Hint Resolve @list_cspec.

(* Specifications: *)
Lemma comp_antisym:  forall {A} (cmp: A -> A -> comparison) (cspec: CompSpec' cmp),
forall x y, Lt = cmp x y <-> Gt = cmp y x.
Lemma NoDup_rsort_uniq:
forall {A} (cmp: A -> A -> comparison) (cspec: CompSpec' cmp),
forall  l, NoDup (rsort_uniq cmp l).
Lemma Forall_sortu:
forall  {A} (f: A -> Prop) (cmp: A -> A -> comparison) l,
Forall f l -> Forall f  (rsort_uniq cmp l).
Lemma rsort_uniq_in:
forall {A} (R: A -> A -> comparison)
(EQ: forall a b, (a=b) <-> (Eq = R a b))
x l,
List.In x (rsort_uniq  R l) <-> List.In x l.