Fix calling Qt.binding() on bound functions

Calling Qt.binding() on a bound function object is a valid use
case and used to work until Qt 5.8.

The problem was that we optimized the code in QQmlBinding and
QQmlJavascriptExpression to directly work on a QV4::Function,
so this wouldn't work anymore.

To fix this make sure recursive calls to Function.bind() are
unrolled (so that the BoundFunction's target is never a bound
function itself), then add the bound function as an optional
member to the QQmlBinding and use it's bound arguments if
present.

Task-number: QTBUG-61927
Change-Id: I472214ddd82fc2a1212efd9b769861fc43d2ddaf
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

1 files changed, 12 insertions, 0 deletions

diff --git a/tests/auto/qml/qqmlecmascript/tst_qqmlecmascript.cpp b/tests/auto/qml/qqmlecmascript/tst_qqmlecmascript.cpp
index c0cf123243..f40a9758f7 100644
--- a/tests/auto/qml/qqmlecmascript/tst_qqmlecmascript.cpp
+++ b/tests/auto/qml/qqmlecmascript/tst_qqmlecmascript.cpp
@@ -289,6 +289,7 @@ private slots:
     void withStatement();
     void tryStatement();
     void replaceBinding();
+    void bindingBoundFunctions();
     void deleteRootObjectInCreation();
     void onDestruction();
     void onDestructionViaGC();
@@ -7247,6 +7248,17 @@ void tst_qqmlecmascript::replaceBinding()
     delete obj;
 }
 
+void tst_qqmlecmascript::bindingBoundFunctions()
+{
+    QQmlEngine engine;
+    QQmlComponent c(&engine, testFileUrl("bindingBoundFunctions.qml"));
+    QObject *obj = c.create();
+    QVERIFY(obj != nullptr);
+
+    QVERIFY(obj->property("success").toBool());
+    delete obj;
+}
+
 void tst_qqmlecmascript::deleteRootObjectInCreation()
 {
     {