Merge remote-tracking branch 'origin/2.10.x' into merge-210

* origin/2.10.x:
  Fix for paramaccessor alias regression.
  Expanded bytecode testing code.
  SI-5675 Discard duplicate feature warnings at a position
  accommodates pull request feedback
  term and type reftrees are now reified uniformly
  SI-6591 Reify and path-dependent types
  SI-7096 SubstSymMap copies trees before modifying their symbols
  SI-6961 no structural sharing in list serialization
  SI-6187 Make partial functions re-typable
  [backport] SI-6478 Fixing JavaTokenParser ident
  SI-7100 Fixed infinite recursion in duplicators
  SI-6146 More accurate prefixes for sealed subtypes.
  SI-5082 Cycle avoidance between case companions
  SI-6113 typeOf now works for type lambdas
  SI-5824 Fix crashes in reify with _*
  SI-7026: parseTree should never return a typed one
  SI-7070 Turn restriction on companions in pkg objs into warning

Conflicts:
	src/compiler/scala/reflect/reify/codegen/GenSymbols.scala
	src/compiler/scala/tools/nsc/typechecker/PatternMatching.scala
	src/compiler/scala/tools/nsc/typechecker/Typers.scala
	src/compiler/scala/tools/reflect/ToolBoxFactory.scala
	src/library/scala/collection/immutable/List.scala
	src/reflect/scala/reflect/internal/TreeInfo.scala
	src/reflect/scala/reflect/internal/Types.scala
	src/reflect/scala/reflect/internal/settings/MutableSettings.scala
	src/reflect/scala/reflect/runtime/Settings.scala
	test/files/buildmanager/t2650_1/t2650_1.check
	test/files/buildmanager/t2657/t2657.check
	test/files/neg/t3234.check
	test/files/run/idempotency-this.check
	test/files/run/macro-typecheck-macrosdisabled2.check
	test/files/run/showraw_tree.check
	test/files/run/showraw_tree_ids.check
	test/files/run/showraw_tree_kinds.check
	test/files/run/showraw_tree_types_ids.check
	test/files/run/showraw_tree_types_typed.check
	test/files/run/showraw_tree_types_untyped.check
	test/files/run/showraw_tree_ultimate.check
	test/files/run/t2886.check
	test/files/run/t5225_2.check
	test/files/run/t5374.check
	test/files/run/t5374.scala
	test/files/run/t6329_repl.check
	test/files/run/toolbox_typecheck_macrosdisabled2.check

27 files changed, 443 insertions, 137 deletions

diff --git a/src/compiler/scala/reflect/reify/codegen/GenSymbols.scala b/src/compiler/scala/reflect/reify/codegen/GenSymbols.scala
index 731aab93b8..67bc93d407 100644
--- a/src/compiler/scala/reflect/reify/codegen/GenSymbols.scala
+++ b/src/compiler/scala/reflect/reify/codegen/GenSymbols.scala
@@ -1,6 +1,8 @@
 package scala.reflect.reify
 package codegen
 
+import scala.reflect.internal.Flags._
+
 trait GenSymbols {
   self: Reifier =>
 
@@ -99,6 +101,33 @@ trait GenSymbols {
     reifyIntoSymtab(binding.symbol) { sym =>
       if (reifyDebug) println("Free term" + (if (sym.isCapturedVariable) " (captured)" else "") + ": " + sym + "(" + sym.accurateKindString + ")")
       val name = newTermName("" + nme.REIFY_FREE_PREFIX + sym.name + (if (sym.isType) nme.REIFY_FREE_THIS_SUFFIX else ""))
+      // We need to note whether the free value being reified is stable or not to guide subsequent reflective compilation.
+      // Here's why reflection compilation needs our help.
+      //
+      // When dealing with a tree, which contain free values, toolboxes extract those and wrap the entire tree in a Function
+      // having parameters defined for every free values in the tree. For example, evaluating
+      //
+      //   Ident(setTypeSignature(newFreeTerm("x", 2), <Int>))
+      //
+      // Will generate something like
+      //
+      //   object wrapper {
+      //     def wrapper(x: () => Int) = {
+      //       x()
+      //     }
+      //   }
+      //
+      // Note that free values get transformed into, effectively, by-name parameters. This is done to make sure
+      // that evaluation order is kept intact. And indeed, we cannot just evaluate all free values at once in order
+      // to obtain arguments for wrapper.wrapper, because if some of the free values end up being unused during evaluation,
+      // we might end up doing unnecessary calculations.
+      //
+      // So far, so good - we didn't need any flags at all. However, if the code being reified contains path-dependent types,
+      // we're in trouble, because valid code like `free.T` ends up being transformed into `free.apply().T`, which won't compile.
+      //
+      // To overcome this glitch, we note whether a given free term is stable or not (because vars can also end up being free terms).
+      // Then, if a free term is stable, we tell the compiler to treat `free.apply()` specially and assume that it's stable.
+      if (!sym.isMutable) sym setFlag STABLE
       if (sym.isCapturedVariable) {
         assert(binding.isInstanceOf[Ident], showRaw(binding))
         val capturedBinding = referenceCapturedVariable(sym)
diff --git a/src/compiler/scala/reflect/reify/codegen/GenTrees.scala b/src/compiler/scala/reflect/reify/codegen/GenTrees.scala
index f60089c935..df2eeaa932 100644
--- a/src/compiler/scala/reflect/reify/codegen/GenTrees.scala
+++ b/src/compiler/scala/reflect/reify/codegen/GenTrees.scala
@@ -155,21 +155,23 @@ trait GenTrees {
         else mirrorCall(nme.Ident, reify(name))
 
       case Select(qual, name) =>
-        if (sym == NoSymbol || sym.name == name)
-          reifyProduct(tree)
-        else
-          reifyProduct(Select(qual, sym.name))
+        if (qual.symbol != null && qual.symbol.isPackage) {
+          mirrorBuildCall(nme.Ident, reify(sym))
+        } else {
+          val effectiveName = if (sym != null && sym != NoSymbol) sym.name else name
+          reifyProduct(Select(qual, effectiveName))
+        }
 
       case _ =>
         throw new Error("internal error: %s (%s, %s) is not supported".format(tree, tree.productPrefix, tree.getClass))
     }
   }
 
-  private def reifyBoundType(tree: Tree): Tree = {
+  private def reifyBoundType(tree: RefTree): Tree = {
     val sym = tree.symbol
     val tpe = tree.tpe
 
-    def reifyBoundType(tree: Tree): Tree = {
+    def reifyBoundType(tree: RefTree): Tree = {
       assert(tpe != null, "unexpected: bound type that doesn't have a tpe: " + showRaw(tree))
 
       // if a symbol or a type of the scrutinee are local to reifee
@@ -177,7 +179,7 @@ trait GenTrees {
       // then we can reify the scrutinee as a symless AST and that will definitely be hygienic
       // why? because then typechecking of a scrutinee doesn't depend on the environment external to the quasiquote
       // otherwise we need to reify the corresponding type
-      if (sym.isLocalToReifee || tpe.isLocalToReifee)
+      if (sym.isLocalToReifee || tpe.isLocalToReifee || treeInfo.isWildcardStarType(tree))
         reifyProduct(tree)
       else {
         if (reifyDebug) println("reifying bound type %s (underlying type is %s)".format(sym, tpe))
@@ -198,13 +200,19 @@ trait GenTrees {
               mirrorBuildCall(nme.TypeTree, spliced)
           }
         }
-        else if (sym.isLocatable) {
-          if (reifyDebug) println("tpe is locatable: reify as Ident(%s)".format(sym))
-          mirrorBuildCall(nme.Ident, reify(sym))
-        }
-        else {
-          if (reifyDebug) println("tpe is not locatable: reify as TypeTree(%s)".format(tpe))
-          mirrorBuildCall(nme.TypeTree, reify(tpe))
+        else tree match {
+          case Select(qual, name) if !qual.symbol.isPackage =>
+            if (reifyDebug) println(s"reifying Select($qual, $name)")
+            mirrorCall(nme.Select, reify(qual), reify(name))
+          case SelectFromTypeTree(qual, name) =>
+            if (reifyDebug) println(s"reifying SelectFromTypeTree($qual, $name)")
+            mirrorCall(nme.SelectFromTypeTree, reify(qual), reify(name))
+          case _ if sym.isLocatable =>
+            if (reifyDebug) println(s"tpe is locatable: reify as Ident($sym)")
+            mirrorBuildCall(nme.Ident, reify(sym))
+          case _ =>
+            if (reifyDebug) println(s"tpe is not locatable: reify as TypeTree($tpe)")
+            mirrorBuildCall(nme.TypeTree, reify(tpe))
         }
       }
     }
diff --git a/src/compiler/scala/reflect/reify/codegen/GenTypes.scala b/src/compiler/scala/reflect/reify/codegen/GenTypes.scala
index ca44938f50..2370f18e3a 100644
--- a/src/compiler/scala/reflect/reify/codegen/GenTypes.scala
+++ b/src/compiler/scala/reflect/reify/codegen/GenTypes.scala
@@ -69,8 +69,7 @@ trait GenTypes {
   def reificationIsConcrete: Boolean = state.reificationIsConcrete
 
