9 files changed, 45 insertions, 44 deletions
diff --git a/src/qml/qml/qqmlcomponent.cpp b/src/qml/qml/qqmlcomponent.cpp
index 0ca3836181..56df62e50e 100644
--- a/src/qml/qml/qqmlcomponent.cpp
+++ b/src/qml/qml/qqmlcomponent.cpp
@@ -916,8 +916,7 @@ QObject *QQmlComponentPrivate::createWithProperties(QObject *parent, const QVari
 
     if (state.hasUnsetRequiredProperties()) {
         if (behavior == CreateWarnAboutRequiredProperties) {
-            const RequiredProperties &unsetRequiredProperties = state.requiredProperties();
-            for (const auto &unsetRequiredProperty : unsetRequiredProperties) {
+            for (const auto &unsetRequiredProperty : std::as_const(*state.requiredProperties())) {
                 const QQmlError error = unsetRequiredPropertyToQQmlError(unsetRequiredProperty);
                 qmlWarning(rv, error);
             }
@@ -1110,6 +1109,7 @@ void QQmlComponentPrivate::complete(QQmlEnginePrivate *enginePriv, ConstructionS
     Finds the matching top-level property with name \a name of the component \a createdComponent.
     If it was a required property or an alias to a required property contained in \a
     requiredProperties, it is removed from it.
+    \a requiredProperties must be non-null.
 
     If wasInRequiredProperties is non-null, the referenced boolean is set to true iff the property
     was found in requiredProperties.
@@ -1122,9 +1122,10 @@ void QQmlComponentPrivate::complete(QQmlEnginePrivate *enginePriv, ConstructionS
     setInitialProperties.
  */
 QQmlProperty QQmlComponentPrivate::removePropertyFromRequired(
-        QObject *createdComponent, const QString &name, RequiredProperties &requiredProperties,
+        QObject *createdComponent, const QString &name, RequiredProperties *requiredProperties,
         QQmlEngine *engine, bool *wasInRequiredProperties)
 {
+    Q_ASSERT(requiredProperties);
     QQmlProperty prop(createdComponent, name, engine);
     auto privProp = QQmlPropertyPrivate::get(prop);
     if (prop.isValid()) {
@@ -1145,11 +1146,11 @@ QQmlProperty QQmlComponentPrivate::removePropertyFromRequired(
             Q_ASSERT(data && data->propertyCache);
             targetProp = data->propertyCache->property(targetProp->coreIndex());
         }
-        auto it = requiredProperties.find(targetProp);
-        if (it != requiredProperties.end()) {
+        auto it = requiredProperties->find(targetProp);
+        if (it != requiredProperties->end()) {
             if (wasInRequiredProperties)
                 *wasInRequiredProperties = true;
-            requiredProperties.erase(it);
+            requiredProperties->erase(it);
         } else {
             if (wasInRequiredProperties)
                 *wasInRequiredProperties = false;
@@ -1178,8 +1179,7 @@ void QQmlComponent::completeCreate()
 void QQmlComponentPrivate::completeCreate()
 {
     if (state.hasUnsetRequiredProperties()) {
-        const RequiredProperties& unsetRequiredProperties = state.requiredProperties();
-        for (const auto& unsetRequiredProperty: unsetRequiredProperties) {
+        for (const auto& unsetRequiredProperty: std::as_const(*state.requiredProperties())) {
             QQmlError error = unsetRequiredPropertyToQQmlError(unsetRequiredProperty);
             state.errors.push_back(QQmlComponentPrivate::AnnotatedQmlError { error, true });
         }
@@ -1484,7 +1484,7 @@ struct QmlIncubatorObject : public QV4::Object
     static ReturnedValue method_forceCompletion(const FunctionObject *, const Value *thisObject, const Value *argv, int argc);
 
     void statusChanged(QQmlIncubator::Status);
-    void setInitialState(QObject *, RequiredProperties &requiredProperties);
+    void setInitialState(QObject *, RequiredProperties *requiredProperties);
 };
 
 }
@@ -1582,7 +1582,7 @@ static void QQmlComponent_setQmlParent(QObject *me, QObject *parent)
 */
 
