const QCanBusFactory *factory = qobject_cast<QCanBusFactory *>(obj);

In function

QList<QCanBusDeviceInfo> QCanBus::availableDevices(const QString &plugin, QString *errorMessage) const

Following

const QCanBusFactory *factory = qobject_cast<QCanBusFactory *>(obj);

Caused

error: no member called qt_metacall

Check also function

QCanBusDevice *QCanBus::createDevice(const QString &plugin, const QString &interfaceName,
QString *errorMessage) const