4 files changed, 27 insertions, 43 deletions

diff --git a/src/qml/qml/qqml.h b/src/qml/qml/qqml.h
index 61eb5e1ffe..078bd93d25 100644
--- a/src/qml/qml/qqml.h
+++ b/src/qml/qml/qqml.h
@@ -153,7 +153,8 @@
 
 #define QML_IMPLEMENTS_INTERFACES(INTERFACES) \
     Q_INTERFACES(INTERFACES) \
-    enum class QmlIsInterface {yes = false};
+    enum class QmlIsInterface {yes = false}; \
+    template<typename, typename> friend struct QML_PRIVATE_NAMESPACE::QmlInterface;
 
 #define QML_UNAVAILABLE \
     QML_FOREIGN(QQmlTypeNotAvailable)
diff --git a/src/qmlcompiler/qqmljsscope.cpp b/src/qmlcompiler/qqmljsscope.cpp
index 11a2b4a619..1fe22ab5a8 100644
--- a/src/qmlcompiler/qqmljsscope.cpp
+++ b/src/qmlcompiler/qqmljsscope.cpp
@@ -41,20 +41,14 @@ QT_BEGIN_NAMESPACE
 template<typename Action>
 static bool searchBaseAndExtensionTypes(const QQmlJSScope *type, const Action &check)
 {
-    const QQmlJSScope *nonCompositeBase = nullptr;
     for (const QQmlJSScope *scope = type; scope; scope = scope->baseType().data()) {
-        if (check(scope))
-            return true;
-
-        if (!nonCompositeBase && !scope->isComposite())
-            nonCompositeBase = scope;
-    }
-
-    if (!nonCompositeBase)
-        return false;
+        // Extensions override their base types
+        for (const QQmlJSScope *extension = scope->extensionType().data(); extension;
+             extension = extension->baseType().data()) {
+            if (check(extension))
+                return true;
+        }
 
-    for (const QQmlJSScope *scope = nonCompositeBase->extensionType().data(); scope;
-         scope = scope->baseType().data()) {
         if (check(scope))
             return true;
     }
@@ -263,23 +257,7 @@ void QQmlJSScope::resolveGroupedScopes()
             return false;
         };
 
-        const QQmlJSScope *nonCompositeBase = isComposite() ? this : nullptr;
-        for (const QQmlJSScope *type = this; type; type = type->baseType().data()) {
-            if (findProperty(type))
-                break;
-
-            if (!nonCompositeBase && !type->isComposite())
-                nonCompositeBase = type;
-        }
-
-        if (!childScope->m_baseType && nonCompositeBase && nonCompositeBase != this) {
-            for (const QQmlJSScope *type = nonCompositeBase->extensionType().data(); type;
-                 type = type->baseType().data()) {
-                if (findProperty(type))
-                    break;
-            }
-        }
-
+        searchBaseAndExtensionTypes(this, findProperty);
         childScope->resolveGroupedScopes();
     }
 }
diff --git a/src/qmltyperegistrar/qmltypesclassdescription.cpp b/src/qmltyperegistrar/qmltypesclassdescription.cpp
index 70a4e49d19..2310b8b3b2 100644
--- a/src/qmltyperegistrar/qmltypesclassdescription.cpp
+++ b/src/qmltyperegistrar/qmltypesclassdescription.cpp
@@ -112,9 +112,14 @@ void QmlTypesClassDescription::collectLocalAnonymous(
     const auto classInfos = classDef->value(QLatin1String("classInfos")).toArray();
     for (const QJsonValue &classInfo : classInfos) {
         const QJsonObject obj = classInfo.toObject();
-        if (obj[QLatin1String("name")].toString() == QLatin1String("DefaultProperty")) {
+        const QString name = obj[QStringLiteral("name")].toString();
+        const QString value = obj[QStringLiteral("value")].toString();
+
+        if (name == QStringLiteral("DefaultProperty")) {
             defaultProp = obj[QLatin1String("value")].toString();
-            break;
+        } else if (name == QStringLiteral("QML.Extended")) {
+            extensionType = value;
+            collectRelated(value, types, foreign, defaultRevision);
         }
     }
 
diff --git a/src/qmltyperegistrar/qmltypescreator.cpp b/src/qmltyperegistrar/qmltypescreator.cpp
index 4dafdc4490..f754679fb9 100644
--- a/src/qmltyperegistrar/qmltypescreator.cpp
+++ b/src/qmltyperegistrar/qmltypescreator.cpp
@@ -61,6 +61,17 @@ void QmlTypesCreator::writeClassProperties(const QmlTypesClassDescription &colle
     if (!collector.sequenceValueType.isEmpty())
         m_qml.writeScriptBinding(QLatin1String("valueType"), enquote(collector.sequenceValueType));
 
+    if (!collector.extensionType.isEmpty())
+        m_qml.writeScriptBinding(QLatin1String("extension"), enquote(collector.extensionType));
+
+    if (!collector.implementsInterfaces.isEmpty()) {
+        QStringList interfaces;
+        for (const QString &interface : collector.implementsInterfaces)
+            interfaces << enquote(interface);
+
+        m_qml.writeArrayBinding(QLatin1String("interfaces"), interfaces);
+    }
+
     if (collector.elementName.isEmpty())
         return;
 
@@ -96,17 +107,6 @@ void QmlTypesCreator::writeClassProperties(const QmlTypesClassDescription &colle
 
     if (!collector.attachedType.isEmpty())
         m_qml.writeScriptBinding(QLatin1String("attachedType"), enquote(collector.attachedType));
-
-    if (!collector.extensionType.isEmpty())
-        m_qml.writeScriptBinding(QLatin1String("extension"), enquote(collector.extensionType));
-
-    if (!collector.implementsInterfaces.isEmpty()) {
-        QStringList interfaces;
-        for (const QString &interface : collector.implementsInterfaces)
-            interfaces << enquote(interface);
-
-        m_qml.writeArrayBinding(QLatin1String("interfaces"), interfaces);
-    }
 }
 
 void QmlTypesCreator::writeType(const QJsonObject &property, const QString &key, bool isReadonly,