proposition: Lemma disjoint_fsetI0 A B : [disjoint A & B] -> A `&` B = fset0.
proof: Proof. by rewrite -fsetI_eq0; move/eqP. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrnat eqtype ssrfun seq) mathcomp(choice path finset finfun fintype bigop)