目前在 Sass 中不推荐使用嵌套规则后的声明，在 为了通知用户即将进行的更改，并给他们时间进行更改 与之兼容的样式表。在未来的版本中，Dart Sass 将更改为 匹配纯 CSS 嵌套生成的顺序。Deprecation Warning: Sass's behavior for declarations that appear after nested
rules will be changing to match the behavior specified by CSS in an upcoming  
version. To keep the existing behavior, move the declaration above the nested 
rule. To opt into the new behavior, wrap the declaration in `& {}`.