MOC does not generate output for `using` keyword in namespace

enum class PingDeviceType {
    UNKNOWN = 0,
};

namespace PingDeviceTypeNamespace {
Q_NAMESPACE
    using ::PingDeviceType;
    enum Enum {
        TestA = 1,
    };
    enum class EnumClass {
        TestB = 2,
    };
Q_ENUM_NS(PingDeviceType)
Q_ENUM_NS(Enum)
Q_ENUM_NS(EnumClass)
}

static const qt_meta_stringdata_PingDeviceTypeNamespace_t qt_meta_stringdata_PingDeviceTypeNamespace = {
    {
QT_MOC_LITERAL(0, 0, 23), // "PingDeviceTypeNamespace"
QT_MOC_LITERAL(1, 24, 4), // "Enum"
QT_MOC_LITERAL(2, 29, 5), // "TestA"
QT_MOC_LITERAL(3, 35, 9), // "EnumClass"
QT_MOC_LITERAL(4, 45, 5) // "TestB"

    },
    "PingDeviceTypeNamespace\0Enum\0TestA\0"
    "EnumClass\0TestB"
};
#undef QT_MOC_LITERAL

static const uint qt_meta_data_PingDeviceTypeNamespace[] = {

 // content:
       8,       // revision
       0,       // classname
       0,    0, // classinfo
       0,    0, // methods
       0,    0, // properties
       2,   14, // enums/sets
       0,    0, // constructors
       4,       // flags
       0,       // signalCount

 // enums: name, alias, flags, count, data
       1,    1, 0x0,    1,   24,
       3,    3, 0x2,    1,   26,

 // enum data: key, value
       2, uint(PingDeviceTypeNamespace::TestA),
       4, uint(PingDeviceTypeNamespace::EnumClass::TestB),

       0        // eod
};