struct WrapWithVariant
{
    Q_GADGET
    QML_VALUE_TYPE(wrappedWithVariant)
    QML_CONSTRUCTIBLE_VALUE    Q_PROPERTY(QVariant intPrimitiveValue READ intPrimitiveValue CONSTANT)
    Q_PROPERTY(QVariant undefinedPrimitiveValue READ undefinedPrimitiveValue CONSTANT)
    Q_PROPERTY(QVariant nullPrimitiveValue READ nullPrimitiveValue CONSTANT)
public:
    WrapWithVariant() = default;    QVariant intPrimitiveValue() const
    {
        return QVariant::fromValue<QJSPrimitiveValue>(QJSPrimitiveValue(12));
    }    QVariant undefinedPrimitiveValue() const
    {
        return QVariant::fromValue<QJSPrimitiveValue>(QJSPrimitiveValue(QJSPrimitiveUndefined()));
    }    QVariant nullPrimitiveValue() const
    {
        return QVariant::fromValue<QJSPrimitiveValue>(QJSPrimitiveValue(QJSPrimitiveNull()));
    }
 


// qml file
QtObject { 
    property wrappedWithVariant wrapped
    property bool primitiveIsNull: wrapped.nullPrimitiveValue === null
}