xref: /external/clang/lib/Sema/SemaDecl.cpp

//===--- SemaDecl.cpp - Semantic Analysis for Declarations ----------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
//  This file implements semantic analysis for declarations.
//
//===----------------------------------------------------------------------===//

#include "clang/Sema/SemaInternal.h"
#include "TypeLocBuilder.h"
#include "clang/AST/ASTConsumer.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/CXXInheritance.h"
#include "clang/AST/CharUnits.h"
#include "clang/AST/CommentDiagnostic.h"
#include "clang/AST/DeclCXX.h"
#include "clang/AST/DeclObjC.h"
#include "clang/AST/DeclTemplate.h"
#include "clang/AST/EvaluatedExprVisitor.h"
#include "clang/AST/ExprCXX.h"
#include "clang/AST/StmtCXX.h"
#include "clang/Basic/PartialDiagnostic.h"
#include "clang/Basic/SourceManager.h"
#include "clang/Basic/TargetInfo.h"
#include "clang/Lex/HeaderSearch.h" // FIXME: Sema shouldn't depend on Lex
#include "clang/Lex/ModuleLoader.h" // FIXME: Sema shouldn't depend on Lex
#include "clang/Lex/Preprocessor.h" // FIXME: Sema shouldn't depend on Lex
#include "clang/Parse/ParseDiagnostic.h"
#include "clang/Sema/CXXFieldCollector.h"
#include "clang/Sema/DeclSpec.h"
#include "clang/Sema/DelayedDiagnostic.h"
#include "clang/Sema/Initialization.h"
#include "clang/Sema/Lookup.h"
#include "clang/Sema/ParsedTemplate.h"
#include "clang/Sema/Scope.h"
#include "clang/Sema/ScopeInfo.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/Triple.h"
#include <algorithm>
#include <cstring>
#include <functional>
using namespace clang;
using namespace sema;

Sema::DeclGroupPtrTy Sema::ConvertDeclToDeclGroup(Decl *Ptr, Decl *OwnedType) {
  if (OwnedType) {
    Decl *Group[2] = { OwnedType, Ptr };
    return DeclGroupPtrTy::make(DeclGroupRef::Create(Context, Group, 2));
  }

  return DeclGroupPtrTy::make(DeclGroupRef(Ptr));
}

namespace {

class TypeNameValidatorCCC : public CorrectionCandidateCallback {
 public:
  TypeNameValidatorCCC(bool AllowInvalid, bool WantClass=false)
      : AllowInvalidDecl(AllowInvalid), WantClassName(WantClass) {
    WantExpressionKeywords = false;
    WantCXXNamedCasts = false;
    WantRemainingKeywords = false;
  }

  virtual bool ValidateCandidate(const TypoCorrection &candidate) {
    if (NamedDecl *ND = candidate.getCorrectionDecl())
      return (isa<TypeDecl>(ND) || isa<ObjCInterfaceDecl>(ND)) &&
          (AllowInvalidDecl || !ND->isInvalidDecl());
    else
      return !WantClassName && candidate.isKeyword();
  }

 private:
  bool AllowInvalidDecl;
  bool WantClassName;
};

}

/// \brief Determine whether the token kind starts a simple-type-specifier.
bool Sema::isSimpleTypeSpecifier(tok::TokenKind Kind) const {
  switch (Kind) {
  // FIXME: Take into account the current language when deciding whether a
  // token kind is a valid type specifier
  case tok::kw_short:
  case tok::kw_long:
  case tok::kw___int64:
  case tok::kw___int128:
  case tok::kw_signed:
  case tok::kw_unsigned:
  case tok::kw_void:
  case tok::kw_char:
  case tok::kw_int:
  case tok::kw_half:
  case tok::kw_float:
  case tok::kw_double:
  case tok::kw_wchar_t:
  case tok::kw_bool:
  case tok::kw___underlying_type:
    return true;

  case tok::annot_typename:
  case tok::kw_char16_t:
  case tok::kw_char32_t:
  case tok::kw_typeof:
  case tok::kw_decltype:
    return getLangOpts().CPlusPlus;

  default:
    break;
  }

  return false;
}

/// \brief If the identifier refers to a type name within this scope,
/// return the declaration of that type.
///
/// This routine performs ordinary name lookup of the identifier II
/// within the given scope, with optional C++ scope specifier SS, to
/// determine whether the name refers to a type. If so, returns an
/// opaque pointer (actually a QualType) corresponding to that
/// type. Otherwise, returns NULL.
///
/// If name lookup results in an ambiguity, this routine will complain
/// and then return NULL.
ParsedType Sema::getTypeName(IdentifierInfo &II, SourceLocation NameLoc,
                             Scope *S, CXXScopeSpec *SS,
                             bool isClassName, bool HasTrailingDot,
                             ParsedType ObjectTypePtr,
                             bool IsCtorOrDtorName,
                             bool WantNontrivialTypeSourceInfo,
                             IdentifierInfo **CorrectedII) {
  // Determine where we will perform name lookup.
  DeclContext *LookupCtx = 0;
  if (ObjectTypePtr) {
    QualType ObjectType = ObjectTypePtr.get();
    if (ObjectType->isRecordType())
      LookupCtx = computeDeclContext(ObjectType);
  } else if (SS && SS->isNotEmpty()) {
    LookupCtx = computeDeclContext(*SS, false);

    if (!LookupCtx) {
      if (isDependentScopeSpecifier(*SS)) {
        // C++ [temp.res]p3:
        //   A qualified-id that refers to a type and in which the
        //   nested-name-specifier depends on a template-parameter (14.6.2)
        //   shall be prefixed by the keyword typename to indicate that the
        //   qualified-id denotes a type, forming an
        //   elaborated-type-specifier (7.1.5.3).
        //
        // We therefore do not perform any name lookup if the result would
        // refer to a member of an unknown specialization.
        if (!isClassName && !IsCtorOrDtorName)
          return ParsedType();

        // We know from the grammar that this name refers to a type,
        // so build a dependent node to describe the type.
        if (WantNontrivialTypeSourceInfo)
          return ActOnTypenameType(S, SourceLocation(), *SS, II, NameLoc).get();

        NestedNameSpecifierLoc QualifierLoc = SS->getWithLocInContext(Context);
        QualType T =
          CheckTypenameType(ETK_None, SourceLocation(), QualifierLoc,
                            II, NameLoc);

          return ParsedType::make(T);
      }

      return ParsedType();
    }

    if (!LookupCtx->isDependentContext() &&
        RequireCompleteDeclContext(*SS, LookupCtx))
      return ParsedType();
  }

  // FIXME: LookupNestedNameSpecifierName isn't the right kind of
  // lookup for class-names.
  LookupNameKind Kind = isClassName ? LookupNestedNameSpecifierName :
                                      LookupOrdinaryName;
  LookupResult Result(*this, &II, NameLoc, Kind);
  if (LookupCtx) {
    // Perform "qualified" name lookup into the declaration context we
    // computed, which is either the type of the base of a member access
    // expression or the declaration context associated with a prior
    // nested-name-specifier.
    LookupQualifiedName(Result, LookupCtx);

    if (ObjectTypePtr && Result.empty()) {
      // C++ [basic.lookup.classref]p3:
      //   If the unqualified-id is ~type-name, the type-name is looked up
      //   in the context of the entire postfix-expression. If the type T of
      //   the object expression is of a class type C, the type-name is also
      //   looked up in the scope of class C. At least one of the lookups shall
      //   find a name that refers to (possibly cv-qualified) T.
      LookupName(Result, S);
    }
  } else {
    // Perform unqualified name lookup.
    LookupName(Result, S);
  }

  NamedDecl *IIDecl = 0;
  switch (Result.getResultKind()) {
  case LookupResult::NotFound:
  case LookupResult::NotFoundInCurrentInstantiation:
    if (CorrectedII) {
      TypeNameValidatorCCC Validator(true, isClassName);
      TypoCorrection Correction = CorrectTypo(Result.getLookupNameInfo(),
                                              Kind, S, SS, Validator);
      IdentifierInfo *NewII = Correction.getCorrectionAsIdentifierInfo();
      TemplateTy Template;
      bool MemberOfUnknownSpecialization;
      UnqualifiedId TemplateName;
      TemplateName.setIdentifier(NewII, NameLoc);
      NestedNameSpecifier *NNS = Correction.getCorrectionSpecifier();
      CXXScopeSpec NewSS, *NewSSPtr = SS;
      if (SS && NNS) {
        NewSS.MakeTrivial(Context, NNS, SourceRange(NameLoc));
        NewSSPtr = &NewSS;
      }
      if (Correction && (NNS || NewII != &II) &&
          // Ignore a correction to a template type as the to-be-corrected
          // identifier is not a template (typo correction for template names
          // is handled elsewhere).
          !(getLangOpts().CPlusPlus && NewSSPtr &&
            isTemplateName(S, *NewSSPtr, false, TemplateName, ParsedType(),
                           false, Template, MemberOfUnknownSpecialization))) {
        ParsedType Ty = getTypeName(*NewII, NameLoc, S, NewSSPtr,
                                    isClassName, HasTrailingDot, ObjectTypePtr,
                                    IsCtorOrDtorName,
                                    WantNontrivialTypeSourceInfo);
        if (Ty) {
          std::string CorrectedStr(Correction.getAsString(getLangOpts()));
          std::string CorrectedQuotedStr(
              Correction.getQuoted(getLangOpts()));
          Diag(NameLoc, diag::err_unknown_type_or_class_name_suggest)
              << Result.getLookupName() << CorrectedQuotedStr << isClassName
              << FixItHint::CreateReplacement(SourceRange(NameLoc),
                                              CorrectedStr);
          if (NamedDecl *FirstDecl = Correction.getCorrectionDecl())
            Diag(FirstDecl->getLocation(), diag::note_previous_decl)
              << CorrectedQuotedStr;

          if (SS && NNS)
            SS->MakeTrivial(Context, NNS, SourceRange(NameLoc));
          *CorrectedII = NewII;
          return Ty;
        }
      }
    }
    // If typo correction failed or was not performed, fall through
  case LookupResult::FoundOverloaded:
  case LookupResult::FoundUnresolvedValue:
    Result.suppressDiagnostics();
    return ParsedType();

  case LookupResult::Ambiguous:
    // Recover from type-hiding ambiguities by hiding the type.  We'll
    // do the lookup again when looking for an object, and we can
    // diagnose the error then.  If we don't do this, then the error
    // about hiding the type will be immediately followed by an error
    // that only makes sense if the identifier was treated like a type.
    if (Result.getAmbiguityKind() == LookupResult::AmbiguousTagHiding) {
      Result.suppressDiagnostics();
      return ParsedType();
    }

    // Look to see if we have a type anywhere in the list of results.
    for (LookupResult::iterator Res = Result.begin(), ResEnd = Result.end();
         Res != ResEnd; ++Res) {
      if (isa<TypeDecl>(*Res) || isa<ObjCInterfaceDecl>(*Res)) {
        if (!IIDecl ||
            (*Res)->getLocation().getRawEncoding() <
              IIDecl->getLocation().getRawEncoding())
          IIDecl = *Res;
      }
    }

    if (!IIDecl) {
      // None of the entities we found is a type, so there is no way
      // to even assume that the result is a type. In this case, don't
      // complain about the ambiguity. The parser will either try to
      // perform this lookup again (e.g., as an object name), which
      // will produce the ambiguity, or will complain that it expected
      // a type name.
      Result.suppressDiagnostics();
      return ParsedType();
    }

    // We found a type within the ambiguous lookup; diagnose the
    // ambiguity and then return that type. This might be the right
    // answer, or it might not be, but it suppresses any attempt to
    // perform the name lookup again.
    break;

  case LookupResult::Found:
    IIDecl = Result.getFoundDecl();
    break;
  }

  assert(IIDecl && "Didn't find decl");

  QualType T;
  if (TypeDecl *TD = dyn_cast<TypeDecl>(IIDecl)) {
    DiagnoseUseOfDecl(IIDecl, NameLoc);

    if (T.isNull())
      T = Context.getTypeDeclType(TD);

    // NOTE: avoid constructing an ElaboratedType(Loc) if this is a
    // constructor or destructor name (in such a case, the scope specifier
    // will be attached to the enclosing Expr or Decl node).
    if (SS && SS->isNotEmpty() && !IsCtorOrDtorName) {
      if (WantNontrivialTypeSourceInfo) {
        // Construct a type with type-source information.
        TypeLocBuilder Builder;
        Builder.pushTypeSpec(T).setNameLoc(NameLoc);

        T = getElaboratedType(ETK_None, *SS, T);
        ElaboratedTypeLoc ElabTL = Builder.push<ElaboratedTypeLoc>(T);
        ElabTL.setElaboratedKeywordLoc(SourceLocation());
        ElabTL.setQualifierLoc(SS->getWithLocInContext(Context));
        return CreateParsedType(T, Builder.getTypeSourceInfo(Context, T));
      } else {
        T = getElaboratedType(ETK_None, *SS, T);
      }
    }
  } else if (ObjCInterfaceDecl *IDecl = dyn_cast<ObjCInterfaceDecl>(IIDecl)) {
    (void)DiagnoseUseOfDecl(IDecl, NameLoc);
    if (!HasTrailingDot)
      T = Context.getObjCInterfaceType(IDecl);
  }

  if (T.isNull()) {
    // If it's not plausibly a type, suppress diagnostics.
    Result.suppressDiagnostics();
    return ParsedType();
  }
  return ParsedType::make(T);
}

