Implement the C++0x deduced 'auto' feature.

This fixes PR 8738, 9060 and 9132.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@126069 91177308-0d34-0410-b5e6-96231b3b80d8

26 files changed, 567 insertions, 159 deletions

diff --git a/lib/AST/ASTContext.cpp b/lib/AST/ASTContext.cpp
index 50c295f241..945dfb87f2 100644
--- a/lib/AST/ASTContext.cpp
+++ b/lib/AST/ASTContext.cpp
@@ -380,10 +380,6 @@ void ASTContext::InitBuiltinTypes() {
   // Placeholder type for functions.
   InitBuiltinType(OverloadTy,          BuiltinType::Overload);
 
-  // Placeholder type for C++0x auto declarations whose real type has
-  // not yet been deduced.
-  InitBuiltinType(UndeducedAutoTy,     BuiltinType::UndeducedAuto);
-
   // C99 6.2.5p11.
   FloatComplexTy      = getComplexType(FloatTy);
   DoubleComplexTy     = getComplexType(DoubleTy);
@@ -875,6 +871,12 @@ ASTContext::getTypeInfo(const Type *T) const {
     return getTypeInfo(cast<SubstTemplateTypeParmType>(T)->
                        getReplacementType().getTypePtr());
 
+  case Type::Auto: {
+    const AutoType *A = cast<AutoType>(T);
+    assert(A->isDeduced() && "Cannot request the size of a dependent type");
+    return getTypeInfo(cast<AutoType>(T)->getDeducedType().getTypePtr());
+  }
+
   case Type::Paren:
     return getTypeInfo(cast<ParenType>(T)->getInnerType().getTypePtr());
 
@@ -1532,6 +1534,7 @@ QualType ASTContext::getVariableArrayDecayedType(QualType type) const {
   case Type::DependentTemplateSpecialization:
   case Type::TemplateTypeParm:
   case Type::SubstTemplateTypeParmPack:
+  case Type::Auto:
   case Type::PackExpansion:
     llvm_unreachable("type should never be variably-modified");
 
@@ -2680,6 +2683,14 @@ QualType ASTContext::getDecltypeType(Expr *e) const {
   return QualType(dt, 0);
 }
 
+/// getAutoType - Unlike many "get<Type>" functions, we don't unique
+/// AutoType AST's.
+QualType ASTContext::getAutoType(QualType DeducedType) const {
+  AutoType *at = new (*this, TypeAlignment) AutoType(DeducedType);
+  Types.push_back(at);
+  return QualType(at, 0);
+}
+
 /// getTagDeclType - Return the unique reference to the type for the
 /// specified TagDecl (struct/union/class/enum) decl.
 QualType ASTContext::getTagDeclType(const TagDecl *Decl) const {
diff --git a/lib/AST/ASTDiagnostic.cpp b/lib/AST/ASTDiagnostic.cpp
index 9870b515c6..5bf8a38199 100644
--- a/lib/AST/ASTDiagnostic.cpp
+++ b/lib/AST/ASTDiagnostic.cpp
@@ -28,18 +28,26 @@ static QualType Desugar(ASTContext &Context, QualType QT, bool &ShouldAKA) {
     const Type *Ty = QC.strip(QT);
 
     // Don't aka just because we saw an elaborated type...
-    if (isa<ElaboratedType>(Ty)) {
-      QT = cast<ElaboratedType>(Ty)->desugar();
+    if (const ElaboratedType *ET = dyn_cast<ElaboratedType>(Ty)) {
+      QT = ET->desugar();
       continue;
     }
     // ... or a paren type ...
-    if (isa<ParenType>(Ty)) {
-      QT = cast<ParenType>(Ty)->desugar();
+    if (const ParenType *PT = dyn_cast<ParenType>(Ty)) {
+      QT = PT->desugar();
       continue;
     }
-    // ...or a substituted template type parameter.
-    if (isa<SubstTemplateTypeParmType>(Ty)) {
-      QT = cast<SubstTemplateTypeParmType>(Ty)->desugar();
+    // ...or a substituted template type parameter ...
+    if (const SubstTemplateTypeParmType *ST =
+          dyn_cast<SubstTemplateTypeParmType>(Ty)) {
+      QT = ST->desugar();
+      continue;
+    }
+    // ... or an auto type.
+    if (const AutoType *AT = dyn_cast<AutoType>(Ty)) {
+      if (!AT->isSugared())
+        break;
+      QT = AT->desugar();
       continue;
     }
 
