proposition: Lemma tupleP u : tuple1_spec u.
proof: Proof. case: u => [[|x s] //= sz_s]; pose t := @Tuple n _ s sz_s. by rewrite (_ : Tuple _ = [tuple of x :: t]) //; apply: val_inj. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat) mathcomp(seq choice fintype path)