This is a clone of
QTBUG-19741, which is closed but is still broken in Qt 5.8.
When declaring in the same class one enumeration, the corresponding Q_ENUM's, and a Q_INVOKABLE function with the enumeration in parameter, the function can be called from qml.
But if the enumeration comes from another class, the Q_INVOKABLE function cannot be called with the following error message:
"Error: Unknown method parameter type"