fix(sn): Fix dialyzer warnings

apps/emqx_sn/src/emqx_sn_gateway.erl

@@ -473,10 +473,10 @@ handle_event(info, {datagram, SockPid, Data}, StateName,
              State = #state{sockpid = SockPid, channel = _Channel}) ->
     ?LOG(debug, "RECV ~p", [Data], State),
     Oct = iolist_size(Data),
-    emqx_pd:inc_counter(recv_oct, Oct),
+    inc_counter(recv_oct, Oct),
     try emqx_sn_frame:parse(Data) of
         {ok, Msg} ->
-            emqx_pd:inc_counter(recv_cnt, 1),
+            inc_counter(recv_cnt, 1),
             ?LOG(info, "RECV ~s at state ~s",
                  [emqx_sn_frame:format(Msg), StateName], State),
             {keep_state, State, next_event({incoming, Msg})}
@@ -597,8 +597,8 @@ handle_info(Info, State = #state{channel = Channel}) ->
    handle_return(emqx_channel:handle_info(Info, Channel), State).
 
 handle_ping(_PingReq, State) ->
-    emqx_pd:inc_counter(recv_oct, 2),
-    emqx_pd:inc_counter(recv_msg, 1),
+    inc_counter(recv_oct, 2),
+    inc_counter(recv_msg, 1),
     ok = send_message(?SN_PINGRESP_MSG(), State),
     {keep_state, State}.
 
@@ -1075,18 +1075,24 @@ transform_fun() ->
     fun(Packet, State) -> transform(Packet, FunMsgIdToTopicId, State) end.
 
 inc_incoming_stats(Type) ->
-    emqx_pd:inc_counter(recv_pkt, 1),
+    inc_counter(recv_pkt, 1),
     case Type == ?PUBLISH of
         true ->
-            emqx_pd:inc_counter(recv_msg, 1),
-            emqx_pd:inc_counter(incoming_pubs, 1);
+            inc_counter(recv_msg, 1),
+            inc_counter(incoming_pubs, 1);
         false -> ok
     end.
 
 inc_outgoing_stats(Type) ->
-    emqx_pd:inc_counter(send_pkt, 1),
-    (Type == ?SN_PUBLISH)
-        andalso emqx_pd:inc_counter(send_msg, 1).
+    inc_counter(send_pkt, 1),
+    case Type =:= ?SN_PUBLISH of
+        true -> inc_counter(send_msg, 1);
+        false -> ok
+    end.
 
 next_event(Content) ->
     {next_event, cast, Content}.
+
+inc_counter(Key, Inc) ->
+    _ = emqx_pd:inc_counter(Key, Inc),
+    ok.