QmlJS: Avoid infinite loop with recursive prototypes.

src/libs/qmljs/qmljsinterpreter.h

@@ -397,6 +397,7 @@ public:
     QString className() const;
     void setClassName(const QString &className);
 
+    // not guaranteed to not recurse, use PrototypeIterator!
     const ObjectValue *prototype(const Context *context) const;
     void setPrototype(const Value *prototype);
 
@@ -422,6 +423,24 @@ private:
     QString _className;
 };
 
+class QMLJS_EXPORT PrototypeIterator
+{
+public:
+    PrototypeIterator(const ObjectValue *start, const Context *context);
+
+    bool hasNext();
+    const ObjectValue *peekNext();
+    const ObjectValue *next();
+
+    QList<const ObjectValue *> all();
+
+private:
+    const ObjectValue *m_current;
+    const ObjectValue *m_next;
+    QList<const ObjectValue *> m_prototypes;
+    const Context *m_context;
+};
+
 class QMLJS_EXPORT QmlObjectValue: public ObjectValue
 {
 public: