anchor.diff:                    Term.mkApp(t', cvars |> List.map mkFreeV), []
   
                   | None ->
  -                  let tsym = varops.fresh "Tm_arrow" in
  +                  let tsym = varops.mk_unique ("Tm_arrow_" ^ (Util.digest_of_string tkey.hash)) in
                     let cvar_sorts = List.map snd cvars in
                     let caption =
                       if Options.log_queries()
  
positive.code:     fresh:string -> string;
      string_const:string -> term;
      next_id: unit -> int;
  }
  let varops =
      let initial_ctr = 100 in
  
negative.code:      new_fvar=new_fvar;
       fresh=fresh;
       string_const=string_const;
       next_id=next_id;
       mk_unique=mk_unique}
  
   let unmangle (x:bv) : bv = {x with ppname=Util.unmangle_field_name x.ppname}
  (* ---------------------------------------------------- *)
  