Merge master.

113 files changed, 1717 insertions, 1027 deletions

diff --git a/src/android-library/scala/reflect/ScalaBeanInfo.scala b/src/android-library/scala/reflect/ScalaBeanInfo.scala
deleted file mode 100644
index 05c7bced71..0000000000
--- a/src/android-library/scala/reflect/ScalaBeanInfo.scala
+++ /dev/null
@@ -1 +0,0 @@
-/* ScalaBeanInfo does not exist for the Android target */
diff --git a/src/compiler/scala/reflect/reify/codegen/GenSymbols.scala b/src/compiler/scala/reflect/reify/codegen/GenSymbols.scala
index 67bc93d407..90fb41f80b 100644
--- a/src/compiler/scala/reflect/reify/codegen/GenSymbols.scala
+++ b/src/compiler/scala/reflect/reify/codegen/GenSymbols.scala
@@ -42,7 +42,7 @@ trait GenSymbols {
     else if (sym.isPackage)
       mirrorMirrorCall(nme.staticPackage, reify(sym.fullName))
     else if (sym.isLocatable) {
-      /** This is a fancy conundrum that stems from the fact that Scala allows
+      /*  This is a fancy conundrum that stems from the fact that Scala allows
        *  packageless packages and packageless objects with the same names in the same program.
        *
        *  For more details read the docs to staticModule and staticPackage.
diff --git a/src/compiler/scala/tools/ant/sabbus/ScalacFork.scala b/src/compiler/scala/tools/ant/sabbus/ScalacFork.scala
index 76820b8060..363c31f6c4 100644
--- a/src/compiler/scala/tools/ant/sabbus/ScalacFork.scala
+++ b/src/compiler/scala/tools/ant/sabbus/ScalacFork.scala
@@ -114,7 +114,7 @@ class ScalacFork extends ScalaMatchingTask with ScalacShared with TaskArgs {
         mapper
       ) map (x => new File(sourceDir, x))
 
-    /** Nothing to do. */
+    /* Nothing to do. */
     if (includedFiles.isEmpty && argfile.isEmpty)
       return
 
diff --git a/src/compiler/scala/tools/cmd/CommandLine.scala b/src/compiler/scala/tools/cmd/CommandLine.scala
index cf0463423c..e8ac882ee6 100644
--- a/src/compiler/scala/tools/cmd/CommandLine.scala
+++ b/src/compiler/scala/tools/cmd/CommandLine.scala
@@ -36,7 +36,7 @@ class CommandLine(val spec: Reference, val originalArgs: List[String]) extends C
     def loop(args: List[String]): Map[String, String] = {
       def residual(xs: List[String]) = { residualBuffer ++= xs ; Map[String, String]() }
 
-      /** Returns Some(List(args)) if this option expands to an
+      /*  Returns Some(List(args)) if this option expands to an
        *  argument list and it's not returning only the same arg.
        */
       def expand(s1: String) = {
@@ -48,7 +48,7 @@ class CommandLine(val spec: Reference, val originalArgs: List[String]) extends C
         else None
       }
 
-      /** Assumes known options have all been ruled out already. */
+      /* Assumes known options have all been ruled out already. */
       def isUnknown(opt: String) =
         onlyKnownOptions && (opt startsWith "-") && {
           errorFn("Option '%s' not recognized.".format(opt))
diff --git a/src/compiler/scala/tools/nsc/Global.scala b/src/compiler/scala/tools/nsc/Global.scala
index 7ee3ee551f..c53d6cd11e 100644
--- a/src/compiler/scala/tools/nsc/Global.scala
+++ b/src/compiler/scala/tools/nsc/Global.scala
@@ -25,7 +25,7 @@ import transform._
 import backend.icode.{ ICodes, GenICode, ICodeCheckers }
 import backend.{ ScalaPrimitives, Platform, JavaPlatform }
 import backend.jvm.GenASM
-import backend.opt.{ Inliners, InlineExceptionHandlers, ClosureElimination, DeadCodeElimination }
+import backend.opt.{ Inliners, InlineExceptionHandlers, ConstantOptimization, ClosureElimination, DeadCodeElimination }
 import backend.icode.analysis._
 import scala.language.postfixOps
 
@@ -594,6 +594,13 @@ class Global(var currentSettings: Settings, var reporter: Reporter)
     val runsRightAfter = None
   } with ClosureElimination
 
+  // phaseName = "constopt"
+  object constantOptimization extends {
+    val global: Global.this.type = Global.this
+    val runsAfter = List("closelim")
+    val runsRightAfter = None
+  } with ConstantOptimization
+
   // phaseName = "dce"
   object deadCode extends {
     val global: Global.this.type = Global.this
@@ -678,6 +685,7 @@ class Global(var currentSettings: Settings, var reporter: Reporter)
       inliner                 -> "optimization: do inlining",
       inlineExceptionHandlers -> "optimization: inline exception handlers",
       closureElimination      -> "optimization: eliminate uncalled closures",
+      constantOptimization    -> "optimization: optimize null and other constants",
       deadCode                -> "optimization: eliminate dead code",
       terminal                -> "The last phase in the compiler chain"
     )
@@ -795,8 +803,6 @@ class Global(var currentSettings: Settings, var reporter: Reporter)
     } reverse
   }
 
-  private def numberedPhase(ph: Phase) = "%2d/%s".format(ph.id, ph.name)
-
   // ------------ Invalidations ---------------------------------
 
   /** Is given package class a system package class that cannot be invalidated?
@@ -1106,7 +1112,7 @@ class Global(var currentSettings: Settings, var reporter: Reporter)
   override def currentRunId = curRunId
 
   def echoPhaseSummary(ph: Phase) = {
-    /** Only output a summary message under debug if we aren't echoing each file. */
+    /* Only output a summary message under debug if we aren't echoing each file. */
     if (settings.debug.value && !(settings.verbose.value || currentRun.size < 5))
       inform("[running phase " + ph.name + " on " + currentRun.size +  " compilation units]")
   }
@@ -1200,7 +1206,7 @@ class Global(var currentSettings: Settings, var reporter: Reporter)
       curRunId += 1
       curRun = this
 
-      /** Set phase to a newly created syntaxAnalyzer and call definitions.init. */
+      /* Set phase to a newly created syntaxAnalyzer and call definitions.init. */
       val parserPhase: Phase = syntaxAnalyzer.newPhase(NoPhase)
       phase = parserPhase
       definitions.init()
diff --git a/src/compiler/scala/tools/nsc/ScriptRunner.scala b/src/compiler/scala/tools/nsc/ScriptRunner.scala
index 92b2dc79ed..821e88e52e 100644
--- a/src/compiler/scala/tools/nsc/ScriptRunner.scala
+++ b/src/compiler/scala/tools/nsc/ScriptRunner.scala
@@ -84,8 +84,8 @@ class ScriptRunner extends HasCompileSocket {
   {
     def mainClass = scriptMain(settings)
 
-    /** Compiles the script file, and returns the directory with the compiled
-     *  class files, if the compilation succeeded.
+    /* Compiles the script file, and returns the directory with the compiled
+     * class files, if the compilation succeeded.
      */
     def compile: Option[Directory] = {
       val compiledPath = Directory makeTemp "scalascript"
@@ -96,8 +96,8 @@ class ScriptRunner extends HasCompileSocket {
       settings.outdir.value = compiledPath.path
 
       if (settings.nc.value) {
-        /** Setting settings.script.value informs the compiler this is not a
-         *  self contained compilation unit.
+        /* Setting settings.script.value informs the compiler this is not a
+         * self contained compilation unit.
          */
         settings.script.value = mainClass
         val reporter = new ConsoleReporter(settings)
@@ -110,8 +110,8 @@ class ScriptRunner extends HasCompileSocket {
       else None
     }
 
-    /** The script runner calls sys.exit to communicate a return value, but this must
-     *  not take place until there are no non-daemon threads running.  Tickets #1955, #2006.
+    /* The script runner calls sys.exit to communicate a return value, but this must
+     * not take place until there are no non-daemon threads running.  Tickets #1955, #2006.
      */
     util.waitingForThreads {
       if (settings.save.value) {
diff --git a/src/compiler/scala/tools/nsc/ast/DocComments.scala b/src/compiler/scala/tools/nsc/ast/DocComments.scala
index 3397797927..5ad494177c 100755
--- a/src/compiler/scala/tools/nsc/ast/DocComments.scala
+++ b/src/compiler/scala/tools/nsc/ast/DocComments.scala
@@ -501,7 +501,7 @@ trait DocComments { self: Global =>
         result
       }
 
-      /**
+      /*
        * work around the backticks issue suggested by Simon in
        * https://groups.google.com/forum/?hl=en&fromgroups#!topic/scala-internals/z7s1CCRCz74
        * ideally, we'd have a removeWikiSyntax method in the CommentFactory to completely eliminate the wiki markup
diff --git a/src/compiler/scala/tools/nsc/ast/Positions.scala b/src/compiler/scala/tools/nsc/ast/Positions.scala
index 63a2dd0ee7..66d75969e9 100644
--- a/src/compiler/scala/tools/nsc/ast/Positions.scala
+++ b/src/compiler/scala/tools/nsc/ast/Positions.scala
@@ -1,8 +1,6 @@
 package scala.tools.nsc
 package ast
 
-import scala.reflect.internal.util.{ SourceFile, OffsetPosition }
-
 trait Positions extends scala.reflect.internal.Positions {
   self: Global =>
 
diff --git a/src/compiler/scala/tools/nsc/ast/TreeGen.scala b/src/compiler/scala/tools/nsc/ast/TreeGen.scala
index b9eb511a9a..692afbac66 100644
--- a/src/compiler/scala/tools/nsc/ast/TreeGen.scala
+++ b/src/compiler/scala/tools/nsc/ast/TreeGen.scala
@@ -19,18 +19,6 @@ abstract class TreeGen extends scala.reflect.internal.TreeGen with TreeDSL {
   import global._
   import definitions._
 
-  def mkCheckInit(tree: Tree): Tree = {
-    val tpe =
-      if (tree.tpe != null || !tree.hasSymbolField) tree.tpe
-      else tree.symbol.tpe
-
-    if (!global.phase.erasedTypes && settings.warnSelectNullable.value &&
-        tpe <:< NotNullClass.tpe && !tpe.isNotNull)
-      mkRuntimeCall(nme.checkInitialized, List(tree))
-    else
-      tree
-  }
-
   /** Builds a fully attributed wildcard import node.
    */
   def mkWildcardImport(pkg: Symbol): Import = {
diff --git a/src/compiler/scala/tools/nsc/ast/Trees.scala b/src/compiler/scala/tools/nsc/ast/Trees.scala
index 6c5c087d55..8391ebdafc 100644
--- a/src/compiler/scala/tools/nsc/ast/Trees.scala
+++ b/src/compiler/scala/tools/nsc/ast/Trees.scala
@@ -100,12 +100,11 @@ trait Trees extends scala.reflect.internal.Trees { self: Global =>
         if (body forall treeInfo.isInterfaceMember) List()
         else List(
           atPos(wrappingPos(superPos, lvdefs)) (
-            DefDef(NoMods, nme.MIXIN_CONSTRUCTOR, List(), ListOfNil, TypeTree(), Block(lvdefs, Literal(Constant())))))
+            DefDef(NoMods, nme.MIXIN_CONSTRUCTOR, List(), ListOfNil, TypeTree(), Block(lvdefs, Literal(Constant(()))))))
       } else {
         // convert (implicit ... ) to ()(implicit ... ) if its the only parameter section
         if (vparamss1.isEmpty || !vparamss1.head.isEmpty && vparamss1.head.head.mods.isImplicit)
           vparamss1 = List() :: vparamss1
-        val superRef: Tree = atPos(superPos)(gen.mkSuperInitCall)
         val superCall = pendingSuperCall // we can't know in advance which of the parents will end up as a superclass
                                          // this requires knowing which of the parents is a type macro and which is not
                                          // and that's something that cannot be found out before typer
@@ -116,7 +115,7 @@ trait Trees extends scala.reflect.internal.Trees { self: Global =>
           // TODO: previously this was `wrappingPos(superPos, lvdefs ::: argss.flatten)`
           // is it going to be a problem that we can no longer include the `argss`?
           atPos(wrappingPos(superPos, lvdefs)) (
-            DefDef(constrMods, nme.CONSTRUCTOR, List(), vparamss1, TypeTree(), Block(lvdefs ::: List(superCall), Literal(Constant())))))
+            DefDef(constrMods, nme.CONSTRUCTOR, List(), vparamss1, TypeTree(), Block(lvdefs ::: List(superCall), Literal(Constant(()))))))
       }
     }
     constrs foreach (ensureNonOverlapping(_, parents ::: gvdefs, focus=false))
diff --git a/src/compiler/scala/tools/nsc/ast/parser/Parsers.scala b/src/compiler/scala/tools/nsc/ast/parser/Parsers.scala
index 9218ad3330..68e198d071 100644
--- a/src/compiler/scala/tools/nsc/ast/parser/Parsers.scala
+++ b/src/compiler/scala/tools/nsc/ast/parser/Parsers.scala
@@ -57,7 +57,7 @@ trait ParsersCommon extends ScannersCommon {
       if (in.token == LPAREN) inParens(body)
       else { accept(LPAREN) ; alt }
 
-    @inline final def inParensOrUnit[T](body: => Tree): Tree = inParensOrError(body, Literal(Constant()))
+    @inline final def inParensOrUnit[T](body: => Tree): Tree = inParensOrError(body, Literal(Constant(())))
     @inline final def inParensOrNil[T](body: => List[T]): List[T] = inParensOrError(body, Nil)
 
     @inline final def inBraces[T](body: => T): T = {
@@ -71,7 +71,7 @@ trait ParsersCommon extends ScannersCommon {
       else { accept(LBRACE) ; alt }
 
     @inline final def inBracesOrNil[T](body: => List[T]): List[T] = inBracesOrError(body, Nil)
-    @inline final def inBracesOrUnit[T](body: => Tree): Tree = inBracesOrError(body, Literal(Constant()))
+    @inline final def inBracesOrUnit[T](body: => Tree): Tree = inBracesOrError(body, Literal(Constant(())))
     @inline final def dropAnyBraces[T](body: => T): T =
       if (in.token == LBRACE) inBraces(body)
       else body
@@ -321,38 +321,38 @@ self =>
       accept(EOF)
 
       def mainModuleName = newTermName(settings.script.value)
-      /** If there is only a single object template in the file and it has a
-       *  suitable main method, we will use it rather than building another object
-       *  around it.  Since objects are loaded lazily the whole script would have
-       *  been a no-op, so we're not taking much liberty.
+      /* If there is only a single object template in the file and it has a
+       * suitable main method, we will use it rather than building another object
+       * around it.  Since objects are loaded lazily the whole script would have
+       * been a no-op, so we're not taking much liberty.
        */
       def searchForMain(): Option[Tree] = {
-        /** Have to be fairly liberal about what constitutes a main method since
-         *  nothing has been typed yet - for instance we can't assume the parameter
-         *  type will look exactly like "Array[String]" as it could have been renamed
-         *  via import, etc.
+        /* Have to be fairly liberal about what constitutes a main method since
+         * nothing has been typed yet - for instance we can't assume the parameter
+         * type will look exactly like "Array[String]" as it could have been renamed
+         * via import, etc.
          */
         def isMainMethod(t: Tree) = t match {
           case DefDef(_, nme.main, Nil, List(_), _, _)  => true
           case _                                        => false
         }
-        /** For now we require there only be one top level object. */
+        /* For now we require there only be one top level object. */
         var seenModule = false
         val newStmts = stmts collect {
           case t @ Import(_, _) => t
           case md @ ModuleDef(mods, name, template) if !seenModule && (md exists isMainMethod) =>
             seenModule = true
-            /** This slightly hacky situation arises because we have no way to communicate
-             *  back to the scriptrunner what the name of the program is.  Even if we were
-             *  willing to take the sketchy route of settings.script.value = progName, that
-             *  does not work when using fsc.  And to find out in advance would impose a
-             *  whole additional parse.  So instead, if the actual object's name differs from
-             *  what the script is expecting, we transform it to match.
+            /* This slightly hacky situation arises because we have no way to communicate
+             * back to the scriptrunner what the name of the program is.  Even if we were
+             * willing to take the sketchy route of settings.script.value = progName, that
+             * does not work when using fsc.  And to find out in advance would impose a
+             * whole additional parse.  So instead, if the actual object's name differs from
+             * what the script is expecting, we transform it to match.
              */
             if (name == mainModuleName) md
             else treeCopy.ModuleDef(md, mods, mainModuleName, template)
           case _ =>
-            /** If we see anything but the above, fail. */
+            /* If we see anything but the above, fail. */
             return None
         }
         Some(makePackaging(0, emptyPkg, newStmts))
@@ -1249,7 +1249,7 @@ self =>
           newLinesOpt()
           val thenp = expr()
           val elsep = if (in.token == ELSE) { in.nextToken(); expr() }
-          else Literal(Constant())
+          else Literal(Constant(()))
           If(cond, thenp, elsep)
         }
         parseIf
@@ -1323,7 +1323,7 @@ self =>
       case RETURN =>
         def parseReturn =
           atPos(in.skipToken()) {
-            Return(if (isExprIntro) expr() else Literal(Constant()))
+            Return(if (isExprIntro) expr() else Literal(Constant(())))
           }
         parseReturn
       case THROW =>
@@ -2265,8 +2265,8 @@ self =>
         accept(DOT)
         result
       }
-      /** Walks down import `foo.bar.baz.{ ... }` until it ends at a
-       *  an underscore, a left brace, or an undotted identifier.
+      /* Walks down import `foo.bar.baz.{ ... }` until it ends at a
+       * an underscore, a left brace, or an undotted identifier.
        */
       def loop(expr: Tree): Tree = {
         expr setPos expr.pos.makeTransparent
@@ -2524,7 +2524,7 @@ self =>
      */
     def constrExpr(vparamss: List[List[ValDef]]): Tree =
       if (in.token == LBRACE) constrBlock(vparamss)
-      else Block(List(selfInvocation(vparamss)), Literal(Constant()))
+      else Block(List(selfInvocation(vparamss)), Literal(Constant(())))
 
     /** {{{
      *  SelfInvocation  ::= this ArgumentExprs {ArgumentExprs}
@@ -2554,7 +2554,7 @@ self =>
           else Nil
         }
         accept(RBRACE)
-        Block(stats, Literal(Constant()))
+        Block(stats, Literal(Constant(())))
       }
 
     /** {{{
@@ -2760,7 +2760,7 @@ self =>
       def anyvalConstructor() = (
         // Not a well-formed constructor, has to be finished later - see note
         // regarding AnyVal constructor in AddInterfaces.
-        DefDef(NoMods, nme.CONSTRUCTOR, Nil, ListOfNil, TypeTree(), Block(Nil, Literal(Constant())))
+        DefDef(NoMods, nme.CONSTRUCTOR, Nil, ListOfNil, TypeTree(), Block(Nil, Literal(Constant(()))))
       )
       val tstart0 = if (body.isEmpty && in.lastOffset < tstart) in.lastOffset else tstart
 
@@ -2986,7 +2986,7 @@ self =>
         else List(tmplDef(pos, mods))
 
       in.token match {
-        case RBRACE | CASE  => defs :+ (Literal(Constant()) setPos o2p(in.offset))
+        case RBRACE | CASE  => defs :+ (Literal(Constant(())) setPos o2p(in.offset))
         case _              => defs
       }
     }
diff --git a/src/compiler/scala/tools/nsc/ast/parser/Scanners.scala b/src/compiler/scala/tools/nsc/ast/parser/Scanners.scala
index 6ad1c50075..b485e862fd 100644
--- a/src/compiler/scala/tools/nsc/ast/parser/Scanners.scala
+++ b/src/compiler/scala/tools/nsc/ast/parser/Scanners.scala
@@ -303,11 +303,11 @@ trait Scanners extends ScannersCommon {
         next.token = EMPTY
       }
 
-      /** Insert NEWLINE or NEWLINES if
-       *  - we are after a newline
-       *  - we are within a { ... } or on toplevel (wrt sepRegions)
-       *  - the current token can start a statement and the one before can end it
-       *  insert NEWLINES if we are past a blank line, NEWLINE otherwise
+      /* Insert NEWLINE or NEWLINES if
+       * - we are after a newline
+       * - we are within a { ... } or on toplevel (wrt sepRegions)
+       * - the current token can start a statement and the one before can end it
+       * insert NEWLINES if we are past a blank line, NEWLINE otherwise
        */
       if (!applyBracePatch() && afterLineEnd() && inLastOfStat(lastToken) && inFirstOfStat(token) &&
           (sepRegions.isEmpty || sepRegions.head == RBRACE)) {
@@ -440,7 +440,7 @@ trait Scanners extends ScannersCommon {
               nextChar()
               base = 16
             } else {
-              /**
+              /*
                * What should leading 0 be in the future? It is potentially dangerous
                *  to let it be base-10 because of history.  Should it be an error? Is
                *  there a realistic situation where one would need it?
@@ -959,7 +959,7 @@ trait Scanners extends ScannersCommon {
       }
       token = INTLIT
 
-      /** When we know for certain it's a number after using a touch of lookahead */
+      /* When we know for certain it's a number after using a touch of lookahead */
       def restOfNumber() = {
         putChar(ch)
         nextChar()
@@ -987,8 +987,8 @@ trait Scanners extends ScannersCommon {
         val lookahead = lookaheadReader
         val c = lookahead.getc()
 
-        /** As of scala 2.11, it isn't a number unless c here is a digit, so
-         *  settings.future.value excludes the rest of the logic.
+        /* As of scala 2.11, it isn't a number unless c here is a digit, so
+         * settings.future.value excludes the rest of the logic.
          */
         if (settings.future.value && !isDigit(c))
           return setStrVal()
@@ -998,16 +998,16 @@ trait Scanners extends ScannersCommon {
           case '0' | '1' | '2' | '3' | '4' | '5' | '6' | '7' | '8' | '9'  =>
             true
 
-          /** Backquoted idents like 22.`foo`. */
+          /* Backquoted idents like 22.`foo`. */
           case '`' =>
             return setStrVal()  /** Note the early return */
 
-          /** These letters may be part of a literal, or a method invocation on an Int.
+          /* These letters may be part of a literal, or a method invocation on an Int.
            */
           case 'd' | 'D' | 'f' | 'F' =>
             !isIdentifierPart(lookahead.getc())
 
-          /** A little more special handling for e.g. 5e7 */
+          /* A little more special handling for e.g. 5e7 */
           case 'e' | 'E' =>
             val ch = lookahead.getc()
             !isIdentifierPart(ch) || (isDigit(ch) || ch == '+' || ch == '-')
diff --git a/src/compiler/scala/tools/nsc/ast/parser/SymbolicXMLBuilder.scala b/src/compiler/scala/tools/nsc/ast/parser/SymbolicXMLBuilder.scala
index cdcfd0b834..f326212d5b 100755
--- a/src/compiler/scala/tools/nsc/ast/parser/SymbolicXMLBuilder.scala
+++ b/src/compiler/scala/tools/nsc/ast/parser/SymbolicXMLBuilder.scala
@@ -196,7 +196,7 @@ abstract class SymbolicXMLBuilder(p: Parsers#Parser, preserveWS: Boolean) {
       uri1
     }
 
-    /** Extract all the namespaces from the attribute map. */
+    /* Extract all the namespaces from the attribute map. */
     val namespaces: List[Tree] =
       for (z <- attrMap.keys.toList ; if z startsWith xmlns) yield {
         val ns = splitPrefix(z) match {
diff --git a/src/compiler/scala/tools/nsc/ast/parser/TreeBuilder.scala b/src/compiler/scala/tools/nsc/ast/parser/TreeBuilder.scala
index d70b1f4d9c..5f361f32b5 100644
--- a/src/compiler/scala/tools/nsc/ast/parser/TreeBuilder.scala
+++ b/src/compiler/scala/tools/nsc/ast/parser/TreeBuilder.scala
@@ -131,7 +131,7 @@ abstract class TreeBuilder {
   }
 
   def makeTupleTerm(trees: List[Tree], flattenUnary: Boolean): Tree = trees match {
-    case Nil => Literal(Constant())
+    case Nil => Literal(Constant(()))
     case List(tree) if flattenUnary => tree
     case _ => makeTuple(trees, isType = false)
   }
@@ -250,21 +250,21 @@ abstract class TreeBuilder {
   /** Create tree representing a while loop */
   def makeWhile(lname: TermName, cond: Tree, body: Tree): Tree = {
     val continu = atPos(o2p(body.pos pointOrElse wrappingPos(List(cond, body)).pos.endOrPoint)) { Apply(Ident(lname), Nil) }
-    val rhs = If(cond, Block(List(body), continu), Literal(Constant()))
+    val rhs = If(cond, Block(List(body), continu), Literal(Constant(())))
     LabelDef(lname, Nil, rhs)
   }
 
   /** Create tree representing a do-while loop */
   def makeDoWhile(lname: TermName, body: Tree, cond: Tree): Tree = {
     val continu = Apply(Ident(lname), Nil)
-    val rhs = Block(List(body), If(cond, continu, Literal(Constant())))
+    val rhs = Block(List(body), If(cond, continu, Literal(Constant(()))))
     LabelDef(lname, Nil, rhs)
   }
 
   /** Create block of statements `stats`  */
   def makeBlock(stats: List[Tree]): Tree =
-    if (stats.isEmpty) Literal(Constant())
-    else if (!stats.last.isTerm) Block(stats, Literal(Constant()))
+    if (stats.isEmpty) Literal(Constant(()))
+    else if (!stats.last.isTerm) Block(stats, Literal(Constant(())))
     else if (stats.length == 1) stats.head
     else Block(stats.init, stats.last)
 
@@ -353,9 +353,9 @@ abstract class TreeBuilder {
   */
   private def makeFor(mapName: TermName, flatMapName: TermName, enums: List[Enumerator], body: Tree): Tree = {
 
-    /** make a closure pat => body.
-     *  The closure is assigned a transparent position with the point at pos.point and
-     *  the limits given by pat and body.
+    /* make a closure pat => body.
+     * The closure is assigned a transparent position with the point at pos.point and
+     * the limits given by pat and body.
      */
     def makeClosure(pos: Position, pat: Tree, body: Tree): Tree = {
       def splitpos = wrappingPos(List(pat, body)).withPoint(pos.point).makeTransparent
@@ -371,26 +371,23 @@ abstract class TreeBuilder {
       }
     }
 
-    /** Make an application  qual.meth(pat => body) positioned at `pos`.
+    /* Make an application  qual.meth(pat => body) positioned at `pos`.
      */
     def makeCombination(pos: Position, meth: TermName, qual: Tree, pat: Tree, body: Tree): Tree =
       Apply(Select(qual, meth) setPos qual.pos, List(makeClosure(pos, pat, body))) setPos pos
 
-    /** If `pat` is not yet a `Bind` wrap it in one with a fresh name
-     */
+    /* If `pat` is not yet a `Bind` wrap it in one with a fresh name */
     def makeBind(pat: Tree): Tree = pat match {
       case Bind(_, _) => pat
       case _ => Bind(freshName(), pat) setPos pat.pos
     }
 
-    /** A reference to the name bound in Bind `pat`.
-     */
+    /* A reference to the name bound in Bind `pat`. */
     def makeValue(pat: Tree): Tree = pat match {
       case Bind(name, _) => Ident(name) setPos pat.pos.focus
     }
 
-    /** The position of the closure that starts with generator at position `genpos`.
-     */
+    /* The position of the closure that starts with generator at position `genpos`. */
     def closurePos(genpos: Position) = {
       val end = body.pos match {
         case NoPosition => genpos.point
diff --git a/src/compiler/scala/tools/nsc/backend/JavaPlatform.scala b/src/compiler/scala/tools/nsc/backend/JavaPlatform.scala
index 08602f87dc..00f2933fab 100644
--- a/src/compiler/scala/tools/nsc/backend/JavaPlatform.scala
+++ b/src/compiler/scala/tools/nsc/backend/JavaPlatform.scala
@@ -7,7 +7,7 @@ package scala.tools.nsc
 package backend
 
 import io.AbstractFile
-import util.{ClassPath,JavaClassPath,MergedClassPath,DeltaClassPath}
+import util.{ClassPath,MergedClassPath,DeltaClassPath}
 import scala.tools.util.PathResolver
 
 trait JavaPlatform extends Platform {
diff --git a/src/compiler/scala/tools/nsc/backend/icode/BasicBlocks.scala b/src/compiler/scala/tools/nsc/backend/icode/BasicBlocks.scala
index d772dcb6c4..89682e91d2 100644
--- a/src/compiler/scala/tools/nsc/backend/icode/BasicBlocks.scala
+++ b/src/compiler/scala/tools/nsc/backend/icode/BasicBlocks.scala
@@ -68,10 +68,10 @@ trait BasicBlocks {
           addBlock(scratchBlocks.head)
           scratchBlocks = scratchBlocks.tail
         }
-        /** Return a list of successors for 'b' that come from exception handlers
-         *  covering b's (non-exceptional) successors. These exception handlers
-         *  might not cover 'b' itself. This situation corresponds to an
-         *  exception being thrown as the first thing of one of b's successors.
+        /* Return a list of successors for 'b' that come from exception handlers
+         * covering b's (non-exceptional) successors. These exception handlers
+         * might not cover 'b' itself. This situation corresponds to an
+         * exception being thrown as the first thing of one of b's successors.
          */
         while (scratchHandlers ne Nil) {
           val handler = scratchHandlers.head
@@ -332,8 +332,8 @@ trait BasicBlocks {
 
       if (ignore) {
         if (settings.debug.value) {
-          /** Trying to pin down what it's likely to see after a block has been
-           *  put into ignore mode so we hear about it if there's a problem.
+          /* Trying to pin down what it's likely to see after a block has been
+           * put into ignore mode so we hear about it if there's a problem.
            */
           instr match {
             case JUMP(_) | RETURN(_) | THROW(_) | SCOPE_EXIT(_)               => // ok
diff --git a/src/compiler/scala/tools/nsc/backend/icode/GenICode.scala b/src/compiler/scala/tools/nsc/backend/icode/GenICode.scala
index 94116d6783..8ba75fbb46 100644
--- a/src/compiler/scala/tools/nsc/backend/icode/GenICode.scala
+++ b/src/compiler/scala/tools/nsc/backend/icode/GenICode.scala
@@ -276,8 +276,8 @@ abstract class GenICode extends SubComponent  {
         generatedType = elem
         ctx1.bb.emit(LOAD_ARRAY_ITEM(elementType), tree.pos)
         // it's tempting to just drop array loads of type Null instead
-        // of adapting them but array accesses can cause 
-        // ArrayIndexOutOfBounds so we can't. Besides, Array[Null] 
+        // of adapting them but array accesses can cause
+        // ArrayIndexOutOfBounds so we can't. Besides, Array[Null]
         // probably isn't common enough to figure out an optimization
         adaptNullRef(generatedType, expectedType, ctx1, tree.pos)
       }
@@ -479,11 +479,11 @@ abstract class GenICode extends SubComponent  {
       val resCtx: Context = tree match {
         case LabelDef(name, params, rhs) =>
           def genLoadLabelDef = {
-            val ctx1 = ctx.newBlock() // note: we cannot kill ctx1 if ctx is in ignore mode because 
+            val ctx1 = ctx.newBlock() // note: we cannot kill ctx1 if ctx is in ignore mode because
                                       // label defs can be the target of jumps from other locations.
                                       // that means label defs can lead to unreachable code without
                                       // proper reachability analysis
-            
+
             if (nme.isLoopHeaderLabel(name))
               ctx1.bb.loopHeader = true
 
@@ -777,8 +777,8 @@ abstract class GenICode extends SubComponent  {
               ctx1 = genLoadArguments(args, sym.info.paramTypes, ctx1)
               val cm = CALL_METHOD(sym, invokeStyle)
 
-              /** In a couple cases, squirrel away a little extra information in the
-               *  CALL_METHOD for use by GenASM.
+              /* In a couple cases, squirrel away a little extra information in the
+               * CALL_METHOD for use by GenASM.
                */
               fun match {
                 case Select(qual, _) =>
@@ -1018,7 +1018,7 @@ abstract class GenICode extends SubComponent  {
 
       resCtx
     }
-    
+
     /**
      * If we have a method call, field load, or array element load of type Null then
      * we need to convince the JVM that we have a null value because in Scala
@@ -1030,9 +1030,9 @@ abstract class GenICode extends SubComponent  {
      */
     private def adaptNullRef(from: TypeKind, to: TypeKind, ctx: Context, pos: Position) {
       log(s"GenICode#adaptNullRef($from, $to, $ctx, $pos)")
-      
+
       // Don't need to adapt null to unit because we'll just drop it anyway. Don't
-      // need to adapt to Object or AnyRef because the JVM is happy with 
+      // need to adapt to Object or AnyRef because the JVM is happy with
       // upcasting Null to them.
       // We do have to adapt from NullReference to NullReference because we could be storing
       // this value into a local of type Null and we want the JVM to see that it's
@@ -1066,12 +1066,12 @@ abstract class GenICode extends SubComponent  {
           ctx.bb.enterIgnoreMode()
         case _ if from isAssignabledTo to =>
           ()
-        case (_, UNIT) => 
+        case (_, UNIT) =>
           ctx.bb.emit(DROP(from), pos)
         // otherwise we'd better be doing a primtive -> primitive coercion or there's a problem
-        case _ if !from.isRefOrArrayType && !to.isRefOrArrayType => 
+        case _ if !from.isRefOrArrayType && !to.isRefOrArrayType =>
           coerce(from, to)
-        case _ =>   
+        case _ =>
           assert(false, s"Can't convert from $from to $to in unit ${unit.source} at $pos")
       }
     }
@@ -1356,10 +1356,10 @@ abstract class GenICode extends SubComponent  {
                         ctx: Context,
                         thenCtx: Context,
                         elseCtx: Context): Boolean =
-    {      
+    {
       /**
        * Generate the de-sugared comparison mechanism that will underly an '=='
-       * 
+       *
        * @param l       left-hand side of the '=='
        * @param r       right-hand side of the '=='
        * @param code    the comparison operator to use
@@ -1470,11 +1470,11 @@ abstract class GenICode extends SubComponent  {
         ctx.makeLocal(l.pos, AnyRefClass.tpe, nme.EQEQ_LOCAL_VAR.toString)
       }
 
-      /** True if the equality comparison is between values that require the use of the rich equality
-        * comparator (scala.runtime.Comparator.equals). This is the case when either side of the
-        * comparison might have a run-time type subtype of java.lang.Number or java.lang.Character.
-        * When it is statically known that both sides are equal and subtypes of Number of Character,
-        * not using the rich equality is possible (their own equals method will do ok.)*/
+      /* True if the equality comparison is between values that require the use of the rich equality
+       * comparator (scala.runtime.Comparator.equals). This is the case when either side of the
+       * comparison might have a run-time type subtype of java.lang.Number or java.lang.Character.
+       * When it is statically known that both sides are equal and subtypes of Number of Character,
+       * not using the rich equality is possible (their own equals method will do ok.)*/
       def mustUseAnyComparator: Boolean = {
         def areSameFinals = l.tpe.isFinalType && r.tpe.isFinalType && (l.tpe =:= r.tpe)
         !areSameFinals && isMaybeBoxed(l.tpe.typeSymbol) && isMaybeBoxed(r.tpe.typeSymbol)
@@ -1568,12 +1568,12 @@ abstract class GenICode extends SubComponent  {
       debugassert(ctx.clazz.symbol eq cls,
                "Classes are not the same: " + ctx.clazz.symbol + ", " + cls)
 
-      /** Non-method term members are fields, except for module members. Module
-       *  members can only happen on .NET (no flatten) for inner traits. There,
-       *  a module symbol is generated (transformInfo in mixin) which is used
-       *  as owner for the members of the implementation class (so that the
-       *  backend emits them as static).
-       *  No code is needed for this module symbol.
+      /* Non-method term members are fields, except for module members. Module
+       * members can only happen on .NET (no flatten) for inner traits. There,
+       * a module symbol is generated (transformInfo in mixin) which is used
+       * as owner for the members of the implementation class (so that the
+       * backend emits them as static).
+       * No code is needed for this module symbol.
        */
       for (f <- cls.info.decls ; if !f.isMethod && f.isTerm && !f.isModule)
         ctx.clazz addField new IField(f)
@@ -1961,34 +1961,34 @@ abstract class GenICode extends SubComponent  {
        *   }), (AnotherExceptionClass,
        *   ctx => {...
        *   } ))`
-       *   
+       *
        *   The resulting structure will look something like
-       *   
+       *
        *   outer:
        *     // this 'useless' jump will be removed later,
        *     // for now it separates the try body's blocks from previous
        *     // code since the try body needs its own exception handlers
        *     JUMP body
-       *     
+       *
        *   body:
        *     [ try body ]
        *     JUMP normalExit
-       *     
+       *
        *   catch[i]:
        *     [ handler[i] body ]
        *     JUMP normalExit
-       *     
+       *
        *   catchAll:
        *     STORE exception
        *     [ finally body ]
        *     THROW exception
-       *     
+       *
        *   normalExit:
        *     [ finally body ]
-       *     
+       *
        *  each catch[i] will cover body.  catchAll will cover both body and each catch[i]
        *  Additional finally copies are created on the emission of every RETURN in the try body and exception handlers.
-       *  
+       *
        *  This could result in unreachable code which has to be cleaned up later, e.g. if the try and all the exception
        *  handlers always end in RETURN then there will be no "normal" flow out of the try/catch/finally.
        *  Later reachability analysis will remove unreacahble code.
@@ -2047,7 +2047,7 @@ abstract class GenICode extends SubComponent  {
             exhEndCtx.bb.enterIgnoreMode()
             finalizerCtx.endHandler()
           }
-  
+
           // Generate each exception handler
           for ((sym, kind, handler) <- handlers) {
             val exh = this.newExceptionHandler(sym, tree.pos)
diff --git a/src/compiler/scala/tools/nsc/backend/icode/ICodeCheckers.scala b/src/compiler/scala/tools/nsc/backend/icode/ICodeCheckers.scala
index 82fdcbbc04..b7b07a579f 100644
--- a/src/compiler/scala/tools/nsc/backend/icode/ICodeCheckers.scala
+++ b/src/compiler/scala/tools/nsc/backend/icode/ICodeCheckers.scala
@@ -169,10 +169,10 @@ abstract class ICodeCheckers {
 
       def hasNothingType(s: TypeStack) = s.nonEmpty && (s.head == NothingReference)
 
