Proof using.
unfold raft_net_invariant_reboot, nextIndex_safety, reboot.
simpl.
intros.
subst.
repeat find_higher_order_rewrite.
update_destruct_simplify.
- unfold getNextIndex, assoc_default. simpl. omega.
- auto.
Qed.

(* Specifications: *)
Lemma nextIndex_safety_invariant :
forall net,
raft_intermediate_reachable net ->
nextIndex_safety net.