Backport of SI-6846.

Squashed commit of the following:

commit 55806cc0e6177820c12a35a18b4f2a12dc07bb39
Author: Paul Phillips <paulp@improving.org>
Date:   Wed Dec 19 07:32:19 2012 -0800

    SI-6846, regression in type constructor inference.

    In 658ba1b4e6 some inference was gained and some was lost.
    In this commit we regain what was lost and gain even more.
    Dealiasing and widening should be fully handled now, as
    illustrated by the test case.
    (cherry picked from commit dbebcd509e4013ce02655a2687b27d0967b3650e)

commit e6ef58447d0f4ef6de956fcc03ee283bb9028c02
Author: Paul Phillips <paulp@improving.org>
Date:   Fri Dec 21 15:11:29 2012 -0800

    Cleaning up type alias usage.

    I determined that many if not most of the calls to .normalize
    have no intent beyond dealiasing the type. In light of this I
    went call site to call site knocking on doors and asking why
    exactly they were calling any of

      .normalize
      .widen.normalize
      .normalize.widen

    and if I didn't like their answers they found themselves
    introduced to 'dropAliasesAndSingleTypes', the recursive widener
    and dealiaser which I concluded is necessary after all.

    Discovered that the object called 'deAlias' actually depends
    upon calling 'normalize', not 'dealias'. Decided this was
    sufficient cause to rename it to 'normalizeAliases'.

    Created dealiasWiden and dealiasWidenChain.

    Dropped dropAliasesAndSingleTypes in favor of methods
    on Type alongside dealias and widen (Type#dealiasWiden).
    These should reduce the number of "hey, the type alias doesn't work" bugs.

    (cherry picked from commit 3bf51189f979eb0dd41744ca844fd12dfdaa0dee)

    Conflicts:
    	src/compiler/scala/tools/nsc/interpreter/CompletionOutput.scala

commit c1d8803cea1523f458730103386d8e14324a9446
Author: Paul Phillips <paulp@improving.org>
Date:   Sat Dec 22 08:13:48 2012 -0800

    Shored up a hidden dealiasing dependency.

    Like the comment says:

    // This way typedNew always returns a dealiased type. This
    // used to happen by accident for instantiations without type
    // arguments due to ad hoc code in typedTypeConstructor, and
    // annotations depended on it (to the extent that they worked,
    // which they did not when given a parameterized type alias
    // which dealiased to an annotation.) typedTypeConstructor
    // dealiases nothing now, but it makes sense for a "new" to
    // always be given a dealiased type.

    PS:
    Simply running the test suite is becoming more difficult all
    the time. Running "ant test" includes time consuming activities
    of niche interest such as all the osgi tests, but test.suite
    manages to miss the continuations tests.
    (cherry picked from commit 422f461578ae0547181afe6d2c0c52ea1071d37b)

commit da4748502792b260161baa10939554564c488051
Author: Paul Phillips <paulp@improving.org>
Date:   Fri Dec 21 12:39:02 2012 -0800

    Fix and simplify typedTypeConstructor.

    Investigating the useful output of devWarning (-Xdev people,
    it's good for you) led back to this comment:

      "normalize to get rid of type aliases"

    You may know that this is not all the normalizing does.
    Normalizing also turns TypeRefs with unapplied arguments
    (type constructors) into PolyTypes. That means that when
    typedParentType would call typedTypeConstructor it would
    find its parent had morphed into a PolyType. Not that it
    noticed; it would blithely continue and unwittingly discard
    the type arguments by way of appliedType (which smoothly
    logged the incident, thank you appliedType.)

    The simplification of typedTypeConstructor:

    There was a whole complicated special treatment of AnyRef
    here which appears to have become unnecessary. Removed special
    treatment and lit a candle for regularity.

    Updated lots of tests regarding newly not-so-special AnyRef.
    (cherry picked from commit 394cc426c1ff1da53146679b4e2995ece52a133e)

commit 1f3c77bacb2fbb3ba9e4ad0a8a733e0f9263b234
Author: Paul Phillips <paulp@improving.org>
Date:   Fri Dec 21 15:06:10 2012 -0800

    Removed dead implementation.

    Another "attractive nuisance" burning off time until I
    realized it was commented out.
    (cherry picked from commit ed40f5cbdf35d09b02898e9c0950b9bd34c1f858)

