XFAIL : tst_QScriptEngine::getSetGlobalObject() __defineGetter__ and co. does not work on the objects that have an interceptor

If we set a custom global object, we can't define getter/setter properties on it. That's too bad. What actually happens? How is the property written to our proxy object when _defineGetter_() is called? Can't we get the descriptor of the property and see that it's a getter/setter property, and delegate to it from our interceptor?