successor property

_TreeNode<V> successor
inherited

Return the next greatest element (or null)

Implementation 

_TreeNode<V> get successor {
  var node = this;
  if (node.right != null) {
    return node.right.minimumNode;
  }
  while (node.parent != null && node == node.parent.right) {
    node = node.parent;
  }
  return node.parent;
}