Scalaで型消去を回避する ref: http://qiita.com/mather314/items/67fdbf8293edc0200444

file0.scala

class A
class B extends A
class C extends A

def isType[T <: A](a: A) = a.isInstanceOf[T]
// <console>:9: warning: abstract type T is unchecked since it is eliminated by erasure
//        def isType[T <: A](a: A) = a.isInstanceOf[T]
//                                                 ^
// isType: [T <: A](a: A)Boolean

file1.txt

scala> isType[A](new A)
res11: Boolean = true

scala> isType[C](new B)
res12: Boolean = true  // 本当は (new B).isInstanceOf[C] => false

file2.scala

def isType[T <: A](a: A)(implicit e: scala.reflect.ClassTag[T]) = e.runtimeClass.isInstance(a)
//=> isType: [T <: A](a: A)(implicit e: scala.reflect.ClassTag[T])Boolean

file3.scala

scala> isType[C](new B)
res13: Boolean = false

file4.scala

import scala.reflect.ClassTag

def isType[T <: A : ClassTag](a: A) = implicitly[ClassTag[T]].runtimeClass.isInstance(a)

file5.scala

import scala.reflect.ClassTag

def isType[T <: A : ClassTag](a: A) = a match {
  case t: T => true
  case _ => false
}