Add support for GCC's '__auto_type' extension, per the GCC manual:

https://gcc.gnu.org/onlinedocs/gcc/Typeof.html

Differences from the GCC extension:
 * __auto_type is also permitted in C++ (but only in places where
   it could appear in C), allowing its use in headers that might
   be shared across C and C++, or used from C++98
 * __auto_type can be combined with a declarator, as with C++ auto
   (for instance, "__auto_type *p")
 * multiple variables can be declared in a single __auto_type
   declaration, with the C++ semantics (the deduced type must be
   the same in each case)

This patch also adds a missing restriction on applying typeof to
a bit-field, which GCC has historically rejected in C (due to
lack of clarity as to whether the operand should be promoted).
The same restriction also applies to __auto_type in C (in both
GCC and Clang).

This also fixes PR25449.

Patch by Nicholas Allegra!

llvm-svn: 252690

33 files changed, 192 insertions, 93 deletions

diff --git a/clang/include/clang/AST/ASTContext.h b/clang/include/clang/AST/ASTContext.h
index 72bbb606df0..a6d97aaec2e 100644
--- a/clang/include/clang/AST/ASTContext.h
+++ b/clang/include/clang/AST/ASTContext.h
@@ -1299,7 +1299,7 @@ public:
                                  UnaryTransformType::UTTKind UKind) const;
 
   /// \brief C++11 deduced auto type.
-  QualType getAutoType(QualType DeducedType, bool IsDecltypeAuto,
+  QualType getAutoType(QualType DeducedType, AutoTypeKeyword Keyword,
                        bool IsDependent) const;
 
   /// \brief C++11 deduction pattern for 'auto' type.
diff --git a/clang/include/clang/AST/Type.h b/clang/include/clang/AST/Type.h
index d080535ba7e..e9aadec8020 100644
--- a/clang/include/clang/AST/Type.h
+++ b/clang/include/clang/AST/Type.h
@@ -1210,6 +1210,16 @@ enum RefQualifierKind {
   RQ_RValue
 };
 
+/// Which keyword(s) were used to create an AutoType.
+enum class AutoTypeKeyword {
+  /// \brief auto
+  Auto,
+  /// \brief decltype(auto)
+  DecltypeAuto,
+  /// \brief __auto_type (GNU extension)
+  GNUAutoType
+};
+
 /// The base class of the type hierarchy.
 ///
 /// A central concept with types is that each type always has a canonical
@@ -1428,8 +1438,9 @@ protected:
 
     unsigned : NumTypeBits;
 
-    /// Was this placeholder type spelled as 'decltype(auto)'?
-    unsigned IsDecltypeAuto : 1;
+    /// Was this placeholder type spelled as 'auto', 'decltype(auto)',
+    /// or '__auto_type'?  AutoTypeKeyword value.
+    unsigned Keyword : 2;
   };
 
   union {
@@ -3902,8 +3913,7 @@ public:
 /// is no deduced type and an auto type is canonical. In the latter case, it is
 /// also a dependent type.
 class AutoType : public Type, public llvm::FoldingSetNode {
-  AutoType(QualType DeducedType, bool IsDecltypeAuto,
-           bool IsDependent)
+  AutoType(QualType DeducedType, AutoTypeKeyword Keyword, bool IsDependent)
     : Type(Auto, DeducedType.isNull() ? QualType(this, 0) : DeducedType,
            /*Dependent=*/IsDependent, /*InstantiationDependent=*/IsDependent,
            /*VariablyModified=*/false,
@@ -3911,13 +3921,18 @@ class AutoType : public Type, public llvm::FoldingSetNode {
                ? false : DeducedType->containsUnexpandedParameterPack()) {
     assert((DeducedType.isNull() || !IsDependent) &&
            "auto deduced to dependent type");
-    AutoTypeBits.IsDecltypeAuto = IsDecltypeAuto;
+    AutoTypeBits.Keyword = (unsigned)Keyword;
   }
 
   friend class ASTContext;  // ASTContext creates these
 
 public:
-  bool isDecltypeAuto() const { return AutoTypeBits.IsDecltypeAuto; }
+  bool isDecltypeAuto() const {
+    return getKeyword() == AutoTypeKeyword::DecltypeAuto;
+  }
+  AutoTypeKeyword getKeyword() const {
+    return (AutoTypeKeyword)AutoTypeBits.Keyword;
+  }
 
   bool isSugared() const { return !isCanonicalUnqualified(); }
   QualType desugar() const { return getCanonicalTypeInternal(); }
@@ -3932,14 +3947,13 @@ public:
   }
 
   void Profile(llvm::FoldingSetNodeID &ID) {
-    Profile(ID, getDeducedType(), isDecltypeAuto(), 
-		    isDependentType());
+    Profile(ID, getDeducedType(), getKeyword(), isDependentType());
   }
 
   static void Profile(llvm::FoldingSetNodeID &ID, QualType Deduced,
-                      bool IsDecltypeAuto, bool IsDependent) {
+                      AutoTypeKeyword Keyword, bool IsDependent) {
     ID.AddPointer(Deduced.getAsOpaquePtr());
-    ID.AddBoolean(IsDecltypeAuto);
+    ID.AddInteger((unsigned)Keyword);
     ID.AddBoolean(IsDependent);
   }
 
diff --git a/clang/include/clang/Basic/DiagnosticGroups.td b/clang/include/clang/Basic/DiagnosticGroups.td
index 4b94b186cd6..0b030168aaa 100644
--- a/clang/include/clang/Basic/DiagnosticGroups.td
+++ b/clang/include/clang/Basic/DiagnosticGroups.td
@@ -24,6 +24,7 @@ def : DiagGroup<"aggregate-return">;
 def GNUAlignofExpression : DiagGroup<"gnu-alignof-expression">;
 def AmbigMemberTemplate : DiagGroup<"ambiguous-member-template">;
 def GNUAnonymousStruct : DiagGroup<"gnu-anonymous-struct">;
+def GNUAutoType : DiagGroup<"gnu-auto-type">;
 def ArrayBounds : DiagGroup<"array-bounds">;
 def ArrayBoundsPointerArithmetic : DiagGroup<"array-bounds-pointer-arithmetic">;
 def Availability : DiagGroup<"availability">;
@@ -707,6 +708,7 @@ def C99 : DiagGroup<"c99-extensions">;
 
