class QmlTestSubProperty : public QObject
{
	Q_OBJECT
	QML_ELEMENT

	Q_PROPERTY(bool valid READ isValid CONSTANT)
	public:
	[[nodiscard]] bool isValid() const;
};

class QmlTest : public QObject
{
	Q_OBJECT
	QML_ELEMENT
	QML_SINGLETON

	Q_PROPERTY(QmlTestSubProperty* appData READ getAppData CONSTANT)

	QmlTestSubProperty* obj = new QmlTestSubProperty();

	public:
		[[nodiscard]] QmlTestSubProperty* getAppData() const;

	public:
		QmlTest();
		~QmlTest();
};

console.log("found property: " + QmlTest.appData.valid)

Warning: /tmp/b/QmlDummy/Main.qml:9:44: Type "QmlTestSubProperty" of property "appData" not found. This is likely due to a missing dependency entry or a type not being exposed declaratively. [unresolved-type]
                console.log("found property: " + QmlTest.appData.valid)
                                                        ^^^^^^^

Module {
    Component {
        file: "qml.h"
        name: "dummy::QmlTest"
        accessSemantics: "reference"
        prototype: "QObject"
        exports: ["Stuff/QmlTest 254.0"]
        isCreatable: false
        isSingleton: true
        exportMetaObjectRevisions: [65024]
        Property {
            name: "appData"
            type: "QmlTestSubProperty"
            isPointer: true
            read: "getAppData"
            index: 0
            isReadonly: true
            isConstant: true
        }
    }
    Component {
        file: "qml.h"
        name: "dummy::QmlTestSubProperty"
        accessSemantics: "reference"
        prototype: "QObject"
        exports: ["Stuff/QmlTestSubProperty 254.0"]
        exportMetaObjectRevisions: [65024]
        Property {
            name: "valid"
            type: "bool"
            read: "isValid"
            index: 0
            isReadonly: true
            isConstant: true
        }
    }
}