QML compile error about duplicate signals can be improved

Error message from duplicate signals (attempt to override, in my specific case) is confusing: it implies that there is some "valid" way to override signals. But as far as I can tell from the code, there isn't.

Duplicate signal name: invalid override of property change signal or superclass signal

QString signalName = stringAt(s->nameIndex);
if (seenSignals.contains(signalName))
    return qQmlCompileError(s->location, QQmlPropertyCacheCreatorBase::tr("Duplicate signal name: invalid override of property change signal or superclass signal"));
seenSignals.insert(signalName);