proposition: Lemma cast_bseqEwiden m n (eq_mn : m = n) (bs : m.-bseq T) : cast_bseq eq_mn bs = widen_bseq (eq_leq eq_mn) bs.
proof: Proof. by case: n / eq_mn; rewrite widen_bseq_id. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat) mathcomp(seq choice fintype path)