virtpatmat: initial CPS support

typers&patmatvirtualizer have ad-hoc support for dropping annotations
in a way that makes the CPS plugins happy... this is not ideal,
but unless virtpatmat runs after the plugin phases, I don't see how to solve it
running virtpatmat after the CPS plugin would mean the pattern matching evaluation
cannot be captured by CPS, so it's not even desirable to move it to a later phase

- typedIf must lub annotated types
- drop selector.tpe's annotations
- drop annots in matchEnd's argument type
- deal with annots in casts synth by in virtpatmat
  (drop them from type arg to asInstanceof, recover them using type ascription)
- workaround skolemize existential dropping annots

CPS is the main reason why typedMatchAnonFun is not used anymore,
and PartialFunction synthesis is moved back to uncurry (which is quite painful due to labeldefs being so broken)
we can't synth partialfunction during typer since T @cps[U] does not conform to Any,
so we can't pass it as a type arg to PartialFunction, so we can't type a cps-transformed PF
after the CPS plugin, T @cps[U] becomes ControlContext[...], which is a type we can pass
to PartialFunction

virtpatmat is now also run until right before uncurry
(so, can't use isPastTyper, although it means more or less the same thing -- we don't run after uncurry)

the main functional improvements are in the selective ANF transform
its treatment of labeldefs was broken: for example,
LabelDef L1; LabelDef L2 --> DefDef L1; L1(); DefDef L2; L2()
but this does not take into account L1 may jump over L2 to another label
since methods always return (or fail), and the ANF transform generates ValDefs
to store the result of those method calls, both L1 and L2 would always be executed
(so you would run a match with N cases N times, with each partial run starting at a later case)

also fixed a couple of weird bugs in selective anf that caused matches to be duplicated
(with the duplicate being nested in the original)

since label defs are turned into method defs, and later defs
will be nested in the flatMap calls on the controlcontext
yielded by earlier statements, we reverse the list of method
definitions, so that earlier (in the control flow sense) methods
are visible in later ones

selective CPS now generates a catch that's directly digestible by backend

1 files changed, 1 insertions, 1 deletions

diff --git a/test/files/continuations-run/match2.scala b/test/files/continuations-run/match2.scala
index 8b0fb946df..5092ce3abe 100644
--- a/test/files/continuations-run/match2.scala
+++ b/test/files/continuations-run/match2.scala
@@ -18,7 +18,7 @@ object Test {
   }
 
   
-  def main(args: Array[String]): Any = {
+  def main(args: Array[String]): Unit = {
     println(reset(test1()))
     println(reset(test2()))
   }