Bringing the tree and icode checkers back to life.

  build/pack/bin/scalac -d /tmp -Ycheck-debug -Ycheck:all \
  src/compiler/scala/tools/nsc/Global.scala

That blows up in constructors as most files do, so also try it with
-Ycheck:icode to see the pretty icode output (for a little while anyway,
after which it will again blow up.)

Our work has only just begun! See test/checker-tests/fail*.scala for
11 examples of places where the checker cries foul. Many of them are
telling us about real issues and we should listen, but I will need help
to figure out which are legitimate and which should be eliminated by
altering the checkers.

This patch also hacks on some territory the checkers drew me into,
especially TypeKinds, where I figured anything which had been commented
out since 2005 was fair game.

(Optional) review by dragos. (The one place I know I could use a look is
in Checkers.scala, because I had to relax some checks and add at least
one newer opcode.)

1 files changed, 136 insertions, 0 deletions

diff --git a/test/checker-tests/fail4.scala b/test/checker-tests/fail4.scala
new file mode 100644
index 0000000000..7bf44617f9
--- /dev/null
+++ b/test/checker-tests/fail4.scala
@@ -0,0 +1,136 @@
+// Incompatible stacks in icode: BoxedUnit vs. empty.
+class Classy {
+  def f(b: Boolean): Unit = synchronized {
+    if (b) ()
+  }
+}
+
+// % work/check all -Xprint:icode work/fail4.scala
+// TypeStack init: REFERENCE(type AnyRef)
+// [Not checkable: parser]
+// [Not checkable: namer]
+// [Not checkable: packageobjects]
+// [Now checking: typer]
+// [Now checking: superaccessors]
+// [Now checking: pickler]
+// [Now checking: refchecks]
+// [Now checking: selectiveanf]
+// [Now checking: liftcode]
+// [Now checking: selectivecps]
+// [Now checking: uncurry]
+// [Now checking: tailcalls]
+// [Not checkable: specialize]
+// [Not checkable: explicitouter]
+// [Now checking: erasure]
+// [Now checking: lazyvals]
+// [Now checking: lambdalift]
+// [Now checking: constructors]
+// [Now checking: flatten]
+// [Now checking: mixin]
+// [Now checking: cleanup]
+// [[syntax trees at end of icode]]// Scala source: fail4.scala
+// package <empty> {
+//   class Classy extends java.lang.Object with ScalaObject {
+//     def f(b: Boolean): Unit = {
+//       Classy.this.synchronized(if (b)
+//         scala.runtime.BoxedUnit.UNIT
+//       else
+//         scala.runtime.BoxedUnit.UNIT);
+//       ()
+//     };
+//     def this(): Classy = {
+//       Classy.super.this();
+//       ()
+//     }
+//   }
+// }
+//
+// [Now checking: icode]
+//
+// ** Checking class Classy
+//
+// ** Checking method Classy.f
+// ** Checking Block 1 [S: 4, 3] [P: N/A]
+//    1-> REFERENCE(class Classy)
+// 0<- REFERENCE(class Classy)
+//    1-> REFERENCE(class Classy)
+//       2-> REFERENCE(class Classy)
+//    1<- REFERENCE(class Classy)
+// 0<- REFERENCE(class Classy)
+// Output changed for Block 1 [S: 4, 3] [P: N/A]
+// ** Checking Block 4 [S: 3, 6, 5] [P: 1]
+//    1-> BOOL
+// 0<- BOOL
+// Output changed for Block 4 [S: 3, 6, 5] [P: 1]
+// ** Checking Block 3 [S: N/A] [P: 1, 4, 5, 6, 7]
+//    1-> REFERENCE(class Throwable)
+//       2-> REFERENCE(class Object)
+//    1<- REFERENCE(class Object)
+// 0<- REFERENCE(class Throwable)
+//    1-> REFERENCE(trait Nothing)
+// ** Checking Block 6 [S: 3, 7] [P: 4]
+//    1-> REFERENCE(class BoxedUnit)
+// Output changed for Block 6 [S: 3, 7] [P: 4]
+// ** Checking Block 5 [S: 3, 7] [P: 4]
+//    1-> REFERENCE(class BoxedUnit)
+// Output changed for Block 5 [S: 3, 7] [P: 4]
+// Checker created new stack: (List(REFERENCE(class BoxedUnit)), List(REFERENCE(class BoxedUnit))) => List(REFERENCE(class BoxedUnit))
+// TypeStack init: REFERENCE(class BoxedUnit)
+// Checker created new stack: (List(REFERENCE(class BoxedUnit)), List(REFERENCE(class BoxedUnit))) => List(REFERENCE(class BoxedUnit))
+// TypeStack init: REFERENCE(class BoxedUnit)
+// Checker created new stack: (List(REFERENCE(class BoxedUnit)), List(REFERENCE(class BoxedUnit))) => List(REFERENCE(class BoxedUnit))
