Lots of work hardening matching on sequences.

one long-standing bug which actually had a test case testing its
bugginess (which is to say, when I fixed the bug, the test case failed.)
This:

-    def doMatch4(xs:Seq[Char]) = xs match {
-      case Seq(x, y, _*) => x::y::Nil
-      case Seq(x, y, z, w) => List(z,w) // redundant!
-    }

...should never have compiled - which must have been recognized
on some level given the "redundant!" comment, but it never made
it into neg/.

3 files changed, 28 insertions, 4 deletions

diff --git a/test/files/neg/pat_unreachable.check b/test/files/neg/pat_unreachable.check
new file mode 100644
index 0000000000..4e1463d591
--- /dev/null
+++ b/test/files/neg/pat_unreachable.check
@@ -0,0 +1,7 @@
+pat_unreachable.scala:5: error: unreachable code
+    case Seq(x, y, z, w) => List(z,w) // redundant!
+                                ^
+pat_unreachable.scala:9: error: unreachable code
+    case Seq(x, y) => List(x, y)
+                          ^
+two errors found
diff --git a/test/files/neg/pat_unreachable.scala b/test/files/neg/pat_unreachable.scala
new file mode 100644
index 0000000000..c07be8edf0
--- /dev/null
+++ b/test/files/neg/pat_unreachable.scala
@@ -0,0 +1,20 @@
+
+object Test extends Application {
+  def unreachable1(xs:Seq[Char]) = xs match {
+    case Seq(x, y, _*) => x::y::Nil
+    case Seq(x, y, z, w) => List(z,w) // redundant!
+  }
+  def unreachable2(xs:Seq[Char]) = xs match {
+    case Seq(x, y, _*) => x::y::Nil
+    case Seq(x, y) => List(x, y)
+  }
+
+  def not_unreachable(xs:Seq[Char]) = xs match {
+    case Seq(x, y, _*) => x::y::Nil
+    case Seq(x) => List(x)
+  }
+  def not_unreachable2(xs:Seq[Char]) = xs match {
+    case Seq(x, y) => x::y::Nil
+    case Seq(x, y, z, _*) => List(x,y)
+  }
+}
\ No newline at end of file
diff --git a/test/files/neg/patternalts.scala b/test/files/neg/patternalts.scala
index 62d0325a8b..513b81eb5e 100644
--- a/test/files/neg/patternalts.scala
+++ b/test/files/neg/patternalts.scala
@@ -2,7 +2,4 @@ object Test {
   List(1) match {
     case List(x) | List() => Console.println(x)
   }
-  List(2) match {
-    case List(_: Int) | List() => Console.println()
-  }
-}
+}
\ No newline at end of file