 // A warning group for warnings about GCC extensions.
 def GNU : DiagGroup<"gnu", [GNUAlignofExpression, GNUAnonymousStruct,
+                            GNUAutoType,
                             GNUBinaryLiteral, GNUCaseRange,
                             GNUComplexInteger, GNUCompoundLiteralInitializer,
                             GNUConditionalOmittedOperand, GNUDesignator,
diff --git a/clang/include/clang/Basic/DiagnosticParseKinds.td b/clang/include/clang/Basic/DiagnosticParseKinds.td
index bf0a128a70d..6e7fbde587c 100644
--- a/clang/include/clang/Basic/DiagnosticParseKinds.td
+++ b/clang/include/clang/Basic/DiagnosticParseKinds.td
@@ -299,6 +299,9 @@ def ext_decltype_auto_type_specifier : ExtWarn<
 def warn_cxx11_compat_decltype_auto_type_specifier : Warning<
   "'decltype(auto)' type specifier is incompatible with C++ standards before "
   "C++14">, InGroup<CXXPre14Compat>, DefaultIgnore;
+def ext_auto_type : Extension<
+  "'__auto_type' is a GNU extension">,
+  InGroup<GNUAutoType>;
 def ext_for_range : ExtWarn<
   "range-based for loop is a C++11 extension">, InGroup<CXX11>;
 def warn_cxx98_compat_for_range : Warning<
diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index 9b21c61dce3..43062543057 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -1664,18 +1664,22 @@ def warn_cxx98_compat_auto_type_specifier : Warning<
   "'auto' type specifier is incompatible with C++98">,
   InGroup<CXX98Compat>, DefaultIgnore;
 def err_auto_variable_cannot_appear_in_own_initializer : Error<
-  "variable %0 declared with 'auto' type cannot appear in its own initializer">;
+  "variable %0 declared with %select{'auto'|'decltype(auto)'|'__auto_type'}1 "
+  "type cannot appear in its own initializer">;
 def err_illegal_decl_array_of_auto : Error<
   "'%0' declared as array of %1">;
 def err_new_array_of_auto : Error<
   "cannot allocate array of 'auto'">;
 def err_auto_not_allowed : Error<
-  "%select{'auto'|'decltype(auto)'}0 not allowed %select{in function prototype"
-  "|in non-static struct member"
-  "|in non-static union member|in non-static class member|in interface member"
+  "%select{'auto'|'decltype(auto)'|'__auto_type'}0 not allowed "
+  "%select{in function prototype"
+  "|in non-static struct member|in struct member"
+  "|in non-static union member|in union member"
+  "|in non-static class member|in interface member"
   "|in exception declaration|in template parameter|in block literal"
   "|in template argument|in typedef|in type alias|in function return type"
-  "|in conversion function type|here|in lambda parameter}1">;
+  "|in conversion function type|here|in lambda parameter"
+  "|in type allocated by 'new'|in K&R-style function parameter}1">;
 def err_auto_not_allowed_var_inst : Error<
   "'auto' variable template instantiation is not allowed">;
 def err_auto_var_requires_init : Error<
@@ -1709,8 +1713,8 @@ def err_auto_var_deduction_failure_from_init_list : Error<
 def err_auto_new_deduction_failure : Error<
   "new expression for type %0 has incompatible constructor argument of type %1">;
 def err_auto_different_deductions : Error<
-  "'%select{auto|decltype(auto)}0' deduced as %1 in declaration of %2 and "
-  "deduced as %3 in declaration of %4">;
+  "'%select{auto|decltype(auto)|__auto_type}0' deduced as %1 in declaration "
+  "of %2 and deduced as %3 in declaration of %4">;
 def err_implied_std_initializer_list_not_found : Error<
   "cannot deduce type of initializer list because std::initializer_list was "
   "not found; include <initializer_list>">;
@@ -1720,6 +1724,10 @@ def warn_dangling_std_initializer_list : Warning<
   "array backing the initializer list will be destroyed at the end of "
   "%select{the full-expression|the constructor}0">,
   InGroup<DiagGroup<"dangling-initializer-list">>;
+def err_auto_init_list_from_c : Error<
+  "cannot use __auto_type with initializer list in C">;
+def err_auto_bitfield : Error<
+  "cannot pass bit-field as __auto_type initializer in C">;
 
 // C++1y decltype(auto) type
 def err_decltype_auto_cannot_be_combined : Error<
@@ -4812,8 +4820,8 @@ def err_sizeof_alignof_function_type : Error<
   "function type">;
 def err_openmp_default_simd_align_expr : Error<
   "invalid application of '__builtin_omp_required_simd_align' to an expression, only type is allowed">;
-def err_sizeof_alignof_bitfield : Error<
-  "invalid application of '%select{sizeof|alignof}0' to bit-field">;
+def err_sizeof_alignof_typeof_bitfield : Error<
+  "invalid application of '%select{sizeof|alignof|typeof}0' to bit-field">;
 def err_alignof_member_of_incomplete_type : Error<
   "invalid application of 'alignof' to a field of a class still being defined">;
 def err_vecstep_non_scalar_vector_type : Error<
diff --git a/clang/include/clang/Basic/Specifiers.h b/clang/include/clang/Basic/Specifiers.h
index 47d2f31c0fe..e5f1f834f75 100644
--- a/clang/include/clang/Basic/Specifiers.h
+++ b/clang/include/clang/Basic/Specifiers.h
@@ -64,6 +64,7 @@ namespace clang {
     TST_underlyingType,   // __underlying_type for C++11
     TST_auto,             // C++11 auto
     TST_decltype_auto,    // C++1y decltype(auto)
+    TST_auto_type,        // __auto_type extension
     TST_unknown_anytype,  // __unknown_anytype extension
     TST_atomic,           // C11 _Atomic
     TST_error         // erroneous type
diff --git a/clang/include/clang/Basic/TokenKinds.def b/clang/include/clang/Basic/TokenKinds.def
index 1e0ec117d07..9252d9947a9 100644
--- a/clang/include/clang/Basic/TokenKinds.def
+++ b/clang/include/clang/Basic/TokenKinds.def
@@ -384,6 +384,7 @@ KEYWORD(__real                      , KEYALL)
 KEYWORD(__thread                    , KEYALL)
 KEYWORD(__FUNCTION__                , KEYALL)
 KEYWORD(__PRETTY_FUNCTION__         , KEYALL)
+KEYWORD(__auto_type                 , KEYALL)
 