diff --git a/lib/AST/ASTImporter.cpp b/lib/AST/ASTImporter.cpp
index a1e0070422..65c0a3bb61 100644
--- a/lib/AST/ASTImporter.cpp
+++ b/lib/AST/ASTImporter.cpp
@@ -64,6 +64,7 @@ namespace {
     // FIXME: DependentTypeOfExprType
     QualType VisitTypeOfType(const TypeOfType *T);
     QualType VisitDecltypeType(const DecltypeType *T);
+    QualType VisitAutoType(const AutoType *T);
     // FIXME: DependentDecltypeType
     QualType VisitRecordType(const RecordType *T);
     QualType VisitEnumType(const EnumType *T);
@@ -604,6 +605,13 @@ static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
       return false;
     break;
 
+  case Type::Auto:
+    if (!IsStructurallyEquivalent(Context,
+                                  cast<AutoType>(T1)->getDeducedType(),
+                                  cast<AutoType>(T2)->getDeducedType()))
+      return false;
+    break;
+
   case Type::Record:
   case Type::Enum:
     if (!IsStructurallyEquivalent(Context,
@@ -1347,9 +1355,6 @@ QualType ASTNodeImporter::VisitBuiltinType(const BuiltinType *T) {
     
   case BuiltinType::Overload: return Importer.getToContext().OverloadTy;
   case BuiltinType::Dependent: return Importer.getToContext().DependentTy;
-  case BuiltinType::UndeducedAuto: 
-    // FIXME: Make sure that the "to" context supports C++0x!
-    return Importer.getToContext().UndeducedAutoTy;
 
   case BuiltinType::ObjCId:
     // FIXME: Make sure that the "to" context supports Objective-C!
@@ -1550,6 +1555,7 @@ QualType ASTNodeImporter::VisitTypeOfType(const TypeOfType *T) {
 }
 
 QualType ASTNodeImporter::VisitDecltypeType(const DecltypeType *T) {
+  // FIXME: Make sure that the "to" context supports C++0x!
   Expr *ToExpr = Importer.Import(T->getUnderlyingExpr());
   if (!ToExpr)
     return QualType();
@@ -1557,6 +1563,19 @@ QualType ASTNodeImporter::VisitDecltypeType(const DecltypeType *T) {
   return Importer.getToContext().getDecltypeType(ToExpr);
 }
 
+QualType ASTNodeImporter::VisitAutoType(const AutoType *T) {
+  // FIXME: Make sure that the "to" context supports C++0x!
+  QualType FromDeduced = T->getDeducedType();
+  QualType ToDeduced;
+  if (!FromDeduced.isNull()) {
+    ToDeduced = Importer.Import(FromDeduced);
+    if (ToDeduced.isNull())
+      return QualType();
+  }
+  
+  return Importer.getToContext().getAutoType(ToDeduced);
+}
+
 QualType ASTNodeImporter::VisitRecordType(const RecordType *T) {
   RecordDecl *ToDecl
     = dyn_cast_or_null<RecordDecl>(Importer.Import(T->getDecl()));
diff --git a/lib/AST/ItaniumMangle.cpp b/lib/AST/ItaniumMangle.cpp
index 2819a7e4b9..d66c374cbe 100644
--- a/lib/AST/ItaniumMangle.cpp
+++ b/lib/AST/ItaniumMangle.cpp
@@ -1313,9 +1313,6 @@ void CXXNameMangler::mangleType(const BuiltinType *T) {
     assert(false &&
            "Overloaded and dependent types shouldn't get to name mangling");
     break;
-  case BuiltinType::UndeducedAuto:
-    assert(0 && "Should not see undeduced auto here");
-    break;
   case BuiltinType::ObjCId: Out << "11objc_object"; break;
   case BuiltinType::ObjCClass: Out << "10objc_class"; break;
   case BuiltinType::ObjCSel: Out << "13objc_selector"; break;
@@ -1648,6 +1645,12 @@ void CXXNameMangler::mangleType(const DecltypeType *T) {
   Out << 'E';
 }
 
