Q_ENUM_NS without Q_DECLARE_METATYPE doesn't work

#include <QQuickItem>

namespace Data {
   Q_NAMESPACE
   QML_ELEMENT
   enum DType {
     A, B
   };
  Q_ENUM_NS(DType)
} // namespace Data

//Q_DECLARE_METATYPE(Data::DType)   

class MyItem : public QQuickItem
{
private:
    Q_OBJECT
    QML_ELEMENT
 public:
    MyItem();
    Q_INVOKABLE void setDType(Data::DType) {}
};

import QtQuick 2.15
import QtQuick.Window 2.15
import example.mylib 1.0

Window {
    width: 640
    height: 480
    visible: true
    title: qsTr("Hello World")
    
    Component.onCompleted: {
        myItem.setDType(0);
    }
    MyItem {
        id: myItem
    }
}