Compiler warns about signal for properties starting with "on"

Despite the fact that using properties starting with "on" might not be very wise, it is not forbidden and correctly handled during runtime.

Compiler and runtime seem to disagree about signal vs property when interpreting

import QtQuick

Window {
    id: root
    width: 640
    height: 480
    visible: true
    title: "Foo"

    Switch {
        onLabel: qsTr("Power on")
    }
}

, though. The compiler claims

Warning: main.qml:11:9: no matching signal found for handler "onLabel" [unqualified]
        onLabel: qsTr("Power on")
        ^^^^^^^

, but the signal would be have been named onOnLabel instead.