anchor.diff:  %% @end
   %%--------------------------------------------------------------------
   -spec receive_msg(Msg :: term(), Timeout :: timeout()) ->
  -    ok | {error, {timeout, UnreceivedMsg :: term()}}.
  +    {ok, ReceivedMsg :: term()} | {error, {timeout, UnreceivedMsg :: term()}}.
   receive_msg(Msg, Timeout) ->
       receive
  -        Msg -> ok
  +        Msg -> {ok, Msg}
       after
           Timeout -> {error, {timeout, Msg}}
       end.
  
positive.code: %% @end
  %%--------------------------------------------------------------------
  -spec receive_msg(Msg :: term()) ->
      ok | {error, {timeout, UnreceivedMsg :: term()}}.
  receive_msg(Msg) ->
      receive_msg(Msg, timer:seconds(0)).
  
  
negative.code: %% @equiv receive_any(0)
  %% @end
  %%--------------------------------------------------------------------
  -spec receive_any() -> {ok, ReceivedMsg :: term()} | {error, timeout}.
  receive_any() ->
      receive_any(timer:seconds(0)).
  
  