}
      checkArgument(isValidPort(port), "Port number out of range: %s", hostPortString);
    }

    return new HostAndPort(host, port, hasBracketlessColons);
  }

  /**
   * Parses a bracketed host-port string, throwing IllegalArgumentException if parsing fails.
   *
   * @param hostPortString the full bracketed host-port specification. Port might not be specified.