使用 self 类型扩展 trait 时非法继承 [英] Illegal inheritance while extending trait with self type

问题描述

我对以下代码感到困惑:

I'm confused by the following code:

    trait T1 {
        type S
    }

    trait T2 {
      self: T1 =>

       case  class ClS(s: S)
    }

    object O extends T2 {

    }

它给出了以下错误消息:

It gives out the following error message:

非法继承；tests.O.type 不符合 tests.T2 的selftype tests.T2 with tests.T1

illegal inheritance; tests.O.type does not conform to tests.T2's selftype tests.T2 with tests.T1

怎么了?我用 T2 扩展 O 的原因是我想引用 O 中的 CLS 类，怎么能我做到了?

What's going wrong? the reason that I extend O with T2 is that I want to reference the class CLS in O, how can I achieve that?

推荐答案

trait T2 有个约定说:如果你继承我，你也应该继承T1.

trait T2 has a contract that says: If you inherit from me, you should also inherit from T1.

object O extends T2 with T1

然后您可能会收到一个错误，指出 type S 未定义.这是一件好事，因为它用于 CLS

You would then probably get an error that type S is not defined. Which is a good thing since it's used in the definition of CLS

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