 // GNU Extensions (outside impl-reserved namespace)
 KEYWORD(typeof                      , KEYGNU)
diff --git a/clang/include/clang/Sema/DeclSpec.h b/clang/include/clang/Sema/DeclSpec.h
index f809c58e056..7bce0cdcfcc 100644
--- a/clang/include/clang/Sema/DeclSpec.h
+++ b/clang/include/clang/Sema/DeclSpec.h
@@ -301,6 +301,7 @@ public:
   static const TST TST_decltype_auto = clang::TST_decltype_auto;
   static const TST TST_underlyingType = clang::TST_underlyingType;
   static const TST TST_auto = clang::TST_auto;
+  static const TST TST_auto_type = clang::TST_auto_type;
   static const TST TST_unknown_anytype = clang::TST_unknown_anytype;
   static const TST TST_atomic = clang::TST_atomic;
   static const TST TST_error = clang::TST_error;
@@ -512,7 +513,8 @@ public:
   void setTypeofParensRange(SourceRange range) { TypeofParensRange = range; }
 
   bool containsPlaceholderType() const {
-    return TypeSpecType == TST_auto || TypeSpecType == TST_decltype_auto;
+    return (TypeSpecType == TST_auto || TypeSpecType == TST_auto_type ||
+            TypeSpecType == TST_decltype_auto);
   }
 
   bool hasTagDefinition() const;
diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
index 4009915619d..18240e79d80 100644
--- a/clang/lib/AST/ASTContext.cpp
+++ b/clang/lib/AST/ASTContext.cpp
@@ -3983,20 +3983,20 @@ QualType ASTContext::getUnaryTransformType(QualType BaseType,
 /// getAutoType - Return the uniqued reference to the 'auto' type which has been
 /// deduced to the given type, or to the canonical undeduced 'auto' type, or the
 /// canonical deduced-but-dependent 'auto' type.
-QualType ASTContext::getAutoType(QualType DeducedType, bool IsDecltypeAuto,
+QualType ASTContext::getAutoType(QualType DeducedType, AutoTypeKeyword Keyword,
                                  bool IsDependent) const {
-  if (DeducedType.isNull() && !IsDecltypeAuto && !IsDependent)
+  if (DeducedType.isNull() && Keyword == AutoTypeKeyword::Auto && !IsDependent)
     return getAutoDeductType();
 
   // Look in the folding set for an existing type.
   void *InsertPos = nullptr;
   llvm::FoldingSetNodeID ID;
-  AutoType::Profile(ID, DeducedType, IsDecltypeAuto, IsDependent);
+  AutoType::Profile(ID, DeducedType, Keyword, IsDependent);
   if (AutoType *AT = AutoTypes.FindNodeOrInsertPos(ID, InsertPos))
     return QualType(AT, 0);
 
   AutoType *AT = new (*this, TypeAlignment) AutoType(DeducedType,
-                                                     IsDecltypeAuto,
+                                                     Keyword,
                                                      IsDependent);
   Types.push_back(AT);
   if (InsertPos)
@@ -4036,7 +4036,7 @@ QualType ASTContext::getAtomicType(QualType T) const {
 QualType ASTContext::getAutoDeductType() const {
   if (AutoDeductTy.isNull())
     AutoDeductTy = QualType(
-      new (*this, TypeAlignment) AutoType(QualType(), /*decltype(auto)*/false,
+      new (*this, TypeAlignment) AutoType(QualType(), AutoTypeKeyword::Auto,
                                           /*dependent*/false),
       0);
   return AutoDeductTy;
diff --git a/clang/lib/AST/ASTImporter.cpp b/clang/lib/AST/ASTImporter.cpp
index ccc6931a5ff..824cc180109 100644
--- a/clang/lib/AST/ASTImporter.cpp
+++ b/clang/lib/AST/ASTImporter.cpp
@@ -1746,7 +1746,7 @@ QualType ASTNodeImporter::VisitAutoType(const AutoType *T) {
       return QualType();
   }
   
-  return Importer.getToContext().getAutoType(ToDeduced, T->isDecltypeAuto(), 
+  return Importer.getToContext().getAutoType(ToDeduced, T->getKeyword(),
                                              /*IsDependent*/false);
 }
 
diff --git a/clang/lib/AST/ItaniumMangle.cpp b/clang/lib/AST/ItaniumMangle.cpp
index c3432839c2e..7f2ef495a20 100644
--- a/clang/lib/AST/ItaniumMangle.cpp
+++ b/clang/lib/AST/ItaniumMangle.cpp
@@ -2653,9 +2653,11 @@ void CXXNameMangler::mangleType(const UnaryTransformType *T) {
 void CXXNameMangler::mangleType(const AutoType *T) {
   QualType D = T->getDeducedType();
   // <builtin-type> ::= Da  # dependent auto
-  if (D.isNull())
+  if (D.isNull()) {
+    assert(T->getKeyword() != AutoTypeKeyword::GNUAutoType &&
+           "shouldn't need to mangle __auto_type!");
     Out << (T->isDecltypeAuto() ? "Dc" : "Da");
-  else
+  } else
     mangleType(D);
 }
 
diff --git a/clang/lib/AST/MicrosoftMangle.cpp b/clang/lib/AST/MicrosoftMangle.cpp
index 5c30ae28b34..01e17588feb 100644
--- a/clang/lib/AST/MicrosoftMangle.cpp
+++ b/clang/lib/AST/MicrosoftMangle.cpp
@@ -1818,6 +1818,8 @@ void MicrosoftCXXNameMangler::mangleFunctionType(const FunctionType *T,
       Out << '?';
       mangleQualifiers(ResultType.getLocalQualifiers(), /*IsMember=*/false);
       Out << '?';
+      assert(AT->getKeyword() != AutoTypeKeyword::GNUAutoType &&
+             "shouldn't need to mangle __auto_type!");
       mangleSourceName(AT->isDecltypeAuto() ? "<decltype-auto>" : "<auto>");
       Out << '@';
     } else {
diff --git a/clang/lib/AST/Type.cpp b/clang/lib/AST/Type.cpp
index 40fe903feab..611218ff917 100644
--- a/clang/lib/AST/Type.cpp
+++ b/clang/lib/AST/Type.cpp
@@ -948,7 +948,7 @@ public:
           == T->getDeducedType().getAsOpaquePtr())
       return QualType(T, 0);
 
