proposition: Lemma sig_bij_on : {on [pred _ | true], bijective sig}.
proof: Proof. exact/onW_bij/sig_bij. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(path fintype tuple bigop finset div prime finfun) mathcomp(finset)