1) open the qtdeclarative project in Creator
2) try to build
3) get errors like this:

/home/rutledge/dev/qt5/qtdeclarative/tests/auto/qml/qqmllanguage/data/readonlyObjectProperty.qml:4: error: Expected token `,'
/home/rutledge/dev/qt5/qtdeclarative/tests/auto/qml/qqmllanguage/data/readonlyObjectProperty.qml:5: error: Expected token `:'

The code it's complaining about looks like this

import QtQml 2.0

QtObject {
    readonly property QtObject subObject: QtObject {
        property int readWrite: 42
    }
}

which looks OK, and in fact "runs" in the qml tool (doesn't create anything visible though). So it must be some other validation parser which is unhappy with this QML?

When building qtdeclarative, this is just a distraction. It has been that way for several Creator releases now.