/// isTagName() - This method is called *for error recovery purposes only*
/// to determine if the specified name is a valid tag name ("struct foo").  If
/// so, this returns the TST for the tag corresponding to it (TST_enum,
/// TST_union, TST_struct, TST_interface, TST_class).  This is used to diagnose
/// cases in C where the user forgot to specify the tag.
DeclSpec::TST Sema::isTagName(IdentifierInfo &II, Scope *S) {
  // Do a tag name lookup in this scope.
  LookupResult R(*this, &II, SourceLocation(), LookupTagName);
  LookupName(R, S, false);
  R.suppressDiagnostics();
  if (R.getResultKind() == LookupResult::Found)
    if (const TagDecl *TD = R.getAsSingle<TagDecl>()) {
      switch (TD->getTagKind()) {
      case TTK_Struct: return DeclSpec::TST_struct;
      case TTK_Interface: return DeclSpec::TST_interface;
      case TTK_Union:  return DeclSpec::TST_union;
      case TTK_Class:  return DeclSpec::TST_class;
      case TTK_Enum:   return DeclSpec::TST_enum;
      }
    }

  return DeclSpec::TST_unspecified;
}

/// isMicrosoftMissingTypename - In Microsoft mode, within class scope,
/// if a CXXScopeSpec's type is equal to the type of one of the base classes
/// then downgrade the missing typename error to a warning.
/// This is needed for MSVC compatibility; Example:
/// @code
/// template<class T> class A {
/// public:
///   typedef int TYPE;
/// };
/// template<class T> class B : public A<T> {
/// public:
///   A<T>::TYPE a; // no typename required because A<T> is a base class.
/// };
/// @endcode
bool Sema::isMicrosoftMissingTypename(const CXXScopeSpec *SS, Scope *S) {
  if (CurContext->isRecord()) {
    const Type *Ty = SS->getScopeRep()->getAsType();

    CXXRecordDecl *RD = cast<CXXRecordDecl>(CurContext);
    for (CXXRecordDecl::base_class_const_iterator Base = RD->bases_begin(),
          BaseEnd = RD->bases_end(); Base != BaseEnd; ++Base)
      if (Context.hasSameUnqualifiedType(QualType(Ty, 1), Base->getType()))
        return true;
    return S->isFunctionPrototypeScope();
  }
  return CurContext->isFunctionOrMethod() || S->isFunctionPrototypeScope();
}

bool Sema::DiagnoseUnknownTypeName(IdentifierInfo *&II,
                                   SourceLocation IILoc,
                                   Scope *S,
                                   CXXScopeSpec *SS,
                                   ParsedType &SuggestedType) {
  // We don't have anything to suggest (yet).
  SuggestedType = ParsedType();

  // There may have been a typo in the name of the type. Look up typo
  // results, in case we have something that we can suggest.
  TypeNameValidatorCCC Validator(false);
  if (TypoCorrection Corrected = CorrectTypo(DeclarationNameInfo(II, IILoc),
                                             LookupOrdinaryName, S, SS,
                                             Validator)) {
    std::string CorrectedStr(Corrected.getAsString(getLangOpts()));
    std::string CorrectedQuotedStr(Corrected.getQuoted(getLangOpts()));

    if (Corrected.isKeyword()) {
      // We corrected to a keyword.
      IdentifierInfo *NewII = Corrected.getCorrectionAsIdentifierInfo();
      if (!isSimpleTypeSpecifier(NewII->getTokenID()))
        CorrectedQuotedStr = "the keyword " + CorrectedQuotedStr;
      Diag(IILoc, diag::err_unknown_typename_suggest)
        << II << CorrectedQuotedStr
        << FixItHint::CreateReplacement(SourceRange(IILoc), CorrectedStr);
      II = NewII;
    } else {
      NamedDecl *Result = Corrected.getCorrectionDecl();
      // We found a similarly-named type or interface; suggest that.
      if (!SS || !SS->isSet())
        Diag(IILoc, diag::err_unknown_typename_suggest)
          << II << CorrectedQuotedStr
          << FixItHint::CreateReplacement(SourceRange(IILoc), CorrectedStr);
      else if (DeclContext *DC = computeDeclContext(*SS, false))
        Diag(IILoc, diag::err_unknown_nested_typename_suggest)
          << II << DC << CorrectedQuotedStr << SS->getRange()
          << FixItHint::CreateReplacement(Corrected.getCorrectionRange(),
                                          CorrectedStr);
      else
        llvm_unreachable("could not have corrected a typo here");

      Diag(Result->getLocation(), diag::note_previous_decl)
        << CorrectedQuotedStr;

      SuggestedType = getTypeName(*Result->getIdentifier(), IILoc, S, SS,
                                  false, false, ParsedType(),
                                  /*IsCtorOrDtorName=*/false,
                                  /*NonTrivialTypeSourceInfo=*/true);
    }
    return true;
  }

  if (getLangOpts().CPlusPlus) {
    // See if II is a class template that the user forgot to pass arguments to.
    UnqualifiedId Name;
    Name.setIdentifier(II, IILoc);
    CXXScopeSpec EmptySS;
    TemplateTy TemplateResult;
    bool MemberOfUnknownSpecialization;
    if (isTemplateName(S, SS ? *SS : EmptySS, /*hasTemplateKeyword=*/false,
                       Name, ParsedType(), true, TemplateResult,
                       MemberOfUnknownSpecialization) == TNK_Type_template) {
      TemplateName TplName = TemplateResult.getAsVal<TemplateName>();
      Diag(IILoc, diag::err_template_missing_args) << TplName;
      if (TemplateDecl *TplDecl = TplName.getAsTemplateDecl()) {
        Diag(TplDecl->getLocation(), diag::note_template_decl_here)
          << TplDecl->getTemplateParameters()->getSourceRange();
      }
      return true;
    }
  }

  // FIXME: Should we move the logic that tries to recover from a missing tag
  // (struct, union, enum) from Parser::ParseImplicitInt here, instead?

  if (!SS || (!SS->isSet() && !SS->isInvalid()))
    Diag(IILoc, diag::err_unknown_typename) << II;
  else if (DeclContext *DC = computeDeclContext(*SS, false))
    Diag(IILoc, diag::err_typename_nested_not_found)
      << II << DC << SS->getRange();
  else if (isDependentScopeSpecifier(*SS)) {
    unsigned DiagID = diag::err_typename_missing;
    if (getLangOpts().MicrosoftMode && isMicrosoftMissingTypename(SS, S))
      DiagID = diag::warn_typename_missing;

    Diag(SS->getRange().getBegin(), DiagID)
      << (NestedNameSpecifier *)SS->getScopeRep() << II->getName()
      << SourceRange(SS->getRange().getBegin(), IILoc)
      << FixItHint::CreateInsertion(SS->getRange().getBegin(), "typename ");
    SuggestedType = ActOnTypenameType(S, SourceLocation(),
                                      *SS, *II, IILoc).get();
  } else {
    assert(SS && SS->isInvalid() &&
           "Invalid scope specifier has already been diagnosed");
  }

  return true;
}

/// \brief Determine whether the given result set contains either a type name
/// or
static bool isResultTypeOrTemplate(LookupResult &R, const Token &NextToken) {
  bool CheckTemplate = R.getSema().getLangOpts().CPlusPlus &&
                       NextToken.is(tok::less);

  for (LookupResult::iterator I = R.begin(), IEnd = R.end(); I != IEnd; ++I) {
    if (isa<TypeDecl>(*I) || isa<ObjCInterfaceDecl>(*I))
      return true;

    if (CheckTemplate && isa<TemplateDecl>(*I))
      return true;
  }

  return false;
}

static bool isTagTypeWithMissingTag(Sema &SemaRef, LookupResult &Result,
                                    Scope *S, CXXScopeSpec &SS,
                                    IdentifierInfo *&Name,
                                    SourceLocation NameLoc) {
  LookupResult R(SemaRef, Name, NameLoc, Sema::LookupTagName);
  SemaRef.LookupParsedName(R, S, &SS);
  if (TagDecl *Tag = R.getAsSingle<TagDecl>()) {
    const char *TagName = 0;
    const char *FixItTagName = 0;
    switch (Tag->getTagKind()) {
      case TTK_Class:
        TagName = "class";
        FixItTagName = "class ";
        break;

      case TTK_Enum:
        TagName = "enum";
        FixItTagName = "enum ";
        break;

      case TTK_Struct:
        TagName = "struct";
        FixItTagName = "struct ";
        break;

      case TTK_Interface:
        TagName = "__interface";
        FixItTagName = "__interface ";
        break;

      case TTK_Union:
        TagName = "union";
        FixItTagName = "union ";
        break;
    }

    SemaRef.Diag(NameLoc, diag::err_use_of_tag_name_without_tag)
      << Name << TagName << SemaRef.getLangOpts().CPlusPlus
      << FixItHint::CreateInsertion(NameLoc, FixItTagName);

    for (LookupResult::iterator I = Result.begin(), IEnd = Result.end();
         I != IEnd; ++I)
      SemaRef.Diag((*I)->getLocation(), diag::note_decl_hiding_tag_type)
        << Name << TagName;

    // Replace lookup results with just the tag decl.
    Result.clear(Sema::LookupTagName);
    SemaRef.LookupParsedName(Result, S, &SS);
    return true;
  }

  return false;
}

/// Build a ParsedType for a simple-type-specifier with a nested-name-specifier.
static ParsedType buildNestedType(Sema &S, CXXScopeSpec &SS,
                                  QualType T, SourceLocation NameLoc) {
  ASTContext &Context = S.Context;

  TypeLocBuilder Builder;
  Builder.pushTypeSpec(T).setNameLoc(NameLoc);

  T = S.getElaboratedType(ETK_None, SS, T);
  ElaboratedTypeLoc ElabTL = Builder.push<ElaboratedTypeLoc>(T);
  ElabTL.setElaboratedKeywordLoc(SourceLocation());
  ElabTL.setQualifierLoc(SS.getWithLocInContext(Context));
  return S.CreateParsedType(T, Builder.getTypeSourceInfo(Context, T));
}

Sema::NameClassification Sema::ClassifyName(Scope *S,
                                            CXXScopeSpec &SS,
                                            IdentifierInfo *&Name,
                                            SourceLocation NameLoc,
                                            const Token &NextToken,
                                            bool IsAddressOfOperand,
                                            CorrectionCandidateCallback *CCC) {
  DeclarationNameInfo NameInfo(Name, NameLoc);
  ObjCMethodDecl *CurMethod = getCurMethodDecl();

  if (NextToken.is(tok::coloncolon)) {
    BuildCXXNestedNameSpecifier(S, *Name, NameLoc, NextToken.getLocation(),
                                QualType(), false, SS, 0, false);

  }

  LookupResult Result(*this, Name, NameLoc, LookupOrdinaryName);
  LookupParsedName(Result, S, &SS, !CurMethod);

  // Perform lookup for Objective-C instance variables (including automatically
  // synthesized instance variables), if we're in an Objective-C method.
  // FIXME: This lookup really, really needs to be folded in to the normal
  // unqualified lookup mechanism.
  if (!SS.isSet() && CurMethod && !isResultTypeOrTemplate(Result, NextToken)) {
    ExprResult E = LookupInObjCMethod(Result, S, Name, true);
    if (E.get() || E.isInvalid())
      return E;
  }

  bool SecondTry = false;
  bool IsFilteredTemplateName = false;

Corrected:
  switch (Result.getResultKind()) {
  case LookupResult::NotFound:
    // If an unqualified-id is followed by a '(', then we have a function
    // call.
    if (!SS.isSet() && NextToken.is(tok::l_paren)) {
      // In C++, this is an ADL-only call.
      // FIXME: Reference?
      if (getLangOpts().CPlusPlus)
        return BuildDeclarationNameExpr(SS, Result, /*ADL=*/true);

      // C90 6.3.2.2:
      //   If the expression that precedes the parenthesized argument list in a
      //   function call consists solely of an identifier, and if no
      //   declaration is visible for this identifier, the identifier is
      //   implicitly declared exactly as if, in the innermost block containing
      //   the function call, the declaration
      //
      //     extern int identifier ();
      //
      //   appeared.
      //
      // We also allow this in C99 as an extension.
      if (NamedDecl *D = ImplicitlyDefineFunction(NameLoc, *Name, S)) {
        Result.addDecl(D);
        Result.resolveKind();
        return BuildDeclarationNameExpr(SS, Result, /*ADL=*/false);
      }
    }

    // In C, we first see whether there is a tag type by the same name, in
    // which case it's likely that the user just forget to write "enum",
    // "struct", or "union".
    if (!getLangOpts().CPlusPlus && !SecondTry &&
        isTagTypeWithMissingTag(*this, Result, S, SS, Name, NameLoc)) {
      break;
    }

    // Perform typo correction to determine if there is another name that is
    // close to this name.
    if (!SecondTry && CCC) {
      SecondTry = true;
      if (TypoCorrection Corrected = CorrectTypo(Result.getLookupNameInfo(),
                                                 Result.getLookupKind(), S,
                                                 &SS, *CCC)) {
        unsigned UnqualifiedDiag = diag::err_undeclared_var_use_suggest;
        unsigned QualifiedDiag = diag::err_no_member_suggest;
        std::string CorrectedStr(Corrected.getAsString(getLangOpts()));
        std::string CorrectedQuotedStr(Corrected.getQuoted(getLangOpts()));

        NamedDecl *FirstDecl = Corrected.getCorrectionDecl();
        NamedDecl *UnderlyingFirstDecl
          = FirstDecl? FirstDecl->getUnderlyingDecl() : 0;
        if (getLangOpts().CPlusPlus && NextToken.is(tok::less) &&
            UnderlyingFirstDecl && isa<TemplateDecl>(UnderlyingFirstDecl)) {
          UnqualifiedDiag = diag::err_no_template_suggest;
          QualifiedDiag = diag::err_no_member_template_suggest;
        } else if (UnderlyingFirstDecl &&
                   (isa<TypeDecl>(UnderlyingFirstDecl) ||
                    isa<ObjCInterfaceDecl>(UnderlyingFirstDecl) ||
                    isa<ObjCCompatibleAliasDecl>(UnderlyingFirstDecl))) {
           UnqualifiedDiag = diag::err_unknown_typename_suggest;
           QualifiedDiag = diag::err_unknown_nested_typename_suggest;
         }

        if (SS.isEmpty())
          Diag(NameLoc, UnqualifiedDiag)
            << Name << CorrectedQuotedStr
            << FixItHint::CreateReplacement(NameLoc, CorrectedStr);
        else // FIXME: is this even reachable? Test it.
          Diag(NameLoc, QualifiedDiag)
            << Name << computeDeclContext(SS, false) << CorrectedQuotedStr
            << SS.getRange()
            << FixItHint::CreateReplacement(Corrected.getCorrectionRange(),
                                            CorrectedStr);

        // Update the name, so that the caller has the new name.
        Name = Corrected.getCorrectionAsIdentifierInfo();

        // Typo correction corrected to a keyword.
        if (Corrected.isKeyword())
          return Corrected.getCorrectionAsIdentifierInfo();

        // Also update the LookupResult...
        // FIXME: This should probably go away at some point
        Result.clear();
        Result.setLookupName(Corrected.getCorrection());
        if (FirstDecl) {
          Result.addDecl(FirstDecl);
          Diag(FirstDecl->getLocation(), diag::note_previous_decl)
            << CorrectedQuotedStr;
        }

        // If we found an Objective-C instance variable, let
        // LookupInObjCMethod build the appropriate expression to
        // reference the ivar.
        // FIXME: This is a gross hack.
        if (ObjCIvarDecl *Ivar = Result.getAsSingle<ObjCIvarDecl>()) {
          Result.clear();
          ExprResult E(LookupInObjCMethod(Result, S, Ivar->getIdentifier()));
          return E;
        }

        goto Corrected;
      }
    }

    // We failed to correct; just fall through and let the parser deal with it.
    Result.suppressDiagnostics();
    return NameClassification::Unknown();

  case LookupResult::NotFoundInCurrentInstantiation: {
    // We performed name lookup into the current instantiation, and there were
    // dependent bases, so we treat this result the same way as any other
    // dependent nested-name-specifier.

