class XUEntityProperty<EntityType>: NSObject {
}

class XUPrimitiveValueProperty<EntityType: NSObject, ValueType>: XUEntityProperty<EntityType> {
}

class XUArrayProperty<EntityType: NSObject, ItemType: NSObject>: XUPrimitiveValueProperty<EntityType, Array<ItemType>> {

        // Error: 'unowned' may only be applied to class and class-bound protocol
        // types, not '(XUArrayProperty<EntityType, ItemType>) -> () -> 
        // XUArrayProperty<EntityType, ItemType>'
    var validator: ((EntityType, ItemType) -> Bool) = { [unowned self] (_, _) -> Bool in
        return true
    }
    
}

class Foo {
        // Error: Use of unresolved identifier 'self'
    var validator: () -> Bool = { [unowned self] in
        return true
    }
}