class Opal::Rewriters::ForwardArgs

def on_args(node)
  if node.children.last && node.children.last.type == :forward_arg
    prev_children = node.children[0..-2]
    super(node.updated(nil,
      [
        *prev_children,
        s(:restarg, '$fwd_rest'),
        s(:blockarg, '$fwd_block')
      ]
    ))
  else
    super
  end
end