 
-void QQmlComponentPrivate::setInitialProperties(QV4::ExecutionEngine *engine, QV4::QmlContext *qmlContext, const QV4::Value &o, const QV4::Value &v, RequiredProperties &requiredProperties, QObject *createdComponent)
+void QQmlComponentPrivate::setInitialProperties(QV4::ExecutionEngine *engine, QV4::QmlContext *qmlContext, const QV4::Value &o, const QV4::Value &v, RequiredProperties *requiredProperties, QObject *createdComponent)
 {
     QV4::Scope scope(engine);
     QV4::ScopedObject object(scope);
@@ -1627,7 +1627,7 @@ void QQmlComponentPrivate::setInitialProperties(QV4::ExecutionEngine *engine, QV
         if (engine->hasException) {
             qmlWarning(createdComponent, engine->catchExceptionAsQmlError());
             continue;
-        } else if (isTopLevelProperty) {
+        } else if (isTopLevelProperty && requiredProperties) {
             auto prop = removePropertyFromRequired(createdComponent, name->toQString(),
                                                    requiredProperties, engine->qmlEngine());
         }
@@ -1721,7 +1721,7 @@ void QQmlComponent::createObject(QQmlV4Function *args)
     }
     if (d->state.hasUnsetRequiredProperties()) {
         QList<QQmlError> errors;
-        for (const auto &requiredProperty: d->state.requiredProperties()) {
+        for (const auto &requiredProperty: std::as_const(*d->state.requiredProperties())) {
             errors.push_back(QQmlComponentPrivate::unsetRequiredPropertyToQQmlError(requiredProperty));
         }
         qmlWarning(rv, errors);
@@ -1878,7 +1878,7 @@ void QQmlComponent::incubateObject(QQmlV4Function *args)
 }
 
 // XXX used by QSGLoader
-void QQmlComponentPrivate::initializeObjectWithInitialProperties(QV4::QmlContext *qmlContext, const QV4::Value &valuemap, QObject *toCreate, RequiredProperties &requiredProperties)
+void QQmlComponentPrivate::initializeObjectWithInitialProperties(QV4::QmlContext *qmlContext, const QV4::Value &valuemap, QObject *toCreate, RequiredProperties *requiredProperties)
 {
     QV4::ExecutionEngine *v4engine = engine->handle();
     QV4::Scope scope(v4engine);
@@ -1977,7 +1977,7 @@ void QV4::Heap::QmlIncubatorObject::destroy() {
     Object::destroy();
 }
 
-void QV4::QmlIncubatorObject::setInitialState(QObject *o, RequiredProperties &requiredProperties)
+void QV4::QmlIncubatorObject::setInitialState(QObject *o, RequiredProperties *requiredProperties)
 {
     QQmlComponent_setQmlParent(o, d()->parent);
 
diff --git a/src/qml/qml/qqmlcomponent_p.h b/src/qml/qml/qqmlcomponent_p.h
index e61fd1ca69..064b609b19 100644
--- a/src/qml/qml/qqmlcomponent_p.h
+++ b/src/qml/qml/qqmlcomponent_p.h
@@ -47,8 +47,8 @@ public:
 
     QObject *beginCreate(QQmlRefPointer<QQmlContextData>);
     void completeCreate();
-    void initializeObjectWithInitialProperties(QV4::QmlContext *qmlContext, const QV4::Value &valuemap, QObject *toCreate, RequiredProperties &requiredProperties);
-    static void setInitialProperties(QV4::ExecutionEngine *engine, QV4::QmlContext *qmlContext, const QV4::Value &o, const QV4::Value &v, RequiredProperties &requiredProperties, QObject *createdComponent);
+    void initializeObjectWithInitialProperties(QV4::QmlContext *qmlContext, const QV4::Value &valuemap, QObject *toCreate, RequiredProperties *requiredProperties);
+    static void setInitialProperties(QV4::ExecutionEngine *engine, QV4::QmlContext *qmlContext, const QV4::Value &o, const QV4::Value &v, RequiredProperties *requiredProperties, QObject *createdComponent);
     static QQmlError unsetRequiredPropertyToQQmlError(const RequiredPropertyInfo &unsetRequiredProperty);
 
     virtual void incubateObject(
@@ -99,25 +99,27 @@ public:
            \internal A list of pending required properties that need
            to be set in order for object construction to be successful.
          */
-        RequiredProperties &requiredProperties() {
+        RequiredProperties *requiredProperties() {
             if (hasCreator())
                 return m_creator->requiredProperties();
             else
-                return m_requiredProperties;
+                return &m_requiredProperties;
         }
 
         void addPendingRequiredProperty(const QQmlPropertyData *propData, const RequiredPropertyInfo &info)
         {
-            requiredProperties().insert(propData, info);
+            Q_ASSERT(requiredProperties());
+            requiredProperties()->insert(propData, info);
         }
 
         bool hasUnsetRequiredProperties() const {
-            return !const_cast<ConstructionState *>(this)->requiredProperties().isEmpty();
+            return !const_cast<ConstructionState *>(this)->requiredProperties()->isEmpty();
         }
 
         void clearRequiredProperties()
         {
-            requiredProperties().clear();
+            if (auto reqProps = requiredProperties())
+                reqProps->clear();
         }
 
