namespace trial {
  namespace protocol {
    namespace json {
      class error;

      enum errc { no_error = = 0, unexpected_token, invalid_key, 
                  invalid_value, incompatible_type, unbalanced_end_array, 
                  unbalanced_end_object, expected_end_array, 
                  expected_end_object };
      const std::error_category & error_category();
      enum errc to_errc(token::code::value);
      std::error_code make_error_code(json::errc e = no_error);
    }
  }
}namespace std {
  template<> struct is_error_code_enum<trial::protocol::json::errc>;
}