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, 25 insertions, 30 deletions

diff --git a/src/compiler/scala/tools/nsc/typechecker/Typers.scala b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
index 9d390476db..38221ad199 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Typers.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
@@ -224,7 +224,7 @@ trait Typers extends Modes with Adaptations with Tags {
       case ExistentialType(tparams, tpe) =>
         new SubstWildcardMap(tparams).apply(tp)
       case TypeRef(_, sym, _) if sym.isAliasType =>
-        val tp0 = tp.normalize
+        val tp0 = tp.dealias
         val tp1 = dropExistential(tp0)
         if (tp1 eq tp0) tp else tp1
       case _ => tp
@@ -439,7 +439,7 @@ trait Typers extends Modes with Adaptations with Tags {
               if (!hiddenSymbols.isEmpty && hiddenSymbols.head == sym &&
                   sym.isAliasType && sameLength(sym.typeParams, args)) {
                 hiddenSymbols = hiddenSymbols.tail
-                t.normalize
+                t.dealias
               } else t
             case SingleType(_, sym) =>
               checkNoEscape(sym)
@@ -1075,9 +1075,9 @@ trait Typers extends Modes with Adaptations with Tags {
           adapt(tree setType restpe, mode, pt, original)
         case TypeRef(_, ByNameParamClass, List(arg)) if ((mode & EXPRmode) != 0) => // (2)
           adapt(tree setType arg, mode, pt, original)
-        case tr @ TypeRef(_, sym, _) if sym.isAliasType && tr.normalize.isInstanceOf[ExistentialType] &&
+        case tr @ TypeRef(_, sym, _) if sym.isAliasType && tr.dealias.isInstanceOf[ExistentialType] &&
           ((mode & (EXPRmode | LHSmode)) == EXPRmode) =>
-          adapt(tree setType tr.normalize.skolemizeExistential(context.owner, tree), mode, pt, original)
+          adapt(tree setType tr.dealias.skolemizeExistential(context.owner, tree), mode, pt, original)
         case et @ ExistentialType(_, _) if ((mode & (EXPRmode | LHSmode)) == EXPRmode) =>
           adapt(tree setType et.skolemizeExistential(context.owner, tree), mode, pt, original)
         case PolyType(tparams, restpe) if inNoModes(mode, TAPPmode | PATTERNmode | HKmode) => // (3)
@@ -1147,7 +1147,7 @@ trait Typers extends Modes with Adaptations with Tags {
               if (tree1.tpe <:< pt) adapt(tree1, mode, pt, original)
               else {
                 if (inExprModeButNot(mode, FUNmode)) {
-                  pt.normalize match {
+                  pt.dealias match {
                     case TypeRef(_, sym, _) =>
                       // note: was if (pt.typeSymbol == UnitClass) but this leads to a potentially
                       // infinite expansion if pt is constant type ()
@@ -1302,7 +1302,7 @@ trait Typers extends Modes with Adaptations with Tags {
 
     def adaptToMember(qual: Tree, searchTemplate: Type, reportAmbiguous: Boolean = true, saveErrors: Boolean = true): Tree = {
       if (isAdaptableWithView(qual)) {
-        qual.tpe.widen.normalize match {
+        qual.tpe.dealiasWiden match {
           case et: ExistentialType =>
             qual setType et.skolemizeExistential(context.owner, qual) // open the existential
           case _ =>
@@ -1840,7 +1840,7 @@ trait Typers extends Modes with Adaptations with Tags {
         _.typedTemplate(cdef.impl, parentTypes(cdef.impl))
       }
       val impl2 = finishMethodSynthesis(impl1, clazz, context)
-      if (clazz.isTrait && clazz.info.parents.nonEmpty && clazz.info.firstParent.normalize.typeSymbol == AnyClass)
+      if (clazz.isTrait && clazz.info.parents.nonEmpty && clazz.info.firstParent.typeSymbol == AnyClass)
         checkEphemeral(clazz, impl2.body)
       if ((clazz != ClassfileAnnotationClass) &&
           (clazz isNonBottomSubClass ClassfileAnnotationClass))
@@ -3865,7 +3865,7 @@ trait Typers extends Modes with Adaptations with Tags {
       val normalizeLocals = new TypeMap {
         def apply(tp: Type): Type = tp match {
           case TypeRef(pre, sym, args) =>
-            if (sym.isAliasType && containsLocal(tp)) apply(tp.normalize)
+            if (sym.isAliasType && containsLocal(tp)) apply(tp.dealias)
             else {
               if (pre.isVolatile)
                 InferTypeWithVolatileTypeSelectionError(tree, pre)
@@ -4393,7 +4393,13 @@ trait Typers extends Modes with Adaptations with Tags {
       def typedNew(tree: New) = {
         val tpt = tree.tpt
         val tpt1 = {
-          val tpt0 = typedTypeConstructor(tpt)
+          // 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.
+          val tpt0 = typedTypeConstructor(tpt) modifyType (_.dealias)
           if (checkStablePrefixClassType(tpt0))
             if (tpt0.hasSymbol && !tpt0.symbol.typeParams.isEmpty) {
               context.undetparams = cloneSymbols(tpt0.symbol.typeParams)
@@ -5733,29 +5739,18 @@ trait Typers extends Modes with Adaptations with Tags {
     def typedTypeConstructor(tree: Tree, mode: Int): Tree = {
       val result = typed(tree, forTypeMode(mode) | FUNmode, WildcardType)
 
-      val restpe = result.tpe.normalize // normalize to get rid of type aliases for the following check (#1241)
-      if (!phase.erasedTypes && restpe.isInstanceOf[TypeRef] && !restpe.prefix.isStable && !context.unit.isJava) {
-        // The isJava exception if OK only because the only type constructors scalac gets
-        // to see are those in the signatures. These do not need a unique object as a prefix.
-        // The situation is different for new's and super's, but scalac does not look deep
-        // enough to see those. See #3938
-        ConstructorPrefixError(tree, restpe)
-      } else {
-        //@M fix for #2208
-        // if there are no type arguments, normalization does not bypass any checks, so perform it to get rid of AnyRef
-        if (result.tpe.typeArgs.isEmpty) {
-          // minimal check: if(result.tpe.typeSymbolDirect eq AnyRefClass) {
-          // must expand the fake AnyRef type alias, because bootstrapping (init in Definitions) is not
-          // designed to deal with the cycles in the scala package (ScalaObject extends
-          // AnyRef, but the AnyRef type alias is entered after the scala package is
-          // loaded and completed, so that ScalaObject is unpickled while AnyRef is not
-          // yet defined )
-          // !!! TODO - revisit now that ScalaObject is gone.
-          result setType(restpe)
-        } else { // must not normalize: type application must be (bounds-)checked (during RefChecks), see #2208
+      // get rid of type aliases for the following check (#1241)
+      result.tpe.dealias match {
+        case restpe @ TypeRef(pre, _, _) if !phase.erasedTypes && !pre.isStable && !context.unit.isJava =>
+          // The isJava exception if OK only because the only type constructors scalac gets
+          // to see are those in the signatures. These do not need a unique object as a prefix.
+          // The situation is different for new's and super's, but scalac does not look deep
+          // enough to see those. See #3938
+          ConstructorPrefixError(tree, restpe)
+        case _ =>
+          // must not normalize: type application must be (bounds-)checked (during RefChecks), see #2208
           // during uncurry (after refchecks), all types are normalized
           result
-        }
       }
     }