Proof using.
intros. induction l; simpl in *; auto; try congruence.
repeat break_match; simpl in *; intuition.
- subst. find_inversion. auto.
- repeat find_rewrite. auto.
Qed.

Lemma assoc_default_assoc_set :
forall l (k : K) (v : V) d,
assoc_default (assoc_set l k v) k d = v.