    // C++ [temp.res]p2:
    //   A name used in a template declaration or definition and that is
    //   dependent on a template-parameter is assumed not to name a type
    //   unless the applicable name lookup finds a type name or the name is
    //   qualified by the keyword typename.
    //
    // FIXME: If the next token is '<', we might want to ask the parser to
    // perform some heroics to see if we actually have a
    // template-argument-list, which would indicate a missing 'template'
    // keyword here.
    return ActOnDependentIdExpression(SS, /*TemplateKWLoc=*/SourceLocation(),
                                      NameInfo, IsAddressOfOperand,
                                      /*TemplateArgs=*/0);
  }

  case LookupResult::Found:
  case LookupResult::FoundOverloaded:
  case LookupResult::FoundUnresolvedValue:
    break;

  case LookupResult::Ambiguous:
    if (getLangOpts().CPlusPlus && NextToken.is(tok::less) &&
        hasAnyAcceptableTemplateNames(Result)) {
      // C++ [temp.local]p3:
      //   A lookup that finds an injected-class-name (10.2) can result in an
      //   ambiguity in certain cases (for example, if it is found in more than
      //   one base class). If all of the injected-class-names that are found
      //   refer to specializations of the same class template, and if the name
      //   is followed by a template-argument-list, the reference refers to the
      //   class template itself and not a specialization thereof, and is not
      //   ambiguous.
      //
      // This filtering can make an ambiguous result into an unambiguous one,
      // so try again after filtering out template names.
      FilterAcceptableTemplateNames(Result);
      if (!Result.isAmbiguous()) {
        IsFilteredTemplateName = true;
        break;
      }
    }

    // Diagnose the ambiguity and return an error.
    return NameClassification::Error();
  }

  if (getLangOpts().CPlusPlus && NextToken.is(tok::less) &&
      (IsFilteredTemplateName || hasAnyAcceptableTemplateNames(Result))) {
    // C++ [temp.names]p3:
    //   After name lookup (3.4) finds that a name is a template-name or that
    //   an operator-function-id or a literal- operator-id refers to a set of
    //   overloaded functions any member of which is a function template if
    //   this is followed by a <, the < is always taken as the delimiter of a
    //   template-argument-list and never as the less-than operator.
    if (!IsFilteredTemplateName)
      FilterAcceptableTemplateNames(Result);

    if (!Result.empty()) {
      bool IsFunctionTemplate;
      TemplateName Template;
      if (Result.end() - Result.begin() > 1) {
        IsFunctionTemplate = true;
        Template = Context.getOverloadedTemplateName(Result.begin(),
                                                     Result.end());
      } else {
        TemplateDecl *TD
          = cast<TemplateDecl>((*Result.begin())->getUnderlyingDecl());
        IsFunctionTemplate = isa<FunctionTemplateDecl>(TD);

        if (SS.isSet() && !SS.isInvalid())
          Template = Context.getQualifiedTemplateName(SS.getScopeRep(),
                                                    /*TemplateKeyword=*/false,
                                                      TD);
        else
          Template = TemplateName(TD);
      }

      if (IsFunctionTemplate) {
        // Function templates always go through overload resolution, at which
        // point we'll perform the various checks (e.g., accessibility) we need
        // to based on which function we selected.
        Result.suppressDiagnostics();

        return NameClassification::FunctionTemplate(Template);
      }

      return NameClassification::TypeTemplate(Template);
    }
  }

  NamedDecl *FirstDecl = (*Result.begin())->getUnderlyingDecl();
  if (TypeDecl *Type = dyn_cast<TypeDecl>(FirstDecl)) {
    DiagnoseUseOfDecl(Type, NameLoc);
    QualType T = Context.getTypeDeclType(Type);
    if (SS.isNotEmpty())
      return buildNestedType(*this, SS, T, NameLoc);
    return ParsedType::make(T);
  }

  ObjCInterfaceDecl *Class = dyn_cast<ObjCInterfaceDecl>(FirstDecl);
  if (!Class) {
    // FIXME: It's unfortunate that we don't have a Type node for handling this.
    if (ObjCCompatibleAliasDecl *Alias
                                = dyn_cast<ObjCCompatibleAliasDecl>(FirstDecl))
      Class = Alias->getClassInterface();
  }

  if (Class) {
    DiagnoseUseOfDecl(Class, NameLoc);

    if (NextToken.is(tok::period)) {
      // Interface. <something> is parsed as a property reference expression.
      // Just return "unknown" as a fall-through for now.
      Result.suppressDiagnostics();
      return NameClassification::Unknown();
    }

    QualType T = Context.getObjCInterfaceType(Class);
    return ParsedType::make(T);
  }

  // We can have a type template here if we're classifying a template argument.
  if (isa<TemplateDecl>(FirstDecl) && !isa<FunctionTemplateDecl>(FirstDecl))
    return NameClassification::TypeTemplate(
        TemplateName(cast<TemplateDecl>(FirstDecl)));

  // Check for a tag type hidden by a non-type decl in a few cases where it
  // seems likely a type is wanted instead of the non-type that was found.
  if (!getLangOpts().ObjC1) {
    bool NextIsOp = NextToken.is(tok::amp) || NextToken.is(tok::star);
    if ((NextToken.is(tok::identifier) ||
         (NextIsOp && FirstDecl->isFunctionOrFunctionTemplate())) &&
        isTagTypeWithMissingTag(*this, Result, S, SS, Name, NameLoc)) {
      TypeDecl *Type = Result.getAsSingle<TypeDecl>();
      DiagnoseUseOfDecl(Type, NameLoc);
      QualType T = Context.getTypeDeclType(Type);
      if (SS.isNotEmpty())
        return buildNestedType(*this, SS, T, NameLoc);
      return ParsedType::make(T);
    }
  }

  if (FirstDecl->isCXXClassMember())
    return BuildPossibleImplicitMemberExpr(SS, SourceLocation(), Result, 0);

  bool ADL = UseArgumentDependentLookup(SS, Result, NextToken.is(tok::l_paren));
  return BuildDeclarationNameExpr(SS, Result, ADL);
}

// Determines the context to return to after temporarily entering a
// context.  This depends in an unnecessarily complicated way on the
// exact ordering of callbacks from the parser.
DeclContext *Sema::getContainingDC(DeclContext *DC) {

  // Functions defined inline within classes aren't parsed until we've
  // finished parsing the top-level class, so the top-level class is
  // the context we'll need to return to.
  if (isa<FunctionDecl>(DC)) {
    DC = DC->getLexicalParent();

    // A function not defined within a class will always return to its
    // lexical context.
    if (!isa<CXXRecordDecl>(DC))
      return DC;

    // A C++ inline method/friend is parsed *after* the topmost class
    // it was declared in is fully parsed ("complete");  the topmost
    // class is the context we need to return to.
    while (CXXRecordDecl *RD = dyn_cast<CXXRecordDecl>(DC->getLexicalParent()))
      DC = RD;

    // Return the declaration context of the topmost class the inline method is
    // declared in.
    return DC;
  }

  return DC->getLexicalParent();
}

void Sema::PushDeclContext(Scope *S, DeclContext *DC) {
  assert(getContainingDC(DC) == CurContext &&
      "The next DeclContext should be lexically contained in the current one.");
  CurContext = DC;
  S->setEntity(DC);
}

void Sema::PopDeclContext() {
  assert(CurContext && "DeclContext imbalance!");

  CurContext = getContainingDC(CurContext);
  assert(CurContext && "Popped translation unit!");
}

/// EnterDeclaratorContext - Used when we must lookup names in the context
/// of a declarator's nested name specifier.
///
void Sema::EnterDeclaratorContext(Scope *S, DeclContext *DC) {
  // C++0x [basic.lookup.unqual]p13:
  //   A name used in the definition of a static data member of class
  //   X (after the qualified-id of the static member) is looked up as
  //   if the name was used in a member function of X.
  // C++0x [basic.lookup.unqual]p14:
  //   If a variable member of a namespace is defined outside of the
  //   scope of its namespace then any name used in the definition of
  //   the variable member (after the declarator-id) is looked up as
  //   if the definition of the variable member occurred in its
  //   namespace.
  // Both of these imply that we should push a scope whose context
  // is the semantic context of the declaration.  We can't use
  // PushDeclContext here because that context is not necessarily
  // lexically contained in the current context.  Fortunately,
  // the containing scope should have the appropriate information.

  assert(!S->getEntity() && "scope already has entity");

#ifndef NDEBUG
  Scope *Ancestor = S->getParent();
  while (!Ancestor->getEntity()) Ancestor = Ancestor->getParent();
  assert(Ancestor->getEntity() == CurContext && "ancestor context mismatch");
#endif

  CurContext = DC;
  S->setEntity(DC);
}

void Sema::ExitDeclaratorContext(Scope *S) {
  assert(S->getEntity() == CurContext && "Context imbalance!");

  // Switch back to the lexical context.  The safety of this is
  // enforced by an assert in EnterDeclaratorContext.
  Scope *Ancestor = S->getParent();
  while (!Ancestor->getEntity()) Ancestor = Ancestor->getParent();
  CurContext = (DeclContext*) Ancestor->getEntity();

  // We don't need to do anything with the scope, which is going to
  // disappear.
}


void Sema::ActOnReenterFunctionContext(Scope* S, Decl *D) {
  FunctionDecl *FD = dyn_cast<FunctionDecl>(D);
  if (FunctionTemplateDecl *TFD = dyn_cast_or_null<FunctionTemplateDecl>(D)) {
    // We assume that the caller has already called
    // ActOnReenterTemplateScope
    FD = TFD->getTemplatedDecl();
  }
  if (!FD)
    return;

  // Same implementation as PushDeclContext, but enters the context
  // from the lexical parent, rather than the top-level class.
  assert(CurContext == FD->getLexicalParent() &&
    "The next DeclContext should be lexically contained in the current one.");
  CurContext = FD;
  S->setEntity(CurContext);

  for (unsigned P = 0, NumParams = FD->getNumParams(); P < NumParams; ++P) {
    ParmVarDecl *Param = FD->getParamDecl(P);
    // If the parameter has an identifier, then add it to the scope
    if (Param->getIdentifier()) {
      S->AddDecl(Param);
      IdResolver.AddDecl(Param);
    }
  }
}


void Sema::ActOnExitFunctionContext() {
  // Same implementation as PopDeclContext, but returns to the lexical parent,
  // rather than the top-level class.
  assert(CurContext && "DeclContext imbalance!");
  CurContext = CurContext->getLexicalParent();
  assert(CurContext && "Popped translation unit!");
}


/// \brief Determine whether we allow overloading of the function
/// PrevDecl with another declaration.
///
/// This routine determines whether overloading is possible, not
/// whether some new function is actually an overload. It will return
/// true in C++ (where we can always provide overloads) or, as an
/// extension, in C when the previous function is already an
/// overloaded function declaration or has the "overloadable"
/// attribute.
static bool AllowOverloadingOfFunction(LookupResult &Previous,
                                       ASTContext &Context) {
  if (Context.getLangOpts().CPlusPlus)
    return true;

  if (Previous.getResultKind() == LookupResult::FoundOverloaded)
    return true;

  return (Previous.getResultKind() == LookupResult::Found
          && Previous.getFoundDecl()->hasAttr<OverloadableAttr>());
}

/// Add this decl to the scope shadowed decl chains.
void Sema::PushOnScopeChains(NamedDecl *D, Scope *S, bool AddToContext) {
  // Move up the scope chain until we find the nearest enclosing
  // non-transparent context. The declaration will be introduced into this
  // scope.
  while (S->getEntity() &&
         ((DeclContext *)S->getEntity())->isTransparentContext())
    S = S->getParent();

  // Add scoped declarations into their context, so that they can be
  // found later. Declarations without a context won't be inserted
  // into any context.
  if (AddToContext)
    CurContext->addDecl(D);

  // Out-of-line definitions shouldn't be pushed into scope in C++.
  // Out-of-line variable and function definitions shouldn't even in C.
  if ((getLangOpts().CPlusPlus || isa<VarDecl>(D) || isa<FunctionDecl>(D)) &&
      D->isOutOfLine() &&
      !D->getDeclContext()->getRedeclContext()->Equals(
        D->getLexicalDeclContext()->getRedeclContext()))
    return;

  // Template instantiations should also not be pushed into scope.
  if (isa<FunctionDecl>(D) &&
      cast<FunctionDecl>(D)->isFunctionTemplateSpecialization())
    return;

  // If this replaces anything in the current scope,
  IdentifierResolver::iterator I = IdResolver.begin(D->getDeclName()),
                               IEnd = IdResolver.end();
  for (; I != IEnd; ++I) {
    if (S->isDeclScope(*I) && D->declarationReplaces(*I)) {
      S->RemoveDecl(*I);
      IdResolver.RemoveDecl(*I);

      // Should only need to replace one decl.
      break;
    }
  }

  S->AddDecl(D);

  if (isa<LabelDecl>(D) && !cast<LabelDecl>(D)->isGnuLocal()) {
    // Implicitly-generated labels may end up getting generated in an order that
    // isn't strictly lexical, which breaks name lookup. Be careful to insert
    // the label at the appropriate place in the identifier chain.
    for (I = IdResolver.begin(D->getDeclName()); I != IEnd; ++I) {
      DeclContext *IDC = (*I)->getLexicalDeclContext()->getRedeclContext();
      if (IDC == CurContext) {
        if (!S->isDeclScope(*I))
          continue;
      } else if (IDC->Encloses(CurContext))
        break;
    }

