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  1. Qt
  2. QTBUG-139727

QML tools: More warnings about incompatible types

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      Consider different ways we could (accidentally) shove incompatible types into strongly-typed properties.

       

      Code

      import QtQuick

Window {
    id: window
    width: 400
    height: 300
    visible: true

    property Item itemProp: window // Runtime + qmlsc + qmllint + qmlls warnings

    property list<Item> itemList: [
        window // Runtime warning only
    ]

    function assignItemProp() {
        window.itemProp = window // Runtime + qmlsc warnings only
    }

    function assignItemList() {
        window.itemList[0] = window // Runtime + qmlsc warnings only
    }

    Component.onCompleted: {
        assignItemProp()
        assignItemList()
    }
}

       

      Outcomes
      We get a mixed bag of warnings:

      Incompatible assignment Runtime warning qmllint/qmlls warning qmlsc warning
      itemProp declarative initialization ✔️ ✔️ ✔️
      itemList declarative initialization ✔️ ❌ ❌
      itemProp imperative assignment ✔️ ❌ ✔️
      itemList imperative assignment ✔️ ❌ ✔️

       

      Suggestion

      Fill the table above with ticks, if all types involved are known at edit/build time.

       

      Use case
      A customer upgraded to Qt 6.8 and they now see new incompatible-type warnings across their project (thanks to the fix for QTBUG-127343), like:

      qt.qml.list.incompatible: Cannot append Main_QMLTYPE_0(0x26857677a50) to a QML list of QQuickItem*

      However, there is no easy way to track down (and fix) the cause of these warnings.

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            qtqmlteam Qt Qml Team User
            skoh-qt Sze Howe Koh
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              Created:
              Updated:

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