ArrayBuffer.scala

 class Foo {
   import scala.collection.mutable.ArrayBuffer
   val elements = List(1,2,3)
   //ClassManifest is needed
   def map[T:ClassManifest](block: Int => T) = {
     val vals = ArrayBuffer[T]()
     elements foreach{ i => vals += block(i) }
     vals.toArray
   }
 }

// passed (scala-2.8.1)

ListBuffer.scala

 class Foo {
    import scala.collection.mutable.ListBuffer
    val elements = List(1,2,3)
    def map[T](block: Int => T) = {
      val vals = ListBuffer[T]()
      elements foreach{ i => vals += block(i) }
      vals.toList
    }
  }

// passed (scala-2.8.1)