experiment: refactor: represent object types with maps rather than a sorted list

src/lang_utils/env.ml

@@ -9,6 +9,7 @@ sig
   val dom : 'a t -> Dom.t
   val restrict : Dom.t -> 'a t -> 'a t
   val keys : 'a t -> key list
+  val values : 'a t -> 'a list
   val from_list : (key * 'a) list -> 'a t
   val from_list2 : key list -> 'a list -> 'a t
   val adjoin : 'a t -> 'a t -> 'a t
@@ -30,6 +31,7 @@ struct
     | Some v -> add k v acc
     | None -> acc) dom empty
   let keys env = List.map fst (bindings env)
+  let values env = List.map snd (bindings env)
   let from_list kxs = List.fold_left (fun env (k, x) -> add k x env) empty kxs
   let from_list2 ks xs = List.fold_left2 (fun env k x -> add k x env) empty ks xs
   let adjoin env1 env2 = union (fun _ x1 x2 -> Some x2) env1 env2