    IdResolver.InsertDeclAfter(I, D);
  } else {
    IdResolver.AddDecl(D);
  }
}

void Sema::pushExternalDeclIntoScope(NamedDecl *D, DeclarationName Name) {
  if (IdResolver.tryAddTopLevelDecl(D, Name) && TUScope)
    TUScope->AddDecl(D);
}

bool Sema::isDeclInScope(NamedDecl *&D, DeclContext *Ctx, Scope *S,
                         bool ExplicitInstantiationOrSpecialization) {
  return IdResolver.isDeclInScope(D, Ctx, S,
                                  ExplicitInstantiationOrSpecialization);
}

Scope *Sema::getScopeForDeclContext(Scope *S, DeclContext *DC) {
  DeclContext *TargetDC = DC->getPrimaryContext();
  do {
    if (DeclContext *ScopeDC = (DeclContext*) S->getEntity())
      if (ScopeDC->getPrimaryContext() == TargetDC)
        return S;
  } while ((S = S->getParent()));

  return 0;
}

static bool isOutOfScopePreviousDeclaration(NamedDecl *,
                                            DeclContext*,
                                            ASTContext&);

/// Filters out lookup results that don't fall within the given scope
/// as determined by isDeclInScope.
void Sema::FilterLookupForScope(LookupResult &R,
                                DeclContext *Ctx, Scope *S,
                                bool ConsiderLinkage,
                                bool ExplicitInstantiationOrSpecialization) {
  LookupResult::Filter F = R.makeFilter();
  while (F.hasNext()) {
    NamedDecl *D = F.next();

    if (isDeclInScope(D, Ctx, S, ExplicitInstantiationOrSpecialization))
      continue;

    if (ConsiderLinkage &&
        isOutOfScopePreviousDeclaration(D, Ctx, Context))
      continue;

    F.erase();
  }

  F.done();
}

static bool isUsingDecl(NamedDecl *D) {
  return isa<UsingShadowDecl>(D) ||
         isa<UnresolvedUsingTypenameDecl>(D) ||
         isa<UnresolvedUsingValueDecl>(D);
}

/// Removes using shadow declarations from the lookup results.
static void RemoveUsingDecls(LookupResult &R) {
  LookupResult::Filter F = R.makeFilter();
  while (F.hasNext())
    if (isUsingDecl(F.next()))
      F.erase();

  F.done();
}

/// \brief Check for this common pattern:
/// @code
/// class S {
///   S(const S&); // DO NOT IMPLEMENT
///   void operator=(const S&); // DO NOT IMPLEMENT
/// };
/// @endcode
static bool IsDisallowedCopyOrAssign(const CXXMethodDecl *D) {
  // FIXME: Should check for private access too but access is set after we get
  // the decl here.
  if (D->doesThisDeclarationHaveABody())
    return false;

  if (const CXXConstructorDecl *CD = dyn_cast<CXXConstructorDecl>(D))
    return CD->isCopyConstructor();
  if (const CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(D))
    return Method->isCopyAssignmentOperator();
  return false;
}

// We need this to handle
//
// typedef struct {
//   void *foo() { return 0; }
// } A;
//
// When we see foo we don't know if after the typedef we will get 'A' or '*A'
// for example. If 'A', foo will have external linkage. If we have '*A',
// foo will have no linkage. Since we can't know untill we get to the end
// of the typedef, this function finds out if D might have non external linkage.
// Callers should verify at the end of the TU if it D has external linkage or
// not.
bool Sema::mightHaveNonExternalLinkage(const DeclaratorDecl *D) {
  const DeclContext *DC = D->getDeclContext();
  while (!DC->isTranslationUnit()) {
    if (const RecordDecl *RD = dyn_cast<RecordDecl>(DC)){
      if (!RD->hasNameForLinkage())
        return true;
    }
    DC = DC->getParent();
  }

  return !D->hasExternalLinkage();
}

bool Sema::ShouldWarnIfUnusedFileScopedDecl(const DeclaratorDecl *D) const {
  assert(D);

  if (D->isInvalidDecl() || D->isUsed() || D->hasAttr<UnusedAttr>())
    return false;

  // Ignore class templates.
  if (D->getDeclContext()->isDependentContext() ||
      D->getLexicalDeclContext()->isDependentContext())
    return false;

  if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
    if (FD->getTemplateSpecializationKind() == TSK_ImplicitInstantiation)
      return false;

    if (const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(FD)) {
      if (MD->isVirtual() || IsDisallowedCopyOrAssign(MD))
        return false;
    } else {
      // 'static inline' functions are used in headers; don't warn.
      if (FD->getStorageClass() == SC_Static &&
          FD->isInlineSpecified())
        return false;
    }

    if (FD->doesThisDeclarationHaveABody() &&
        Context.DeclMustBeEmitted(FD))
      return false;
  } else if (const VarDecl *VD = dyn_cast<VarDecl>(D)) {
    // Don't warn on variables of const-qualified or reference type, since their
    // values can be used even if though they're not odr-used, and because const
    // qualified variables can appear in headers in contexts where they're not
    // intended to be used.
    // FIXME: Use more principled rules for these exemptions.
    if (!VD->isFileVarDecl() ||
        VD->getType().isConstQualified() ||
        VD->getType()->isReferenceType() ||
        Context.DeclMustBeEmitted(VD))
      return false;

    if (VD->isStaticDataMember() &&
        VD->getTemplateSpecializationKind() == TSK_ImplicitInstantiation)
      return false;

  } else {
    return false;
  }

  // Only warn for unused decls internal to the translation unit.
  return mightHaveNonExternalLinkage(D);
}

void Sema::MarkUnusedFileScopedDecl(const DeclaratorDecl *D) {
  if (!D)
    return;

  if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
    const FunctionDecl *First = FD->getFirstDeclaration();
    if (FD != First && ShouldWarnIfUnusedFileScopedDecl(First))
      return; // First should already be in the vector.
  }

  if (const VarDecl *VD = dyn_cast<VarDecl>(D)) {
    const VarDecl *First = VD->getFirstDeclaration();
    if (VD != First && ShouldWarnIfUnusedFileScopedDecl(First))
      return; // First should already be in the vector.
  }

  if (ShouldWarnIfUnusedFileScopedDecl(D))
    UnusedFileScopedDecls.push_back(D);
}

static bool ShouldDiagnoseUnusedDecl(const NamedDecl *D) {
  if (D->isInvalidDecl())
    return false;

  if (D->isReferenced() || D->isUsed() || D->hasAttr<UnusedAttr>())
    return false;

  if (isa<LabelDecl>(D))
    return true;

  // White-list anything that isn't a local variable.
  if (!isa<VarDecl>(D) || isa<ParmVarDecl>(D) || isa<ImplicitParamDecl>(D) ||
      !D->getDeclContext()->isFunctionOrMethod())
    return false;

  // Types of valid local variables should be complete, so this should succeed.
  if (const VarDecl *VD = dyn_cast<VarDecl>(D)) {

    // White-list anything with an __attribute__((unused)) type.
    QualType Ty = VD->getType();

    // Only look at the outermost level of typedef.
    if (const TypedefType *TT = Ty->getAs<TypedefType>()) {
      if (TT->getDecl()->hasAttr<UnusedAttr>())
        return false;
    }

    // If we failed to complete the type for some reason, or if the type is
    // dependent, don't diagnose the variable.
    if (Ty->isIncompleteType() || Ty->isDependentType())
      return false;

    if (const TagType *TT = Ty->getAs<TagType>()) {
      const TagDecl *Tag = TT->getDecl();
      if (Tag->hasAttr<UnusedAttr>())
        return false;

      if (const CXXRecordDecl *RD = dyn_cast<CXXRecordDecl>(Tag)) {
        if (!RD->hasTrivialDestructor())
          return false;

        if (const Expr *Init = VD->getInit()) {
          if (const ExprWithCleanups *Cleanups = dyn_cast<ExprWithCleanups>(Init))
            Init = Cleanups->getSubExpr();
          const CXXConstructExpr *Construct =
            dyn_cast<CXXConstructExpr>(Init);
          if (Construct && !Construct->isElidable()) {
            CXXConstructorDecl *CD = Construct->getConstructor();
            if (!CD->isTrivial())
              return false;
          }
        }
      }
    }

    // TODO: __attribute__((unused)) templates?
  }

  return true;
}

static void GenerateFixForUnusedDecl(const NamedDecl *D, ASTContext &Ctx,
                                     FixItHint &Hint) {
  if (isa<LabelDecl>(D)) {
    SourceLocation AfterColon = Lexer::findLocationAfterToken(D->getLocEnd(),
                tok::colon, Ctx.getSourceManager(), Ctx.getLangOpts(), true);
    if (AfterColon.isInvalid())
      return;
    Hint = FixItHint::CreateRemoval(CharSourceRange::
                                    getCharRange(D->getLocStart(), AfterColon));
  }
  return;
}

/// DiagnoseUnusedDecl - Emit warnings about declarations that are not used
/// unless they are marked attr(unused).
void Sema::DiagnoseUnusedDecl(const NamedDecl *D) {
  FixItHint Hint;
  if (!ShouldDiagnoseUnusedDecl(D))
    return;

  GenerateFixForUnusedDecl(D, Context, Hint);

  unsigned DiagID;
  if (isa<VarDecl>(D) && cast<VarDecl>(D)->isExceptionVariable())
    DiagID = diag::warn_unused_exception_param;
  else if (isa<LabelDecl>(D))
    DiagID = diag::warn_unused_label;
  else
    DiagID = diag::warn_unused_variable;

  Diag(D->getLocation(), DiagID) << D->getDeclName() << Hint;
}

static void CheckPoppedLabel(LabelDecl *L, Sema &S) {
  // Verify that we have no forward references left.  If so, there was a goto
  // or address of a label taken, but no definition of it.  Label fwd
  // definitions are indicated with a null substmt.
  if (L->getStmt() == 0)
    S.Diag(L->getLocation(), diag::err_undeclared_label_use) <<L->getDeclName();
}

void Sema::ActOnPopScope(SourceLocation Loc, Scope *S) {
  if (S->decl_empty()) return;
  assert((S->getFlags() & (Scope::DeclScope | Scope::TemplateParamScope)) &&
         "Scope shouldn't contain decls!");

  for (Scope::decl_iterator I = S->decl_begin(), E = S->decl_end();
       I != E; ++I) {
    Decl *TmpD = (*I);
    assert(TmpD && "This decl didn't get pushed??");

    assert(isa<NamedDecl>(TmpD) && "Decl isn't NamedDecl?");
    NamedDecl *D = cast<NamedDecl>(TmpD);

    if (!D->getDeclName()) continue;

    // Diagnose unused variables in this scope.
    if (!S->hasErrorOccurred())
      DiagnoseUnusedDecl(D);

    // If this was a forward reference to a label, verify it was defined.
    if (LabelDecl *LD = dyn_cast<LabelDecl>(D))
      CheckPoppedLabel(LD, *this);

    // Remove this name from our lexical scope.
    IdResolver.RemoveDecl(D);
  }
}

void Sema::ActOnStartFunctionDeclarator() {
  ++InFunctionDeclarator;
}

void Sema::ActOnEndFunctionDeclarator() {
  assert(InFunctionDeclarator);
  --InFunctionDeclarator;
}

/// \brief Look for an Objective-C class in the translation unit.
///
/// \param Id The name of the Objective-C class we're looking for. If
/// typo-correction fixes this name, the Id will be updated
/// to the fixed name.
///
/// \param IdLoc The location of the name in the translation unit.
///
/// \param DoTypoCorrection If true, this routine will attempt typo correction
/// if there is no class with the given name.
///
/// \returns The declaration of the named Objective-C class, or NULL if the
/// class could not be found.
ObjCInterfaceDecl *Sema::getObjCInterfaceDecl(IdentifierInfo *&Id,
                                              SourceLocation IdLoc,
                                              bool DoTypoCorrection) {
  // The third "scope" argument is 0 since we aren't enabling lazy built-in
  // creation from this context.
  NamedDecl *IDecl = LookupSingleName(TUScope, Id, IdLoc, LookupOrdinaryName);

  if (!IDecl && DoTypoCorrection) {
    // Perform typo correction at the given location, but only if we
    // find an Objective-C class name.
    DeclFilterCCC<ObjCInterfaceDecl> Validator;
    if (TypoCorrection C = CorrectTypo(DeclarationNameInfo(Id, IdLoc),
                                       LookupOrdinaryName, TUScope, NULL,
                                       Validator)) {
      IDecl = C.getCorrectionDeclAs<ObjCInterfaceDecl>();
      Diag(IdLoc, diag::err_undef_interface_suggest)
        << Id << IDecl->getDeclName()
        << FixItHint::CreateReplacement(IdLoc, IDecl->getNameAsString());
      Diag(IDecl->getLocation(), diag::note_previous_decl)
        << IDecl->getDeclName();

      Id = IDecl->getIdentifier();
    }
  }
  ObjCInterfaceDecl *Def = dyn_cast_or_null<ObjCInterfaceDecl>(IDecl);
  // This routine must always return a class definition, if any.
  if (Def && Def->getDefinition())
      Def = Def->getDefinition();
  return Def;
}

/// getNonFieldDeclScope - Retrieves the innermost scope, starting
/// from S, where a non-field would be declared. This routine copes
/// with the difference between C and C++ scoping rules in structs and
/// unions. For example, the following code is well-formed in C but
/// ill-formed in C++:
/// @code
/// struct S6 {
///   enum { BAR } e;
/// };
///
/// void test_S6() {
///   struct S6 a;
///   a.e = BAR;
/// }
/// @endcode
/// For the declaration of BAR, this routine will return a different
/// scope. The scope S will be the scope of the unnamed enumeration
/// within S6. In C++, this routine will return the scope associated
/// with S6, because the enumeration's scope is a transparent
/// context but structures can contain non-field names. In C, this
/// routine will return the translation unit scope, since the
/// enumeration's scope is a transparent context and structures cannot
/// contain non-field names.
Scope *Sema::getNonFieldDeclScope(Scope *S) {
  while (((S->getFlags() & Scope::DeclScope) == 0) ||
         (S->getEntity() &&
          ((DeclContext *)S->getEntity())->isTransparentContext()) ||
         (S->isClassScope() && !getLangOpts().CPlusPlus))
    S = S->getParent();
  return S;
}

