PropertyWrapper: Delegate updates similar to SwiftUIs ObservableObject/Published combo

Delegate.swift

public protocol DelegateProvider: AnyObject {
    static func notifyDelegate(_ instance: Self)
}

@propertyWrapper
public struct Delegate<Value> {
    public var wrappedValue: Value

    public init(wrappedValue: Value) {
        self.wrappedValue = wrappedValue
    }

    public static subscript<Instance: DelegateProvider>(
        _enclosingInstance instance: Instance,
        wrapped wrappedKeyPath: ReferenceWritableKeyPath<Instance, Value>,
        storage storageKeyPath: ReferenceWritableKeyPath<Instance, Self>
    ) -> Value {
        get {
            return instance[keyPath: storageKeyPath].wrappedValue
        }
        set {
            instance[keyPath: storageKeyPath].wrappedValue = newValue
            Instance.notifyDelegate(instance)
        }
    }
}

Usage.swift

// Updating any of the properties marked `@Delegate` will notify the delegate

protocol ViewModelDelegate: AnyObject {
    func viewModelUpdated(_ viewModel: ViewModel)
}

class ViewModel: DelegateProvider {
    static func notifyDelegate(_ instance: ViewModel) {
        instance.delegate?.viewModelUpdated(instance)
    }

    @Delegate private(set) var foo: Int = 0
    @Delegate private(set) var bar: String = ""
    @Delegate private(set) var baz: [Bool] = []

    weak var delegate: ViewModelDelegate? { // property wrappers dont work with `weak` :(
        didSet { Self.notifyDelegate(self) }
    }

    init() { }
}