gistfile1.scala

class !<:<[A, B]
implicit def any[A, B]: A !<:< B = new !<:<[A, B]
implicit def sub1[A, B >: A]: A !<:< B = new !<:<[A, B]
implicit def sub2[A, B >: A]: A !<:< B = new !<:<[A, B]

abstract class Tag
abstract class Unlimited
abstract class Unselected
abstract class Unskipped

class AddTag[TT, T, In, Out]

implicit def addTag1[TT, T <: TT, In]: AddTag[TT, T, In, In with TT] = null
implicit def addTag2[TT, T, In](implicit ev: T !<:< TT): AddTag[TT, T, In, In] = null

class RemoveTag[TT, In, Out]

implicit def removeUnlimited[T, Out1, Out2](implicit a: AddTag[Unselected, T, Tag, Out1],
  b: AddTag[Unskipped, T, Out1, Out2]): RemoveTag[Unlimited, T, Out2] = null
implicit def removeUnskipped[T, Out1, Out2](implicit a: AddTag[Unselected, T, Tag, Out1],
  b: AddTag[Unlimited, T, Out1, Out2]): RemoveTag[Unskipped, T, Out2] = null
implicit def removeUnselected[T, Out1, Out2](implicit a: AddTag[Unlimited, T, Tag, Out1],
  b: AddTag[Unskipped, T, Out1, Out2]): RemoveTag[Unselected, T, Out2] = null

class Query[T] {
  def limit[_ >: T <: Unlimited, T2](n: Int)(implicit a: RemoveTag[Unlimited, T, T2]): Query[T2] = this.asInstanceOf[Query[T2]]
  def skip[_ >: T <: Unskipped, T2](n: Int)(implicit a: RemoveTag[Unskipped, T, T2]): Query[T2] = this.asInstanceOf[Query[T2]]
  def select[_ >: T <: Unselected, T2]()(implicit a: RemoveTag[Unselected, T, T2]): Query[T2] = this.asInstanceOf[Query[T2]]
}

val q = new Query[Tag with Unlimited with Unselected with Unskipped]
q.limit(3)