-    return Ctx.getAutoType(deducedType, T->isDecltypeAuto(),
+    return Ctx.getAutoType(deducedType, T->getKeyword(),
                            T->isDependentType());
   }
 
diff --git a/clang/lib/AST/TypePrinter.cpp b/clang/lib/AST/TypePrinter.cpp
index 0bb50c6ba81..b4810d63c80 100644
--- a/clang/lib/AST/TypePrinter.cpp
+++ b/clang/lib/AST/TypePrinter.cpp
@@ -835,7 +835,11 @@ void TypePrinter::printAutoBefore(const AutoType *T, raw_ostream &OS) {
   if (!T->getDeducedType().isNull()) {
     printBefore(T->getDeducedType(), OS);
   } else {
-    OS << (T->isDecltypeAuto() ? "decltype(auto)" : "auto");
+    switch (T->getKeyword()) {
+    case AutoTypeKeyword::Auto: OS << "auto"; break;
+    case AutoTypeKeyword::DecltypeAuto: OS << "decltype(auto)"; break;
+    case AutoTypeKeyword::GNUAutoType: OS << "__auto_type"; break;
+    }
     spaceBeforePlaceHolder(OS);
   }
 }
diff --git a/clang/lib/Format/TokenAnnotator.cpp b/clang/lib/Format/TokenAnnotator.cpp
index b44a34115ff..8f08828b5f2 100644
--- a/clang/lib/Format/TokenAnnotator.cpp
+++ b/clang/lib/Format/TokenAnnotator.cpp
@@ -905,7 +905,7 @@ private:
                (!Line.MightBeFunctionDecl || Current.NestingLevel != 0)) {
       Contexts.back().FirstStartOfName = &Current;
       Current.Type = TT_StartOfName;
-    } else if (Current.is(tok::kw_auto)) {
+    } else if (Current.isOneOf(tok::kw_auto, tok::kw___auto_type)) {
       AutoFound = true;
     } else if (Current.is(tok::arrow) &&
                Style.Language == FormatStyle::LK_Java) {
diff --git a/clang/lib/Parse/ParseDecl.cpp b/clang/lib/Parse/ParseDecl.cpp
index 51b4eee24e6..cf3189a91a9 100644
--- a/clang/lib/Parse/ParseDecl.cpp
+++ b/clang/lib/Parse/ParseDecl.cpp
@@ -3138,6 +3138,11 @@ void Parser::ParseDeclarationSpecifiers(DeclSpec &DS,
                                            PrevSpec, DiagID, Policy);
       isStorageClass = true;
       break;
+    case tok::kw___auto_type:
+      Diag(Tok, diag::ext_auto_type);
+      isInvalid = DS.SetTypeSpecType(DeclSpec::TST_auto_type, Loc, PrevSpec,
+                                     DiagID, Policy);
+      break;
     case tok::kw_register:
       isInvalid = DS.SetStorageClassSpec(Actions, DeclSpec::SCS_register, Loc,
                                          PrevSpec, DiagID, Policy);
@@ -4440,6 +4445,7 @@ bool Parser::isDeclarationSpecifier(bool DisambiguatingWithExpression) {
   case tok::kw___private_extern__:
   case tok::kw_static:
   case tok::kw_auto:
+  case tok::kw___auto_type:
   case tok::kw_register:
   case tok::kw___thread:
   case tok::kw_thread_local:
diff --git a/clang/lib/Parse/ParseObjc.cpp b/clang/lib/Parse/ParseObjc.cpp
index 4ac8f42f136..698c38f9c31 100644
--- a/clang/lib/Parse/ParseObjc.cpp
+++ b/clang/lib/Parse/ParseObjc.cpp
@@ -1127,6 +1127,7 @@ IdentifierInfo *Parser::ParseObjCSelectorPiece(SourceLocation &SelectorLoc) {
   case tok::kw__Bool:
   case tok::kw__Complex:
   case tok::kw___alignof:
+  case tok::kw___auto_type:
     IdentifierInfo *II = Tok.getIdentifierInfo();
     SelectorLoc = ConsumeToken();
     return II;
diff --git a/clang/lib/Parse/ParseTentative.cpp b/clang/lib/Parse/ParseTentative.cpp
index 9d2a2b931e8..6fbcfd9bd21 100644
--- a/clang/lib/Parse/ParseTentative.cpp
+++ b/clang/lib/Parse/ParseTentative.cpp
@@ -1089,6 +1089,7 @@ public:
 /// [GNU]     typeof-specifier
 /// [GNU]     '_Complex'
 /// [C++11]   'auto'
+/// [GNU]     '__auto_type'
 /// [C++11]   'decltype' ( expression )
 /// [C++1y]   'decltype' ( 'auto' )
 ///
@@ -1262,6 +1263,7 @@ Parser::isCXXDeclarationSpecifier(Parser::TPResult BracedCastResult,
   case tok::kw_restrict:
   case tok::kw__Complex:
   case tok::kw___attribute:
+  case tok::kw___auto_type:
     return TPResult::True;
 
     // Microsoft
@@ -1515,6 +1517,7 @@ bool Parser::isCXXDeclarationSpecifierAType() {
   case tok::kw_double:
   case tok::kw_void:
   case tok::kw___unknown_anytype:
+  case tok::kw___auto_type:
     return true;
 
   case tok::kw_auto:
diff --git a/clang/lib/Sema/DeclSpec.cpp b/clang/lib/Sema/DeclSpec.cpp
index 05ec5d4abc4..498a375fe1b 100644
--- a/clang/lib/Sema/DeclSpec.cpp
+++ b/clang/lib/Sema/DeclSpec.cpp
@@ -288,6 +288,7 @@ bool Declarator::isDeclarationOfFunction() const {
   switch (DS.getTypeSpecType()) {
     case TST_atomic:
     case TST_auto:
+    case TST_auto_type:
     case TST_bool:
     case TST_char:
     case TST_char16:
@@ -476,6 +477,7 @@ const char *DeclSpec::getSpecifierName(DeclSpec::TST T,
   case DeclSpec::TST_typeofType:
   case DeclSpec::TST_typeofExpr:  return "typeof";
   case DeclSpec::TST_auto:        return "auto";
+  case DeclSpec::TST_auto_type:   return "__auto_type";
   case DeclSpec::TST_decltype:    return "(decltype)";
   case DeclSpec::TST_decltype_auto: return "decltype(auto)";
   case DeclSpec::TST_underlyingType: return "__underlying_type";
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index ed86e854894..18d0c3491b1 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -111,6 +111,7 @@ bool Sema::isSimpleTypeSpecifier(tok::TokenKind Kind) const {
   case tok::kw_wchar_t:
   case tok::kw_bool:
   case tok::kw___underlying_type:
+  case tok::kw___auto_type:
     return true;
 
   case tok::annot_typename:
@@ -5765,7 +5766,10 @@ Sema::ActOnVariableDeclarator(Scope *S, Declarator &D, DeclContext *DC,
     NewVD = VarDecl::Create(Context, DC, D.getLocStart(),
                             D.getIdentifierLoc(), II,
                             R, TInfo, SC);
-  
+
+    if (D.getDeclSpec().containsPlaceholderType() && R->getContainedAutoType())
+      ParsingInitForAutoVars.insert(NewVD);
+
     if (D.isInvalidType())
       NewVD->setInvalidDecl();
   } else {
@@ -10243,7 +10247,7 @@ Sema::BuildDeclaratorGroup(MutableArrayRef<Decl *> Group,
           } else if (DeducedCanon != UCanon) {
             Diag(D->getTypeSourceInfo()->getTypeLoc().getBeginLoc(),
                  diag::err_auto_different_deductions)
-              << (AT->isDecltypeAuto() ? 1 : 0)
+              << (unsigned)AT->getKeyword()
               << Deduced << DeducedDecl->getDeclName()
               << U << D->getDeclName()
               << DeducedDecl->getInit()->getSourceRange()
diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index a1e2c0191f6..aee3e3c49a9 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -349,8 +349,10 @@ bool Sema::DiagnoseUseOfDecl(NamedDecl *D, SourceLocation Loc,
 