 
@@ -167,8 +169,7 @@ public:
     static void completeDeferred(QQmlEnginePrivate *enginePriv, DeferredState *deferredState);
 
     static void complete(QQmlEnginePrivate *enginePriv, ConstructionState *state);
-    static QQmlProperty removePropertyFromRequired(
-            QObject *createdComponent, const QString &name, RequiredProperties &requiredProperties,
+    static QQmlProperty removePropertyFromRequired(QObject *createdComponent, const QString &name, RequiredProperties *requiredProperties,
             QQmlEngine *engine, bool *wasInRequiredProperties = nullptr);
 
     QQmlEngine *engine;
diff --git a/src/qml/qml/qqmlincubator.cpp b/src/qml/qml/qqmlincubator.cpp
index afd265516a..3c0a9dff36 100644
--- a/src/qml/qml/qqmlincubator.cpp
+++ b/src/qml/qml/qqmlincubator.cpp
@@ -263,7 +263,7 @@ void QQmlIncubatorPrivate::incubate(QQmlInstantiationInterrupt &i)
         if (!tresult)
             errors = creator->errors;
         else {
-           RequiredProperties& requiredProperties = creator->requiredProperties();
+           RequiredProperties* requiredProperties = creator->requiredProperties();
            for (auto it = initialProperties.cbegin(); it != initialProperties.cend(); ++it) {
                auto component = tresult;
                auto name = it.key();
@@ -295,9 +295,9 @@ void QQmlIncubatorPrivate::incubate(QQmlInstantiationInterrupt &i)
             ddata->rootObjectInCreation = false;
             if (q) {
                 q->setInitialState(result);
-                if (creator && !creator->requiredProperties().empty()) {
-                    const auto& unsetRequiredProperties = creator->requiredProperties();
-                    for (const auto& unsetRequiredProperty: unsetRequiredProperties)
+                if (creator && !creator->requiredProperties()->empty()) {
+                    const RequiredProperties *unsetRequiredProperties = creator->requiredProperties();
+                    for (const auto& unsetRequiredProperty: *unsetRequiredProperties)
                         errors << QQmlComponentPrivate::unsetRequiredPropertyToQQmlError(unsetRequiredProperty);
                 }
             }
@@ -647,14 +647,15 @@ QObject *QQmlIncubator::object() const
 }
 
 /*!
-Return a list of properties which are required but haven't been set yet.
+Return a pointer to a list of properties which are required but haven't
+been set yet.
 This list can be modified, so that subclasses which implement special logic
 setInitialProperties can mark properties set there as no longer required.
 
 \sa QQmlIncubator::setInitialProperties
 \since 5.15
 */
-RequiredProperties &QQmlIncubatorPrivate::requiredProperties()
+RequiredProperties *QQmlIncubatorPrivate::requiredProperties()
 {
     return creator->requiredProperties();
 }
diff --git a/src/qml/qml/qqmlincubator_p.h b/src/qml/qml/qqmlincubator_p.h
index 00954737f0..a582fbf3ff 100644
--- a/src/qml/qml/qqmlincubator_p.h
+++ b/src/qml/qml/qqmlincubator_p.h
@@ -70,7 +70,7 @@ public:
 
     void forceCompletion(QQmlInstantiationInterrupt &i);
     void incubate(QQmlInstantiationInterrupt &i);
-    RequiredProperties &requiredProperties();
+    RequiredProperties *requiredProperties();
     bool hadTopLevelRequiredProperties() const;
 };
 
diff --git a/src/qml/qml/qqmlobjectcreator_p.h b/src/qml/qml/qqmlobjectcreator_p.h
index 844a4ee73b..2371facc0a 100644
--- a/src/qml/qml/qqmlobjectcreator_p.h
+++ b/src/qml/qml/qqmlobjectcreator_p.h
@@ -113,7 +113,7 @@ public:
     }
     QFiniteStack<QQmlGuard<QObject> > &allCreatedObjects() { return sharedState->allCreatedObjects; }
 
-    RequiredProperties &requiredProperties() {return sharedState->requiredProperties;}
+    RequiredProperties *requiredProperties() {return &sharedState->requiredProperties;}
     bool componentHadTopLevelRequiredProperties() const {return sharedState->hadTopLevelRequiredProperties;}
 
     static QQmlComponent *createComponent(QQmlEngine *engine,
diff --git a/src/qmlmodels/qqmldelegatemodel.cpp b/src/qmlmodels/qqmldelegatemodel.cpp
index 00072636d1..fcbcec15a1 100644
--- a/src/qmlmodels/qqmldelegatemodel.cpp
+++ b/src/qmlmodels/qqmldelegatemodel.cpp
@@ -931,9 +931,9 @@ void QQDMIncubationTask::initializeRequiredProperties(QQmlDelegateModelItem *mod
             proxyContext->setContextObject(nullptr);
         }
 