   def spliceType(tpe: Type): Tree = {
-    val quantified = currentQuantified
-    if (tpe.isSpliceable && !(quantified contains tpe.typeSymbol)) {
+    if (tpe.isSpliceable && !(boundSymbolsInCallstack contains tpe.typeSymbol)) {
       if (reifyDebug) println("splicing " + tpe)
 
       val tagFlavor = if (concrete) tpnme.TypeTag.toString else tpnme.WeakTypeTag.toString
diff --git a/src/compiler/scala/reflect/reify/phases/Reify.scala b/src/compiler/scala/reflect/reify/phases/Reify.scala
index 2741785752..eda4cba2bf 100644
--- a/src/compiler/scala/reflect/reify/phases/Reify.scala
+++ b/src/compiler/scala/reflect/reify/phases/Reify.scala
@@ -26,7 +26,10 @@ trait Reify extends GenSymbols
       finally currents = currents.tail
     }
   }
-  def currentQuantified = flatCollect(reifyStack.currents)({ case ExistentialType(quantified, _) => quantified })
+  def boundSymbolsInCallstack = flatCollect(reifyStack.currents) {
+    case ExistentialType(quantified, _) => quantified
+    case PolyType(typeParams, _) => typeParams
+  }
   def current = reifyStack.currents.head
   def currents = reifyStack.currents
 
diff --git a/src/compiler/scala/reflect/reify/phases/Reshape.scala b/src/compiler/scala/reflect/reify/phases/Reshape.scala
index 5dd5f08b45..71fe4ddeea 100644
--- a/src/compiler/scala/reflect/reify/phases/Reshape.scala
+++ b/src/compiler/scala/reflect/reify/phases/Reshape.scala
@@ -187,8 +187,12 @@ trait Reshape {
     }
 
     private def toPreTyperTypedOrAnnotated(tree: Tree): Tree = tree match {
-      case ty @ Typed(expr1, tt @ TypeTree()) =>
+      case ty @ Typed(expr1, tpt) =>
         if (reifyDebug) println("reify typed: " + tree)
+        val original = tpt match {
+          case tt @ TypeTree() => tt.original
+          case tpt => tpt
+        }
         val annotatedArg = {
           def loop(tree: Tree): Tree = tree match {
             case annotated1 @ Annotated(ann, annotated2 @ Annotated(_, _)) => loop(annotated2)
@@ -196,15 +200,15 @@ trait Reshape {
             case _ => EmptyTree
           }
 
-          loop(tt.original)
+          loop(original)
         }
         if (annotatedArg != EmptyTree) {
           if (annotatedArg.isType) {
             if (reifyDebug) println("verdict: was an annotated type, reify as usual")
             ty
           } else {
-            if (reifyDebug) println("verdict: was an annotated value, equivalent is " + tt.original)
-            toPreTyperTypedOrAnnotated(tt.original)
+            if (reifyDebug) println("verdict: was an annotated value, equivalent is " + original)
+            toPreTyperTypedOrAnnotated(original)
           }
         } else {
           if (reifyDebug) println("verdict: wasn't annotated, reify as usual")
diff --git a/src/compiler/scala/reflect/reify/utils/Extractors.scala b/src/compiler/scala/reflect/reify/utils/Extractors.scala
index 254cb02ee6..d57188bf6e 100644
--- a/src/compiler/scala/reflect/reify/utils/Extractors.scala
+++ b/src/compiler/scala/reflect/reify/utils/Extractors.scala
@@ -263,12 +263,12 @@ trait Extractors {
   }
 
   object BoundType {
-    def unapply(tree: Tree): Option[Tree] = tree match {
-      case Select(_, name) if name.isTypeName =>
+    def unapply(tree: Tree): Option[RefTree] = tree match {
+      case tree @ Select(_, name) if name.isTypeName =>
         Some(tree)
-      case SelectFromTypeTree(_, name) if name.isTypeName =>
+      case tree @ SelectFromTypeTree(_, _) =>
         Some(tree)
-      case Ident(name) if name.isTypeName =>
+      case tree @ Ident(name) if name.isTypeName =>
         Some(tree)
       case _ =>
         None
diff --git a/src/compiler/scala/tools/nsc/Global.scala b/src/compiler/scala/tools/nsc/Global.scala
index d751669612..466f5eb17c 100644
--- a/src/compiler/scala/tools/nsc/Global.scala
+++ b/src/compiler/scala/tools/nsc/Global.scala
@@ -1107,13 +1107,13 @@ class Global(var currentSettings: Settings, var reporter: Reporter)
 
   /** Collects for certain classes of warnings during this run. */
   class ConditionalWarning(what: String, option: Settings#BooleanSetting) {
-    val warnings = new mutable.ListBuffer[(Position, String)]
+    val warnings = mutable.LinkedHashMap[Position, String]()
     def warn(pos: Position, msg: String) =
       if (option.value) reporter.warning(pos, msg)
-      else warnings += ((pos, msg))
+      else if (!(warnings contains pos)) warnings += ((pos, msg))
     def summarize() =
-      if (option.isDefault && warnings.nonEmpty)
-        reporter.warning(NoPosition, "there were %d %s warnings; re-run with %s for details".format(warnings.size, what, option.name))
+      if (warnings.nonEmpty && (option.isDefault || settings.fatalWarnings.value))
+        warning("there were %d %s warning(s); re-run with %s for details".format(warnings.size, what, option.name))
   }
 
   def newUnitParser(code: String)      = new syntaxAnalyzer.UnitParser(newCompilationUnit(code))
diff --git a/src/compiler/scala/tools/nsc/doc/ScaladocGlobal.scala b/src/compiler/scala/tools/nsc/doc/ScaladocGlobal.scala
index 5e68152936..d4777d7800 100644
--- a/src/compiler/scala/tools/nsc/doc/ScaladocGlobal.scala
+++ b/src/compiler/scala/tools/nsc/doc/ScaladocGlobal.scala
@@ -12,7 +12,7 @@ import typechecker.Analyzer
 import scala.reflect.internal.util.BatchSourceFile
 
 trait ScaladocAnalyzer extends Analyzer {
-  val global : ScaladocGlobal
+  val global : Global // generally, a ScaladocGlobal
   import global._
 
   override def newTyper(context: Context): ScaladocTyper = new ScaladocTyper(context)
diff --git a/src/compiler/scala/tools/nsc/interactive/CompilerControl.scala b/src/compiler/scala/tools/nsc/interactive/CompilerControl.scala
index cf38c629fc..f10c00b8e0 100644
--- a/src/compiler/scala/tools/nsc/interactive/CompilerControl.scala
+++ b/src/compiler/scala/tools/nsc/interactive/CompilerControl.scala
@@ -256,15 +256,12 @@ trait CompilerControl { self: Global =>
   }
 
   /** Returns parse tree for source `source`. No symbols are entered. Syntax errors are reported.
-   *  Can be called asynchronously from presentation compiler.
+   *
+   *  This method is thread-safe and as such can safely run outside of the presentation
+   *  compiler thread.
    */
-  def parseTree(source: SourceFile): Tree = ask { () =>
-    getUnit(source) match {
-      case Some(unit) if unit.status >= JustParsed =>
-        unit.body
-      case _ =>
-        new UnitParser(new CompilationUnit(source)).parse()
-    }
+  def parseTree(source: SourceFile): Tree = {
+    new UnitParser(new CompilationUnit(source)).parse()
   }
 