-      /** XXX workaround #1: one stack empty, the other has BoxedUnit.
-       *  One example where this arises is:
+      /* XXX workaround #1: one stack empty, the other has BoxedUnit.
+       * One example where this arises is:
        *
-       *  def f(b: Boolean): Unit = synchronized { if (b) () }
+       * def f(b: Boolean): Unit = synchronized { if (b) () }
        */
       def allUnits(s: TypeStack)   = s.types forall (_ == BoxedUnitReference)
 
@@ -181,10 +181,10 @@ abstract class ICodeCheckers {
         case (x1, x2) if f(x2)  => x1
       }
 
-      /** XXX workaround #2: different stacks heading into an exception
-       *  handler which will clear them anyway.  Examples where it arises:
+      /* XXX workaround #2: different stacks heading into an exception
+       * handler which will clear them anyway.  Examples where it arises:
        *
-       *  var bippy: Int = synchronized { if (b) 5 else 10 }
+       * var bippy: Int = synchronized { if (b) 5 else 10 }
        */
       def isHandlerBlock() = bl.exceptionHandlerStart
 
@@ -336,7 +336,7 @@ abstract class ICodeCheckers {
       def popStack2    = { checkStack(2) ; (popStackN(2): @unchecked) match { case List(x, y) => (x, y) } }
       def popStack3    = { checkStack(3) ; (popStackN(3): @unchecked) match { case List(x, y, z) => (x, y, z) } }
 
-      /** Called by faux instruction LOAD_EXCEPTION to wipe out the stack. */
+      /* Called by faux instruction LOAD_EXCEPTION to wipe out the stack. */
       def clearStack() = {
         if (stack.nonEmpty)
           logChecker("Wiping out the " + stack.length + " element stack for exception handler: " + stack)
@@ -385,7 +385,7 @@ abstract class ICodeCheckers {
             icodeError(" expected reference type, but " + obj + " found")
         }
 
-        /** Checks that tpe is a subtype of one of the allowed types */
+        /* Checks that tpe is a subtype of one of the allowed types */
         def checkType(tpe: TypeKind, allowed: TypeKind*) = (
           if (allowed exists (k => isSubtype(tpe, k))) ()
           else icodeError(tpe + " is not one of: " + allowed.mkString("{ ", ", ", " }"))
@@ -393,16 +393,14 @@ abstract class ICodeCheckers {
         def checkNumeric(tpe: TypeKind) =
           checkType(tpe, BYTE, CHAR, SHORT, INT, LONG, FLOAT, DOUBLE)
 
-        /** Checks that the 2 topmost elements on stack are of the
-         *  kind TypeKind.
-         */
+        /* Checks that the 2 topmost elements on stack are of the kind TypeKind. */
         def checkBinop(kind: TypeKind) {
           val (a, b) = popStack2
           checkType(a, kind)
           checkType(b, kind)
         }
 
-        /** Check that arguments on the stack match method params. */
+        /* Check that arguments on the stack match method params. */
         def checkMethodArgs(method: Symbol) {
           val params = method.info.paramTypes
           checkStack(params.length)
@@ -412,8 +410,8 @@ abstract class ICodeCheckers {
           )
         }
 
-        /** Checks that the object passed as receiver has a method
-         *  `method` and that it is callable from the current method.
+        /* Checks that the object passed as receiver has a method
+         * `method` and that it is callable from the current method.
          */
         def checkMethod(receiver: TypeKind, method: Symbol) =
           receiver match {
diff --git a/src/compiler/scala/tools/nsc/backend/icode/TypeKinds.scala b/src/compiler/scala/tools/nsc/backend/icode/TypeKinds.scala
index 1875c8c914..2c8fda85f4 100644
--- a/src/compiler/scala/tools/nsc/backend/icode/TypeKinds.scala
+++ b/src/compiler/scala/tools/nsc/backend/icode/TypeKinds.scala
@@ -130,21 +130,21 @@ trait TypeKinds { self: ICodes =>
    * The lub is based on the lub of scala types.
    */
   def lub(a: TypeKind, b: TypeKind): TypeKind = {
-    /** The compiler's lub calculation does not order classes before traits.
-     *  This is apparently not wrong but it is inconvenient, and causes the
-     *  icode checker to choke when things don't match up.  My attempts to
-     *  alter the calculation at the compiler level were failures, so in the
-     *  interests of a working icode checker I'm making the adjustment here.
+    /* The compiler's lub calculation does not order classes before traits.
+     * This is apparently not wrong but it is inconvenient, and causes the
+     * icode checker to choke when things don't match up.  My attempts to
+     * alter the calculation at the compiler level were failures, so in the
+     * interests of a working icode checker I'm making the adjustment here.
      *
-     *  Example where we'd like a different answer:
+     * Example where we'd like a different answer:
      *
-     *    abstract class Tom
-     *    case object Bob extends Tom
-     *    case object Harry extends Tom
-     *    List(Bob, Harry)  // compiler calculates "Product with Tom" rather than "Tom with Product"
+     *   abstract class Tom
+     *   case object Bob extends Tom
+     *   case object Harry extends Tom
+     *   List(Bob, Harry)  // compiler calculates "Product with Tom" rather than "Tom with Product"
      *
-     *  Here we make the adjustment by rewinding to a pre-erasure state and
-     *  sifting through the parents for a class type.
+     * Here we make the adjustment by rewinding to a pre-erasure state and
+     * sifting through the parents for a class type.
      */
     def lub0(tk1: TypeKind, tk2: TypeKind): Type = enteringUncurry {
       val tp = global.lub(List(tk1.toType, tk2.toType))
diff --git a/src/compiler/scala/tools/nsc/backend/jvm/BytecodeWriters.scala b/src/compiler/scala/tools/nsc/backend/jvm/BytecodeWriters.scala
index c1cd3204e0..66aed14d1c 100644
--- a/src/compiler/scala/tools/nsc/backend/jvm/BytecodeWriters.scala
+++ b/src/compiler/scala/tools/nsc/backend/jvm/BytecodeWriters.scala
@@ -6,12 +6,15 @@
 package scala.tools.nsc
 package backend.jvm
 
-import java.io.{ DataOutputStream, FileOutputStream, OutputStream, File => JFile }
+import java.io.{ DataOutputStream, FileOutputStream, IOException, OutputStream, File => JFile }
 import scala.tools.nsc.io._
 import scala.tools.nsc.util.ScalaClassLoader
 import java.util.jar.Attributes.Name
 import scala.language.postfixOps
 
+/** Can't output a file due to the state of the file system. */
+class FileConflictException(msg: String, val file: AbstractFile) extends IOException(msg)
+
 /** For the last mile: turning generated bytecode in memory into
  *  something you can use.  Has implementations for writing to class
  *  files, jars, and disassembled/javap output.
@@ -20,16 +23,20 @@ trait BytecodeWriters {
   val global: Global
   import global._
 
-  private def outputDirectory(sym: Symbol): AbstractFile = (
-    settings.outputDirs.outputDirFor(enteringFlatten(sym.sourceFile))
-  )
-  private def getFile(base: AbstractFile, /*cls.getName()*/ clsName: String, suffix: String): AbstractFile = {
+  private def outputDirectory(sym: Symbol): AbstractFile =
+    settings.outputDirs outputDirFor enteringFlatten(sym.sourceFile)
+
+  /**
+   * @param clsName cls.getName
+   */
+  private def getFile(base: AbstractFile, clsName: String, suffix: String): AbstractFile = {
+    def ensureDirectory(dir: AbstractFile): AbstractFile =
+      if (dir.isDirectory) dir
+      else throw new FileConflictException(s"${base.path}/$clsName$suffix: ${dir.path} is not a directory", dir)
     var dir = base
     val pathParts = clsName.split("[./]").toList
-    for (part <- pathParts.init) {
-      dir = dir.subdirectoryNamed(part)
-    }
-    dir.fileNamed(pathParts.last + suffix)
+    for (part <- pathParts.init) dir = ensureDirectory(dir) subdirectoryNamed part
+    ensureDirectory(dir) fileNamed pathParts.last + suffix
   }
   private def getFile(sym: Symbol, clsName: String, suffix: String): AbstractFile =
     getFile(outputDirectory(sym), clsName, suffix)
diff --git a/src/compiler/scala/tools/nsc/backend/jvm/GenASM.scala b/src/compiler/scala/tools/nsc/backend/jvm/GenASM.scala
index 4a3d1805d9..2aa874b567 100644
--- a/src/compiler/scala/tools/nsc/backend/jvm/GenASM.scala
+++ b/src/compiler/scala/tools/nsc/backend/jvm/GenASM.scala
@@ -105,29 +105,30 @@ abstract class GenASM extends SubComponent with BytecodeWriters with GenJVMASM {
           "Such classes will overwrite one another on case-insensitive filesystems.")
       }
 
-      debuglog("Created new bytecode generator for " + classes.size + " classes.")
+      debuglog(s"Created new bytecode generator for ${classes.size} classes.")
       val bytecodeWriter  = initBytecodeWriter(sortedClasses filter isJavaEntryPoint)
       val plainCodeGen    = new JPlainBuilder(bytecodeWriter)
       val mirrorCodeGen   = new JMirrorBuilder(bytecodeWriter)
       val beanInfoCodeGen = new JBeanInfoBuilder(bytecodeWriter)
 
-      while(!sortedClasses.isEmpty) {
-        val c = sortedClasses.head
-
+      def emitFor(c: IClass) {
         if (isStaticModule(c.symbol) && isTopLevelModule(c.symbol)) {
-          if (c.symbol.companionClass == NoSymbol) {
-            mirrorCodeGen.genMirrorClass(c.symbol, c.cunit)
-          } else {
-            log("No mirror class for module with linked class: " + c.symbol.fullName)
-          }
+          if (c.symbol.companionClass == NoSymbol)
+            mirrorCodeGen genMirrorClass (c.symbol, c.cunit)
+          else
+            log(s"No mirror class for module with linked class: ${c.symbol.fullName}")
         }
+        plainCodeGen genClass c
+        if (c.symbol hasAnnotation BeanInfoAttr) beanInfoCodeGen genBeanInfoClass c
+      }
 
-        plainCodeGen.genClass(c)
-
-        if (c.symbol hasAnnotation BeanInfoAttr) {
-          beanInfoCodeGen.genBeanInfoClass(c)
+      while (!sortedClasses.isEmpty) {
+        val c = sortedClasses.head
+        try emitFor(c)
+        catch {
+          case e: FileConflictException =>
+            c.cunit.error(c.symbol.pos, s"error writing ${c.symbol}: ${e.getMessage}")
         }
-
         sortedClasses = sortedClasses.tail
         classes -= c.symbol // GC opportunity
       }
@@ -454,7 +455,7 @@ abstract class GenASM extends SubComponent with BytecodeWriters with GenJVMASM {
     }
 
     // -----------------------------------------------------------------------------------------
-    // utitilies useful when emitting plain, mirror, and beaninfo classes.
+    // utilities useful when emitting plain, mirror, and beaninfo classes.
     // -----------------------------------------------------------------------------------------
 
     def writeIfNotTooBig(label: String, jclassName: String, jclass: asm.ClassWriter, sym: Symbol) {
@@ -513,7 +514,7 @@ abstract class GenASM extends SubComponent with BytecodeWriters with GenJVMASM {
      */
     def javaName(sym: Symbol): String = {
 
-        /**
+        /*
          * Checks if given symbol corresponds to inner class/object and add it to innerClassBuffer
          *
          * Note: This method is called recursively thus making sure that we add complete chain
@@ -608,9 +609,9 @@ abstract class GenASM extends SubComponent with BytecodeWriters with GenJVMASM {
     def isDeprecated(sym: Symbol): Boolean = { sym.annotations exists (_ matches definitions.DeprecatedAttr) }
 
     def addInnerClasses(csym: Symbol, jclass: asm.ClassVisitor) {
-      /** The outer name for this inner class. Note that it returns null
-       *  when the inner class should not get an index in the constant pool.
-       *  That means non-member classes (anonymous). See Section 4.7.5 in the JVMS.
+      /* The outer name for this inner class. Note that it returns null
+       * when the inner class should not get an index in the constant pool.
+       * That means non-member classes (anonymous). See Section 4.7.5 in the JVMS.
        */
       def outerName(innerSym: Symbol): String = {
         if (innerSym.originalEnclosingMethod != NoSymbol)
@@ -1044,9 +1045,9 @@ abstract class GenASM extends SubComponent with BytecodeWriters with GenJVMASM {
       val paramJavaTypes: List[asm.Type] = methodInfo.paramTypes map javaType
       // val paramNames     = 0 until paramJavaTypes.length map ("x_" + _)
 
-      /** Forwarders must not be marked final,
-       *  as the JVM will not allow redefinition of a final static method,
-       *  and we don't know what classes might be subclassing the companion class.  See SI-4827.
+      /* Forwarders must not be marked final,
+       * as the JVM will not allow redefinition of a final static method,
+       * and we don't know what classes might be subclassing the companion class.  See SI-4827.
        */
       // TODO: evaluate the other flags we might be dropping on the floor here.
       // TODO: ACC_SYNTHETIC ?
@@ -1270,8 +1271,8 @@ abstract class GenASM extends SubComponent with BytecodeWriters with GenJVMASM {
           case _                => None
         }
 
-        /** Drop redundant interfaces (ones which are implemented by some other parent) from the immediate parents.
-         *  This is important on Android because there is otherwise an interface explosion.
+        /* Drop redundant interfaces (ones which are implemented by some other parent) from the immediate parents.
+         * This is important on Android because there is otherwise an interface explosion.
          */
         def minimizeInterfaces(lstIfaces: List[Symbol]): List[Symbol] = {
           var rest   = lstIfaces
@@ -1397,7 +1398,6 @@ abstract class GenASM extends SubComponent with BytecodeWriters with GenJVMASM {
       addInnerClasses(clasz.symbol, jclass)
       jclass.visitEnd()
       writeIfNotTooBig("" + c.symbol.name, thisName, jclass, c.symbol)
-
     }
 
     /**
@@ -1847,7 +1847,7 @@ abstract class GenASM extends SubComponent with BytecodeWriters with GenJVMASM {
         val keyMax = keys(keys.length - 1)
 
         val isDenseEnough: Boolean = {
-          /** Calculate in long to guard against overflow. TODO what overflow??? */
+          /* Calculate in long to guard against overflow. TODO what overflow??? */
           val keyRangeD: Double = (keyMax.asInstanceOf[Long] - keyMin + 1).asInstanceOf[Double]
           val klenD:     Double = keys.length
           val kdensity:  Double = (klenD / keyRangeD)
@@ -1982,7 +1982,7 @@ abstract class GenASM extends SubComponent with BytecodeWriters with GenJVMASM {
       // Part 2 of genCode(): demarcating exception handler boundaries (visitTryCatchBlock() must be invoked before visitLabel() in genBlock())
       // ------------------------------------------------------------------------------------------------------------
 
-        /**Generate exception handlers for the current method.
+        /* Generate exception handlers for the current method.
          *
          * Quoting from the JVMS 4.7.3 The Code Attribute
          * The items of the Code_attribute structure are as follows:
@@ -2005,16 +2005,16 @@ abstract class GenASM extends SubComponent with BytecodeWriters with GenJVMASM {
          */
         def genExceptionHandlers() {
 
-          /** Return a list of pairs of intervals where the handler is active.
-           *  Each interval is closed on both ends, ie. inclusive both in the left and right endpoints: [start, end].
-           *  Preconditions:
-           *    - e.covered non-empty
-           *  Postconditions for the result:
-           *    - always non-empty
-           *    - intervals are sorted as per `linearization`
-           *    - the argument's `covered` blocks have been grouped into maximally contiguous intervals,
-           *      ie. between any two intervals in the result there is a non-empty gap.
-           *    - each of the `covered` blocks in the argument is contained in some interval in the result
+          /* Return a list of pairs of intervals where the handler is active.
+           * Each interval is closed on both ends, ie. inclusive both in the left and right endpoints: [start, end].
+           * Preconditions:
+           *   - e.covered non-empty
+           * Postconditions for the result:
+           *   - always non-empty
+           *   - intervals are sorted as per `linearization`
+           *   - the argument's `covered` blocks have been grouped into maximally contiguous intervals,
+           *     ie. between any two intervals in the result there is a non-empty gap.
+           *   - each of the `covered` blocks in the argument is contained in some interval in the result
            */
           def intervals(e: ExceptionHandler): List[BlockInteval] = {
             assert(e.covered.nonEmpty, e)
@@ -2460,7 +2460,7 @@ abstract class GenASM extends SubComponent with BytecodeWriters with GenJVMASM {
           case icodes.mthdsCat =>
           def genMethodsInstr() = (instr: @unchecked) match {
 
-            /** Special handling to access native Array.clone() */
+            /* Special handling to access native Array.clone() */
             case call @ CALL_METHOD(definitions.Array_clone, Dynamic) =>
               val target: String = javaType(call.targetTypeKind).getInternalName
               jcode.invokevirtual(target, "clone", mdesc_arrayClone)
@@ -2610,7 +2610,7 @@ abstract class GenASM extends SubComponent with BytecodeWriters with GenJVMASM {
         }
       }
 
-      /**
+      /*
        * Emits one or more conversion instructions based on the types given as arguments.
        *
        * @param from The type of the value to be converted into another type.
@@ -2634,7 +2634,7 @@ abstract class GenASM extends SubComponent with BytecodeWriters with GenJVMASM {
 
         if(from == to) { return }
         // the only conversion involving BOOL that is allowed is (BOOL -> BOOL)
-        assert(from != BOOL && to != BOOL, "inconvertible types : $from -> $to")
+        assert(from != BOOL && to != BOOL, s"inconvertible types : $from -> $to")
 
         if(from.isIntSizedType) { // BYTE, CHAR, SHORT, and INT. (we're done with BOOL already)
 
@@ -2903,7 +2903,7 @@ abstract class GenASM extends SubComponent with BytecodeWriters with GenJVMASM {
                                      JAVA_LANG_OBJECT.getInternalName,
                                      EMPTY_STRING_ARRAY)
 
-      log("Dumping mirror class for '%s'".format(mirrorName))
+      log(s"Dumping mirror class for '$mirrorName'")
 
       // typestate: entering mode with valid call sequences:
       //   [ visitSource ] [ visitOuterClass ] ( visitAnnotation | visitAttribute )*
@@ -2926,8 +2926,6 @@ abstract class GenASM extends SubComponent with BytecodeWriters with GenJVMASM {
       mirrorClass.visitEnd()
       writeIfNotTooBig("" + modsym.name, mirrorName, mirrorClass, modsym)
     }
-
-
   } // end of class JMirrorBuilder
 
 
@@ -3171,7 +3169,7 @@ abstract class GenASM extends SubComponent with BytecodeWriters with GenJVMASM {
         }
       }
 
-      /**
+      /*
        * Computes a mapping from jump only block to its
        * final destination which is either a non-jump-only
        * block or, if it's in a jump-only block cycle, is
diff --git a/src/compiler/scala/tools/nsc/backend/jvm/GenJVMASM.scala b/src/compiler/scala/tools/nsc/backend/jvm/GenJVMASM.scala
index 50fd59b23f..2ad474cf3f 100644
--- a/src/compiler/scala/tools/nsc/backend/jvm/GenJVMASM.scala
+++ b/src/compiler/scala/tools/nsc/backend/jvm/GenJVMASM.scala
@@ -67,7 +67,6 @@ trait GenJVMASM {
       // Before erasure so we can identify generic mains.
       enteringErasure {
         val companion     = sym.linkedClassOfClass
-        val companionMain = companion.tpe.member(nme.main)
 
         if (hasJavaMainMethod(companion))
           failNoForwarder("companion contains its own main method")
diff --git a/src/compiler/scala/tools/nsc/backend/opt/ConstantOptimization.scala b/src/compiler/scala/tools/nsc/backend/opt/ConstantOptimization.scala
new file mode 100644
index 0000000000..7187bacb06
--- /dev/null
+++ b/src/compiler/scala/tools/nsc/backend/opt/ConstantOptimization.scala
@@ -0,0 +1,620 @@
+/* NSC -- new Scala compiler
+ * Copyright 2005-2013 LAMP/EPFL
+ * @author  James Iry
+ */
+
+package scala.tools.nsc
+package backend.opt
+
+import scala.tools.nsc.backend.icode.analysis.LubException
+import scala.annotation.tailrec
+
+/**
+ * ConstantOptimization uses abstract interpretation to approximate for
+ * each instruction what constants a variable or stack slot might hold
+ * or cannot hold. From this it will eliminate unreachable conditionals
+ * where only one branch is reachable, e.g. to eliminate unnecessary
+ * null checks.
+ *
+ * With some more work it could be extended to
+ * - cache stable values (final fields, modules) in locals 
+ * - replace the copy propagation in ClosureElilmination
+ * - fold constants
+ * - eliminate unnecessary stores and loads
+ * - propagate knowledge gathered from conditionals for further optimization
+ */
+abstract class ConstantOptimization extends SubComponent {
+  import global._
+  import icodes._
+  import icodes.opcodes._
+
+  val phaseName = "constopt"
+
+  /** Create a new phase */
+  override def newPhase(p: Phase) = new ConstantOptimizationPhase(p)
+
+  /**
+   * The constant optimization phase.
+   */
+  class ConstantOptimizationPhase(prev: Phase) extends ICodePhase(prev) {
+
+    def name = phaseName
+
+    override def apply(c: IClass) {
+      if (settings.YconstOptimization.value) {
+        val analyzer = new ConstantOptimizer
+        analyzer optimizeClass c
+      }
+    }
+  }
+
+  class ConstantOptimizer {
+    def optimizeClass(cls: IClass) {
+      log(s"Analyzing ${cls.methods.size} methods in $cls.")
+      cls.methods foreach { m =>
+        optimizeMethod(m)
+      }
+    }
+
+    def optimizeMethod(m: IMethod) {
+      if (m.hasCode) {
+        log(s"Analyzing ${m.symbol}")
+        val replacementInstructions = interpretMethod(m)
+        for (block <- m.blocks) {
+          if (replacementInstructions contains block) {
+            val instructions = replacementInstructions(block)
+            block.replaceInstruction(block.lastInstruction, instructions)
+          }
+        }
+      }
+    }
+
+    /**
+     * A single possible (or impossible) datum that can be held in Contents
+     */
+    private sealed abstract class Datum
+    /**
+     * A constant datum
+     */
+    private case class Const(c: Constant) extends Datum {
+      def isIntAssignable = c.tag >= BooleanTag && c.tag <= IntTag
+      def toInt = c.tag match {
+        case BooleanTag => if (c.booleanValue) 1 else 0
+        case _ => c.intValue
+      }
+
+      /**
+       * True if this constant would compare to other as true under primitive eq
+       */
+      override def equals(other: Any) = other match {
+        case oc @ Const(o) => (this eq oc) || (if (this.isIntAssignable && oc.isIntAssignable) this.toInt == oc.toInt else c.value == o.value)
+        case _ => false
+      }
+
+      /**
+       * Hash code consistent with equals
+       */
+      override def hashCode = if (this.isIntAssignable) this.toInt else c.hashCode
+
+    }
+    /**
+     * A datum that has been Boxed via a BOX instruction
+     */
+    private case class Boxed(c: Datum) extends Datum
+
+    /**
+     * The knowledge we have about the abstract state of one location in terms
+     * of what constants it might or cannot hold. Forms a lower
+     * lattice where lower elements in the lattice indicate less knowledge.
+     *
+     * With the following partial ordering (where '>' indicates more precise knowledge)
+     *
+     * Possible(xs) > Possible(xs + y)
+     * Possible(xs) > Impossible(ys)
+     * Impossible(xs + y) > Impossible(xs)
+     *
+     * and the following merges, which indicate merging knowledge from two paths through
+     * the code,
+     *
+     * // left must be 1 or 2, right must be 2 or 3 then we must have a 1, 2 or 3
+     * Possible(xs) merge Possible(ys) => Possible(xs union ys)
+     * 
+     * // Left says can't be 2 or 3, right says can't be 3 or 4
+     * // then it's not 3 (it could be 2 from the right or 4 from the left)
+     * Impossible(xs) merge Impossible(ys) => Impossible(xs intersect ys)
+     * 
+     * // Left says it can't be 2 or 3, right says it must be 3 or 4, then
+     * // it can't be 2 (left rules out 4 and right says 3 is possible)
+     * Impossible(xs) merge Possible(ys) => Impossible(xs -- ys)
+     * 
+     * Intuitively, Possible(empty) says that a location can't hold anything,
+     * it's uninitialized. However, Possible(empty) never appears in the code.
+     * 
+     * Conversely, Impossible(empty) says nothing is impossible, it could be
+     * anything. Impossible(empty) is given a synonym UNKNOWN and is used
+     * for, e.g., the result of an arbitrary method call.
+     */
+    private sealed abstract class Contents {
+      /**
+       * Join this Contents with another coming from another path. Join enforces
+       * the lattice structure. It is symmetrical and never moves upward in the
+       * lattice
+       */
+      final def merge(other: Contents): Contents = if (this eq other) this else (this, other) match {
+        case (Possible(possible1), Possible(possible2)) =>
+          Possible(possible1 union possible2)
+        case (Impossible(impossible1), Impossible(impossible2)) =>
+          Impossible(impossible1 intersect impossible2)
+        case (Impossible(impossible), Possible(possible)) =>
+          Impossible(impossible -- possible)
+        case (Possible(possible), Impossible(impossible)) =>
+          Impossible(impossible -- possible)
+      }
+      // TODO we could have more fine-grained knowledge, e.g. know that 0 < x < 3. But for now equality/inequality is a good start.
+      def mightEqual(other: Contents): Boolean
+      def mightNotEqual(other: Contents): Boolean
+    }
+    private def SingleImpossible(x: Datum) = new Impossible(Set(x))
+    
+    /**
+     * The location is known to have one of a set of values.
+     */
+    private case class Possible(possible: Set[Datum]) extends Contents {
+      assert(possible.nonEmpty, "Contradiction: had an empty possible set indicating an uninitialized location")
+      def mightEqual(other: Contents): Boolean = (this eq other) || (other match {
+        // two Possibles might be equal if they have any possible members in common
+        case Possible(possible2) => (possible intersect possible2).nonEmpty
+        // a possible can be equal to an impossible if the impossible doesn't rule
+        // out all the possibilities
+        case Impossible(possible2) => (possible -- possible2).nonEmpty
+      })
+      def mightNotEqual(other: Contents): Boolean = (this ne other) && (other match {
+        // two Possibles might not be equal if either has possible members that the other doesn't
+        case Possible(possible2) => (possible -- possible2).nonEmpty || (possible2 -- possible).nonEmpty
+        case Impossible(_) => true
+      })
+    }
+    private def SinglePossible(x: Datum) = new Possible(Set(x))
+
+    /**
+     * The location is known to not have any of a set of values value (e.g null).
+     */
+    private case class Impossible(impossible: Set[Datum]) extends Contents {
+      def mightEqual(other: Contents): Boolean = (this eq other) || (other match {
+        case Possible(_) => other mightEqual this
+        case _ => true
+      })
+      def mightNotEqual(other: Contents): Boolean = (this eq other) || (other match {
+        case Possible(_) => other mightNotEqual this
+        case _ => true
+      })
+    }
+
+    /**
+     * Our entire knowledge about the contents of all variables and the stack. It forms
+     * a lattice primarily driven by the lattice structure of Contents.
+     *
+     * In addition to the rules of contents, State has the following properties:
+     * - The merge of two sets of locals holds the merges of locals found in the intersection
+     * of the two sets of locals. Locals not found in a
+     * locals map are thus possibly uninitialized and attempting to load them results
+     * in an error.
+     * - The stack heights of two states must match otherwise it's an error to merge them
+     *
+     * State is immutable in order to aid in structure sharing of local maps and stacks
+     */
+    private case class State(locals: Map[Local, Contents], stack: List[Contents]) {
+      def mergeLocals(olocals: Map[Local, Contents]): Map[Local, Contents] = if (locals eq olocals) locals else Map((for {
+        key <- (locals.keySet intersect olocals.keySet).toSeq
+      } yield (key, locals(key) merge olocals(key))): _*)
+
+      def merge(other: State): State = if (this eq other) this else {
+        @tailrec def mergeStacks(l: List[Contents], r: List[Contents], out: List[Contents]): List[Contents] = (l, r) match {
+          case (Nil, Nil) => out.reverse
+          case (l, r) if l eq r => out.reverse ++ l
+          case (lhead :: ltail, rhead :: rtail) => mergeStacks(ltail, rtail, (lhead merge rhead) :: out)
+          case _ => sys.error("Mismatched stack heights")
+        }
+
+        val newLocals = mergeLocals(other.locals)
+
+        val newStack = if (stack eq other.stack) stack else mergeStacks(stack, other.stack, Nil)
+        State(newLocals, newStack)
+      }
+
+      /**
+       * Peek at the top of the stack without modifying it. Error if the stack is empty
+       */
+      def peek(n: Int): Contents = stack(n)
+      /**
+       * Push contents onto a stack
+       */
+      def push(contents: Contents): State = this copy (stack = contents :: stack)
+      /**
+       * Drop n elements from the stack
+       */
+      def drop(number: Int): State = this copy (stack = stack drop number)
+      /**
+       * Store the top of the stack into the specified local. An error if the stack
+       * is empty
+       */
+      def store(variable: Local): State = {
+        val contents = stack.head
+        val newVariables = locals + ((variable, contents))
+        new State(newVariables, stack.tail)
+      }
+      /**
+       * Load the specified local onto the top of the stack. An error the the local is uninitialized.
+       */
+      def load(variable: Local): State = {
+        val contents: Contents = locals.getOrElse(variable, sys.error(s"$variable is not initialized"))
+        push(contents)
+      }
+      /**
+       * A copy of this State with an empty stack
+       */
+      def cleanStack: State = if (stack.isEmpty) this else this copy (stack = Nil)
+    }
+
+    // some precomputed constants
+    private val NULL = Const(Constant(null: Any))
+    private val UNKNOWN = Impossible(Set.empty)
+    private val NOT_NULL = SingleImpossible(NULL)
+    private val CONST_UNIT = SinglePossible(Const(Constant(())))
+    private val CONST_FALSE = SinglePossible(Const(Constant(false)))
+    private val CONST_ZERO_BYTE = SinglePossible(Const(Constant(0: Byte)))
+    private val CONST_ZERO_SHORT = SinglePossible(Const(Constant(0: Short)))
+    private val CONST_ZERO_CHAR = SinglePossible(Const(Constant(0: Char)))
+    private val CONST_ZERO_INT = SinglePossible(Const(Constant(0: Int)))
+    private val CONST_ZERO_LONG = SinglePossible(Const(Constant(0: Long)))
+    private val CONST_ZERO_FLOAT = SinglePossible(Const(Constant(0.0f)))
+    private val CONST_ZERO_DOUBLE = SinglePossible(Const(Constant(0.0d)))
+    private val CONST_NULL = SinglePossible(NULL)
+
+    /**
+     * Given a TypeKind, figure out what '0' for it means in order to interpret CZJUMP
+     */
+    private def getZeroOf(k: TypeKind): Contents = k match {
+      case UNIT => CONST_UNIT
+      case BOOL => CONST_FALSE
+      case BYTE => CONST_ZERO_BYTE
+      case SHORT => CONST_ZERO_SHORT
+      case CHAR => CONST_ZERO_CHAR
+      case INT => CONST_ZERO_INT
+      case LONG => CONST_ZERO_LONG
+      case FLOAT => CONST_ZERO_FLOAT
+      case DOUBLE => CONST_ZERO_DOUBLE
+      case REFERENCE(_) => CONST_NULL
+      case ARRAY(_) => CONST_NULL
+      case BOXED(_) => CONST_NULL
+      case ConcatClass => abort("no zero of ConcatClass")
+    }
+
+    // normal locals can't be null, so we use null to mean the magic 'this' local
+    private val THIS_LOCAL: Local = null
+
+    /**
+     * interpret a single instruction to find its impact on the abstract state
+     */
+    private def interpretInst(in: State, inst: Instruction): State = {
+      // pop the consumed number of values off the `in` state's stack, producing a new state
+      def dropConsumed: State = in drop inst.consumed
+      
+      inst match {
+        case THIS(_) =>
+          in load THIS_LOCAL
+  
+        case CONSTANT(k) =>
+          // treat NaN as UNKNOWN because NaN must never equal NaN
+          val const = if (k.isNaN) UNKNOWN
+          else SinglePossible(Const(k))
+          in push const
+  
+        case LOAD_ARRAY_ITEM(_) | LOAD_FIELD(_, _) | CALL_PRIMITIVE(_) =>
+          dropConsumed push UNKNOWN
+
+        case LOAD_LOCAL(local) =>
+          // TODO if a local is known to hold a constant then we can replace this instruction with a push of that constant
+          in load local
+  
+        case STORE_LOCAL(local) =>
+          in store local
+  
+        case STORE_THIS(_) =>
+          // if a local is already known to have a constant and we're replacing with the same constant then we can
+          // replace this with a drop
+          in store THIS_LOCAL
+    
+        case CALL_METHOD(_, _) =>
+          // TODO we could special case implementations of equals that are known, e.g. String#equals
+          // We could turn Possible(string constants).equals(Possible(string constants) into an eq check
+          // We could turn nonConstantString.equals(constantString) into constantString.equals(nonConstantString)
+          //  and eliminate the null check that likely precedes this call
+          val initial = dropConsumed
+          (0 until inst.produced).foldLeft(initial) { case (know, _) => know push UNKNOWN }
+  
+        case BOX(_) =>
+          val value = in peek 0
+          // we simulate boxing by, um, boxing the possible/impossible contents
+          // so if we have Possible(1,2) originally then we'll end up with
+          // a Possible(Boxed(1), Boxed(2))
+          // Similarly, if we know the input is not a 0 then we'll know the
+          // output is not a Boxed(0)
+          val newValue = value match {
+            case Possible(values) => Possible(values map Boxed)
+            case Impossible(values) => Impossible(values map Boxed)
+          }
+          dropConsumed push newValue
+  
+        case UNBOX(_) =>
+          val value = in peek 0
+          val newValue = value match {
+            // if we have a Possible, then all the possibilities
+            // should themselves be Boxes. In that
+            // case we can merge them to figure out what the UNBOX will produce
+            case Possible(inners) =>
+              assert(inners.nonEmpty, "Empty possible set indicating an uninitialized location")
+              val sanitized: Set[Contents] = (inners map {
+                case Boxed(content) => SinglePossible(content)
+                case _ => UNKNOWN
+              })
+              sanitized reduce (_ merge _)
+            // if we have an impossible then the thing that's impossible
+            // should be a box. We'll unbox that to see what we get
+            case unknown@Impossible(inners) =>
+              if (inners.isEmpty) {
+                unknown
+              } else {
+                val sanitized: Set[Contents] = (inners map {
+                  case Boxed(content) => SingleImpossible(content)
+                  case _ => UNKNOWN
+                })
+                sanitized reduce (_ merge _)
+              }
+          }
+          dropConsumed push newValue
+  
+        case LOAD_MODULE(_) | NEW(_) | LOAD_EXCEPTION(_) =>
+          in push NOT_NULL
+
+        case CREATE_ARRAY(_, _) =>
+          dropConsumed push NOT_NULL
+    
+        case IS_INSTANCE(_) =>
+          // TODO IS_INSTANCE is going to be followed by a C(Z)JUMP
+          // and if IS_INSTANCE/C(Z)JUMP the branch for "true" can
+          // know that whatever was checked was not a null
+          // see the TODO on CJUMP for more information about propagating null
+          // information
+          // TODO if the top of stack is guaranteed null then we can eliminate this IS_INSTANCE check and 
+          // replace with a constant false, but how often is a knowable null checked for instanceof?
+          // TODO we could track type information and statically know to eliminate IS_INSTANCE
+          // which might be a nice win under specialization
+          dropConsumed push UNKNOWN // it's actually a Possible(true, false) but since the following instruction
+        // will be a conditional jump comparing to true or false there
+        // nothing to be gained by being more precise
+  
+        case CHECK_CAST(_) =>
+          // TODO we could track type information and statically know to eliminate CHECK_CAST
+          // but that's probably not a huge win
+          in
+  
+        case DUP(_) =>
+          val value = in peek 0
+          in push value
+  
+        case DROP(_) | MONITOR_ENTER() | MONITOR_EXIT() | STORE_ARRAY_ITEM(_) | STORE_FIELD(_, _) =>
+          dropConsumed
+
+        case SCOPE_ENTER(_) | SCOPE_EXIT(_) =>
+          in
+  
+        case JUMP(_) | CJUMP(_, _, _, _) | CZJUMP(_, _, _, _) | RETURN(_) | THROW(_) | SWITCH(_, _) =>
+          dumpClassesAndAbort("Unexpected block ending instruction: " + inst)
+      }
+    }
+    /**
+     * interpret the last instruction of a block which will be jump, a conditional branch, a throw, or a return.
+     * It will result in a map from target blocks to the input state computed for that block. It
+     * also computes a replacement list of instructions
+     */
+    private def interpretLast(in: State, inst: Instruction): (Map[BasicBlock, State], List[Instruction]) = {
+      def canSwitch(in1: Contents, tagSet: List[Int]) = {
+        in1 mightEqual Possible(tagSet.toSet map { tag: Int => Const(Constant(tag)) })
+      }
+
+      /* common code for interpreting CJUMP and CZJUMP */
+      def interpretConditional(kind: TypeKind, val1: Contents, val2: Contents, success: BasicBlock, failure: BasicBlock, cond: TestOp): (Map[BasicBlock, State], List[Instruction]) = {
+        // TODO use reaching analysis to update the state in the two branches
+        // e.g. if the comparison was checking null equality on local x
+        // then the in the success branch we know x is null and
+        // on the failure branch we know it is not
+        // in fact, with copy propagation we could propagate that knowledge
+        // back through a chain of locations
+        //
+        // TODO if we do all that we need to be careful in the
+        // case that success and failure are the same target block
+        // because we're using a Map and don't want one possible state to clobber the other
+        // alternative mayb we should just replace the conditional with a jump if both targets are the same
+
+        def mightEqual = val1 mightEqual val2
+        def mightNotEqual = val1 mightNotEqual val2
+        def guaranteedEqual = mightEqual && !mightNotEqual
+
+        def succPossible = cond match {
+          case EQ => mightEqual
+          case NE => mightNotEqual
+          case LT | GT => !guaranteedEqual // if the two are guaranteed to be equal then they can't be LT/GT
+          case LE | GE => true
+        }
+
+        def failPossible = cond match {
+          case EQ => mightNotEqual
+          case NE => mightEqual
+          case LT | GT => true
+          case LE | GE => !guaranteedEqual // if the two are guaranteed to be equal then they must be LE/GE
+        }
+
+        val out = in drop inst.consumed
+
+        var result = Map[BasicBlock, State]()
+        if (succPossible) {
+          result += ((success, out))
+        }
+
+        if (failPossible) {
+          result += ((failure, out))
+        }
+
+        val replacements = if (result.size == 1) List.fill(inst.consumed)(DROP(kind)) :+ JUMP(result.keySet.head)
+        else inst :: Nil
+        
+        (result, replacements)
+      }
+
+      inst match {
+        case JUMP(whereto) =>
+          (Map((whereto, in)), inst :: Nil)
+
+        case CJUMP(success, failure, cond, kind) =>
+          val in1 = in peek 0
+          val in2 = in peek 1
+          interpretConditional(kind, in1, in2, success, failure, cond)
+
+        case CZJUMP(success, failure, cond, kind) =>
+          val in1 = in peek 0
+          val in2 = getZeroOf(kind)
+          interpretConditional(kind, in1, in2, success, failure, cond)
+
+        case SWITCH(tags, labels) =>
+          val in1 = in peek 0
+          val newStuff = tags zip labels filter { case (tagSet, _) => canSwitch(in1, tagSet) }
+          val (reachableTags, reachableNormalLabels) = (tags zip labels filter { case (tagSet, _) => canSwitch(in1, tagSet) }).unzip
+          val reachableLabels = if (labels.lengthCompare(tags.length) > 0) {
+            // if we've got an extra label then it's the default
+            val defaultLabel = labels.last
+            // see if the default is reachable by seeing if the input might be out of the set
+            // of all tags
+            val allTags = Possible(tags.flatten.toSet map { tag: Int => Const(Constant(tag)) })
+            if (in1 mightNotEqual allTags) {
+              reachableNormalLabels :+ defaultLabel
+            } else {
+              reachableNormalLabels
+            }
+          } else {
+            reachableNormalLabels
+          }
+          // TODO similar to the comment in interpretConditional, we should update our the State going into each
+          // branch based on which tag is being matched. Also, just like interpretConditional, if target blocks
+          // are the same we need to merge State rather than clobber
+
+          // alternative, maybe we should simplify the SWITCH to not have same target labels
+          val newState = in drop inst.consumed
+          val result = Map(reachableLabels map { label => (label, newState) }: _*)
+          if (reachableLabels.size == 1) (result, DROP(INT) :: JUMP(reachableLabels.head) :: Nil)
+          else (result, inst :: Nil)
+
+        // these instructions don't have target blocks
+        // (exceptions are assumed to be reachable from all instructions)
+        case RETURN(_) | THROW(_) =>
+          (Map.empty, inst :: Nil)
+
+        case _ =>
+          dumpClassesAndAbort("Unexpected non-block ending instruction: " + inst)
+      }
+    }
+
+    /**
+     * Analyze a single block to find how it transforms an input state into a states for its successor blocks
+     * Also computes a list of instructions to be used to replace its last instruction
+     */
+    private def interpretBlock(in: State, block: BasicBlock): (Map[BasicBlock, State], Map[BasicBlock, State], List[Instruction]) = {
+      debuglog(s"interpreting block $block")
+      // number of instructions excluding the last one
+      val normalCount = block.size - 1
+
+      var exceptionState = in.cleanStack
+      var normalExitState = in
+      var idx = 0
+      while (idx < normalCount) {
+        val inst = block(idx)
+        normalExitState = interpretInst(normalExitState, inst)
+        if (normalExitState.locals ne exceptionState.locals)
+          exceptionState.copy(locals = exceptionState mergeLocals normalExitState.locals)
+        idx += 1
+      }
+
+      val pairs = block.exceptionSuccessors map { b => (b, exceptionState) }
+      val exceptionMap = Map(pairs: _*)
+
+      val (normalExitMap, newInstructions) = interpretLast(normalExitState, block.lastInstruction)
+
+      (normalExitMap, exceptionMap, newInstructions)
+    }
+
+    /**
+     * Analyze a single method to find replacement instructions
+     */
+    private def interpretMethod(m: IMethod): Map[BasicBlock, List[Instruction]] = {
+      import scala.collection.mutable.{ Set => MSet, Map => MMap }
+
+      debuglog(s"interpreting method $m")
+      var iterations = 0
+
+      // initially we know that 'this' is not null and the params are initialized to some unknown value
+      val initThis: Iterator[(Local, Contents)] = if (m.isStatic) Iterator.empty else Iterator.single((THIS_LOCAL, NOT_NULL))
+      val initOtherLocals: Iterator[(Local, Contents)] = m.params.iterator map { param => (param, UNKNOWN) }
+      val initialLocals: Map[Local, Contents] = Map((initThis ++ initOtherLocals).toSeq: _*)
+      val initialState = State(initialLocals, Nil)
+
+      // worklist of basic blocks to process, initially the start block
+      val worklist = MSet(m.startBlock)
+      // worklist of exception basic blocks. They're kept in a separate set so they can be 
+      // processed after normal flow basic blocks. That's because exception basic blocks
+      // are more likely to have multiple predecessors and queueing them for later
+      // increases the chances that they'll only need to be interpreted once
+      val exceptionlist = MSet[BasicBlock]()
+      // our current best guess at what the input state is for each block
+      // initially we only know about the start block
+      val inputState = MMap[BasicBlock, State]((m.startBlock, initialState))
+
+      // update the inputState map based on new information from interpreting a block
+      // When the input state of a block changes, add it back to the work list to be
+      // reinterpreted
+      def updateInputStates(outputStates: Map[BasicBlock, State], worklist: MSet[BasicBlock]) {
+        for ((block, newState) <- outputStates) {
+          val oldState = inputState get block
+          val updatedState = oldState map (x => x merge newState) getOrElse newState
+          if (oldState != Some(updatedState)) {
+            worklist add block
+            inputState(block) = updatedState
+          }
+        }
+      }
+
+      // the instructions to be used as the last instructions on each block
+      val replacements = MMap[BasicBlock, List[Instruction]]()
+
+      while (worklist.nonEmpty || exceptionlist.nonEmpty) {
+        if (worklist.isEmpty) {
+          // once the worklist is empty, start processing exception blocks
+          val block = exceptionlist.head
+          exceptionlist remove block
+          worklist add block
+        } else {
+          iterations += 1
+          val block = worklist.head
+          worklist remove block
+          val (normalExitMap, exceptionMap, newInstructions) = interpretBlock(inputState(block), block)
+
+          updateInputStates(normalExitMap, worklist)
+          updateInputStates(exceptionMap, exceptionlist)
+          replacements(block) = newInstructions
+        }
+      }
+
+      debuglog(s"method $m with ${m.blocks.size} reached fixpoint in $iterations iterations")
+      replacements.toMap
+    }
+  }
+}
diff --git a/src/compiler/scala/tools/nsc/backend/opt/DeadCodeElimination.scala b/src/compiler/scala/tools/nsc/backend/opt/DeadCodeElimination.scala
index a9c8104e79..7042d7a042 100644
--- a/src/compiler/scala/tools/nsc/backend/opt/DeadCodeElimination.scala
+++ b/src/compiler/scala/tools/nsc/backend/opt/DeadCodeElimination.scala
@@ -218,7 +218,7 @@ abstract class DeadCodeElimination extends SubComponent {
         // worklist so we also mark their reaching defs as useful - see SI-7060
         if (!useful(bb)(idx)) {
           useful(bb) += idx
-          dropOf.get(bb, idx) foreach {
+          dropOf.get((bb, idx)) foreach {
             for ((bb1, idx1) <- _) {
               /*
                * SI-7060: A drop that we now mark as useful can be reached via several paths,
@@ -346,7 +346,7 @@ abstract class DeadCodeElimination extends SubComponent {
           if (useful(bb)(idx)) {
             debuglog(" * " + i + " is useful")
             bb.emit(i, i.pos)
-            compensations.get(bb, idx) match {
+            compensations.get((bb, idx)) match {
               case Some(is) => is foreach bb.emit
               case None => ()
             }
diff --git a/src/compiler/scala/tools/nsc/backend/opt/Inliners.scala b/src/compiler/scala/tools/nsc/backend/opt/Inliners.scala
index 1a73764719..38040d921f 100644
--- a/src/compiler/scala/tools/nsc/backend/opt/Inliners.scala
+++ b/src/compiler/scala/tools/nsc/backend/opt/Inliners.scala
@@ -342,7 +342,7 @@ abstract class Inliners extends SubComponent {
         inlineWithoutTFA(inputBlocks, callsites)
       }
 
