proposition: Lemma binds_nil : binds x a (@nil (asn A B)) <-> False.
proof: Proof. clear. split. inversion 1. intuition. Qed.
imports: Coq.FSets.FSets Coq.Lists.List Coq.Logic.Decidable Metalib.CoqFSetDecide Metalib.CoqListFacts Metalib.LibTactics Metalib.MetatheoryAtom Metalib.LibTactics