   /** Asks for a computation to be done quickly on the presentation compiler thread */
diff --git a/src/compiler/scala/tools/nsc/interactive/Global.scala b/src/compiler/scala/tools/nsc/interactive/Global.scala
index 31208d2ad7..9bb2d552be 100644
--- a/src/compiler/scala/tools/nsc/interactive/Global.scala
+++ b/src/compiler/scala/tools/nsc/interactive/Global.scala
@@ -221,7 +221,10 @@ class Global(settings: Settings, _reporter: Reporter, projectName: String = "")
   /** Called from parser, which signals hereby that a method definition has been parsed.
    */
   override def signalParseProgress(pos: Position) {
-    checkForMoreWork(pos)
+    // We only want to be interruptible when running on the PC thread.
+    if(onCompilerThread) {
+      checkForMoreWork(pos)
+    }
   }
 
   /** Called from typechecker, which signals hereby that a node has been completely typechecked.
@@ -408,7 +411,7 @@ class Global(settings: Settings, _reporter: Reporter, projectName: String = "")
    */
   @elidable(elidable.WARNING)
   override def assertCorrectThread() {
-    assert(initializing || (Thread.currentThread() eq compileRunner),
+    assert(initializing || onCompilerThread,
         "Race condition detected: You are running a presentation compiler method outside the PC thread.[phase: %s]".format(globalPhase) +
         " Please file a ticket with the current stack trace at https://www.assembla.com/spaces/scala-ide/support/tickets")
   }
diff --git a/src/compiler/scala/tools/nsc/settings/ScalaSettings.scala b/src/compiler/scala/tools/nsc/settings/ScalaSettings.scala
index 9fe3016c02..a5496f829d 100644
--- a/src/compiler/scala/tools/nsc/settings/ScalaSettings.scala
+++ b/src/compiler/scala/tools/nsc/settings/ScalaSettings.scala
@@ -170,7 +170,6 @@ trait ScalaSettings extends AbsScalaSettings
   val etaExpandKeepsStar = BooleanSetting ("-Yeta-expand-keeps-star", "Eta-expand varargs methods to T* rather than Seq[T].  This is a temporary option to ease transition.")
   val Yinvalidate     = StringSetting     ("-Yinvalidate", "classpath-entry", "Invalidate classpath entry before run", "")
   val noSelfCheck     = BooleanSetting    ("-Yno-self-type-checks", "Suppress check for self-type conformance among inherited members.")
-  val companionsInPkgObjs = BooleanSetting("-Ycompanions-in-pkg-objs", "Allow companion objects and case classes in package objects. See issue SI-5954.")
   val YvirtClasses    = false // too embryonic to even expose as a -Y //BooleanSetting    ("-Yvirtual-classes", "Support virtual classes")
 
   val exposeEmptyPackage = BooleanSetting("-Yexpose-empty-package", "Internal only: expose the empty package.").internalOnly()
diff --git a/src/compiler/scala/tools/nsc/typechecker/Duplicators.scala b/src/compiler/scala/tools/nsc/typechecker/Duplicators.scala
index ab65e18093..face149b9f 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Duplicators.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Duplicators.scala
@@ -352,7 +352,7 @@ abstract class Duplicators extends Analyzer {
               cases
           }
 
-          super.typedPos(tree.pos, mode, pt)(Match(scrut, cases1))
+          super.typed(atPos(tree.pos)(Match(scrut, cases1)), mode, pt)
 
         case EmptyTree =>
           // no need to do anything, in particular, don't set the type to null, EmptyTree.tpe_= asserts
diff --git a/src/compiler/scala/tools/nsc/typechecker/PatternMatching.scala b/src/compiler/scala/tools/nsc/typechecker/PatternMatching.scala
index b2eb7c9a75..bbbc5cbb18 100644
--- a/src/compiler/scala/tools/nsc/typechecker/PatternMatching.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/PatternMatching.scala
@@ -105,9 +105,6 @@ trait PatternMatching extends Transform with TypingTransformers with ast.TreeDSL
   import definitions._
   import analyzer._ //Typer
 
-
-  case class DefaultOverrideMatchAttachment(default: Tree)
-
   object vpmName {
     val one       = newTermName("one")
     val drop      = newTermName("drop")
@@ -217,11 +214,11 @@ trait PatternMatching extends Transform with TypingTransformers with ast.TreeDSL
     // However this is a pain (at least the way I'm going about it)
     // and I have to think these detailed errors are primarily useful
     // for beginners, not people writing nested pattern matches.
-    def checkMatchVariablePatterns(m: Match) {
+    def checkMatchVariablePatterns(cases: List[CaseDef]) {
       // A string describing the first variable pattern
       var vpat: String = null
       // Using an iterator so we can recognize the last case
-      val it = m.cases.iterator
+      val it = cases.iterator
 
       def addendum(pat: Tree) = {
         matchingSymbolInScope(pat) match {
@@ -264,7 +261,15 @@ trait PatternMatching extends Transform with TypingTransformers with ast.TreeDSL
       */
     def translateMatch(match_ : Match): Tree = {
       val Match(selector, cases) = match_
-      checkMatchVariablePatterns(match_)
+
+      val (nonSyntheticCases, defaultOverride) = cases match {
+        case init :+ last if treeInfo isSyntheticDefaultCase last =>
+          (init, Some(((scrut: Tree) => last.body)))
+        case _ =>
+          (cases, None)
+      }
+
+      checkMatchVariablePatterns(nonSyntheticCases)
 
       // we don't transform after uncurry
       // (that would require more sophistication when generating trees,
@@ -291,14 +296,11 @@ trait PatternMatching extends Transform with TypingTransformers with ast.TreeDSL
       // pt is the skolemized version
       val pt = repeatedToSeq(ptUnCPS)
 
-      // the alternative to attaching the default case override would be to simply
-      // append the default to the list of cases and suppress the unreachable case error that may arise (once we detect that...)
-      val matchFailGenOverride = match_.attachments.get[DefaultOverrideMatchAttachment].map{case DefaultOverrideMatchAttachment(default) => ((scrut: Tree) => default)}
-
+      // val packedPt = repeatedToSeq(typer.packedType(match_, context.owner))
       val selectorSym = freshSym(selector.pos, pureType(selectorTp)) setFlag treeInfo.SYNTH_CASE_FLAGS
 
       // pt = Any* occurs when compiling test/files/pos/annotDepMethType.scala  with -Xexperimental
-      val combined = combineCases(selector, selectorSym, cases map translateCase(selectorSym, pt), pt, matchOwner, matchFailGenOverride)
+      val combined = combineCases(selector, selectorSym, nonSyntheticCases map translateCase(selectorSym, pt), pt, matchOwner, defaultOverride)
 
       if (Statistics.canEnable) Statistics.stopTimer(patmatNanos, start)
       combined
@@ -2814,7 +2816,9 @@ trait PatternMatching extends Transform with TypingTransformers with ast.TreeDSL
               // compare to the fully known type `tp` (modulo abstract types),
               // so that we can rule out stuff like: sealed trait X[T]; class XInt extends X[Int] --> XInt not valid when enumerating X[String]
               // however, must approximate abstract types in
-              val subTp       = appliedType(pre.memberType(sym), sym.typeParams.map(_ => WildcardType))
+
+              val memberType  = nestedMemberType(sym, pre, tpApprox.typeSymbol.owner)
+              val subTp       = appliedType(memberType, sym.typeParams.map(_ => WildcardType))
               val subTpApprox = typer.infer.approximateAbstracts(subTp) // TODO: needed?
               // patmatDebug("subtp"+(subTpApprox <:< tpApprox, subTpApprox, tpApprox))
               if (subTpApprox <:< tpApprox) Some(checkableType(subTp))
diff --git a/src/compiler/scala/tools/nsc/typechecker/SyntheticMethods.scala b/src/compiler/scala/tools/nsc/typechecker/SyntheticMethods.scala
index 9949e9181b..a2b0530c26 100644
--- a/src/compiler/scala/tools/nsc/typechecker/SyntheticMethods.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/SyntheticMethods.scala
@@ -6,6 +6,7 @@
 package scala.tools.nsc
 package typechecker
 