+void CXXNameMangler::mangleType(const AutoType *T) {
+  QualType D = T->getDeducedType();
+  assert(!D.isNull() && "can't mangle undeduced auto type");
+  mangleType(D);
+}
+
 void CXXNameMangler::mangleIntegerLiteral(QualType T,
                                           const llvm::APSInt &Value) {
   //  <expr-primary> ::= L <type> <value number> E # integer literal
diff --git a/lib/AST/MicrosoftMangle.cpp b/lib/AST/MicrosoftMangle.cpp
index 7aafac0ad0..4bf7f23a0a 100644
--- a/lib/AST/MicrosoftMangle.cpp
+++ b/lib/AST/MicrosoftMangle.cpp
@@ -720,9 +720,6 @@ void MicrosoftCXXNameMangler::mangleType(const BuiltinType *T) {
     assert(false &&
            "Overloaded and dependent types shouldn't get to name mangling");
     break;
-  case BuiltinType::UndeducedAuto:
-    assert(0 && "Should not see undeduced auto here");
-    break;
   case BuiltinType::ObjCId: Out << "PAUobjc_object@@"; break;
   case BuiltinType::ObjCClass: Out << "PAUobjc_class@@"; break;
   case BuiltinType::ObjCSel: Out << "PAUobjc_selector@@"; break;
@@ -1119,6 +1116,10 @@ void MicrosoftCXXNameMangler::mangleType(const DecltypeType *T) {
   assert(false && "Don't know how to mangle DecltypeTypes yet!");
 }
 
+void MicrosoftCXXNameMangler::mangleType(const AutoType *T) {
+  assert(false && "Don't know how to mangle AutoTypes yet!");
+}
+
 void MicrosoftMangleContext::mangleName(const NamedDecl *D,
                                         llvm::raw_ostream &Out) {
   assert((isa<FunctionDecl>(D) || isa<VarDecl>(D)) &&
diff --git a/lib/AST/Type.cpp b/lib/AST/Type.cpp
index 0130b13b94..b03314e11d 100644
--- a/lib/AST/Type.cpp
+++ b/lib/AST/Type.cpp
@@ -432,6 +432,61 @@ CXXRecordDecl *Type::getAsCXXRecordDecl() const {
   return 0;
 }
 
+namespace {
+  class GetContainedAutoVisitor :
+    public TypeVisitor<GetContainedAutoVisitor, AutoType*> {
+  public:
+    using TypeVisitor<GetContainedAutoVisitor, AutoType*>::Visit;
+    AutoType *Visit(QualType T) {
+      if (T.isNull())
+        return 0;
+      return Visit(T.getTypePtr());
+    }
+
+    // The 'auto' type itself.
+    AutoType *VisitAutoType(const AutoType *AT) {
+      return const_cast<AutoType*>(AT);
+    }
+
+    // Only these types can contain the desired 'auto' type.
+    AutoType *VisitPointerType(const PointerType *T) {
+      return Visit(T->getPointeeType());
+    }
+    AutoType *VisitBlockPointerType(const BlockPointerType *T) {
+      return Visit(T->getPointeeType());
+    }
+    AutoType *VisitReferenceType(const ReferenceType *T) {
+      return Visit(T->getPointeeTypeAsWritten());
+    }
+    AutoType *VisitMemberPointerType(const MemberPointerType *T) {
+      return Visit(T->getPointeeType());
+    }
+    AutoType *VisitArrayType(const ArrayType *T) {
+      return Visit(T->getElementType());
+    }
+    AutoType *VisitDependentSizedExtVectorType(
+      const DependentSizedExtVectorType *T) {
+      return Visit(T->getElementType());
+    }
+    AutoType *VisitVectorType(const VectorType *T) {
+      return Visit(T->getElementType());
+    }
+    AutoType *VisitFunctionType(const FunctionType *T) {
+      return Visit(T->getResultType());
+    }
+    AutoType *VisitParenType(const ParenType *T) {
+      return Visit(T->getInnerType());
+    }
+    AutoType *VisitAttributedType(const AttributedType *T) {
+      return Visit(T->getModifiedType());
+    }
+  };
+}
+
+AutoType *Type::getContainedAutoType() const {
+  return GetContainedAutoVisitor().Visit(this);
+}
+
 bool Type::isIntegerType() const {
   if (const BuiltinType *BT = dyn_cast<BuiltinType>(CanonicalType))
     return BT->getKind() >= BuiltinType::Bool &&
@@ -1066,7 +1121,6 @@ const char *BuiltinType::getName(const LangOptions &LO) const {
   case NullPtr:           return "nullptr_t";
   case Overload:          return "<overloaded function type>";
   case Dependent:         return "<dependent type>";
-  case UndeducedAuto:     return "auto";
   case ObjCId:            return "id";
   case ObjCClass:         return "Class";
   case ObjCSel:           return "SEL";
diff --git a/lib/AST/TypeLoc.cpp b/lib/AST/TypeLoc.cpp
index 0680acb1c5..14db7f83c2 100644
--- a/lib/AST/TypeLoc.cpp
+++ b/lib/AST/TypeLoc.cpp
@@ -191,9 +191,7 @@ TypeSpecifierType BuiltinTypeLoc::getWrittenTypeSpec() const {
     case BuiltinType::WChar_S:
     case BuiltinType::WChar_U:
       return TST_wchar;
-    case BuiltinType::UndeducedAuto:
-      return TST_auto;
-        
+
     case BuiltinType::UChar:
     case BuiltinType::UShort:
     case BuiltinType::UInt:
diff --git a/lib/AST/TypePrinter.cpp b/lib/AST/TypePrinter.cpp
index 5e6046acdc..139073987a 100644
--- a/lib/AST/TypePrinter.cpp
+++ b/lib/AST/TypePrinter.cpp
@@ -80,6 +80,8 @@ void TypePrinter::print(const Type *T, Qualifiers Quals, std::string &buffer) {
   bool CanPrefixQualifiers = false;
   
