Code

import QtQuick

Window {
    id: window
    width: 640
    height: 480
    visible: true

    component Config: QtObject { required property color winColor }
    component BadConfig: Config { property color winColor: "beige" }

    property Config cfg: BadConfig { winColor: "yellow" }
    color: window.cfg.winColor
}

Outcomes
At compile time, qmlsc says,

Warning: Main.qml:13:20: Member winColor of QObject of (component in Main.qml)::cfg with type Config can be shadowed [compiler]
	color: window.cfg.winColor
                  	^^^^^^^^

And indeed, BadConfig is trying to shadow it. However, it cannot do that because we get this at runtime:

QQmlApplicationEngine failed to create component
qrc:/qt/qml/untitled4/Main.qml:9:31: Required property winColor was not initialized

Suggestion

Since it is impossible to shadow a required property without blocking the object's initialization, could we treat that property as FINAL?

• (Primary suggestion) qmlsc shouldn't warn that Config.winColor can be shadowed
• (Secondary suggestion) BadConfig trying to implement a new property called winColor should be treated as an error