Merge pull request scala#5376 from milessabin/topic/clean-experimental

Clean up of code guarded by bare -Xexperimental

bincompat-forward.whitelist.conf

@@ -20,6 +20,10 @@ filter {
     {
       matchName="scala.sys.process.ProcessImpl#CompoundProcess.futureThread"
       problemName=DirectMissingMethodProblem
+    },
+    {
+      matchName="scala.reflect.runtime.Settings.Yvirtpatmat"
+      problemName=DirectMissingMethodProblem
     }
   ]
 }

src/compiler/scala/tools/nsc/Global.scala

@@ -333,8 +333,6 @@ class Global(var currentSettings: Settings, var reporter: Reporter)
   // to create it on that side.  For this one my strategy is a constant def at the file
   // where I need it, and then an override in Global with the setting.
   override protected val etaExpandKeepsStar = settings.etaExpandKeepsStar.value
-  // Here comes another one...
-  override protected val enableTypeVarExperimentals = settings.Xexperimental.value
 
   def getSourceFile(f: AbstractFile): BatchSourceFile = new BatchSourceFile(f, reader read f)
 

src/compiler/scala/tools/nsc/settings/ScalaSettings.scala

@@ -215,6 +215,7 @@ trait ScalaSettings extends AbsScalaSettings
   val inferByName     = BooleanSetting    ("-Yinfer-by-name", "Allow inference of by-name types. This is a temporary option to ease transition. See SI-7899.").withDeprecationMessage(removalIn212)
   val YdisableFlatCpCaching  = BooleanSetting    ("-YdisableFlatCpCaching", "Do not cache flat classpath representation of classpath elements from jars across compiler instances.")
   val YpartialUnification = BooleanSetting ("-Ypartial-unification", "Enable partial unification in type constructor inference")
+  val Yvirtpatmat     = BooleanSetting    ("-Yvirtpatmat", "Enable pattern matcher virtualization")
 
   val exposeEmptyPackage = BooleanSetting ("-Yexpose-empty-package", "Internal only: expose the empty package.").internalOnly()
   val Ydelambdafy        = ChoiceSetting  ("-Ydelambdafy", "strategy", "Strategy used for translating lambdas into JVM code.", List("inline", "method"), "method")

src/compiler/scala/tools/nsc/typechecker/Typers.scala

@@ -2561,7 +2561,7 @@ trait Typers extends Adaptations with Tags with TypersTracking with PatternTyper
 
       // TODO: add fallback __match sentinel to predef
       val matchStrategy: Tree =
-        if (!(settings.Xexperimental && context.isNameInScope(vpmName._match))) null    // fast path, avoiding the next line if there's no __match to be seen
+        if (!(settings.Yvirtpatmat && context.isNameInScope(vpmName._match))) null    // fast path, avoiding the next line if there's no __match to be seen
         else newTyper(context.makeImplicit(reportAmbiguousErrors = false)).silent(_.typed(Ident(vpmName._match)), reportAmbiguousErrors = false) orElse (_ => null)
 
       if (matchStrategy ne null) // virtualize

src/reflect/scala/reflect/internal/Types.scala

@@ -99,8 +99,6 @@ trait Types
   private final val propagateParameterBoundsToTypeVars = sys.props contains "scalac.debug.prop-constraints"
   private final val sharperSkolems = sys.props contains "scalac.experimental.sharper-skolems"
 
-  protected val enableTypeVarExperimentals = settings.Xexperimental.value
-
   /** Caching the most recent map has a 75-90% hit rate. */
   private object substTypeMapCache {
     private[this] var cached: SubstTypeMap = new SubstTypeMap(Nil, Nil)
@@ -3010,7 +3008,7 @@ trait Types
     // EXPERIMENTAL: value will not be considered unless enableTypeVarExperimentals is true
     // see SI-5729 for why this is still experimental
     private var encounteredHigherLevel = false
-    private def shouldRepackType = enableTypeVarExperimentals && encounteredHigherLevel
+    private def shouldRepackType = encounteredHigherLevel
 
     // <region name="constraint mutators + undoLog">
     // invariant: before mutating constr, save old state in undoLog
@@ -3205,7 +3203,8 @@ trait Types
         checkSubtype(tp, origin)
       else if (instValid)  // type var is already set
         checkSubtype(tp, inst)
-      else isRelatable(tp) && {
+      else {
+        trackHigherLevel(tp)
         unifySimple || unifyFull(tp) || (
           // only look harder if our gaze is oriented toward Any
           isLowerBound && (
@@ -3228,7 +3227,8 @@ trait Types
 
       if (suspended) tp =:= origin
       else if (instValid) checkIsSameType(tp)
-      else isRelatable(tp) && {
+      else {
+        trackHigherLevel(tp)
         val newInst = wildcardToTypeVarMap(tp)
         (constr isWithinBounds newInst) && {
           setInst(newInst)
@@ -3251,19 +3251,10 @@ trait Types
       case ts: TypeSkolem => ts.level > level
       case _              => false
     }
-    // side-effects encounteredHigherLevel
-    private def containsSkolemAboveLevel(tp: Type) =
-      (tp exists isSkolemAboveLevel) && { encounteredHigherLevel = true ; true }
 
-     /** Can this variable be related in a constraint to type `tp`?
-      *  This is not the case if `tp` contains type skolems whose
-      *  skolemization level is higher than the level of this variable.
-      */
-    def isRelatable(tp: Type) = (
-         shouldRepackType               // short circuit if we already know we've seen higher levels
-      || !containsSkolemAboveLevel(tp)  // side-effects tracking boolean
-      || enableTypeVarExperimentals     // -Xexperimental: always say we're relatable, track consequences
-    )
+    private def trackHigherLevel(tp: Type): Unit =
+      if(!shouldRepackType && tp.exists(isSkolemAboveLevel))
+        encounteredHigherLevel = true
 
     override def normalize: Type = (
       if (instValid) inst

src/reflect/scala/reflect/internal/settings/MutableSettings.scala

@@ -54,6 +54,7 @@ abstract class MutableSettings extends AbsSettings {
   def uniqid: BooleanSetting
   def verbose: BooleanSetting
   def YpartialUnification: BooleanSetting
+  def Yvirtpatmat: BooleanSetting
 
   def Yrecursion: IntSetting
   def maxClassfileName: IntSetting

src/reflect/scala/reflect/runtime/Settings.scala

@@ -48,6 +48,7 @@ private[reflect] class Settings extends MutableSettings {
   val uniqid            = new BooleanSetting(false)
   val verbose           = new BooleanSetting(false)
   val YpartialUnification = new BooleanSetting(false)
+  val Yvirtpatmat       = new BooleanSetting(false)
 
   val Yrecursion        = new IntSetting(0)
   val maxClassfileName  = new IntSetting(255)

test/files/neg/t5729.check

@@ -0,0 +1,7 @@
+t5729.scala:5: error: ambiguous reference to overloaded definition,
+both method join in object Test of type [S](in: Seq[T[S]])String
+and  method join in object Test of type (in: Seq[T[_]])Int
+match argument types (Seq[T[_]])
+  join(null: Seq[T[_]])
+  ^
+one error found

test/files/run/virtpatmat_staging.flags

@@ -1,2 +1,2 @@
 -Yrangepos:false
--Xexperimental
+-Yvirtpatmat