Added -Xmigration option and @migration annotat...

Added -Xmigration option and @migration annotation. At present it will
warn about the following changes from 2.7 to 2.8:

  Stack iterator order reversed
  mutable.Set.map returns a Set and thus discards duplicates
  A case 'x @ Pattern' matches differently than 'Pattern'

Review by odersky.

3 files changed, 21 insertions, 0 deletions

diff --git a/test/files/neg/migration28.check b/test/files/neg/migration28.check
new file mode 100644
index 0000000000..19aba2c31d
--- /dev/null
+++ b/test/files/neg/migration28.check
@@ -0,0 +1,8 @@
+migration28.scala:5: error: method ++= in class Stack is deprecated: use pushAll
+  s ++= List(1,2,3)
+  ^
+migration28.scala:7: error: method foreach in class Stack has changed semantics:
+ Stack iterator and foreach now traverse in FIFO order.
+  s foreach (_ => ())
+  ^
+two errors found
diff --git a/test/files/neg/migration28.flags b/test/files/neg/migration28.flags
new file mode 100644
index 0000000000..f7025d0226
--- /dev/null
+++ b/test/files/neg/migration28.flags
@@ -0,0 +1 @@
+-Yfatal-warnings -Xmigration
diff --git a/test/files/neg/migration28.scala b/test/files/neg/migration28.scala
new file mode 100644
index 0000000000..090b32d690
--- /dev/null
+++ b/test/files/neg/migration28.scala
@@ -0,0 +1,12 @@
+object Test {
+  import scala.collection.mutable._
+
+  val s = new Stack[Int]
+  s ++= List(1,2,3)
+  s map (_ + 1)
+  s foreach (_ => ())
+
+  def main(args: Array[String]): Unit = {
+
+  }
+}