class Sass::CSS

def flatten_rule(rule)
  while rule.children.size == 1 && rule.children.first.is_a?(Tree::RuleNode)
    child = rule.children.first
    if child.rule.first[0] == ?&
      rule.rule = [child.rule.first.gsub(/^&/, rule.rule.first)]
    else
      rule.rule = ["#{rule.rule.first} #{child.rule.first}"]
    end
    rule.children = child.children
  end
  flatten_rules(rule)
end