Stops barking up the wrong tree with -Ywarn-dea...

Stops barking up the wrong tree with -Ywarn-dead-code. The origin of its
issues was twofold:

 1) synchronized acts by-name without being by-name (ticket #4086) 2)
 warnings are swallowed if context.reportGeneralErrors is false

Those two plus a dash of bitrot. In any case it's at its all time
happiest now. It found all the dead code related fixes in this commit.
Way to go, -Ywarn-dead-code! Review by odersky.

1 files changed, 11 insertions, 5 deletions

diff --git a/test/files/neg/check-dead.check b/test/files/neg/check-dead.check
index be4de3060b..29601c1d4a 100644
--- a/test/files/neg/check-dead.check
+++ b/test/files/neg/check-dead.check
@@ -1,7 +1,13 @@
-check-dead.scala:27: error: dead code following this construct
-    throw new Exception
+check-dead.scala:7: error: dead code following this construct
+  def z1 = y1(throw new Exception)  // should warn
+              ^
+check-dead.scala:10: error: dead code following this construct
+  def z2 = y2(throw new Exception)  // should warn
+              ^
+check-dead.scala:29: error: dead code following this construct
+    throw new Exception // should warn
     ^
-check-dead.scala:31: error: dead code following this construct
-    throw new Exception
+check-dead.scala:33: error: dead code following this construct
+    throw new Exception // should warn
     ^
-two errors found
+four errors found