case class Man[T]()
implicit def man[T] = Man[T]()

abstract class Exp[T:Man] {
  def mT = man[T]
}

case class Const[A:Man](x: A) extends Exp[A]

case class Node[A:Man, B:Man](base: Exp[A]) extends Exp[B] {
  def mA = man[A]
  def mB = man[B]
}

val m = Node[Int, String](Node[Double, Int](Const(3.14)))

val n = m match {
  case Node(Node(t)) => t
}
//At the REPL we get
//n: Exp[Any] = Const(3.14)

//scala> n.mT
//res0: Man[Any] = Man()

scala> val m = Node[java.io.File, StringBuffer](Node[String, java.io.File](Const("a string")))
m: Node[java.io.File,java.lang.StringBuffer] = Node(Node(Const(a string)))

scala> val n = m match {
     |   case Node(Node(t)) => t
     | }
n: Exp[Any] = Const(a string)