+import scala.collection.{ mutable, immutable }
 import symtab.Flags._
 import scala.collection.mutable.ListBuffer
 
@@ -48,6 +49,10 @@ trait SyntheticMethods extends ast.TreeDSL {
     else if (clazz.isDerivedValueClass) valueSymbols
     else Nil
   }
+  private lazy val renamedCaseAccessors = perRunCaches.newMap[Symbol, mutable.Map[TermName, TermName]]()
+  /** Does not force the info of `caseclazz` */
+  final def caseAccessorName(caseclazz: Symbol, paramName: TermName) =
+    (renamedCaseAccessors get caseclazz).fold(paramName)(_(paramName))
 
   /** Add the synthetic methods to case classes.
    */
@@ -369,6 +374,7 @@ trait SyntheticMethods extends ast.TreeDSL {
       def isRewrite(sym: Symbol) = sym.isCaseAccessorMethod && !sym.isPublic
 
       for (ddef @ DefDef(_, _, _, _, _, _) <- templ.body ; if isRewrite(ddef.symbol)) {
+        val original = ddef.symbol
         val newAcc = deriveMethod(ddef.symbol, name => context.unit.freshTermName(name + "$")) { newAcc =>
           newAcc.makePublic
           newAcc resetFlag (ACCESSOR | PARAMACCESSOR)
@@ -377,6 +383,8 @@ trait SyntheticMethods extends ast.TreeDSL {
         // TODO: shouldn't the next line be: `original resetFlag CASEACCESSOR`?
         ddef.symbol resetFlag CASEACCESSOR
         lb += logResult("case accessor new")(newAcc)
+        val renamedInClassMap = renamedCaseAccessors.getOrElseUpdate(clazz, mutable.Map() withDefault(x => x))
+        renamedInClassMap(original.name.toTermName) = newAcc.symbol.name.toTermName
       }
 
       (lb ++= templ.body ++= synthesize()).toList
diff --git a/src/compiler/scala/tools/nsc/typechecker/Typers.scala b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
index 6cf9dfdd5b..4ab3d684a2 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Typers.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
@@ -31,7 +31,6 @@ trait Typers extends Adaptations with Tags {
   import global._
   import definitions._
   import TypersStats._
-  import patmat.DefaultOverrideMatchAttachment
 
   final def forArgMode(fun: Tree, mode: Mode) =
     if (treeInfo.isSelfOrSuperConstrCall(fun)) mode | SCCmode
@@ -1838,29 +1837,29 @@ trait Typers extends Adaptations with Tags {
 
       // SI-5954. On second compile of a companion class contained in a package object we end up
       // with some confusion of names which leads to having two symbols with the same name in the
-      // same owner. Until that can be straightened out we can't allow companion objects in package
+      // same owner. Until that can be straightened out we will warn on companion objects in package
       // objects. But this code also tries to be friendly by distinguishing between case classes and
       // user written companion pairs
-      def restrictPackageObjectMembers(mdef : ModuleDef) = for (m <- mdef.symbol.info.members) {
+      def warnPackageObjectMembers(mdef : ModuleDef) = for (m <- mdef.symbol.info.members) {
         // ignore synthetic objects, because the "companion" object to a case class is synthetic and
         // we only want one error per case class
         if (!m.isSynthetic) {
           // can't handle case classes in package objects
-          if (m.isCaseClass) pkgObjectRestriction(m, mdef, "case")
+          if (m.isCaseClass) pkgObjectWarning(m, mdef, "case")
           // can't handle companion class/object pairs in package objects
           else if ((m.isClass && m.companionModule != NoSymbol && !m.companionModule.isSynthetic) ||
                    (m.isModule && m.companionClass != NoSymbol && !m.companionClass.isSynthetic))
-                     pkgObjectRestriction(m, mdef, "companion")
+                     pkgObjectWarning(m, mdef, "companion")
         }
 
-        def pkgObjectRestriction(m : Symbol, mdef : ModuleDef, restricted : String) = {
+        def pkgObjectWarning(m : Symbol, mdef : ModuleDef, restricted : String) = {
           val pkgName = mdef.symbol.ownerChain find (_.isPackage) map (_.decodedName) getOrElse mdef.symbol.toString
-          context.error(if (m.pos.isDefined) m.pos else mdef.pos, s"implementation restriction: package object ${pkgName} cannot contain ${restricted} ${m}. Instead, ${m} should be placed directly in package ${pkgName}.")
+          context.warning(if (m.pos.isDefined) m.pos else mdef.pos, s"${m} should be placed directly in package ${pkgName} instead of package object ${pkgName}. Under some circumstances companion objects and case classes in package objects can fail to recompile. See https://issues.scala-lang.org/browse/SI-5954.")
         }
       }
 
-      if (!settings.companionsInPkgObjs.value && mdef.symbol.isPackageObject)
-        restrictPackageObjectMembers(mdef)
+      if (mdef.symbol.isPackageObject)
+        warnPackageObjectMembers(mdef)
 
       treeCopy.ModuleDef(mdef, typedMods, mdef.name, impl2) setType NoType
     }
@@ -2075,7 +2074,7 @@ trait Typers extends Adaptations with Tags {
             val alias = (
               superAcc.initialize.alias
                 orElse (superAcc getter superAcc.owner)
-                filter (alias => superClazz.info.nonPrivateMember(alias.name) != alias)
+                filter (alias => superClazz.info.nonPrivateMember(alias.name) == alias)
             )
             if (alias.exists && !alias.accessed.isVariable) {
               val ownAcc = clazz.info decl name suchThat (_.isParamAccessor) match {
@@ -2562,8 +2561,13 @@ trait Typers extends Adaptations with Tags {
       def mkParam(methodSym: Symbol, tp: Type = argTp) =
         methodSym.newValueParameter(paramName, paramPos.focus, SYNTHETIC) setInfo tp
 
+      def mkDefaultCase(body: Tree) =
+        atPos(tree.pos.makeTransparent) {
+          CaseDef(Bind(nme.DEFAULT_CASE, Ident(nme.WILDCARD)), body)
+        }
+
       // `def applyOrElse[A1 <: $argTp, B1 >: $matchResTp](x: A1, default: A1 => B1): B1 =
-      //  ${`$selector match { $cases }` updateAttachment DefaultOverrideMatchAttachment(REF(default) APPLY (REF(x)))}`
+      //  ${`$selector match { $cases; case default$ => default(x) }`
       def applyOrElseMethodDef = {
         val methodSym = anonClass.newMethod(nme.applyOrElse, tree.pos, FINAL | OVERRIDE)
 
@@ -2572,7 +2576,7 @@ trait Typers extends Adaptations with Tags {
         val x = mkParam(methodSym, A1.tpe)
 
         // applyOrElse's default parameter:
-        val B1 = methodSym newTypeParameter (newTypeName("B1")) setInfo TypeBounds.empty //lower(resTp)
+        val B1 = methodSym newTypeParameter (newTypeName("B1")) setInfo TypeBounds.empty
         val default = methodSym newValueParameter (newTermName("default"), tree.pos.focus, SYNTHETIC) setInfo functionType(List(A1.tpe), B1.tpe)
 
         val paramSyms = List(x, default)
@@ -2582,19 +2586,72 @@ trait Typers extends Adaptations with Tags {
         // should use the DefDef for the context's tree, but it doesn't exist yet (we need the typer we're creating to create it)
         paramSyms foreach (methodBodyTyper.context.scope enter _)
 
-        val match_ = methodBodyTyper.typedMatch(selector, cases, mode, resTp)
+        // First, type without the default case; only the cases provided
+        // by the user are typed. The LUB of these becomes `B`, the lower
+        // bound of `B1`, which in turn is the result type of the default
+        // case
+        val match0 = methodBodyTyper.typedMatch(selector, cases, mode, resTp)
+        val matchResTp = match0.tpe
 
-        val matchResTp = match_.tpe
         B1 setInfo TypeBounds.lower(matchResTp) // patch info
 
