specific-missing-type.scala

import annotation.unchecked.uncheckedVariance
import reflect.runtime.universe.TypeTag

package object stuff {
  // required for the better ??? operator
  type MyTypeTag[+A] = TypeTag[A @uncheckedVariance]
  
  def ???[A](implicit tag: MyTypeTag[A]): A = 
    throw new NotImplementedError(s"unimplemented value of type ${tag.tpe}")
}