Qt 5.7 Extending Popup (ASSERT: "_currentList.object" in file qml/qqmlobjectcreator.cpp, line 945)

[KrabQT]

I got the runtime error below when using my custom popup implementation with Qt 5.7 (Qt 5.7 is necessary because there is introduced Popup and it needs to be compiled with
-developer-build flag so private symbols (QQuickPopup class) are exported).

You can try replace "CPopup" with "Popup" in MyItem.qml and you will see it works, so the problem needs to be somewhere with the inheritance from QQuickPopup in my CustomPopup class.

ERROR: ASSERT: "_currentList.object" in file qml/qqmlobjectcreator.cpp, line 945

https://github.com/qt/qtquickcontrols2/blob/5.7/src/quicktemplates2/qquickpopup_p.h
https://github.com/qt/qtquickcontrols2/blob/5.7/src/quicktemplates2/qquickpopup.cpp
https://github.com/qt/qtdeclarative/blob/dev/src/qml/qml/qqmlobjectcreator_p.h
https://github.com/qt/qtdeclarative/blob/dev/src/qml/qml/qqmlobjectcreator.cpp

PROJECT: popuptest

popuptest.pro

TEMPLATE = app

QT += gui qml quick quickcontrols2
QT_PRIVATE += quick-private core-private gui-private qml-private quickcontrols2-private quicktemplates2-private

CONFIG += c++11

SOURCES += main.cpp \
    custompopup.cpp

RESOURCES += qml.qrc

# Additional import path used to resolve QML modules in Qt Creator's code model
QML_IMPORT_PATH =

# Default rules for deployment.
include(deployment.pri)

HEADERS += \
    custompopup.h

custompopup.h

#ifndef CUSTOMPOPUP_H
#define CUSTOMPOPUP_H

#include <private/qquickpopup_p.h>

class CustomPopup : public QQuickPopup
{

    Q_OBJECT
    //Q_PROPERTY(QQmlListProperty<QObject> contentData READ contentData FINAL)
    //Q_CLASSINFO("DefaultProperty", "contentData")
public:
    CustomPopup(QObject *parent = nullptr);

protected:
    bool overlayEvent(QQuickItem *item, QEvent *event) override;

private:
    /*Q_DISABLE_COPY(CustomPopup)
    Q_DECLARE_PRIVATE(QQuickPopup)*/
};


QML_DECLARE_TYPE(CustomPopup)

#endif // CUSTOMPOPUP_H

custompopup.cpp

#include "custompopup.h"

CustomPopup::CustomPopup(QObject *parent) : QQuickPopup(parent)
{

}

bool CustomPopup::overlayEvent(QQuickItem *item, QEvent *event)
{
        /*QQuickPopup implementation
        Q_D(QQuickPopup);
        switch (event->type()) {
        case QEvent::KeyPress:
        case QEvent::KeyRelease:
        case QEvent::MouseMove:
        case QEvent::Wheel:
            if (d->modal)
                event->accept();
            return d->modal;

        case QEvent::MouseButtonPress:
        case QEvent::MouseButtonRelease:
            if (d->modal)
                event->accept();
            d->tryClose(item, static_cast<QMouseEvent *>(event));
            return d->modal;

        default:
            return false;
        }
        */
   // Q_D(QQuickPopup);
    return QQuickPopup::overlayEvent(item, event);
}

main.cpp

#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include "custompopup.h"

int main(int argc, char *argv[])
{
    QGuiApplication app(argc, argv);

    QQmlApplicationEngine engine;

    qmlRegisterType<CustomPopup>("Custom", 1, 0, "CPopup");

    engine.load(QUrl(QStringLiteral("qrc:/main.qml")));

    return app.exec();
}

main.qml

import QtQuick 2.7
import QtQuick.Controls 1.5

ApplicationWindow {
    visible: true
    width: 600
    height: 480

    MyItem {
        anchors.fill: parent
    }
}

MyItem.qml

import QtQuick 2.0
import QtQuick.Controls 2.0
import Custom 1.0

Item {

    MouseArea {
        anchors.fill: parent
        acceptedButtons: Qt.RightButton
        onClicked: {
            menu.x = mouse.x
            menu.y = mouse.y
            menu.open()
        }

    }

    CPopup {
        id: menu
        Rectangle {
            width: 100
            height: 100
            color: "red"
        }
    }
}