+        // the default uses applyOrElse's first parameter since the scrut's type has been widened
+        val match_ = {
+          val defaultCase = methodBodyTyper.typedCase(
+            mkDefaultCase(methodBodyTyper.typed1(REF(default) APPLY (REF(x)), mode, B1.tpe).setType(B1.tpe)), argTp, B1.tpe)
+          treeCopy.Match(match0, match0.selector, match0.cases :+ defaultCase)
+        }
         match_ setType B1.tpe
 
-        // the default uses applyOrElse's first parameter since the scrut's type has been widened
-        val matchWithDefault = match_ updateAttachment DefaultOverrideMatchAttachment(REF(default) APPLY (REF(x)))
-        (DefDef(methodSym, methodBodyTyper.virtualizedMatch(matchWithDefault, mode, B1.tpe)), matchResTp)
+        // SI-6187 Do you really want to know? Okay, here's what's going on here.
+        //
+        //         Well behaved trees satisfy the property:
+        //
+        //         typed(tree) == typed(resetLocalAttrs(typed(tree))
+        //
+        //         Trees constructed without low-level symbol manipulation get this for free;
+        //         references to local symbols are cleared by `ResetAttrs`, but bind to the
+        //         corresponding symbol in the re-typechecked tree. But PartialFunction synthesis
+        //         doesn't play by these rules.
+        //
+        //         During typechecking of method bodies, references to method type parameter from
+        //         the declared types of the value parameters should bind to a fresh set of skolems,
+        //         which have been entered into scope by `Namer#methodSig`. A comment therein:
+        //
+        //         "since the skolemized tparams are in scope, the TypeRefs in vparamSymss refer to skolemized tparams"
+        //
+        //         But, if we retypecheck the reset `applyOrElse`, the TypeTree of the `default`
+        //         parameter contains no type. Somehow (where?!) it recovers a type that is _almost_ okay:
+        //         `A1 => B1`. But it should really be `A1&0 => B1&0`. In the test, run/t6187.scala, this
+        //         difference results in a type error, as `default.apply(x)` types as `B1`, which doesn't
+        //         conform to the required `B1&0`
+        //
+        //         I see three courses of action.
+        //
+        //         1) synthesize a `asInstanceOf[B1]` below (I tried this first. But... ewwww.)
+        //         2) install an 'original' TypeTree that will used after ResetAttrs (the solution below)
+        //         3) Figure out how the almost-correct type is recovered on re-typechecking, and
+        //            substitute in the skolems.
+        //
+        //         For 2.11, we'll probably shift this transformation back a phase or two, so macros
+        //         won't be affected. But in any case, we should satisfy retypecheckability.
+        //
+        val originals: Map[Symbol, Tree] = {
+          def typedIdent(sym: Symbol) = methodBodyTyper.typedType(Ident(sym), mode)
+          val A1Tpt = typedIdent(A1)
+          val B1Tpt = typedIdent(B1)
+          Map(
+            x -> A1Tpt,
+            default -> gen.scalaFunctionConstr(List(A1Tpt), B1Tpt)
+          )
+        }
+        val rhs = methodBodyTyper.virtualizedMatch(match_, mode, B1.tpe)
+        val defdef = DefDef(methodSym, Modifiers(methodSym.flags), originals, rhs)
+
+        (defdef, matchResTp)
       }
 
-      // `def isDefinedAt(x: $argTp): Boolean = ${`$selector match { $casesTrue ` updateAttachment DefaultOverrideMatchAttachment(FALSE)}`
+      // `def isDefinedAt(x: $argTp): Boolean = ${`$selector match { $casesTrue; case default$ => false } }`
       def isDefinedAtMethod = {
         val methodSym = anonClass.newMethod(nme.isDefinedAt, tree.pos.makeTransparent, FINAL)
         val paramSym = mkParam(methodSym)
@@ -2603,10 +2660,10 @@ trait Typers extends Adaptations with Tags {
         methodBodyTyper.context.scope enter paramSym
         methodSym setInfo MethodType(List(paramSym), BooleanClass.tpe)
 
-        val match_ = methodBodyTyper.typedMatch(selector, casesTrue, mode, BooleanClass.tpe)
+        val defaultCase = mkDefaultCase(FALSE)
+        val match_ = methodBodyTyper.typedMatch(selector, casesTrue :+ defaultCase, mode, BooleanClass.tpe)
 
-        val matchWithDefault = match_ updateAttachment DefaultOverrideMatchAttachment(FALSE)
-        DefDef(methodSym, methodBodyTyper.virtualizedMatch(matchWithDefault, mode, BooleanClass.tpe))
+        DefDef(methodSym, methodBodyTyper.virtualizedMatch(match_, mode, BooleanClass.tpe))
       }
 
       // only used for @cps annotated partial functions
@@ -2651,7 +2708,9 @@ trait Typers extends Adaptations with Tags {
       members foreach (m => anonClass.info.decls enter m.symbol)
 
       val typedBlock = typedPos(tree.pos, mode, pt) {
-        Block(ClassDef(anonClass, NoMods, ListOfNil, members, tree.pos.focus), atPos(tree.pos.focus)(New(anonClass.tpe)))
+        Block(ClassDef(anonClass, NoMods, ListOfNil, members, tree.pos.focus), atPos(tree.pos.focus)(
+          Apply(Select(New(Ident(anonClass.name).setSymbol(anonClass)), nme.CONSTRUCTOR), List())
+        ))
       }
 
       if (typedBlock.isErrorTyped) typedBlock
diff --git a/src/compiler/scala/tools/nsc/typechecker/Unapplies.scala b/src/compiler/scala/tools/nsc/typechecker/Unapplies.scala
index 36754999fc..589e5ce6fd 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Unapplies.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Unapplies.scala
@@ -82,12 +82,33 @@ trait Unapplies extends ast.TreeDSL
    *  @param param  The name of the parameter of the unapply method, assumed to be of type C[Ts]
    *  @param caseclazz  The case class C[Ts]
    */
-  private def caseClassUnapplyReturnValue(param: Name, caseclazz: Symbol) = {
-    def caseFieldAccessorValue(selector: Symbol): Tree = Ident(param) DOT selector
+  private def caseClassUnapplyReturnValue(param: Name, caseclazz: ClassDef) = {
+    def caseFieldAccessorValue(selector: ValDef): Tree = {
+      val accessorName = selector.name
+      val privateLocalParamAccessor = caseclazz.impl.body.collectFirst {
+        case dd: ValOrDefDef if dd.name == accessorName && dd.mods.isPrivateLocal => dd.symbol
+      }
+      privateLocalParamAccessor match {
+        case None =>
+          // Selecting by name seems to be the most straight forward way here to
+          // avoid forcing the symbol of the case class in order to list the accessors.
+          val maybeRenamedAccessorName = caseAccessorName(caseclazz.symbol, accessorName)
+          Ident(param) DOT maybeRenamedAccessorName
+        case Some(sym) =>
+          // But, that gives a misleading error message in neg/t1422.scala, where a case
+          // class has an illegal private[this] parameter. We can detect this by checking
+          // the modifiers on the param accessors.
+          //
+          // We just generate a call to that param accessor here, which gives us an inaccessible
+          // symbol error, as before.
+          Ident(param) DOT sym
+      }
+    }
 
-    caseclazz.caseFieldAccessors match {
-      case Nil      => TRUE
-      case xs       => SOME(xs map caseFieldAccessorValue: _*)
+    // Working with trees, rather than symbols, to avoid cycles like SI-5082
+    constrParamss(caseclazz).take(1).flatten match {
+      case Nil => TRUE
+      case xs  => SOME(xs map caseFieldAccessorValue: _*)
     }
   }
 
