QtQml: Check for isReference() before trying to write back

If we neglect this we get an assert further down the line.

Amends commit a824a6f060ec3a0000d7349649a3ab9e0570ecaa.

Change-Id: Ib8fd01d329d5b45b27dfe117e168860c6a1d267f
Reviewed-by: Semih Yavuz <semih.yavuz@qt.io>
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
(cherry picked from commit 9c8d76b6ce036fe5e5f17cdcff3c6b22f15b4b65)
(cherry picked from commit c82d1eed1756ddbf0f51953ed9a51dff29d0ef90)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

4 files changed, 13 insertions, 2 deletions

diff --git a/src/qml/jsruntime/qv4sequenceobject.cpp b/src/qml/jsruntime/qv4sequenceobject.cpp
index a059ee93b7..1dd2654382 100644
--- a/src/qml/jsruntime/qv4sequenceobject.cpp
+++ b/src/qml/jsruntime/qv4sequenceobject.cpp
@@ -511,7 +511,7 @@ int Sequence::virtualMetacall(Object *object, QMetaObject::Call call, int index,
     switch (call) {
     case QMetaObject::ReadProperty: {
         const QMetaType valueType = valueMetaType(sequence->d());
-        if (!sequence->loadReference())
+        if (sequence->d()->isReference() && !sequence->loadReference())
             return 0;
         const QMetaSequence *metaSequence = sequence->d()->typePrivate()->extraData.ld;
         if (metaSequence->valueMetaType() != valueType)
@@ -529,7 +529,8 @@ int Sequence::virtualMetacall(Object *object, QMetaObject::Call call, int index,
         if (index < 0 || index >= metaSequence->size(storagePointer))
             return 0;
         metaSequence->setValueAtIndex(storagePointer, index, a[0]);
-        sequence->storeReference();
+        if (sequence->d()->isReference())
+            sequence->storeReference();
         break;
     }
     default:
diff --git a/tests/auto/qml/qqmlvaluetypeproviders/data/recursiveWriteBack.qml b/tests/auto/qml/qqmlvaluetypeproviders/data/recursiveWriteBack.qml
index d6707e37cd..e2c39d2d72 100644
--- a/tests/auto/qml/qqmlvaluetypeproviders/data/recursiveWriteBack.qml
+++ b/tests/auto/qml/qqmlvaluetypeproviders/data/recursiveWriteBack.qml
@@ -3,11 +3,16 @@ import Test
 
 MyTypeObject {
     property list<structured> l: [{i : 21}, {c: 22}, {p: {x: 199, y: 222}}]
+    property int aa: 5
 
     Component.onCompleted: {
         l[2].i = 4
         l[1].p.x = 88
         l[0].sizes[1].width = 19
         structured.p.x = 76
+
+        var sizesDetached = l[0].sizesDetached();
+        sizesDetached[1].width = 12;
+        aa = sizesDetached[1].width;
     }
 }
diff --git a/tests/auto/qml/qqmlvaluetypeproviders/testtypes.h b/tests/auto/qml/qqmlvaluetypeproviders/testtypes.h
index 096212822d..0267345281 100644
--- a/tests/auto/qml/qqmlvaluetypeproviders/testtypes.h
+++ b/tests/auto/qml/qqmlvaluetypeproviders/testtypes.h
@@ -98,6 +98,8 @@ public:
     const QList<QSizeF> &sizes() const { return m_sizes; }
     void setSizes(const QList<QSizeF> &sizes) { m_sizes = sizes; }
 
+    Q_INVOKABLE QList<QSizeF> sizesDetached() const { return m_sizes; }
+
 private:
 
     friend bool operator==(const StructuredValueType &a, const StructuredValueType &b)
diff --git a/tests/auto/qml/qqmlvaluetypeproviders/tst_qqmlvaluetypeproviders.cpp b/tests/auto/qml/qqmlvaluetypeproviders/tst_qqmlvaluetypeproviders.cpp
index 5f4d7c1042..930ac11fbe 100644
--- a/tests/auto/qml/qqmlvaluetypeproviders/tst_qqmlvaluetypeproviders.cpp
+++ b/tests/auto/qml/qqmlvaluetypeproviders/tst_qqmlvaluetypeproviders.cpp
@@ -476,6 +476,9 @@ void tst_qqmlvaluetypeproviders::recursive()
 
     MyTypeObject *m = qobject_cast<MyTypeObject *>(o.data());
     QCOMPARE(m->structured().p().x(), 76);
+
+    // Recursive write back into a list detached from the property.
+    QCOMPARE(m->property("aa").toInt(), 12);
 }
 
 void tst_qqmlvaluetypeproviders::date()