   // See if this is an auto-typed variable whose initializer we are parsing.
   if (ParsingInitForAutoVars.count(D)) {
+    const AutoType *AT = cast<VarDecl>(D)->getType()->getContainedAutoType();
+
     Diag(Loc, diag::err_auto_variable_cannot_appear_in_own_initializer)
-      << D->getDeclName();
+      << D->getDeclName() << (unsigned)AT->getKeyword();
     return true;
   }
 
@@ -3685,7 +3687,7 @@ static bool CheckAlignOfExpr(Sema &S, Expr *E) {
     return false;
 
   if (E->getObjectKind() == OK_BitField) {
-    S.Diag(E->getExprLoc(), diag::err_sizeof_alignof_bitfield)
+    S.Diag(E->getExprLoc(), diag::err_sizeof_alignof_typeof_bitfield)
        << 1 << E->getSourceRange();
     return true;
   }
@@ -3787,7 +3789,7 @@ Sema::CreateUnaryExprOrTypeTraitExpr(Expr *E, SourceLocation OpLoc,
       Diag(E->getExprLoc(), diag::err_openmp_default_simd_align_expr);
       isInvalid = true;
   } else if (E->refersToBitField()) {  // C99 6.5.3.4p1.
-    Diag(E->getExprLoc(), diag::err_sizeof_alignof_bitfield) << 0;
+    Diag(E->getExprLoc(), diag::err_sizeof_alignof_typeof_bitfield) << 0;
     isInvalid = true;
   } else {
     isInvalid = CheckUnaryExprOrTypeTraitOperand(E, UETT_SizeOf);
diff --git a/clang/lib/Sema/SemaTemplateDeduction.cpp b/clang/lib/Sema/SemaTemplateDeduction.cpp
index 8b2e7db8a24..2605acddfac 100644
--- a/clang/lib/Sema/SemaTemplateDeduction.cpp
+++ b/clang/lib/Sema/SemaTemplateDeduction.cpp
@@ -3908,7 +3908,7 @@ namespace {
           !Replacement.isNull() && Replacement->isDependentType();
         QualType Result =
           SemaRef.Context.getAutoType(Dependent ? QualType() : Replacement,
-                                      TL.getTypePtr()->isDecltypeAuto(),
+                                      TL.getTypePtr()->getKeyword(),
                                       Dependent);
         AutoTypeLoc NewTL = TLB.push<AutoTypeLoc>(Result);
         NewTL.setNameLoc(TL.getNameLoc());
@@ -3976,6 +3976,11 @@ Sema::DeduceAutoType(TypeLoc Type, Expr *&Init, QualType &Result) {
       if (Result.isNull())
         return DAR_FailedAlreadyDiagnosed;
       return DAR_Succeeded;
+    } else if (!getLangOpts().CPlusPlus) {
+      if (isa<InitListExpr>(Init)) {
+        Diag(Init->getLocStart(), diag::err_auto_init_list_from_c);
+        return DAR_FailedAlreadyDiagnosed;
+      }
     }
   }
 
@@ -4013,6 +4018,11 @@ Sema::DeduceAutoType(TypeLoc Type, Expr *&Init, QualType &Result) {
         return DAR_Failed;
     }
   } else {
+    if (!getLangOpts().CPlusPlus && Init->refersToBitField()) {
+      Diag(Loc, diag::err_auto_bitfield);
+      return DAR_FailedAlreadyDiagnosed;
+    }
+
     if (AdjustFunctionParmAndArgTypesForDeduction(
             *this, TemplateParamsSt.get(), FuncParam, InitType, Init, TDF))
       return DAR_Failed;
diff --git a/clang/lib/Sema/SemaTemplateVariadic.cpp b/clang/lib/Sema/SemaTemplateVariadic.cpp
index a7fef8a29d8..61052f06c83 100644
--- a/clang/lib/Sema/SemaTemplateVariadic.cpp
+++ b/clang/lib/Sema/SemaTemplateVariadic.cpp
@@ -737,6 +737,7 @@ bool Sema::containsUnexpandedParameterPacks(Declarator &D) {
   case TST_interface:
   case TST_class:
   case TST_auto:
+  case TST_auto_type:
   case TST_decltype_auto:
   case TST_unknown_anytype:
   case TST_error:
diff --git a/clang/lib/Sema/SemaType.cpp b/clang/lib/Sema/SemaType.cpp
index e53c7792e50..bbd0c3fbd06 100644
--- a/clang/lib/Sema/SemaType.cpp
+++ b/clang/lib/Sema/SemaType.cpp
@@ -1504,14 +1504,17 @@ static QualType ConvertDeclSpecToType(TypeProcessingState &state) {
       // template type parameter.
       Result = QualType(CorrespondingTemplateParam->getTypeForDecl(), 0);
     } else {
-      Result = Context.getAutoType(QualType(), /*decltype(auto)*/false, false);
+      Result = Context.getAutoType(QualType(), AutoTypeKeyword::Auto, false);
     }
     break;
 
+  case DeclSpec::TST_auto_type:
+    Result = Context.getAutoType(QualType(), AutoTypeKeyword::GNUAutoType, false);
+    break;
+
   case DeclSpec::TST_decltype_auto:
-    Result = Context.getAutoType(QualType(), 
-                                 /*decltype(auto)*/true, 
-                                 /*IsDependent*/   false);
+    Result = Context.getAutoType(QualType(), AutoTypeKeyword::DecltypeAuto,
+                                 /*IsDependent*/ false);
     break;
 
   case DeclSpec::TST_unknown_anytype:
@@ -2573,8 +2576,6 @@ static QualType GetDeclSpecTypeForDeclarator(TypeProcessingState &state,
   // The TagDecl owned by the DeclSpec.
   TagDecl *OwnedTagDecl = nullptr;
 