-      /**
+      /*
        *  Inline straightforward callsites (those that can be inlined without a TFA).
        *
        *  To perform inlining, all we need to know is listed as formal params in `analyzeInc()`:
@@ -372,7 +372,7 @@ abstract class Inliners extends SubComponent {
         inlineCount
       }
 
-      /**
+      /*
        *  Decides whether it's feasible and desirable to inline the body of the method given by `concreteMethod`
        *  at the program point given by `i` (a callsite). The boolean result indicates whether inlining was performed.
        *
@@ -788,7 +788,7 @@ abstract class Inliners extends SubComponent {
 
         val varsInScope = mutable.HashSet[Local]() ++= block.varsInScope
 
-        /** Side effects varsInScope when it sees SCOPE_ENTERs. */
+        /* Side effects varsInScope when it sees SCOPE_ENTERs. */
         def instrBeforeFilter(i: Instruction): Boolean = {
           i match { case SCOPE_ENTER(l) => varsInScope += l ; case _ => () }
           i ne instr
@@ -801,7 +801,7 @@ abstract class Inliners extends SubComponent {
         // store the '$this' into the special local
         val inlinedThis = newLocal("$inlThis", REFERENCE(ObjectClass))
 
-        /** buffer for the returned value */
+        /* buffer for the returned value */
         val retVal = inc.m.returnType match {
           case UNIT  => null
           case x     => newLocal("$retVal", x)
@@ -809,7 +809,7 @@ abstract class Inliners extends SubComponent {
 
         val inlinedLocals = mutable.HashMap.empty[Local, Local]
 
-        /** Add a new block in the current context. */
+        /* Add a new block in the current context. */
         def newBlock() = {
           val b = caller.m.code.newBlock()
           activeHandlers foreach (_ addCoveredBlock b)
@@ -826,7 +826,7 @@ abstract class Inliners extends SubComponent {
           handler
         }
 
-        /** alfa-rename `l` in caller's context. */
+        /* alfa-rename `l` in caller's context. */
         def dupLocal(l: Local): Local = {
           val sym = caller.sym.newVariable(freshName(l.sym.name.toString), l.sym.pos)
           // sym.setInfo(l.sym.tpe)
@@ -837,10 +837,10 @@ abstract class Inliners extends SubComponent {
 
         val afterBlock = newBlock()
 
-        /** Map from nw.init instructions to their matching NEW call */
+        /* Map from nw.init instructions to their matching NEW call */
         val pending: mutable.Map[Instruction, NEW] = new mutable.HashMap
 
-        /** Map an instruction from the callee to one suitable for the caller. */
+        /* Map an instruction from the callee to one suitable for the caller. */
         def map(i: Instruction): Instruction = {
           def assertLocal(l: Local) = {
             assert(caller.locals contains l, "Could not find local '" + l + "' in locals, nor in inlinedLocals: " + inlinedLocals)
diff --git a/src/compiler/scala/tools/nsc/plugins/Plugins.scala b/src/compiler/scala/tools/nsc/plugins/Plugins.scala
index 00e5875852..71b97e86a6 100644
--- a/src/compiler/scala/tools/nsc/plugins/Plugins.scala
+++ b/src/compiler/scala/tools/nsc/plugins/Plugins.scala
@@ -79,11 +79,11 @@ trait Plugins {
 
     val plugs = pick(roughPluginsList, Set(), (phasesSet map (_.phaseName)).toSet)
 
-    /** Verify requirements are present. */
+    /* Verify requirements are present. */
     for (req <- settings.require.value ; if !(plugs exists (_.name == req)))
       globalError("Missing required plugin: " + req)
 
-    /** Process plugin options. */
+    /* Process plugin options. */
     def namec(plug: Plugin) = plug.name + ":"
     def optList(xs: List[String], p: Plugin) = xs filter (_ startsWith namec(p))
     def doOpts(p: Plugin): List[String] =
@@ -95,7 +95,7 @@ trait Plugins {
         p.processOptions(opts, globalError)
     }
 
-    /** Verify no non-existent plugin given with -P */
+    /* Verify no non-existent plugin given with -P */
     for (opt <- settings.pluginOptions.value ; if plugs forall (p => optList(List(opt), p).isEmpty))
       globalError("bad option: -P:" + opt)
 
diff --git a/src/compiler/scala/tools/nsc/settings/MutableSettings.scala b/src/compiler/scala/tools/nsc/settings/MutableSettings.scala
index cc77cbdf52..4d086e787e 100644
--- a/src/compiler/scala/tools/nsc/settings/MutableSettings.scala
+++ b/src/compiler/scala/tools/nsc/settings/MutableSettings.scala
@@ -486,8 +486,6 @@ class MutableSettings(val errorFn: String => Unit)
     descr: String,
     default: ScalaVersion)
   extends Setting(name, descr) {
-    import ScalaVersion._
-    
     type T = ScalaVersion
     protected var v: T = NoScalaVersion
 
@@ -495,14 +493,14 @@ class MutableSettings(val errorFn: String => Unit)
       value = default
       Some(args)
     }
-    
+
     override def tryToSetColon(args: List[String]) = args match {
       case Nil      => value = default; Some(Nil)
       case x :: xs  => value = ScalaVersion(x, errorFn) ; Some(xs)
     }
-    
+
     override def tryToSetFromPropertyValue(s: String) = tryToSet(List(s))
-    
+
     def unparse: List[String] = if (value == NoScalaVersion) Nil else List(s"${name}:${value.unparse}")
 
     withHelpSyntax(s"${name}:<${arg}>")
diff --git a/src/compiler/scala/tools/nsc/settings/ScalaSettings.scala b/src/compiler/scala/tools/nsc/settings/ScalaSettings.scala
index 9469113238..ee9a3aed2a 100644
--- a/src/compiler/scala/tools/nsc/settings/ScalaSettings.scala
+++ b/src/compiler/scala/tools/nsc/settings/ScalaSettings.scala
@@ -38,7 +38,7 @@ trait ScalaSettings extends AbsScalaSettings
   protected def futureSettings = List[BooleanSetting]()
 
   /** Enabled under -optimise. */
-  protected def optimiseSettings = List[BooleanSetting](inline, inlineHandlers, Xcloselim, Xdce)
+  protected def optimiseSettings = List[BooleanSetting](inline, inlineHandlers, Xcloselim, Xdce, YconstOptimization)
 
   /** Internal use - syntax enhancements. */
   private class EnableSettings[T <: BooleanSetting](val s: T) {
@@ -128,6 +128,7 @@ trait ScalaSettings extends AbsScalaSettings
   val check           = PhasesSetting     ("-Ycheck", "Check the tree at the end of")
   val Yshow           = PhasesSetting     ("-Yshow", "(Requires -Xshow-class or -Xshow-object) Show after")
   val Xcloselim       = BooleanSetting    ("-Yclosure-elim", "Perform closure elimination.")
+  val YconstOptimization  = BooleanSetting    ("-Yconst-opt", "Perform optimization with constant values.")
   val Ycompacttrees   = BooleanSetting    ("-Ycompact-trees", "Use compact tree printer when displaying trees.")
   val noCompletion    = BooleanSetting    ("-Yno-completion", "Disable tab-completion in the REPL.")
   val Xdce            = BooleanSetting    ("-Ydead-code", "Perform dead code elimination.")
@@ -166,7 +167,6 @@ trait ScalaSettings extends AbsScalaSettings
   val Yreifycopypaste = BooleanSetting    ("-Yreify-copypaste", "Dump the reified trees in copypasteable representation.")
   val Yreplsync       = BooleanSetting    ("-Yrepl-sync", "Do not use asynchronous code for repl startup")
   val Yreploutdir     = StringSetting     ("-Yrepl-outdir", "path", "Write repl-generated classfiles to given output directory (use \"\" to generate a temporary dir)" , "")
-  val Ynotnull        = BooleanSetting    ("-Ynotnull", "Enable (experimental and incomplete) scala.NotNull.")
   val YmethodInfer    = BooleanSetting    ("-Yinfer-argument-types", "Infer types for arguments of overriden methods.")
   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.").
                                           withDeprecationMessage("This flag is scheduled for removal in 2.12. If you have a case where you need this flag then please report a bug.")
diff --git a/src/compiler/scala/tools/nsc/settings/Warnings.scala b/src/compiler/scala/tools/nsc/settings/Warnings.scala
index 2649a150ad..791d44153c 100644
--- a/src/compiler/scala/tools/nsc/settings/Warnings.scala
+++ b/src/compiler/scala/tools/nsc/settings/Warnings.scala
@@ -19,7 +19,6 @@ trait Warnings {
   // present form, but have the potential to offer useful info.
   protected def allWarnings = lintWarnings ++ List(
     warnDeadCode,
-    warnSelectNullable,
     warnValueDiscard,
     warnNumericWiden
   )
@@ -46,21 +45,20 @@ trait Warnings {
       allWarnings foreach (_.value = true)
     }
   )
+  private lazy val warnSelectNullable = BooleanSetting("-Xcheck-null", "This option is obsolete and does nothing.")
 
   // Individual warnings.
-  val warnSelectNullable   = BooleanSetting   ("-Xcheck-null", "Warn upon selection of nullable reference.")
   val warnAdaptedArgs      = BooleanSetting   ("-Ywarn-adapted-args", "Warn if an argument list is modified to match the receiver.")
   val warnDeadCode         = BooleanSetting   ("-Ywarn-dead-code", "Warn when dead code is identified.")
   val warnValueDiscard     = BooleanSetting   ("-Ywarn-value-discard", "Warn when non-Unit expression results are unused.")
   val warnNumericWiden     = BooleanSetting   ("-Ywarn-numeric-widen", "Warn when numerics are widened.")
   val warnNullaryUnit      = BooleanSetting   ("-Ywarn-nullary-unit", "Warn when nullary methods return Unit.")
   val warnInaccessible     = BooleanSetting   ("-Ywarn-inaccessible", "Warn about inaccessible types in method signatures.")
-  val warnNullaryOverride  = BooleanSetting   ("-Ywarn-nullary-override",
-    "Warn when non-nullary overrides nullary, e.g. `def foo()` over `def foo`.")
+  val warnNullaryOverride  = BooleanSetting   ("-Ywarn-nullary-override", "Warn when non-nullary overrides nullary, e.g. `def foo()` over `def foo`.")
   val warnInferAny         = BooleanSetting   ("-Ywarn-infer-any", "Warn when a type argument is inferred to be `Any`.")
 
   // Backward compatibility.
-  @deprecated("Use fatalWarnings", "2.11.0") def Xwarnfatal      = fatalWarnings         // used by sbt
-  @deprecated("Use warnSelectNullable", "2.11.0") def Xchecknull = warnSelectNullable    // used by ide
-  @deprecated("Use warnDeadCode", "2.11.0") def Ywarndeadcode    = warnDeadCode          // used by ide
+  @deprecated("Use fatalWarnings", "2.11.0") def Xwarnfatal            = fatalWarnings      // used by sbt
+  @deprecated("This option is being removed", "2.11.0") def Xchecknull = warnSelectNullable // used by ide
+  @deprecated("Use warnDeadCode", "2.11.0") def Ywarndeadcode          = warnDeadCode       // used by ide
 }
diff --git a/src/compiler/scala/tools/nsc/symtab/classfile/ClassfileParser.scala b/src/compiler/scala/tools/nsc/symtab/classfile/ClassfileParser.scala
index f8930c4ddd..d26a61f187 100644
--- a/src/compiler/scala/tools/nsc/symtab/classfile/ClassfileParser.scala
+++ b/src/compiler/scala/tools/nsc/symtab/classfile/ClassfileParser.scala
@@ -503,8 +503,8 @@ abstract class ClassfileParser {
     val nameIdx      = in.nextChar
     currentClass     = pool.getClassName(nameIdx)
 
-    /** Parse parents for Java classes. For Scala, return AnyRef, since the real type will be unpickled.
-     *  Updates the read pointer of 'in'. */
+    /* Parse parents for Java classes. For Scala, return AnyRef, since the real type will be unpickled.
+     * Updates the read pointer of 'in'. */
     def parseParents: List[Type] = {
       if (isScala) {
         in.nextChar              // skip superclass
@@ -984,8 +984,8 @@ abstract class ClassfileParser {
       Some(ScalaSigBytes(pool.getBytes(entries.toList)))
     }
 
-    /** Parse and return a single annotation.  If it is malformed,
-     *  return None.
+    /* Parse and return a single annotation.  If it is malformed,
+     * return None.
      */
     def parseAnnotation(attrNameIndex: Char): Option[AnnotationInfo] = try {
       val attrType = pool.getType(attrNameIndex)
@@ -1030,7 +1030,7 @@ abstract class ClassfileParser {
         None // ignore malformed annotations
     }
 
-    /**
+    /*
      * Parse the "Exceptions" attribute which denotes the exceptions
      * thrown by a method.
      */
@@ -1046,8 +1046,8 @@ abstract class ClassfileParser {
       }
     }
 
-    /** Parse a sequence of annotations and attaches them to the
-     *  current symbol sym, except for the ScalaSignature annotation that it returns, if it is available. */
+    /* Parse a sequence of annotations and attaches them to the
+     * current symbol sym, except for the ScalaSignature annotation that it returns, if it is available. */
     def parseAnnotations(len: Int): Option[AnnotationInfo] =  {
       val nAttr = in.nextChar
       var scalaSigAnnot: Option[AnnotationInfo] = None
@@ -1173,7 +1173,7 @@ abstract class ClassfileParser {
      *  If the given name is not an inner class, it returns the symbol found in `definitions`.
      */
     def classSymbol(externalName: Name): Symbol = {
-      /** Return the symbol of `innerName`, having the given `externalName`. */
+      /* Return the symbol of `innerName`, having the given `externalName`. */
       def innerSymbol(externalName: Name, innerName: Name, static: Boolean): Symbol = {
         def getMember(sym: Symbol, name: Name): Symbol =
           if (static)
diff --git a/src/compiler/scala/tools/nsc/symtab/classfile/ICodeReader.scala b/src/compiler/scala/tools/nsc/symtab/classfile/ICodeReader.scala
index 7010c9e20a..86f034223d 100644
--- a/src/compiler/scala/tools/nsc/symtab/classfile/ICodeReader.scala
+++ b/src/compiler/scala/tools/nsc/symtab/classfile/ICodeReader.scala
@@ -197,7 +197,7 @@ abstract class ICodeReader extends ClassfileParser {
       import code._
       var size = 1 // instruction size
 
-      /** Parse 16 bit jump target. */
+      /* Parse 16 bit jump target. */
       def parseJumpTarget = {
         size += 2
         val offset = in.nextChar.toShort
@@ -206,7 +206,7 @@ abstract class ICodeReader extends ClassfileParser {
         target
       }
 
-      /** Parse 32 bit jump target. */
+      /* Parse 32 bit jump target. */
       def parseJumpTargetW: Int = {
         size += 4
         val offset = in.nextInt
diff --git a/src/compiler/scala/tools/nsc/symtab/classfile/Pickler.scala b/src/compiler/scala/tools/nsc/symtab/classfile/Pickler.scala
index 140be0e17b..9217bbeeb8 100644
--- a/src/compiler/scala/tools/nsc/symtab/classfile/Pickler.scala
+++ b/src/compiler/scala/tools/nsc/symtab/classfile/Pickler.scala
@@ -222,7 +222,7 @@ abstract class Pickler extends SubComponent {
         case NullaryMethodType(restpe) =>
           putType(restpe)
         case PolyType(tparams, restpe) =>
-          /** no longer needed since all params are now local
+          /* no longer needed since all params are now local
           tparams foreach { tparam =>
             if (!isLocal(tparam)) locals += tparam // similar to existential types, these tparams are local
           }
@@ -528,7 +528,7 @@ abstract class Pickler extends SubComponent {
     private def writeSymInfo(sym: Symbol) {
       writeRef(sym.name)
       writeRef(localizedOwner(sym))
-      writeLongNat((rawToPickledFlags(sym.flags & PickledFlags)))
+      writeLongNat((rawToPickledFlags(sym.rawflags & PickledFlags)))
       if (sym.hasAccessBoundary) writeRef(sym.privateWithin)
       writeRef(sym.info)
     }
diff --git a/src/compiler/scala/tools/nsc/transform/AddInterfaces.scala b/src/compiler/scala/tools/nsc/transform/AddInterfaces.scala
index 5fbc15f858..ba75f40a3a 100644
--- a/src/compiler/scala/tools/nsc/transform/AddInterfaces.scala
+++ b/src/compiler/scala/tools/nsc/transform/AddInterfaces.scala
@@ -174,8 +174,8 @@ abstract class AddInterfaces extends InfoTransform { self: Erasure =>
     override def complete(implSym: Symbol) {
       debuglog("LazyImplClassType completing " + implSym)
 
-      /** If `tp` refers to a non-interface trait, return a
-       *  reference to its implementation class. Otherwise return `tp`.
+      /* If `tp` refers to a non-interface trait, return a
+       * reference to its implementation class. Otherwise return `tp`.
        */
       def mixinToImplClass(tp: Type): Type = AddInterfaces.this.erasure(implSym) {
         tp match { //@MATN: no normalize needed (comes after erasure)
@@ -276,7 +276,7 @@ abstract class AddInterfaces extends InfoTransform { self: Erasure =>
    */
   private def addMixinConstructorDef(clazz: Symbol, stats: List[Tree]): List[Tree] =
     if (treeInfo.firstConstructor(stats) != EmptyTree) stats
-    else DefDef(clazz.primaryConstructor, Block(List(), Literal(Constant()))) :: stats
+    else DefDef(clazz.primaryConstructor, Block(List(), Literal(Constant(())))) :: stats
 
   private def implTemplate(clazz: Symbol, templ: Template): Template = atPos(templ.pos) {
     val templ1 = (
diff --git a/src/compiler/scala/tools/nsc/transform/CleanUp.scala b/src/compiler/scala/tools/nsc/transform/CleanUp.scala
index a871c72fc2..3b9cee2d88 100644
--- a/src/compiler/scala/tools/nsc/transform/CleanUp.scala
+++ b/src/compiler/scala/tools/nsc/transform/CleanUp.scala
@@ -351,7 +351,7 @@ abstract class CleanUp extends Transform with ast.TreeDSL {
               else if (resultSym == ObjectClass) tree                                     // no cast necessary
               else gen.mkCast(tree, boxedResType)                                         // cast to expected type
 
-            /** Normal non-Array call */
+            /* Normal non-Array call */
             def genDefaultCall = {
               // reflective method call machinery
               val invokeName  = MethodClass.tpe member nme.invoke_                                  // scala.reflect.Method.invoke(...)
@@ -369,7 +369,7 @@ abstract class CleanUp extends Transform with ast.TreeDSL {
               fixResult(TRY (invocation) CATCH { CASE (catchVar) ==> catchBody } ENDTRY)
             }
 
-            /** A possible primitive method call, represented by methods in BoxesRunTime. */
+            /* A possible primitive method call, represented by methods in BoxesRunTime. */
             def genValueCall(operator: Symbol) = fixResult(REF(operator) APPLY args)
             def genValueCallWithTest = {
               getPrimitiveReplacementForStructuralCall(methSym.name) match {
@@ -380,7 +380,7 @@ abstract class CleanUp extends Transform with ast.TreeDSL {
               }
             }
 
-            /** A native Array call. */
+            /* A native Array call. */
             def genArrayCall = fixResult(
               methSym.name match {
                 case nme.length => REF(boxMethod(IntClass)) APPLY (REF(arrayLengthMethod) APPLY args)
@@ -391,9 +391,9 @@ abstract class CleanUp extends Transform with ast.TreeDSL {
               mustBeUnit = methSym.name == nme.update
             )
 
-            /** A conditional Array call, when we can't determine statically if the argument is
-             *  an Array, but the structural type method signature is consistent with an Array method
-             *  so we have to generate both kinds of code.
+            /* A conditional Array call, when we can't determine statically if the argument is
+             * an Array, but the structural type method signature is consistent with an Array method
+             * so we have to generate both kinds of code.
              */
             def genArrayCallWithTest =
               IF ((qual1() GETCLASS()) DOT nme.isArray) THEN genArrayCall ELSE genDefaultCall
diff --git a/src/compiler/scala/tools/nsc/transform/Constructors.scala b/src/compiler/scala/tools/nsc/transform/Constructors.scala
index a4a6c3ff31..768c9b6989 100644
--- a/src/compiler/scala/tools/nsc/transform/Constructors.scala
+++ b/src/compiler/scala/tools/nsc/transform/Constructors.scala
@@ -34,6 +34,41 @@ abstract class Constructors extends Transform with ast.TreeDSL {
       val stats = impl.body          // the transformed template body
       val localTyper = typer.atOwner(impl, clazz)
 
+      // Inspect for obvious out-of-order initialization; concrete, eager vals or vars,
+      // declared in this class, for which a reference to the member precedes its definition.
+      def checkableForInit(sym: Symbol) = (
+           (sym ne null)
+        && (sym.isVal || sym.isVar)
+        && !(sym hasFlag LAZY | DEFERRED | SYNTHETIC)
+      )
+      val uninitializedVals = mutable.Set[Symbol](
+        stats collect { case vd: ValDef if checkableForInit(vd.symbol) => vd.symbol.accessedOrSelf }: _*
+      )
+      if (uninitializedVals.nonEmpty)
+        log("Checking constructor for init order issues among: " + uninitializedVals.map(_.name).mkString(", "))
+
+      for (stat <- stats) {
+        // Checking the qualifier symbol is necessary to prevent a selection on
+        // another instance of the same class from potentially appearing to be a forward
+        // reference on the member in the current class.
+        def check(tree: Tree) = {
+          for (t <- tree) t match {
+            case t: RefTree if uninitializedVals(t.symbol.accessedOrSelf) && t.qualifier.symbol == clazz =>
+              unit.warning(t.pos, s"Reference to uninitialized ${t.symbol.accessedOrSelf}")
+            case _ =>
+          }
+        }
+        stat match {
+          case vd: ValDef      =>
+            // doing this first allows self-referential vals, which to be a conservative
+            // warner we will do because it's possible though difficult for it to be useful.
+            uninitializedVals -= vd.symbol.accessedOrSelf
+            if (!vd.symbol.isLazy)
+              check(vd.rhs)
+          case _: MemberDef    => // skip other member defs
+          case t               => check(t) // constructor body statement
+        }
+      }
       val specializedFlag: Symbol = clazz.info.decl(nme.SPECIALIZED_INSTANCE)
       val shouldGuard = (specializedFlag != NoSymbol) && !clazz.hasFlag(SPECIALIZED)
 
@@ -268,10 +303,10 @@ abstract class Constructors extends Transform with ast.TreeDSL {
         copyParam(acc, parameter(acc))
       }
 
-      /** Return a single list of statements, merging the generic class constructor with the
-       *  specialized stats. The original statements are retyped in the current class, and
-       *  assignments to generic fields that have a corresponding specialized assignment in
-       *  `specializedStats` are replaced by the specialized assignment.
+      /* Return a single list of statements, merging the generic class constructor with the
+       * specialized stats. The original statements are retyped in the current class, and
+       * assignments to generic fields that have a corresponding specialized assignment in
+       * `specializedStats` are replaced by the specialized assignment.
        */
       def mergeConstructors(genericClazz: Symbol, originalStats: List[Tree], specializedStats: List[Tree]): List[Tree] = {
         val specBuf = new ListBuffer[Tree]
@@ -286,10 +321,10 @@ abstract class Constructors extends Transform with ast.TreeDSL {
             case _ => false
           }
 
-        /** Rewrite calls to ScalaRunTime.array_update to the proper apply method in scala.Array.
-         *  Erasure transforms Array.update to ScalaRunTime.update when the element type is a type
-         *  variable, but after specialization this is a concrete primitive type, so it would
-         *  be an error to pass it to array_update(.., .., Object).
+        /* Rewrite calls to ScalaRunTime.array_update to the proper apply method in scala.Array.
+         * Erasure transforms Array.update to ScalaRunTime.update when the element type is a type
+         * variable, but after specialization this is a concrete primitive type, so it would
+         * be an error to pass it to array_update(.., .., Object).
          */
         def rewriteArrayUpdate(tree: Tree): Tree = {
           val adapter = new Transformer {
@@ -338,14 +373,14 @@ abstract class Constructors extends Transform with ast.TreeDSL {
         res
       }
 
-      /** Add an 'if' around the statements coming after the super constructor. This
-       *  guard is necessary if the code uses specialized fields. A specialized field is
-       *  initialized in the subclass constructor, but the accessors are (already) overridden
-       *  and pointing to the (empty) fields. To fix this, a class with specialized fields
-       *  will not run its constructor statements if the instance is specialized. The specialized
-       *  subclass includes a copy of those constructor statements, and runs them. To flag that a class
-       *  has specialized fields, and their initialization should be deferred to the subclass, method
-       *  'specInstance$' is added in phase specialize.
+      /* Add an 'if' around the statements coming after the super constructor. This
+       * guard is necessary if the code uses specialized fields. A specialized field is
+       * initialized in the subclass constructor, but the accessors are (already) overridden
+       * and pointing to the (empty) fields. To fix this, a class with specialized fields
+       * will not run its constructor statements if the instance is specialized. The specialized
+       * subclass includes a copy of those constructor statements, and runs them. To flag that a class
+       * has specialized fields, and their initialization should be deferred to the subclass, method
+       * 'specInstance$' is added in phase specialize.
        */
       def guardSpecializedInitializer(stats: List[Tree]): List[Tree] = if (settings.nospecialization.value) stats else {
         // split the statements in presuper and postsuper
@@ -366,7 +401,7 @@ abstract class Constructors extends Transform with ast.TreeDSL {
                 CODE.NOT (
                  Apply(gen.mkAttributedRef(specializedFlag), List())),
                 List()),
-              Block(stats, Literal(Constant())),
+              Block(stats, Literal(Constant(()))),
               EmptyTree)
 
           List(localTyper.typed(tree))
@@ -390,8 +425,7 @@ abstract class Constructors extends Transform with ast.TreeDSL {
       }
 */
 
-      /** Create a getter or a setter and enter into `clazz` scope
-       */
+      /* Create a getter or a setter and enter into `clazz` scope */
       def addAccessor(sym: Symbol, name: TermName, flags: Long) = {
         val m = clazz.newMethod(name, sym.pos, flags & ~(LOCAL | PRIVATE)) setPrivateWithin clazz
         clazz.info.decls enter m
@@ -520,7 +554,7 @@ abstract class Constructors extends Transform with ast.TreeDSL {
         gen.mkMethodCall(This(clazz), delayedInitMethod, Nil, List(New(closure.symbol.tpe, This(clazz))))
       }
 
-      /** Return a pair consisting of (all statements up to and including superclass and trait constr calls, rest) */
+      /* Return a pair consisting of (all statements up to and including superclass and trait constr calls, rest) */
       def splitAtSuper(stats: List[Tree]) = {
         def isConstr(tree: Tree) = (tree.symbol ne null) && tree.symbol.isConstructor
         val (pre, rest0) = stats span (!isConstr(_))
@@ -531,12 +565,12 @@ abstract class Constructors extends Transform with ast.TreeDSL {
       val (uptoSuperStats, remainingConstrStats0) = splitAtSuper(constrStatBuf.toList)
       var remainingConstrStats = remainingConstrStats0
 
-      /** XXX This is not corect: remainingConstrStats.nonEmpty excludes too much,
-       *  but excluding it includes too much.  The constructor sequence being mimicked
-       *  needs to be reproduced with total fidelity.
+      /* XXX This is not corect: remainingConstrStats.nonEmpty excludes too much,
+       * but excluding it includes too much.  The constructor sequence being mimicked
+       * needs to be reproduced with total fidelity.
        *
-       *  See test case files/run/bug4680.scala, the output of which is wrong in many
-       *  particulars.
+       * See test case files/run/bug4680.scala, the output of which is wrong in many
+       * particulars.
        */
       val needsDelayedInit =
         (clazz isSubClass DelayedInitClass) /*&& !(defBuf exists isInitDef)*/ && remainingConstrStats.nonEmpty
diff --git a/src/compiler/scala/tools/nsc/transform/Erasure.scala b/src/compiler/scala/tools/nsc/transform/Erasure.scala
index 55b9ce1be9..857c01c49a 100644
--- a/src/compiler/scala/tools/nsc/transform/Erasure.scala
+++ b/src/compiler/scala/tools/nsc/transform/Erasure.scala
@@ -21,7 +21,6 @@ abstract class Erasure extends AddInterfaces
   import global._
   import definitions._
   import CODE._
-  import treeInfo._
 
   val phaseName: String = "erasure"
 
@@ -559,11 +558,11 @@ abstract class Erasure extends AddInterfaces
           case x          =>
             assert(x != ArrayClass)
             tree match {
-              /** Can't always remove a Box(Unbox(x)) combination because the process of boxing x
-               *  may lead to throwing an exception.
+              /* Can't always remove a Box(Unbox(x)) combination because the process of boxing x
+               * may lead to throwing an exception.
                *
-               *  This is important for specialization: calls to the super constructor should not box/unbox specialized
-               *  fields (see TupleX). (ID)
+               * This is important for specialization: calls to the super constructor should not box/unbox specialized
+               * fields (see TupleX). (ID)
                */
               case Apply(boxFun, List(arg)) if isSafelyRemovableUnbox(tree, arg) =>
                 log(s"boxing an unbox: ${tree.symbol} -> ${arg.tpe}")
diff --git a/src/compiler/scala/tools/nsc/transform/InlineErasure.scala b/src/compiler/scala/tools/nsc/transform/InlineErasure.scala
index 83dbc23014..1bbe1b8410 100644
--- a/src/compiler/scala/tools/nsc/transform/InlineErasure.scala
+++ b/src/compiler/scala/tools/nsc/transform/InlineErasure.scala
@@ -4,8 +4,8 @@ package transform
 trait InlineErasure {
   self: Erasure =>
 
