@Joel-Bodenmann
Okay, this is a curious thing. I'd try some debugging of the QMetaEnum in debug mode, to see what the problem might be; something like this:
QMetaEnum myEnum = MetaEnum::fromType<LibraryItem::Type>();
if (!myEnum.isValid())
qDebug() << myEnum.name() << " is invalid with scope " << myEnum.scope();
for (qint32 i = 0, count = myEnum.keyCount(); i < count; i++)
qDebug() << myEnum.key(i);
Try it out and see what is printed in the debug window.