broken type spec for socket:sendto/4 in OTP-27.2

[RoadRunnr]

Describe the bug

Between 27.1.3 and 27.2 the type spec for socket:sendto/4 was changed. The updated type spec does no longer allow nowait as the value for the 4th parameter.

The implementation has not changed and based on the implementation nowait is clearly valid.

These lines https://github.com/erlang/otp/blob/OTP-27.1.3/lib/kernel/src/socket.erl#L3727-L3728 from 27.1.3 have been lost in PR-8986

To Reproduce

Run dialyzer on this

-module(sock).

-export([sendto/4]).

family({_,_,_,_}) -> inet;
family({_,_,_,_,_,_,_,_}) -> inet6.

sendto(Socket, IP, Port, Data) ->
    Dest = #{family => family(IP),
             addr => IP,
             port => Port},
    case socket:sendto(Socket, Data, Dest, nowait) of
        ok -> ok;
        Other  ->
            logger:debug("sendto(~p) failed with: ~p", [Dest, Other]),
            ok
    end.

Results in this error:

Line 12 Column 10: The contract socket:sendto(Socket::socket(),Data::iodata(),Dest::sockaddr(),Flags::[any()]) -> Result when Result :: 'ok' | {'ok',RestData::binary()} | {'error',Reason} | {'error',{Reason,RestData::binary()}}, Reason :: posix() | 'closed' | invalid();(Socket::socket(),Data::iodata(),Cont::select_info(),TimeoutOrHandle::dynamic()) -> Result when Result :: 'ok' | {'ok',RestData::binary()} | {'error',Reason} | {'error',{Reason,RestData::binary()}}, Reason :: posix() | 'closed' | invalid() cannot be right because the inferred return for sendto(Socket::any(),Data::any(),Dest::#{'addr':={_,_,_,_} | {_,_,_,_,_,_,_,_}, 'family':='inet' | 'inet6', 'port':=_},'nowait') on line {12,10} is any()

Used to work in 27.1

Expected behavior
Call is not reported as violating the function specification.

Affected versions

27.2

[bmk]

Hi,

Could you please provide the exact dialyzer command?

Regards,
/Micael

[RoadRunnr]

@bmk

Save the sample snippet to sock.erl, then debug compile sock.erl and make sure you have a plt:

$ erlc +debug_info sock.erl
$ dialyzer --build_plt --apps erts kernel stdlib compiler crypto parsetools
  Creating PLT /home/aschultz/.cache/erlang/.dialyzer_plt ... done in 0m25.79s
done (passed successfully)

Then run dialyzer on the sock.beam produced by erlc:

$ dialyzer -Wno_return sock.beam 
  Checking whether the PLT /home/aschultz/.cache/erlang/.dialyzer_plt is up-to-date... yes
  Proceeding with analysis...
sock.erl:12:10: The contract socket:sendto
          (Socket :: socket(),
          Data :: iodata(),
          Dest :: sockaddr(),
          Flags :: [any()]) ->
             Result
             when
                 Result ::
                     'ok' |
                     {'ok', RestData :: binary()} |
                     {'error', Reason} |
                     {'error', {Reason, RestData :: binary()}},
                 Reason :: posix() | 'closed' | invalid();
         (Socket :: socket(),
          Data :: iodata(),
          Cont :: select_info(),
          TimeoutOrHandle :: dynamic()) ->
             Result
             when
                 Result ::
                     'ok' |
                     {'ok', RestData :: binary()} |
                     {'error', Reason} |
                     {'error', {Reason, RestData :: binary()}},
                 Reason :: posix() | 'closed' | invalid() cannot be right because the inferred return for sendto
         (Socket :: any(),
          Data :: any(),
          Dest ::
              #{'addr' := {_, _, _, _} | {_, _, _, _, _, _, _, _},
                'family' := 'inet' | 'inet6',
                'port' := _},
          'nowait') on position 12:10 is 
          any()
 done in 0m0.23s
done (warnings were emitted)

Before 27.2 the above used to work without warnings.

[IngelaAndin]

Fixed by #9295