-/**
+/*
   import global._
   import definitions._
- **/
+ */
 }
diff --git a/src/compiler/scala/tools/nsc/transform/LambdaLift.scala b/src/compiler/scala/tools/nsc/transform/LambdaLift.scala
index 60815da967..6ff8792a45 100644
--- a/src/compiler/scala/tools/nsc/transform/LambdaLift.scala
+++ b/src/compiler/scala/tools/nsc/transform/LambdaLift.scala
@@ -253,8 +253,7 @@ abstract class LambdaLift extends InfoTransform {
         }
       }
 
-      /** Rename a trait's interface and implementation class in coordinated fashion.
-       */
+      /* Rename a trait's interface and implementation class in coordinated fashion. */
       def renameTrait(traitSym: Symbol, implSym: Symbol) {
         val originalImplName = implSym.name
         renameSym(traitSym)
@@ -457,7 +456,7 @@ abstract class LambdaLift extends InfoTransform {
               case arg => arg
             }
 
-            /** Wrap expr argument in new *Ref(..) constructor. But try/catch
+            /* Wrap expr argument in new *Ref(..) constructor. But try/catch
              * is a problem because a throw will clear the stack and post catch
              * we would expect the partially-constructed object to be on the stack
              * for the call to init. So we recursively
diff --git a/src/compiler/scala/tools/nsc/transform/Mixin.scala b/src/compiler/scala/tools/nsc/transform/Mixin.scala
index 988e80aa77..e0b30ab9f9 100644
--- a/src/compiler/scala/tools/nsc/transform/Mixin.scala
+++ b/src/compiler/scala/tools/nsc/transform/Mixin.scala
@@ -201,7 +201,7 @@ abstract class Mixin extends InfoTransform with ast.TreeDSL {
       treatedClassInfos(clazz) = clazz.info
       assert(phase == currentRun.mixinPhase, phase)
 
-      /** Create a new getter. Getters are never private or local. They are
+      /* Create a new getter. Getters are never private or local. They are
        *  always accessors and deferred. */
       def newGetter(field: Symbol): Symbol = {
         // println("creating new getter for "+ field +" : "+ field.info +" at "+ field.locationString+(field hasFlag MUTABLE))
@@ -210,8 +210,8 @@ abstract class Mixin extends InfoTransform with ast.TreeDSL {
         clazz.newMethod(nme.getterName(field.name.toTermName), field.pos, newFlags) setInfo MethodType(Nil, field.info)
       }
 
-      /** Create a new setter. Setters are never private or local. They are
-       *  always accessors and deferred. */
+      /* Create a new setter. Setters are never private or local. They are
+       * always accessors and deferred. */
       def newSetter(field: Symbol): Symbol = {
         //println("creating new setter for "+field+field.locationString+(field hasFlag MUTABLE))
         val setterName = nme.getterToSetter(nme.getterName(field.name.toTermName))
@@ -264,7 +264,7 @@ abstract class Mixin extends InfoTransform with ast.TreeDSL {
         resetFlag DEFERRED | lateDEFERRED
     )
 
-    /** Mix in members of implementation class mixinClass into class clazz */
+    /* Mix in members of implementation class mixinClass into class clazz */
     def mixinImplClassMembers(mixinClass: Symbol, mixinInterface: Symbol) {
       if (!mixinClass.isImplClass) debugwarn ("Impl class flag is not set " +
         ((mixinClass.debugLocationString, mixinInterface.debugLocationString)))
@@ -280,9 +280,9 @@ abstract class Mixin extends InfoTransform with ast.TreeDSL {
       }
     }
 
-    /** Mix in members of trait mixinClass into class clazz. Also,
-     *  for each lazy field in mixinClass, add a link from its mixed in member to its
-     *  initializer method inside the implclass.
+    /* Mix in members of trait mixinClass into class clazz. Also,
+     * for each lazy field in mixinClass, add a link from its mixed in member to its
+     * initializer method inside the implclass.
      */
     def mixinTraitMembers(mixinClass: Symbol) {
       // For all members of a trait's interface do:
@@ -649,34 +649,34 @@ abstract class Mixin extends InfoTransform with ast.TreeDSL {
     private def addNewDefs(clazz: Symbol, stats: List[Tree]): List[Tree] = {
       val newDefs = mutable.ListBuffer[Tree]()
 
-      /** Attribute given tree and anchor at given position */
+      /* Attribute given tree and anchor at given position */
       def attributedDef(pos: Position, tree: Tree): Tree = {
         debuglog("add new def to " + clazz + ": " + tree)
         typedPos(pos)(tree)
       }
 
-      /** The position of given symbol, or, if this is undefined,
-       *  the position of the current class.
+      /* The position of given symbol, or, if this is undefined,
+       * the position of the current class.
        */
       def position(sym: Symbol) =
         if (sym.pos == NoPosition) clazz.pos else sym.pos
 
-      /** Add tree at given position as new definition */
+      /* Add tree at given position as new definition */
       def addDef(pos: Position, tree: Tree) {
         newDefs += attributedDef(pos, tree)
       }
 
-      /** Add new method definition.
+      /* Add new method definition.
        *
-       *  @param sym   The method symbol.
-       *  @param rhs   The method body.
+       * @param sym   The method symbol.
+       * @param rhs   The method body.
        */
       def addDefDef(sym: Symbol, rhs: Tree = EmptyTree) = addDef(position(sym), DefDef(sym, rhs))
       def addValDef(sym: Symbol, rhs: Tree = EmptyTree) = addDef(position(sym), ValDef(sym, rhs))
 
-      /** Add `newdefs` to `stats`, removing any abstract method definitions
-       *  in `stats` that are matched by some symbol defined in
-       *  `newDefs`.
+      /* Add `newdefs` to `stats`, removing any abstract method definitions
+       * in `stats` that are matched by some symbol defined in
+       * `newDefs`.
        */
       def add(stats: List[Tree], newDefs: List[Tree]) = {
         val newSyms = newDefs map (_.symbol)
@@ -692,12 +692,12 @@ abstract class Mixin extends InfoTransform with ast.TreeDSL {
         else newDefs ::: (stats filter isNotDuplicate)
       }
 
-      /** If `stat` is a superaccessor, complete it by adding a right-hand side.
-       *  Note: superaccessors are always abstract until this point.
-       *   The method to call in a superaccessor is stored in the accessor symbol's alias field.
-       *  The rhs is:
-       *    super.A(xs)  where A is the super accessor's alias and xs are its formal parameters.
-       *  This rhs is typed and then mixin transformed.
+      /* If `stat` is a superaccessor, complete it by adding a right-hand side.
+       * Note: superaccessors are always abstract until this point.
+       *  The method to call in a superaccessor is stored in the accessor symbol's alias field.
+       * The rhs is:
+       *   super.A(xs)  where A is the super accessor's alias and xs are its formal parameters.
+       * This rhs is typed and then mixin transformed.
        */
       def completeSuperAccessor(stat: Tree) = stat match {
         case DefDef(_, _, _, vparams :: Nil, _, EmptyTree) if stat.symbol.isSuperAccessor =>
@@ -709,7 +709,7 @@ abstract class Mixin extends InfoTransform with ast.TreeDSL {
           stat
       }
 
-      /**
+      /*
        *  Return the bitmap field for 'offset'. Depending on the hierarchy it is possible to reuse
        *  the bitmap of its parents. If that does not exist yet we create one.
        */
@@ -751,7 +751,7 @@ abstract class Mixin extends InfoTransform with ast.TreeDSL {
         if (kind == LongClass ) LIT(1L << realOffset) else LIT(1 << realOffset)
       }
 
-      /** Return an (untyped) tree of the form 'Clazz.this.bmp = Clazz.this.bmp | mask'. */
+      /* Return an (untyped) tree of the form 'Clazz.this.bmp = Clazz.this.bmp | mask'. */
       def mkSetFlag(clazz: Symbol, offset: Int, valSym: Symbol, kind: ClassSymbol): Tree = {
         val bmp      = bitmapFor(clazz, offset, valSym)
         def mask     = maskForOffset(offset, valSym, kind)
@@ -761,8 +761,8 @@ abstract class Mixin extends InfoTransform with ast.TreeDSL {
         x === newValue
       }
 
-      /** Return an (untyped) tree of the form 'clazz.this.bitmapSym & mask (==|!=) 0', the
-       *  precise comparison operator depending on the value of 'equalToZero'.
+      /* Return an (untyped) tree of the form 'clazz.this.bitmapSym & mask (==|!=) 0', the
+       * precise comparison operator depending on the value of 'equalToZero'.
        */
       def mkTest(clazz: Symbol, mask: Tree, bitmapSym: Symbol, equalToZero: Boolean, kind: ClassSymbol): Tree = {
         val bitmapTree  = (This(clazz) DOT bitmapSym)
@@ -800,17 +800,17 @@ abstract class Mixin extends InfoTransform with ast.TreeDSL {
       }
 
 
-	  /** Always copy the tree if we are going to perform sym substitution,
-	   *  otherwise we will side-effect on the tree that is used in the fast path
-	   */
-	  class TreeSymSubstituterWithCopying(from: List[Symbol], to: List[Symbol]) extends TreeSymSubstituter(from, to) {
-	    override def transform(tree: Tree): Tree =
-	      if (tree.hasSymbolField && from.contains(tree.symbol))
-	        super.transform(tree.duplicate)
-	      else super.transform(tree.duplicate)
+      /* Always copy the tree if we are going to perform sym substitution,
+       * otherwise we will side-effect on the tree that is used in the fast path
+       */
+      class TreeSymSubstituterWithCopying(from: List[Symbol], to: List[Symbol]) extends TreeSymSubstituter(from, to) {
+        override def transform(tree: Tree): Tree =
+          if (tree.hasSymbolField && from.contains(tree.symbol))
+            super.transform(tree.duplicate)
+          else super.transform(tree.duplicate)
 
-	    override def apply[T <: Tree](tree: T): T = if (from.isEmpty) tree else super.apply(tree)
-	  }
+        override def apply[T <: Tree](tree: T): T = if (from.isEmpty) tree else super.apply(tree)
+      }
 
       /** return a 'lazified' version of rhs. It uses double-checked locking to ensure
        *  initialization is performed at most once. For performance reasons the double-checked
@@ -889,11 +889,11 @@ abstract class Mixin extends InfoTransform with ast.TreeDSL {
         typedPos(pos)(BLOCK(result, retVal))
       }
 
-      /** Complete lazy field accessors. Applies only to classes,
-       *  for it's own (non inherited) lazy fields. If 'checkinit'
-       *  is enabled, getters that check for the initialized bit are
-       *  generated, and the class constructor is changed to set the
-       *  initialized bits.
+      /* Complete lazy field accessors. Applies only to classes,
+       * for it's own (non inherited) lazy fields. If 'checkinit'
+       * is enabled, getters that check for the initialized bit are
+       * generated, and the class constructor is changed to set the
+       * initialized bits.
        */
       def addCheckedGetters(clazz: Symbol, stats: List[Tree]): List[Tree] = {
         def dd(stat: DefDef) = {
@@ -974,17 +974,17 @@ abstract class Mixin extends InfoTransform with ast.TreeDSL {
         }
       }
 
-      /** Adds statements to set the 'init' bit for each field initialized
-       *  in the body of a constructor.
+      /* Adds statements to set the 'init' bit for each field initialized
+       * in the body of a constructor.
        */
       def addInitBits(clazz: Symbol, rhs: Tree): Tree =
         new AddInitBitsTransformer(clazz) transform rhs
 
       // begin addNewDefs
 
-      /** Fill the map from fields to offset numbers.
-       *  Instead of field symbols, the map keeps their getter symbols. This makes
-       *  code generation easier later.
+      /* Fill the map from fields to offset numbers.
+       * Instead of field symbols, the map keeps their getter symbols. This makes
+       * code generation easier later.
        */
       def buildBitmapOffsets() {
         def fold(fields: List[Symbol], category: Name) = {
@@ -1060,7 +1060,7 @@ abstract class Mixin extends InfoTransform with ast.TreeDSL {
               else if (needsInitFlag(sym))
                 mkCheckedAccessor(clazz, accessedRef, fieldOffset(sym), sym.pos, sym)
               else
-                gen.mkCheckInit(accessedRef)
+                accessedRef
             })
           }
           else if (sym.isModule && !(sym hasFlag LIFTED | BRIDGE)) {
diff --git a/src/compiler/scala/tools/nsc/transform/PostErasure.scala b/src/compiler/scala/tools/nsc/transform/PostErasure.scala
index 2a86d711f1..96263f3c0c 100644
--- a/src/compiler/scala/tools/nsc/transform/PostErasure.scala
+++ b/src/compiler/scala/tools/nsc/transform/PostErasure.scala
@@ -33,11 +33,11 @@ trait PostErasure extends InfoTransform with TypingTransformers {
     override def transform(tree: Tree) = {
       def finish(res: Tree) = logResult(s"Posterasure reduction\n  Old: $tree\n  New")(res)
 
-      /** We use the name of the operation being performed and not the symbol
-       *  itself because the symbol hails from the boxed class, and this transformation
-       *  exists to operate directly on the values. So we are for instance looking
-       *  up == on an lhs of type Int, whereas the symbol which has been passed in
-       *  is from java.lang.Integer.
+      /* We use the name of the operation being performed and not the symbol
+       * itself because the symbol hails from the boxed class, and this transformation
+       * exists to operate directly on the values. So we are for instance looking
+       * up == on an lhs of type Int, whereas the symbol which has been passed in
+       * is from java.lang.Integer.
        */
       def binop(lhs: Tree, op: Symbol, rhs: Tree) =
         finish(localTyper typed (Apply(Select(lhs, op.name) setPos tree.pos, rhs :: Nil) setPos tree.pos))
diff --git a/src/compiler/scala/tools/nsc/transform/SpecializeTypes.scala b/src/compiler/scala/tools/nsc/transform/SpecializeTypes.scala
index 0cd7f516ef..15fe9f0a24 100644
--- a/src/compiler/scala/tools/nsc/transform/SpecializeTypes.scala
+++ b/src/compiler/scala/tools/nsc/transform/SpecializeTypes.scala
@@ -518,9 +518,9 @@ abstract class SpecializeTypes extends InfoTransform with TypingTransformers {
    */
   def specializeClass(clazz: Symbol, outerEnv: TypeEnv): List[Symbol] = {
     def specializedClass(env0: TypeEnv, normMembers: List[Symbol]): Symbol = {
-      /** It gets hard to follow all the clazz and cls, and specializedClass
-       *  was both already used for a map and mucho long.  So "sClass" is the
-       *  specialized subclass of "clazz" throughout this file.
+      /* It gets hard to follow all the clazz and cls, and specializedClass
+       * was both already used for a map and mucho long.  So "sClass" is the
+       * specialized subclass of "clazz" throughout this file.
        */
 
       // SI-5545: Eliminate classes with the same name loaded from the bytecode already present - all we need to do is
@@ -558,12 +558,12 @@ abstract class SpecializeTypes extends InfoTransform with TypingTransformers {
         def applyContext(tpe: Type) =
           subst(env, tpe).instantiateTypeParams(oldClassTParams, newClassTParams map (_.tpe))
 
-        /** Return a list of specialized parents to be re-mixed in a specialized subclass.
-         *  Assuming env = [T -> Int] and
-         *    class Integral[@specialized T] extends Numeric[T]
-         *  and Numeric[U] is specialized on U, this produces List(Numeric$mcI).
+        /* Return a list of specialized parents to be re-mixed in a specialized subclass.
+         * Assuming env = [T -> Int] and
+         *   class Integral[@specialized T] extends Numeric[T]
+         * and Numeric[U] is specialized on U, this produces List(Numeric$mcI).
          *
-         *  so that class Integral$mci extends Integral[Int] with Numeric$mcI.
+         * so that class Integral$mci extends Integral[Int] with Numeric$mcI.
          */
         def specializedParents(parents: List[Type]): List[Type] = {
           var res: List[Type] = Nil
@@ -604,10 +604,10 @@ abstract class SpecializeTypes extends InfoTransform with TypingTransformers {
       exitingSpecialize(sClass setInfo specializedInfoType)
       val fullEnv = outerEnv ++ env
 
-      /** Enter 'sym' in the scope of the current specialized class. It's type is
-       *  mapped through the active environment, binding type variables to concrete
-       *  types. The existing typeEnv for `sym` is composed with the current active
-       *  environment
+      /* Enter 'sym' in the scope of the current specialized class. It's type is
+       * mapped through the active environment, binding type variables to concrete
+       * types. The existing typeEnv for `sym` is composed with the current active
+       * environment
        */
       def enterMember(sym: Symbol): Symbol = {
         typeEnv(sym) = fullEnv ++ typeEnv(sym) // append the full environment
@@ -620,18 +620,18 @@ abstract class SpecializeTypes extends InfoTransform with TypingTransformers {
         decls1 enter subst(fullEnv)(sym)
       }
 
-      /** Create and enter in scope an overridden symbol m1 for `m` that forwards
-       *  to `om`. `om` is a fresh, special overload of m1 that is an implementation
-       *  of `m`. For example, for a
+      /* Create and enter in scope an overridden symbol m1 for `m` that forwards
+       * to `om`. `om` is a fresh, special overload of m1 that is an implementation
+       * of `m`. For example, for a
        *
-       *  class Foo[@specialized A] {
-       *    def m(x: A) = <body> // m
-       *  }
-       *  , for class Foo$I extends Foo[Int], this method enters two new symbols in
-       *  the scope of Foo$I:
+       * class Foo[@specialized A] {
+       *   def m(x: A) = <body> // m
+       * }
+       * , for class Foo$I extends Foo[Int], this method enters two new symbols in
+       * the scope of Foo$I:
        *
-       *    def m(x: Int) = m$I(x) // m1
-       *    def m$I(x: Int) = <body>/adapted to env {A -> Int} // om
+       *   def m(x: Int) = m$I(x) // m1
+       *   def m$I(x: Int) = <body>/adapted to env {A -> Int} // om
        */
       def forwardToOverload(m: Symbol): Symbol = {
         val specMember = enterMember(cloneInSpecializedClass(m, f => (f | OVERRIDE) & ~(DEFERRED | CASEACCESSOR)))
@@ -935,13 +935,13 @@ abstract class SpecializeTypes extends InfoTransform with TypingTransformers {
    *  this method will return List('apply$mcII$sp')
    */
   private def specialOverrides(clazz: Symbol) = logResultIf[List[Symbol]]("specialized overrides in " + clazz, _.nonEmpty) {
-    /** Return the overridden symbol in syms that needs a specialized overriding symbol,
-     *  together with its specialization environment. The overridden symbol may not be
-     *  the closest to 'overriding', in a given hierarchy.
+    /* Return the overridden symbol in syms that needs a specialized overriding symbol,
+     * together with its specialization environment. The overridden symbol may not be
+     * the closest to 'overriding', in a given hierarchy.
      *
-     *  An method m needs a special override if
-     *    * m overrides a method whose type contains specialized type variables
-     *    * there is a valid specialization environment that maps the overridden method type to m's type.
+     * An method m needs a special override if
+     *   * m overrides a method whose type contains specialized type variables
+     *   * there is a valid specialization environment that maps the overridden method type to m's type.
      */
     def needsSpecialOverride(overriding: Symbol): (Symbol, TypeEnv) = {
       def checkOverriddenTParams(overridden: Symbol) {
@@ -1527,7 +1527,7 @@ abstract class SpecializeTypes extends InfoTransform with TypingTransformers {
           if (symbol.isConstructor) {
             val t = atOwner(symbol)(forwardCtorCall(tree.pos, gen.mkSuperInitCall, vparamss, symbol.owner))
             if (symbol.isPrimaryConstructor)
-              localTyper.typedPos(symbol.pos)(deriveDefDef(tree)(_ => Block(List(t), Literal(Constant()))))
+              localTyper.typedPos(symbol.pos)(deriveDefDef(tree)(_ => Block(List(t), Literal(Constant(())))))
             else // duplicate the original constructor
               reportError(duplicateBody(ddef, info(symbol).target))(_ => ddef)
           }
@@ -1797,11 +1797,11 @@ abstract class SpecializeTypes extends InfoTransform with TypingTransformers {
   private def forwardCtorCall(pos: scala.reflect.internal.util.Position, receiver: Tree, paramss: List[List[ValDef]], clazz: Symbol): Tree = {
     log(s"forwardCtorCall($pos, $receiver, $paramss, $clazz)")
 
-    /** A constructor parameter `f` initializes a specialized field
-     *  iff:
-     *    - it is specialized itself
-     *    - there is a getter for the original (non-specialized) field in the same class
-     *    - there is a getter for the specialized field in the same class
+    /* A constructor parameter `f` initializes a specialized field
+     * iff:
+     *   - it is specialized itself
+     *   - there is a getter for the original (non-specialized) field in the same class
+     *   - there is a getter for the specialized field in the same class
      */
     def initializesSpecializedField(f: Symbol) = (
          (f.name endsWith nme.SPECIALIZED_SUFFIX)
diff --git a/src/compiler/scala/tools/nsc/transform/TailCalls.scala b/src/compiler/scala/tools/nsc/transform/TailCalls.scala
index 2418698a18..92ed7fc555 100644
--- a/src/compiler/scala/tools/nsc/transform/TailCalls.scala
+++ b/src/compiler/scala/tools/nsc/transform/TailCalls.scala
@@ -134,9 +134,9 @@ abstract class TailCalls extends Transform {
         this.tailPos  = true
         this.failPos  = dd.pos
 
-        /** Create a new method symbol for the current method and store it in
-          * the label field.
-          */
+        /* Create a new method symbol for the current method and store it in
+         * the label field.
+         */
         this.label    = {
           val label     = method.newLabel(newTermName("_" + method.name), method.pos)
           val thisParam = method.newSyntheticValueParam(currentClass.typeOfThis)
@@ -186,8 +186,7 @@ abstract class TailCalls extends Transform {
     }
 
     override def transform(tree: Tree): Tree = {
-      /** A possibly polymorphic apply to be considered for tail call transformation.
-       */
+      /* A possibly polymorphic apply to be considered for tail call transformation. */
       def rewriteApply(target: Tree, fun: Tree, targs: List[Tree], args: List[Tree]) = {
         val receiver: Tree = fun match {
           case Select(qual, _)  => qual
@@ -200,8 +199,8 @@ abstract class TailCalls extends Transform {
         def transformArgs     = noTailTransforms(args)
         def matchesTypeArgs   = ctx.tparams sameElements (targs map (_.tpe.typeSymbol))
 
-        /** Records failure reason in Context for reporting.
-         *  Position is unchanged (by default, the method definition.)
+        /* Records failure reason in Context for reporting.
+         * Position is unchanged (by default, the method definition.)
          */
         def fail(reason: String) = {
           debuglog("Cannot rewrite recursive call at: " + fun.pos + " because: " + reason)
@@ -209,8 +208,7 @@ abstract class TailCalls extends Transform {
           ctx.failReason = reason
           treeCopy.Apply(tree, noTailTransform(target), transformArgs)
         }
-        /** Position of failure is that of the tree being considered.
-         */
+        /* Position of failure is that of the tree being considered. */
         def failHere(reason: String) = {
           ctx.failPos = fun.pos
           fail(reason)
@@ -264,8 +262,8 @@ abstract class TailCalls extends Transform {
 
           deriveDefDef(tree){rhs =>
             if (newCtx.isTransformed) {
-              /** We have rewritten the tree, but there may be nested recursive calls remaining.
-               *  If @tailrec is given we need to fail those now.
+              /* We have rewritten the tree, but there may be nested recursive calls remaining.
+               * If @tailrec is given we need to fail those now.
                */
               if (newCtx.isMandatory) {
                 for (t @ Apply(fn, _) <- newRHS ; if fn.symbol == newCtx.method) {
diff --git a/src/compiler/scala/tools/nsc/transform/UnCurry.scala b/src/compiler/scala/tools/nsc/transform/UnCurry.scala
index 94ca1206b9..8fd1df7cea 100644
--- a/src/compiler/scala/tools/nsc/transform/UnCurry.scala
+++ b/src/compiler/scala/tools/nsc/transform/UnCurry.scala
@@ -401,8 +401,7 @@ abstract class UnCurry extends InfoTransform
         finally needTryLift = saved
       }
 
-      /** Transform tree `t` to { def f = t; f } where `f` is a fresh name
-       */
+      /* Transform tree `t` to { def f = t; f } where `f` is a fresh name */
       def liftTree(tree: Tree) = {
         debuglog("lifting tree at: " + (tree.pos))
         val sym = currentOwner.newMethod(unit.freshTermName("liftedTree"), tree.pos)
@@ -550,8 +549,6 @@ abstract class UnCurry extends InfoTransform
           false
       }
 
-      def isDefaultCatch(cdef: CaseDef) = isThrowable(cdef.pat) && cdef.guard.isEmpty
-
       tree match {
         /* Some uncurry post transformations add members to templates.
          *
@@ -701,7 +698,7 @@ abstract class UnCurry extends InfoTransform
         // update the type of the method after uncurry.
         dd.symbol updateInfo {
           val GenPolyType(tparams, tp) = dd.symbol.info
-          logResult("erased dependent param types for ${dd.symbol.info}") {
+          logResult(s"erased dependent param types for ${dd.symbol.info}") {
             GenPolyType(tparams, MethodType(allParams map (_.symbol), tp.finalResultType))
           }
         }
diff --git a/src/compiler/scala/tools/nsc/transform/patmat/Logic.scala b/src/compiler/scala/tools/nsc/transform/patmat/Logic.scala
index 69d9987b05..0371df3b10 100644
--- a/src/compiler/scala/tools/nsc/transform/patmat/Logic.scala
+++ b/src/compiler/scala/tools/nsc/transform/patmat/Logic.scala
@@ -6,7 +6,6 @@
 
 package scala.tools.nsc.transform.patmat
 
-import scala.tools.nsc.symtab._
 import scala.language.postfixOps
 import scala.collection.mutable
 import scala.reflect.internal.util.Statistics
@@ -366,7 +365,7 @@ trait ScalaLogic extends Interface with Logic with TreeAndTypeAnalysis {
        * and thus in this variable's equality symbols), but reachability also requires us to model things like V = 1 precluding V = "1"
        */
       lazy val implications = {
-        /** when we know V = C, which other equalities must hold
+        /* when we know V = C, which other equalities must hold
          *
          * in general, equality to some type implies equality to its supertypes
          * (this multi-valued kind of equality is necessary for unreachability)
@@ -385,7 +384,7 @@ trait ScalaLogic extends Interface with Logic with TreeAndTypeAnalysis {
           // else  debug.patmat("NOT implies: "+(lower, upper))
 
 
-        /** does V = C preclude V having value `other`?
+        /* does V = C preclude V having value `other`?
          (1) V = null is an exclusive assignment,
          (2) V = A and V = B, for A and B value constants, are mutually exclusive unless A == B
              we err on the safe side, for example:
@@ -497,11 +496,11 @@ trait ScalaLogic extends Interface with Logic with TreeAndTypeAnalysis {
         uniques.get(tp).getOrElse(
           uniques.find {case (oldTp, oldC) => oldTp =:= tp} match {
             case Some((_, c)) =>
-              debug.patmat("unique const: "+ (tp, c))
+              debug.patmat("unique const: "+ ((tp, c)))
               c
             case _ =>
               val fresh = mkFresh
-              debug.patmat("uniqued const: "+ (tp, fresh))
+              debug.patmat("uniqued const: "+ ((tp, fresh)))
               uniques(tp) = fresh
               fresh
           })
@@ -517,12 +516,12 @@ trait ScalaLogic extends Interface with Logic with TreeAndTypeAnalysis {
         if (!t.symbol.isStable) t.tpe.narrow
         else trees find (a => a.correspondsStructure(t)(sameValue)) match {
           case Some(orig) =>
-            debug.patmat("unique tp for tree: "+ (orig, orig.tpe))
+            debug.patmat("unique tp for tree: "+ ((orig, orig.tpe)))
             orig.tpe
           case _ =>
             // duplicate, don't mutate old tree (TODO: use a map tree -> type instead?)
             val treeWithNarrowedType = t.duplicate setType t.tpe.narrow
-            debug.patmat("uniqued: "+ (t, t.tpe, treeWithNarrowedType.tpe))
+            debug.patmat("uniqued: "+ ((t, t.tpe, treeWithNarrowedType.tpe)))
             trees += treeWithNarrowedType
             treeWithNarrowedType.tpe
         }
@@ -623,4 +622,4 @@ trait ScalaLogic extends Interface with Logic with TreeAndTypeAnalysis {
       override def toString = "null"
     }
   }
-}
\ No newline at end of file
+}
diff --git a/src/compiler/scala/tools/nsc/transform/patmat/MatchAnalysis.scala b/src/compiler/scala/tools/nsc/transform/patmat/MatchAnalysis.scala
index 3ee75df6c4..006c7bd85f 100644
--- a/src/compiler/scala/tools/nsc/transform/patmat/MatchAnalysis.scala
+++ b/src/compiler/scala/tools/nsc/transform/patmat/MatchAnalysis.scala
@@ -12,14 +12,10 @@ import scala.reflect.internal.util.Statistics
 import scala.reflect.internal.util.Position
 
 trait TreeAndTypeAnalysis extends Debugging {
-  import global.{Tree, Type, Symbol, definitions, analyzer,
-    ConstantType, Literal, Constant,  appliedType, WildcardType, TypeRef, ModuleClassSymbol,
-    nestedMemberType, TypeMap, Ident}
-
+  import global._
   import definitions._
   import analyzer.Typer
 
-
   // we use subtyping as a model for implication between instanceof tests
   // i.e., when S <:< T we assume x.isInstanceOf[S] implies x.isInstanceOf[T]
   // unfortunately this is not true in general:
@@ -60,7 +56,7 @@ trait TreeAndTypeAnalysis extends Debugging {
           Some(List(tp))
         // make sure it's not a primitive, else (5: Byte) match { case 5 => ... } sees no Byte
         case sym if !sym.isSealed || isPrimitiveValueClass(sym) =>
-          debug.patmat("enum unsealed "+ (tp, sym, sym.isSealed, isPrimitiveValueClass(sym)))
+          debug.patmat("enum unsealed "+ ((tp, sym, sym.isSealed, isPrimitiveValueClass(sym))))
           None
         case sym =>
           val subclasses = (
@@ -68,7 +64,7 @@ trait TreeAndTypeAnalysis extends Debugging {
             // symbols which are both sealed and abstract need not be covered themselves, because
             // all of their children must be and they cannot otherwise be created.
             filterNot (x => x.isSealed && x.isAbstractClass && !isPrimitiveValueClass(x)))
-          debug.patmat("enum sealed -- subclasses: "+ (sym, subclasses))
+          debug.patmat("enum sealed -- subclasses: "+ ((sym, subclasses)))
 
           val tpApprox = typer.infer.approximateAbstracts(tp)
           val pre = tpApprox.prefix
@@ -86,7 +82,7 @@ trait TreeAndTypeAnalysis extends Debugging {
               if (subTpApprox <:< tpApprox) Some(checkableType(subTp))
               else None
             })
-          debug.patmat("enum sealed "+ (tp, tpApprox) + " as "+ validSubTypes)
+          debug.patmat("enum sealed "+ ((tp, tpApprox)) + " as "+ validSubTypes)
           Some(validSubTypes)
       }
 
@@ -108,7 +104,7 @@ trait TreeAndTypeAnalysis extends Debugging {
       }
 
       val res = typeArgsToWildcardsExceptArray(tp)
-      debug.patmat("checkable "+(tp, res))
+      debug.patmat("checkable "+((tp, res)))
       res
     }
 
@@ -126,8 +122,8 @@ trait TreeAndTypeAnalysis extends Debugging {
 }
 
 trait MatchApproximation extends TreeAndTypeAnalysis with ScalaLogic with MatchTreeMaking {
-  import global.{Tree, Type, NoType, Symbol, NoSymbol, ConstantType, Literal, Constant, Ident, UniqueType, RefinedType, EmptyScope}
-  import global.definitions.{ListClass, NilModule}
+  import global._
+  import global.definitions._
 
   /**
    * Represent a match as a formula in propositional logic that encodes whether the match matches (abstractly: we only consider types)
@@ -344,8 +340,8 @@ trait MatchApproximation extends TreeAndTypeAnalysis with ScalaLogic with MatchT
 
 trait MatchAnalysis extends MatchApproximation {
   import PatternMatchingStats._
-  import global.{Tree, Type, Symbol, NoSymbol, Ident, Select}
-  import global.definitions.{isPrimitiveValueClass, ConsClass, isTupleSymbol}
+  import global._
+  import global.definitions._
 
   trait MatchAnalyzer extends MatchApproximator  {
     def uncheckedWarning(pos: Position, msg: String) = global.currentUnit.uncheckedWarning(pos, msg)
@@ -636,7 +632,7 @@ trait MatchAnalysis extends MatchApproximation {
         def toCounterExample(beBrief: Boolean = false): CounterExample =
           if (!allFieldAssignmentsLegal) NoExample
           else {
-            debug.patmat("describing "+ (variable, equalTo, notEqualTo, fields, cls, allFieldAssignmentsLegal))
+            debug.patmat("describing "+ ((variable, equalTo, notEqualTo, fields, cls, allFieldAssignmentsLegal)))
             val res = prunedEqualTo match {
               // a definite assignment to a value
               case List(eq: ValueConst) if fields.isEmpty => ValueExample(eq)
diff --git a/src/compiler/scala/tools/nsc/transform/patmat/MatchCodeGen.scala b/src/compiler/scala/tools/nsc/transform/patmat/MatchCodeGen.scala
index 416bdf50f0..889615a39f 100644
--- a/src/compiler/scala/tools/nsc/transform/patmat/MatchCodeGen.scala
+++ b/src/compiler/scala/tools/nsc/transform/patmat/MatchCodeGen.scala
@@ -10,7 +10,6 @@ import scala.tools.nsc.symtab.Flags.SYNTHETIC
 import scala.language.postfixOps
 import scala.reflect.internal.util.Statistics
 import scala.reflect.internal.util.Position
-import scala.reflect.internal.util.NoPosition
 
 /** Factory methods used by TreeMakers to make the actual trees.
  *
@@ -18,10 +17,7 @@ import scala.reflect.internal.util.NoPosition
  * and pure (aka "virtualized": match is parametric in its monad).
  */
 trait MatchCodeGen extends Interface {
-  import PatternMatchingStats._
-  import global.{nme, treeInfo, definitions, gen, Tree, Type, Symbol, NoSymbol,
-    appliedType, NoType, MethodType, newTermName, Name,
-    Block, Literal, Constant, EmptyTree, Function, Typed, ValDef, LabelDef}
+  import global._
   import definitions._
 
   ///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
@@ -79,7 +75,7 @@ trait MatchCodeGen extends Interface {
       // duplicated out of frustration with cast generation
       def mkZero(tp: Type): Tree = {
         tp.typeSymbol match {
-          case UnitClass    => Literal(Constant())
+          case UnitClass    => Literal(Constant(()))
           case BooleanClass => Literal(Constant(false))
           case FloatClass   => Literal(Constant(0.0f))
           case DoubleClass  => Literal(Constant(0.0d))
@@ -255,4 +251,4 @@ trait MatchCodeGen extends Interface {
 
     }
   }
-}
\ No newline at end of file
+}
diff --git a/src/compiler/scala/tools/nsc/transform/patmat/MatchOptimization.scala b/src/compiler/scala/tools/nsc/transform/patmat/MatchOptimization.scala
index dcf2413b15..125e9a3b65 100644
--- a/src/compiler/scala/tools/nsc/transform/patmat/MatchOptimization.scala
+++ b/src/compiler/scala/tools/nsc/transform/patmat/MatchOptimization.scala
@@ -11,7 +11,6 @@ import scala.language.postfixOps
 import scala.collection.mutable
 import scala.reflect.internal.util.Statistics
 import scala.reflect.internal.util.Position
-import scala.reflect.internal.util.NoPosition
 
 /** Optimize and analyze matches based on their TreeMaker-representation.
  *
@@ -20,15 +19,9 @@ import scala.reflect.internal.util.NoPosition
  * TODO: split out match analysis
  */
 trait MatchOptimization extends MatchTreeMaking with MatchAnalysis {
-  import PatternMatchingStats._
-  import global.{Tree, Type, Symbol, NoSymbol, CaseDef, atPos,
-    ConstantType, Literal, Constant, gen, EmptyTree,
-    Typed, treeInfo, nme, Ident,
-    Apply, If, Bind, lub, Alternative, deriveCaseDef, Match, MethodType, LabelDef, TypeTree, Throw}
-
+  import global._
   import global.definitions._
 
-
   ////
   trait CommonSubconditionElimination extends OptimizedCodegen with MatchApproximator {
     /** a flow-sensitive, generalised, common sub-expression elimination
@@ -160,7 +153,7 @@ trait MatchOptimization extends MatchTreeMaking with MatchAnalysis {
       def chainBefore(next: Tree)(casegen: Casegen): Tree = // assert(codegen eq optimizedCodegen)
         atPos(pos)(casegen.asInstanceOf[optimizedCodegen.OptimizedCasegen].flatMapCondStored(cond, storedCond, res, nextBinder, substitution(next).duplicate))
 
-      override def toString = "Memo"+(nextBinder.name, storedCond.name, cond, res, substitution)
+      override def toString = "Memo"+((nextBinder.name, storedCond.name, cond, res, substitution))
     }
 
     case class ReusingCondTreeMaker(sharedPrefix: List[Test], toReused: TreeMaker => TreeMaker) extends TreeMaker { import CODE._
@@ -199,7 +192,7 @@ trait MatchOptimization extends MatchTreeMaking with MatchAnalysis {
         // and in its confusion it emits illegal casts (diagnosed by Grzegorz: checkcast T ; invokevirtual S.m, where T not a subtype of S)
         casegen.ifThenElseZero(REF(lastReusedTreeMaker.storedCond), substitution(next).duplicate)
       }
-      override def toString = "R"+(lastReusedTreeMaker.storedCond.name, substitution)
+      override def toString = "R"+((lastReusedTreeMaker.storedCond.name, substitution))
     }
   }
 
diff --git a/src/compiler/scala/tools/nsc/transform/patmat/MatchTranslation.scala b/src/compiler/scala/tools/nsc/transform/patmat/MatchTranslation.scala
index 23b33e9be6..c8c3b741f1 100644
--- a/src/compiler/scala/tools/nsc/transform/patmat/MatchTranslation.scala
+++ b/src/compiler/scala/tools/nsc/transform/patmat/MatchTranslation.scala
@@ -243,7 +243,7 @@ trait MatchTranslation { self: PatternMatching  =>
         if (!extractor.isTyped) ErrorUtils.issueNormalTypeError(patTree, "Could not typecheck extractor call: "+ extractor)(context)
         // if (extractor.resultInMonad == ErrorType) throw new TypeError(pos, "Unsupported extractor type: "+ extractor.tpe)
 
-        debug.patmat("translateExtractorPattern checking parameter type: "+ (patBinder, patBinder.info.widen, extractor.paramType, patBinder.info.widen <:< extractor.paramType))
+        debug.patmat("translateExtractorPattern checking parameter type: "+ ((patBinder, patBinder.info.widen, extractor.paramType, patBinder.info.widen <:< extractor.paramType)))
 
         // must use type `tp`, which is provided by extractor's result, not the type expected by binder,
         // as b.info may be based on a Typed type ascription, which has not been taken into account yet by the translation
@@ -309,7 +309,7 @@ trait MatchTranslation { self: PatternMatching  =>
           // debug.patmat("unfun: "+ (unfun.tpe, unfun.symbol.ownerChain, unfun.symbol.info, patBinder.info))
           translateExtractorPattern(ExtractorCall(unfun, args))
 
-        /** A constructor pattern is of the form c(p1, ..., pn) where n ≥ 0.
+        /* A constructor pattern is of the form c(p1, ..., pn) where n ≥ 0.
           It consists of a stable identifier c, followed by element patterns p1, ..., pn.
           The constructor c is a simple or qualified name which denotes a case class (§5.3.2).
 
