Allow setting values in value type group properties in "on" assignments

Assigning to a group property inside a property value source or
interceptor as part of an "on assignment" is perfectly valid. That is
because while "color" is a value type property, the on assignment means
we're actually setting easing.type (in the example and test) on the
property value source, not the color, and that one is a QObject. The
same goes for interceptors.

Change-Id: I505a658977a578894d6dfb00bf5c65b41e42b12f
Task-number: QTBUG-56600
Reviewed-by: Michael Brasser <michael.brasser@live.com>
(cherry picked from commit 2659c308792967322564b5088e0e21bb371e0283)

src/qml/compiler/qqmlpropertyvalidator.cpp

@@ -196,7 +196,13 @@ QVector<QQmlCompileError> QQmlPropertyValidator::validateObject(int objectIndex,
         }
 
         if (binding->type >= QV4::CompiledData::Binding::Type_Object && (pd || binding->isAttachedProperty())) {
-            const QVector<QQmlCompileError> subObjectValidatorErrors = validateObject(binding->value.objectIndex, binding, pd && QQmlValueTypeFactory::metaObjectForMetaType(pd->propType()));
+            const bool populatingValueTypeGroupProperty
+                    = pd
+                      && QQmlValueTypeFactory::metaObjectForMetaType(pd->propType())
+                      && !(binding->flags & QV4::CompiledData::Binding::IsOnAssignment);
+            const QVector<QQmlCompileError> subObjectValidatorErrors
+                    = validateObject(binding->value.objectIndex, binding,
+                                     populatingValueTypeGroupProperty);
             if (!subObjectValidatorErrors.isEmpty())
                 return subObjectValidatorErrors;
         }

tests/auto/qml/qqmllanguage/data/groupPropertyInPropertyValueSource.qml

@@ -0,0 +1,11 @@
+import QtQuick 2.0
+
+Rectangle {
+    ColorAnimation on color {
+        id: animation
+        from: "red"
+        to: "darkgray"
+        duration: 250
+        easing.type: Easing.InOutQuad
+    }
+}

tests/auto/qml/qqmllanguage/tst_qqmllanguage.cpp

@@ -38,6 +38,7 @@
 #include <QFont>
 #include <QQmlFileSelector>
 #include <QFileSelector>
+#include <QEasingCurve>
 
 #include <private/qqmlproperty_p.h>
 #include <private/qqmlmetatype_p.h>
@@ -275,6 +276,8 @@ private slots:
 
     void thisInQmlScope();
 
+    void valueTypeGroupPropertiesInBehavior();
+
 private:
     QQmlEngine engine;
     QStringList defaultImportPathList;
@@ -4619,6 +4622,20 @@ void tst_qqmllanguage::thisInQmlScope()
     QCOMPARE(o->property("y"), QVariant(42));
 }
 
+void tst_qqmllanguage::valueTypeGroupPropertiesInBehavior()
+{
+    QQmlEngine engine;
+    QQmlComponent component(&engine, testFileUrl("groupPropertyInPropertyValueSource.qml"));
+    VERIFY_ERRORS(0);
+    QScopedPointer<QObject> o(component.create());
+    QVERIFY(!o.isNull());
+
+    QObject *animation = qmlContext(o.data())->contextProperty("animation").value<QObject*>();
+    QVERIFY(animation);
+
+    QCOMPARE(animation->property("easing").value<QEasingCurve>().type(), QEasingCurve::InOutQuad);
+}
+
 QTEST_MAIN(tst_qqmllanguage)
 
 #include "tst_qqmllanguage.moc"