anchor.diff:  run_built_in(erlang, monitor, 2, [Type, Target], Info) ->
     #concuerror_info{
        monitors = Monitors,
  -     next_event = #event{event_info = EventInfo} = Event} = Info,
  +     event = #event{event_info = EventInfo} = Event} = Info,
     ?badarg_if_not(Type =:= process),
     {Target, As} =
       case Target of
  
positive.code:   {true, Info};
  
  run_built_in(erlang, halt, _, _, Info) ->
    #concuerror_info{next_event = Event} = Info,
    NewEvent = Event#event{special = [halt]},
    {no_return, Info#concuerror_info{next_event = NewEvent}};
  
  run_built_in(erlang, is_process_alive, 1, [Pid], Info) ->
    ?badarg_if_not(is_pid(Pid)),
  
negative.code:   {MessageOrAfter, ReceiveInfo} =
      has_matching_or_after(PatternFun, Timeout, Location, Info, blocking),
    #concuerror_info{
       event = NextEvent,
       flags = #process_flags{trap_exit = Trapping}
      } = UpdatedInfo =
      add_location_info(Location, ReceiveInfo),
  