@@ -328,22 +328,22 @@ trait MatchTranslation { self: PatternMatching  =>
             noFurtherSubPats()
           }
 
-        /** A typed pattern x : T consists of a pattern variable x and a type pattern T.
-            The type of x is the type pattern T, where each type variable and wildcard is replaced by a fresh, unknown type.
-            This pattern matches any value matched by the type pattern T (§8.2); it binds the variable name to that value.
-        **/
+        /* A typed pattern x : T consists of a pattern variable x and a type pattern T.
+           The type of x is the type pattern T, where each type variable and wildcard is replaced by a fresh, unknown type.
+           This pattern matches any value matched by the type pattern T (§8.2); it binds the variable name to that value.
+        */
         // must treat Typed and Bind together -- we need to know the patBinder of the Bind pattern to get at the actual type
         case MaybeBoundTyped(subPatBinder, pt) =>
           val next = glb(List(dealiasWiden(patBinder.info), pt)).normalize
           // a typed pattern never has any subtrees
           noFurtherSubPats(TypeTestTreeMaker(subPatBinder, patBinder, pt, next)(pos))
 
-        /** A pattern binder x@p consists of a pattern variable x and a pattern p.
-            The type of the variable x is the static type T of the pattern p.
-            This pattern matches any value v matched by the pattern p,
-            provided the run-time type of v is also an instance of T,  <-- TODO! https://issues.scala-lang.org/browse/SI-1503
-            and it binds the variable name to that value.
-        **/
+        /* A pattern binder x@p consists of a pattern variable x and a pattern p.
+           The type of the variable x is the static type T of the pattern p.
+           This pattern matches any value v matched by the pattern p,
+           provided the run-time type of v is also an instance of T,  <-- TODO! https://issues.scala-lang.org/browse/SI-1503
+           and it binds the variable name to that value.
+        */
         case Bound(subpatBinder, p)          =>
           // replace subpatBinder by patBinder (as if the Bind was not there)
           withSubPats(List(SubstOnlyTreeMaker(subpatBinder, patBinder)),
@@ -351,14 +351,14 @@ trait MatchTranslation { self: PatternMatching  =>
             (patBinder, p)
           )
 
-        /** 8.1.4 Literal Patterns
-              A literal pattern L matches any value that is equal (in terms of ==) to the literal L.
-              The type of L must conform to the expected type of the pattern.
+        /* 8.1.4 Literal Patterns
+             A literal pattern L matches any value that is equal (in terms of ==) to the literal L.
+             The type of L must conform to the expected type of the pattern.
 
-            8.1.5 Stable Identifier Patterns  (a stable identifier r (see §3.1))
-              The pattern matches any value v such that r == v (§12.1).
-              The type of r must conform to the expected type of the pattern.
-        **/
+           8.1.5 Stable Identifier Patterns  (a stable identifier r (see §3.1))
+             The pattern matches any value v such that r == v (§12.1).
+             The type of r must conform to the expected type of the pattern.
+        */
         case Literal(Constant(_)) | Ident(_) | Select(_, _) | This(_) =>
           noFurtherSubPats(EqualityTestTreeMaker(patBinder, patTree, pos))
 
diff --git a/src/compiler/scala/tools/nsc/transform/patmat/MatchTreeMaking.scala b/src/compiler/scala/tools/nsc/transform/patmat/MatchTreeMaking.scala
index 202f3444f8..76268f3ecd 100644
--- a/src/compiler/scala/tools/nsc/transform/patmat/MatchTreeMaking.scala
+++ b/src/compiler/scala/tools/nsc/transform/patmat/MatchTreeMaking.scala
@@ -11,7 +11,6 @@ import scala.language.postfixOps
 import scala.collection.mutable
 import scala.reflect.internal.util.Statistics
 import scala.reflect.internal.util.Position
-import scala.reflect.internal.util.NoPosition
 
 /** Translate our IR (TreeMakers) into actual Scala Trees using the factory methods in MatchCodeGen.
  *
@@ -19,13 +18,8 @@ import scala.reflect.internal.util.NoPosition
  * mostly agnostic to whether we're in optimized/pure (virtualized) mode.
  */
 trait MatchTreeMaking extends MatchCodeGen with Debugging {
-  import PatternMatchingStats._
-  import global.{Tree, Type, Symbol, CaseDef, atPos, settings,
-    Select, Block, ThisType, SingleType, NoPrefix, NoType, needsOuterTest,
-    ConstantType, Literal, Constant, gen, This, EmptyTree, map2, NoSymbol, Traverser,
-    Function, Typed, treeInfo, TypeRef, DefTree, Ident, nme}
-
-  import global.definitions.{SomeClass, AnyRefClass, UncheckedClass, BooleanClass}
+  import global._
+  import definitions.{SomeClass, AnyRefClass, UncheckedClass, BooleanClass}
 
   final case class Suppression(exhaustive: Boolean, unreachable: Boolean)
   object Suppression {
@@ -60,7 +54,7 @@ trait MatchTreeMaking extends MatchCodeGen with Debugging {
 
       private[TreeMakers] def incorporateOuterSubstitution(outerSubst: Substitution): Unit = {
         if (currSub ne null) {
-          debug.patmat("BUG: incorporateOuterSubstitution called more than once for "+ (this, currSub, outerSubst))
+          debug.patmat("BUG: incorporateOuterSubstitution called more than once for "+ ((this, currSub, outerSubst)))
           Thread.dumpStack()
         }
         else currSub = outerSubst >> substitution
@@ -100,7 +94,7 @@ trait MatchTreeMaking extends MatchCodeGen with Debugging {
 
       def chainBefore(next: Tree)(casegen: Casegen): Tree = // assert(next eq EmptyTree)
         atPos(body.pos)(casegen.one(substitution(body))) // since SubstOnly treemakers are dropped, need to do it here
-      override def toString = "B"+(body, matchPt)
+      override def toString = "B"+((body, matchPt))
     }
 
     case class SubstOnlyTreeMaker(prevBinder: Symbol, nextBinder: Symbol) extends TreeMaker {
@@ -220,7 +214,7 @@ trait MatchTreeMaking extends MatchCodeGen with Debugging {
         )
       }
 
-      override def toString = "X"+(extractor, nextBinder.name)
+      override def toString = "X"+((extractor, nextBinder.name))
     }
 
     /**
@@ -274,7 +268,7 @@ trait MatchTreeMaking extends MatchCodeGen with Debugging {
         }
       }
 
-      override def toString = "P"+(prevBinder.name,  extraCond getOrElse "", localSubstitution)
+      override def toString = "P"+((prevBinder.name,  extraCond getOrElse "", localSubstitution))
     }
 
     object IrrefutableExtractorTreeMaker {
@@ -389,7 +383,7 @@ trait MatchTreeMaking extends MatchCodeGen with Debugging {
     **/
     case class TypeTestTreeMaker(prevBinder: Symbol, testedBinder: Symbol, expectedTp: Type, nextBinderTp: Type)(override val pos: Position, extractorArgTypeTest: Boolean = false) extends CondTreeMaker {
       import TypeTestTreeMaker._
-      debug.patmat("TTTM"+(prevBinder, extractorArgTypeTest, testedBinder, expectedTp, nextBinderTp))
+      debug.patmat("TTTM"+((prevBinder, extractorArgTypeTest, testedBinder, expectedTp, nextBinderTp)))
 
       lazy val outerTestNeeded = (
           !((expectedTp.prefix eq NoPrefix) || expectedTp.prefix.typeSymbol.isPackageClass)
@@ -452,7 +446,7 @@ trait MatchTreeMaking extends MatchCodeGen with Debugging {
 
       def impliesBinderNonNull(binder: Symbol) = renderCondition(nonNullImpliedByTestChecker(binder))
 
-      override def toString = "TT"+(expectedTp, testedBinder.name, nextBinderTp)
+      override def toString = "TT"+((expectedTp, testedBinder.name, nextBinderTp))
     }
 
     // need to substitute to deal with existential types -- TODO: deal with existentials better, don't substitute (see RichClass during quick.comp)
@@ -463,7 +457,7 @@ trait MatchTreeMaking extends MatchCodeGen with Debugging {
       // equals need not be well-behaved, so don't intersect with pattern's (stabilized) type (unlike MaybeBoundTyped's accumType, where it's required)
       val cond = codegen._equals(patTree, prevBinder)
       val res  = CODE.REF(prevBinder)
-      override def toString = "ET"+(prevBinder.name, patTree)
+      override def toString = "ET"+((prevBinder.name, patTree))
     }
 
     case class AlternativesTreeMaker(prevBinder: Symbol, var altss: List[List[TreeMaker]], pos: Position) extends TreeMaker with NoNewBinders {
@@ -474,7 +468,7 @@ trait MatchTreeMaking extends MatchCodeGen with Debugging {
         altss = altss map (alts => propagateSubstitution(alts, substitution))
       }
 
-      def chainBefore(next: Tree)(codegenAlt: Casegen): Tree = { import CODE._
+      def chainBefore(next: Tree)(codegenAlt: Casegen): Tree = {
         atPos(pos){
           // one alternative may still generate multiple trees (e.g., an extractor call + equality test)
           // (for now,) alternatives may not bind variables (except wildcards), so we don't care about the final substitution built internally by makeTreeMakers
@@ -587,18 +581,18 @@ trait MatchTreeMaking extends MatchCodeGen with Debugging {
         t match {
           case Function(_, _) if t.symbol == NoSymbol =>
             t.symbol = currentOwner.newAnonymousFunctionValue(t.pos)
-            debug.patmat("new symbol for "+ (t, t.symbol.ownerChain))
+            debug.patmat("new symbol for "+ ((t, t.symbol.ownerChain)))
           case Function(_, _) if (t.symbol.owner == NoSymbol) || (t.symbol.owner == origOwner) =>
-            debug.patmat("fundef: "+ (t, t.symbol.ownerChain, currentOwner.ownerChain))
+            debug.patmat("fundef: "+ ((t, t.symbol.ownerChain, currentOwner.ownerChain)))
             t.symbol.owner = currentOwner
           case d : DefTree if (d.symbol != NoSymbol) && ((d.symbol.owner == NoSymbol) || (d.symbol.owner == origOwner)) => // don't indiscriminately change existing owners! (see e.g., pos/t3440, pos/t3534, pos/unapplyContexts2)
-            debug.patmat("def: "+ (d, d.symbol.ownerChain, currentOwner.ownerChain))
+            debug.patmat("def: "+ ((d, d.symbol.ownerChain, currentOwner.ownerChain)))
             if(d.symbol.moduleClass ne NoSymbol)
               d.symbol.moduleClass.owner = currentOwner
 
             d.symbol.owner = currentOwner
           // case _ if (t.symbol != NoSymbol) && (t.symbol ne null) =>
-          debug.patmat("untouched "+ (t, t.getClass, t.symbol.ownerChain, currentOwner.ownerChain))
+          debug.patmat("untouched "+ ((t, t.getClass, t.symbol.ownerChain, currentOwner.ownerChain)))
           case _ =>
         }
         super.traverse(t)
@@ -611,4 +605,4 @@ trait MatchTreeMaking extends MatchCodeGen with Debugging {
       // currentRun.trackerFactory.snapshot()
     }
   }
-}
\ No newline at end of file
+}
diff --git a/src/compiler/scala/tools/nsc/transform/patmat/Solving.scala b/src/compiler/scala/tools/nsc/transform/patmat/Solving.scala
index 34cdbeba8e..a0fb6e82fc 100644
--- a/src/compiler/scala/tools/nsc/transform/patmat/Solving.scala
+++ b/src/compiler/scala/tools/nsc/transform/patmat/Solving.scala
@@ -13,13 +13,6 @@ import scala.reflect.internal.util.Statistics
 trait Solving extends Logic {
   import PatternMatchingStats._
   trait CNF extends PropositionalLogic {
-
-    /** Override Array creation for efficiency (to not go through reflection). */
-    private implicit val clauseTag: scala.reflect.ClassTag[Clause] = new scala.reflect.ClassTag[Clause] {
-      def runtimeClass: java.lang.Class[Clause] = classOf[Clause]
-      final override def newArray(len: Int): Array[Clause] = new Array[Clause](len)
-    }
-
     import scala.collection.mutable.ArrayBuffer
     type FormulaBuilder = ArrayBuffer[Clause]
     def formulaBuilder  = ArrayBuffer[Clause]()
diff --git a/src/compiler/scala/tools/nsc/typechecker/ContextErrors.scala b/src/compiler/scala/tools/nsc/typechecker/ContextErrors.scala
index 0af75a2aad..8723046728 100644
--- a/src/compiler/scala/tools/nsc/typechecker/ContextErrors.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/ContextErrors.scala
@@ -20,7 +20,6 @@ trait ContextErrors {
 
   import global._
   import definitions._
-  import treeInfo._
 
   object ErrorKinds extends Enumeration {
     type ErrorKind = Value
@@ -173,8 +172,7 @@ trait ContextErrors {
         assert(!foundType.isErroneous && !req.isErroneous, (foundType, req))
 
         issueNormalTypeError(tree, withAddendum(tree.pos)(typeErrorMsg(foundType, req, infer.isPossiblyMissingArgs(foundType, req))) )
-        if (settings.explaintypes.value)
-          explainTypes(foundType, req)
+        infer.explainTypes(foundType, req)
       }
 
       def WithFilterError(tree: Tree, ex: AbsTypeError) = {
@@ -302,7 +300,7 @@ trait ContextErrors {
           val target           = qual.tpe.widen
           def targetKindString = if (owner.isTypeParameterOrSkolem) "type parameter " else ""
           def nameString       = decodeWithKind(name, owner)
-          /** Illuminating some common situations and errors a bit further. */
+          /* Illuminating some common situations and errors a bit further. */
           def addendum         = {
             val companion = {
               if (name.isTermName && owner.isPackageClass) {
@@ -1274,11 +1272,12 @@ trait ContextErrors {
     // not exactly an error generator, but very related
     // and I dearly wanted to push it away from Macros.scala
     private def checkSubType(slot: String, rtpe: Type, atpe: Type) = {
-      val ok = if (macroDebugVerbose || settings.explaintypes.value) {
-        if (rtpe eq atpe) println(rtpe + " <: " + atpe + "?" + EOL + "true")
+      val ok = if (macroDebugVerbose) {
         withTypesExplained(rtpe <:< atpe)
       } else rtpe <:< atpe
       if (!ok) {
+        if (!macroDebugVerbose)
+          explainTypes(rtpe, atpe)
         compatibilityError("type mismatch for %s: %s does not conform to %s".format(slot, abbreviateCoreAliases(rtpe.toString), abbreviateCoreAliases(atpe.toString)))
       }
     }
diff --git a/src/compiler/scala/tools/nsc/typechecker/Contexts.scala b/src/compiler/scala/tools/nsc/typechecker/Contexts.scala
index 429bd7d682..9d5a9c819c 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Contexts.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Contexts.scala
@@ -532,7 +532,7 @@ trait Contexts { self: Analyzer =>
         case _ => false
       }
 
-      /** Is protected access to target symbol permitted */
+      /* Is protected access to target symbol permitted */
       def isProtectedAccessOK(target: Symbol) = {
         val c = enclosingSubClassContext(sym.owner)
         if (c == NoContext)
@@ -594,11 +594,11 @@ trait Contexts { self: Analyzer =>
       def restore(): Type = savedTypeBounds.foldLeft(tp) { case (current, (sym, savedInfo)) =>
         def bounds_s(tb: TypeBounds) = if (tb.isEmptyBounds) "<empty bounds>" else s"TypeBounds(lo=${tb.lo}, hi=${tb.hi})"
         //@M TODO: when higher-kinded types are inferred, probably need a case PolyType(_, TypeBounds(...)) if ... =>
-        val tb @ TypeBounds(lo, hi) = sym.info.bounds
-        val isUnique                = lo <:< hi && hi <:< lo
-        val isPresent               = current contains sym
-        def saved_s                 = bounds_s(savedInfo.bounds)
-        def current_s               = bounds_s(sym.info.bounds)
+        val TypeBounds(lo, hi) = sym.info.bounds
+        val isUnique           = lo <:< hi && hi <:< lo
+        val isPresent          = current contains sym
+        def saved_s            = bounds_s(savedInfo.bounds)
+        def current_s          = bounds_s(sym.info.bounds)
 
         if (isUnique && isPresent)
           devWarningResult(s"Preserving inference: ${sym.nameString}=$hi in $current (based on $current_s) before restoring $sym to saved $saved_s")(
@@ -962,15 +962,15 @@ trait Contexts { self: Analyzer =>
           // import check from being misled by symbol lookups which are not
           // actually used.
           val other = lookupImport(imp2, requireExplicit = !sameDepth)
-          def imp1wins = { imports = imp1 :: imports.tail.tail }
-          def imp2wins = { impSym = other ; imports = imports.tail }
+          def imp1wins() = { imports = imp1 :: imports.tail.tail }
+          def imp2wins() = { impSym = other ; imports = imports.tail }
 
           if (!other.exists) // imp1 wins; drop imp2 and continue.
-            imp1wins
+            imp1wins()
           else if (sameDepth && !imp1Explicit && imp2Explicit) // imp2 wins; drop imp1 and continue.
-            imp2wins
+            imp2wins()
           else resolveAmbiguousImport(name, imp1, imp2) match {
-            case Some(imp) => if (imp eq imp1) imp1wins else imp2wins
+            case Some(imp) => if (imp eq imp1) imp1wins() else imp2wins()
             case _         => lookupError = ambiguousImports(imp1, imp2)
           }
         }
diff --git a/src/compiler/scala/tools/nsc/typechecker/Duplicators.scala b/src/compiler/scala/tools/nsc/typechecker/Duplicators.scala
index ad45fc0354..b9e4b4f591 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Duplicators.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Duplicators.scala
@@ -80,7 +80,7 @@ abstract class Duplicators extends Analyzer {
             BodyDuplicator.super.silent(_.typedType(Ident(sym.name))) match {
               case SilentResultValue(t) =>
                 sym1 = t.symbol
-                debuglog("fixed by trying harder: "+(sym, sym1, context))
+                debuglog("fixed by trying harder: "+((sym, sym1, context)))
               case _ =>
             }
           }
diff --git a/src/compiler/scala/tools/nsc/typechecker/EtaExpansion.scala b/src/compiler/scala/tools/nsc/typechecker/EtaExpansion.scala
index 80dfef6c7b..282dd8a99d 100644
--- a/src/compiler/scala/tools/nsc/typechecker/EtaExpansion.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/EtaExpansion.scala
@@ -56,8 +56,8 @@ trait EtaExpansion { self: Analyzer =>
     }
     val defs = new ListBuffer[Tree]
 
-    /** Append to `defs` value definitions for all non-stable
-     *  subexpressions of the function application `tree`.
+    /* Append to `defs` value definitions for all non-stable
+     * subexpressions of the function application `tree`.
      */
     def liftoutPrefix(tree: Tree): Tree = {
       def liftout(tree: Tree, byName: Boolean): Tree =
@@ -106,8 +106,7 @@ trait EtaExpansion { self: Analyzer =>
       tree1
     }
 
-    /** Eta-expand lifted tree.
-     */
+    /* Eta-expand lifted tree. */
     def expand(tree: Tree, tpe: Type): Tree = tpe match {
       case mt @ MethodType(paramSyms, restpe) if !mt.isImplicit =>
         val params: List[(ValDef, Boolean)] = paramSyms.map {
diff --git a/src/compiler/scala/tools/nsc/typechecker/Implicits.scala b/src/compiler/scala/tools/nsc/typechecker/Implicits.scala
index 2331f82a58..8f52088b19 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Implicits.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Implicits.scala
@@ -268,7 +268,7 @@ trait Implicits {
    */
   object Function1 {
     val Sym = FunctionClass(1)
-    def unapply(tp: Type) = tp match {
+    def unapply(tp: Type) = tp baseType Sym match {
       case TypeRef(_, Sym, arg1 :: arg2 :: _) => Some((arg1, arg2))
       case _                                  => None
     }
@@ -311,7 +311,7 @@ trait Implicits {
       (info2 == NoImplicitInfo) ||
       (info1 != NoImplicitInfo) && {
         if (info1.sym.isStatic && info2.sym.isStatic) {
-          improvesCache get (info1, info2) match {
+          improvesCache get ((info1, info2)) match {
             case Some(b) => if (Statistics.canEnable) Statistics.incCounter(improvesCachedCount); b
             case None =>
               val result = isStrictlyMoreSpecific(info1.tpe, info2.tpe, info1.sym, info2.sym)
@@ -431,10 +431,8 @@ trait Implicits {
       val start = if (Statistics.canEnable) Statistics.startTimer(matchesPtNanos) else null
       val result = normSubType(tp, pt) || isView && {
         pt match {
-          case TypeRef(_, Function1.Sym, arg1 :: arg2 :: Nil) =>
-            matchesPtView(tp, arg1, arg2, undet)
-          case _ =>
-            false
+          case Function1(arg1, arg2) => matchesPtView(tp, arg1, arg2, undet)
+          case _                     => false
         }
       }
       if (Statistics.canEnable) Statistics.stopTimer(matchesPtNanos, start)
@@ -575,21 +573,21 @@ trait Implicits {
       )
 
       def fail(reason: String): SearchResult = failure(itree, reason)
+      def fallback = typed1(itree, EXPRmode, wildPt)
       try {
-        val itree1 =
-          if (isView) {
-            val arg1 :: arg2 :: _ = pt.typeArgs
+        val itree1 = if (!isView) fallback else pt match {
+          case Function1(arg1, arg2) =>
             typed1(
               atPos(itree.pos)(Apply(itree, List(Ident("<argument>") setType approximate(arg1)))),
               EXPRmode,
               approximate(arg2)
             )
-          }
-          else
-            typed1(itree, EXPRmode, wildPt)
-
-        if (context.hasErrors)
+          case _ => fallback
+        }
+        if (context.hasErrors) {
+          log("implicit adapt failed: " + context.errBuffer.head.errMsg)
           return fail(context.errBuffer.head.errMsg)
+        }
 
         if (Statistics.canEnable) Statistics.incCounter(typedImplicits)
 
@@ -875,8 +873,8 @@ trait Implicits {
         }
 
         if (best.isFailure) {
-          /** If there is no winner, and we witnessed and caught divergence,
-           *  now we can throw it for the error message.
+          /* If there is no winner, and we witnessed and caught divergence,
+           * now we can throw it for the error message.
            */
           if (divergence)
             throw DivergentImplicit
@@ -936,8 +934,8 @@ trait Implicits {
      */
     private def companionImplicitMap(tp: Type): InfoMap = {
 
-      /** Populate implicit info map by traversing all parts of type `tp`.
-       *  Parameters as for `getParts`.
+      /* Populate implicit info map by traversing all parts of type `tp`.
+       * Parameters as for `getParts`.
        */
       def getClassParts(tp: Type)(implicit infoMap: InfoMap, seen: mutable.Set[Type], pending: Set[Symbol]) = tp match {
         case TypeRef(pre, sym, args) =>
@@ -969,13 +967,13 @@ trait Implicits {
             }
       }
 
-      /** Populate implicit info map by traversing all parts of type `tp`.
-       *  This method is performance critical.
-       *  @param tp   The type for which we want to traverse parts
-       *  @param infoMap  The infoMap in which implicit infos corresponding to parts are stored
-       *  @param seen     The types that were already visited previously when collecting parts for the given infoMap
-       *  @param pending  The set of static symbols for which we are currently trying to collect their parts
-       *                  in order to cache them in infoMapCache
+      /* Populate implicit info map by traversing all parts of type `tp`.
+       * This method is performance critical.
+       * @param tp   The type for which we want to traverse parts
+       * @param infoMap  The infoMap in which implicit infos corresponding to parts are stored
+       * @param seen     The types that were already visited previously when collecting parts for the given infoMap
+       * @param pending  The set of static symbols for which we are currently trying to collect their parts
+       *                 in order to cache them in infoMapCache
        */
       def getParts(tp: Type)(implicit infoMap: InfoMap, seen: mutable.Set[Type], pending: Set[Symbol]) {
         if (seen(tp))
@@ -1138,7 +1136,7 @@ trait Implicits {
       val full = flavor == FullManifestClass
       val opt = flavor == OptManifestClass
 
-      /** Creates a tree that calls the factory method called constructor in object scala.reflect.Manifest */
+      /* Creates a tree that calls the factory method called constructor in object scala.reflect.Manifest */
       def manifestFactoryCall(constructor: String, tparg: Type, args: Tree*): Tree =
         if (args contains EmptyTree) EmptyTree
         else typedPos(tree.pos.focus) {
@@ -1147,12 +1145,12 @@ trait Implicits {
           mani
         }
 
-      /** Creates a tree representing one of the singleton manifests.*/
+      /* Creates a tree representing one of the singleton manifests.*/
       def findSingletonManifest(name: String) = typedPos(tree.pos.focus) {
         Select(gen.mkAttributedRef(FullManifestModule), name)
       }
 
-      /** Re-wraps a type in a manifest before calling inferImplicit on the result */
+      /* Re-wraps a type in a manifest before calling inferImplicit on the result */
       def findManifest(tp: Type, manifestClass: Symbol = if (full) FullManifestClass else PartialManifestClass) =
         inferImplicit(tree, appliedType(manifestClass, tp), reportAmbiguous = true, isView = false, context).tree
 
diff --git a/src/compiler/scala/tools/nsc/typechecker/Infer.scala b/src/compiler/scala/tools/nsc/typechecker/Infer.scala
index 9f16f65a6a..495ac1c086 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Infer.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Infer.scala
@@ -304,17 +304,18 @@ trait Infer extends Checkable {
 
     def isPossiblyMissingArgs(found: Type, req: Type) = (
       false
-      /** However it is that this condition is expected to imply
-       *  "is possibly missing args", it is too weak.  It is
-       *  better to say nothing than to offer misleading guesses.
+      /* However it is that this condition is expected to imply
+       * "is possibly missing args", it is too weak.  It is
+       * better to say nothing than to offer misleading guesses.
 
-         (found.resultApprox ne found)
-      && isWeaklyCompatible(found.resultApprox, req)
+       * (found.resultApprox ne found) && isWeaklyCompatible(found.resultApprox, req)
       */
     )
 
-    def explainTypes(tp1: Type, tp2: Type) =
-      withDisambiguation(List(), tp1, tp2)(global.explainTypes(tp1, tp2))
+    def explainTypes(tp1: Type, tp2: Type) = {
+      if (context.reportErrors)
+        withDisambiguation(List(), tp1, tp2)(global.explainTypes(tp1, tp2))
+    }
 
     /* -- Tests & Checks---------------------------------------------------- */
 
@@ -509,8 +510,8 @@ trait Infer extends Checkable {
     */
     def protoTypeArgs(tparams: List[Symbol], formals: List[Type], restpe: Type,
                       pt: Type): List[Type] = {
-      /** Map type variable to its instance, or, if `variance` is covariant/contravariant,
-       *  to its upper/lower bound */
+      /* Map type variable to its instance, or, if `variance` is covariant/contravariant,
+       * to its upper/lower bound */
       def instantiateToBound(tvar: TypeVar, variance: Variance): Type = {
         lazy val hiBounds = tvar.constr.hiBounds
         lazy val loBounds = tvar.constr.loBounds
@@ -1250,8 +1251,7 @@ trait Infer extends Checkable {
 
       debuglog("infer constr inst "+ tree +"/"+ undetparams +"/ pt= "+ pt +" pt0= "+ pt0 +" resTp: "+ resTp)
 
-      /** Compute type arguments for undetermined params
-       */
+      /* Compute type arguments for undetermined params */
       def inferFor(pt: Type): Option[List[Type]] = {
         val tvars   = undetparams map freshVar
         val resTpV  = resTp.instantiateTypeParams(undetparams, tvars)
@@ -1269,7 +1269,7 @@ trait Infer extends Checkable {
             // TODO: reinstate checkBounds, return params that fail to meet their bounds to undetparams
             Some(targs)
           } catch ifNoInstance { msg =>
-            debuglog("NO INST "+ (tvars, tvars map (_.constr)))
+            debuglog("NO INST "+ ((tvars, tvars map (_.constr))))
             NoConstructorInstanceError(tree, resTp, pt, msg)
             None
           }
@@ -1384,9 +1384,9 @@ trait Infer extends Checkable {
       def ptMatchesPattp = pt matchesPattern pattp.widen
       def pattpMatchesPt = pattp matchesPattern pt
 
-      /** If we can absolutely rule out a match we can fail early.
-       *  This is the case if the scrutinee has no unresolved type arguments
-       *  and is a "final type", meaning final + invariant in all type parameters.
+      /* If we can absolutely rule out a match we can fail early.
+       * This is the case if the scrutinee has no unresolved type arguments
+       * and is a "final type", meaning final + invariant in all type parameters.
        */
       if (pt.isFinalType && ptparams.isEmpty && !ptMatchesPattp) {
         IncompatibleScrutineeTypeError(tree0, pattp, pt)
@@ -1422,9 +1422,9 @@ trait Infer extends Checkable {
         }
         tvars foreach instantiateTypeVar
       }
-      /** If the scrutinee has free type parameters but the pattern does not,
-       *  we have to flip the arguments so the expected type is treated as more
-       *  general when calculating the intersection.  See run/bug2755.scala.
+      /* If the scrutinee has free type parameters but the pattern does not,
+       * we have to flip the arguments so the expected type is treated as more
+       * general when calculating the intersection.  See run/bug2755.scala.
        */
       if (tpparams.isEmpty && ptparams.nonEmpty) intersect(pattp, pt)
       else intersect(pt, pattp)
diff --git a/src/compiler/scala/tools/nsc/typechecker/Macros.scala b/src/compiler/scala/tools/nsc/typechecker/Macros.scala
index 91ebd798e1..2dbfa1d0d3 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Macros.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Macros.scala
@@ -189,7 +189,7 @@ trait Macros extends scala.tools.reflect.FastTrack with Traces {
       val payload = pickledPayload.map{ case Assign(k, v) => (unpickleAtom(k), unpickleAtom(v)) }.toMap
 
       val pickleVersionFormat = payload("versionFormat").asInstanceOf[Int]
-      if (versionFormat != pickleVersionFormat) throw new Error("macro impl binding format mismatch: expected $versionFormat, actual $pickleVersionFormat")
+      if (versionFormat != pickleVersionFormat) throw new Error(s"macro impl binding format mismatch: expected $versionFormat, actual $pickleVersionFormat")
 
       val className = payload("className").asInstanceOf[String]
       val methodName = payload("methodName").asInstanceOf[String]
diff --git a/src/compiler/scala/tools/nsc/typechecker/MethodSynthesis.scala b/src/compiler/scala/tools/nsc/typechecker/MethodSynthesis.scala
index 8c686107b4..5999a64b36 100644
--- a/src/compiler/scala/tools/nsc/typechecker/MethodSynthesis.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/MethodSynthesis.scala
@@ -426,7 +426,7 @@ trait MethodSynthesis {
             Nil,
             Nil,
             tpt,
-            if (mods.isDeferred) EmptyTree else gen.mkCheckInit(fieldSelection)
+            if (mods.isDeferred) EmptyTree else fieldSelection
           ) setSymbol derivedSym
         }
       }
diff --git a/src/compiler/scala/tools/nsc/typechecker/Namers.scala b/src/compiler/scala/tools/nsc/typechecker/Namers.scala
index 007c7c6a83..e966cc9060 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Namers.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Namers.scala
@@ -554,8 +554,8 @@ trait Namers extends MethodSynthesis {
       val sym      = copyDef.symbol
       val lazyType = completerOf(copyDef)
 
-      /** Assign the types of the class parameters to the parameters of the
-       *  copy method. See comment in `Unapplies.caseClassCopyMeth` */
+      /* Assign the types of the class parameters to the parameters of the
+       * copy method. See comment in `Unapplies.caseClassCopyMeth` */
       def assignParamTypes() {
         val clazz = sym.owner
         val constructorType = clazz.primaryConstructor.tpe
@@ -805,23 +805,19 @@ trait Namers extends MethodSynthesis {
         case _ =>
           false
       }
-
-      val tpe1 = dropIllegalStarTypes(tpe.deconst)
-      val tpe2 = tpe1.widen
-
-      // This infers Foo.type instead of "object Foo"
-      // See Infer#adjustTypeArgs for the polymorphic case.
-      if (tpe.typeSymbolDirect.isModuleClass) tpe1
-      else if (sym.isVariable || sym.isMethod && !sym.hasAccessorFlag)
-        if (tpe2 <:< pt) tpe2 else tpe1
-      else if (isHidden(tpe)) tpe2
-      // In an attempt to make pattern matches involving method local vals
-      // compilable into switches, for a time I had a more generous condition:
-      //    `if (sym.isFinal || sym.isLocal) tpe else tpe1`
-      // This led to issues with expressions like classOf[List[_]] which apparently
-      // depend on being deconst-ed here, so this is again the original:
-      else if (!sym.isFinal) tpe1
-      else tpe
+      val shouldWiden = (
+           !tpe.typeSymbolDirect.isModuleClass // Infer Foo.type instead of "object Foo"
+        && (tpe.widen <:< pt)                  // Don't widen our way out of conforming to pt
+        && (   sym.isVariable
+            || sym.isMethod && !sym.hasAccessorFlag
+            || isHidden(tpe)
+           )
+      )
+      dropIllegalStarTypes(
+        if (shouldWiden) tpe.widen
+        else if (sym.isFinal) tpe    // "final val" allowed to retain constant type
+        else tpe.deconst
+      )
     }
     /** Computes the type of the body in a ValDef or DefDef, and
      *  assigns the type to the tpt's node.  Returns the type.
@@ -989,7 +985,7 @@ trait Namers extends MethodSynthesis {
       var vparamSymss = enterValueParams(vparamss)
 
 
-      /**
+      /*
        * Creates a method type using tparamSyms and vparamsSymss as argument symbols and `respte` as result type.
        * All typeRefs to type skolems are replaced by references to the corresponding non-skolem type parameter,
        * so the resulting type is a valid external method type, it does not contain (references to) skolems.
@@ -1023,7 +1019,7 @@ trait Namers extends MethodSynthesis {
         res.substSym(tparamSkolems, tparamSyms)
       }
 
-      /**
+      /*
        * Creates a schematic method type which has WildcardTypes for non specified
        * return or parameter types. For instance, in `def f[T](a: T, b) = ...`, the
        * type schema is
@@ -1047,7 +1043,7 @@ trait Namers extends MethodSynthesis {
       // def overriddenSymbol = meth.nextOverriddenSymbol
 
 
-      /**
+      /*
        * If `meth` doesn't have an explicit return type, extracts the return type from the method
        * overridden by `meth` (if there's an unique one). This type is lateron used as the expected
        * type for computing the type of the rhs. The resulting type references type skolems for
@@ -1391,12 +1387,12 @@ trait Namers extends MethodSynthesis {
      */
     def typeSig(tree: Tree): Type = {
       // log("typeSig " + tree)
-      /** For definitions, transform Annotation trees to AnnotationInfos, assign
-       *  them to the sym's annotations. Type annotations: see Typer.typedAnnotated
-       *  We have to parse definition annotations here (not in the typer when traversing
-       *  the MemberDef tree): the typer looks at annotations of certain symbols; if
-       *  they were added only in typer, depending on the compilation order, they may
-       *  or may not be visible.
+      /* For definitions, transform Annotation trees to AnnotationInfos, assign
+       * them to the sym's annotations. Type annotations: see Typer.typedAnnotated
+       * We have to parse definition annotations here (not in the typer when traversing
+       * the MemberDef tree): the typer looks at annotations of certain symbols; if
+       * they were added only in typer, depending on the compilation order, they may
+       * or may not be visible.
        */
       def annotate(annotated: Symbol) = {
         // typeSig might be called multiple times, e.g. on a ValDef: val, getter, setter
diff --git a/src/compiler/scala/tools/nsc/typechecker/NamesDefaults.scala b/src/compiler/scala/tools/nsc/typechecker/NamesDefaults.scala
index ce8e0ed37b..d5ecb687b0 100644
--- a/src/compiler/scala/tools/nsc/typechecker/NamesDefaults.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/NamesDefaults.scala
@@ -111,7 +111,7 @@ trait NamesDefaults { self: Analyzer =>
     val context = typer.context
     import context.unit
 
-    /**
+    /*
      * Transform a function into a block, and passing context.namedApplyBlockInfo to
      * the new block as side-effect.
      *
@@ -256,7 +256,7 @@ trait NamesDefaults { self: Analyzer =>
       }
     }
 
-    /**
+    /*
      * For each argument (arg: T), create a local value
      *  x$n: T = arg
      *
diff --git a/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala b/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala
index b7221a78ec..40428272cf 100644
--- a/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/RefChecks.scala
@@ -281,8 +281,8 @@ abstract class RefChecks extends InfoTransform with scala.reflect.internal.trans
          else "")
       }
 
