anchor.diff:      false = T,  %% assert
       recv(Bin, S);
   
  -%% Check whether or not to read more after a throttle_cb timeout.
  +%% Make a new throttling callback after a timeout.
   transition(throttle, #transport{throttled = B} = S) ->
  -    true = B,  %% assert
  +    true = false /= B,  %% assert
       throttle(S);
   
   %% Capabilties exchange has decided on whether or not to run over TLS.
  
positive.code: %% transition/2
  
  %% Initial incoming message when we might need to upgrade to TLS:
  %% don't request another message until we know.
  transition({tcp, Sock, Bin}, #transport{socket = Sock,
                                          parent = Pid,
                                          frag = Head,
  
negative.code: %% No fragment to flush or not receiving messages.
  flush(#transport{frag = Frag, throttled = B} = S)
    when Frag == <<>>;
         B /= false ->
      S;
  
  %% Messages have been received since last timer expiry.
  