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import language._
object ScalaZeee {
trait HFold[M[_], U] {
type Apply[E, A <: U] <: U
}
trait GenericCons[M[_], H, +T <: GenericList[M]] extends GenericList[M] {
val tail: T
override type Folded[N[X] >: M[X], U, F <: HFold[N, U]] = F#Apply[H, tail.Folded[N, U, F]]
}
val KNil: GenericList[Nothing] = ???
sealed trait GenericList[+M[_]] {
type Folded[N[X] >: M[X], U, F <: HFold[N, U]] <: U
}
}
object TypelevelUsage {
import ScalaZeee._
type T = GenericCons[Some, String, KNil.type]
val klist1: T = ???
type T2 = klist1.Folded[Option, Int, HFold[Option, Int]]
val count2: T2 = ???
count2.ensuring(x => true).toChar // trigger an implicit search
}
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