Fix for linked lists closes #4080 and proves my...

Fix for linked lists closes #4080 and proves my desire not to ship
obviously broken code is even greater than my will to hold out for any
help. I threw in a free fix for this which I noticed while in there.

  scala> scala.collection.mutable.LinkedList[Int]().head

  res0: Int = 0

Also was reminded how useless tests can be:

  val ten = DoubleLinkedList(1 to 10: _*)
  ten.insert(DoubleLinkedList(11))
  // Post-insert position test
  require(ten.last == 11)

Fortunately a test confirming buggy behavior still serves a purpose by
breaking when you fix the bug which allowed it to pass, thus letting you
fix the broken test too. Life's (very) little compensations. Linked list
code should still be presumed broken. No review.

3 files changed, 15 insertions, 4 deletions

diff --git a/test/files/run/bug4080.check b/test/files/run/bug4080.check
new file mode 100644
index 0000000000..66ce31bb43
--- /dev/null
+++ b/test/files/run/bug4080.check
@@ -0,0 +1 @@
+LinkedList(1, 0, 2, 3)
diff --git a/test/files/run/bug4080.scala b/test/files/run/bug4080.scala
new file mode 100644
index 0000000000..92740ed776
--- /dev/null
+++ b/test/files/run/bug4080.scala
@@ -0,0 +1,12 @@
+import scala.collection.mutable.LinkedList
+
+object Test {
+  def main(args: Array[String]) {
+    val ll = LinkedList(1, 2, 3)
+    ll.insert(LinkedList(0))
+    println(ll)
+    val ll2 = LinkedList[Int]()
+    try println(ll2.head)
+    catch { case _ => () }
+  }
+}
diff --git a/test/files/run/t3361.scala b/test/files/run/t3361.scala
index 17af89a67c..892e36dbd9 100644
--- a/test/files/run/t3361.scala
+++ b/test/files/run/t3361.scala
@@ -39,10 +39,8 @@ object Test extends App {
 
   def insert_1 {
     val ten = DoubleLinkedList(1 to 10: _*)
-    ten.insert(DoubleLinkedList(11)) match {
-      case _: Unit => require(true)
-      case _ => require(false)
-    }
+    ten.append(DoubleLinkedList(11))
+
     // Post-insert size test
     require(11 == ten.size)
     // Post-insert data test