PropertCache: Don't pass Q_GADGET value types as integers

We need to check for the IsGadget flag there.

Fixes: QTBUG-73734
Change-Id: Ic4afd4215e6ed346bc40794d85397f0f262715e2
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

src/qml/qml/qqmlpropertycache.cpp

@@ -929,8 +929,8 @@ static bool passTypeAsInt(int type)
     if (type < int(QMetaType::User))
         return false;
 
-    // Pointers to QObjects and QGadgets can be handled as they are.
+    // Pointers to QObjects and QGadgets, and QGadgets themselves can be handled as they are.
-    if (flags & (QMetaType::PointerToQObject | QMetaType::PointerToGadget))
+    if (flags & (QMetaType::PointerToQObject | QMetaType::PointerToGadget | QMetaType::IsGadget))
         return false;
 
     // If it wasn't declared as metatype, better don't touch it.

tests/auto/qml/qqmlpropertycache/data/passQGadget.qml

@@ -0,0 +1,12 @@
+import QtQml 2.2
+
+QtObject {
+    property var result;
+
+    property Connections connections: Connections {
+        target: emitter
+        onEmitGadget: function(gadget) {
+            result = gadget.someProperty;
+        }
+    }
+}

tests/auto/qml/qqmlpropertycache/tst_qqmlpropertycache.cpp

@@ -50,6 +50,7 @@ private slots:
     void signalHandlers();
     void signalHandlersDerived();
     void passForeignEnums();
+    void passQGadget();
     void metaObjectSize_data();
     void metaObjectSize();
     void metaObjectChecksum();
@@ -338,6 +339,44 @@ void tst_qqmlpropertycache::passForeignEnums()
 
 Q_DECLARE_METATYPE(MyEnum::Option1)
 
+QT_BEGIN_NAMESPACE
+class SimpleGadget
+{
+    Q_GADGET
+    Q_PROPERTY(bool someProperty READ someProperty)
+public:
+    bool someProperty() const { return true; }
+};
+
+// Avoids NeedsCreation and NeedsDestruction flags
+Q_DECLARE_TYPEINFO(SimpleGadget, Q_PRIMITIVE_TYPE);
+QT_END_NAMESPACE
+
+class GadgetEmitter : public QObject
+{
+    Q_OBJECT
+signals:
+    void emitGadget(SimpleGadget);
+};
+
+void tst_qqmlpropertycache::passQGadget()
+{
+    qRegisterMetaType<SimpleGadget>();
+
+    GadgetEmitter emitter;
+    engine.rootContext()->setContextProperty("emitter", &emitter);
+    QQmlComponent component(&engine, testFile("passQGadget.qml"));
+    QVERIFY(component.isReady());
+
+    QScopedPointer<QObject> obj(component.create(engine.rootContext()));
+    QVariant before = obj->property("result");
+    QVERIFY(before.isNull());
+    emit emitter.emitGadget(SimpleGadget());
+    QVariant after = obj->property("result");
+    QCOMPARE(QMetaType::Type(after.type()), QMetaType::Bool);
+    QVERIFY(after.toBool());
+}
+
 class TestClass : public QObject
 {
     Q_OBJECT