proposition: Lemma val_tcast m n (eq_mn : m = n) (t : m.-tuple T) : tcast eq_mn t = t :> seq T.
proof: Proof. by case: n / eq_mn. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat) mathcomp(seq choice fintype path)