-        if (incubatorPriv->requiredProperties().empty())
+        if (incubatorPriv->requiredProperties()->empty())
             return;
-        RequiredProperties &requiredProperties = incubatorPriv->requiredProperties();
+        RequiredProperties *requiredProperties = incubatorPriv->requiredProperties();
 
         auto qmlMetaObject = modelItemToIncubate->metaObject();
         // if a required property was not in the model, it might still be a static property of the
diff --git a/src/qmlmodels/qqmltableinstancemodel.cpp b/src/qmlmodels/qqmltableinstancemodel.cpp
index 1c14427b90..e4fcae2a44 100644
--- a/src/qmlmodels/qqmltableinstancemodel.cpp
+++ b/src/qmlmodels/qqmltableinstancemodel.cpp
@@ -397,8 +397,8 @@ bool QQmlTableInstanceModel::setRequiredProperty(int index, const QString &name,
 
     bool wasInRequired = false;
     const auto task = QQmlIncubatorPrivate::get(modelItem->incubationTask);
-    RequiredProperties &props = task->requiredProperties();
-    if (props.empty())
+    RequiredProperties *props = task->requiredProperties();
+    if (props->empty())
         return false;
 
     QQmlProperty componentProp = QQmlComponentPrivate::removePropertyFromRequired(
@@ -492,7 +492,7 @@ void QQmlTableInstanceModelIncubationTask::setInitialState(QObject *object)
     modelItemToIncubate->object = object;
     emit tableInstanceModel->initItem(modelItemToIncubate->index, object);
 
-    if (!QQmlIncubatorPrivate::get(this)->requiredProperties().empty()) {
+    if (!QQmlIncubatorPrivate::get(this)->requiredProperties()->empty()) {
         modelItemToIncubate->object = nullptr;
         object->deleteLater();
     }
diff --git a/src/quicktemplates2/qquickstackelement.cpp b/src/quicktemplates2/qquickstackelement.cpp
index e165a780bb..f8001a2980 100644
--- a/src/quicktemplates2/qquickstackelement.cpp
+++ b/src/quicktemplates2/qquickstackelement.cpp
@@ -141,13 +141,12 @@ bool QQuickStackElement::load(QQuickStackView *parent)
         if (component->isError())
             QQuickStackViewPrivate::get(parent)->warn(component->errorString().trimmed());
     } else {
-        RequiredProperties noRequiredProperties {};
-        initialize(noRequiredProperties);
+        initialize(/*required properties=*/nullptr);
     }
     return item;
 }
 
-void QQuickStackElement::incubate(QObject *object, RequiredProperties &requiredProperties)
+void QQuickStackElement::incubate(QObject *object, RequiredProperties *requiredProperties)
 {
     item = qmlobject_cast<QQuickItem *>(object);
     if (item) {
@@ -157,7 +156,7 @@ void QQuickStackElement::incubate(QObject *object, RequiredProperties &requiredP
     }
 }
 
-void QQuickStackElement::initialize(RequiredProperties &requiredProperties)
+void QQuickStackElement::initialize(RequiredProperties *requiredProperties)
 {
     if (!item || init)
         return;
@@ -182,9 +181,9 @@ void QQuickStackElement::initialize(RequiredProperties &requiredProperties)
         properties.clear();
     }
 
-    if (!requiredProperties.empty()) {
+    if (requiredProperties && !requiredProperties->empty()) {
         QString error;
-        for (const auto &property: requiredProperties) {
+        for (const auto &property: *requiredProperties) {
             error += QLatin1String("Property %1 was marked as required but not set.\n")
                     .arg(property.propertyName);
         }
diff --git a/src/quicktemplates2/qquickstackelement_p_p.h b/src/quicktemplates2/qquickstackelement_p_p.h
index f591e8fd5d..00b150805d 100644
--- a/src/quicktemplates2/qquickstackelement_p_p.h
+++ b/src/quicktemplates2/qquickstackelement_p_p.h
@@ -39,8 +39,8 @@ public:
     static QQuickStackElement *fromObject(QObject *object, QQuickStackView *view, QString *error);
 
     bool load(QQuickStackView *parent);
-    void incubate(QObject *object, RequiredProperties &requiredProperties);
-    void initialize(RequiredProperties &requiredProperties);
+    void incubate(QObject *object, RequiredProperties *requiredProperties);
+    void initialize(RequiredProperties *requiredProperties);
 
     void setIndex(int index);
     void setView(QQuickStackView *view);