code: public boolean changeBaseType(JSTypeExpression jsType) {
      if (jsType != null && !hasAnySingletonTypeTags()) {
        currentInfo.setBaseType(jsType);
        populated = true;
        return true;
      } else {
        return false;
      }
    }
docs: Changes a base type, even if one has already been set on currentInfo.
  
  @return {@code true} if the base type was changed successfully.