   Type::TypeClass TC = T->getTypeClass();
+  if (const AutoType *AT = dyn_cast<AutoType>(T))
+    TC = AT->desugar()->getTypeClass();
   if (const SubstTemplateTypeParmType *Subst
                                       = dyn_cast<SubstTemplateTypeParmType>(T))
     TC = Subst->getReplacementType()->getTypeClass();
@@ -129,6 +131,7 @@ void TypePrinter::print(const Type *T, Qualifiers Quals, std::string &buffer) {
     case Type::Attributed:
     case Type::PackExpansion:
     case Type::SubstTemplateTypeParm:
+    case Type::Auto:
       CanPrefixQualifiers = false;
       break;
   }
@@ -493,6 +496,17 @@ void TypePrinter::printDecltype(const DecltypeType *T, std::string &S) {
   S = "decltype(" + s.str() + ")" + S;
 }
 
+void TypePrinter::printAuto(const AutoType *T, std::string &S) { 
+  // If the type has been deduced, do not print 'auto'.
+  if (T->isDeduced()) {
+    print(T->getDeducedType(), S);
+  } else {
+    if (!S.empty())    // Prefix the basic type, e.g. 'auto X'.
+      S = ' ' + S;
+    S = "auto" + S;
+  }
+}
+
 /// Appends the given scope to the end of a string.
 void TypePrinter::AppendScope(DeclContext *DC, std::string &Buffer) {
   if (DC->isTranslationUnit()) return;
diff --git a/lib/CodeGen/CGDebugInfo.cpp b/lib/CodeGen/CGDebugInfo.cpp
index 01a4154a87..469b4605d7 100644
--- a/lib/CodeGen/CGDebugInfo.cpp
+++ b/lib/CodeGen/CGDebugInfo.cpp
@@ -1465,6 +1465,7 @@ llvm::DIType CGDebugInfo::CreateTypeNode(QualType Ty,
   case Type::TypeOfExpr:
   case Type::TypeOf:
   case Type::Decltype:
+  case Type::Auto:
     llvm_unreachable("type should have been unwrapped!");
     return llvm::DIType();      
   }
diff --git a/lib/CodeGen/CGRTTI.cpp b/lib/CodeGen/CGRTTI.cpp
index de403b6559..7ec0ee4b5c 100644
--- a/lib/CodeGen/CGRTTI.cpp
+++ b/lib/CodeGen/CGRTTI.cpp
@@ -195,7 +195,6 @@ static bool TypeInfoIsInStandardLibrary(const BuiltinType *Ty) {
       
     case BuiltinType::Overload:
     case BuiltinType::Dependent:
-    case BuiltinType::UndeducedAuto:
       assert(false && "Should not see this type here!");
       
