+ putDirect(exec->globalData(), exec->propertyNames().length, jsNumber(1), DontDelete | ReadOnly | DontEnum); // ECMA 15.11.7.5
+ putDirect(exec->globalData(), exec->propertyNames().prototype, prototype, DontDelete | ReadOnly | DontEnum);
+ m_errorStructure.set(exec->globalData(), this, ErrorInstance::createStructure(exec->globalData(), prototype));
+ ASSERT(m_errorStructure);
+ ASSERT(m_errorStructure->typeInfo().type() == ObjectType);
+}