Q_ENUMs from one class cannot be used as a Q_INVOKABLE function parameter of another class when being in a namespace

This is a clone of QTBUG-58454, which is closed but is still broken in Qt 5.13 - at least in the special case where the class is inside a namespace.

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"

Accessing the Enum value outside the method call does work.