anchor.diff:      assert_type(map, Src, Vst0),
       verify_live(Live, Vst0),
       verify_y_init(Vst0),
  -    foreach(fun (Term) -> assert_term(Term, Vst0) end, List),
  +    foreach(fun (Term) -> assert_not_fragile(Term, Vst0) end, List),
       Vst1 = heap_alloc(0, Vst0),
       Vst2 = branch_state(Fail, Vst1),
       Vst = prune_x_regs(Live, Vst2),
  
positive.code: 	is_integer(Sz) ->
  	    ok;
  	true ->
  	    assert_term(Sz, Vst0)
      end,
      Vst1 = heap_alloc(Heap, Vst0),
      Vst2 = branch_state(Fail, Vst1),
  
negative.code: assert_term(Src, Vst) ->
      get_term_type(Src, Vst),
      ok.
  
  assert_not_fragile(Src, Vst) ->
      case get_term_type(Src, Vst) of
          {fragile, _} -> error({fragile_message_reference, Src});
          _ -> ok
      end.
  
  assert_not_literal({x,_}) -> ok;
  assert_not_literal({y,_}) -> ok;
  