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jimmydivvy/ExistantialTest.scala

Created May 25, 2018 08:51
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ExistantialTest.scala
object ExistentialTest {
case class Box[T]()
case class Pair[T](a: Box[T], b: Box[T])
val pair: Pair[_] = ???
val pair2 = Pair(pair.a, pair.b)
}
@AndreasKostler
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AndreasKostler commented May 25, 2018 •
edited
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    object ExistentialTest {

    case class Box[T]()

    case class Pair[F[x] <: Box[x], T](a: F[T], b: F[T]) {
      type Inner = T
    }


    val pair = Pair(Box[Int], Box[Int])

    val pair2 = Pair(pair.a, pair.b)

  }

@AndreasKostler
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object ExistentialTest {
    import scala.language.existentials


    case class Box[T](value: T)
    case class Pair(a: Box[T] forSome { type T } , b: Box[T]  forSome { type T } ) {
    }

    val pair: Pair = Pair(Box[Int](42), Box[Int](42))

    val pair2 = Pair(pair.a, pair.b)

  }

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