@@ -146,7 +167,7 @@ trait Unapplies extends ast.TreeDSL
     }
     val cparams   = List(ValDef(Modifiers(PARAM | SYNTHETIC), unapplyParamName, classType(cdef, tparams), EmptyTree))
     val ifNull    = if (constrParamss(cdef).head.isEmpty) FALSE else REF(NoneModule)
-    val body      = nullSafe({ case Ident(x) => caseClassUnapplyReturnValue(x, cdef.symbol) }, ifNull)(Ident(unapplyParamName))
+    val body      = nullSafe({ case Ident(x) => caseClassUnapplyReturnValue(x, cdef) }, ifNull)(Ident(unapplyParamName))
 
     atPos(cdef.pos.focus)(
       DefDef(caseMods, method, tparams, List(cparams), TypeTree(), body)
diff --git a/src/compiler/scala/tools/reflect/ToolBoxFactory.scala b/src/compiler/scala/tools/reflect/ToolBoxFactory.scala
index 7b065e7cf6..df9d907377 100644
--- a/src/compiler/scala/tools/reflect/ToolBoxFactory.scala
+++ b/src/compiler/scala/tools/reflect/ToolBoxFactory.scala
@@ -6,6 +6,7 @@ import scala.tools.nsc.reporters._
 import scala.tools.nsc.CompilerCommand
 import scala.tools.nsc.io.VirtualDirectory
 import scala.tools.nsc.interpreter.AbstractFileClassLoader
+import scala.reflect.internal.Flags._
 import scala.reflect.internal.util.{BatchSourceFile, NoSourceFile, NoFile}
 import java.lang.{Class => jClass}
 import scala.compat.Platform.EOL
@@ -209,8 +210,9 @@ abstract class ToolBoxFactory[U <: JavaUniverse](val u: U) { factorySelf =>
 
           val meth = obj.moduleClass.newMethod(newTermName(wrapperMethodName))
           def makeParam(schema: (FreeTermSymbol, TermName)) = {
+            // see a detailed explanation of the STABLE trick in `GenSymbols.reifyFreeTerm`
             val (fv, name) = schema
-            meth.newValueParameter(name) setInfo appliedType(definitions.FunctionClass(0).tpe, List(fv.tpe.resultType))
+            meth.newValueParameter(name, newFlags = if (fv.hasStableFlag) STABLE else 0) setInfo appliedType(definitions.FunctionClass(0).tpe, List(fv.tpe.resultType))
           }
           meth setInfo MethodType(freeTerms.map(makeParam).toList, AnyClass.tpe)
           minfo.decls enter meth
@@ -410,4 +412,3 @@ abstract class ToolBoxFactory[U <: JavaUniverse](val u: U) { factorySelf =>
     def eval(tree: u.Tree): Any = compile(tree)()
   }
 }
-
diff --git a/src/library/scala/collection/immutable/List.scala b/src/library/scala/collection/immutable/List.scala
index 654ed0286a..be233d06cb 100644
--- a/src/library/scala/collection/immutable/List.scala
+++ b/src/library/scala/collection/immutable/List.scala
@@ -55,6 +55,12 @@ import java.io._
  *  val shorter =  mainList.tail  // costs nothing as it uses the same 2::1::Nil instances as mainList
  *  }}}
  *
+ *  @note The functional list is characterized by persistence and structural sharing, thus offering considerable
+ *        performance and space consumption benefits in some scenarios if used correctly.
+ *        However, note that objects having multiple references into the same functional list (that is,
+ *        objects that rely on structural sharing), will be serialized and deserialized with multiple lists, one for
+ *        each reference to it. I.e. structural sharing is lost after serialization/deserialization.
+ *
  *  @author  Martin Odersky and others
  *  @version 2.8
  *  @since   1.0
@@ -305,7 +311,7 @@ sealed abstract class List[+A] extends AbstractSeq[A]
     }
     result
   }
-  
+
   override def foldRight[B](z: B)(op: (A, B) => B): B =
     reverse.foldLeft(z)((right, left) => op(left, right))
 
@@ -350,25 +356,8 @@ final case class ::[B](private var hd: B, private[scala] var tl: List[B]) extend
   override def tail : List[B] = tl
   override def isEmpty: Boolean = false
 
-  private def writeObject(out: ObjectOutputStream) {
-    out.writeObject(ListSerializeStart) // needed to differentiate with the legacy `::` serialization
-    out.writeObject(this.hd)
-    out.writeObject(this.tl)
-  }
-
   private def readObject(in: ObjectInputStream) {
-    val obj = in.readObject()
-    if (obj == ListSerializeStart) {
-      this.hd = in.readObject().asInstanceOf[B]
-      this.tl = in.readObject().asInstanceOf[List[B]]
-    } else oldReadObject(in, obj)
-  }
-
-  /* The oldReadObject method exists here for compatibility reasons.
-   * :: objects used to be serialized by serializing all the elements to
-   * the output stream directly, but this was broken (see SI-5374).
-   */
-  private def oldReadObject(in: ObjectInputStream, firstObject: AnyRef) {
+    val firstObject = in.readObject()
     hd = firstObject.asInstanceOf[B]
     assert(hd != ListSerializeEnd)
     var current: ::[B] = this
@@ -376,12 +365,18 @@ final case class ::[B](private var hd: B, private[scala] var tl: List[B]) extend
       case ListSerializeEnd =>
         current.tl = Nil
         return
-      case a : Any =>
+      case a =>
         val list : ::[B] = new ::(a.asInstanceOf[B], Nil)
         current.tl = list
         current = list
     }
   }
+
+  private def writeObject(out: ObjectOutputStream) {
+    var xs: List[B] = this
+    while (!xs.isEmpty) { out.writeObject(xs.head); xs = xs.tail }
+    out.writeObject(ListSerializeEnd)
+  }
 }
 
 /** $factoryInfo
@@ -401,10 +396,6 @@ object List extends SeqFactory[List] {
 }
 
 /** Only used for list serialization */
-@SerialVersionUID(0L - 8287891243975527522L)
-private[scala] case object ListSerializeStart
-
-/** Only used for list serialization */
 @SerialVersionUID(0L - 8476791151975527571L)
 private[scala] case object ListSerializeEnd
 
diff --git a/src/partest/scala/tools/partest/AsmNode.scala b/src/partest/scala/tools/partest/AsmNode.scala
new file mode 100644
index 0000000000..d181436676
--- /dev/null
+++ b/src/partest/scala/tools/partest/AsmNode.scala
@@ -0,0 +1,60 @@
+package scala.tools.partest
+
+import scala.collection.JavaConverters._
+import scala.tools.asm
+import asm._
+import asm.tree._
+import java.lang.reflect.Modifier
+
+sealed trait AsmNode[+T] {
+  def node: T
+  def access: Int
+  def desc: String
+  def name: String
+  def signature: String
+  def attrs: List[Attribute]
+  def visibleAnnotations: List[AnnotationNode]
+  def invisibleAnnotations: List[AnnotationNode]
+  def characteristics = f"$name%15s $desc%-30s$accessString$sigString"
+
+  private def accessString = if (access == 0) "" else " " + Modifier.toString(access)
+  private def sigString = if (signature == null) "" else " " + signature
+  override def toString = characteristics
+}
+
+object AsmNode {
+  type AsmMethod = AsmNode[MethodNode]
+  type AsmField = AsmNode[FieldNode]
+  type AsmMember = AsmNode[_]
+
+  implicit class ClassNodeOps(val node: ClassNode) {
+    def fieldsAndMethods: List[AsmMember] = {
+      val xs: List[AsmMember] = (
+           node.methods.asScala.toList.map(x => (x: AsmMethod))
+        ++ node.fields.asScala.toList.map(x => (x: AsmField))
+      )
+      xs sortBy (_.characteristics)
+    }
+  }
+  implicit class AsmMethodNode(val node: MethodNode) extends AsmNode[MethodNode] {
+    def access: Int                                = node.access
+    def desc: String                               = node.desc
+    def name: String                               = node.name
+    def signature: String                          = node.signature
+    def attrs: List[Attribute]                     = node.attrs.asScala.toList
+    def visibleAnnotations: List[AnnotationNode]   = node.visibleAnnotations.asScala.toList
+    def invisibleAnnotations: List[AnnotationNode] = node.invisibleAnnotations.asScala.toList
+  }
+  implicit class AsmFieldNode(val node: FieldNode) extends AsmNode[FieldNode] {
+    def access: Int                                = node.access
+    def desc: String                               = node.desc
+    def name: String                               = node.name
+    def signature: String                          = node.signature
+    def attrs: List[Attribute]                     = node.attrs.asScala.toList
+    def visibleAnnotations: List[AnnotationNode]   = node.visibleAnnotations.asScala.toList
+    def invisibleAnnotations: List[AnnotationNode] = node.invisibleAnnotations.asScala.toList
+  }
+
+  def apply(node: MethodNode): AsmMethodNode = new AsmMethodNode(node)
+  def apply(node: FieldNode): AsmFieldNode   = new AsmFieldNode(node)
+}
diff --git a/src/partest/scala/tools/partest/BytecodeTest.scala b/src/partest/scala/tools/partest/BytecodeTest.scala
index 41329a8264..2699083069 100644
--- a/src/partest/scala/tools/partest/BytecodeTest.scala
+++ b/src/partest/scala/tools/partest/BytecodeTest.scala
@@ -3,9 +3,10 @@ package scala.tools.partest
 import scala.tools.nsc.util.JavaClassPath
 import scala.collection.JavaConverters._
 import scala.tools.asm
-import asm.ClassReader
+import asm.{ ClassReader }
 import asm.tree.{ClassNode, MethodNode, InsnList}
 import java.io.InputStream
+import AsmNode._
 
