code: boolean declareParam(JSTypeExpression jsType, String parameter) {
      lazyInitInfo();
      if (info.parameters == null) {
        info.parameters = new LinkedHashMap<>();
      }
      if (!info.parameters.containsKey(parameter)) {
        info.parameters.put(parameter, jsType);
        return true;
      } else {
        return false;
      }
    }
docs: Declares a parameter. Parameters are described using the {@code @param}
  annotation.
  
  @param jsType the parameter's type, it may be {@code null} when the
  {@code @param} annotation did not specify a type.
  @param parameter the parameter's name