proposition: Lemma prl_ne1_surj_rec i j (f := prl_can_fun S): gle (psr S) i j -> surjection (f j) -> surjection (f i).
proof: Proof. move => lij sa. move:(prl_can_fun_prop lij)(sjf lij); rewrite -/f; move => [sc ->] sd. by apply: compose_fs. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat)