virtpatmat, hidden behind -Yvirtpatmat

at least one imminent TODO: undo hardwired generation of if/then/else,
and decide based on type whether to call flatMap/orElse or inline those
methods from Option

review by extempore

1 files changed, 17 insertions, 5 deletions

diff --git a/src/compiler/scala/tools/nsc/typechecker/Typers.scala b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
index c2dd1ba6a2..13cd299fa2 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Typers.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
@@ -27,7 +27,7 @@ import scala.tools.util.StringOps.{ countAsString, countElementsAsString }
  *  @author  Martin Odersky
  *  @version 1.0
  */
-trait Typers extends Modes with Adaptations {
+trait Typers extends Modes with Adaptations with PatMatVirtualiser {
   self: Analyzer =>
 
   import global._
@@ -3280,11 +3280,23 @@ trait Typers extends Modes with Adaptations {
         } else {
           val selector1 = checkDead(typed(selector, EXPRmode | BYVALmode, WildcardType))
           var cases1 = typedCases(tree, cases, selector1.tpe.widen, pt)
-          val (owntype, needAdapt) = ptOrLub(cases1 map (_.tpe))
-          if (needAdapt) {
-            cases1 = cases1 map (adaptCase(_, owntype))
+
+          if (phase.id > currentRun.typerPhase.id || !opt.virtPatmat) {
+            val (owntype, needAdapt) = ptOrLub(cases1 map (_.tpe))
+            if (needAdapt) {
+              cases1 = cases1 map (adaptCase(_, owntype))
+            }
+            treeCopy.Match(tree, selector1, cases1) setType owntype
+          } else { // don't run translator after typers (see comments in PatMatVirtualiser)
+            def repackExistential(tp: Type): Type = existentialAbstraction((tp filter {t => t.typeSymbol.isExistentiallyBound}) map (_.typeSymbol), tp)
+            val (owntype0, needAdapt) = ptOrLub(cases1 map (x => repackExistential(x.tpe)))
+            val owntype = elimAnonymousClass(owntype0)
+            if (needAdapt) cases1 = cases1 map (adaptCase(_, owntype))
+
+            val translated = (new MatchTranslator(this)).X(treeCopy.Match(tree, selector1, cases1), owntype)
+
+            typed1(translated, mode, WildcardType) setType owntype // TODO: get rid of setType owntype -- it should all typecheck
           }
-          treeCopy.Match(tree, selector1, cases1) setType owntype
         }
       }