     case BuiltinType::ObjCId:
diff --git a/lib/CodeGen/CodeGenTypes.cpp b/lib/CodeGen/CodeGenTypes.cpp
index 0a1f76d297..5254922f13 100644
--- a/lib/CodeGen/CodeGenTypes.cpp
+++ b/lib/CodeGen/CodeGenTypes.cpp
@@ -253,7 +253,6 @@ const llvm::Type *CodeGenTypes::ConvertNewType(QualType T) {
     
     case BuiltinType::Overload:
     case BuiltinType::Dependent:
-    case BuiltinType::UndeducedAuto:
       assert(0 && "Unexpected builtin type!");
       break;
     }
diff --git a/lib/Parse/ParseDecl.cpp b/lib/Parse/ParseDecl.cpp
index bff4e184c2..5a7fc7e72d 100644
--- a/lib/Parse/ParseDecl.cpp
+++ b/lib/Parse/ParseDecl.cpp
@@ -392,7 +392,7 @@ Parser::DeclGroupPtrTy Parser::ParseSimpleDeclaration(StmtVector &Stmts,
   ParsingDeclSpec DS(*this);
   DS.takeAttributesFrom(attrs);
   ParseDeclarationSpecifiers(DS, ParsedTemplateInfo(), AS_none,
-                            getDeclSpecContextFromDeclaratorContext(Context));
+                             getDeclSpecContextFromDeclaratorContext(Context));
   StmtResult R = Actions.ActOnVlaStmt(DS);
   if (R.isUsable())
     Stmts.push_back(R.release());
@@ -587,6 +587,9 @@ Decl *Parser::ParseDeclarationAfterDeclarator(Declarator &D,
     }
   }
 
+  bool TypeContainsAuto =
+    D.getDeclSpec().getTypeSpecType() == DeclSpec::TST_auto;
+
   // Parse declarator '=' initializer.
   if (isTokenEqualOrMistypedEqualEqual(
                                diag::err_invalid_equalequal_after_declarator)) {
@@ -622,7 +625,8 @@ Decl *Parser::ParseDeclarationAfterDeclarator(Declarator &D,
         SkipUntil(tok::comma, true, true);
         Actions.ActOnInitializerError(ThisDecl);
       } else
-        Actions.AddInitializerToDecl(ThisDecl, Init.take());
+        Actions.AddInitializerToDecl(ThisDecl, Init.take(),
+                                     /*DirectInit=*/false, TypeContainsAuto);
     }
   } else if (Tok.is(tok::l_paren)) {
     // Parse C++ direct initializer: '(' expression-list ')'
@@ -656,12 +660,11 @@ Decl *Parser::ParseDeclarationAfterDeclarator(Declarator &D,
 
       Actions.AddCXXDirectInitializerToDecl(ThisDecl, LParenLoc,
                                             move_arg(Exprs),
-                                            RParenLoc);
+                                            RParenLoc,
+                                            TypeContainsAuto);
     }
   } else {
-    bool TypeContainsUndeducedAuto =
-      D.getDeclSpec().getTypeSpecType() == DeclSpec::TST_auto;
-    Actions.ActOnUninitializedDecl(ThisDecl, TypeContainsUndeducedAuto);
+    Actions.ActOnUninitializedDecl(ThisDecl, TypeContainsAuto);
   }
 
   return ThisDecl;
diff --git a/lib/Parse/ParseExprCXX.cpp b/lib/Parse/ParseExprCXX.cpp
index e769ecac50..e73578f23e 100644
--- a/lib/Parse/ParseExprCXX.cpp
+++ b/lib/Parse/ParseExprCXX.cpp
@@ -827,7 +827,8 @@ bool Parser::ParseCXXCondition(ExprResult &ExprOut,
     ConsumeToken();
     ExprResult AssignExpr(ParseAssignmentExpression());
     if (!AssignExpr.isInvalid()) 
-      Actions.AddInitializerToDecl(DeclOut, AssignExpr.take());
+      Actions.AddInitializerToDecl(DeclOut, AssignExpr.take(), false,
+                                   DS.getTypeSpecType() == DeclSpec::TST_auto);
   } else {
     // FIXME: C++0x allows a braced-init-list
     Diag(Tok, diag::err_expected_equal_after_declarator);
diff --git a/lib/Sema/SemaCodeComplete.cpp b/lib/Sema/SemaCodeComplete.cpp
index aef5cab98a..bab665a38d 100644
--- a/lib/Sema/SemaCodeComplete.cpp
+++ b/lib/Sema/SemaCodeComplete.cpp
@@ -586,7 +586,6 @@ SimplifiedTypeClass clang::getSimplifiedTypeClass(CanQualType T) {
         