-  bool ContainsPlaceholderType = false;
-
   switch (D.getName().getKind()) {
   case UnqualifiedId::IK_ImplicitSelfParam:
   case UnqualifiedId::IK_OperatorFunctionId:
@@ -2582,7 +2583,6 @@ static QualType GetDeclSpecTypeForDeclarator(TypeProcessingState &state,
   case UnqualifiedId::IK_LiteralOperatorId:
   case UnqualifiedId::IK_TemplateId:
     T = ConvertDeclSpecToType(state);
-    ContainsPlaceholderType = D.getDeclSpec().containsPlaceholderType();
 
     if (!D.isInvalidType() && D.getDeclSpec().isTypeSpecOwned()) {
       OwnedTagDecl = cast<TagDecl>(D.getDeclSpec().getRepAsDecl());
@@ -2606,7 +2606,6 @@ static QualType GetDeclSpecTypeForDeclarator(TypeProcessingState &state,
     // converts to.
     T = SemaRef.GetTypeFromParser(D.getName().ConversionFunctionId,
                                   &ReturnTypeInfo);
-    ContainsPlaceholderType = T->getContainedAutoType();
     break;
   }
 
@@ -2614,17 +2613,10 @@ static QualType GetDeclSpecTypeForDeclarator(TypeProcessingState &state,
     distributeTypeAttrsFromDeclarator(state, T);
 
   // C++11 [dcl.spec.auto]p5: reject 'auto' if it is not in an allowed context.
-  // In C++11, a function declarator using 'auto' must have a trailing return
-  // type (this is checked later) and we can skip this. In other languages
-  // using auto, we need to check regardless.
-  // C++14 In generic lambdas allow 'auto' in their parameters.
-  if (ContainsPlaceholderType &&
-      (!SemaRef.getLangOpts().CPlusPlus11 || !D.isFunctionDeclarator())) {
+  if (D.getDeclSpec().containsPlaceholderType()) {
     int Error = -1;
 
     switch (D.getContext()) {
-    case Declarator::KNRTypeListContext:
-      llvm_unreachable("K&R type lists aren't allowed in C++");
     case Declarator::LambdaExprContext:
       llvm_unreachable("Can't specify a type specifier in lambda grammar");
     case Declarator::ObjCParameterContext:
@@ -2633,69 +2625,88 @@ static QualType GetDeclSpecTypeForDeclarator(TypeProcessingState &state,
       Error = 0;  
       break;
     case Declarator::LambdaExprParameterContext:
+      // In C++14, generic lambdas allow 'auto' in their parameters.
       if (!(SemaRef.getLangOpts().CPlusPlus14 
               && D.getDeclSpec().getTypeSpecType() == DeclSpec::TST_auto))
-        Error = 14;
+        Error = 16;
       break;
-    case Declarator::MemberContext:
-      if (D.getDeclSpec().getStorageClassSpec() == DeclSpec::SCS_static)
+    case Declarator::MemberContext: {
+      if (D.getDeclSpec().getStorageClassSpec() == DeclSpec::SCS_static ||
+          D.isFunctionDeclarator())
         break;
+      bool Cxx = SemaRef.getLangOpts().CPlusPlus;
       switch (cast<TagDecl>(SemaRef.CurContext)->getTagKind()) {
       case TTK_Enum: llvm_unreachable("unhandled tag kind");
-      case TTK_Struct: Error = 1; /* Struct member */ break;
-      case TTK_Union:  Error = 2; /* Union member */ break;
-      case TTK_Class:  Error = 3; /* Class member */ break;
-      case TTK_Interface: Error = 4; /* Interface member */ break;
+      case TTK_Struct: Error = Cxx ? 1 : 2; /* Struct member */ break;
+      case TTK_Union:  Error = Cxx ? 3 : 4; /* Union member */ break;
+      case TTK_Class:  Error = 5; /* Class member */ break;
+      case TTK_Interface: Error = 6; /* Interface member */ break;
       }
       break;
+    }
     case Declarator::CXXCatchContext:
     case Declarator::ObjCCatchContext:
-      Error = 5; // Exception declaration
+      Error = 7; // Exception declaration
       break;
     case Declarator::TemplateParamContext:
-      Error = 6; // Template parameter
+      Error = 8; // Template parameter
       break;
     case Declarator::BlockLiteralContext:
-      Error = 7; // Block literal
+      Error = 9; // Block literal
       break;
     case Declarator::TemplateTypeArgContext:
-      Error = 8; // Template type argument
+      Error = 10; // Template type argument
       break;
     case Declarator::AliasDeclContext:
     case Declarator::AliasTemplateContext:
-      Error = 10; // Type alias
+      Error = 12; // Type alias
       break;
     case Declarator::TrailingReturnContext:
-      if (!SemaRef.getLangOpts().CPlusPlus14)
-        Error = 11; // Function return type
+      if (!SemaRef.getLangOpts().CPlusPlus14 ||
+          D.getDeclSpec().getTypeSpecType() == DeclSpec::TST_auto_type)
+        Error = 13; // Function return type
       break;
     case Declarator::ConversionIdContext:
-      if (!SemaRef.getLangOpts().CPlusPlus14)
-        Error = 12; // conversion-type-id
+      if (!SemaRef.getLangOpts().CPlusPlus14 ||
+          D.getDeclSpec().getTypeSpecType() == DeclSpec::TST_auto_type)
+        Error = 14; // conversion-type-id
       break;
     case Declarator::TypeNameContext:
-      Error = 13; // Generic
+      Error = 15; // Generic
       break;
     case Declarator::FileContext:
     case Declarator::BlockContext:
     case Declarator::ForContext:
     case Declarator::ConditionContext:
+      break;
     case Declarator::CXXNewContext:
+      if (D.getDeclSpec().getTypeSpecType() == DeclSpec::TST_auto_type)
+        Error = 17; // 'new' type
+      break;
+    case Declarator::KNRTypeListContext:
+      Error = 18; // K&R function parameter
       break;
     }
 
     if (D.getDeclSpec().getStorageClassSpec() == DeclSpec::SCS_typedef)
-      Error = 9;
-
-    // In Objective-C it is an error to use 'auto' on a function declarator.
-    if (D.isFunctionDeclarator())
       Error = 11;
 