/// \brief Looks up the declaration of "struct objc_super" and
/// saves it for later use in building builtin declaration of
/// objc_msgSendSuper and objc_msgSendSuper_stret. If no such
/// pre-existing declaration exists no action takes place.
static void LookupPredefedObjCSuperType(Sema &ThisSema, Scope *S,
                                        IdentifierInfo *II) {
  if (!II->isStr("objc_msgSendSuper"))
    return;
  ASTContext &Context = ThisSema.Context;

  LookupResult Result(ThisSema, &Context.Idents.get("objc_super"),
                      SourceLocation(), Sema::LookupTagName);
  ThisSema.LookupName(Result, S);
  if (Result.getResultKind() == LookupResult::Found)
    if (const TagDecl *TD = Result.getAsSingle<TagDecl>())
      Context.setObjCSuperType(Context.getTagDeclType(TD));
}

/// LazilyCreateBuiltin - The specified Builtin-ID was first used at
/// file scope.  lazily create a decl for it. ForRedeclaration is true
/// if we're creating this built-in in anticipation of redeclaring the
/// built-in.
NamedDecl *Sema::LazilyCreateBuiltin(IdentifierInfo *II, unsigned bid,
                                     Scope *S, bool ForRedeclaration,
                                     SourceLocation Loc) {
  LookupPredefedObjCSuperType(*this, S, II);

  Builtin::ID BID = (Builtin::ID)bid;

  ASTContext::GetBuiltinTypeError Error;
  QualType R = Context.GetBuiltinType(BID, Error);
  switch (Error) {
  case ASTContext::GE_None:
    // Okay
    break;

  case ASTContext::GE_Missing_stdio:
    if (ForRedeclaration)
      Diag(Loc, diag::warn_implicit_decl_requires_stdio)
        << Context.BuiltinInfo.GetName(BID);
    return 0;

  case ASTContext::GE_Missing_setjmp:
    if (ForRedeclaration)
      Diag(Loc, diag::warn_implicit_decl_requires_setjmp)
        << Context.BuiltinInfo.GetName(BID);
    return 0;

  case ASTContext::GE_Missing_ucontext:
    if (ForRedeclaration)
      Diag(Loc, diag::warn_implicit_decl_requires_ucontext)
        << Context.BuiltinInfo.GetName(BID);
    return 0;
  }

  if (!ForRedeclaration && Context.BuiltinInfo.isPredefinedLibFunction(BID)) {
    Diag(Loc, diag::ext_implicit_lib_function_decl)
      << Context.BuiltinInfo.GetName(BID)
      << R;
    if (Context.BuiltinInfo.getHeaderName(BID) &&
        Diags.getDiagnosticLevel(diag::ext_implicit_lib_function_decl, Loc)
          != DiagnosticsEngine::Ignored)
      Diag(Loc, diag::note_please_include_header)
        << Context.BuiltinInfo.getHeaderName(BID)
        << Context.BuiltinInfo.GetName(BID);
  }

  FunctionDecl *New = FunctionDecl::Create(Context,
                                           Context.getTranslationUnitDecl(),
                                           Loc, Loc, II, R, /*TInfo=*/0,
                                           SC_Extern,
                                           SC_None, false,
                                           /*hasPrototype=*/true);
  New->setImplicit();

  // Create Decl objects for each parameter, adding them to the
  // FunctionDecl.
  if (const FunctionProtoType *FT = dyn_cast<FunctionProtoType>(R)) {
    SmallVector<ParmVarDecl*, 16> Params;
    for (unsigned i = 0, e = FT->getNumArgs(); i != e; ++i) {
      ParmVarDecl *parm =
        ParmVarDecl::Create(Context, New, SourceLocation(),
                            SourceLocation(), 0,
                            FT->getArgType(i), /*TInfo=*/0,
                            SC_None, SC_None, 0);
      parm->setScopeInfo(0, i);
      Params.push_back(parm);
    }
    New->setParams(Params);
  }

  AddKnownFunctionAttributes(New);

  // TUScope is the translation-unit scope to insert this function into.
  // FIXME: This is hideous. We need to teach PushOnScopeChains to
  // relate Scopes to DeclContexts, and probably eliminate CurContext
  // entirely, but we're not there yet.
  DeclContext *SavedContext = CurContext;
  CurContext = Context.getTranslationUnitDecl();
  PushOnScopeChains(New, TUScope);
  CurContext = SavedContext;
  return New;
}

/// \brief Filter out any previous declarations that the given declaration
/// should not consider because they are not permitted to conflict, e.g.,
/// because they come from hidden sub-modules and do not refer to the same
/// entity.
static void filterNonConflictingPreviousDecls(ASTContext &context,
                                              NamedDecl *decl,
                                              LookupResult &previous){
  // This is only interesting when modules are enabled.
  if (!context.getLangOpts().Modules)
    return;

  // Empty sets are uninteresting.
  if (previous.empty())
    return;

  // If this declaration has external
  bool hasExternalLinkage = decl->hasExternalLinkage();

  LookupResult::Filter filter = previous.makeFilter();
  while (filter.hasNext()) {
    NamedDecl *old = filter.next();

    // Non-hidden declarations are never ignored.
    if (!old->isHidden())
      continue;

    // If either has no-external linkage, ignore the old declaration.
    if (!hasExternalLinkage || old->getLinkage() != ExternalLinkage)
      filter.erase();
  }

  filter.done();
}

bool Sema::isIncompatibleTypedef(TypeDecl *Old, TypedefNameDecl *New) {
  QualType OldType;
  if (TypedefNameDecl *OldTypedef = dyn_cast<TypedefNameDecl>(Old))
    OldType = OldTypedef->getUnderlyingType();
  else
    OldType = Context.getTypeDeclType(Old);
  QualType NewType = New->getUnderlyingType();

  if (NewType->isVariablyModifiedType()) {
    // Must not redefine a typedef with a variably-modified type.
    int Kind = isa<TypeAliasDecl>(Old) ? 1 : 0;
    Diag(New->getLocation(), diag::err_redefinition_variably_modified_typedef)
      << Kind << NewType;
    if (Old->getLocation().isValid())
      Diag(Old->getLocation(), diag::note_previous_definition);
    New->setInvalidDecl();
    return true;
  }

  if (OldType != NewType &&
      !OldType->isDependentType() &&
      !NewType->isDependentType() &&
      !Context.hasSameType(OldType, NewType)) {
    int Kind = isa<TypeAliasDecl>(Old) ? 1 : 0;
    Diag(New->getLocation(), diag::err_redefinition_different_typedef)
      << Kind << NewType << OldType;
    if (Old->getLocation().isValid())
      Diag(Old->getLocation(), diag::note_previous_definition);
    New->setInvalidDecl();
    return true;
  }
  return false;
}

/// MergeTypedefNameDecl - We just parsed a typedef '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. If there was an error, set New to be invalid.
///
void Sema::MergeTypedefNameDecl(TypedefNameDecl *New, LookupResult &OldDecls) {
  // If the new decl is known invalid already, don't bother doing any
  // merging checks.
  if (New->isInvalidDecl()) return;

  // Allow multiple definitions for ObjC built-in typedefs.
  // FIXME: Verify the underlying types are equivalent!
  if (getLangOpts().ObjC1) {
    const IdentifierInfo *TypeID = New->getIdentifier();
    switch (TypeID->getLength()) {
    default: break;
    case 2:
      {
        if (!TypeID->isStr("id"))
          break;
        QualType T = New->getUnderlyingType();
        if (!T->isPointerType())
          break;
        if (!T->isVoidPointerType()) {
          QualType PT = T->getAs<PointerType>()->getPointeeType();
          if (!PT->isStructureType())
            break;
        }
        Context.setObjCIdRedefinitionType(T);
        // Install the built-in type for 'id', ignoring the current definition.
        New->setTypeForDecl(Context.getObjCIdType().getTypePtr());
        return;
      }
    case 5:
      if (!TypeID->isStr("Class"))
        break;
      Context.setObjCClassRedefinitionType(New->getUnderlyingType());
      // Install the built-in type for 'Class', ignoring the current definition.
      New->setTypeForDecl(Context.getObjCClassType().getTypePtr());
      return;
    case 3:
      if (!TypeID->isStr("SEL"))
        break;
      Context.setObjCSelRedefinitionType(New->getUnderlyingType());
      // Install the built-in type for 'SEL', ignoring the current definition.
      New->setTypeForDecl(Context.getObjCSelType().getTypePtr());
      return;
    }
    // Fall through - the typedef name was not a builtin type.
  }

  // Verify the old decl was also a type.
  TypeDecl *Old = OldDecls.getAsSingle<TypeDecl>();
  if (!Old) {
    Diag(New->getLocation(), diag::err_redefinition_different_kind)
      << New->getDeclName();

    NamedDecl *OldD = OldDecls.getRepresentativeDecl();
    if (OldD->getLocation().isValid())
      Diag(OldD->getLocation(), diag::note_previous_definition);

    return New->setInvalidDecl();
  }

  // If the old declaration is invalid, just give up here.
  if (Old->isInvalidDecl())
    return New->setInvalidDecl();

  // If the typedef types are not identical, reject them in all languages and
  // with any extensions enabled.
  if (isIncompatibleTypedef(Old, New))
    return;

  // The types match.  Link up the redeclaration chain if the old
  // declaration was a typedef.
  if (TypedefNameDecl *Typedef = dyn_cast<TypedefNameDecl>(Old))
    New->setPreviousDeclaration(Typedef);

  if (getLangOpts().MicrosoftExt)
    return;

  if (getLangOpts().CPlusPlus) {
    // C++ [dcl.typedef]p2:
    //   In a given non-class scope, a typedef specifier can be used to
    //   redefine the name of any type declared in that scope to refer
    //   to the type to which it already refers.
    if (!isa<CXXRecordDecl>(CurContext))
      return;

    // C++0x [dcl.typedef]p4:
    //   In a given class scope, a typedef specifier can be used to redefine
    //   any class-name declared in that scope that is not also a typedef-name
    //   to refer to the type to which it already refers.
    //
    // This wording came in via DR424, which was a correction to the
    // wording in DR56, which accidentally banned code like:
    //
    //   struct S {
    //     typedef struct A { } A;
    //   };
    //
    // in the C++03 standard. We implement the C++0x semantics, which
    // allow the above but disallow
    //
    //   struct S {
    //     typedef int I;
    //     typedef int I;
    //   };
    //
    // since that was the intent of DR56.
    if (!isa<TypedefNameDecl>(Old))
      return;

    Diag(New->getLocation(), diag::err_redefinition)
      << New->getDeclName();
    Diag(Old->getLocation(), diag::note_previous_definition);
    return New->setInvalidDecl();
  }

  // Modules always permit redefinition of typedefs, as does C11.
  if (getLangOpts().Modules || getLangOpts().C11)
    return;

  // If we have a redefinition of a typedef in C, emit a warning.  This warning
  // is normally mapped to an error, but can be controlled with
  // -Wtypedef-redefinition.  If either the original or the redefinition is
  // in a system header, don't emit this for compatibility with GCC.
  if (getDiagnostics().getSuppressSystemWarnings() &&
      (Context.getSourceManager().isInSystemHeader(Old->getLocation()) ||
       Context.getSourceManager().isInSystemHeader(New->getLocation())))
    return;

  Diag(New->getLocation(), diag::warn_redefinition_of_typedef)
    << New->getDeclName();
  Diag(Old->getLocation(), diag::note_previous_definition);
  return;
}

/// DeclhasAttr - returns true if decl Declaration already has the target
/// attribute.
static bool
DeclHasAttr(const Decl *D, const Attr *A) {
  // There can be multiple AvailabilityAttr in a Decl. Make sure we copy
  // all of them. It is mergeAvailabilityAttr in SemaDeclAttr.cpp that is
  // responsible for making sure they are consistent.
  const AvailabilityAttr *AA = dyn_cast<AvailabilityAttr>(A);
  if (AA)
    return false;

  // The following thread safety attributes can also be duplicated.
  switch (A->getKind()) {
    case attr::ExclusiveLocksRequired:
    case attr::SharedLocksRequired:
    case attr::LocksExcluded:
    case attr::ExclusiveLockFunction:
    case attr::SharedLockFunction:
    case attr::UnlockFunction:
    case attr::ExclusiveTrylockFunction:
    case attr::SharedTrylockFunction:
    case attr::GuardedBy:
    case attr::PtGuardedBy:
    case attr::AcquiredBefore:
    case attr::AcquiredAfter:
      return false;
    default:
      ;
  }

  const OwnershipAttr *OA = dyn_cast<OwnershipAttr>(A);
  const AnnotateAttr *Ann = dyn_cast<AnnotateAttr>(A);
  for (Decl::attr_iterator i = D->attr_begin(), e = D->attr_end(); i != e; ++i)
    if ((*i)->getKind() == A->getKind()) {
      if (Ann) {
        if (Ann->getAnnotation() == cast<AnnotateAttr>(*i)->getAnnotation())
          return true;
        continue;
      }
      // FIXME: Don't hardcode this check
      if (OA && isa<OwnershipAttr>(*i))
        return OA->getOwnKind() == cast<OwnershipAttr>(*i)->getOwnKind();
      return true;
    }

  return false;
}

static bool isAttributeTargetADefinition(Decl *D) {
  if (VarDecl *VD = dyn_cast<VarDecl>(D))
    return VD->isThisDeclarationADefinition();
  if (TagDecl *TD = dyn_cast<TagDecl>(D))
    return TD->isCompleteDefinition() || TD->isBeingDefined();
  return true;
}

/// Merge alignment attributes from \p Old to \p New, taking into account the
/// special semantics of C11's _Alignas specifier and C++11's alignas attribute.
///
/// \return \c true if any attributes were added to \p New.
static bool mergeAlignedAttrs(Sema &S, NamedDecl *New, Decl *Old) {
  // Look for alignas attributes on Old, and pick out whichever attribute
  // specifies the strictest alignment requirement.
  AlignedAttr *OldAlignasAttr = 0;
  AlignedAttr *OldStrictestAlignAttr = 0;
  unsigned OldAlign = 0;
  for (specific_attr_iterator<AlignedAttr>
         I = Old->specific_attr_begin<AlignedAttr>(),
         E = Old->specific_attr_end<AlignedAttr>(); I != E; ++I) {
    // FIXME: We have no way of representing inherited dependent alignments
    // in a case like:
    //   template<int A, int B> struct alignas(A) X;
    //   template<int A, int B> struct alignas(B) X {};
    // For now, we just ignore any alignas attributes which are not on the
    // definition in such a case.
    if (I->isAlignmentDependent())
      return false;

    if (I->isAlignas())
      OldAlignasAttr = *I;

    unsigned Align = I->getAlignment(S.Context);
    if (Align > OldAlign) {
      OldAlign = Align;
      OldStrictestAlignAttr = *I;
    }
  }

  // Look for alignas attributes on New.
  AlignedAttr *NewAlignasAttr = 0;
  unsigned NewAlign = 0;
  for (specific_attr_iterator<AlignedAttr>
         I = New->specific_attr_begin<AlignedAttr>(),
         E = New->specific_attr_end<AlignedAttr>(); I != E; ++I) {
    if (I->isAlignmentDependent())
      return false;

    if (I->isAlignas())
      NewAlignasAttr = *I;

    unsigned Align = I->getAlignment(S.Context);
    if (Align > NewAlign)
      NewAlign = Align;
  }

  if (OldAlignasAttr && NewAlignasAttr && OldAlign != NewAlign) {
    // Both declarations have 'alignas' attributes. We require them to match.
    // C++11 [dcl.align]p6 and C11 6.7.5/7 both come close to saying this, but
    // fall short. (If two declarations both have alignas, they must both match
    // every definition, and so must match each other if there is a definition.)

