Merge branch 'master' into execution-context

Conflicts:
	src/library/scala/package.scala

1 files changed, 54 insertions, 0 deletions

diff --git a/test/files/pos/existentials-harmful.scala b/test/files/pos/existentials-harmful.scala
new file mode 100644
index 0000000000..8722852e8a
--- /dev/null
+++ b/test/files/pos/existentials-harmful.scala
@@ -0,0 +1,54 @@
+// a.scala
+// Mon Jul 11 14:18:26 PDT 2011
+
+object ExistentialsConsideredHarmful {
+  class Animal(val name: String)
+  object Dog extends Animal("Dog")
+  object Sheep extends Animal("Sheep")
+
+  trait Tools[A] {
+    def shave(a: A): A
+  }
+  def tools[A](a: A): Tools[A] = null // dummy
+
+  case class TransportBox[A <: Animal](animal: A, tools: Tools[A]) {
+    def label: String = animal.name
+  }
+
+  // 1.
+  def carry[A <: Animal](box: TransportBox[A]): Unit = {
+    println(box.animal.name+" got carried away")
+  }
+
+  val aBox =
+    if (math.random < 0.5)
+      TransportBox(Dog, tools(Dog))
+    else
+      TransportBox(Sheep, tools(Sheep))
+
+  // 2.
+  //aBox.tools.shave(aBox.animal)
+
+  // Use pattern match to avoid opening the existential twice
+  aBox match {
+    case TransportBox(animal, tools) => tools.shave(animal)
+  }
+
+  abstract class BoxCarrier[R <: Animal](box: TransportBox[R]) {
+    def speed: Int
+
+    def talkToAnimal: Unit = println("The carrier says hello to"+box.animal.name)
+  }
+
+  // 3.
+  //val bc = new BoxCarrier(aBox) {
+
+  // Use pattern match to avoid opening the existential twice
+  // Type annotation on bc is required ... possible compiler bug?
+  // val bc : BoxCarrier[_ <: Animal] = aBox match {
+  val bc = aBox match {
+    case tb : TransportBox[a] => new BoxCarrier(tb) {
+      def speed: Int = 12
+    }
+  }
+}