Proof using.
intros.
invcs H.
invcs H2.
- monad_unfold.
unfold NetHandler in *.
break_match_hyp.
+ unfold occurred in *.
find_apply_lem_hyp ClientNetHandler_lbcases; intuition; congruence.
+ unfold occurred in *.
find_apply_lem_hyp ServerNetHandler_lbcases; intuition;
break_exists; intuition; try congruence; [left|right];
fold LockServ_MultiParams in *; (* typeclass stuff *)
repeat find_rewrite; simpl.
* left. congruence.
* update_destruct_max_simplify; try congruence.
find_inversion.
repeat find_rewrite.
destruct (queue (nwState (evt_a e) Server)) eqn:?; try congruence.
exists (length l). simpl.
constructor.
apply Nth_snoc.
- monad_unfold.
find_apply_lem_hyp InputHandler_lbcases.
intuition; try congruence.
break_exists. intuition; congruence.
- unfold occurred in *. congruence.
Qed.

Lemma MsgLock_Locked :
forall c s,
event_step_star step_async step_async_init (hd s) ->
lb_step_execution lb_step_async s ->
weak_fairness lb_step_async label_silent s ->
now (occurred (MsgLock c)) s ->
eventually
(fun s => In (mkPacket Server (Client c) Locked)
(nwPackets (evt_a (hd s)))) s.