    // If either declaration only contains 'alignas(0)' specifiers, then it
    // specifies the natural alignment for the type.
    if (OldAlign == 0 || NewAlign == 0) {
      QualType Ty;
      if (ValueDecl *VD = dyn_cast<ValueDecl>(New))
        Ty = VD->getType();
      else
        Ty = S.Context.getTagDeclType(cast<TagDecl>(New));

      if (OldAlign == 0)
        OldAlign = S.Context.getTypeAlign(Ty);
      if (NewAlign == 0)
        NewAlign = S.Context.getTypeAlign(Ty);
    }

    if (OldAlign != NewAlign) {
      S.Diag(NewAlignasAttr->getLocation(), diag::err_alignas_mismatch)
        << (unsigned)S.Context.toCharUnitsFromBits(OldAlign).getQuantity()
        << (unsigned)S.Context.toCharUnitsFromBits(NewAlign).getQuantity();
      S.Diag(OldAlignasAttr->getLocation(), diag::note_previous_declaration);
    }
  }

  if (OldAlignasAttr && !NewAlignasAttr && isAttributeTargetADefinition(New)) {
    // C++11 [dcl.align]p6:
    //   if any declaration of an entity has an alignment-specifier,
    //   every defining declaration of that entity shall specify an
    //   equivalent alignment.
    // C11 6.7.5/7:
    //   If the definition of an object does not have an alignment
    //   specifier, any other declaration of that object shall also
    //   have no alignment specifier.
    S.Diag(New->getLocation(), diag::err_alignas_missing_on_definition)
      << OldAlignasAttr->isC11();
    S.Diag(OldAlignasAttr->getLocation(), diag::note_alignas_on_declaration)
      << OldAlignasAttr->isC11();
  }

  bool AnyAdded = false;

  // Ensure we have an attribute representing the strictest alignment.
  if (OldAlign > NewAlign) {
    AlignedAttr *Clone = OldStrictestAlignAttr->clone(S.Context);
    Clone->setInherited(true);
    New->addAttr(Clone);
    AnyAdded = true;
  }

  // Ensure we have an alignas attribute if the old declaration had one.
  if (OldAlignasAttr && !NewAlignasAttr &&
      !(AnyAdded && OldStrictestAlignAttr->isAlignas())) {
    AlignedAttr *Clone = OldAlignasAttr->clone(S.Context);
    Clone->setInherited(true);
    New->addAttr(Clone);
    AnyAdded = true;
  }

  return AnyAdded;
}

static bool mergeDeclAttribute(Sema &S, NamedDecl *D, InheritableAttr *Attr,
                               bool Override) {
  InheritableAttr *NewAttr = NULL;
  unsigned AttrSpellingListIndex = Attr->getSpellingListIndex();
  if (AvailabilityAttr *AA = dyn_cast<AvailabilityAttr>(Attr))
    NewAttr = S.mergeAvailabilityAttr(D, AA->getRange(), AA->getPlatform(),
                                      AA->getIntroduced(), AA->getDeprecated(),
                                      AA->getObsoleted(), AA->getUnavailable(),
                                      AA->getMessage(), Override,
                                      AttrSpellingListIndex);
  else if (VisibilityAttr *VA = dyn_cast<VisibilityAttr>(Attr))
    NewAttr = S.mergeVisibilityAttr(D, VA->getRange(), VA->getVisibility(),
                                    AttrSpellingListIndex);
  else if (TypeVisibilityAttr *VA = dyn_cast<TypeVisibilityAttr>(Attr))
    NewAttr = S.mergeTypeVisibilityAttr(D, VA->getRange(), VA->getVisibility(),
                                        AttrSpellingListIndex);
  else if (DLLImportAttr *ImportA = dyn_cast<DLLImportAttr>(Attr))
    NewAttr = S.mergeDLLImportAttr(D, ImportA->getRange(),
                                   AttrSpellingListIndex);
  else if (DLLExportAttr *ExportA = dyn_cast<DLLExportAttr>(Attr))
    NewAttr = S.mergeDLLExportAttr(D, ExportA->getRange(),
                                   AttrSpellingListIndex);
  else if (FormatAttr *FA = dyn_cast<FormatAttr>(Attr))
    NewAttr = S.mergeFormatAttr(D, FA->getRange(), FA->getType(),
                                FA->getFormatIdx(), FA->getFirstArg(),
                                AttrSpellingListIndex);
  else if (SectionAttr *SA = dyn_cast<SectionAttr>(Attr))
    NewAttr = S.mergeSectionAttr(D, SA->getRange(), SA->getName(),
                                 AttrSpellingListIndex);
  else if (isa<AlignedAttr>(Attr))
    // AlignedAttrs are handled separately, because we need to handle all
    // such attributes on a declaration at the same time.
    NewAttr = 0;
  else if (!DeclHasAttr(D, Attr))
    NewAttr = cast<InheritableAttr>(Attr->clone(S.Context));

  if (NewAttr) {
    NewAttr->setInherited(true);
    D->addAttr(NewAttr);
    return true;
  }

  return false;
}

static const Decl *getDefinition(const Decl *D) {
  if (const TagDecl *TD = dyn_cast<TagDecl>(D))
    return TD->getDefinition();
  if (const VarDecl *VD = dyn_cast<VarDecl>(D))
    return VD->getDefinition();
  if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
    const FunctionDecl* Def;
    if (FD->hasBody(Def))
      return Def;
  }
  return NULL;
}

static bool hasAttribute(const Decl *D, attr::Kind Kind) {
  for (Decl::attr_iterator I = D->attr_begin(), E = D->attr_end();
       I != E; ++I) {
    Attr *Attribute = *I;
    if (Attribute->getKind() == Kind)
      return true;
  }
  return false;
}

/// checkNewAttributesAfterDef - If we already have a definition, check that
/// there are no new attributes in this declaration.
static void checkNewAttributesAfterDef(Sema &S, Decl *New, const Decl *Old) {
  if (!New->hasAttrs())
    return;

  const Decl *Def = getDefinition(Old);
  if (!Def || Def == New)
    return;

  AttrVec &NewAttributes = New->getAttrs();
  for (unsigned I = 0, E = NewAttributes.size(); I != E;) {
    const Attr *NewAttribute = NewAttributes[I];
    if (hasAttribute(Def, NewAttribute->getKind())) {
      ++I;
      continue; // regular attr merging will take care of validating this.
    }

    if (isa<C11NoReturnAttr>(NewAttribute)) {
      // C's _Noreturn is allowed to be added to a function after it is defined.
      ++I;
      continue;
    } else if (const AlignedAttr *AA = dyn_cast<AlignedAttr>(NewAttribute)) {
      if (AA->isAlignas()) {
        // C++11 [dcl.align]p6:
        //   if any declaration of an entity has an alignment-specifier,
        //   every defining declaration of that entity shall specify an
        //   equivalent alignment.
        // C11 6.7.5/7:
        //   If the definition of an object does not have an alignment
        //   specifier, any other declaration of that object shall also
        //   have no alignment specifier.
        S.Diag(Def->getLocation(), diag::err_alignas_missing_on_definition)
          << AA->isC11();
        S.Diag(NewAttribute->getLocation(), diag::note_alignas_on_declaration)
          << AA->isC11();
        NewAttributes.erase(NewAttributes.begin() + I);
        --E;
        continue;
      }
    }

    S.Diag(NewAttribute->getLocation(),
           diag::warn_attribute_precede_definition);
    S.Diag(Def->getLocation(), diag::note_previous_definition);
    NewAttributes.erase(NewAttributes.begin() + I);
    --E;
  }
}

/// mergeDeclAttributes - Copy attributes from the Old decl to the New one.
void Sema::mergeDeclAttributes(NamedDecl *New, Decl *Old,
                               AvailabilityMergeKind AMK) {
  if (!Old->hasAttrs() && !New->hasAttrs())
    return;

  // attributes declared post-definition are currently ignored
  checkNewAttributesAfterDef(*this, New, Old);

  if (!Old->hasAttrs())
    return;

  bool foundAny = New->hasAttrs();

  // Ensure that any moving of objects within the allocated map is done before
  // we process them.
  if (!foundAny) New->setAttrs(AttrVec());

  for (specific_attr_iterator<InheritableAttr>
         i = Old->specific_attr_begin<InheritableAttr>(),
         e = Old->specific_attr_end<InheritableAttr>();
       i != e; ++i) {
    bool Override = false;
    // Ignore deprecated/unavailable/availability attributes if requested.
    if (isa<DeprecatedAttr>(*i) ||
        isa<UnavailableAttr>(*i) ||
        isa<AvailabilityAttr>(*i)) {
      switch (AMK) {
      case AMK_None:
        continue;

      case AMK_Redeclaration:
        break;

      case AMK_Override:
        Override = true;
        break;
      }
    }

    if (mergeDeclAttribute(*this, New, *i, Override))
      foundAny = true;
  }

  if (mergeAlignedAttrs(*this, New, Old))
    foundAny = true;

  if (!foundAny) New->dropAttrs();
}

/// mergeParamDeclAttributes - Copy attributes from the old parameter
/// to the new one.
static void mergeParamDeclAttributes(ParmVarDecl *newDecl,
                                     const ParmVarDecl *oldDecl,
                                     Sema &S) {
  // C++11 [dcl.attr.depend]p2:
  //   The first declaration of a function shall specify the
  //   carries_dependency attribute for its declarator-id if any declaration
  //   of the function specifies the carries_dependency attribute.
  if (newDecl->hasAttr<CarriesDependencyAttr>() &&
      !oldDecl->hasAttr<CarriesDependencyAttr>()) {
    S.Diag(newDecl->getAttr<CarriesDependencyAttr>()->getLocation(),
           diag::err_carries_dependency_missing_on_first_decl) << 1/*Param*/;
    // Find the first declaration of the parameter.
    // FIXME: Should we build redeclaration chains for function parameters?
    const FunctionDecl *FirstFD =
      cast<FunctionDecl>(oldDecl->getDeclContext())->getFirstDeclaration();
    const ParmVarDecl *FirstVD =
      FirstFD->getParamDecl(oldDecl->getFunctionScopeIndex());
    S.Diag(FirstVD->getLocation(),
           diag::note_carries_dependency_missing_first_decl) << 1/*Param*/;
  }

  if (!oldDecl->hasAttrs())
    return;

  bool foundAny = newDecl->hasAttrs();

  // Ensure that any moving of objects within the allocated map is
  // done before we process them.
  if (!foundAny) newDecl->setAttrs(AttrVec());

  for (specific_attr_iterator<InheritableParamAttr>
       i = oldDecl->specific_attr_begin<InheritableParamAttr>(),
       e = oldDecl->specific_attr_end<InheritableParamAttr>(); i != e; ++i) {
    if (!DeclHasAttr(newDecl, *i)) {
      InheritableAttr *newAttr =
        cast<InheritableParamAttr>((*i)->clone(S.Context));
      newAttr->setInherited(true);
      newDecl->addAttr(newAttr);
      foundAny = true;
    }
  }

  if (!foundAny) newDecl->dropAttrs();
}

namespace {

/// Used in MergeFunctionDecl to keep track of function parameters in
/// C.
struct GNUCompatibleParamWarning {
  ParmVarDecl *OldParm;
  ParmVarDecl *NewParm;
  QualType PromotedType;
};

}

/// getSpecialMember - get the special member enum for a method.
Sema::CXXSpecialMember Sema::getSpecialMember(const CXXMethodDecl *MD) {
  if (const CXXConstructorDecl *Ctor = dyn_cast<CXXConstructorDecl>(MD)) {
    if (Ctor->isDefaultConstructor())
      return Sema::CXXDefaultConstructor;

    if (Ctor->isCopyConstructor())
      return Sema::CXXCopyConstructor;

    if (Ctor->isMoveConstructor())
      return Sema::CXXMoveConstructor;
  } else if (isa<CXXDestructorDecl>(MD)) {
    return Sema::CXXDestructor;
  } else if (MD->isCopyAssignmentOperator()) {
    return Sema::CXXCopyAssignment;
  } else if (MD->isMoveAssignmentOperator()) {
    return Sema::CXXMoveAssignment;
  }

  return Sema::CXXInvalid;
}

/// canRedefineFunction - checks if a function can be redefined. Currently,
/// only extern inline functions can be redefined, and even then only in
/// GNU89 mode.
static bool canRedefineFunction(const FunctionDecl *FD,
                                const LangOptions& LangOpts) {
  return ((FD->hasAttr<GNUInlineAttr>() || LangOpts.GNUInline) &&
          !LangOpts.CPlusPlus &&
          FD->isInlineSpecified() &&
          FD->getStorageClass() == SC_Extern);
}

