fact: Parameter atom_fresh_for_list : forall (xs : list t), {x : atom | ~ List.In x xs}.
imports: Coq.Arith.Arith Coq.Arith.Max Coq.Classes.EquivDec Coq.Lists.List Coq.Structures.Equalities Coq.FSets.FSets Metalib.CoqListFacts Metalib.FSetExtra Metalib.FSetWeakNotin Metalib.LibTactics Lia