta 3. All of our immutable model attributes are now triggering swift compiler error from the title (tied to swift 6 - warning in swift 5). Neither warning or error show up on previous builds. Anyone else running into this? Hopefully not a limitation on swiftData that attributes must be mutable? filed as: FB14379932 (new in Xcode 16 beta3: "cannot expand accessors on variable declared with 'let'" in SwiftData Models)

Posting here to see if folks have workarounds or if I have a misunderstanding of SwiftData supported types. In adopting SwiftData, I have swiftData properties of collection type (Array or Set - both have this issue). E.g: @Model final class Item { var timestamp: Date var strings = ["aa", "bb"] var display: String { strings.joined(separator: " ") } init(timestamp: Date) { self.timestamp = timestamp } } So far in development I haven't had issues on iOS 17, but on the iOS 18 betas 4-5 the app logs show the following error: "fault: Could not materialize Objective-C class named "Array" from declared attribute value type "Array<String>" of attribute named strings" It happens immediately in my app when creating an object with a collection attribute. In a minimal test example, the error log appears only after a few minutes and doesn't seem to affect the template app's basic functionality. Anyone else running into this? Was filed as FB14397250