Phantom Types

gistfile1.txt

    object Phantom {

      type Nothing <: Any
      type Any
      
      def assume[T <: Any]: T
      
      class Function1[-T <: Any, +R <: Any] {
        def apply(x: T): R
      }
      
      class ImplicitFunction1[-T <: Any, +R <: Any] extends Function1[T, R] {
        def apply(implicit x: T): R
      }
      
      ... same for other arities ...
    }

    object X {
      type CanScare[Int] <: Phantom.Any
      def canScare: CanScare[Int] = Phantom.assume[CanScare[Int]]
    }
    
Rules:

 No mixing of phantom and non-phantom