Similar to https://gist.github.com/ceedubs/c71490e9a4376a56dc01 but without higher kinds

NoImplicitFor.scala

trait Show[A] {
  def show(a: A): String
}

object Show {
  implicit val stringShow: Show[String] = new Show[String] {
    def show(a: String) = a
  }
}

trait NoImplicitFor[A]

sealed trait LowPriorityNoImplicitFor {
  implicit def lowPriorityNoImplicitFor[A]: NoImplicitFor[A] = new NoImplicitFor[A] {}
}

object NoImplicitFor extends LowPriorityNoImplicitFor {
  implicit def ambiguousPriorityNoImplicitFor1[A](implicit ev: A): NoImplicitFor[A] = new NoImplicitFor[A] {}
  implicit def ambiguousPriorityNoImplicitFor2[A](implicit ev: A): NoImplicitFor[A] = new NoImplicitFor[A] {}
}

object Test {
  implicitly[NoImplicitFor[Show[Int]]]

  // doesn't compile
  //implicitly[NoImplicitFor[Show[String]]]
}