anchor.diff:  
   let compile_op_lid n s r = [mk_ident(compile_op n s r, r)] |> lid_of_ids
   
  -let op_as_term env arity rng op : option<S.term> =
  +let op_as_term env arity op : option<S.term> =
     let r l dd = Some (S.lid_as_fv (set_lid_range l (range_of_id op)) dd None |> S.fv_to_tm) in
     let fallback () =
       match Ident.text_of_id op with
  
positive.code:         in
          match (unparen rel).tm with
          | Op (id, _) ->
              begin match op_as_term env 2 Range.dummyRange id with
              | Some t -> is_impl_t t
              | None -> false
              end
  
negative.code: 
      | Op(s, args) ->
        begin
        match op_as_term env (List.length args) s with
        | None ->
          raise_error (Errors.Fatal_UnepxectedOrUnboundOperator,
                       "Unexpected or unbound operator: " ^
  