anchor.diff:  
   -spec split_host_port(list(), list()) -> tuple().
   split_host_port(HostPort, DefaultPort) ->
  -    split_host_port(HostPort, DefaultPort, misc:is_ipv6()).
  +    split_host_port(HostPort, DefaultPort, is_ipv6()).
   
   -spec split_host_port(list(), list(), boolean()) -> tuple().
   split_host_port("[" ++ Rest, DefaultPort, true) ->
  
positive.code: 
  -spec localhost([] | [url]) -> string().
  localhost(Options) ->
      case misc:is_ipv6() of
          true ->
              case Options of
                  [] ->
  
negative.code:                                        | {cannot_listen, inet:posix()}
                                         | {address_not_allowed, string()}.
  is_good_address(Address) ->
      is_good_address(Address, is_ipv6()).
  
  is_good_address(Address, false) ->
      check_short_name(Address, ".");
  