anchor.diff:        Namespace :: file:filename_all(),
         IfAddrs   :: [ifaddrs()],
         Reason    :: term().
  +
  +-dialyzer({no_return, getifaddrs/2}).
   
   getifaddrs(Filter, Namespace)
     when (is_atom(Filter) orelse is_map(Filter)) andalso is_list(Namespace) ->
  
positive.code: info() ->
      prim_net:info().
  -else.
  -dialyzer({nowarn_function, info/0}).
  info() ->
      erlang:error(notsup).
  -endif.
  
negative.code:       Host    :: string(),
        Info    :: [address_info()],
        Reason  :: term().
  
  -dialyzer({no_return, getaddrinfo/1}).
  
  getaddrinfo(Host) when is_list(Host) ->
      getaddrinfo(Host, undefined).
  