QML范围：无效的别名引用

Question

我收到以下错误：qrc:/main.qml:17 Invalid alias reference. Unable to find id "button2"。可以通过以下qml文件重现该错误：

import QtQuick 2.1
import QtQuick.Controls 1.0
import QtQuick.Window 2.0
import QtQuick.Layouts 1.0
Window {
    visible: true
    width: 640
    height: 480
    title: qsTr("Hello World")
    Item {
    id: root

    property alias myprop: button2


    SplitView {
        id: splitView
        orientation: Qt.Vertical

        SplitView {
            id: splitView1
            orientation: Qt.Horizontal
            TabView {
                Tab{
                    title: "Tab1"
                }
                Tab{
                    title: "Tab2"

                    ColumnLayout {
                        GridLayout {
                            Button {
                                id: button2
                                text: qsTr("test button")
                            }
                        }


                    }
                }
            }


        }
    }
    }
}

似乎我对qml范围有误解。我以为父母可以访问所有孩子的ids？