       case BuiltinType::Overload:
       case BuiltinType::Dependent:
-      case BuiltinType::UndeducedAuto:
         return STC_Other;
         
       case BuiltinType::ObjCId:
diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index 679b430a3c..dd30c1261e 100644
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -1471,48 +1471,26 @@ bool Sema::MergeCompatibleFunctionDecls(FunctionDecl *New, FunctionDecl *Old) {
   return false;
 }
 
-/// MergeVarDecl - We just parsed a variable 'New' which has the same name
-/// and scope as a previous declaration 'Old'.  Figure out how to resolve this
-/// situation, merging decls or emitting diagnostics as appropriate.
+/// MergeVarDecl - We parsed a variable 'New' which has the same name and scope
+/// as a previous declaration 'Old'.  Figure out how to merge their types,
+/// emitting diagnostics as appropriate.
 ///
-/// Tentative definition rules (C99 6.9.2p2) are checked by
-/// FinalizeDeclaratorGroup. Unfortunately, we can't analyze tentative
-/// definitions here, since the initializer hasn't been attached.
+/// Declarations using the auto type specifier (C++ [decl.spec.auto]) call back
+/// to here in AddInitializerToDecl and AddCXXDirectInitializerToDecl. We can't
+/// check them before the initializer is attached.
 ///
-void Sema::MergeVarDecl(VarDecl *New, LookupResult &Previous) {
-  // If the new decl is already invalid, don't do any other checking.
-  if (New->isInvalidDecl())
+void Sema::MergeVarDeclTypes(VarDecl *New, VarDecl *Old) {
+  if (New->isInvalidDecl() || Old->isInvalidDecl())
     return;
 
-  // Verify the old decl was also a variable.
-  VarDecl *Old = 0;
-  if (!Previous.isSingleResult() ||
-      !(Old = dyn_cast<VarDecl>(Previous.getFoundDecl()))) {
-    Diag(New->getLocation(), diag::err_redefinition_different_kind)
-      << New->getDeclName();
-    Diag(Previous.getRepresentativeDecl()->getLocation(),
-         diag::note_previous_definition);
-    return New->setInvalidDecl();
-  }
-
-  // C++ [class.mem]p1:
-  //   A member shall not be declared twice in the member-specification [...]
-  // 
-  // Here, we need only consider static data members.
-  if (Old->isStaticDataMember() && !New->isOutOfLine()) {
-    Diag(New->getLocation(), diag::err_duplicate_member) 
-      << New->getIdentifier();
-    Diag(Old->getLocation(), diag::note_previous_declaration);
-    New->setInvalidDecl();
-  }
-  
-  MergeDeclAttributes(New, Old, Context);
-
-  // Merge the types
   QualType MergedT;
   if (getLangOptions().CPlusPlus) {
-    if (Context.hasSameType(New->getType(), Old->getType()))
-      MergedT = New->getType();
+    AutoType *AT = New->getType()->getContainedAutoType();
+    if (AT && !AT->isDeduced()) {
+      // We don't know what the new type is until the initializer is attached.
+      return;
+    } else if (Context.hasSameType(New->getType(), Old->getType()))
+      return;
     // C++ [basic.link]p10:
     //   [...] the types specified by all declarations referring to a given
     //   object or function shall be identical, except that declarations for an
@@ -1536,7 +1514,8 @@ void Sema::MergeVarDecl(VarDecl *New, LookupResult &Previous) {
         MergedT = Old->getType();
     } else if (New->getType()->isObjCObjectPointerType()
                && Old->getType()->isObjCObjectPointerType()) {
-        MergedT = Context.mergeObjCGCQualifiers(New->getType(), Old->getType());
+        MergedT = Context.mergeObjCGCQualifiers(New->getType(),
+                                                        Old->getType());
     }
   } else {
     MergedT = Context.mergeTypes(New->getType(), Old->getType());
@@ -1548,6 +1527,49 @@ void Sema::MergeVarDecl(VarDecl *New, LookupResult &Previous) {
     return New->setInvalidDecl();
   }
   New->setType(MergedT);
+}
+
+/// MergeVarDecl - We just parsed a variable 'New' which has the same name
+/// and scope as a previous declaration 'Old'.  Figure out how to resolve this
+/// situation, merging decls or emitting diagnostics as appropriate.
+///
+/// Tentative definition rules (C99 6.9.2p2) are checked by
+/// FinalizeDeclaratorGroup. Unfortunately, we can't analyze tentative
+/// definitions here, since the initializer hasn't been attached.
+///
+void Sema::MergeVarDecl(VarDecl *New, LookupResult &Previous) {
+  // If the new decl is already invalid, don't do any other checking.
+  if (New->isInvalidDecl())
+    return;
+
+  // Verify the old decl was also a variable.
+  VarDecl *Old = 0;
+  if (!Previous.isSingleResult() ||
+      !(Old = dyn_cast<VarDecl>(Previous.getFoundDecl()))) {
+    Diag(New->getLocation(), diag::err_redefinition_different_kind)
+      << New->getDeclName();
+    Diag(Previous.getRepresentativeDecl()->getLocation(),
+         diag::note_previous_definition);
+    return New->setInvalidDecl();
+  }
+
+  // C++ [class.mem]p1:
+  //   A member shall not be declared twice in the member-specification [...]
+  // 
+  // Here, we need only consider static data members.
+  if (Old->isStaticDataMember() && !New->isOutOfLine()) {
+    Diag(New->getLocation(), diag::err_duplicate_member) 
+      << New->getIdentifier();
+    Diag(Old->getLocation(), diag::note_previous_declaration);
+    New->setInvalidDecl();
+  }
+  
+  MergeDeclAttributes(New, Old, Context);
+
+  // Merge the types.
+  MergeVarDeclTypes(New, Old);
+  if (New->isInvalidDecl())
+    return;
 