/// Is the given calling convention the ABI default for the given
/// declaration?
static bool isABIDefaultCC(Sema &S, CallingConv CC, FunctionDecl *D) {
  CallingConv ABIDefaultCC;
  if (isa<CXXMethodDecl>(D) && cast<CXXMethodDecl>(D)->isInstance()) {
    ABIDefaultCC = S.Context.getDefaultCXXMethodCallConv(D->isVariadic());
  } else {
    // Free C function or a static method.
    ABIDefaultCC = (S.Context.getLangOpts().MRTD ? CC_X86StdCall : CC_C);
  }
  return ABIDefaultCC == CC;
}

template <typename T>
static bool haveIncompatibleLanguageLinkages(const T *Old, const T *New) {
  const DeclContext *DC = Old->getDeclContext();
  if (DC->isRecord())
    return false;

  LanguageLinkage OldLinkage = Old->getLanguageLinkage();
  if (OldLinkage == CXXLanguageLinkage &&
      New->getDeclContext()->isExternCContext())
    return true;
  if (OldLinkage == CLanguageLinkage &&
      New->getDeclContext()->isExternCXXContext())
    return true;
  return false;
}

/// MergeFunctionDecl - We just parsed a function 'New' from
/// declarator D 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.
///
/// In C++, New and Old must be declarations that are not
/// overloaded. Use IsOverload to determine whether New and Old are
/// overloaded, and to select the Old declaration that New should be
/// merged with.
///
/// Returns true if there was an error, false otherwise.
bool Sema::MergeFunctionDecl(FunctionDecl *New, Decl *OldD, Scope *S) {
  // Verify the old decl was also a function.
  FunctionDecl *Old = 0;
  if (FunctionTemplateDecl *OldFunctionTemplate
        = dyn_cast<FunctionTemplateDecl>(OldD))
    Old = OldFunctionTemplate->getTemplatedDecl();
  else
    Old = dyn_cast<FunctionDecl>(OldD);
  if (!Old) {
    if (UsingShadowDecl *Shadow = dyn_cast<UsingShadowDecl>(OldD)) {
      Diag(New->getLocation(), diag::err_using_decl_conflict_reverse);
      Diag(Shadow->getTargetDecl()->getLocation(),
           diag::note_using_decl_target);
      Diag(Shadow->getUsingDecl()->getLocation(),
           diag::note_using_decl) << 0;
      return true;
    }

    Diag(New->getLocation(), diag::err_redefinition_different_kind)
      << New->getDeclName();
    Diag(OldD->getLocation(), diag::note_previous_definition);
    return true;
  }

  // Determine whether the previous declaration was a definition,
  // implicit declaration, or a declaration.
  diag::kind PrevDiag;
  if (Old->isThisDeclarationADefinition())
    PrevDiag = diag::note_previous_definition;
  else if (Old->isImplicit())
    PrevDiag = diag::note_previous_implicit_declaration;
  else
    PrevDiag = diag::note_previous_declaration;

  QualType OldQType = Context.getCanonicalType(Old->getType());
  QualType NewQType = Context.getCanonicalType(New->getType());

  // Don't complain about this if we're in GNU89 mode and the old function
  // is an extern inline function.
  if (!isa<CXXMethodDecl>(New) && !isa<CXXMethodDecl>(Old) &&
      New->getStorageClass() == SC_Static &&
      Old->getStorageClass() != SC_Static &&
      !canRedefineFunction(Old, getLangOpts())) {
    if (getLangOpts().MicrosoftExt) {
      Diag(New->getLocation(), diag::warn_static_non_static) << New;
      Diag(Old->getLocation(), PrevDiag);
    } else {
      Diag(New->getLocation(), diag::err_static_non_static) << New;
      Diag(Old->getLocation(), PrevDiag);
      return true;
    }
  }

  // If a function is first declared with a calling convention, but is
  // later declared or defined without one, the second decl assumes the
  // calling convention of the first.
  //
  // It's OK if a function is first declared without a calling convention,
  // but is later declared or defined with the default calling convention.
  //
  // For the new decl, we have to look at the NON-canonical type to tell the
  // difference between a function that really doesn't have a calling
  // convention and one that is declared cdecl. That's because in
  // canonicalization (see ASTContext.cpp), cdecl is canonicalized away
  // because it is the default calling convention.
  //
  // Note also that we DO NOT return at this point, because we still have
  // other tests to run.
  const FunctionType *OldType = cast<FunctionType>(OldQType);
  const FunctionType *NewType = New->getType()->getAs<FunctionType>();
  FunctionType::ExtInfo OldTypeInfo = OldType->getExtInfo();
  FunctionType::ExtInfo NewTypeInfo = NewType->getExtInfo();
  bool RequiresAdjustment = false;
  if (OldTypeInfo.getCC() == NewTypeInfo.getCC()) {
    // Fast path: nothing to do.

  // Inherit the CC from the previous declaration if it was specified
  // there but not here.
  } else if (NewTypeInfo.getCC() == CC_Default) {
    NewTypeInfo = NewTypeInfo.withCallingConv(OldTypeInfo.getCC());
    RequiresAdjustment = true;

  // Don't complain about mismatches when the default CC is
  // effectively the same as the explict one. Only Old decl contains correct
  // information about storage class of CXXMethod.
  } else if (OldTypeInfo.getCC() == CC_Default &&
             isABIDefaultCC(*this, NewTypeInfo.getCC(), Old)) {
    NewTypeInfo = NewTypeInfo.withCallingConv(OldTypeInfo.getCC());
    RequiresAdjustment = true;

  } else if (!Context.isSameCallConv(OldTypeInfo.getCC(),
                                     NewTypeInfo.getCC())) {
    // Calling conventions really aren't compatible, so complain.
    Diag(New->getLocation(), diag::err_cconv_change)
      << FunctionType::getNameForCallConv(NewTypeInfo.getCC())
      << (OldTypeInfo.getCC() == CC_Default)
      << (OldTypeInfo.getCC() == CC_Default ? "" :
          FunctionType::getNameForCallConv(OldTypeInfo.getCC()));
    Diag(Old->getLocation(), diag::note_previous_declaration);
    return true;
  }

  // FIXME: diagnose the other way around?
  if (OldTypeInfo.getNoReturn() && !NewTypeInfo.getNoReturn()) {
    NewTypeInfo = NewTypeInfo.withNoReturn(true);
    RequiresAdjustment = true;
  }

  // Merge regparm attribute.
  if (OldTypeInfo.getHasRegParm() != NewTypeInfo.getHasRegParm() ||
      OldTypeInfo.getRegParm() != NewTypeInfo.getRegParm()) {
    if (NewTypeInfo.getHasRegParm()) {
      Diag(New->getLocation(), diag::err_regparm_mismatch)
        << NewType->getRegParmType()
        << OldType->getRegParmType();
      Diag(Old->getLocation(), diag::note_previous_declaration);
      return true;
    }

    NewTypeInfo = NewTypeInfo.withRegParm(OldTypeInfo.getRegParm());
    RequiresAdjustment = true;
  }

  // Merge ns_returns_retained attribute.
  if (OldTypeInfo.getProducesResult() != NewTypeInfo.getProducesResult()) {
    if (NewTypeInfo.getProducesResult()) {
      Diag(New->getLocation(), diag::err_returns_retained_mismatch);
      Diag(Old->getLocation(), diag::note_previous_declaration);
      return true;
    }

    NewTypeInfo = NewTypeInfo.withProducesResult(true);
    RequiresAdjustment = true;
  }

  if (RequiresAdjustment) {
    NewType = Context.adjustFunctionType(NewType, NewTypeInfo);
    New->setType(QualType(NewType, 0));
    NewQType = Context.getCanonicalType(New->getType());
  }

  // If this redeclaration makes the function inline, we may need to add it to
  // UndefinedButUsed.
  if (!Old->isInlined() && New->isInlined() &&
      !New->hasAttr<GNUInlineAttr>() &&
      (getLangOpts().CPlusPlus || !getLangOpts().GNUInline) &&
      Old->isUsed(false) &&
      !Old->isDefined() && !New->isThisDeclarationADefinition())
    UndefinedButUsed.insert(std::make_pair(Old->getCanonicalDecl(),
                                           SourceLocation()));

  // If this redeclaration makes it newly gnu_inline, we don't want to warn
  // about it.
  if (New->hasAttr<GNUInlineAttr>() &&
      Old->isInlined() && !Old->hasAttr<GNUInlineAttr>()) {
    UndefinedButUsed.erase(Old->getCanonicalDecl());
  }

  if (getLangOpts().CPlusPlus) {
    // (C++98 13.1p2):
    //   Certain function declarations cannot be overloaded:
    //     -- Function declarations that differ only in the return type
    //        cannot be overloaded.
    QualType OldReturnType = OldType->getResultType();
    QualType NewReturnType = cast<FunctionType>(NewQType)->getResultType();
    QualType ResQT;
    if (OldReturnType != NewReturnType) {
      if (NewReturnType->isObjCObjectPointerType()
          && OldReturnType->isObjCObjectPointerType())
        ResQT = Context.mergeObjCGCQualifiers(NewQType, OldQType);
      if (ResQT.isNull()) {
        if (New->isCXXClassMember() && New->isOutOfLine())
          Diag(New->getLocation(),
               diag::err_member_def_does_not_match_ret_type) << New;
        else
          Diag(New->getLocation(), diag::err_ovl_diff_return_type);
        Diag(Old->getLocation(), PrevDiag) << Old << Old->getType();
        return true;
      }
      else
        NewQType = ResQT;
    }

    const CXXMethodDecl* OldMethod = dyn_cast<CXXMethodDecl>(Old);
    CXXMethodDecl* NewMethod = dyn_cast<CXXMethodDecl>(New);
    if (OldMethod && NewMethod) {
      // Preserve triviality.
      NewMethod->setTrivial(OldMethod->isTrivial());

      // MSVC allows explicit template specialization at class scope:
      // 2 CXMethodDecls referring to the same function will be injected.
      // We don't want a redeclartion error.
      bool IsClassScopeExplicitSpecialization =
                              OldMethod->isFunctionTemplateSpecialization() &&
                              NewMethod->isFunctionTemplateSpecialization();
      bool isFriend = NewMethod->getFriendObjectKind();

      if (!isFriend && NewMethod->getLexicalDeclContext()->isRecord() &&
          !IsClassScopeExplicitSpecialization) {
        //    -- Member function declarations with the same name and the
        //       same parameter types cannot be overloaded if any of them
        //       is a static member function declaration.
        if (OldMethod->isStatic() || NewMethod->isStatic()) {
          Diag(New->getLocation(), diag::err_ovl_static_nonstatic_member);
          Diag(Old->getLocation(), PrevDiag) << Old << Old->getType();
          return true;
        }

        // C++ [class.mem]p1:
        //   [...] A member shall not be declared twice in the
        //   member-specification, except that a nested class or member
        //   class template can be declared and then later defined.
        if (ActiveTemplateInstantiations.empty()) {
          unsigned NewDiag;
          if (isa<CXXConstructorDecl>(OldMethod))
            NewDiag = diag::err_constructor_redeclared;
          else if (isa<CXXDestructorDecl>(NewMethod))
            NewDiag = diag::err_destructor_redeclared;
          else if (isa<CXXConversionDecl>(NewMethod))
            NewDiag = diag::err_conv_function_redeclared;
          else
            NewDiag = diag::err_member_redeclared;

          Diag(New->getLocation(), NewDiag);
        } else {
          Diag(New->getLocation(), diag::err_member_redeclared_in_instantiation)
            << New << New->getType();
        }
        Diag(Old->getLocation(), PrevDiag) << Old << Old->getType();

      // Complain if this is an explicit declaration of a special
      // member that was initially declared implicitly.
      //
      // As an exception, it's okay to befriend such methods in order
      // to permit the implicit constructor/destructor/operator calls.
      } else if (OldMethod->isImplicit()) {
        if (isFriend) {
          NewMethod->setImplicit();
        } else {
          Diag(NewMethod->getLocation(),
               diag::err_definition_of_implicitly_declared_member)
            << New << getSpecialMember(OldMethod);
          return true;
        }
      } else if (OldMethod->isExplicitlyDefaulted() && !isFriend) {
        Diag(NewMethod->getLocation(),
             diag::err_definition_of_explicitly_defaulted_member)
          << getSpecialMember(OldMethod);
        return true;
      }
    }

    // C++11 [dcl.attr.noreturn]p1:
    //   The first declaration of a function shall specify the noreturn
    //   attribute if any declaration of that function specifies the noreturn
    //   attribute.
    if (New->hasAttr<CXX11NoReturnAttr>() &&
        !Old->hasAttr<CXX11NoReturnAttr>()) {
      Diag(New->getAttr<CXX11NoReturnAttr>()->getLocation(),
           diag::err_noreturn_missing_on_first_decl);
      Diag(Old->getFirstDeclaration()->getLocation(),
           diag::note_noreturn_missing_first_decl);
    }

    // C++11 [dcl.attr.depend]p2:
    //   The first declaration of a function shall specify the
    //   carries_dependency attribute for its declarator-id if any declaration
    //   of the function specifies the carries_dependency attribute.
    if (New->hasAttr<CarriesDependencyAttr>() &&
        !Old->hasAttr<CarriesDependencyAttr>()) {
      Diag(New->getAttr<CarriesDependencyAttr>()->getLocation(),
           diag::err_carries_dependency_missing_on_first_decl) << 0/*Function*/;
      Diag(Old->getFirstDeclaration()->getLocation(),
           diag::note_carries_dependency_missing_first_decl) << 0/*Function*/;
    }

    // (C++98 8.3.5p3):
    //   All declarations for a function shall agree exactly in both the
    //   return type and the parameter-type-list.
    // We also want to respect all the extended bits except noreturn.