 /**
  * Provides utilities for inspecting bytecode using ASM library.
@@ -29,13 +30,14 @@ import java.io.InputStream
  *
  */
 abstract class BytecodeTest extends ASMConverters {
+  import instructions._
 
   /** produce the output to be compared against a checkfile */
   protected def show(): Unit
 
   def main(args: Array[String]): Unit = show
 
-// asserts
+  // asserts
   def sameBytecode(methA: MethodNode, methB: MethodNode) = {
     val isa = instructions.fromMethod(methA)
     val isb = instructions.fromMethod(methB)
@@ -43,7 +45,32 @@ abstract class BytecodeTest extends ASMConverters {
     else diffInstructions(isa, isb)
   }
 
-  import instructions._
+  // Do these classes have all the same methods, with the same names, access,
+  // descriptors and generic signatures? Method bodies are not considered, and
+  // the names of the classes containing the methods are substituted so they do
+  // not appear as differences.
+  def sameMethodAndFieldSignatures(clazzA: ClassNode, clazzB: ClassNode): Boolean = {
+    val ms1 = clazzA.fieldsAndMethods.toIndexedSeq
+    val ms2 = clazzB.fieldsAndMethods.toIndexedSeq
+    val name1 = clazzA.name
+    val name2 = clazzB.name
+
+    if (ms1.length != ms2.length) {
+      println("Different member counts in $name1 and $name2")
+      false
+    }
+    else (ms1, ms2).zipped forall { (m1, m2) =>
+      val c1 = m1.characteristics
+      val c2 = m2.characteristics.replaceAllLiterally(name2, name1)
+      if (c1 == c2)
+        println(s"[ok] $m1")
+      else
+        println(s"[fail]\n  in $name1: $c1\n  in $name2: $c2")
+
+      c1 == c2
+    }
+  }
+
   // bytecode is equal modulo local variable numbering
   def equalsModuloVar(a: Instruction, b: Instruction) = (a, b) match {
     case _ if a == b => true
diff --git a/src/reflect/scala/reflect/internal/Flags.scala b/src/reflect/scala/reflect/internal/Flags.scala
index 6aa7eab689..45c5279574 100644
--- a/src/reflect/scala/reflect/internal/Flags.scala
+++ b/src/reflect/scala/reflect/internal/Flags.scala
@@ -287,7 +287,7 @@ class Flags extends ModifierFlags {
    *  from Modifiers.  Others which may be applied at creation time are:
    *  SYNTHETIC.
    */
-  final val ValueParameterFlags = BYNAMEPARAM | IMPLICIT | DEFAULTPARAM
+  final val ValueParameterFlags = BYNAMEPARAM | IMPLICIT | DEFAULTPARAM | STABLE
   final val BeanPropertyFlags   = DEFERRED | OVERRIDE | STATIC
   final val VarianceFlags       = COVARIANT | CONTRAVARIANT
 
diff --git a/src/reflect/scala/reflect/internal/StdNames.scala b/src/reflect/scala/reflect/internal/StdNames.scala
index 3d1701386e..a894bd649c 100644
--- a/src/reflect/scala/reflect/internal/StdNames.scala
+++ b/src/reflect/scala/reflect/internal/StdNames.scala
@@ -281,6 +281,7 @@ trait StdNames {
     // Compiler internal names
     val ANYname: NameType                  = "<anyname>"
     val CONSTRUCTOR: NameType              = "<init>"
+    val DEFAULT_CASE: NameType             = "defaultCase$"
     val EQEQ_LOCAL_VAR: NameType           = "eqEqTemp$"
     val FAKE_LOCAL_THIS: NameType          = "this$"
     val INITIALIZER: NameType              = CONSTRUCTOR // Is this buying us something?
@@ -551,6 +552,7 @@ trait StdNames {
     val RootPackage: NameType          = "RootPackage"
     val RootClass: NameType            = "RootClass"
     val Select: NameType               = "Select"
+    val SelectFromTypeTree: NameType   = "SelectFromTypeTree"
     val StringContext: NameType        = "StringContext"
     val This: NameType                 = "This"
     val ThisType: NameType             = "ThisType"
diff --git a/src/reflect/scala/reflect/internal/TreeInfo.scala b/src/reflect/scala/reflect/internal/TreeInfo.scala
index 9b8f86751e..1edfa84c04 100644
--- a/src/reflect/scala/reflect/internal/TreeInfo.scala
+++ b/src/reflect/scala/reflect/internal/TreeInfo.scala
@@ -92,12 +92,15 @@ abstract class TreeInfo {
       tree.symbol.isStable && isExprSafeToInline(qual)
     case TypeApply(fn, _) =>
       isExprSafeToInline(fn)
+    case Apply(Select(free @ Ident(_), nme.apply), _) if free.symbol.name endsWith nme.REIFY_FREE_VALUE_SUFFIX =>
+      // see a detailed explanation of this trick in `GenSymbols.reifyFreeTerm`
+      free.symbol.hasStableFlag && isExprSafeToInline(free)
     case Apply(fn, List()) =>
-      /* Note: After uncurry, field accesses are represented as Apply(getter, Nil),
-       * so an Apply can also be pure.
-       * However, before typing, applications of nullary functional values are also
-       * Apply(function, Nil) trees. To prevent them from being treated as pure,
-       * we check that the callee is a method. */
+      // Note: After uncurry, field accesses are represented as Apply(getter, Nil),
+      // so an Apply can also be pure.
+      // However, before typing, applications of nullary functional values are also
+      // Apply(function, Nil) trees. To prevent them from being treated as pure,
+      // we check that the callee is a method.
       fn.symbol.isMethod && !fn.symbol.isLazy && isExprSafeToInline(fn)
     case Typed(expr, _) =>
       isExprSafeToInline(expr)
@@ -421,6 +424,13 @@ abstract class TreeInfo {
     case _                   => false
   }
 
+  /** Is the argument a wildcard star type of the form `_*`?
+   */
+  def isWildcardStarType(tree: Tree): Boolean = tree match {
+    case Ident(tpnme.WILDCARD_STAR) => true
+    case _                          => false
+  }
+
   /** Is this pattern node a catch-all (wildcard or variable) pattern? */
   def isDefaultCase(cdef: CaseDef) = cdef match {
     case CaseDef(pat, EmptyTree, _) => isWildcardArg(pat)
@@ -444,6 +454,13 @@ abstract class TreeInfo {
     case _              => nme.NO_NAME
   }
 
+  /** Is this pattern node a synthetic catch-all case, added during PartialFuction synthesis before we know
+    * whether the user provided cases are exhaustive. */
+  def isSyntheticDefaultCase(cdef: CaseDef) = cdef match {
+    case CaseDef(Bind(nme.DEFAULT_CASE, _), EmptyTree, _) => true
+    case _                                                => false
+  }
+
   /** Does this CaseDef catch Throwable? */
   def catchesThrowable(cdef: CaseDef) = (
     cdef.guard.isEmpty && (unbind(cdef.pat) match {
diff --git a/src/reflect/scala/reflect/internal/Trees.scala b/src/reflect/scala/reflect/internal/Trees.scala
index 9b185c1c2d..408c7c648f 100644
--- a/src/reflect/scala/reflect/internal/Trees.scala
+++ b/src/reflect/scala/reflect/internal/Trees.scala
@@ -534,7 +534,11 @@ trait Trees extends api.Trees { self: SymbolTable =>
     override private[scala] def copyAttrs(tree: Tree) = {
       super.copyAttrs(tree)
       tree match {
-        case other: TypeTree => wasEmpty = other.wasEmpty // SI-6648 Critical for correct operation of `resetAttrs`.
+        case other: TypeTree =>
+          // SI-6648 Critical for correct operation of `resetAttrs`.
+          wasEmpty = other.wasEmpty
+          if (other.orig != null)
+            orig = other.orig.duplicate
         case _ =>
       }
       this
@@ -1009,6 +1013,18 @@ trait Trees extends api.Trees { self: SymbolTable =>
   def DefDef(sym: Symbol, mods: Modifiers, rhs: Tree): DefDef =
     DefDef(sym, mods, mapParamss(sym)(ValDef), rhs)
 
