proposition: Lemma binds_one_iff : binds x a (one (VarAsn B y b)) <-> x = y /\ a = b.
proof: Proof. clear. split. intros H1. intuition eauto using binds_one_1, binds_one_2. intros H1. intuition auto using binds_one_3. Qed.
imports: Coq.FSets.FSets Coq.Lists.List Coq.Logic.Decidable Metalib.CoqFSetDecide Metalib.CoqListFacts Metalib.LibTactics Metalib.MetatheoryAtom Metalib.LibTactics