Binding QML Connections to 'enabled' property causes either a warning or an error

Implicitly defined onFoo properties in Connections are deprecated. Use this syntax instead: function onFoo(<arguments>)\{ ... }

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

import QtQuick 2.15
import QtQuick.Window 2.15

Window {
    visible: true
    width: 640
    height: 480
    title: qsTr("This file causes a warning")    

    Item {
        id: item
        enabled: true
    }    

    Connections {
        target: item
        onEnabledChanged: console.log("whatever")
    }
}

// This file causes a warning:
//
// qrc:/main.qml:15:5: QML Connections: Implicitly defined onFoo properties in Connections are deprecated. Use this syntax instead: function onFoo(<arguments>) { ... }

import QtQuick 2.15
import QtQuick.Window 2.15

Window {
    visible: true
    width: 640
    height: 480
    title: qsTr("This file causes an error")

    Item {
        id: item
        enabled: true
    }

    Connections {
        target: item
        function onEnabledChanged() {
            console.log("whatever")
        }
    }
}

// This file causes a runtime error:
//
// QQmlApplicationEngine failed to load component
// qrc:/main.qml:17:18: Duplicate method name: invalid override of property change signal or superclass signal

import QtQuick 2.15
import QtQuick.Window 2.15

Window {
    visible: true
    width: 640
    height: 480
    title: qsTr("This file works fine")

    Item {
        id: item
        enabled: true
//        property alias enabled2: enabled // Causes an error: qrc:/main-workaround.qml:13:34: Invalid alias reference. Unable to find id "enabled"
        property bool enabled2: enabled // works fine
    }

    Connections {
        target: item
        function onEnabled2Changed() {
            console.log("whatever")
        }
    }
}