-      /** Check that all conditions for overriding `other` by `member`
-       *  of class `clazz` are met.
+      /* Check that all conditions for overriding `other` by `member`
+       * of class `clazz` are met.
        */
       def checkOverride(member: Symbol, other: Symbol) {
         debuglog("Checking validity of %s overriding %s".format(member.fullLocationString, other.fullLocationString))
@@ -361,8 +361,7 @@ abstract class RefChecks extends InfoTransform with scala.reflect.internal.trans
           }
         }
 
-        /** Is the intersection between given two lists of overridden symbols empty?
-         */
+        /* Is the intersection between given two lists of overridden symbols empty? */
         def intersectionIsEmpty(syms1: List[Symbol], syms2: List[Symbol]) =
           !(syms1 exists (syms2 contains _))
 
@@ -736,9 +735,9 @@ abstract class RefChecks extends InfoTransform with scala.reflect.internal.trans
         }
       }
 
-      /** Returns whether there is a symbol declared in class `inclazz`
-       *  (which must be different from `clazz`) whose name and type
-       *  seen as a member of `class.thisType` matches `member`'s.
+      /* Returns whether there is a symbol declared in class `inclazz`
+       * (which must be different from `clazz`) whose name and type
+       * seen as a member of `class.thisType` matches `member`'s.
        */
       def hasMatchingSym(inclazz: Symbol, member: Symbol): Boolean = {
         val isVarargs = hasRepeatedParam(member.tpe)
@@ -750,22 +749,22 @@ abstract class RefChecks extends InfoTransform with scala.reflect.internal.trans
 
           matches(member.tpe) || (isVarargs && matches(varargsType))
         }
-        /** The rules for accessing members which have an access boundary are more
-         *  restrictive in java than scala.  Since java has no concept of package nesting,
-         *  a member with "default" (package-level) access can only be accessed by members
-         *  in the exact same package.  Example:
+        /* The rules for accessing members which have an access boundary are more
+         * restrictive in java than scala.  Since java has no concept of package nesting,
+         * a member with "default" (package-level) access can only be accessed by members
+         * in the exact same package.  Example:
          *
-         *    package a.b;
-         *    public class JavaClass { void foo() { } }
+         *   package a.b;
+         *   public class JavaClass { void foo() { } }
          *
-         *  The member foo() can be accessed only from members of package a.b, and not
-         *  nested packages like a.b.c.  In the analogous scala class:
+         * The member foo() can be accessed only from members of package a.b, and not
+         * nested packages like a.b.c.  In the analogous scala class:
          *
-         *    package a.b
-         *    class ScalaClass { private[b] def foo() = () }
+         *   package a.b
+         *   class ScalaClass { private[b] def foo() = () }
          *
-         *  The member IS accessible to classes in package a.b.c.  The javaAccessCheck logic
-         *  is restricting the set of matching signatures according to the above semantics.
+         * The member IS accessible to classes in package a.b.c.  The javaAccessCheck logic
+         * is restricting the set of matching signatures according to the above semantics.
          */
         def javaAccessCheck(sym: Symbol) = (
              !inclazz.isJavaDefined                             // not a java defined member
@@ -812,7 +811,7 @@ abstract class RefChecks extends InfoTransform with scala.reflect.internal.trans
       for (i <- 0 until seenTypes.length)
         seenTypes(i) = Nil
 
-      /** validate all base types of a class in reverse linear order. */
+      /* validate all base types of a class in reverse linear order. */
       def register(tp: Type): Unit = {
 //        if (clazz.fullName.endsWith("Collection.Projection"))
 //            println("validate base type "+tp)
@@ -948,7 +947,7 @@ abstract class RefChecks extends InfoTransform with scala.reflect.internal.trans
         // @MAT normalize for consistency in error message, otherwise only part is normalized due to use of `typeSymbol`
         def typesString = normalizeAll(qual.tpe.widen)+" and "+normalizeAll(args.head.tpe.widen)
 
-        /** Symbols which limit the warnings we can issue since they may be value types */
+        /* Symbols which limit the warnings we can issue since they may be value types */
         val isMaybeValue = Set[Symbol](AnyClass, AnyRefClass, AnyValClass, ObjectClass, ComparableClass, JavaSerializableClass)
 
         // Whether def equals(other: Any) has known behavior: it is the default
@@ -1124,7 +1123,7 @@ abstract class RefChecks extends InfoTransform with scala.reflect.internal.trans
      *     accessor for that field. The instance is created lazily, on first access.
      */
     private def eliminateModuleDefs(moduleDef: Tree): List[Tree] = exitingRefchecks {
-      val ModuleDef(mods, name, impl) = moduleDef
+      val ModuleDef(_, _, impl) = moduleDef
       val module        = moduleDef.symbol
       val site          = module.owner
       val moduleName    = module.name.toTermName
@@ -1455,11 +1454,11 @@ abstract class RefChecks extends InfoTransform with scala.reflect.internal.trans
       val Select(qual, _) = tree
       val sym = tree.symbol
 
-      /** Note: if a symbol has both @deprecated and @migration annotations and both
-       *  warnings are enabled, only the first one checked here will be emitted.
-       *  I assume that's a consequence of some code trying to avoid noise by suppressing
-       *  warnings after the first, but I think it'd be better if we didn't have to
-       *  arbitrarily choose one as more important than the other.
+      /* Note: if a symbol has both @deprecated and @migration annotations and both
+       * warnings are enabled, only the first one checked here will be emitted.
+       * I assume that's a consequence of some code trying to avoid noise by suppressing
+       * warnings after the first, but I think it'd be better if we didn't have to
+       * arbitrarily choose one as more important than the other.
        */
       checkDeprecated(sym, tree.pos)
       if(settings.Xmigration.value != NoScalaVersion)
@@ -1485,7 +1484,7 @@ abstract class RefChecks extends InfoTransform with scala.reflect.internal.trans
     private def transformIf(tree: If): Tree = {
       val If(cond, thenpart, elsepart) = tree
       def unitIfEmpty(t: Tree): Tree =
-        if (t == EmptyTree) Literal(Constant()).setPos(tree.pos).setType(UnitClass.tpe) else t
+        if (t == EmptyTree) Literal(Constant(())).setPos(tree.pos).setType(UnitClass.tpe) else t
 
       cond.tpe match {
         case ConstantType(value) =>
@@ -1553,6 +1552,8 @@ abstract class RefChecks extends InfoTransform with scala.reflect.internal.trans
             val bridges = addVarargBridges(currentOwner)
             checkAllOverrides(currentOwner)
             checkAnyValSubclass(currentOwner)
+            if (currentOwner.isDerivedValueClass)
+              currentOwner.primaryConstructor makeNotPrivate NoSymbol // SI-6601, must be done *after* pickler!
             if (bridges.nonEmpty) deriveTemplate(tree)(_ ::: bridges) else tree
 
           case dc@TypeTreeWithDeferredRefCheck() => abort("adapt should have turned dc: TypeTreeWithDeferredRefCheck into tpt: TypeTree, with tpt.original == dc")
diff --git a/src/compiler/scala/tools/nsc/typechecker/SuperAccessors.scala b/src/compiler/scala/tools/nsc/typechecker/SuperAccessors.scala
index e8925ce2d0..c967fed0b9 100644
--- a/src/compiler/scala/tools/nsc/typechecker/SuperAccessors.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/SuperAccessors.scala
@@ -1,3 +1,4 @@
+
 /* NSC -- new Scala compiler
  * Copyright 2005-2013 LAMP/EPFL
  * @author Martin Odersky
@@ -264,7 +265,7 @@ abstract class SuperAccessors extends transform.Transform with transform.TypingT
                 debuglog("alias replacement: " + tree + " ==> " + result); //debug
                 localTyper.typed(gen.maybeMkAsInstanceOf(transformSuperSelect(result), sym.tpe, sym.alias.tpe, beforeRefChecks = true))
               } else {
-                /**
+                /*
                  * A trait which extends a class and accesses a protected member
                  *  of that class cannot implement the necessary accessor method
                  *  because its implementation is in an implementation class (e.g.
diff --git a/src/compiler/scala/tools/nsc/typechecker/SyntheticMethods.scala b/src/compiler/scala/tools/nsc/typechecker/SyntheticMethods.scala
index a2b0530c26..5dc422bc1a 100644
--- a/src/compiler/scala/tools/nsc/typechecker/SyntheticMethods.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/SyntheticMethods.scala
@@ -126,8 +126,7 @@ trait SyntheticMethods extends ast.TreeDSL {
       )
     }
 
-    /** Common code for productElement and (currently disabled) productElementName
-     */
+    /* Common code for productElement and (currently disabled) productElementName */
     def perElementMethod(name: Name, returnType: Type)(caseFn: Symbol => Tree): Tree =
       createSwitchMethod(name, accessors.indices, returnType)(idx => caseFn(accessors(idx)))
 
@@ -135,8 +134,8 @@ trait SyntheticMethods extends ast.TreeDSL {
 
     var syntheticCanEqual = false
 
-    /** The canEqual method for case classes.
-     *    def canEqual(that: Any) = that.isInstanceOf[This]
+    /* The canEqual method for case classes.
+     *   def canEqual(that: Any) = that.isInstanceOf[This]
      */
     def canEqualMethod: Tree = {
       syntheticCanEqual = true
@@ -144,13 +143,13 @@ trait SyntheticMethods extends ast.TreeDSL {
         Ident(m.firstParam) IS_OBJ classExistentialType(clazz))
     }
 
-    /** that match { case _: this.C => true ; case _ => false }
-     *  where `that` is the given method's first parameter.
+    /* that match { case _: this.C => true ; case _ => false }
+     * where `that` is the given method's first parameter.
      *
-     *  An isInstanceOf test is insufficient because it has weaker
-     *  requirements than a pattern match. Given an inner class Foo and
-     *  two different instantiations of the container, an x.Foo and and a y.Foo
-     *  are both .isInstanceOf[Foo], but the one does not match as the other.
+     * An isInstanceOf test is insufficient because it has weaker
+     * requirements than a pattern match. Given an inner class Foo and
+     * two different instantiations of the container, an x.Foo and and a y.Foo
+     * are both .isInstanceOf[Foo], but the one does not match as the other.
      */
     def thatTest(eqmeth: Symbol): Tree = {
       Match(
@@ -162,19 +161,19 @@ trait SyntheticMethods extends ast.TreeDSL {
       )
     }
 
-    /** (that.asInstanceOf[this.C])
-     *  where that is the given methods first parameter.
+    /* (that.asInstanceOf[this.C])
+     * where that is the given methods first parameter.
      */
     def thatCast(eqmeth: Symbol): Tree =
       gen.mkCast(Ident(eqmeth.firstParam), clazz.tpe)
 
-    /** The equality method core for case classes and inline clases.
-     *  1+ args:
-     *    (that.isInstanceOf[this.C]) && {
-     *        val x$1 = that.asInstanceOf[this.C]
-     *        (this.arg_1 == x$1.arg_1) && (this.arg_2 == x$1.arg_2) && ... && (x$1 canEqual this)
-     *       }
-     *  Drop canBuildFrom part if class is final and canBuildFrom is synthesized
+    /* The equality method core for case classes and inline clases.
+     * 1+ args:
+     *   (that.isInstanceOf[this.C]) && {
+     *       val x$1 = that.asInstanceOf[this.C]
+     *       (this.arg_1 == x$1.arg_1) && (this.arg_2 == x$1.arg_2) && ... && (x$1 canEqual this)
+     *      }
+     * Drop canBuildFrom part if class is final and canBuildFrom is synthesized
      */
     def equalsCore(eqmeth: Symbol, accessors: List[Symbol]) = {
       val otherName = context.unit.freshTermName(clazz.name + "$")
@@ -189,16 +188,16 @@ trait SyntheticMethods extends ast.TreeDSL {
       )
     }
 
-    /** The equality method for case classes.
-     *  0 args:
-     *    def equals(that: Any) = that.isInstanceOf[this.C] && that.asInstanceOf[this.C].canEqual(this)
-     *  1+ args:
-     *    def equals(that: Any) = (this eq that.asInstanceOf[AnyRef]) || {
-     *      (that.isInstanceOf[this.C]) && {
-     *        val x$1 = that.asInstanceOf[this.C]
-     *        (this.arg_1 == x$1.arg_1) && (this.arg_2 == x$1.arg_2) && ... && (x$1 canEqual this)
-     *       }
-     *    }
+    /* The equality method for case classes.
+     * 0 args:
+     *   def equals(that: Any) = that.isInstanceOf[this.C] && that.asInstanceOf[this.C].canEqual(this)
+     * 1+ args:
+     *   def equals(that: Any) = (this eq that.asInstanceOf[AnyRef]) || {
+     *     (that.isInstanceOf[this.C]) && {
+     *       val x$1 = that.asInstanceOf[this.C]
+     *       (this.arg_1 == x$1.arg_1) && (this.arg_2 == x$1.arg_2) && ... && (x$1 canEqual this)
+     *      }
+     *   }
      */
     def equalsCaseClassMethod: Tree = createMethod(nme.equals_, List(AnyClass.tpe), BooleanClass.tpe) { m =>
       if (accessors.isEmpty)
@@ -208,25 +207,25 @@ trait SyntheticMethods extends ast.TreeDSL {
         (mkThis ANY_EQ Ident(m.firstParam)) OR equalsCore(m, accessors)
     }
 
-    /** The equality method for value classes
-     *  def equals(that: Any) = (this.asInstanceOf[AnyRef]) eq that.asInstanceOf[AnyRef]) || {
-     *    (that.isInstanceOf[this.C]) && {
-     *     val x$1 = that.asInstanceOf[this.C]
-     *     (this.underlying == that.underlying
+    /* The equality method for value classes
+     * def equals(that: Any) = (this.asInstanceOf[AnyRef]) eq that.asInstanceOf[AnyRef]) || {
+     *   (that.isInstanceOf[this.C]) && {
+     *    val x$1 = that.asInstanceOf[this.C]
+     *    (this.underlying == that.underlying
      */
     def equalsDerivedValueClassMethod: Tree = createMethod(nme.equals_, List(AnyClass.tpe), BooleanClass.tpe) { m =>
       equalsCore(m, List(clazz.derivedValueClassUnbox))
     }
 
-    /** The hashcode method for value classes
+    /* The hashcode method for value classes
      * def hashCode(): Int = this.underlying.hashCode
      */
     def hashCodeDerivedValueClassMethod: Tree = createMethod(nme.hashCode_, Nil, IntClass.tpe) { m =>
       Select(mkThisSelect(clazz.derivedValueClassUnbox), nme.hashCode_)
     }
 
-    /** The _1, _2, etc. methods to implement ProductN, disabled
-     *  until we figure out how to introduce ProductN without cycles.
+    /* The _1, _2, etc. methods to implement ProductN, disabled
+     * until we figure out how to introduce ProductN without cycles.
      */
     /****
     def productNMethods = {
@@ -308,11 +307,11 @@ trait SyntheticMethods extends ast.TreeDSL {
       // Object_equals   -> (() => createMethod(Object_equals)(m => This(clazz) ANY_EQ Ident(m.firstParam)))
     )
 
-    /** If you serialize a singleton and then deserialize it twice,
-     *  you will have two instances of your singleton unless you implement
-     *  readResolve.  Here it is implemented for all objects which have
-     *  no implementation and which are marked serializable (which is true
-     *  for all case objects.)
+    /* If you serialize a singleton and then deserialize it twice,
+     * you will have two instances of your singleton unless you implement
+     * readResolve.  Here it is implemented for all objects which have
+     * no implementation and which are marked serializable (which is true
+     * for all case objects.)
      */
     def needsReadResolve = (
          clazz.isModuleClass
@@ -330,8 +329,8 @@ trait SyntheticMethods extends ast.TreeDSL {
         else Nil
       )
 
-      /** Always generate overrides for equals and hashCode in value classes,
-       *  so they can appear in universal traits without breaking value semantics.
+      /* Always generate overrides for equals and hashCode in value classes,
+       * so they can appear in universal traits without breaking value semantics.
        */
       def impls = {
         def shouldGenerate(m: Symbol) = {
@@ -363,11 +362,11 @@ trait SyntheticMethods extends ast.TreeDSL {
       catch { case _: TypeError if reporter.hasErrors => Nil }
     }
 
-    /** If this case class has any less than public accessors,
-     *  adds new accessors at the correct locations to preserve ordering.
-     *  Note that this must be done before the other method synthesis
-     *  because synthesized methods need refer to the new symbols.
-     *  Care must also be taken to preserve the case accessor order.
+    /* If this case class has any less than public accessors,
+     * adds new accessors at the correct locations to preserve ordering.
+     * Note that this must be done before the other method synthesis
+     * because synthesized methods need refer to the new symbols.
+     * Care must also be taken to preserve the case accessor order.
      */
     def caseTemplateBody(): List[Tree] = {
       val lb = ListBuffer[Tree]()
diff --git a/src/compiler/scala/tools/nsc/typechecker/TreeCheckers.scala b/src/compiler/scala/tools/nsc/typechecker/TreeCheckers.scala
index 5c863469e4..dc11c5fe96 100644
--- a/src/compiler/scala/tools/nsc/typechecker/TreeCheckers.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/TreeCheckers.scala
@@ -221,7 +221,7 @@ abstract class TreeCheckers extends Analyzer {
                 case _: ConstantType  => ()
                 case _                =>
                   checkSym(tree)
-                  /** XXX: lots of syms show up here with accessed == NoSymbol. */
+                  /* XXX: lots of syms show up here with accessed == NoSymbol. */
                   if (accessed != NoSymbol) {
                     val agetter = accessed.getter(sym.owner)
                     val asetter = accessed.setter(sym.owner)
@@ -248,7 +248,7 @@ abstract class TreeCheckers extends Analyzer {
             else if (currentOwner.ownerChain takeWhile (_ != sym) exists (_ == NoSymbol))
               return fail("tree symbol "+sym+" does not point to enclosing class; tree = ")
 
-          /** XXX: temporary while Import nodes are arriving untyped. */
+          /* XXX: temporary while Import nodes are arriving untyped. */
           case Import(_, _) =>
             return
           case _ =>
@@ -283,7 +283,6 @@ abstract class TreeCheckers extends Analyzer {
 
       private def checkSymbolRefsRespectScope(tree: Tree) {
         def symbolOf(t: Tree): Symbol = Option(tree.symbol).getOrElse(NoSymbol)
-        def definedSymbolOf(t: Tree): Symbol = if (t.isDef) symbolOf(t) else NoSymbol
         val info = Option(symbolOf(tree).info).getOrElse(NoType)
         val referencedSymbols: List[Symbol] = {
           val directRef = tree match {
diff --git a/src/compiler/scala/tools/nsc/typechecker/Typers.scala b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
index 92f53f4956..0e57145343 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Typers.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
@@ -86,6 +86,9 @@ trait Typers extends Adaptations with Tags {
   // that are turned private by typedBlock
   private final val SYNTHETIC_PRIVATE = TRANS_FLAG
 
+  private final val InterpolatorCodeRegex  = """\$\{.*?\}""".r
+  private final val InterpolatorIdentRegex = """\$\w+""".r
+
   // To enable decent error messages when the typer crashes.
   // TODO - this only catches trees which go through def typed,
   // but there are all kinds of back ways - typedClassDef, etc. etc.
@@ -905,7 +908,7 @@ trait Typers extends Adaptations with Tags {
         }
       }
 
-      /**
+      /*
        * To deal with the type slack between actual (run-time) types and statically known types, for each abstract type T,
        * reflect its variance as a skolem that is upper-bounded by T (covariant position), or lower-bounded by T (contravariant).
        *
@@ -1124,16 +1127,19 @@ trait Typers extends Adaptations with Tags {
               else {
                 if (mode.inExprModeButNot(FUNmode)) {
                   pt.dealias match {
-                    case TypeRef(_, sym, _) =>
+                    // The <: Any requirement inhibits attempts to adapt continuation types
+                    // to non-continuation types.
+                    case TypeRef(_, sym, _) if tree.tpe <:< AnyClass.tpe =>
                       // note: was if (pt.typeSymbol == UnitClass) but this leads to a potentially
                       // infinite expansion if pt is constant type ()
-                      if (sym == UnitClass && tree.tpe <:< AnyClass.tpe) { // (12)
+                      if (sym == UnitClass) { // (12)
                         if (settings.warnValueDiscard.value)
                           context.unit.warning(tree.pos, "discarded non-Unit value")
                         return typedPos(tree.pos, mode, pt) {
-                          Block(List(tree), Literal(Constant()))
+                          Block(List(tree), Literal(Constant(())))
                         }
-                      } else if (isNumericValueClass(sym) && isNumericSubType(tree.tpe, pt)) {
+                      }
+                      else if (isNumericValueClass(sym) && isNumericSubType(tree.tpe, pt)) {
                         if (settings.warnNumericWiden.value)
                           context.unit.warning(tree.pos, "implicit numeric widening")
                         return typedPos(tree.pos, mode, pt) {
@@ -1245,7 +1251,7 @@ trait Typers extends Adaptations with Tags {
       val savedUndetparams = context.undetparams
       silent(_.instantiate(tree, mode, UnitClass.tpe)) orElse { _ =>
           context.undetparams = savedUndetparams
-          val valueDiscard = atPos(tree.pos)(Block(List(instantiate(tree, mode, WildcardType)), Literal(Constant())))
+          val valueDiscard = atPos(tree.pos)(Block(List(instantiate(tree, mode, WildcardType)), Literal(Constant(()))))
           typed(valueDiscard, mode, UnitClass.tpe)
       }
     }
@@ -1504,7 +1510,7 @@ trait Typers extends Adaptations with Tags {
      */
     private def typedParentType(encodedtpt: Tree, templ: Template, inMixinPosition: Boolean): Tree = {
       val app = treeInfo.dissectApplied(encodedtpt)
-      val (treeInfo.Applied(core, targs, argss), decodedtpt) = (app, app.callee)
+      val (treeInfo.Applied(core, targs, argss), decodedtpt) = ((app, app.callee))
       val argssAreTrivial = argss == Nil || argss == ListOfNil
 
       // we cannot avoid cyclic references with `initialize` here, because when type macros arrive,
@@ -2153,7 +2159,7 @@ trait Typers extends Adaptations with Tags {
         unit.error(pos, msg)
         false
       }
-      /** Have to examine all parameters in all lists.
+      /* Have to examine all parameters in all lists.
        */
       def paramssTypes(tp: Type): List[List[Type]] = tp match {
         case mt @ MethodType(_, restpe) => mt.paramTypes :: paramssTypes(restpe)
@@ -2172,10 +2178,10 @@ trait Typers extends Adaptations with Tags {
           val sym = paramType.typeSymbol
           def paramPos = nthParamPos(listIdx, paramIdx)
 
-          /** Not enough to look for abstract types; have to recursively check the bounds
-           *  of each abstract type for more abstract types. Almost certainly there are other
-           *  exploitable type soundness bugs which can be seen by bounding a type parameter
-           *  by an abstract type which itself is bounded by an abstract type.
+          /* Not enough to look for abstract types; have to recursively check the bounds
+           * of each abstract type for more abstract types. Almost certainly there are other
+           * exploitable type soundness bugs which can be seen by bounding a type parameter
+           * by an abstract type which itself is bounded by an abstract type.
            */
           def checkAbstract(tp0: Type, what: String): Boolean = {
             def check(sym: Symbol): Boolean = !sym.isAbstractType || {
@@ -2861,8 +2867,8 @@ trait Typers extends Adaptations with Tags {
           }
       }
 
-      /** 'accessor' and 'accessed' are so similar it becomes very difficult to
-       *  follow the logic, so I renamed one to something distinct.
+      /* 'accessor' and 'accessed' are so similar it becomes very difficult to
+       * follow the logic, so I renamed one to something distinct.
        */
       def accesses(looker: Symbol, accessed: Symbol) = accessed.hasLocalFlag && (
            (accessed.isParamAccessor)
@@ -2985,9 +2991,8 @@ trait Typers extends Adaptations with Tags {
             else if (isByNameParamType(formals.head)) NOmode
             else BYVALmode
           )
-          var tree = typedArg(args.head, mode, typedMode, adapted.head)
           // formals may be empty, so don't call tail
-          tree :: loop(args.tail, formals drop 1, adapted.tail)
+          typedArg(args.head, mode, typedMode, adapted.head) :: loop(args.tail, formals drop 1, adapted.tail)
         }
       }
       loop(args0, formals0, adapted0)
@@ -3119,9 +3124,9 @@ trait Typers extends Adaptations with Tags {
           val argslen = args.length
           val formals = formalTypes(paramTypes, argslen)
 
-          /** Try packing all arguments into a Tuple and apply `fun`
-           *  to that. This is the last thing which is tried (after
-           *  default arguments)
+          /* Try packing all arguments into a Tuple and apply `fun`
+           * to that. This is the last thing which is tried (after
+           * default arguments)
            */
           def tryTupleApply: Option[Tree] = (
             if (eligibleForTupleConversion(paramTypes, argslen) && !phase.erasedTypes) {
@@ -3142,10 +3147,10 @@ trait Typers extends Adaptations with Tags {
             else None
           )
 
-          /** Treats an application which uses named or default arguments.
-           *  Also works if names + a vararg used: when names are used, the vararg
-           *  parameter has to be specified exactly once. Note that combining varargs
-           *  and defaults is ruled out by typedDefDef.
+          /* Treats an application which uses named or default arguments.
+           * Also works if names + a vararg used: when names are used, the vararg
+           * parameter has to be specified exactly once. Note that combining varargs
+           * and defaults is ruled out by typedDefDef.
            */
           def tryNamesDefaults: Tree = {
             val lencmp = compareLengths(args, formals)
@@ -3255,7 +3260,7 @@ trait Typers extends Adaptations with Tags {
                   case _ => tp
                 }
 
-                /**
+                /*
                  * This is translating uses of List() into Nil.  This is less
                  *  than ideal from a consistency standpoint, but it shouldn't be
                  *  altered without due caution.
@@ -3472,8 +3477,8 @@ trait Typers extends Adaptations with Tags {
         ErroneousAnnotation
       }
 
-      /** Calling constfold right here is necessary because some trees (negated
-       *  floats and literals in particular) are not yet folded.
+      /* Calling constfold right here is necessary because some trees (negated
+       * floats and literals in particular) are not yet folded.
        */
       def tryConst(tr: Tree, pt: Type): Option[LiteralAnnotArg] = {
         // The typed tree may be relevantly different than the tree `tr`,
@@ -3495,8 +3500,8 @@ trait Typers extends Adaptations with Tags {
           Some(LiteralAnnotArg(const))
       }
 
-      /** Converts an untyped tree to a ClassfileAnnotArg. If the conversion fails,
-       *  an error message is reported and None is returned.
+      /* Converts an untyped tree to a ClassfileAnnotArg. If the conversion fails,
+       * an error message is reported and None is returned.
        */
       def tree2ConstArg(tree: Tree, pt: Type): Option[ClassfileAnnotArg] = tree match {
         case Apply(Select(New(tpt), nme.CONSTRUCTOR), args) if (pt.typeSymbol == ArrayClass) =>
@@ -3995,13 +4000,13 @@ trait Typers extends Adaptations with Tags {
           def applyOp(args: List[Tree]) = if (hasNamed(args)) nme.applyDynamicNamed else nme.applyDynamic
           def matches(t: Tree)          = isDesugaredApply || treeInfo.dissectApplied(t).core == treeSelection
 
-          /** Note that the trees which arrive here are potentially some distance from
-           *  the trees of direct interest. `cxTree` is some enclosing expression which
-           *  may apparently be arbitrarily larger than `tree`; and `tree` itself is
-           *  too small, having at least in some cases lost its explicit type parameters.
-           *  This logic is designed to use `tree` to pinpoint the immediately surrounding
-           *  Apply/TypeApply/Select node, and only then creates the dynamic call.
-           *  See SI-6731 among others.
+          /* Note that the trees which arrive here are potentially some distance from
+           * the trees of direct interest. `cxTree` is some enclosing expression which
+           * may apparently be arbitrarily larger than `tree`; and `tree` itself is
+           * too small, having at least in some cases lost its explicit type parameters.
+           * This logic is designed to use `tree` to pinpoint the immediately surrounding
+           * Apply/TypeApply/Select node, and only then creates the dynamic call.
+           * See SI-6731 among others.
            */
           def findSelection(t: Tree): Option[(TermName, Tree)] = t match {
             case Apply(fn, args) if hasStar(args) => DynamicVarArgUnsupported(tree, applyOp(args)) ; None
@@ -4060,7 +4065,7 @@ trait Typers extends Adaptations with Tags {
       def typedAnnotated(atd: Annotated): Tree = {
         val ann = atd.annot
         val arg1 = typed(atd.arg, mode, pt)
-        /** mode for typing the annotation itself */
+        /* mode for typing the annotation itself */
         val annotMode = (mode &~ TYPEmode) | EXPRmode
 
         def resultingTypeTree(tpe: Type) = {
@@ -4184,11 +4189,11 @@ trait Typers extends Adaptations with Tags {
 
       def typedArrayValue(tree: ArrayValue) = {
         val elemtpt1 = typedType(tree.elemtpt, mode)
-        val elems1 = tree.elems mapConserve (elem => typed(elem, mode, elemtpt1.tpe))
-        treeCopy.ArrayValue(tree, elemtpt1, elems1)
-          .setType(
-            (if (isFullyDefined(pt) && !phase.erasedTypes) pt
-             else arrayType(elemtpt1.tpe)).notNull)
+        val elems1   = tree.elems mapConserve (elem => typed(elem, mode, elemtpt1.tpe))
+        // see run/t6126 for an example where `pt` does not suffice (tagged types)
+        val tpe1     = if (isFullyDefined(pt) && !phase.erasedTypes) pt else arrayType(elemtpt1.tpe)
+
+        treeCopy.ArrayValue(tree, elemtpt1, elems1) setType tpe1
       }
 
       def typedAssign(lhs: Tree, rhs: Tree): Tree = {
@@ -4336,8 +4341,8 @@ trait Typers extends Adaptations with Tags {
           else tpt0
         }
 
-        /** If current tree <tree> appears in <val x(: T)? = <tree>>
-         *  return `tp with x.type' else return `tp`.
+        /* If current tree <tree> appears in <val x(: T)? = <tree>>
+         * return `tp with x.type' else return `tp`.
          */
         def narrowRhs(tp: Type) = { val sym = context.tree.symbol
           context.tree match {
@@ -4406,8 +4411,8 @@ trait Typers extends Adaptations with Tags {
         }
       }
 
-      /** Try to apply function to arguments; if it does not work, try to convert Java raw to existentials, or try to
-       *  insert an implicit conversion.
+      /* Try to apply function to arguments; if it does not work, try to convert Java raw to existentials, or try to
+       * insert an implicit conversion.
        */
       def tryTypedApply(fun: Tree, args: List[Tree]): Tree = {
         val start = if (Statistics.canEnable) Statistics.startTimer(failedApplyNanos) else null
@@ -4491,35 +4496,31 @@ trait Typers extends Adaptations with Tags {
                   reportError
               }
           }
-          silent(_.typed(fun, mode.forFunMode, funpt),
-                 if (mode.inExprMode) false else context.ambiguousErrors,
-                 if (mode.inExprMode) tree else context.tree) match {
+          val silentResult = silent(
+            op                    = _.typed(fun, mode.forFunMode, funpt),
+            reportAmbiguousErrors = !mode.inExprMode && context.ambiguousErrors,
+            newtree               = if (mode.inExprMode) tree else context.tree
+          )
+          silentResult match {
             case SilentResultValue(fun1) =>
               val fun2 = if (stableApplication) stabilizeFun(fun1, mode, pt) else fun1
               if (Statistics.canEnable) Statistics.incCounter(typedApplyCount)
-              def isImplicitMethod(tpe: Type) = tpe match {
-                case mt: MethodType => mt.isImplicit
-                case _ => false
-              }
-              val useTry = (
-                   !isPastTyper
-                && fun2.isInstanceOf[Select]
-                && !isImplicitMethod(fun2.tpe)
-                && ((fun2.symbol eq null) || !fun2.symbol.isConstructor)
-                && (mode & (EXPRmode | SNDTRYmode)) == EXPRmode
+              val noSecondTry = (
+                   isPastTyper
+                || (fun2.symbol ne null) && fun2.symbol.isConstructor
+                || (fun2.tpe match { case mt: MethodType => mt.isImplicit case _ => false })
+              )
+              val isFirstTry = !noSecondTry && (
+                fun2 match {
+                  case Select(_, _) => mode inExprModeButNot SNDTRYmode
+                  case _            => false
+                }
               )
-              val res =
-                if (useTry) tryTypedApply(fun2, args)
-                else doTypedApply(tree, fun2, args, mode, pt)
-
-              if (fun2.symbol == Array_apply && !res.isErrorTyped) {
-                val checked = gen.mkCheckInit(res)
-                // this check is needed to avoid infinite recursion in Duplicators
-                // (calling typed1 more than once for the same tree)
-                if (checked ne res) typed { atPos(tree.pos)(checked) }
-                else res
-              } else
-                res
+              if (isFirstTry)
+                tryTypedApply(fun2, args)
+              else
+                doTypedApply(tree, fun2, args, mode, pt)
+
             case SilentTypeError(err) =>
               onError({issue(err); setError(tree)})
           }
@@ -4647,8 +4648,8 @@ trait Typers extends Adaptations with Tags {
             if (isStableContext(tree, mode, pt)) tree setType clazz.thisType else tree
         }
 
-      /** Attribute a selection where `tree` is `qual.name`.
-       *  `qual` is already attributed.
+      /* Attribute a selection where `tree` is `qual.name`.
+       * `qual` is already attributed.
        */
       def typedSelect(tree: Tree, qual: Tree, name: Name): Tree = {
         val t = typedSelectInternal(tree, qual, name)
@@ -4735,16 +4736,6 @@ trait Typers extends Adaptations with Tags {
               (stabilize(treeAndPre._1, treeAndPre._2, mode, pt), None)
           }
 
-          def isPotentialNullDeference() = {
-            !isPastTyper &&
-            !sym.isConstructor &&
-            !(qual.tpe <:< NotNullClass.tpe) && !qual.tpe.isNotNull &&
-            !(List(Any_isInstanceOf, Any_asInstanceOf) contains result.symbol)  // null.is/as is not a dereference
-          }
-          // unit is null here sometimes; how are we to know when unit might be null? (See bug #2467.)
-          if (settings.warnSelectNullable.value && isPotentialNullDeference && unit != null)
-            unit.warning(tree.pos, "potential null pointer dereference: "+tree)
-
           result match {
             // could checkAccessible (called by makeAccessible) potentially have skipped checking a type application in qual?
             case SelectFromTypeTree(qual@TypeTree(), name) if qual.tpe.typeArgs.nonEmpty => // TODO: somehow the new qual is not checked in refchecks
@@ -4814,7 +4805,7 @@ trait Typers extends Adaptations with Tags {
         }
       }
 
-      /** A symbol qualifies if:
+      /* A symbol qualifies if:
        *  - it exists
        *  - it is not stale (stale symbols are made to disappear here)
        *  - if we are in a pattern constructor, method definitions do not qualify
@@ -4826,12 +4817,12 @@ trait Typers extends Adaptations with Tags {
         && !(inPatternConstructor && sym.isMethod && !sym.isStable)
       )
 
-      /** Attribute an identifier consisting of a simple name or an outer reference.
+      /* Attribute an identifier consisting of a simple name or an outer reference.
        *
-       *  @param tree      The tree representing the identifier.
-       *  @param name      The name of the identifier.
-       *  Transformations: (1) Prefix class members with this.
-       *                   (2) Change imported symbols to selections
+       * @param tree      The tree representing the identifier.
+       * @param name      The name of the identifier.
+       * Transformations: (1) Prefix class members with this.
+       *                  (2) Change imported symbols to selections
        */
       def typedIdent(tree: Tree, name: Name): Tree = {
         // setting to enable unqualified idents in empty package (used by the repl)
@@ -4973,7 +4964,7 @@ trait Typers extends Adaptations with Tags {
         treeCopy.PackageDef(tree, pid1, stats1) setType NoType
       }
 
-      /**
+      /*
        * The typer with the correct context for a method definition. If the method is a default getter for
        * a constructor default, the resulting typer has a constructor context (fixes SI-5543).
        */
@@ -5151,6 +5142,19 @@ trait Typers extends Adaptations with Tags {
 
       def typedLiteral(tree: Literal) = {
         val value = tree.value
+        // Warn about likely interpolated strings which are missing their interpolators
+        if (settings.lint.value) value match {
+          case Constant(s: String) =>
+            def names = InterpolatorIdentRegex findAllIn s map (n => newTermName(n stripPrefix "$"))
+            val shouldWarn = (
+                 (InterpolatorCodeRegex findFirstIn s).nonEmpty
+              || (names exists (n => context.lookupSymbol(n, _ => true).symbol.exists))
+            )
+            if (shouldWarn)
+              unit.warning(tree.pos, "looks like an interpolated String; did you forget the interpolator?")
+          case _ =>
+        }
+
         tree setType (
           if (value.tag == UnitTag) UnitClass.tpe
           else ConstantType(value))
diff --git a/src/compiler/scala/tools/nsc/util/AbstractFileClassLoader.scala b/src/compiler/scala/tools/nsc/util/AbstractFileClassLoader.scala
index e4f879560c..b204c39e9c 100644
--- a/src/compiler/scala/tools/nsc/util/AbstractFileClassLoader.scala
+++ b/src/compiler/scala/tools/nsc/util/AbstractFileClassLoader.scala
@@ -8,7 +8,6 @@ package util
 import scala.tools.nsc.io.AbstractFile
 import java.security.cert.Certificate
 import java.security.{ ProtectionDomain, CodeSource }
-import util.ScalaClassLoader
 import java.net.{ URL, URLConnection, URLStreamHandler }
 import scala.collection.{ mutable, immutable }
 
