Type* TypeChecker::lookup(Env env, Id identifier){
  std::list<std::map<Id, Type*>>::reverse_iterator iter =  env_.contexts.rbegin();
  for(; iter != env_.contexts.rend(); iter++){
    Type* type = iter->find(identifier)->second;
      if(type != nullptr){
      return type;
    }
  }
  errorMessage = errorMessage + "\n" + "Error: No variable with Id " + identifier + " found";
  success = false;
  return nullptr;
}