1
我有一個和特質,看起來像如下:泛型類型和類型不匹配
sealed trait Sum[+A, +B]
final case class Failure[A](value: A) extends Sum[A, Nothing]
final case class Success[B](value: B) extends Sum[Nothing, B]
當我嘗試創建一個新的變量爲:
val s1: Sum[Int, Nothing] = Success(4)
我有以下錯誤:
Error:(5, 41) type mismatch;
found : Int(4)
required: Nothing
val s1: Sum[Int, Nothing] = Success(4)
爲什麼?
爲什麼這是工作:
val s1: Sum[Int, Int] = Success(4)