proposition: Fact le0x (x : {t : T & T' t}) : Tagged T' (\bot : T' \bot) <= x.
proof: Proof. rewrite leEsig /=; case: comparableP (le0x (tag x)) => //=. by case: x => //= x px x0; rewrite x0 in px *; rewrite tagged_asE le0x. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(path fintype tuple bigop finset div prime finfun) mathcomp(finset)