Proof using.
move => m.
elim => //= [|n l IH] failed h n'; first by rewrite remove_all_nil.
have H_cn := remove_all_cons name_eq_dec failed n l.
break_or_hyp; break_and; find_rewrite; first exact: IH.
rewrite /=.
case (adjacent_to_dec _ _) => H_dec' /=.
move => H_in.
case: H_in => H_in.
inversion H_in.
by left.
right.
exact: IH.
exact: IH.
Qed.

Lemma in_adjacent_exclude_in_exlude :
forall ns failed n h,
In (tot_map_name_inv n) (filter_rel adjacent_to_dec h (remove_all name_eq_dec failed ns)) ->
In (tot_map_name_inv n) (remove_all name_eq_dec failed ns) /\ adjacent_to h (tot_map_name_inv n).