proposition: Lemma uniq_cons_iff : uniq ((x, a) :: E) <-> uniq E /\ ~ In x (dom E).
proof: Proof. clear. split. eauto using uniq_cons_1, uniq_cons_2. intros [? ?]. auto using uniq_cons_3. Qed.
imports: Coq.FSets.FSets Coq.Lists.List Coq.Logic.Decidable Coq.Strings.String String Metalib.CoqFSetDecide Metalib.CoqListFacts Metalib.LibTactics Metalib.CoqFSetInterface Coq.Classes.Equivalence Coq.Classes.EquivDec Metalib.CoqEqDec