6 files changed, 32 insertions, 4 deletions

diff --git a/src/library/scala/NonNull.scala b/src/library/scala/NonNull.scala
new file mode 100644
index 0000000000..02a037ccf0
--- /dev/null
+++ b/src/library/scala/NonNull.scala
@@ -0,0 +1,13 @@
+/*                     __                                               *\
+**     ________ ___   / /  ___     Scala API                            **
+**    / __/ __// _ | / /  / _ |    (c) 2002-2005, LAMP/EPFL             **
+**  __\ \/ /__/ __ |/ /__/ __ |                                         **
+** /____/\___/_/ |_/____/_/ | |                                         **
+**                          |/                                          **
+\*                                                                      */
+
+// $Id: ScalaObject.scala 5390 2005-12-19 13:49:03Z dubochet $
+
+package scala;
+
+trait NonNull;
diff --git a/src/library/scala/UndefinedException.scala b/src/library/scala/UndefinedException.scala
new file mode 100644
index 0000000000..d88cb0a5ca
--- /dev/null
+++ b/src/library/scala/UndefinedException.scala
@@ -0,0 +1,12 @@
+/*                     __                                               *\
+**     ________ ___   / /  ___     Scala API                            **
+**    / __/ __// _ | / /  / _ |    (c) 2002, LAMP/EPFL                  **
+**  __\ \/ /__/ __ |/ /__/ __ |                                         **
+** /____/\___/_/ |_/____/_/ | |                                         **
+**                          |/                                          **
+**                                                                      **
+** $Id: MatchError.scala 5390 2005-12-19 13:49:03Z dubochet $
+\*                                                                      */
+package scala;
+
+final class UndefinedException extends RuntimeException;
diff --git a/src/library/scala/collection/mutable/DoubleLinkedList.scala b/src/library/scala/collection/mutable/DoubleLinkedList.scala
index 4b79ba534c..0fefcf6b04 100644
--- a/src/library/scala/collection/mutable/DoubleLinkedList.scala
+++ b/src/library/scala/collection/mutable/DoubleLinkedList.scala
@@ -19,7 +19,7 @@ package scala.collection.mutable;
  *  @version 1.0, 08/07/2003
  */
 [serializable]
-abstract class DoubleLinkedList[A, This <: DoubleLinkedList[A, This]] requires This
+abstract class DoubleLinkedList[A, This >: AllRef <: DoubleLinkedList[A, This]] requires This
     extends SingleLinkedList[A, This] {
 
     var prev: This = _;
diff --git a/src/library/scala/collection/mutable/SingleLinkedList.scala b/src/library/scala/collection/mutable/SingleLinkedList.scala
index 9ec97f39ff..52c2fdcd35 100644
--- a/src/library/scala/collection/mutable/SingleLinkedList.scala
+++ b/src/library/scala/collection/mutable/SingleLinkedList.scala
@@ -19,13 +19,13 @@ package scala.collection.mutable;
  *  @version 1.0, 08/07/2003
  */
 [serializable]
-abstract class SingleLinkedList[A, This <: SingleLinkedList[A, This]]
+abstract class SingleLinkedList[A, This >: AllRef <: SingleLinkedList[A, This]]
                requires This
                extends AnyRef with Seq[A] {
 
     var elem: A = _;
 
-    var next: This = _;
+    var next: This = null;
 
     def length: Int = 1 + (if (next == null) 0 else next.length);
 
diff --git a/src/library/scala/concurrent/MailBox.scala b/src/library/scala/concurrent/MailBox.scala
index 427d424b28..4463071f2e 100644
--- a/src/library/scala/concurrent/MailBox.scala
+++ b/src/library/scala/concurrent/MailBox.scala
@@ -137,7 +137,7 @@ trait ListQueueCreator {
 /** Efficient queue module creator based on linked lists. */
 trait LinkedListQueueCreator {
   import scala.collection.mutable.LinkedList;
-  def queueCreate[a <: AnyRef]: QueueModule[a] = new QueueModule[a] {
+  def queueCreate[a >: AllRef <: AnyRef]: QueueModule[a] = new QueueModule[a] {
     type t = Pair[LinkedList[a], LinkedList[a]]; // fst = the list, snd = last elem
     def make: t = {
       val l = new LinkedList[a](null, null);
diff --git a/src/library/scala/runtime/ScalaRunTime.scala b/src/library/scala/runtime/ScalaRunTime.scala
index 827e4cc223..77d46fc745 100644
--- a/src/library/scala/runtime/ScalaRunTime.scala
+++ b/src/library/scala/runtime/ScalaRunTime.scala
@@ -88,6 +88,9 @@ object ScalaRunTime {
       false
   }
 
+  def checkDefined[T >: AllRef](x: T): T =
+    if (x == null) throw new UndefinedException else x
+
   def Seq[a](xs: a*): Seq[a] = null; // interpreted specially by new backend.
 
   def booleanValue(x: BoxedBoolean): Boolean = if (x eq null) false else x.booleanValue();