static <A> L<A> treeView_allNodes(TreeView<A> t) {
  new L<A> out;
  if (t == null) ret out;
  TreeView<A> parent;
  while ((parent = t.parent()) != null) t = parent;
  new L<TreeView<A>> stack;
  stack.add(t);
  while (nempty(stack)) {
    t = popLast(stack);
    out.add(t.node());
    addAll(stack, t.children());
  }
  ret out;
}