classtag.scala

class A
class B extends A
class C extends B

val a = new A
val b = new B
val c = new C

def f[T : ClassTag](a: A) = a match {
  case _: T => "is given type"
  case _ => "NOT given type"
}

f[B](c)
// => "is given type"

f[C](c)
// => "is given type"

f[C](a)
// => "NOT given type"