scala - scala.Singleton 是纯编译器小说吗？

Question

Scala Language Specification在 §3.2.1 下说:

A stable type is either a singleton type or a type which is declared to be a subtype of trait scala.Singleton.

我找不到 scala.Singleton既不在源代码中，也不在 ScalaDoc 中，也不在二进制 jar 文件中。

尝试 REPL 结果:

scala> class Foo extends Singleton
<console>:9: error: illegal inheritance from final trait Singleton
       class Foo extends Singleton
                         ^
<console>:9: error: illegal inheritance; superclass Any
 is not a subclass of the superclass Object
 of the mixin trait ScalaObject
       class Foo extends Singleton
                 ^

在哪里scala.Singelton生活，它的​​目的是什么？

Answer 1

终于在这方面找到了一些东西:

The type Singleton is essentially an encoding trick for existentials with values. I.e.

T forSome { val x: T } 

is turned into

[x.type := X] T forSome { type X <:T with Singleton } 

来源:http://scala-programming-language.1934581.n4.nabble.com/scala-Singleton-td1940630.html