Get ClassTag from within specialized class

When I have a @specialized class, I retain the information about what primitive my type is. Is there a fast way to get a ClassTag[T], e.g. to create arrays?

This does not compile, because no ClassTag[T] is available

class Foo[@specialized T] {
  def bar: Array[T] = new Array[T]
}

This works, but I want to avoid passing the ClassTag

class Foo[@specialized T: ClassTag] {
  def bar: Array[T] = new Array[T]
}

This works, but is slow:

class Foo[@specialized T] {
  def bar: Array[T] = new Array[T]

  implicit def classTag: ClassTag[T] = {
    val name = getClass.getName
    if(name.endsWith("$I$sp") ClassTag.Int
    else if(name.endsWith("$L$sp") ClassTag.Long
    else ??? // you get the idea
  }
}