QML fails to bind to QObject property (defined with Q_OBJECT_BINDABLE_PROPERTY and BINDABLE) that are a type Q_GADGET

import QtQuick
import QtQuick.Window
import doubleBinding 1.0
Window {
    width: 640
    height: 480
    visible: true
    title: qsTr("Hello World")
    MouseArea {
        anchors.fill: parent
        onClicked: {
            console.log("clicked")
            var time = aId.x.timeIndex + 1
            aId.x = WeatherModelUrlUtils.url(time); //This assignment works
        }
    }
    A {
        id: aId
        x: WeatherModelUrlUtils.url(1); //This binding doesn't work
        onXChanged: {
            console.log("x changed:" + aId.x.timeIndex)
        }
    }
    B {
        id: bId
        y: aId.x //This binding doesn't work
        onZChanged: {
            console.log("z changed:" + bId.z)
        }
    }
    Text {
        text: "aId.x.timeIndex:" + aId.x.timeIndex + "\nbId.y.timeIndex:" + bId.y.timeIndex + "\nb.z:" + bId.z
    }
    Text {
        anchors.centerIn: parent
        text: "Click to change the time index"
        font.pixelSize: 20
    }
}
 

#ifndef A_H
#define A_H
#include <QObject>
#include <QProperty>
#include <QtQml>
//Our includes
#include "WeatherModelUrl.h"
 
class A : public QObject
{
    Q_OBJECT
    QML_ELEMENT
    //This doesn't work.
    Q_PROPERTY(WeatherModelUrl x READ x WRITE setX NOTIFY xChanged BINDABLE bindableX)
    //This works
//    Q_PROPERTY(WeatherModelUrl x READ x WRITE setX NOTIFY xChanged)

        public:
                 explicit A(QObject *parent = nullptr) : QObject(parent) {}
    WeatherModelUrl x() const { return m_x.value(); }
    void setX(const WeatherModelUrl& newX) { m_x.setValue(newX);}
    QBindable<WeatherModelUrl> bindableX() { return QBindable<WeatherModelUrl>(&m_x); }
signals:
    void xChanged();
private:
    Q_OBJECT_BINDABLE_PROPERTY(A, WeatherModelUrl, m_x, &A::xChanged)
};
class B : public QObject
{
    Q_OBJECT
    QML_ELEMENT
    //This doesn't work.
    Q_PROPERTY(WeatherModelUrl y READ y WRITE setY NOTIFY yChanged BINDABLE bindableY)
    //This works!
//    Q_PROPERTY(WeatherModelUrl y READ y WRITE setY NOTIFY yChanged)
    Q_PROPERTY(int z READ z NOTIFY zChanged)
public:
    explicit B(QObject *parent = nullptr) : QObject(parent) {
        m_z.setBinding([this]()->int {
            auto y = m_y.value();
            if(y.timeIndex() < 2) {
                return -1;
            }
            return y.timeIndex() * 2;
        });
    }
    WeatherModelUrl y() const { return m_y.value(); }
    void setY(const WeatherModelUrl& newY) { m_y.setValue(newY); }
    QBindable<WeatherModelUrl> bindableY() { return QBindable<WeatherModelUrl>(&m_y); }
    int z() const { return m_z.value(); }
    QBindable<int> bindableZ() const { return QBindable<int>(&m_z); }
signals:
    void yChanged();
    void zChanged();
private:
    Q_OBJECT_BINDABLE_PROPERTY(B, WeatherModelUrl, m_y, &B::yChanged)
    Q_OBJECT_BINDABLE_PROPERTY(B, int, m_z, &B::zChanged)
};
#endif // A_H

#ifndef WEATHERMODELURL_H
#define WEATHERMODELURL_H
#include <QtQml>
#include <QObject>
//#include "Result.h"
class WeatherModelUrl
{
    Q_GADGET
        QML_NAMED_ELEMENT(weatherModelUrl)
    QML_UNCREATABLE("WeatherModelUrl is uncreatable");
    Q_PROPERTY(qsizetype timeIndex READ timeIndex CONSTANT)
public:
    WeatherModelUrl() :
        m_timeIndex(-1)
       {}
       WeatherModelUrl(qsizetype timeIdx) :
           m_timeIndex(timeIdx)
       {}
    // Getters
    qsizetype timeIndex() const { return m_timeIndex; }
    bool operator ==(const WeatherModelUrl &other) const;
    bool operator !=(const WeatherModelUrl &other) const;
private:
    qsizetype m_timeIndex;
};
QML_DECLARE_TYPE(WeatherModelUrl)
QDebug operator<<(QDebug debug, const WeatherModelUrl &url);
////For QML use
class WeatherModelUrlUtils : public QObject
{
    Q_OBJECT
    QML_ELEMENT
    QML_SINGLETON
    public:
    WeatherModelUrlUtils(QObject* parent = nullptr) : QObject(parent) {}
    Q_INVOKABLE static WeatherModelUrl url(int timeIdx) {
       return WeatherModelUrl(timeIdx);
    }
};
#endif // WEATHERMODELURL_H