[Reg in Qt 6] setProperty() fails for QFlags types

For example (Qt::textFormat is an enum while Qt::Alignment is a QFlags):

    const QVariant v1("RichText");
    const QVariant v2("AlignBottom");
    QLabel l;
    qDebug() << l.setProperty("textFormat", v1); // true in Qt 5 and 6
    qDebug() << l.setProperty("alignment", v2); // true in 5, FALSE in 6

What it looks like to me is that setProperty() ends up in QMetaProperty::write(), and in Qt 5, it enters the block that calls key[s]ToValue(), which successfully decodes the string to enum values. But in Qt 6, that block is never entered at all, since it is behind this (changed) test:

if (isEnumType() && !t.metaObject() && v.metaType().id() == QMetaType::QString)

and the middle term fails - both the metatypes do in fact have a metaObject. But I don't know if that test is as it should be or not.

Anyway, we next run into another Qt 6 issue/bug, in QVariant, which may or may not be related. Since, we did not enter the block above, the code instead tries to call QVariant::convert(). That succeeds for TextFormat but fails for Alignment - even though the QVariant claims to be able to convert a string in Qt 6:

    qDebug() << v1.canConvert<Qt::TextFormat>(); // true Qt 5 and 6
    qDebug() << v1.value<Qt::TextFormat>(); // Qt::RichText in 5 and 6
    qDebug() << v2.canConvert<Qt::Alignment>(); // false 5, TRUE in 6 ?
    qDebug() << v2.value<Qt::Alignment>(); // empty QFlags in 5 and 6