proposition: Lemma uniq_cons_3 : uniq E -> ~ In x (dom E) -> uniq ((x, a) :: E).
proof: Proof. clear. intros. change (uniq (x ~ a ++ E)). apply uniq_push; trivial. 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