相关疑难解决方法(0)

我想尝试编写一个类型,其方法可以是同类的,并返回相同类型的值:

object SimpleTest {
  trait Foo extends Product with Serializable {
    type Self <: Foo
    def bar: Self
  }

  case class X() extends Foo {
    type Self = X
    def bar = this
  }

  case class Y() extends Foo {
    type Self = Y
    def bar = this
  }


  trait TC[A]

  implicit val tc: TC[Foo] = new TC[Foo] { }

  def tester[A: TC](x: Seq[A]) = "foo"

  // tester(Seq(X(), Y()))
}

不幸的是,注释掉的行调用tester失败并出现以下错误(Scala 2.10):

Error: could not find implicit value …