+    // In Objective-C it is an error to use 'auto' on a function declarator
+    // (and everywhere for '__auto_type').
+    if (D.isFunctionDeclarator() &&
+        (!SemaRef.getLangOpts().CPlusPlus11 ||
+         D.getDeclSpec().getTypeSpecType() == DeclSpec::TST_auto_type))
+      Error = 13;
+
+    bool HaveTrailing = false;
+
     // C++11 [dcl.spec.auto]p2: 'auto' is always fine if the declarator
     // contains a trailing return type. That is only legal at the outermost
     // level. Check all declarator chunks (outermost first) anyway, to give
     // better diagnostics.
-    if (SemaRef.getLangOpts().CPlusPlus11 && Error != -1) {
+    // We don't support '__auto_type' with trailing return types.
+    if (SemaRef.getLangOpts().CPlusPlus11 &&
+        D.getDeclSpec().getTypeSpecType() != DeclSpec::TST_auto_type) {
       for (unsigned i = 0, e = D.getNumTypeObjects(); i != e; ++i) {
         unsigned chunkIndex = e - i - 1;
         state.setCurrentChunkIndex(chunkIndex);
@@ -2703,6 +2714,7 @@ static QualType GetDeclSpecTypeForDeclarator(TypeProcessingState &state,
         if (DeclType.Kind == DeclaratorChunk::Function) {
           const DeclaratorChunk::FunctionTypeInfo &FTI = DeclType.Fun;
           if (FTI.hasTrailingReturnType()) {
+            HaveTrailing = true;
             Error = -1;
             break;
           }
@@ -2715,16 +2727,24 @@ static QualType GetDeclSpecTypeForDeclarator(TypeProcessingState &state,
       AutoRange = D.getName().getSourceRange();
 
     if (Error != -1) {
-      const bool IsDeclTypeAuto = 
-          D.getDeclSpec().getTypeSpecType() == DeclSpec::TST_decltype_auto;
+      unsigned Keyword;
+      switch (D.getDeclSpec().getTypeSpecType()) {
+      case DeclSpec::TST_auto: Keyword = 0; break;
+      case DeclSpec::TST_decltype_auto: Keyword = 1; break;
+      case DeclSpec::TST_auto_type: Keyword = 2; break;
+      default: llvm_unreachable("unknown auto TypeSpecType");
+      }
       SemaRef.Diag(AutoRange.getBegin(), diag::err_auto_not_allowed)
-        << IsDeclTypeAuto << Error << AutoRange;
+        << Keyword << Error << AutoRange;
       T = SemaRef.Context.IntTy;
       D.setInvalidType(true);
-    } else
+    } else if (!HaveTrailing) {
+      // If there was a trailing return type, we already got
+      // warn_cxx98_compat_trailing_return_type in the parser.
       SemaRef.Diag(AutoRange.getBegin(),
                    diag::warn_cxx98_compat_auto_type_specifier)
         << AutoRange;
+    }
   }
 
   if (SemaRef.getLangOpts().CPlusPlus &&
@@ -3729,7 +3749,7 @@ static TypeSourceInfo *GetFullTypeForDeclarator(TypeProcessingState &state,
             D.setInvalidType(true);
           } else if (D.getContext() != Declarator::LambdaExprContext &&
                      (T.hasQualifiers() || !isa<AutoType>(T) ||
-                      cast<AutoType>(T)->isDecltypeAuto())) {
+                      cast<AutoType>(T)->getKeyword() != AutoTypeKeyword::Auto)) {
             S.Diag(D.getDeclSpec().getTypeSpecTypeLoc(),
                  diag::err_trailing_return_without_auto)
               << T << D.getDeclSpec().getSourceRange();
@@ -6792,6 +6812,9 @@ QualType Sema::BuildTypeofExprType(Expr *E, SourceLocation Loc) {
   if (ER.isInvalid()) return QualType();
   E = ER.get();
 
+  if (!getLangOpts().CPlusPlus && E->refersToBitField())
+    Diag(E->getExprLoc(), diag::err_sizeof_alignof_typeof_bitfield) << 2;
+
   if (!E->isTypeDependent()) {
     QualType T = E->getType();
     if (const TagType *TT = T->getAs<TagType>())
diff --git a/clang/lib/Sema/TreeTransform.h b/clang/lib/Sema/TreeTransform.h
index 12f18c7489d..ca85ad5ea91 100644
--- a/clang/lib/Sema/TreeTransform.h
+++ b/clang/lib/Sema/TreeTransform.h
@@ -848,11 +848,11 @@ public:
   /// \brief Build a new C++11 auto type.
   ///
   /// By default, builds a new AutoType with the given deduced type.
-  QualType RebuildAutoType(QualType Deduced, bool IsDecltypeAuto) {
+  QualType RebuildAutoType(QualType Deduced, AutoTypeKeyword Keyword) {
     // Note, IsDependent is always false here: we implicitly convert an 'auto'
     // which has been deduced to a dependent type into an undeduced 'auto', so
     // that we'll retry deduction after the transformation.
-    return SemaRef.Context.getAutoType(Deduced, IsDecltypeAuto, 
+    return SemaRef.Context.getAutoType(Deduced, Keyword,
                                        /*IsDependent*/ false);
   }
 
@@ -3888,7 +3888,7 @@ TreeTransform<Derived>::TransformQualifiedType(TypeLocBuilder &TLB,
         Qs.removeObjCLifetime();
         Deduced = SemaRef.Context.getQualifiedType(Deduced.getUnqualifiedType(),
                                                    Qs);
-        Result = SemaRef.Context.getAutoType(Deduced, AutoTy->isDecltypeAuto(), 
+        Result = SemaRef.Context.getAutoType(Deduced, AutoTy->getKeyword(),
                                 AutoTy->isDependentType());
         TLB.TypeWasModifiedSafely(Result);
       } else {
@@ -5091,7 +5091,7 @@ QualType TreeTransform<Derived>::TransformAutoType(TypeLocBuilder &TLB,
   QualType Result = TL.getType();
   if (getDerived().AlwaysRebuild() || NewDeduced != OldDeduced ||
       T->isDependentType()) {
-    Result = getDerived().RebuildAutoType(NewDeduced, T->isDecltypeAuto());
+    Result = getDerived().RebuildAutoType(NewDeduced, T->getKeyword());
     if (Result.isNull())
       return QualType();
   }
diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
index 32656037921..fa84b94b082 100644
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -5413,9 +5413,9 @@ QualType ASTReader::readTypeRecord(unsigned Index) {
 
   case TYPE_AUTO: {
     QualType Deduced = readType(*Loc.F, Record, Idx);
-    bool IsDecltypeAuto = Record[Idx++];
+    AutoTypeKeyword Keyword = (AutoTypeKeyword)Record[Idx++];
     bool IsDependent = Deduced.isNull() ? Record[Idx++] : false;
-    return Context.getAutoType(Deduced, IsDecltypeAuto, IsDependent);
+    return Context.getAutoType(Deduced, Keyword, IsDependent);
   }
 
   case TYPE_RECORD: {
diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
index 5508b6eceac..0b257a4a1b0 100644
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -281,7 +281,7 @@ void ASTTypeWriter::VisitUnaryTransformType(const UnaryTransformType *T) {
 
 void ASTTypeWriter::VisitAutoType(const AutoType *T) {
   Writer.AddTypeRef(T->getDeducedType(), Record);
-  Record.push_back(T->isDecltypeAuto());
+  Record.push_back((unsigned)T->getKeyword());
   if (T->getDeducedType().isNull())
     Record.push_back(T->isDependentType());
   Code = TYPE_AUTO;
diff --git a/clang/test/CXX/dcl.dcl/dcl.spec/dcl.type/dcl.spec.auto/p3-1y.cpp b/clang/test/CXX/dcl.dcl/dcl.spec/dcl.type/dcl.spec.auto/p3-1y.cpp
index 39c547b9aec..eb751517e2f 100644
--- a/clang/test/CXX/dcl.dcl/dcl.spec/dcl.type/dcl.spec.auto/p3-1y.cpp
+++ b/clang/test/CXX/dcl.dcl/dcl.spec/dcl.type/dcl.spec.auto/p3-1y.cpp
@@ -3,9 +3,9 @@
 
