Fix issue with bindings to aliases that cannot yet be resolved

When an alias points to a child object which has not yet been
initialized, it's id won't have been registered yet, so setting up a
binding to it will result in a crash.

The fix is: when setting a binding target fails, and its target property
is an alias, queue them until all bindings have been set up, and try
again.

Task-number: QTBUG-57041
Change-Id: I4dc5a6d25c0a32fed9fd952c955e2006c76be45a
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>
(cherry picked from commit aa94c6c0469b0595f483f13ac88459f0035deef9)

2 files changed, 25 insertions, 0 deletions

diff --git a/tests/auto/qml/qqmllanguage/data/alias.16.qml b/tests/auto/qml/qqmllanguage/data/alias.16.qml
new file mode 100644
index 0000000000..4637aec58f
--- /dev/null
+++ b/tests/auto/qml/qqmllanguage/data/alias.16.qml
@@ -0,0 +1,15 @@
+import QtQuick 2.0
+import QtQuick.Window 2.0
+
+Window {
+    visible: true
+
+    property alias list: repeater.model
+
+    list: ["A", "B", "C"]
+
+    Repeater {
+        id: repeater
+    }
+}
+
diff --git a/tests/auto/qml/qqmllanguage/tst_qqmllanguage.cpp b/tests/auto/qml/qqmllanguage/tst_qqmllanguage.cpp
index 52decf9e11..c3b0fce35f 100644
--- a/tests/auto/qml/qqmllanguage/tst_qqmllanguage.cpp
+++ b/tests/auto/qml/qqmllanguage/tst_qqmllanguage.cpp
@@ -1872,6 +1872,16 @@ void tst_qqmllanguage::aliasProperties()
 
         QVERIFY(subObject->property("success").toBool());
     }
+
+    // Alias to sub-object with binding (QTBUG-57041)
+    {
+        // This is shold *not* crash.
+        QQmlComponent component(&engine, testFileUrl("alias.16.qml"));
+        VERIFY_ERRORS(0);
+
+        QScopedPointer<QObject> object(component.create());
+        QVERIFY(!object.isNull());
+    }
 }
 
 // QTBUG-13374 Test that alias properties and signals can coexist