@@ -91,10 +90,13 @@ class AbstractFileClassLoader(val root: AbstractFile, parent: ClassLoader)
   lazy val protectionDomain = {
     val cl = Thread.currentThread().getContextClassLoader()
     val resource = cl.getResource("scala/runtime/package.class")
-    if (resource == null) null else {
+    if (resource == null || resource.getProtocol != "jar") null else {
       val s = resource.getPath
-      val path = s.substring(0, s.lastIndexOf('!'))
-      new ProtectionDomain(new CodeSource(new URL(path), null.asInstanceOf[Array[Certificate]]), null, this, null)
+      val n = s.lastIndexOf('!')
+      if (n < 0) null else {
+        val path = s.substring(0, n)
+        new ProtectionDomain(new CodeSource(new URL(path), null.asInstanceOf[Array[Certificate]]), null, this, null)
+      }
     }
   }
 
diff --git a/src/compiler/scala/tools/nsc/util/ClassPath.scala b/src/compiler/scala/tools/nsc/util/ClassPath.scala
index 5f13baa107..aa4128f1a7 100644
--- a/src/compiler/scala/tools/nsc/util/ClassPath.scala
+++ b/src/compiler/scala/tools/nsc/util/ClassPath.scala
@@ -29,7 +29,7 @@ object ClassPath {
   private def expandS(pattern: String): List[String] = {
     val wildSuffix = File.separator + "*"
 
-    /** Get all subdirectories, jars, zips out of a directory. */
+    /* Get all subdirectories, jars, zips out of a directory. */
     def lsDir(dir: Directory, filt: String => Boolean = _ => true) =
       dir.list filter (x => filt(x.name) && (x.isDirectory || isJarOrZip(x))) map (_.path) toList
 
diff --git a/src/compiler/scala/tools/nsc/util/ShowPickled.scala b/src/compiler/scala/tools/nsc/util/ShowPickled.scala
index f91e94471a..76b1394b85 100644
--- a/src/compiler/scala/tools/nsc/util/ShowPickled.scala
+++ b/src/compiler/scala/tools/nsc/util/ShowPickled.scala
@@ -163,7 +163,7 @@ object ShowPickled extends Names {
         out.print(" %s[%s]".format(toHexString(pflags), flagString))
       }
 
-      /** Might be info or privateWithin */
+      /* Might be info or privateWithin */
       val x = buf.readNat()
       if (buf.readIndex == end) {
         printFlags(None)
@@ -175,9 +175,9 @@ object ShowPickled extends Names {
       }
     }
 
-    /** Note: the entries which require some semantic analysis to be correctly
-     *  interpreted are for the most part going to tell you the wrong thing.
-     *  It's not so easy to duplicate the logic applied in the UnPickler.
+    /* Note: the entries which require some semantic analysis to be correctly
+     * interpreted are for the most part going to tell you the wrong thing.
+     * It's not so easy to duplicate the logic applied in the UnPickler.
      */
     def printEntry(i: Int) {
       buf.readIndex = index(i)
diff --git a/src/compiler/scala/tools/reflect/FastTrack.scala b/src/compiler/scala/tools/reflect/FastTrack.scala
index ac50324fa9..aa4ddc8ba8 100644
--- a/src/compiler/scala/tools/reflect/FastTrack.scala
+++ b/src/compiler/scala/tools/reflect/FastTrack.scala
@@ -27,7 +27,7 @@ trait FastTrack {
   final class FastTrackEntry(pf: PartialFunction[Applied, MacroContext => Tree]) extends (MacroArgs => Any) {
     def validate(tree: Tree) = pf isDefinedAt Applied(tree)
     def apply(margs: MacroArgs) = {
-      val MacroArgs(c, args) = margs
+      val MacroArgs(c, _) = margs
       // Macros validated that the pf is defined here - and there's not much we could do if it weren't.
       c.Expr[Nothing](pf(Applied(c.expandee))(c))(c.WeakTypeTag.Nothing)
     }
diff --git a/src/compiler/scala/tools/reflect/ToolBoxFactory.scala b/src/compiler/scala/tools/reflect/ToolBoxFactory.scala
index e6bbe1dbed..3e227ce8aa 100644
--- a/src/compiler/scala/tools/reflect/ToolBoxFactory.scala
+++ b/src/compiler/scala/tools/reflect/ToolBoxFactory.scala
@@ -142,8 +142,8 @@ abstract class ToolBoxFactory[U <: JavaUniverse](val u: U) { factorySelf =>
 
         val expr1 = wrapper(transform(currentTyper, expr))
         var (dummies1, unwrapped) = expr1 match {
-          case Block(dummies, unwrapped) => (dummies, unwrapped)
-          case unwrapped => (Nil, unwrapped)
+          case Block(dummies, unwrapped) => ((dummies, unwrapped))
+          case unwrapped                 => ((Nil, unwrapped))
         }
         val invertedIndex = freeTerms map (_.swap)
         // todo. also fixup singleton types
@@ -369,7 +369,7 @@ abstract class ToolBoxFactory[U <: JavaUniverse](val u: U) { factorySelf =>
     }
 
     private def inferImplicit(tree: u.Tree, pt: u.Type, isView: Boolean, silent: Boolean, withMacrosDisabled: Boolean, pos: u.Position): u.Tree = compiler.withCleanupCaches {
-      if (compiler.settings.verbose.value) println("importing "+pt, ", tree = "+tree+", pos = "+pos)
+      if (compiler.settings.verbose.value) println(s"importing pt=$pt, tree=$tree, pos=$pos")
       val ctree: compiler.Tree = importer.importTree(tree)
       val cpt: compiler.Type = importer.importType(pt)
       val cpos: compiler.Position = importer.importPosition(pos)
diff --git a/src/continuations/plugin/scala/tools/selectivecps/SelectiveANFTransform.scala b/src/continuations/plugin/scala/tools/selectivecps/SelectiveANFTransform.scala
index 323e894b51..ae95a1bdac 100644
--- a/src/continuations/plugin/scala/tools/selectivecps/SelectiveANFTransform.scala
+++ b/src/continuations/plugin/scala/tools/selectivecps/SelectiveANFTransform.scala
@@ -400,9 +400,9 @@ abstract class SelectiveANFTransform extends PluginComponent with Transform with
 
           try {
             val Some((a, b)) = cpsR
-            /** Since shiftUnit is bounded [A,B,C>:B] this may not typecheck
-             *  if C is overly specific.  So if !(B <:< C), call shiftUnit0
-             *  instead, which takes only two type arguments.
+            /* Since shiftUnit is bounded [A,B,C>:B] this may not typecheck
+             * if C is overly specific.  So if !(B <:< C), call shiftUnit0
+             * instead, which takes only two type arguments.
              */
             val conforms = a <:< b
             val call = localTyper.typedPos(tree.pos)(
diff --git a/src/interactive/scala/tools/nsc/interactive/CompilerControl.scala b/src/interactive/scala/tools/nsc/interactive/CompilerControl.scala
index f84fa161c0..c5136c752b 100644
--- a/src/interactive/scala/tools/nsc/interactive/CompilerControl.scala
+++ b/src/interactive/scala/tools/nsc/interactive/CompilerControl.scala
@@ -118,7 +118,7 @@ trait CompilerControl { self: Global =>
       case ri: ReloadItem if ri.sources == sources => Some(ri)
       case _ => None
     }
-    superseeded.foreach(_.response.set())
+    superseeded.foreach(_.response.set(()))
     postWorkItem(new ReloadItem(sources, response))
   }
 
diff --git a/src/library/scala/AnyVal.scala b/src/library/scala/AnyVal.scala
index 0d6ba2454c..9def6cb054 100644
--- a/src/library/scala/AnyVal.scala
+++ b/src/library/scala/AnyVal.scala
@@ -52,6 +52,6 @@ package scala
  * as well as in [[http://docs.scala-lang.org/sips/pending/value-classes.html SIP-15: Value Classes]],
  * the Scala Improvement Proposal.
  */
-abstract class AnyVal extends Any with NotNull {
+abstract class AnyVal extends Any {
   def getClass(): Class[_ <: AnyVal] = null
 }
diff --git a/src/library/scala/NotNull.scala b/src/library/scala/NotNull.scala
index f87416b49d..3cbe9ed4ac 100644
--- a/src/library/scala/NotNull.scala
+++ b/src/library/scala/NotNull.scala
@@ -12,4 +12,6 @@ package scala
  * A marker trait for things that are not allowed to be null
  * @since 2.5
  */
+
+@deprecated("This trait will be removed", "2.11.0")
 trait NotNull extends Any {}
diff --git a/src/library/scala/collection/BitSetLike.scala b/src/library/scala/collection/BitSetLike.scala
index 72a6713ffd..034ed2b24a 100644
--- a/src/library/scala/collection/BitSetLike.scala
+++ b/src/library/scala/collection/BitSetLike.scala
@@ -69,6 +69,8 @@ trait BitSetLike[+This <: BitSetLike[This] with SortedSet[Int]] extends SortedSe
     s
   }
 
+  override def isEmpty: Boolean = 0 until nwords forall (i => word(i) == 0)
+
   implicit def ordering: Ordering[Int] = Ordering.Int
 
   def rangeImpl(from: Option[Int], until: Option[Int]): This = {
diff --git a/src/library/scala/collection/Iterator.scala b/src/library/scala/collection/Iterator.scala
index 43db7c55e0..c85a4fb6e7 100644
--- a/src/library/scala/collection/Iterator.scala
+++ b/src/library/scala/collection/Iterator.scala
@@ -555,7 +555,7 @@ trait Iterator[+A] extends TraversableOnce[A] {
   def span(p: A => Boolean): (Iterator[A], Iterator[A]) = {
     val self = buffered
 
-    /**
+    /*
      * Giving a name to following iterator (as opposed to trailing) because
      * anonymous class is represented as a structural type that trailing
      * iterator is referring (the finish() method) and thus triggering
diff --git a/src/library/scala/collection/SeqLike.scala b/src/library/scala/collection/SeqLike.scala
index a83a6fe6a1..c02ea98914 100644
--- a/src/library/scala/collection/SeqLike.scala
+++ b/src/library/scala/collection/SeqLike.scala
@@ -210,13 +210,13 @@ trait SeqLike[+A, +Repr] extends Any with IterableLike[A, Repr] with GenSeqLike[
       if (!hasNext)
         Iterator.empty.next()
 
-      /** Calculate this result. */
+      /* Calculate this result. */
       val buf = self.newBuilder
       for(k <- 0 until nums.length; j <- 0 until nums(k))
         buf += elms(offs(k)+j)
       val res = buf.result()
 
-      /** Prepare for the next call to next. */
+      /* Prepare for the next call to next. */
       var idx = nums.length - 1
       while (idx >= 0 && nums(idx) == cnts(idx))
         idx -= 1
diff --git a/src/library/scala/collection/immutable/NumericRange.scala b/src/library/scala/collection/immutable/NumericRange.scala
index 195aeed281..5842ff30e6 100644
--- a/src/library/scala/collection/immutable/NumericRange.scala
+++ b/src/library/scala/collection/immutable/NumericRange.scala
@@ -220,10 +220,10 @@ object NumericRange {
         if (!isInclusive && zero == remainder) 0 else 1
       )
 
-      /** The edge cases keep coming.  Since e.g.
-       *    Long.MaxValue + 1 == Long.MinValue
-       *  we do some more improbable seeming checks lest
-       *  overflow turn up as an empty range.
+      /* The edge cases keep coming.  Since e.g.
+       * Long.MaxValue + 1 == Long.MinValue
+       * we do some more improbable seeming checks lest
+       * overflow turn up as an empty range.
        */
       // The second condition contradicts an empty result.
       val isOverflow = longCount == 0 && num.lt(num.plus(start, step), end) == upward
diff --git a/src/library/scala/collection/immutable/RedBlackTree.scala b/src/library/scala/collection/immutable/RedBlackTree.scala
index 37b8ecfbc4..48bccde0e8 100644
--- a/src/library/scala/collection/immutable/RedBlackTree.scala
+++ b/src/library/scala/collection/immutable/RedBlackTree.scala
@@ -325,54 +325,56 @@ object RedBlackTree {
   // whether the zipper was traversed left-most or right-most.
 
   // If the trees were balanced, returns an empty zipper
-  private[this] def compareDepth[A, B](left: Tree[A, B], right: Tree[A, B]): (List[Tree[A, B]], Boolean, Boolean, Int) = {
+  private[this] def compareDepth[A, B](left: Tree[A, B], right: Tree[A, B]): (NList[Tree[A, B]], Boolean, Boolean, Int) = {
+    import NList.cons
     // Once a side is found to be deeper, unzip it to the bottom
-    def unzip(zipper: List[Tree[A, B]], leftMost: Boolean): List[Tree[A, B]] = {
+    def unzip(zipper: NList[Tree[A, B]], leftMost: Boolean): NList[Tree[A, B]] = {
       val next = if (leftMost) zipper.head.left else zipper.head.right
-      next match {
-        case null => zipper
-        case node => unzip(node :: zipper, leftMost)
-      }
+      if (next eq null) zipper
+      else unzip(cons(next, zipper), leftMost)
     }
 
     // Unzip left tree on the rightmost side and right tree on the leftmost side until one is
     // found to be deeper, or the bottom is reached
     def unzipBoth(left: Tree[A, B],
                   right: Tree[A, B],
-                  leftZipper: List[Tree[A, B]],
-                  rightZipper: List[Tree[A, B]],
-                  smallerDepth: Int): (List[Tree[A, B]], Boolean, Boolean, Int) = {
+                  leftZipper: NList[Tree[A, B]],
+                  rightZipper: NList[Tree[A, B]],
+                  smallerDepth: Int): (NList[Tree[A, B]], Boolean, Boolean, Int) = {
       if (isBlackTree(left) && isBlackTree(right)) {
-        unzipBoth(left.right, right.left, left :: leftZipper, right :: rightZipper, smallerDepth + 1)
+        unzipBoth(left.right, right.left, cons(left, leftZipper), cons(right, rightZipper), smallerDepth + 1)
       } else if (isRedTree(left) && isRedTree(right)) {
-        unzipBoth(left.right, right.left, left :: leftZipper, right :: rightZipper, smallerDepth)
+        unzipBoth(left.right, right.left, cons(left, leftZipper), cons(right, rightZipper), smallerDepth)
       } else if (isRedTree(right)) {
-        unzipBoth(left, right.left, leftZipper, right :: rightZipper, smallerDepth)
+        unzipBoth(left, right.left, leftZipper, cons(right, rightZipper), smallerDepth)
       } else if (isRedTree(left)) {
-        unzipBoth(left.right, right, left :: leftZipper, rightZipper, smallerDepth)
+        unzipBoth(left.right, right, cons(left, leftZipper), rightZipper, smallerDepth)
       } else if ((left eq null) && (right eq null)) {
-        (Nil, true, false, smallerDepth)
+        (null, true, false, smallerDepth)
       } else if ((left eq null) && isBlackTree(right)) {
         val leftMost = true
-        (unzip(right :: rightZipper, leftMost), false, leftMost, smallerDepth)
+        (unzip(cons(right, rightZipper), leftMost), false, leftMost, smallerDepth)
       } else if (isBlackTree(left) && (right eq null)) {
         val leftMost = false
-        (unzip(left :: leftZipper, leftMost), false, leftMost, smallerDepth)
+        (unzip(cons(left, leftZipper), leftMost), false, leftMost, smallerDepth)
       } else {
         sys.error("unmatched trees in unzip: " + left + ", " + right)
       }
     }
-    unzipBoth(left, right, Nil, Nil, 0)
+    unzipBoth(left, right, null, null, 0)
   }
 
   private[this] def rebalance[A, B](tree: Tree[A, B], newLeft: Tree[A, B], newRight: Tree[A, B]) = {
     // This is like drop(n-1), but only counting black nodes
-    def  findDepth(zipper: List[Tree[A, B]], depth: Int): List[Tree[A, B]] = zipper match {
-      case head :: tail if isBlackTree(head) =>
-        if (depth == 1) zipper else findDepth(tail, depth - 1)
-      case _ :: tail => findDepth(tail, depth)
-      case Nil => sys.error("Defect: unexpected empty zipper while computing range")
-    }
+    @tailrec
+    def  findDepth(zipper: NList[Tree[A, B]], depth: Int): NList[Tree[A, B]] = 
+      if (zipper eq null) {
+        sys.error("Defect: unexpected empty zipper while computing range")
+      } else if (isBlackTree(zipper.head)) {
+        if (depth == 1) zipper else findDepth(zipper.tail, depth - 1)
+      } else {
+        findDepth(zipper.tail, depth)
+      }
 
     // Blackening the smaller tree avoids balancing problems on union;
     // this can't be done later, though, or it would change the result of compareDepth
@@ -389,7 +391,7 @@ object RedBlackTree {
       } else {
         RedTree(tree.key, tree.value, zipFrom.head, blkNewRight)
       }
-      val zippedTree = zipFrom.tail.foldLeft(union: Tree[A, B]) { (tree, node) =>
+      val zippedTree = NList.foldLeft(zipFrom.tail, union: Tree[A, B]) { (tree, node) =>
         if (leftMost)
           balanceLeft(isBlackTree(node), node.key, node.value, tree, node.right)
         else
@@ -398,6 +400,25 @@ object RedBlackTree {
       zippedTree
     }
   }
+  
+  // Null optimized list implementation for tree rebalancing. null presents Nil.
+  private[this] final class NList[A](val head: A, val tail: NList[A])
+
+  private[this] final object NList {
+    
+    def cons[B](x: B, xs: NList[B]): NList[B] = new NList(x, xs)
+    
+    def foldLeft[A, B](xs: NList[A], z: B)(f: (B, A) => B): B = {
+      var acc = z
+      var these = xs
+      while (these ne null) {
+        acc = f(acc, these.head)
+        these = these.tail
+      }
+      acc
+    }
+    
+  }
 
   /*
    * Forcing direct fields access using the @inline annotation helps speed up
diff --git a/src/library/scala/collection/mutable/BitSet.scala b/src/library/scala/collection/mutable/BitSet.scala
index 2a535a799c..397f8099eb 100644
--- a/src/library/scala/collection/mutable/BitSet.scala
+++ b/src/library/scala/collection/mutable/BitSet.scala
@@ -58,6 +58,11 @@ class BitSet(protected var elems: Array[Long]) extends AbstractSet[Int]
     if (idx < nwords) elems(idx) else 0L
 
   private def updateWord(idx: Int, w: Long) {
+    ensureCapacity(idx)
+    elems(idx) = w
+  }
+
+  private def ensureCapacity(idx: Int) {
     if (idx >= nwords) {
       var newlen = nwords
       while (idx >= newlen) newlen = newlen * 2
@@ -65,7 +70,6 @@ class BitSet(protected var elems: Array[Long]) extends AbstractSet[Int]
       Array.copy(elems, 0, elems1, 0, nwords)
       elems = elems1
     }
-    elems(idx) = w
   }
 
   protected def fromBitMaskNoCopy(words: Array[Long]): BitSet = new BitSet(words)
@@ -92,6 +96,51 @@ class BitSet(protected var elems: Array[Long]) extends AbstractSet[Int]
   def += (elem: Int): this.type = { add(elem); this }
   def -= (elem: Int): this.type = { remove(elem); this }
 
+  /** Updates this bitset to the union with another bitset by performing a bitwise "or".
+   *
+   *  @param   other  the bitset to form the union with.
+   *  @return  the bitset itself.
+   */
+  def |= (other: BitSet): this.type = {
+    ensureCapacity(other.nwords)
+    for (i <- 0 until other.nwords)
+      elems(i) = elems(i) | other.word(i)
+    this
+  }
+  /** Updates this bitset to the intersection with another bitset by performing a bitwise "and".
+   *
+   *  @param   other  the bitset to form the intersection with.
+   *  @return  the bitset itself.
+   */
+  def &= (other: BitSet): this.type = {
+    ensureCapacity(other.nwords)
+    for (i <- 0 until other.nwords)
+      elems(i) = elems(i) & other.word(i)
+    this
+  }
+  /** Updates this bitset to the symmetric difference with another bitset by performing a bitwise "xor".
+   *
+   *  @param   other  the bitset to form the symmetric difference with.
+   *  @return  the bitset itself.
+   */
+  def ^= (other: BitSet): this.type = {
+    ensureCapacity(other.nwords)
+    for (i <- 0 until other.nwords)
+      elems(i) = elems(i) ^ other.word(i)
+    this
+  }
+  /** Updates this bitset to the difference with another bitset by performing a bitwise "and-not".
+   *
+   *  @param   other  the bitset to form the difference with.
+   *  @return  the bitset itself.
+   */
+  def &~= (other: BitSet): this.type = {
+    ensureCapacity(other.nwords)
+    for (i <- 0 until other.nwords)
+      elems(i) = elems(i) & ~other.word(i)
+    this
+  }
+
   override def clear() {
     elems = new Array[Long](elems.length)
   }
diff --git a/src/library/scala/collection/parallel/TaskSupport.scala b/src/library/scala/collection/parallel/TaskSupport.scala
index 9bed5be51b..1ab41bd296 100644
--- a/src/library/scala/collection/parallel/TaskSupport.scala
+++ b/src/library/scala/collection/parallel/TaskSupport.scala
@@ -17,28 +17,25 @@ import scala.concurrent.ExecutionContext
 
 
 
-/** A trait implementing the scheduling of
- *  a parallel collection operation.
+/** A trait implementing the scheduling of a parallel collection operation.
  *
  *  Parallel collections are modular in the way operations are scheduled. Each
  *  parallel collection is parametrized with a task support object which is
  *  responsible for scheduling and load-balancing tasks to processors.
- *  
+ *
  *  A task support object can be changed in a parallel collection after it has
  *  been created, but only during a quiescent period, i.e. while there are no
  *  concurrent invocations to parallel collection methods.
  *
  *  There are currently a few task support implementations available for
  *  parallel collections. The [[scala.collection.parallel.ForkJoinTaskSupport]]
- *  uses a fork-join pool
- *  internally and is used by default on JVM 1.6 or greater. The less efficient
- *  [[scala.collection.parallel.ThreadPoolTaskSupport]] is a fallback for JVM
- *  1.5 and JVMs that do not support the fork join pools. The
- *  [[scala.collection.parallel.ExecutionContextTaskSupport]] uses the
+ *  uses a fork-join pool internally.
+ *
+ *  The [[scala.collection.parallel.ExecutionContextTaskSupport]] uses the
  *  default execution context implementation found in scala.concurrent, and it
- *  reuses the thread pool used in scala.concurrent (this is either a fork join
- *  pool or a thread pool executor, depending on the JVM version). The
- *  execution context task support is set to each parallel collection by
+ *  reuses the thread pool used in scala.concurrent.
+ *
+ *  The execution context task support is set to each parallel collection by
  *  default, so parallel collections reuse the same fork-join pool as the
  *  future API.
  *
@@ -68,17 +65,18 @@ extends TaskSupport with AdaptiveWorkStealingForkJoinTasks
  *
  *  @see [[scala.collection.parallel.TaskSupport]] for more information.
  */
+@deprecated("Use `ForkJoinTaskSupport` instead.", "2.11.0")
 class ThreadPoolTaskSupport(val environment: ThreadPoolExecutor = ThreadPoolTasks.defaultThreadPool)
 extends TaskSupport with AdaptiveWorkStealingThreadPoolTasks
 
 
 /** A task support that uses an execution context to schedule tasks.
- *  
+ *
  *  It can be used with the default execution context implementation in the
  *  `scala.concurrent` package. It internally forwards the call to either a
  *  forkjoin based task support or a thread pool executor one, depending on
  *  what the execution context uses.
- *  
+ *
  *  By default, parallel collections are parametrized with this task support
  *  object, so parallel collections share the same execution context backend
  *  as the rest of the `scala.concurrent` package.
diff --git a/src/library/scala/collection/parallel/Tasks.scala b/src/library/scala/collection/parallel/Tasks.scala
index 441c4269c3..487b3d46d3 100644
--- a/src/library/scala/collection/parallel/Tasks.scala
+++ b/src/library/scala/collection/parallel/Tasks.scala
@@ -214,6 +214,7 @@ trait AdaptiveWorkStealingTasks extends Tasks {
 
 
 /** An implementation of tasks objects based on the Java thread pooling API. */
+@deprecated("Use `ForkJoinTasks` instead.", "2.11.0")
 trait ThreadPoolTasks extends Tasks {
   import java.util.concurrent._
 
@@ -322,6 +323,7 @@ trait ThreadPoolTasks extends Tasks {
 
 }
 
+@deprecated("Use `ForkJoinTasks` instead.", "2.11.0")
 object ThreadPoolTasks {
   import java.util.concurrent._
 
@@ -455,7 +457,7 @@ trait AdaptiveWorkStealingForkJoinTasks extends ForkJoinTasks with AdaptiveWorkS
 
 }
 
-
+@deprecated("Use `AdaptiveWorkStealingForkJoinTasks` instead.", "2.11.0")
 trait AdaptiveWorkStealingThreadPoolTasks extends ThreadPoolTasks with AdaptiveWorkStealingTasks {
 
   class WrappedTask[R, Tp](val body: Task[R, Tp])
diff --git a/src/library/scala/concurrent/SyncVar.scala b/src/library/scala/concurrent/SyncVar.scala
index 9ab7bcc572..6d25ffe19e 100644
--- a/src/library/scala/concurrent/SyncVar.scala
+++ b/src/library/scala/concurrent/SyncVar.scala
@@ -41,9 +41,9 @@ class SyncVar[A] {
    *  @return            `None` if variable is undefined after `timeout`, `Some(value)` otherwise
    */
   def get(timeout: Long): Option[A] = synchronized {
-    /** Defending against the system clock going backward
-     *  by counting time elapsed directly.  Loop required
-     *  to deal with spurious wakeups.
+    /* Defending against the system clock going backward
+     * by counting time elapsed directly.  Loop required
+     * to deal with spurious wakeups.
      */
     var rest = timeout
     while (!isDefined && rest > 0) {
diff --git a/src/library/scala/xml/parsing/MarkupParser.scala b/src/library/scala/xml/parsing/MarkupParser.scala
index d289414c26..9c7bb60475 100755
--- a/src/library/scala/xml/parsing/MarkupParser.scala
+++ b/src/library/scala/xml/parsing/MarkupParser.scala
@@ -108,7 +108,7 @@ trait MarkupParser extends MarkupParserCommon with TokenTests
         val ilen = inpStack.length
         //Console.println("  ilen = "+ilen+ " extIndex = "+extIndex);
         if ((ilen != extIndex) && (ilen > 0)) {
-          /** for external source, inpStack == Nil ! need notify of eof! */
+          /* for external source, inpStack == Nil ! need notify of eof! */
           pop()
         } else {
           reachedEof = true
@@ -880,7 +880,7 @@ trait MarkupParser extends MarkupParserCommon with TokenTests
       externalID()
     }
     else if (ch == 'P') {
-      /** PublicID (without system, only used in NOTATION) */
+      /* PublicID (without system, only used in NOTATION) */
       nextch()
       xToken("UBLIC")
       xSpace()
diff --git a/src/partest/scala/tools/partest/nest/ConsoleRunner.scala b/src/partest/scala/tools/partest/nest/ConsoleRunner.scala
index 6a24926b14..fd4d52f603 100644
--- a/src/partest/scala/tools/partest/nest/ConsoleRunner.scala
+++ b/src/partest/scala/tools/partest/nest/ConsoleRunner.scala
@@ -76,7 +76,7 @@ class ConsoleRunner extends DirectRunner {
     val parsed = CommandLineParser(argstr) withUnaryArgs unaryArgs withBinaryArgs binaryArgs
     val args   = onlyValidTestPaths(parsed.residualArgs)
 
-    /** Early return on no args, version, or invalid args */
+    /* Early return on no args, version, or invalid args */
     if (argstr == "") return NestUI.usage()
     if (parsed isSet "--version") return printVersion
     if (parsed isSet "--help") return NestUI.usage()
diff --git a/src/reflect/scala/reflect/api/Trees.scala b/src/reflect/scala/reflect/api/Trees.scala
index 0170bf2032..18985fe83d 100644
--- a/src/reflect/scala/reflect/api/Trees.scala
+++ b/src/reflect/scala/reflect/api/Trees.scala
@@ -1038,7 +1038,7 @@ trait Trees { self: Universe =>
    *    `case` pat `if` guard => body
    *
    *  If the guard is not present, the `guard` is set to `EmptyTree`.
-   *  If the body is not specified, the `body` is set to `Literal(Constant())`
+   *  If the body is not specified, the `body` is set to `Literal(Constant(()))`
    *  @group Extractors
    */
   abstract class CaseDefExtractor {
@@ -1059,7 +1059,7 @@ trait Trees { self: Universe =>
     def guard: Tree
 
     /** The body of the pattern matching clause.
-     *  Is equal to `Literal(Constant())` if the body is not specified.
+     *  Is equal to `Literal(Constant(()))` if the body is not specified.
      */
     def body: Tree
   }
diff --git a/src/reflect/scala/reflect/internal/ClassfileConstants.scala b/src/reflect/scala/reflect/internal/ClassfileConstants.scala
index 2ab3caa19d..78f7438429 100644
--- a/src/reflect/scala/reflect/internal/ClassfileConstants.scala
+++ b/src/reflect/scala/reflect/internal/ClassfileConstants.scala
@@ -350,7 +350,7 @@ object ClassfileConstants {
     }
     private def translateFlags(jflags: Int, baseFlags: Long): Long = {
       var res: Long = JAVA | baseFlags
-      /** fast, elegant, maintainable, pick any two... */
+      /* fast, elegant, maintainable, pick any two... */
       res |= translateFlag(jflags & JAVA_ACC_PRIVATE)
       res |= translateFlag(jflags & JAVA_ACC_PROTECTED)
       res |= translateFlag(jflags & JAVA_ACC_FINAL)
diff --git a/src/reflect/scala/reflect/internal/Definitions.scala b/src/reflect/scala/reflect/internal/Definitions.scala
index fe5a5c81e2..55954196f6 100644
--- a/src/reflect/scala/reflect/internal/Definitions.scala
+++ b/src/reflect/scala/reflect/internal/Definitions.scala
@@ -281,7 +281,7 @@ trait Definitions extends api.StandardDefinitions {
     def Predef_AnyRef = AnyRefModule
 
     lazy val AnyValClass: ClassSymbol = (ScalaPackageClass.info member tpnme.AnyVal orElse {
-      val anyval    = enterNewClass(ScalaPackageClass, tpnme.AnyVal, List(AnyClass.tpe, NotNullClass.tpe), ABSTRACT)
+      val anyval    = enterNewClass(ScalaPackageClass, tpnme.AnyVal, AnyClass.tpe :: Nil, ABSTRACT)
       val av_constr = anyval.newClassConstructor(NoPosition)
       anyval.info.decls enter av_constr
       anyval
@@ -383,7 +383,6 @@ trait Definitions extends api.StandardDefinitions {
     lazy val StringAddClass             = requiredClass[scala.runtime.StringAdd]
     lazy val ArrowAssocClass            = getRequiredClass("scala.Predef.ArrowAssoc") // SI-5731
     lazy val StringAdd_+                = getMemberMethod(StringAddClass, nme.PLUS)
-    lazy val NotNullClass               = getRequiredClass("scala.NotNull")
     lazy val ScalaNumberClass           = requiredClass[scala.math.ScalaNumber]
     lazy val TraitSetterAnnotationClass = requiredClass[scala.runtime.TraitSetter]
     lazy val DelayedInitClass           = requiredClass[scala.DelayedInit]
@@ -1131,7 +1130,7 @@ trait Definitions extends api.StandardDefinitions {
     /** Is type's symbol a numeric value class? */
     def isNumericValueType(tp: Type): Boolean = tp match {
       case TypeRef(_, sym, _) => isNumericValueClass(sym)
-      case _ => false
+      case _                  => false
     }
 
     // todo: reconcile with javaSignature!!!
diff --git a/src/reflect/scala/reflect/internal/Flags.scala b/src/reflect/scala/reflect/internal/Flags.scala
index 1987f34474..fe46a0471e 100644
--- a/src/reflect/scala/reflect/internal/Flags.scala
+++ b/src/reflect/scala/reflect/internal/Flags.scala
@@ -307,7 +307,11 @@ class Flags extends ModifierFlags {
   assert((OverloadedFlagsMask & FlagsNotPickled) == 0, flagsToString(OverloadedFlagsMask & FlagsNotPickled))
 
   /** These flags are pickled */
-  final val PickledFlags  = InitialFlags & ~FlagsNotPickled
+  final val PickledFlags  = (
+      (InitialFlags & ~FlagsNotPickled)
+    | notPRIVATE // for value class constructors (SI-6601), and private members referenced
+                 // in @inline-marked methods publicized in SuperAccessors (see SI-6608, e6b4204604)
+  )
 
   /** If we have a top-level class or module
    *  and someone asks us for a flag not in TopLevelPickledFlags,
diff --git a/src/reflect/scala/reflect/internal/Importers.scala b/src/reflect/scala/reflect/internal/Importers.scala
index 53410b29c5..f736202e13 100644
--- a/src/reflect/scala/reflect/internal/Importers.scala
+++ b/src/reflect/scala/reflect/internal/Importers.scala
@@ -248,8 +248,6 @@ trait Importers extends api.Importers { self: SymbolTable =>
           AntiPolyType(importType(pre), targs map importType)
         case x: from.TypeVar =>
           TypeVar(importType(x.origin), importTypeConstraint(x.constr), x.typeArgs map importType, x.params map importSymbol)
-        case from.NotNullType(tpe) =>
-          NotNullType(importType(tpe))
         case from.AnnotatedType(annots, tpe, selfsym) =>
           AnnotatedType(annots map importAnnotationInfo, importType(tpe), importSymbol(selfsym))
         case from.ErrorType =>
diff --git a/src/reflect/scala/reflect/internal/Mirrors.scala b/src/reflect/scala/reflect/internal/Mirrors.scala
index d9f1d90b62..63178d0b39 100644
--- a/src/reflect/scala/reflect/internal/Mirrors.scala
+++ b/src/reflect/scala/reflect/internal/Mirrors.scala
@@ -197,8 +197,8 @@ trait Mirrors extends api.Mirrors {
     /************************ helpers ************************/
 
     def erasureName[T: ClassTag] : String = {
-      /** We'd like the String representation to be a valid
-       *  scala type, so we have to decode the jvm's secret language.
+      /* We'd like the String representation to be a valid
+       * scala type, so we have to decode the jvm's secret language.
        */
       def erasureString(clazz: Class[_]): String = {
         if (clazz.isArray) "Array[" + erasureString(clazz.getComponentType) + "]"
diff --git a/src/reflect/scala/reflect/internal/Symbols.scala b/src/reflect/scala/reflect/internal/Symbols.scala
index 6837f37445..c881de7830 100644
--- a/src/reflect/scala/reflect/internal/Symbols.scala
+++ b/src/reflect/scala/reflect/internal/Symbols.scala
@@ -1671,6 +1671,19 @@ trait Symbols extends api.Symbols { self: SymbolTable =>
      *  and is this class symbol also different from Null or Nothing? */
     def isNonBottomSubClass(that: Symbol): Boolean = false
 
+    /** Is this class symbol Null or Nothing,
+     *  and (if Null) is `that` inhabited by null?
+     *  If this is Nothing, of course, it is a
+     *  subclass of `that` by definition.
+     *
+     *  TODO - what is implied by the fact that AnyVal now has
+     *  infinitely many non-bottom subclasses, not only 9?
+     */
+    def isBottomSubClass(that: Symbol) = (
+         (this eq NothingClass)
+      || (this eq NullClass) && that.isClass && (that ne NothingClass) && !(that isNonBottomSubClass AnyValClass)
+    )
+
     /** Overridden in NullClass and NothingClass for custom behavior.
      */
     def isSubClass(that: Symbol) = isNonBottomSubClass(that)
diff --git a/src/reflect/scala/reflect/internal/TreeGen.scala b/src/reflect/scala/reflect/internal/TreeGen.scala
index b2269e476f..d3e486311e 100644
--- a/src/reflect/scala/reflect/internal/TreeGen.scala
+++ b/src/reflect/scala/reflect/internal/TreeGen.scala
@@ -277,7 +277,7 @@ abstract class TreeGen extends macros.TreeBuilder {
 
   /** Builds a tuple */
   def mkTuple(elems: List[Tree]): Tree =
-    if (elems.isEmpty) Literal(Constant())
+    if (elems.isEmpty) Literal(Constant(()))
     else Apply(
       Select(mkAttributedRef(TupleClass(elems.length).caseModule), nme.apply),
       elems)
diff --git a/src/reflect/scala/reflect/internal/Types.scala b/src/reflect/scala/reflect/internal/Types.scala
index e1433d1893..d7ff4faa5d 100644
--- a/src/reflect/scala/reflect/internal/Types.scala
+++ b/src/reflect/scala/reflect/internal/Types.scala
@@ -131,7 +131,6 @@ trait Types
     override def isTrivial = underlying.isTrivial
     override def isHigherKinded: Boolean = underlying.isHigherKinded
     override def typeConstructor: Type = underlying.typeConstructor
-    override def isNotNull = underlying.isNotNull
     override def isError = underlying.isError
     override def isErroneous = underlying.isErroneous
     override def isStable: Boolean = underlying.isStable
@@ -187,7 +186,6 @@ trait Types
     override def params: List[Symbol] = List()
     override def paramTypes: List[Type] = List()
     override def typeArgs = underlying.typeArgs
-    override def notNull = maybeRewrap(underlying.notNull)
     override def instantiateTypeParams(formals: List[Symbol], actuals: List[Type]) = underlying.instantiateTypeParams(formals, actuals)
     override def skolemizeExistential(owner: Symbol, origin: AnyRef) = underlying.skolemizeExistential(owner, origin)
     override def normalize = maybeRewrap(underlying.normalize)
@@ -275,9 +273,6 @@ trait Types
      */
     def isVolatile: Boolean = false
 
-    /** Is this type guaranteed not to have `null` as a value? */
-    def isNotNull: Boolean = false
-
     /** Is this type a structural refinement type (it ''refines'' members that have not been inherited) */
     def isStructuralRefinement: Boolean = false
 
@@ -462,13 +457,6 @@ trait Types
      *  the empty list for all other types */
     def boundSyms: immutable.Set[Symbol] = emptySymbolSet
 
-    /** Mixin a NotNull trait unless type already has one
-     *  ...if the option is given, since it is causing typing bugs.
-     */
-    def notNull: Type =
-      if (!settings.Ynotnull.value || isNotNull || phase.erasedTypes) this
-      else NotNullType(this)
-
     /** Replace formal type parameter symbols with actual type arguments.
      *
      * Amounts to substitution except for higher-kinded types. (See overridden method in TypeRef) -- @M
@@ -1209,17 +1197,6 @@ trait Types
     override def baseTypeSeq: BaseTypeSeq = supertype.baseTypeSeq
     override def baseTypeSeqDepth: Int = supertype.baseTypeSeqDepth
     override def baseClasses: List[Symbol] = supertype.baseClasses
-    override def isNotNull = supertype.isNotNull
-  }
-
-  case class NotNullType(override val underlying: Type) extends SubType with RewrappingTypeProxy {
-    def supertype = underlying
-    protected def rewrap(newtp: Type): Type = NotNullType(newtp)
-    override def isNotNull: Boolean = true
-    override def notNull = this
-    override def deconst: Type = underlying //todo: needed?
-    override def safeToString: String = underlying.toString + " with NotNull"
-    override def kind = "NotNullType"
   }
 
   /** A base class for types that represent a single value
@@ -1324,7 +1301,6 @@ trait Types
     }
 
     override def isTrivial: Boolean = sym.isPackageClass
-    override def isNotNull = true
     override def typeSymbol = sym
     override def underlying: Type = sym.typeOfThis
     override def isVolatile = false
@@ -1363,7 +1339,6 @@ trait Types
     }
     override def isGround = sym.isPackageClass || pre.isGround
 
-    override def isNotNull = underlying.isNotNull
     private[reflect] var underlyingCache: Type = NoType
     private[reflect] var underlyingPeriod = NoPeriod
     override def underlying: Type = {
@@ -1430,8 +1405,6 @@ trait Types
       if (trivial == UNKNOWN) trivial = fromBoolean(thistpe.isTrivial && supertpe.isTrivial)
       toBoolean(trivial)
     }
-    override def isNotNull = true
-
     override def typeSymbol = thistpe.typeSymbol
     override def underlying = supertpe
     override def prefix: Type = supertpe.prefix
@@ -1544,7 +1517,6 @@ trait Types
     }
 
     override def narrow: Type = typeSymbol.thisType
-    override def isNotNull: Boolean = parents exists typeIsNotNull
 
     override def isStructuralRefinement: Boolean =
       typeSymbol.isAnonOrRefinementClass && (decls exists symbolIsPossibleInRefinement)
@@ -1988,8 +1960,7 @@ trait Types
     override def underlying: Type = value.tpe
     assert(underlying.typeSymbol != UnitClass)
     override def isTrivial: Boolean = true
-    override def isNotNull = value.value != null
-    override def deconst: Type = underlying
+    override def deconst: Type = underlying.deconst
     override def safeToString: String =
       underlying.toString + "(" + value.escapedStringValue + ")"
     override def kind = "ConstantType"
@@ -2042,7 +2013,6 @@ trait Types
 
       narrowedCache
     }
-    final override def isNotNull = true
     override protected def finishPrefix(rest: String) = objectPrefix + rest
     override def directObjectString = super.safeToString
     override def toLongString = toString
@@ -2347,9 +2317,6 @@ trait Types
     override def typeSymbol       = sym
     override def typeSymbolDirect = sym
 
-    override def isNotNull =
-      sym.isModuleClass || sym == NothingClass || (sym isNonBottomSubClass NotNullClass) || super.isNotNull
-
     override def parents: List[Type] = {
       val cache = parentsCache
       if (parentsPeriod == currentPeriod && cache != null) cache
@@ -2858,10 +2825,10 @@ trait Types
        *  See SI-5359.
        */
       val bounds  = tparam.info.bounds
-      /** We can seed the type constraint with the type parameter
-       *  bounds as long as the types are concrete.  This should lower
-       *  the complexity of the search even if it doesn't improve
-       *  any results.
+      /* We can seed the type constraint with the type parameter
+       * bounds as long as the types are concrete.  This should lower
+       * the complexity of the search even if it doesn't improve
+       * any results.
        */
       if (propagateParameterBoundsToTypeVars) {
         val exclude = bounds.isEmptyBounds || (bounds exists typeIsNonClassType)
@@ -3566,7 +3533,7 @@ trait Types
     if (args.isEmpty)
       return tycon //@M! `if (args.isEmpty) tycon' is crucial (otherwise we create new types in phases after typer and then they don't get adapted (??))
 
