TailRec phase and tests for it.

Ported tailcall phase from scalac with such changes:
  - all transformation is done in the phase itself
     (previously half of the work was done in backend)
  - it is now able to run before uncurry
  - it is now a treeTransform
  - renamed to tailrec to make it more obvious that
     this phase transforms only recursive calls.

For now this is a single phase which speculatively
transforms DefDefs.
Speculation can be potentially removed by
splitting into 2 phases:
  one detecting which methods should be transformed
  second performing transformation.

But, as transformation requires as same amount of work
as detection, I believe it will be simpler to maintain
it as a single phase.

Conflicts:
	tests/pos/typers.scala

1 files changed, 0 insertions, 56 deletions

diff --git a/tests/untried/pos/t6479.scala b/tests/untried/pos/t6479.scala
deleted file mode 100644
index e4a4ff601..000000000
--- a/tests/untried/pos/t6479.scala
+++ /dev/null
@@ -1,56 +0,0 @@
-object TailrecAfterTryCatch {
-
-  @annotation.tailrec
-  final def good1(): Unit = {
-    1 match {
-      case 2 => {
-        try {
-        //  return
-        } catch {
-          case e: ClassNotFoundException =>
-        }
-        good1()
-      }
-    }
-  }
-
-  @annotation.tailrec
-  final def good2(): Unit = {
-    //1 match {
-    //  case 2 => {
-        try {
-          return
-        } catch {
-          case e: ClassNotFoundException =>
-        }
-        good2()
-    //  }
-    //}
-  }
-
-  @annotation.tailrec
-  final def good3(): Unit = {
-    val 1 = 2
-    try {
-      return
-    } catch {
-      case e: ClassNotFoundException =>
-    }
-    good3()
-  }
-
-  @annotation.tailrec
-  final def bad(): Unit = {
-    1 match {
-      case 2 => {
-        try {
-          return
-        } catch {
-          case e: ClassNotFoundException =>
-        }
-        bad()
-      }
-    }
-  }
-
-}