+// TypeStack init: REFERENCE(class BoxedUnit)
+// ** Checking Block 3 [S: N/A] [P: 1, 4, 5, 6, 7] with initial stack [REFERENCE(class BoxedUnit)]
+// TypeStack init: REFERENCE(class BoxedUnit)
+// 0<- REFERENCE(class BoxedUnit)
+//    1-> REFERENCE(class Throwable)
+//       2-> REFERENCE(class Object)
+//    1<- REFERENCE(class Object)
+// 0<- REFERENCE(class Throwable)
+//    1-> REFERENCE(trait Nothing)
+// ** Checking Block 7 [S: 3, 2] [P: 5, 6] with initial stack [REFERENCE(class BoxedUnit)]
+// TypeStack init: REFERENCE(class BoxedUnit)
+// 0<- REFERENCE(class BoxedUnit)
+//    1-> REFERENCE(class Object)
+// 0<- REFERENCE(class Object)
+// Output changed for Block 7 [S: 3, 2] [P: 5, 6]
+// Checker created new stack: (List(REFERENCE(class BoxedUnit)), List(REFERENCE(class BoxedUnit))) => List(REFERENCE(class BoxedUnit))
+// TypeStack init: REFERENCE(class BoxedUnit)
+// Exception in thread "main" scala.tools.nsc.backend.icode.CheckerException: Incompatible stacks: TypeStack(1 elems) {
+//   REFERENCE(class BoxedUnit)
+// } and TypeStack() in Classy.f at entry to block: 3
+//  at scala.tools.nsc.backend.icode.Checkers$ICodeChecker.meet2$1(Checkers.scala:165)
+//  at scala.tools.nsc.backend.icode.Checkers$ICodeChecker$$anonfun$meet$2.apply(Checkers.scala:174)
+//  at scala.tools.nsc.backend.icode.Checkers$ICodeChecker$$anonfun$meet$2.apply(Checkers.scala:174)
+//  at scala.collection.LinearSeqOptimized$class.foldLeft(LinearSeqOptimized.scala:123)
+//  at scala.collection.immutable.List.foldLeft(List.scala:45)
+//  at scala.collection.LinearSeqOptimized$class.reduceLeft(LinearSeqOptimized.scala:137)
+//  at scala.collection.immutable.List.reduceLeft(List.scala:45)
+//  at scala.tools.nsc.backend.icode.Checkers$ICodeChecker.meet(Checkers.scala:174)
+//  at scala.tools.nsc.backend.icode.Checkers$ICodeChecker$$anonfun$check$5.apply(Checkers.scala:140)
+//  at scala.tools.nsc.backend.icode.Checkers$ICodeChecker$$anonfun$check$5.apply(Checkers.scala:140)
+//  at scala.collection.LinearSeqOptimized$class.foreach(LinearSeqOptimized.scala:61)
+//  at scala.collection.immutable.List.foreach(List.scala:45)
+//  at scala.tools.nsc.backend.icode.Checkers$ICodeChecker.check(Checkers.scala:140)
+//  at scala.tools.nsc.backend.icode.Checkers$ICodeChecker.check(Checkers.scala:110)
+//  at scala.tools.nsc.backend.icode.Checkers$ICodeChecker$$anonfun$check$3.apply(Checkers.scala:103)
+//  at scala.tools.nsc.backend.icode.Checkers$ICodeChecker$$anonfun$check$3.apply(Checkers.scala:103)
+//  at scala.collection.LinearSeqOptimized$class.foreach(LinearSeqOptimized.scala:61)
+//  at scala.collection.immutable.List.foreach(List.scala:45)
+//  at scala.tools.nsc.backend.icode.Checkers$ICodeChecker.check(Checkers.scala:103)
+//  at scala.tools.nsc.backend.icode.Checkers$ICodeChecker$$anonfun$checkICodes$1.apply(Checkers.scala:81)
+//  at scala.tools.nsc.backend.icode.Checkers$ICodeChecker$$anonfun$checkICodes$1.apply(Checkers.scala:81)
+//  at scala.collection.mutable.HashMap$$anon$2$$anonfun$foreach$3.apply(HashMap.scala:89)
+//  at scala.collection.mutable.HashMap$$anon$2$$anonfun$foreach$3.apply(HashMap.scala:89)
+//  at scala.collection.Iterator$class.foreach(Iterator.scala:631)
+//  at scala.collection.mutable.HashTable$$anon$1.foreach(HashTable.scala:161)
+//  at scala.collection.mutable.HashTable$class.foreachEntry(HashTable.scala:194)
+//  at scala.collection.mutable.HashMap.foreachEntry(HashMap.scala:39)
+//  at scala.collection.mutable.HashMap$$anon$2.foreach(HashMap.scala:89)
+//  at scala.tools.nsc.backend.icode.Checkers$ICodeChecker.checkICodes(Checkers.scala:81)
+//  at scala.tools.nsc.Global$Run.compileSources(Global.scala:759)
+//  at scala.tools.nsc.Global$Run.compile(Global.scala:823)
+//  at scala.tools.nsc.Main$.process(Main.scala:106)
+//  at scala.tools.nsc.Main$.main(Main.scala:120)
+//  at scala.tools.nsc.Main.main(Main.scala)
+// [paulp@leaf trunk (check-all)]$