anchor.diff:                            bounds_probs
         in
         let (bound, sub_probs, wl) =
  -          meet_or_join (if flip then U.mk_conj else U.mk_disj) bounds_typs env wl
  +          let mk_conj t1 t2 =
  +              if is_t_true t1 then t2
  +              else if is_t_true t2 then t1
  +              else U.mk_conj t1 t2
  +          in
  +          let mk_disj t1 t2 =
  +              if is_t_true t1 then U.t_true
  +              else if is_t_true t2 then U.t_true
  +              else U.mk_disj t1 t2
  +          in
  +          meet_or_join (if flip then mk_conj else mk_disj) bounds_typs env wl
         in
         let bound_typ, (eq_prob, wl') =
             let flex_u = flex_uvar_head this_flex in
  
positive.code: module Const = FStar.Parser.Const
  
  let print_ctx_uvar ctx_uvar = Print.ctx_uvar_to_string ctx_uvar
  
  (* ------------------------------------------------*)
  (* <guard_formula ops> Operations on guard_formula *)
  
negative.code:                   let t1_base, p1_opt = base_and_refinement_maybe_delta false env t1 in
                    let t2_base, p2_opt = base_and_refinement_maybe_delta false env t2 in
                    let combine_refinements t_base p1_opt p2_opt =
                        let refine x t =
                            if is_t_true t then x.sort
                            else U.refine x t
                        in
                        match p1_opt, p2_opt with
                        | Some (x, phi1), Some(y, phi2) ->
                          let x = freshen_bv x in
                          let subst = [DB(0, x)] in
                          let phi1 = SS.subst subst phi1 in
                          let phi2 = SS.subst subst phi2 in
                          refine x (op phi1 phi2)
  
                        | None, Some (x, phi)
                        | Some(x, phi), None ->
                          let x = freshen_bv x in
                          let subst = [DB(0, x)] in
                          let phi = SS.subst subst phi in
                          refine x (op U.t_true phi)
  
                        | _ ->
                          t_base
  