#[global]
Hint Resolve lel_refl lel_cons_cons lel_cons lel_nil lel_nil nil_cons:
datatypes.
(******************************)
(** ** Set inclusion on list  *)
(******************************)
Section SetIncl.
Variable A : Type.
Definition incl (l m:list A) := forall a:A, In a l -> In a m.
#[local]
Hint Unfold incl : core.

Lemma incl_l_nil : forall l, incl l [] -> l = [].