-    /** Disabled - causes cycles in tcpoly tests. */
+    /* Disabled - causes cycles in tcpoly tests. */
     if (false && isDefinitionsInitialized) {
       assert(isUseableAsTypeArgs(args), {
         val tapp_s = s"""$tycon[${args mkString ", "}]"""
@@ -4084,24 +4051,22 @@ trait Types
     corresponds3(tps1, tps2, tparams map (_.variance))(isSubArg)
   }
 
-  protected[internal] def containsNull(sym: Symbol): Boolean =
-    sym.isClass && sym != NothingClass &&
-    !(sym isNonBottomSubClass AnyValClass) &&
-    !(sym isNonBottomSubClass NotNullClass)
-
-  def specializesSym(tp: Type, sym: Symbol, depth: Int): Boolean =
-    tp.typeSymbol == NothingClass ||
-    tp.typeSymbol == NullClass && containsNull(sym.owner) || {
-      def specializedBy(membr: Symbol): Boolean =
-        membr == sym || specializesSym(tp.narrow, membr, sym.owner.thisType, sym, depth)
-      val member = tp.nonPrivateMember(sym.name)
+  def specializesSym(tp: Type, sym: Symbol, depth: Int): Boolean = {
+    def directlySpecializedBy(member: Symbol): Boolean = (
+         member == sym
+      || specializesSym(tp.narrow, member, sym.owner.thisType, sym, depth)
+    )
+    // Closure reduction, else this would be simply `member exists directlySpecializedBy`
+    def specializedBy(member: Symbol): Boolean = (
       if (member eq NoSymbol) false
-      else if (member.isOverloaded) member.alternatives exists specializedBy
-      else specializedBy(member)
-      // was
-      // (tp.nonPrivateMember(sym.name).alternatives exists
-      //   (alt => sym == alt || specializesSym(tp.narrow, alt, sym.owner.thisType, sym, depth)))
-    }
+      else if (member.isOverloaded) member.alternatives exists directlySpecializedBy
+      else directlySpecializedBy(member)
+    )
+
+    (    (tp.typeSymbol isBottomSubClass sym.owner)
+      || specializedBy(tp nonPrivateMember sym.name)
+    )
+  }
 
   /** Does member `sym1` of `tp1` have a stronger type
    *  than member `sym2` of `tp2`?
@@ -4514,7 +4479,6 @@ trait Types
 
 // ----- Hoisted closures and convenience methods, for compile time reductions -------
 
-  private[scala] val typeIsNotNull = (tp: Type) => tp.isNotNull
   private[scala] val isTypeVar = (tp: Type) => tp.isInstanceOf[TypeVar]
   private[scala] val typeContainsTypeVar = (tp: Type) => tp exists isTypeVar
   private[scala] val typeIsNonClassType = (tp: Type) => tp.typeSymbolDirect.isNonClassType
@@ -4632,7 +4596,7 @@ object TypesStats {
   val singletonBaseTypeSeqCount = Statistics.newSubCounter("  of which for singletons", baseTypeSeqCount)
   val typeOpsStack = Statistics.newTimerStack()
 
-  /** Commented out, because right now this does not inline, so creates a closure which will distort statistics
+  /* Commented out, because right now this does not inline, so creates a closure which will distort statistics
   @inline final def timedTypeOp[T](c: Statistics.StackableTimer)(op: => T): T = {
     val start = Statistics.pushTimer(typeOpsStack, c)
     try op
diff --git a/src/reflect/scala/reflect/internal/pickling/UnPickler.scala b/src/reflect/scala/reflect/internal/pickling/UnPickler.scala
index 3850f965b0..c940d863f7 100644
--- a/src/reflect/scala/reflect/internal/pickling/UnPickler.scala
+++ b/src/reflect/scala/reflect/internal/pickling/UnPickler.scala
@@ -516,18 +516,18 @@ abstract class UnPickler {
       var mods: Modifiers = null
       var name: Name = null
 
-      /** Read a Symbol, Modifiers, and a Name */
+      /* Read a Symbol, Modifiers, and a Name */
       def setSymModsName() {
         symbol = readSymbolRef()
         mods = readModifiersRef()
         name = readNameRef()
       }
-      /** Read a Symbol and a Name */
+      /* Read a Symbol and a Name */
       def setSymName() {
         symbol = readSymbolRef()
         name = readNameRef()
       }
-      /** Read a Symbol */
+      /* Read a Symbol */
       def setSym() {
         symbol = readSymbolRef()
       }
diff --git a/src/reflect/scala/reflect/internal/settings/MutableSettings.scala b/src/reflect/scala/reflect/internal/settings/MutableSettings.scala
index 506edb861e..e7a1ea9311 100644
--- a/src/reflect/scala/reflect/internal/settings/MutableSettings.scala
+++ b/src/reflect/scala/reflect/internal/settings/MutableSettings.scala
@@ -35,7 +35,6 @@ abstract class MutableSettings extends AbsSettings {
   def overrideObjects: BooleanSetting
   def printtypes: BooleanSetting
   def debug: BooleanSetting
-  def Ynotnull: BooleanSetting
   def explaintypes: BooleanSetting
   def verbose: BooleanSetting
   def uniqid: BooleanSetting
diff --git a/src/reflect/scala/reflect/internal/tpe/GlbLubs.scala b/src/reflect/scala/reflect/internal/tpe/GlbLubs.scala
index bdccc75d6d..5bdc5f8a73 100644
--- a/src/reflect/scala/reflect/internal/tpe/GlbLubs.scala
+++ b/src/reflect/scala/reflect/internal/tpe/GlbLubs.scala
@@ -396,7 +396,7 @@ private[internal] trait GlbLubs {
       indent = indent stripSuffix "  "
       println(indent + "lub of " + ts + " is " + res)//debug
     }
-    if (ts forall typeIsNotNull) res.notNull else res
+    res
   }
 
   val GlbFailure = new Throwable
@@ -536,13 +536,9 @@ private[internal] trait GlbLubs {
       }
     }
     // if (settings.debug.value) { println(indent + "glb of " + ts + " at depth "+depth); indent = indent + "  " } //DEBUG
-
     if (Statistics.canEnable) Statistics.incCounter(nestedLubCount)
-    val res = glb0(ts)
-
+    glb0(ts)
     // if (settings.debug.value) { indent = indent.substring(0, indent.length() - 2); log(indent + "glb of " + ts + " is " + res) }//DEBUG
-
-    if (ts exists typeIsNotNull) res.notNull else res
   }
 
   /** All types in list must be polytypes with type parameter lists of
diff --git a/src/reflect/scala/reflect/internal/tpe/TypeComparers.scala b/src/reflect/scala/reflect/internal/tpe/TypeComparers.scala
index 82321f61c2..e9d3ffbf56 100644
--- a/src/reflect/scala/reflect/internal/tpe/TypeComparers.scala
+++ b/src/reflect/scala/reflect/internal/tpe/TypeComparers.scala
@@ -5,6 +5,7 @@ package tpe
 import scala.collection.{ mutable }
 import Flags._
 import util.Statistics
+import scala.annotation.tailrec
 
 trait TypeComparers {
   self: SymbolTable =>
@@ -73,14 +74,17 @@ trait TypeComparers {
     // if (subsametypeRecursions == 0) undoLog.clear()
   }
 
-  def isDifferentTypeConstructor(tp1: Type, tp2: Type): Boolean = tp1 match {
-    case TypeRef(pre1, sym1, _) =>
-      tp2 match {
-        case TypeRef(pre2, sym2, _) => sym1 != sym2 || isDifferentType(pre1, pre2)
-        case _ => true
-      }
-    case _ => true
-  }
+  def isDifferentTypeConstructor(tp1: Type, tp2: Type) = !isSameTypeConstructor(tp1, tp2)
+
+  private def isSameTypeConstructor(tr1: TypeRef, tr2: TypeRef): Boolean = (
+       (tr1.sym == tr2.sym)
+    && !isDifferentType(tr1.pre, tr2.pre)
+  )
+  private def isSameTypeConstructor(tp1: Type, tp2: Type): Boolean = (
+       tp1.isInstanceOf[TypeRef]
+    && tp2.isInstanceOf[TypeRef]
+    && isSameTypeConstructor(tp1.asInstanceOf[TypeRef], tp2.asInstanceOf[TypeRef])
+  )
 
   /** Do `tp1` and `tp2` denote equivalent types? */
   def isSameType(tp1: Type, tp2: Type): Boolean = try {
@@ -392,16 +396,19 @@ trait TypeComparers {
     if (isSingleType(tp1) && isSingleType(tp2) || isConstantType(tp1) && isConstantType(tp2)) return tp1 =:= tp2
     if (tp1.isHigherKinded || tp2.isHigherKinded) return isHKSubType(tp1, tp2, depth)
 
-    /** First try, on the right:
-      *   - unwrap Annotated types, BoundedWildcardTypes,
-      *   - bind TypeVars  on the right, if lhs is not Annotated nor BoundedWildcard
-      *   - handle common cases for first-kind TypeRefs on both sides as a fast path.
-      */
+    /* First try, on the right:
+     *   - unwrap Annotated types, BoundedWildcardTypes,
+     *   - bind TypeVars  on the right, if lhs is not Annotated nor BoundedWildcard
+     *   - handle common cases for first-kind TypeRefs on both sides as a fast path.
+     */
     def firstTry = tp2 match {
       // fast path: two typerefs, none of them HK
       case tr2: TypeRef =>
         tp1 match {
           case tr1: TypeRef =>
+            // TODO - dedicate a method to TypeRef/TypeRef subtyping.
+            // These typerefs are pattern matched up and down far more
+            // than is necessary.
             val sym1 = tr1.sym
             val sym2 = tr2.sym
             val pre1 = tr1.pre
@@ -438,11 +445,11 @@ trait TypeComparers {
         secondTry
     }
 
-    /** Second try, on the left:
-      *   - unwrap AnnotatedTypes, BoundedWildcardTypes,
-      *   - bind typevars,
-      *   - handle existential types by skolemization.
-      */
+    /* Second try, on the left:
+     *   - unwrap AnnotatedTypes, BoundedWildcardTypes,
+     *   - bind typevars,
+     *   - handle existential types by skolemization.
+     */
     def secondTry = tp1 match {
       case AnnotatedType(_, _, _) =>
         isSubType(tp1.withoutAnnotations, tp2.withoutAnnotations, depth) &&
@@ -464,35 +471,27 @@ trait TypeComparers {
 
     def thirdTryRef(tp1: Type, tp2: TypeRef): Boolean = {
       val sym2 = tp2.sym
+      def retry(lhs: Type, rhs: Type)   = isSubType(lhs, rhs, depth)
+      def abstractTypeOnRight(lo: Type) = isDifferentTypeConstructor(tp2, lo) && retry(tp1, lo)
+      def classOnRight                  = (
+        if (isRawType(tp2)) retry(tp1, rawToExistential(tp2))
+        else if (sym2.isRefinementClass) retry(tp1, sym2.info)
+        else fourthTry
+      )
       sym2 match {
-        case NotNullClass => tp1.isNotNull
-        case SingletonClass => tp1.isStable || fourthTry
-        case _: ClassSymbol =>
-          if (isRawType(tp2))
-            isSubType(tp1, rawToExistential(tp2), depth)
-          else if (sym2.name == tpnme.REFINE_CLASS_NAME)
-            isSubType(tp1, sym2.info, depth)
-          else
-            fourthTry
-        case _: TypeSymbol =>
-          if (sym2 hasFlag DEFERRED) {
-            val tp2a = tp2.bounds.lo
-            isDifferentTypeConstructor(tp2, tp2a) &&
-              isSubType(tp1, tp2a, depth) ||
-              fourthTry
-          } else {
-            isSubType(tp1.normalize, tp2.normalize, depth)
-          }
-        case _ =>
-          fourthTry
+        case SingletonClass                   => tp1.isStable || fourthTry
+        case _: ClassSymbol                   => classOnRight
+        case _: TypeSymbol if sym2.isDeferred => abstractTypeOnRight(tp2.bounds.lo) || fourthTry
+        case _: TypeSymbol                    => retry(tp1.normalize, tp2.normalize)
+        case _                                => fourthTry
       }
     }
 
-    /** Third try, on the right:
-      *   - decompose refined types.
-      *   - handle typerefs, existentials, and notnull types.
-      *   - handle left+right method types, polytypes, typebounds
-      */
+    /* Third try, on the right:
+     *   - decompose refined types.
+     *   - handle typerefs and existentials.
+     *   - handle left+right method types, polytypes, typebounds
+     */
     def thirdTry = tp2 match {
       case tr2: TypeRef =>
         thirdTryRef(tp1, tr2)
@@ -501,8 +500,6 @@ trait TypeComparers {
           (rt2.decls forall (specializesSym(tp1, _, depth)))
       case et2: ExistentialType =>
         et2.withTypeVars(isSubType(tp1, _, depth), depth) || fourthTry
-      case nn2: NotNullType =>
-        tp1.isNotNull && isSubType(tp1, nn2.underlying, depth)
       case mt2: MethodType =>
         tp1 match {
           case mt1 @ MethodType(params1, res1) =>
@@ -535,47 +532,40 @@ trait TypeComparers {
         fourthTry
     }
 
-    /** Fourth try, on the left:
-      *   - handle typerefs, refined types, notnull and singleton types.
-      */
-    def fourthTry = tp1 match {
-      case tr1 @ TypeRef(pre1, sym1, _) =>
-        sym1 match {
-          case NothingClass => true
-          case NullClass =>
-            tp2 match {
-              case TypeRef(_, sym2, _) =>
-                containsNull(sym2)
-              case _ =>
-                isSingleType(tp2) && isSubType(tp1, tp2.widen, depth)
-            }
-          case _: ClassSymbol =>
-            if (isRawType(tp1))
-              isSubType(rawToExistential(tp1), tp2, depth)
-            else if (sym1.isModuleClass) tp2 match {
-              case SingleType(pre2, sym2) => equalSymsAndPrefixes(sym1.sourceModule, pre1, sym2, pre2)
-              case _                      => false
-            }
-            else if (sym1.isRefinementClass)
-              isSubType(sym1.info, tp2, depth)
-            else false
-
-          case _: TypeSymbol =>
-            if (sym1 hasFlag DEFERRED) {
-              val tp1a = tp1.bounds.hi
-              isDifferentTypeConstructor(tp1, tp1a) && isSubType(tp1a, tp2, depth)
-            } else {
-              isSubType(tp1.normalize, tp2.normalize, depth)
-            }
-          case _ =>
-            false
-        }
-      case RefinedType(parents1, _) =>
-        parents1 exists (isSubType(_, tp2, depth))
-      case _: SingletonType | _: NotNullType =>
-        isSubType(tp1.underlying, tp2, depth)
-      case _ =>
-        false
+    /* Fourth try, on the left:
+     *   - handle typerefs, refined types, and singleton types.
+     */
+    def fourthTry = {
+      def retry(lhs: Type, rhs: Type)  = isSubType(lhs, rhs, depth)
+      def abstractTypeOnLeft(hi: Type) = isDifferentTypeConstructor(tp1, hi) && retry(hi, tp2)
+
+      tp1 match {
+        case tr1 @ TypeRef(pre1, sym1, _) =>
+          def nullOnLeft = tp2 match {
+            case TypeRef(_, sym2, _) => sym1 isBottomSubClass sym2
+            case _                   => isSingleType(tp2) && retry(tp1, tp2.widen)
+          }
+          def moduleOnLeft = tp2 match {
+            case SingleType(pre2, sym2) => equalSymsAndPrefixes(sym1.sourceModule, pre1, sym2, pre2)
+            case _                      => false
+          }
+          def classOnLeft = (
+            if (isRawType(tp1)) retry(rawToExistential(tp1), tp2)
+            else if (sym1.isModuleClass) moduleOnLeft
+            else sym1.isRefinementClass && retry(sym1.info, tp2)
+          )
+          sym1 match {
+            case NothingClass                     => true
+            case NullClass                        => nullOnLeft
+            case _: ClassSymbol                   => classOnLeft
+            case _: TypeSymbol if sym1.isDeferred => abstractTypeOnLeft(tp1.bounds.hi)
+            case _: TypeSymbol                    => retry(tp1.normalize, tp2.normalize)
+            case _                                => false
+          }
+        case RefinedType(parents, _) => parents exists (retry(_, tp2))
+        case _: SingletonType        => retry(tp1.underlying, tp2)
+        case _                       => false
+      }
     }
 
     firstTry
@@ -583,9 +573,9 @@ trait TypeComparers {
 
 
   def isWeakSubType(tp1: Type, tp2: Type) =
-    tp1.deconst.normalize match {
+    tp1.dealiasWiden match {
       case TypeRef(_, sym1, _) if isNumericValueClass(sym1) =>
-        tp2.deconst.normalize match {
+        tp2.deconst.dealias match {
           case TypeRef(_, sym2, _) if isNumericValueClass(sym2) =>
             isNumericSubClass(sym1, sym2)
           case tv2 @ TypeVar(_, _) =>
@@ -594,7 +584,7 @@ trait TypeComparers {
             isSubType(tp1, tp2)
         }
       case tv1 @ TypeVar(_, _) =>
-        tp2.deconst.normalize match {
+        tp2.deconst.dealias match {
           case TypeRef(_, sym2, _) if isNumericValueClass(sym2) =>
             tv1.registerBound(tp2, isLowerBound = false, isNumericBound = true)
           case _ =>
@@ -604,14 +594,18 @@ trait TypeComparers {
         isSubType(tp1, tp2)
     }
 
-  /** The isNumericValueType tests appear redundant, but without them
-    *  test/continuations-neg/function3.scala goes into an infinite loop.
-    *  (Even if the calls are to typeSymbolDirect.)
-    */
-  def isNumericSubType(tp1: Type, tp2: Type): Boolean = (
-    isNumericValueType(tp1)
-      && isNumericValueType(tp2)
-      && isNumericSubClass(tp1.typeSymbol, tp2.typeSymbol)
-    )
-
+  def isNumericSubType(tp1: Type, tp2: Type) = (
+    isNumericSubClass(primitiveBaseClass(tp1.dealiasWiden), primitiveBaseClass(tp2.dealias))
+   )
+
+  /** If the given type has a primitive class among its base classes,
+   *  the symbol of that class. Otherwise, NoSymbol.
+   */
+  private def primitiveBaseClass(tp: Type): Symbol = {
+    @tailrec def loop(bases: List[Symbol]): Symbol = bases match {
+      case Nil     => NoSymbol
+      case x :: xs => if (isPrimitiveValueClass(x)) x else loop(xs)
+    }
+    loop(tp.baseClasses)
+  }
 }
diff --git a/src/reflect/scala/reflect/internal/tpe/TypeMaps.scala b/src/reflect/scala/reflect/internal/tpe/TypeMaps.scala
index 51363c0f82..0f9db31ec1 100644
--- a/src/reflect/scala/reflect/internal/tpe/TypeMaps.scala
+++ b/src/reflect/scala/reflect/internal/tpe/TypeMaps.scala
@@ -174,10 +174,6 @@ private[internal] trait TypeMaps {
       case tv@TypeVar(_, constr) =>
         if (constr.instValid) this(constr.inst)
         else tv.applyArgs(mapOverArgs(tv.typeArgs, tv.params))  //@M !args.isEmpty implies !typeParams.isEmpty
-      case NotNullType(tp) =>
-        val tp1 = this(tp)
-        if (tp1 eq tp) tp
-        else NotNullType(tp1)
       case AnnotatedType(annots, atp, selfsym) =>
         val annots1 = mapOverAnnotations(annots)
         val atp1 = this(atp)
@@ -1037,7 +1033,7 @@ private[internal] trait TypeMaps {
           devWarning(s"$pre.$sym no longer exist at phase $phase")
           throw new MissingTypeControl // For build manager and presentation compiler purposes
         }
-        /** The two symbols have the same fully qualified name */
+        /* The two symbols have the same fully qualified name */
         def corresponds(sym1: Symbol, sym2: Symbol): Boolean =
           sym1.name == sym2.name && (sym1.isPackageClass || corresponds(sym1.owner, sym2.owner))
         if (!corresponds(sym.owner, rebind0.owner)) {
@@ -1135,7 +1131,6 @@ private[internal] trait TypeMaps {
       case TypeBounds(_, _) => mapOver(tp)
       case TypeVar(_, _) => mapOver(tp)
       case AnnotatedType(_,_,_) => mapOver(tp)
-      case NotNullType(_) => mapOver(tp)
       case ExistentialType(_, _) => mapOver(tp)
       case _ => tp
     }
diff --git a/src/reflect/scala/reflect/internal/transform/Erasure.scala b/src/reflect/scala/reflect/internal/transform/Erasure.scala
index d83b4d71d9..b8a8e4d0c0 100644
--- a/src/reflect/scala/reflect/internal/transform/Erasure.scala
+++ b/src/reflect/scala/reflect/internal/transform/Erasure.scala
@@ -125,7 +125,7 @@ trait Erasure {
           if (unboundedGenericArrayLevel(tp) == 1) ObjectClass.tpe
           else if (args.head.typeSymbol.isBottomClass) ObjectArray
           else typeRef(apply(pre), sym, args map applyInArray)
-        else if (sym == AnyClass || sym == AnyValClass || sym == SingletonClass || sym == NotNullClass) ErasedObject
+        else if (sym == AnyClass || sym == AnyValClass || sym == SingletonClass) ErasedObject
         else if (sym == UnitClass) erasedTypeRef(BoxedUnitClass)
         else if (sym.isRefinementClass) apply(mergeParents(tp.parents))
         else if (sym.isDerivedValueClass) eraseDerivedValueClassRef(tref)
diff --git a/src/reflect/scala/reflect/io/ZipArchive.scala b/src/reflect/scala/reflect/io/ZipArchive.scala
index 1342fde3c5..11d04538e9 100644
--- a/src/reflect/scala/reflect/io/ZipArchive.scala
+++ b/src/reflect/scala/reflect/io/ZipArchive.scala
@@ -259,7 +259,11 @@ final class ManifestResources(val url: URL) extends ZipArchive(null) {
   }
 
   def name  = path
-  def path: String = url.getPath() match { case s => s.substring(0, s.lastIndexOf('!')) }
+  def path: String = {
+    val s = url.getPath
+    val n = s.lastIndexOf('!')
+    s.substring(0, n)
+  }
   def input = url.openStream()
   def lastModified =
     try url.openConnection().getLastModified()
diff --git a/src/reflect/scala/reflect/runtime/JavaMirrors.scala b/src/reflect/scala/reflect/runtime/JavaMirrors.scala
index c5c28ad3e9..2e38caaf5d 100644
--- a/src/reflect/scala/reflect/runtime/JavaMirrors.scala
+++ b/src/reflect/scala/reflect/runtime/JavaMirrors.scala
@@ -60,7 +60,7 @@ private[reflect] trait JavaMirrors extends internal.SymbolTable with api.JavaUni
 
   /** The API of a mirror for a reflective universe */
   class JavaMirror(owner: Symbol,
-    /** Class loader that is a mastermind behind the reflexive mirror */
+    /* Class loader that is a mastermind behind the reflexive mirror */
     val classLoader: ClassLoader
   ) extends Roots(owner) with super.JavaMirror { thisMirror =>
 
diff --git a/src/reflect/scala/reflect/runtime/Settings.scala b/src/reflect/scala/reflect/runtime/Settings.scala
index 5d58fa96d6..6714bae1e0 100644
--- a/src/reflect/scala/reflect/runtime/Settings.scala
+++ b/src/reflect/scala/reflect/runtime/Settings.scala
@@ -33,7 +33,6 @@ private[reflect] class Settings extends MutableSettings {
   val XfullLubs         = new BooleanSetting(false)
   val XnoPatmatAnalysis = new BooleanSetting(false)
   val Xprintpos         = new BooleanSetting(false)
-  val Ynotnull          = new BooleanSetting(false)
   val Yshowsymkinds     = new BooleanSetting(false)
   val Yposdebug         = new BooleanSetting(false)
   val Yrangepos         = new BooleanSetting(false)
diff --git a/src/repl/scala/tools/nsc/interpreter/ExprTyper.scala b/src/repl/scala/tools/nsc/interpreter/ExprTyper.scala
index 9edd54b939..55182a4f95 100644
--- a/src/repl/scala/tools/nsc/interpreter/ExprTyper.scala
+++ b/src/repl/scala/tools/nsc/interpreter/ExprTyper.scala
@@ -13,7 +13,6 @@ trait ExprTyper {
 
   import repl._
   import global.{ reporter => _, Import => _, _ }
-  import definitions._
   import syntaxAnalyzer.UnitParser
   import naming.freshInternalVarName
 
diff --git a/src/repl/scala/tools/nsc/interpreter/IBindings.java b/src/repl/scala/tools/nsc/interpreter/IBindings.java
new file mode 100644
index 0000000000..b4cee4b957
--- /dev/null
+++ b/src/repl/scala/tools/nsc/interpreter/IBindings.java
@@ -0,0 +1,45 @@
+/* NSC -- new Scala compiler
+ * Copyright 2005-2013 LAMP/EPFL
+ * @author Raphael Jolly
+ */
+
+package scala.tools.nsc.interpreter;
+
+import java.util.Map;
+import java.util.AbstractMap;
+import java.util.Set;
+import java.util.AbstractSet;
+import java.util.Iterator;
+import java.util.NoSuchElementException;
+import javax.script.Bindings;
+
+abstract class IBindings extends AbstractMap<String, Object> implements Bindings {
+    public Set<Map.Entry<String, Object>> entrySet() {
+        return new AbstractSet<Map.Entry<String, Object>>() {
+            public int size() {
+                return 0;
+            }
+
+            public Iterator<Map.Entry<String, Object>> iterator() {
+                return new Iterator<Map.Entry<String, Object>>() {
+                    public boolean hasNext() {
+                        return false;
+                    }
+
+                    public Map.Entry<String, Object> next() {
+                        throw new NoSuchElementException();
+                    }
+
+                    public void remove() {
+                        throw new UnsupportedOperationException();
+                    }
+                };
+            }
+
+            public boolean add(Map.Entry<String, Object> e) {
+                IBindings.this.put(e.getKey(), e.getValue());
+                return true;
+            }
+        };
+    }
+}
diff --git a/src/repl/scala/tools/nsc/interpreter/IMain.scala b/src/repl/scala/tools/nsc/interpreter/IMain.scala
index c92777c13e..d2b6cdd7f0 100644
--- a/src/repl/scala/tools/nsc/interpreter/IMain.scala
+++ b/src/repl/scala/tools/nsc/interpreter/IMain.scala
@@ -21,7 +21,7 @@ import scala.tools.nsc.util.Exceptional.unwrap
 import scala.collection.{ mutable, immutable }
 import scala.reflect.BeanProperty
 import scala.util.Properties.versionString
-import javax.script.{AbstractScriptEngine, Bindings, ScriptContext, ScriptEngine, ScriptEngineFactory, ScriptException, SimpleBindings, CompiledScript, Compilable}
+import javax.script.{AbstractScriptEngine, Bindings, ScriptContext, ScriptEngine, ScriptEngineFactory, ScriptException, CompiledScript, Compilable}
 import java.io.{ StringWriter, Reader }
 import java.util.Arrays
 import IMain._
@@ -62,9 +62,10 @@ import StdReplTags._
  *  @author Moez A. Abdel-Gawad
  *  @author Lex Spoon
  */
-class IMain(@BeanProperty val factory: ScriptEngineFactory, initialSettings: Settings, protected val out: JPrintWriter) extends AbstractScriptEngine(new SimpleBindings) with Compilable with Imports {
+class IMain(@BeanProperty val factory: ScriptEngineFactory, initialSettings: Settings, protected val out: JPrintWriter) extends AbstractScriptEngine with Compilable with Imports {
   imain =>
 
+  setBindings(createBindings, ScriptContext.ENGINE_SCOPE)
   object replOutput extends ReplOutput(settings.Yreploutdir) { }
 
   @deprecated("Use replOutput.dir instead", "2.11.0")
@@ -554,7 +555,7 @@ class IMain(@BeanProperty val factory: ScriptEngineFactory, initialSettings: Set
   @throws(classOf[ScriptException])
   def compile(script: String): CompiledScript = {
     if (!bound) {
-      quietBind("bindings", getBindings(ScriptContext.ENGINE_SCOPE))
+      quietBind("engine", this.asInstanceOf[ScriptEngine])
       bound = true
     }
     val cat = code + script
@@ -969,7 +970,18 @@ class IMain(@BeanProperty val factory: ScriptEngineFactory, initialSettings: Set
     override def toString = "Request(line=%s, %s trees)".format(line, trees.size)
   }
 
-  def createBindings: Bindings = new SimpleBindings
+  def createBindings: Bindings = new IBindings {
+    override def put(name: String, value: Object): Object = {
+      val n = name.indexOf(":")
+      val p: NamedParam = if (n < 0) (name, value) else {
+        val nme = name.substring(0, n).trim
+        val tpe = name.substring(n + 1).trim
+        NamedParamClass(nme, tpe, value)
+      }
+      if (!p.name.startsWith("javax.script")) bind(p)
+      null
+    }
+  }
 
   @throws(classOf[ScriptException])
   def eval(script: String, context: ScriptContext): Object = compile(script).eval(context)
diff --git a/src/repl/scala/tools/nsc/interpreter/MemberHandlers.scala b/src/repl/scala/tools/nsc/interpreter/MemberHandlers.scala
index 84a47311e2..c6f0cca481 100644
--- a/src/repl/scala/tools/nsc/interpreter/MemberHandlers.scala
+++ b/src/repl/scala/tools/nsc/interpreter/MemberHandlers.scala
@@ -7,7 +7,6 @@ package scala.tools.nsc
 package interpreter
 
 import scala.collection.{ mutable, immutable }
-import scala.reflect.internal.Flags._
 import scala.language.implicitConversions
 
 trait MemberHandlers {
diff --git a/src/scaladoc/scala/tools/nsc/doc/base/CommentFactoryBase.scala b/src/scaladoc/scala/tools/nsc/doc/base/CommentFactoryBase.scala
index 2064d86860..ef0a013ff2 100755
--- a/src/scaladoc/scala/tools/nsc/doc/base/CommentFactoryBase.scala
+++ b/src/scaladoc/scala/tools/nsc/doc/base/CommentFactoryBase.scala
@@ -679,7 +679,6 @@ trait CommentFactoryBase { this: MemberLookupBase =>
       val SchemeUri = """([a-z]+:.*)""".r
       jump("[[")
       val parens = 2 + repeatJump('[')
-      val start = "[" * parens
       val stop  = "]" * parens
       //println("link with " + parens + " matching parens")
       val target = readUntil { check(stop) || check(" ") }
diff --git a/src/scaladoc/scala/tools/nsc/doc/base/LinkTo.scala b/src/scaladoc/scala/tools/nsc/doc/base/LinkTo.scala
index c11179800c..3d80f9da52 100755
--- a/src/scaladoc/scala/tools/nsc/doc/base/LinkTo.scala
+++ b/src/scaladoc/scala/tools/nsc/doc/base/LinkTo.scala
@@ -6,8 +6,6 @@ package scala.tools.nsc
 package doc
 package base
 
-import scala.collection._
-
 sealed trait LinkTo
 final case class LinkToMember[Mbr, Tpl](mbr: Mbr, tpl: Tpl) extends LinkTo
 final case class LinkToTpl[Tpl](tpl: Tpl) extends LinkTo
diff --git a/src/scaladoc/scala/tools/nsc/doc/base/MemberLookupBase.scala b/src/scaladoc/scala/tools/nsc/doc/base/MemberLookupBase.scala
index 8d80333195..671518fbc6 100755
--- a/src/scaladoc/scala/tools/nsc/doc/base/MemberLookupBase.scala
+++ b/src/scaladoc/scala/tools/nsc/doc/base/MemberLookupBase.scala
@@ -46,7 +46,7 @@ trait MemberLookupBase {
     } else ""
 
   def memberLookup(pos: Position, query: String, siteOpt: Option[Symbol]): LinkTo = {
-    var members = breakMembers(query)
+    val members = breakMembers(query)
 
     // (1) First look in the root package, as most of the links are qualified
     val fromRoot = lookupInRootPackage(pos, members)
diff --git a/src/scaladoc/scala/tools/nsc/doc/model/ModelFactory.scala b/src/scaladoc/scala/tools/nsc/doc/model/ModelFactory.scala
index 1df725636a..895cc84f39 100644
--- a/src/scaladoc/scala/tools/nsc/doc/model/ModelFactory.scala
+++ b/src/scaladoc/scala/tools/nsc/doc/model/ModelFactory.scala
@@ -4,7 +4,6 @@ package scala.tools.nsc
 package doc
 package model
 
-import base._
 import base.comment._
 import diagram._
 
diff --git a/src/scaladoc/scala/tools/nsc/doc/model/ModelFactoryImplicitSupport.scala b/src/scaladoc/scala/tools/nsc/doc/model/ModelFactoryImplicitSupport.scala
index 868c2fc3a4..71b0a00e0a 100644
--- a/src/scaladoc/scala/tools/nsc/doc/model/ModelFactoryImplicitSupport.scala
+++ b/src/scaladoc/scala/tools/nsc/doc/model/ModelFactoryImplicitSupport.scala
@@ -314,7 +314,7 @@ trait ModelFactoryImplicitSupport {
               })
             case other =>
               // this is likely an error on the lub/glb side
-              error("Scaladoc implicits: Error computing lub/glb for: " + (tparam, constr) + ":\n" + other)
+              error("Scaladoc implicits: Error computing lub/glb for: " + ((tparam, constr)) + ":\n" + other)
               Nil
           }
         }
diff --git a/src/scalap/scala/tools/scalap/JavaWriter.scala b/src/scalap/scala/tools/scalap/JavaWriter.scala
index d64c54a0ea..772cf6eacd 100644
--- a/src/scalap/scala/tools/scalap/JavaWriter.scala
+++ b/src/scalap/scala/tools/scalap/JavaWriter.scala
@@ -17,16 +17,15 @@ class JavaWriter(classfile: Classfile, writer: Writer) extends CodeWriter(writer
 
   def flagsToStr(clazz: Boolean, flags: Int): String = {
     val buffer = new StringBuffer()
-    var x: StringBuffer = buffer
     if (((flags & 0x0007) == 0) &&
       ((flags & 0x0002) != 0))
-      x = buffer.append("private ")
+      buffer.append("private ")
     if ((flags & 0x0004) != 0)
-      x = buffer.append("protected ")
+      buffer.append("protected ")
     if ((flags & 0x0010) != 0)
-      x = buffer.append("final ")
+      buffer.append("final ")
     if ((flags & 0x0400) != 0)
-      x = if (clazz) buffer.append("abstract ")
+      if (clazz) buffer.append("abstract ")
           else buffer.append("/*deferred*/ ")
     buffer.toString()
   }