The return value should return an enum value which can be used to compare it to the exposed enum constants.

But the return values are treated as objects and can not be compared to the integer constants:

// in C++
enum StatusCode { Good };
QtBugNamespace::StatusCode goodStatus() // returns an enum

// in QML
// QtBugImport.Constants.Good == 0 (number)
// but object.goodStatus is "Good" (object)

This happens for QObject as well as Q_GADGET. Change https://codereview.qt-project.org/244514 was already applied on top of 5.12

When moving the namespace from ns.h into foo.h it suddenly works.

The example contains a QObject and a Q_GADGET with the same issue.