+  /** A DefDef with original trees attached to the TypeTree of each parameter */
+  def DefDef(sym: Symbol, mods: Modifiers, originalParamTpts: Symbol => Tree, rhs: Tree): DefDef = {
+    val paramms = mapParamss(sym){ sym =>
+      val vd = ValDef(sym, EmptyTree)
+      (vd.tpt : @unchecked) match {
+        case tt: TypeTree => tt setOriginal (originalParamTpts(sym) setPos sym.pos.focus)
+      }
+      vd
+    }
+    DefDef(sym, mods, paramms, rhs)
+  }
+
   def DefDef(sym: Symbol, rhs: Tree): DefDef =
     DefDef(sym, Modifiers(sym.flags), rhs)
 
diff --git a/src/reflect/scala/reflect/internal/Types.scala b/src/reflect/scala/reflect/internal/Types.scala
index 810ea70d58..ce7fae8628 100644
--- a/src/reflect/scala/reflect/internal/Types.scala
+++ b/src/reflect/scala/reflect/internal/Types.scala
@@ -561,9 +561,9 @@ trait Types extends api.Types { self: SymbolTable =>
      *  Expands type aliases and converts higher-kinded TypeRefs to PolyTypes.
      *  Functions on types are also implemented as PolyTypes.
      *
-     *  Example: (in the below, <List> is the type constructor of List)
-     *    TypeRef(pre, <List>, List()) is replaced by
-     *    PolyType(X, TypeRef(pre, <List>, List(X)))
+     *  Example: (in the below, `<List>` is the type constructor of List)
+     *    TypeRef(pre, `<List>`, List()) is replaced by
+     *    PolyType(X, TypeRef(pre, `<List>`, List(X)))
      *
      *  Discussion: normalize is NOT usually what you want to be calling.
      *  The (very real) danger with normalize is that it will force types
@@ -4578,23 +4578,39 @@ trait Types extends api.Types { self: SymbolTable =>
       }
     )
 
-    override def mapOver(tree: Tree, giveup: ()=>Nothing): Tree = {
-      object trans extends TypeMapTransformer {
+    object mapTreeSymbols extends TypeMapTransformer {
+      val strictCopy = newStrictTreeCopier
 
-        def termMapsTo(sym: Symbol) = from indexOf sym match {
-          case -1   => None
-          case idx  => Some(to(idx))
-        }
+      def termMapsTo(sym: Symbol) = from indexOf sym match {
+        case -1   => None
+        case idx  => Some(to(idx))
+      }
 
-        override def transform(tree: Tree) = {
-          termMapsTo(tree.symbol) match {
-            case Some(tosym) => tree.symbol = tosym
-            case None => ()
-          }
-          super.transform(tree)
+      // if tree.symbol is mapped to another symbol, passes the new symbol into the
+      // constructor `trans` and sets the symbol and the type on the resulting tree.
+      def transformIfMapped(tree: Tree)(trans: Symbol => Tree) = termMapsTo(tree.symbol) match {
+        case Some(toSym) => trans(toSym) setSymbol toSym setType tree.tpe
+        case None => tree
+      }
+
+      // changes trees which refer to one of the mapped symbols. trees are copied before attributes are modified.
+      override def transform(tree: Tree) = {
+        // super.transform maps symbol references in the types of `tree`. it also copies trees where necessary.
+        super.transform(tree) match {
+          case id @ Ident(_) =>
+            transformIfMapped(id)(toSym =>
+              strictCopy.Ident(id, toSym.name))
+
+          case sel @ Select(qual, name) =>
+            transformIfMapped(sel)(toSym =>
+              strictCopy.Select(sel, qual, toSym.name))
+
+          case tree => tree
         }
       }
-      trans.transform(tree)
+    }
+    override def mapOver(tree: Tree, giveup: ()=>Nothing): Tree = {
+      mapTreeSymbols.transform(tree)
     }
   }
 
@@ -4843,6 +4859,51 @@ trait Types extends api.Types { self: SymbolTable =>
     }
   }
 
+  /**
+   * A more persistent version of `Type#memberType` which does not require
+   * that the symbol is a direct member of the prefix.
+   *
+   * For instance:
+   *
+   * {{{
+   * class C[T] {
+   *   sealed trait F[A]
+   *   object X {
+   *     object S1 extends F[T]
+   *   }
+   *   class S2 extends F[T]
+   * }
+   * object O extends C[Int] {
+   *   def foo(f: F[Int]) = f match {...} // need to enumerate sealed subtypes of the scrutinee here.
+   * }
+   * class S3 extends O.F[String]
+   *
+   * nestedMemberType(<S1>, <O.type>, <C>) = O.X.S1.type
+   * nestedMemberType(<S2>, <O.type>, <C>) = O.S2.type
+   * nestedMemberType(<S3>, <O.type>, <C>) = S3.type
+   * }}}
+   *
+   * @param sym    The symbol of the subtype
+   * @param pre    The prefix from which the symbol is seen
+   * @param owner
+   */
+  def nestedMemberType(sym: Symbol, pre: Type, owner: Symbol): Type = {
+    def loop(tp: Type): Type =
+      if (tp.isTrivial) tp
+      else if (tp.prefix.typeSymbol isNonBottomSubClass owner) {
+        val widened = tp match {
+          case _: ConstantType => tp        // Java enum constants: don't widen to the enum type!
+          case _               => tp.widen  // C.X.type widens to C.this.X.type, otherwise `tp asSeenFrom (pre, C)` has no effect.
+        }
+        widened asSeenFrom (pre, tp.typeSymbol.owner)
+      }
+      else loop(tp.prefix) memberType tp.typeSymbol
+
+    val result = loop(sym.tpeHK)
+    assert(sym.isTerm || result.typeSymbol == sym, s"($result).typeSymbol = ${result.typeSymbol}; expected ${sym}")
+    result
+  }
+
   /** The most deeply nested owner that contains all the symbols
    *  of thistype or prefixless typerefs/singletype occurrences in given type.
    */
diff --git a/src/reflect/scala/reflect/internal/settings/MutableSettings.scala b/src/reflect/scala/reflect/internal/settings/MutableSettings.scala
index 3ea8cff989..d5ed9dab5b 100644
--- a/src/reflect/scala/reflect/internal/settings/MutableSettings.scala
+++ b/src/reflect/scala/reflect/internal/settings/MutableSettings.scala
@@ -47,6 +47,4 @@ abstract class MutableSettings extends AbsSettings {
   def XnoPatmatAnalysis: BooleanSetting
   def XfullLubs: BooleanSetting
   def breakCycles: BooleanSetting
-  def companionsInPkgObjs: BooleanSetting
-  
 }
diff --git a/src/reflect/scala/reflect/runtime/Settings.scala b/src/reflect/scala/reflect/runtime/Settings.scala
index 9472cefbbf..ba524f4df2 100644
--- a/src/reflect/scala/reflect/runtime/Settings.scala
+++ b/src/reflect/scala/reflect/runtime/Settings.scala
@@ -43,7 +43,6 @@ private[reflect] class Settings extends MutableSettings {
   val uniqid            = new BooleanSetting(false)
   val verbose           = new BooleanSetting(false)
   val breakCycles       = new BooleanSetting(false)
-  val companionsInPkgObjs = new BooleanSetting(false)
 
   val Yrecursion        = new IntSetting(0)
   val maxClassfileName  = new IntSetting(255)