   // C99 6.2.2p4: Check if we have a static decl followed by a non-static.
   if (New->getStorageClass() == SC_Static &&
@@ -3004,6 +3026,12 @@ Sema::ActOnVariableDeclarator(Scope *S, Declarator &D, DeclContext *DC,
     NewVD = VarDecl::Create(Context, DC, D.getIdentifierLoc(),
                             II, R, TInfo, SC, SCAsWritten);
 
+    // If this decl has an auto type in need of deduction, mark the VarDecl so
+    // we can diagnose uses of it in its own initializer.
+    if (D.getDeclSpec().getTypeSpecType() == DeclSpec::TST_auto) {
+      NewVD->setParsingAutoInit(R->getContainedAutoType());
+    }
+
     if (D.isInvalidType() || Invalid)
       NewVD->setInvalidDecl();
 
@@ -4466,17 +4494,14 @@ bool Sema::CheckForConstantInitializer(Expr *Init, QualType DclT) {
   return true;
 }
 
-void Sema::AddInitializerToDecl(Decl *dcl, Expr *init) {
-  AddInitializerToDecl(dcl, init, /*DirectInit=*/false);
-}
-
 /// AddInitializerToDecl - Adds the initializer Init to the
 /// declaration dcl. If DirectInit is true, this is C++ direct
 /// initialization rather than copy initialization.
-void Sema::AddInitializerToDecl(Decl *RealDecl, Expr *Init, bool DirectInit) {
+void Sema::AddInitializerToDecl(Decl *RealDecl, Expr *Init,
+                                bool DirectInit, bool TypeMayContainAuto) {
   // If there is no declaration, there was an error parsing it.  Just ignore
   // the initializer.
-  if (RealDecl == 0)
+  if (RealDecl == 0 || RealDecl->isInvalidDecl())
     return;
 
   if (CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(RealDecl)) {
@@ -4507,6 +4532,25 @@ void Sema::AddInitializerToDecl(Decl *RealDecl, Expr *Init, bool DirectInit) {
     return;
   }
 
