The birth of the @switch and @tailrec annotations.

They are located in package scala.annotation. Also in this patch:

 * numerous test cases for both annotations
 * addition of @tailrec and @switch in a few strategic locations
 * fixes for critical section NewScanners methods which were not being
   compiled into switches, immediately proving the value of @switch
 * tail recursive implementations for Iterator.{ dropWhile, drop}
   and List.dropWhile tagged with @tailrec, closing bug #1376

4 files changed, 139 insertions, 0 deletions

diff --git a/test/files/neg/switch.check b/test/files/neg/switch.check
new file mode 100644
index 0000000000..7212c1a22b
--- /dev/null
+++ b/test/files/neg/switch.check
@@ -0,0 +1,10 @@
+switch.scala:28: error: could not emit switch for @switch annotated match
+  def fail1(c: Char) = (c: @switch) match {
+                                    ^
+switch.scala:38: error: could not emit switch for @switch annotated match
+  def fail2(c: Char) = (c: @switch @unchecked) match {
+                                               ^
+switch.scala:45: error: could not emit switch for @switch annotated match
+  def fail3(c: Char) = (c: @unchecked @switch) match {
+                                               ^
+three errors found
diff --git a/test/files/neg/switch.scala b/test/files/neg/switch.scala
new file mode 100644
index 0000000000..a5a6f9e789
--- /dev/null
+++ b/test/files/neg/switch.scala
@@ -0,0 +1,66 @@
+import scala.annotation.switch
+
+// this is testing not so much how things ought to be but how they are;
+// the test is supposed to start failing if the behavior changes at all.
+object Other {
+  val C1 = 'P'                // fails: not final
+  final val C2 = 'Q'          // succeeds: singleton type Char('Q') inferred
+  final val C3: Char = 'R'    // fails: type Char specified
+  final val C4 = '\u000A'     // succeeds like C2 but more unicodey
+}
+
+object Main {
+  def succ1(c: Char) = (c: @switch) match {
+    case 'A' | 'B' | 'C'  => true
+    case 'd'              => true
+    case 'f' | 'g'        => true
+    case _                => false
+  }
+
+  def succ2(c: Char) = (c: @switch) match {
+    case 'A' | 'B' | 'C'  => true
+    case Other.C2         => true
+    case Other.C4         => true
+    case _                => false
+  }
+
+  // has a guard
+  def fail1(c: Char) = (c: @switch) match {
+    case 'A' | 'B' | 'C'  => true
+    case x if x == 'A'    => true
+    case _                => false
+  }
+
+  // throwing in @unchecked on the next two to make sure
+  // multiple annotations are processed correctly
+
+  // thinks a val in an object is constant... so naive
+  def fail2(c: Char) = (c: @switch @unchecked) match {
+    case 'A'        => true
+    case Other.C1   => true
+    case _          => false
+  }
+
+  // more naivete
+  def fail3(c: Char) = (c: @unchecked @switch) match {
+    case 'A'        => true
+    case Other.C3   => true
+    case _          => false
+  }
+
+  // guard case done correctly
+  def succ3(c: Char) = (c: @switch) match {
+    case 'A' | 'B' | 'C'  => true
+    case x                => x == 'A'
+  }
+
+  // some ints just to mix it up a bit
+  def succ4(x: Int, y: Int) = ((x+y): @switch) match {
+    case  1 => 5
+    case  2 => 10
+    case  3 => 20
+    case  4 => 50
+    case 5|6|7|8 => 100
+    case _  => -1
+  }
+}
\ No newline at end of file
diff --git a/test/files/neg/tailrec.check b/test/files/neg/tailrec.check
new file mode 100644
index 0000000000..22d70e82a0
--- /dev/null
+++ b/test/files/neg/tailrec.check
@@ -0,0 +1,10 @@
+tailrec.scala:6: error: could not optimize @tailrec annotated method
+  def facfail(n: Int): Int =
+      ^
+tailrec.scala:42: error: could not optimize @tailrec annotated method
+  @tailrec def fail1(x: Int): Int = fail1(x)
+               ^
+tailrec.scala:45: error: could not optimize @tailrec annotated method
+  @tailrec def fail2[T](xs: List[T]): List[T] = xs match {
+               ^
+three errors found
diff --git a/test/files/neg/tailrec.scala b/test/files/neg/tailrec.scala
new file mode 100644
index 0000000000..4c45672f93
--- /dev/null
+++ b/test/files/neg/tailrec.scala
@@ -0,0 +1,53 @@
+import scala.annotation.tailrec
+
+// putting @tailrec through the paces
+object Main {
+  @tailrec
+  def facfail(n: Int): Int =
+    if (n == 0) 1
+    else n * facfail(n - 1)
+
+  @tailrec
+  def facsucc(n: Int, acc: Int): Int =
+    if (n == 0) acc
+    else facsucc(n - 1, n * acc)
+
+  @tailrec def loopy1(x: Int): Int = loopy1(x - 1)
+
+  def ding {
+    object dong {
+      @tailrec def loopy2(x: Int): Int = loopy2(x)
+    }
+    ()
+  }
+
+  def inner(q: Int) = {
+    @tailrec
+    def loopy3(x: Int): Int = loopy3(x + 1)
+
+    loopy3(q)
+  }
+}
+
+class Bob {
+  // these should work
+  @tailrec private def succ1(x: Int): Int = succ1(x)
+  @tailrec final def succ2(x: Int): Int = succ2(x)
+  @tailrec final def succ3[T](in: List[T], acc: List[T]): List[T] = in match {
+    case Nil      => Nil
+    case x :: xs  => succ3(xs, x :: acc)
+  }
+
+  // not private, not final
+  @tailrec def fail1(x: Int): Int = fail1(x)
+
+  // a typical between-chair-and-keyboard error
+  @tailrec def fail2[T](xs: List[T]): List[T] = xs match {
+    case Nil      => Nil
+    case x :: xs  => x :: fail2(xs)
+  }
+
+  object innerBob {
+    @tailrec def succ4(x: Int): Int = succ4(x)
+  }
+}