双@ in型

Question

在下面的例子中，double at (@@)的含义是什么？

trait LowPriorityBijections {

  implicit def fromInjection[A, B](implicit inj: Injection[A, B]): Bijection[A] =
    new AbstractBijection[A, B @@ Rep[A]] {
    }
}

Answer 1

它是在com.twitter.bijection package.class中声明的类型别名：

/**
 * Tag a type `T` with `Tag`. The resulting type is a subtype of `T`.
 *
 * The resulting type is used to discriminate between type class instances.
 */
type @@[T, Tag] = T with Tagged[Tag]

你也可以探源。