class Opal::Rewriters::JsReservedWords

def on_restarg(node)

def m(*, **); end
because they may have no name
Restarg and kwrestarg are special cases 
def on_restarg(node)
  name, _ = *node
  if name
    node = node.updated(nil, [fix_var_name(name)], meta: { arg_name: name })
  end
  node
end