Tighter pattern matching hits the street.

is final and does not conform to the pattern, it will no longer compile.
See all the exciting things you can no longer do:

  "bob".reverse match { case Seq('b', 'o', 'b') => true } // denied!
  "bob".toArray match { case Seq('b', 'o', 'b') => true } // rejected!
  final class Dunk
  def f3(x: Dunk) = x match { case Seq('b', 'o', 'b') => true } // uh-uh!

And so forth.  Review by odersky.

1 files changed, 28 insertions, 0 deletions

diff --git a/test/files/neg/patmat-type-check.scala b/test/files/neg/patmat-type-check.scala
new file mode 100644
index 0000000000..c6c689b256
--- /dev/null
+++ b/test/files/neg/patmat-type-check.scala
@@ -0,0 +1,28 @@
+object Test
+{
+  def s1 = "bob".toList  match { case Seq('b', 'o', 'b') => true }  // list ok
+
+  // not final, allowed
+  class Bop
+  def s2(x: Bop) = x match { case Seq('b', 'o', 'b') => true }
+
+  // covariance, allowed
+  final class Bop4[+T]
+  def s3[T](x: Bop4[T]) = x match { case Seq('b', 'o', 'b') => true }
+
+  // contravariance, allowed
+  final class Bop5[T, U, -V]
+  def s4[T1, T2](x: Bop5[_, T1, T2]) = x match { case Seq('b', 'o', 'b') => true }
+
+  // String and Array are final/invariant, disallowed
+  def f1 = "bob".reverse match { case Seq('b', 'o', 'b') => true } // fail
+  def f2 = "bob".toArray match { case Seq('b', 'o', 'b') => true } // fail
+
+  // final, no type parameters, should be disallowed
+  final class Bop2
+  def f3(x: Bop2) = x match { case Seq('b', 'o', 'b') => true } // fail
+
+  // final, invariant type parameter, should be disallowed
+  final class Bop3[T]
+  def f4[T](x: Bop3[T]) = x match { case Seq('b', 'o', 'b') => true } // fail
+}