Non-local enums undefined in QML

This issue occurs if you derive an existing class (e.g. QSettings) which doesn't register their enums via Q_ENUMS or Q_ENUM.

You can make the enum keys visible in QML (autocomplete) if the child class registers them with Q_ENUMS, but it seems that QML can't resolve the related values.

Surprisingly you can get the enum values from Q_INVOKABLE methods, slots and signals if you register the parent enum via Q_DECLARE_METATYPE and qRegisterMetaType (see QTBUG-20639).

For Qt classes the problem could be solved, if QTBUG-28586 gets fixed.

But shouldn't there be a general solution if you can't change the parent class?

(Associated commits here and here).