1 files changed, 14 insertions, 99 deletions

diff --git a/src/compiler/scala/tools/nsc/typechecker/Implicits.scala b/src/compiler/scala/tools/nsc/typechecker/Implicits.scala
index 70a736c91f..10003723fd 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Implicits.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Implicits.scala
@@ -443,8 +443,8 @@ trait Implicits {
       val start = if (Statistics.canEnable) Statistics.startTimer(matchesPtNanos) else null
       val result = normSubType(tp, pt) || isView && {
         pt match {
-          case TypeRef(_, Function1.Sym, args) =>
-            matchesPtView(tp, args.head, args.tail.head, undet)
+          case TypeRef(_, Function1.Sym, arg1 :: arg2 :: Nil) =>
+            matchesPtView(tp, arg1, arg2, undet)
           case _ =>
             false
         }
@@ -488,7 +488,7 @@ trait Implicits {
             loop(restpe, pt)
           else pt match {
             case tr @ TypeRef(pre, sym, args) =>
-              if (sym.isAliasType) loop(tp, pt.normalize)
+              if (sym.isAliasType) loop(tp, pt.dealias)
               else if (sym.isAbstractType) loop(tp, pt.bounds.lo)
               else {
                 val len = args.length - 1
@@ -532,18 +532,15 @@ trait Implicits {
      *  to a final true or false.
      */
     private def isPlausiblySubType(tp1: Type, tp2: Type) = !isImpossibleSubType(tp1, tp2)
-    private def isImpossibleSubType(tp1: Type, tp2: Type) = tp1.normalize.widen match {
-      case tr1 @ TypeRef(_, sym1, _) =>
-        // We can only rule out a subtype relationship if the left hand
-        // side is a class, else we may not know enough.
-        sym1.isClass && (tp2.normalize.widen match {
-          case TypeRef(_, sym2, _) =>
-             sym2.isClass && !(sym1 isWeakSubClass sym2)
-          case RefinedType(parents, decls) =>
-            decls.nonEmpty &&
-            tr1.member(decls.head.name) == NoSymbol
-          case _ => false
-        })
+    private def isImpossibleSubType(tp1: Type, tp2: Type) = tp1.dealiasWiden match {
+      // We can only rule out a subtype relationship if the left hand
+      // side is a class, else we may not know enough.
+      case tr1 @ TypeRef(_, sym1, _) if sym1.isClass =>
+        tp2.dealiasWiden match {
+          case TypeRef(_, sym2, _)         => sym2.isClass && !(sym1 isWeakSubClass sym2)
+          case RefinedType(parents, decls) => decls.nonEmpty && tr1.member(decls.head.name) == NoSymbol
+          case _                           => false
+        }
       case _ => false
     }
 
@@ -1018,7 +1015,7 @@ trait Implicits {
                 args foreach (getParts(_))
               }
             } else if (sym.isAliasType) {
-              getParts(tp.normalize)
+              getParts(tp.dealias)
             } else if (sym.isAbstractType) {
               getParts(tp.bounds.hi)
             }
@@ -1049,88 +1046,6 @@ trait Implicits {
       infoMap
     }
 
-    /** The parts of a type is the smallest set of types that contains
-     *    - the type itself
-     *    - the parts of its immediate components (prefix and argument)
-     *    - the parts of its base types
-     *    - for alias types and abstract types, we take instead the parts
-     *    - of their upper bounds.
-     *  @return For those parts that refer to classes with companion objects that
-     *  can be accessed with unambiguous stable prefixes, the implicits infos
-     *  which are members of these companion objects.
-
-    private def companionImplicits(tp: Type): Infoss = {
-      val partMap = new LinkedHashMap[Symbol, Type]
-      val seen = mutable.HashSet[Type]()  // cycle detection
-
-      /** Enter all parts of `tp` into `parts` set.
-       *  This method is performance critical: about 2-4% of all type checking is spent here
-       */
-      def getParts(tp: Type) {
-        if (seen(tp))
-          return
-        seen += tp
-        tp match {
-          case TypeRef(pre, sym, args) =>
-            if (sym.isClass) {
-              if (!((sym.name == tpnme.REFINE_CLASS_NAME) ||
-                    (sym.name startsWith tpnme.ANON_CLASS_NAME) ||
-                    (sym.name == tpnme.ROOT)))
-                partMap get sym match {
-                  case Some(pre1) =>
-                    if (!(pre =:= pre1)) partMap(sym) = NoType // ambiguous prefix - ignore implicit members
-                  case None =>
-                    if (pre.isStable) partMap(sym) = pre
-                    val bts = tp.baseTypeSeq
-                    var i = 1
-                    while (i < bts.length) {
-                      getParts(bts(i))
-                      i += 1
-                    }
-                    getParts(pre)
-                    args foreach getParts
-                }
-            } else if (sym.isAliasType) {
-              getParts(tp.normalize)
-            } else if (sym.isAbstractType) {
-              getParts(tp.bounds.hi)
-            }
-          case ThisType(_) =>
-            getParts(tp.widen)
-          case _: SingletonType =>
-            getParts(tp.widen)
-          case RefinedType(ps, _) =>
-            for (p <- ps) getParts(p)
-          case AnnotatedType(_, t, _) =>
-            getParts(t)
-          case ExistentialType(_, t) =>
-            getParts(t)
-          case PolyType(_, t) =>
-            getParts(t)
-          case _ =>
-        }
-      }
-
-      getParts(tp)
-
-      val buf = new ListBuffer[Infos]
-      for ((clazz, pre) <- partMap) {
-        if (pre != NoType) {
-          val companion = clazz.companionModule
-          companion.moduleClass match {
-            case mc: ModuleClassSymbol =>
-              buf += (mc.implicitMembers map (im =>
-                new ImplicitInfo(im.name, singleType(pre, companion), im)))
-            case _ =>
-          }
-        }
-      }
-      //println("companion implicits of "+tp+" = "+buf.toList) // DEBUG
-      buf.toList
-    }
-
-*/
-
     /** The implicits made available by type `pt`.
      *  These are all implicits found in companion objects of classes C
      *  such that some part of `tp` has C as one of its superclasses.
@@ -1258,7 +1173,7 @@ trait Implicits {
         implicit def wrapResult(tree: Tree): SearchResult =
           if (tree == EmptyTree) SearchFailure else new SearchResult(tree, if (from.isEmpty) EmptyTreeTypeSubstituter else new TreeTypeSubstituter(from, to))
 
-        val tp1 = tp0.normalize
+        val tp1 = tp0.dealias
         tp1 match {
           case ThisType(_) | SingleType(_, _) =>
             // can't generate a reference to a value that's abstracted over by an existential