错误：case-to-case inheritance is prohibited. To overcome this limitation, use extractors to pattern match on non-leaf nodes.

错误：case-to-case inheritance is prohibited. To overcome this limitation, use extractors to pattern match on non-leaf nodes.

此处错误：样例类不可以作为继承链路中的叶子结点

解决方案：

不采用case，而是老老实实的构造参数和伴生对象。