End VAL_CASTED.
(** As a consequence, casting twice is equivalent to casting once. *)

(* Specifications: *)
Lemma cast_val_casted:
forall v ty m, val_casted v ty -> sem_cast v ty ty m = Some v.
Lemma cast_idempotent:
forall v ty ty' v' m, sem_cast v ty ty' m = Some v' -> sem_cast v' ty' ty' m = Some v'.