anchor.diff:            let flags = filter_out_lcomp_cflags rc.residual_flags in
             Some ({rc with residual_typ=BU.map_opt rc.residual_typ (norm cfg env [])})
          | _ -> lopt
  -
   
   and rebuild (cfg:cfg) (env:env) (stack:stack) (t:term) : term =
     (* Pre-condition: t is in either weak or strong normal form w.r.t env, depending on *)
  
positive.code: 
              | _ -> None
              end
          | _ -> None
      in
      let maybe_auto_squash t =
  
negative.code:         | Some false -> tm
          | None -> tm
          end
      | Tm_match _ ->
          begin match is_const_match tm with
          | Some true -> w U.t_true
          | Some false -> w U.t_false
          | None -> tm
          end
      | _ -> tm
  
  let maybe_simplify cfg env stack tm =
  