I’m trying to resolve a compilation error: Task or actor isolated value cannot be sent when using Xcode 16.0 beta 3 with Swift 6 and Complete Concurrency enabled. My code:

import SwiftUI
@preconcurrency import Contacts
import ContactsUI

struct SimpleContactPicker: View {
    
    let allowedContactType: CNContactType? = CNContactType.person
    
    @Binding var selectedContacts: [CNContact]?

    var body: some View {
        SimpleContactPickerProxy(allowedContactType: self.allowedContactType, selectedContacts: $selectedContacts)
            .ignoresSafeArea()
    }
}

extension CNContactType {
    
    var predicateForEnablingContact: NSPredicate {
        
        NSPredicate(format: "contactType=(self.rawValue)")
    }
}

struct SimpleContactPickerProxy: UIViewControllerRepresentable, @unchecked Sendable {
    
    typealias UIViewControllerType = CNContactPickerViewController
    
    let allowedContactType: CNContactType?
    
    @Binding var selectedContacts: [CNContact]?

    final class Coordinator: NSObject, CNContactPickerDelegate, @unchecked Sendable {
        var parent: SimpleContactPickerProxy

        init(_ parent: SimpleContactPickerProxy) {
            self.parent = parent
        }
        
        func contactPickerDidCancel(_ picker: CNContactPickerViewController) {
        }

        func contactPicker(_ picker: CNContactPickerViewController, didSelect contacts: [CNContact]) {
           
            Task { @MainActor in
                self.parent.selectedContacts = contacts // <<-- ERROR: Task or actor isolated value cannot be sent
            }
        }
    }
    
    func makeUIViewController(context: Context) -> CNContactPickerViewController {
        
        let contactPickerViewController = CNContactPickerViewController()
        
        contactPickerViewController.delegate = context.coordinator
        
        if let allowedContactType {
            contactPickerViewController.predicateForEnablingContact = allowedContactType.predicateForEnablingContact
        }
        
        return contactPickerViewController
    }
    
    func updateUIViewController(_ uiViewController: CNContactPickerViewController, context: Context) {
    }
    
    func makeCoordinator() -> Coordinator {
        Coordinator(self)
    }
}

While I generally understand that the [CNContact] array cannot be sent from the non-isolated context to the MainActor context because CNContact is non-Sendable, it’s unclear how to work around this problem. (This issue did not appear in earlier Xcode 16 betas).

I guess it’s possible to create my own CNContact facsimile struct with copied data, but this seems like an annoying amount of overhead. I also tried MainActor.assumeIsolated and other strategies discussed in this WWDC 2024 Swift Concurrency video https://developer.apple.com/wwdc24/10169, but none of these approaches appeared to work.

Any help is appreciated.