svoid test_structure_synchronizedTreeMap() {
  Map map = synchronizedTreeMap();
  S name = className(map);
  print(name);
  S s;
  print(s = struct(map));
  Map map2 = cast unstruct(s);
  assertEquals(name, className(map2));
  assertEquals(map, map2);
  
  map.put("c", "d");
  map.put("a", "b");
  map.put("d", "e");
  map.put("e", "f");
  print(s = struct(map));
  map2 = (Map) unstruct(s);
  assertEquals(name, className(map2));
  assertEquals(map, map2);
  
  print("OK");
}

Began life as a copy of #1015843