class Sass::Script::Parser

def paren
  return variable unless try_tok(:lparen)
  without_stop_at do
    start_pos = source_position
    e = map
    e.force_division! if e
    end_pos = source_position
    assert_tok(:rparen)
    e || node(Sass::Script::Tree::ListLiteral.new([]), start_pos, end_pos)
  end
end