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object approximateUnion {
trait C[+T]
trait D
trait E
trait X[-T]
{
trait A extends C[A] with D
trait B extends C[B] with D
val coin = true
val x = if (coin) new A{} else new B{}
val y = Some(if (coin) new A{} else new B{} )
val xtest: C[A | B] & D = x
val ytest: Some[C[A | B] & D] = y
}
{
trait A extends C[X[A]] with D
trait B extends C[X[B]] with D with E
val coin = true
val x = if (coin) new A{} else new B{}
val y = Some(if (coin) new A{} else new B{})
val xtest: C[X[A & B]] & D = x
val ytest: Some[C[X[A & B]] & D] = y
}
}
object approximateUnion2 {
trait C[T]
trait D
trait E
trait X[-T]
{
trait A extends C[A] with D
trait B extends C[B] with D
val coin = true
val x = if (coin) new A{} else new B{}
val y = Some(if (coin) new A{} else new B{})
val xtest: C[_ >: A & B <: A | B] & D = x
val ytest: Some[C[_ >: A & B <: A | B] & D] = y
}
{
trait A extends C[X[A]] with D
trait B extends C[X[B]] with D with E
val coin = true
val x = if (coin) new A{} else new B{}
val y = Some(if (coin) new A{} else new B{})
val xtest: C[_ >: X[A | B] <: X[A & B]] & D = x
val ytest: Some[C[_ >: X[A | B] <: X[A & B]]] = y
}
}
object approximateUnion3 {
trait C[-T]
trait D
trait E
trait X[-T]
{
trait A extends C[A] with D
trait B extends C[B] with D
val coin = true
val x = if (coin) new A{} else new B{}
val y = Some(if (coin) new A{} else new B{})
val xtest: C[A & B] & D = x
val ytest: Some[C[A & B] & D] = y
}
{
trait A extends C[X[A]] with D
trait B extends C[X[B]] with D with E
val coin = true
val x = if (coin) new A{} else new B{}
val y = Some(if (coin) new A{} else new B{})
val xtest: C[X[A | B]] & D = x
val ytest2: Some[C[X[A | B]] & D] = y
}
}
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