(* Prenex Implicits and renaming. *)
Notation sval := (@proj1_sig _ _).Notation "@ 'sval'" := (@proj1_sig) (at level 10, format "@ 'sval'").

(* Specifications: *)
Lemma svalP : forall u : sig P, P (sval u).
Lemma s2valP u : P (s2val u).
Lemma s2valP' u : Q (s2val u).