Fixup the implementation mess for QJSValue(QString)

Until now we were using a QV4::String without engine to
represent this case. But this leads to lots of quirks, where
we ended up trying to access the engine (or the internalclass/vtable)
of this string anyway.

Now just represent it by using an QString in QJSValuePrivate, and use
an empty value to represent it. This adds a little bit of code to
QJSValue and QJSEngine, but is more stable and maintainable in the
longer term.

Change-Id: I3358165ee64e788274225743a95dfb13346225cc
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>

1 files changed, 3 insertions, 4 deletions

diff --git a/src/qml/jsapi/qjsvalue_p.h b/src/qml/jsapi/qjsvalue_p.h
index bf839a6f1f..d8da664cc6 100644
--- a/src/qml/jsapi/qjsvalue_p.h
+++ b/src/qml/jsapi/qjsvalue_p.h
@@ -80,17 +80,16 @@ public:
         Q_ASSERT(!value.isEmpty());
     }
     QJSValuePrivate(const QString &s)
-        : PersistentValuePrivate(QV4::Encode::undefined())
-        , string(0, s)
+        : PersistentValuePrivate(QV4::Primitive::emptyValue().asReturnedValue())
+        , string(s)
     {
-        value.val = QV4::Encode(string.asReturned<QV4::String>());
     }
 
     QV4::ReturnedValue getValue(QV4::ExecutionEngine *e);
 
     static QJSValuePrivate *get(const QJSValue &v) { return v.d; }
 
-    QV4::String string;
+    QString string;
 };
 
 QT_END_NAMESPACE