 // FIXME: This is in p11 (?) in C++1y.
 void f() {
-  decltype(auto) a = a; // expected-error{{variable 'a' declared with 'auto' type cannot appear in its own initializer}}
-  if (decltype(auto) b = b) {} // expected-error {{variable 'b' declared with 'auto' type cannot appear in its own initializer}}
-  decltype(auto) c = ({ decltype(auto) d = c; 0; }); // expected-error {{variable 'c' declared with 'auto' type cannot appear in its own initializer}}
+  decltype(auto) a = a; // expected-error{{variable 'a' declared with 'decltype(auto)' type cannot appear in its own initializer}}
+  if (decltype(auto) b = b) {} // expected-error {{variable 'b' declared with 'decltype(auto)' type cannot appear in its own initializer}}
+  decltype(auto) c = ({ decltype(auto) d = c; 0; }); // expected-error {{variable 'c' declared with 'decltype(auto)' type cannot appear in its own initializer}}
 }
 
 void g() {
diff --git a/clang/test/CXX/dcl.dcl/dcl.spec/dcl.type/dcl.spec.auto/p7-1y.cpp b/clang/test/CXX/dcl.dcl/dcl.spec/dcl.type/dcl.spec.auto/p7-1y.cpp
index c3dc1de3ed6..06bd72e125d 100644
--- a/clang/test/CXX/dcl.dcl/dcl.spec/dcl.type/dcl.spec.auto/p7-1y.cpp
+++ b/clang/test/CXX/dcl.dcl/dcl.spec/dcl.type/dcl.spec.auto/p7-1y.cpp
@@ -49,7 +49,7 @@ decltype(auto) f1();
 decltype(auto) (*f2)(); // expected-error {{'decltype(auto)' can only be used as a return type in a function declaration}} expected-error {{requires an initializer}}
 decltype(auto) *f3(); // expected-error {{cannot form pointer to 'decltype(auto)'}}
 const decltype(auto) f4(); // expected-error {{'decltype(auto)' cannot be combined with other type specifiers}}
-typedef decltype(auto) f5(); // expected-error {{'decltype(auto)' can only be used as a return type in a function declaration}}
+typedef decltype(auto) f5(); // expected-error {{'decltype(auto)' not allowed in typedef}}
 decltype(auto) ((((((f6))))())); // ok
 decltype(auto) f7()(); // expected-error {{'decltype(auto)' can only be used as a return type in a function declaration}} expected-error {{function cannot return function type}}
 decltype(auto) (S::*f8)(); // expected-error {{'decltype(auto)' can only be used as a return type in a function declaration}} expected-error {{requires an initializer}}
diff --git a/clang/test/Sema/bitfield.c b/clang/test/Sema/bitfield.c
index ba8460d3f6c..810dc798eaa 100644
--- a/clang/test/Sema/bitfield.c
+++ b/clang/test/Sema/bitfield.c
@@ -63,7 +63,8 @@ typedef unsigned Unsigned;
 typedef signed Signed;
 
 struct Test5 { unsigned n : 2; } t5;
-typedef __typeof__(t5.n) Unsigned; // Bitfield is unsigned
+// Bitfield is unsigned
+struct Test5 sometest5 = {-1}; // expected-warning {{implicit truncation from 'int' to bitfield changes value from -1 to 3}}
 typedef __typeof__(+t5.n) Signed;  // ... but promotes to signed.
 
 typedef __typeof__(t5.n + 0) Signed; // Arithmetic promotes.
diff --git a/clang/test/Sema/exprs.c b/clang/test/Sema/exprs.c
index 17b1aa2851b..5da4f949a15 100644
--- a/clang/test/Sema/exprs.c
+++ b/clang/test/Sema/exprs.c
@@ -97,6 +97,7 @@ int test9(struct f *P) {
   R = __alignof(P->x);  // expected-error {{invalid application of 'alignof' to bit-field}}
   R = __alignof(P->y);   // ok.
   R = sizeof(P->x); // expected-error {{invalid application of 'sizeof' to bit-field}}
+  __extension__ ({ R = (__typeof__(P->x)) 2; }); // expected-error {{invalid application of 'typeof' to bit-field}}
   return R;
 }
 
diff --git a/clang/test/SemaCXX/auto-cxx0x.cpp b/clang/test/SemaCXX/auto-cxx0x.cpp
index a8f9e84423a..f3daf1a19f3 100644
--- a/clang/test/SemaCXX/auto-cxx0x.cpp
+++ b/clang/test/SemaCXX/auto-cxx0x.cpp
@@ -1,5 +1,8 @@
 // RUN: %clang_cc1 -fsyntax-only -verify %s -std=c++11
+// RUN: %clang_cc1 -fsyntax-only -verify %s -std=c++1y
 void f() {
   auto int a; // expected-warning {{'auto' storage class specifier is not permitted in C++11, and will not be supported in future releases}}
   int auto b; // expected-error{{cannot combine with previous 'int' declaration specifier}}
 }
+
+typedef auto PR25449(); // expected-error {{'auto' not allowed in typedef}}
diff --git a/clang/test/SemaCXX/cxx98-compat.cpp b/clang/test/SemaCXX/cxx98-compat.cpp
index 4227272d14e..25a086d9bcd 100644
--- a/clang/test/SemaCXX/cxx98-compat.cpp
+++ b/clang/test/SemaCXX/cxx98-compat.cpp
@@ -100,6 +100,9 @@ struct RefQualifier {
 };
 
 auto f() -> int; // expected-warning {{trailing return types are incompatible with C++98}}
+#ifdef CXX14COMPAT
+auto ff() { return 5; } // expected-warning {{'auto' type specifier is incompatible with C++98}}
+#endif
 
 void RangeFor() {
   int xs[] = {1, 2, 3};