+  // C++0x [decl.spec.auto]p6. Deduce the type which 'auto' stands in for.
+  if (TypeMayContainAuto && VDecl->getType()->getContainedAutoType()) {
+    VDecl->setParsingAutoInit(false);
+
+    QualType DeducedType;
+    if (!DeduceAutoType(VDecl->getType(), Init, DeducedType)) {
+      Diag(VDecl->getLocation(), diag::err_auto_var_deduction_failure)
+        << VDecl->getDeclName() << VDecl->getType() << Init->getType()
+        << Init->getSourceRange();
+      RealDecl->setInvalidDecl();
+      return;
+    }
+    VDecl->setType(DeducedType);
+
+    // If this is a redeclaration, check that the type we just deduced matches
+    // the previously declared type.
+    if (VarDecl *Old = VDecl->getPreviousDeclaration())
+      MergeVarDeclTypes(VDecl, Old);
+  }
   
 
   // A definition must end up with a complete type, which means it must be
@@ -4755,6 +4799,13 @@ void Sema::ActOnInitializerError(Decl *D) {
   VarDecl *VD = dyn_cast<VarDecl>(D);
   if (!VD) return;
 
+  // Auto types are meaningless if we can't make sense of the initializer.
+  if (VD->isParsingAutoInit()) {
+    VD->setParsingAutoInit(false);
+    VD->setInvalidDecl();
+    return;
+  }
+
   QualType Ty = VD->getType();
   if (Ty->isDependentType()) return;
 
@@ -4779,7 +4830,7 @@ void Sema::ActOnInitializerError(Decl *D) {
 }
 
 void Sema::ActOnUninitializedDecl(Decl *RealDecl,
-                                  bool TypeContainsUndeducedAuto) {
+                                  bool TypeMayContainAuto) {
   // If there is no declaration, there was an error parsing it. Just ignore it.
   if (RealDecl == 0)
     return;
@@ -4788,7 +4839,9 @@ void Sema::ActOnUninitializedDecl(Decl *RealDecl,
     QualType Type = Var->getType();
 
     // C++0x [dcl.spec.auto]p3
-    if (TypeContainsUndeducedAuto) {
+    if (TypeMayContainAuto && Type->getContainedAutoType()) {
+      Var->setParsingAutoInit(false);
+
       Diag(Var->getLocation(), diag::err_auto_var_requires_init)
         << Var->getDeclName() << Type;
       Var->setInvalidDecl();
@@ -4999,6 +5052,41 @@ Sema::FinalizeDeclaratorGroup(Scope *S, const DeclSpec &DS,
   if (DS.isTypeSpecOwned())
     Decls.push_back(DS.getRepAsDecl());
 
+  // C++0x [dcl.spec.auto]p7:
+  //   If the type deduced for the template parameter U is not the same in each
+  //   deduction, the program is ill-formed.
+  // FIXME: When initializer-list support is added, a distinction is needed
+  // between the deduced type U and the deduced type which 'auto' stands for.
+  //   auto a = 0, b = { 1, 2, 3 };
+  // is legal because the deduced type U is 'int' in both cases.
+  bool TypeContainsAuto = DS.getTypeSpecType() == DeclSpec::TST_auto;
+  if (TypeContainsAuto && NumDecls > 1) {
+    QualType Deduced;
+    CanQualType DeducedCanon;
+    VarDecl *DeducedDecl = 0;
+    for (unsigned i = 0; i != NumDecls; ++i) {
+      if (VarDecl *D = dyn_cast<VarDecl>(Group[i])) {
+        AutoType *AT = D->getType()->getContainedAutoType();
+        if (AT && AT->isDeduced()) {
+          QualType U = AT->getDeducedType();
+          CanQualType UCanon = Context.getCanonicalType(U);
+          if (Deduced.isNull()) {
+            Deduced = U;
+            DeducedCanon = UCanon;
+            DeducedDecl = D;
+          } else if (DeducedCanon != UCanon) {
+            Diag(DS.getTypeSpecTypeLoc(), diag::err_auto_different_deductions)
+              << Deduced << DeducedDecl->getDeclName()
+              << U << D->getDeclName()
+              << DeducedDecl->getInit()->getSourceRange()
+              << D->getInit()->getSourceRange();
+            break;
+          }
+        }
+      }
+    }
+  }
+
   for (unsigned i = 0; i != NumDecls; ++i)
     if (Decl *D = Group[i])
       Decls.push_back(D);
diff --git a/lib/Sema/SemaDeclCXX.cpp b/lib/Sema/SemaDeclCXX.cpp
index 2e6c4c8ace..e8abab8476 100644
--- a/lib/Sema/SemaDeclCXX.cpp
+++ b/