PartialFunction challenge

gistfile1.scala

// Let's say I have 2 or more partial functions with different argument types
// I'm not interested in the result or the result types here
trait Test[A] { val pf: PartialFunction[A,_] }
object TestInt extends Test[Int] { val pf: PartialFunction[Int,String] = { case i => i.toString } }
object TestString extends Test[String] { val pf: PartialFunction[String,Int] = { case s => s.toInt } }

// I want to be able to chain these with orElse:
val pf = TestInt.pf orElse TestString.pf

// ...except that this doesn't work: neither pf.isDefinedAt(1) nor pf.isDefinedAt("str") work
// pf expects Int with String, which looks like a weird creature

// What would work is to get to a PartialFunction[Any,_] = { case o: A => … }
// for some reasons, I don't want to define it directly like this if I could avoid it
// Since Scala compiles this down to something like o.isInstanceOf[A], the obvious hacky solution would be
// making the following addition to the trait (if you're allowed to modify it):

trait Test[A<:AnyRef] {
  val pf: PartialFunction[A,_]
  def pfAny(implicit mf: Manifest[A]): PartialFunction[AnyRef,_] = {
    // due to erasure, you need to appease both the compiler and the runtime for type A
    case o: A if mf.erasure.isAssignableFrom(o.getClass) => pf(o)
  }
}

// but this gets ugly with our Int-based class: Int doesn't have getClass, so we need Integer
object TestInt extends Test[Integer] {
  val pf: PartialFunction[Integer,String] = { case i => i.toString }
}
// … not to mention that usage is awful:
TestInt.pfAny.apply(1: Integer)

// can you do better, ye Scala gods?
// isDefinedAt should accept only types of the arguments of the component partial functions

And yeah, I know there's this wonderful site called StackOverflow; maybe I should try it