    // noreturn should now match unless the old type info didn't have it.
    QualType OldQTypeForComparison = OldQType;
    if (!OldTypeInfo.getNoReturn() && NewTypeInfo.getNoReturn()) {
      assert(OldQType == QualType(OldType, 0));
      const FunctionType *OldTypeForComparison
        = Context.adjustFunctionType(OldType, OldTypeInfo.withNoReturn(true));
      OldQTypeForComparison = QualType(OldTypeForComparison, 0);
      assert(OldQTypeForComparison.isCanonical());
    }

    if (haveIncompatibleLanguageLinkages(Old, New)) {
      Diag(New->getLocation(), diag::err_different_language_linkage) << New;
      Diag(Old->getLocation(), PrevDiag);
      return true;
    }

    if (OldQTypeForComparison == NewQType)
      return MergeCompatibleFunctionDecls(New, Old, S);

    // Fall through for conflicting redeclarations and redefinitions.
  }

  // C: Function types need to be compatible, not identical. This handles
  // duplicate function decls like "void f(int); void f(enum X);" properly.
  if (!getLangOpts().CPlusPlus &&
      Context.typesAreCompatible(OldQType, NewQType)) {
    const FunctionType *OldFuncType = OldQType->getAs<FunctionType>();
    const FunctionType *NewFuncType = NewQType->getAs<FunctionType>();
    const FunctionProtoType *OldProto = 0;
    if (isa<FunctionNoProtoType>(NewFuncType) &&
        (OldProto = dyn_cast<FunctionProtoType>(OldFuncType))) {
      // The old declaration provided a function prototype, but the
      // new declaration does not. Merge in the prototype.
      assert(!OldProto->hasExceptionSpec() && "Exception spec in C");
      SmallVector<QualType, 16> ParamTypes(OldProto->arg_type_begin(),
                                                 OldProto->arg_type_end());
      NewQType = Context.getFunctionType(NewFuncType->getResultType(),
                                         ParamTypes,
                                         OldProto->getExtProtoInfo());
      New->setType(NewQType);
      New->setHasInheritedPrototype();

      // Synthesize a parameter for each argument type.
      SmallVector<ParmVarDecl*, 16> Params;
      for (FunctionProtoType::arg_type_iterator
             ParamType = OldProto->arg_type_begin(),
             ParamEnd = OldProto->arg_type_end();
           ParamType != ParamEnd; ++ParamType) {
        ParmVarDecl *Param = ParmVarDecl::Create(Context, New,
                                                 SourceLocation(),
                                                 SourceLocation(), 0,
                                                 *ParamType, /*TInfo=*/0,
                                                 SC_None, SC_None,
                                                 0);
        Param->setScopeInfo(0, Params.size());
        Param->setImplicit();
        Params.push_back(Param);
      }

      New->setParams(Params);
    }

    return MergeCompatibleFunctionDecls(New, Old, S);
  }

  // GNU C permits a K&R definition to follow a prototype declaration
  // if the declared types of the parameters in the K&R definition
  // match the types in the prototype declaration, even when the
  // promoted types of the parameters from the K&R definition differ
  // from the types in the prototype. GCC then keeps the types from
  // the prototype.
  //
  // If a variadic prototype is followed by a non-variadic K&R definition,
  // the K&R definition becomes variadic.  This is sort of an edge case, but
  // it's legal per the standard depending on how you read C99 6.7.5.3p15 and
  // C99 6.9.1p8.
  if (!getLangOpts().CPlusPlus &&
      Old->hasPrototype() && !New->hasPrototype() &&
      New->getType()->getAs<FunctionProtoType>() &&
      Old->getNumParams() == New->getNumParams()) {
    SmallVector<QualType, 16> ArgTypes;
    SmallVector<GNUCompatibleParamWarning, 16> Warnings;
    const FunctionProtoType *OldProto
      = Old->getType()->getAs<FunctionProtoType>();
    const FunctionProtoType *NewProto
      = New->getType()->getAs<FunctionProtoType>();

    // Determine whether this is the GNU C extension.
    QualType MergedReturn = Context.mergeTypes(OldProto->getResultType(),
                                               NewProto->getResultType());
    bool LooseCompatible = !MergedReturn.isNull();
    for (unsigned Idx = 0, End = Old->getNumParams();
         LooseCompatible && Idx != End; ++Idx) {
      ParmVarDecl *OldParm = Old->getParamDecl(Idx);
      ParmVarDecl *NewParm = New->getParamDecl(Idx);
      if (Context.typesAreCompatible(OldParm->getType(),
                                     NewProto->getArgType(Idx))) {
        ArgTypes.push_back(NewParm->getType());
      } else if (Context.typesAreCompatible(OldParm->getType(),
                                            NewParm->getType(),
                                            /*CompareUnqualified=*/true)) {
        GNUCompatibleParamWarning Warn
          = { OldParm, NewParm, NewProto->getArgType(Idx) };
        Warnings.push_back(Warn);
        ArgTypes.push_back(NewParm->getType());
      } else
        LooseCompatible = false;
    }

    if (LooseCompatible) {
      for (unsigned Warn = 0; Warn < Warnings.size(); ++Warn) {
        Diag(Warnings[Warn].NewParm->getLocation(),
             diag::ext_param_promoted_not_compatible_with_prototype)
          << Warnings[Warn].PromotedType
          << Warnings[Warn].OldParm->getType();
        if (Warnings[Warn].OldParm->getLocation().isValid())
          Diag(Warnings[Warn].OldParm->getLocation(),
               diag::note_previous_declaration);
      }

      New->setType(Context.getFunctionType(MergedReturn, ArgTypes,
                                           OldProto->getExtProtoInfo()));
      return MergeCompatibleFunctionDecls(New, Old, S);
    }

    // Fall through to diagnose conflicting types.
  }

  // A function that has already been declared has been redeclared or defined
  // with a different type- show appropriate diagnostic
  if (unsigned BuiltinID = Old->getBuiltinID()) {
    // The user has declared a builtin function with an incompatible
    // signature.
    if (Context.BuiltinInfo.isPredefinedLibFunction(BuiltinID)) {
      // The function the user is redeclaring is a library-defined
      // function like 'malloc' or 'printf'. Warn about the
      // redeclaration, then pretend that we don't know about this
      // library built-in.
      Diag(New->getLocation(), diag::warn_redecl_library_builtin) << New;
      Diag(Old->getLocation(), diag::note_previous_builtin_declaration)
        << Old << Old->getType();
      New->getIdentifier()->setBuiltinID(Builtin::NotBuiltin);
      Old->setInvalidDecl();
      return false;
    }

    PrevDiag = diag::note_previous_builtin_declaration;
  }

  Diag(New->getLocation(), diag::err_conflicting_types) << New->getDeclName();
  Diag(Old->getLocation(), PrevDiag) << Old << Old->getType();
  return true;
}

/// \brief Completes the merge of two function declarations that are
/// known to be compatible.
///
/// This routine handles the merging of attributes and other
/// properties of function declarations form the old declaration to
/// the new declaration, once we know that New is in fact a
/// redeclaration of Old.
///
/// \returns false
bool Sema::MergeCompatibleFunctionDecls(FunctionDecl *New, FunctionDecl *Old,
                                        Scope *S) {
  // Merge the attributes
  mergeDeclAttributes(New, Old);

  // Merge the storage class.
  if (Old->getStorageClass() != SC_Extern &&
      Old->getStorageClass() != SC_None)
    New->setStorageClass(Old->getStorageClass());

  // Merge "pure" flag.
  if (Old->isPure())
    New->setPure();

  // Merge "used" flag.
  if (Old->isUsed(false))
    New->setUsed();

  // Merge attributes from the parameters.  These can mismatch with K&R
  // declarations.
  if (New->getNumParams() == Old->getNumParams())
    for (unsigned i = 0, e = New->getNumParams(); i != e; ++i)
      mergeParamDeclAttributes(New->getParamDecl(i), Old->getParamDecl(i),
                               *this);

  if (getLangOpts().CPlusPlus)
    return MergeCXXFunctionDecl(New, Old, S);

  // Merge the function types so the we get the composite types for the return
  // and argument types.
  QualType Merged = Context.mergeTypes(Old->getType(), New->getType());
  if (!Merged.isNull())
    New->setType(Merged);

  return false;
}


void Sema::mergeObjCMethodDecls(ObjCMethodDecl *newMethod,
                                ObjCMethodDecl *oldMethod) {

  // Merge the attributes, including deprecated/unavailable
  mergeDeclAttributes(newMethod, oldMethod, AMK_Override);

  // Merge attributes from the parameters.
  ObjCMethodDecl::param_const_iterator oi = oldMethod->param_begin(),
                                       oe = oldMethod->param_end();
  for (ObjCMethodDecl::param_iterator
         ni = newMethod->param_begin(), ne = newMethod->param_end();
       ni != ne && oi != oe; ++ni, ++oi)
    mergeParamDeclAttributes(*ni, *oi, *this);

  CheckObjCMethodOverride(newMethod, oldMethod);
}

/// MergeVarDeclTypes - 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.
///
/// Declarations using the auto type specifier (C++ [decl.spec.auto]) call back
/// to here in AddInitializerToDecl. We can't check them before the initializer
/// is attached.
void Sema::MergeVarDeclTypes(VarDecl *New, VarDecl *Old) {
  if (New->isInvalidDecl() || Old->isInvalidDecl())
    return;

  QualType MergedT;
  if (getLangOpts().CPlusPlus) {
    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())) {
      // These could still be something that needs exception specs checked.
      return MergeVarDeclExceptionSpecs(New, Old);
    }
    // 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
    //   array object can specify array types that differ by the presence or
    //   absence of a major array bound (8.3.4).
    else if (Old->getType()->isIncompleteArrayType() &&
             New->getType()->isArrayType()) {
      const ArrayType *OldArray = Context.getAsArrayType(Old->getType());
      const ArrayType *NewArray = Context.getAsArrayType(New->getType());
      if (Context.hasSameType(OldArray->getElementType(),
                              NewArray->getElementType()))
        MergedT = New->getType();
    } else if (Old->getType()->isArrayType() &&
             New->getType()->isIncompleteArrayType()) {
      const ArrayType *OldArray = Context.getAsArrayType(Old->getType());
      const ArrayType *NewArray = Context.getAsArrayType(New->getType());
      if (Context.hasSameType(OldArray->getElementType(),
                              NewArray->getElementType()))
        MergedT = Old->getType();
    } else if (New->getType()->isObjCObjectPointerType()
               && Old->getType()->isObjCObjectPointerType()) {
        MergedT = Context.mergeObjCGCQualifiers(New->getType(),
                                                        Old->getType());
    }
  } else {
    MergedT = Context.mergeTypes(New->getType(), Old->getType());
  }
  if (MergedT.isNull()) {
    Diag(New->getLocation(), diag::err_redefinition_different_type)
      << New->getDeclName() << New->getType() << Old->getType();
    Diag(Old->getLocation(), diag::note_previous_definition);
    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);
  // Warn if an already-declared variable is made a weak_import in a subsequent
  // declaration
  if (New->getAttr<WeakImportAttr>() &&
      Old->getStorageClass() == SC_None &&
      !Old->getAttr<WeakImportAttr>()) {
    Diag(New->getLocation(), diag::warn_weak_import) << New->getDeclName();
    Diag(Old->getLocation(), diag::note_previous_definition);
    // Remove weak_import attribute on new declaration.
    New->dropAttr<WeakImportAttr>();
  }

  // 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 &&
      (Old->getStorageClass() == SC_None || Old->hasExternalStorage())) {
    Diag(New->getLocation(), diag::err_static_non_static) << New->getDeclName();
    Diag(Old->getLocation(), diag::note_previous_definition);
    return New->setInvalidDecl();
  }
  // C99 6.2.2p4:
  //   For an identifier declared with the storage-class specifier
  //   extern in a scope in which a prior declaration of that
  //   identifier is visible,23) if the prior declaration specifies
  //   internal or external linkage, the linkage of the identifier at
  //   the later declaration is the same as the linkage specified at
  //   the prior declaration. If no prior declaration is visible, or
  //   if the prior declaration specifies no linkage, then the
  //   identifier has external linkage.
  if (New->hasExternalStorage() && Old->hasLinkage())
    /* Okay */;
  else if (New->getStorageClass() != SC_Static &&
           Old->getStorageClass() == SC_Static) {
    Diag(New->getLocation(), diag::err_non_static_static) << New->getDeclName();
    Diag(Old->getLocation(), diag::note_previous_definition);
    return New->setInvalidDecl();
  }

  // Check if extern is followed by non-extern and vice-versa.
  if (New->hasExternalStorage() &&
      !Old->hasLinkage() && Old->isLocalVarDecl()) {
    Diag(New->getLocation(), diag::err_extern_non_extern) << New->getDeclName();
    Diag(Old->getLocation(), diag::note_previous_definition);
    return New->setInvalidDecl();
  }
  if (Old->hasExternalStorage() &&
      New->isLocalVarDecl() && !New->hasLinkage()) {
    Diag(New->getLocation(), diag::err_non_extern_extern) << New->getDeclName();
    Diag(Old->getLocation(), diag::note_previous_definition);
    return New->setInvalidDecl();
  }

  // Variables with external linkage are analyzed in FinalizeDeclaratorGroup.

  // FIXME: The test for external storage here seems wrong? We still
  // need to check for mismatches.
  if (!New->hasExternalStorage() && !New->isFileVarDecl() &&
      // Don't complain about out-of-line definitions of static members.
      !(Old->getLexicalDeclContext()->isRecord() &&
        !New->getLexicalDeclContext()->isRecord())) {
    Diag(New->getLocation(), diag::err_redefinition) << New->getDeclName();
    Diag(Old->getLocation(), diag::note_previous_definition);
    return New->setInvalidDecl();
  }

  if (New->isThreadSpecified() && !Old->isThreadSpecified()) {
    Diag(New->getLocation(), diag::err_thread_non_thread) << New->getDeclName();
    Diag(Old->getLocation(), diag::note_previous_definition);
  } else if (!New->isThreadSpecified() && Old->isThreadSpecified()) {
    Diag(New->getLocation(), diag::err_non_thread_thread) << New->getDeclName();
    Diag(Old->getLocation(), diag::note_previous_definition);
  }

  // C++ doesn't have tentative definitions, so go right ahead and check here.
  const VarDecl *Def;
  if (getLangOpts().CPlusPlus &&
      New->isThisDeclarationADefinition() == VarDecl::Definition &&
      (Def = Old->getDefinition())) {
    Diag(New->getLocation(), diag::err_redefinition)
      << New->getDeclName();
    Diag(Def->getLocation(), diag::note_previous_definition);
    New->setInvalidDecl();
    return;
  }

  if (haveIncompatibleLanguageLinkages(Old, New)) {
    Diag(New->getLocation(), diag::err_different_language_linkage) << New;
    Diag(Old->getLocation(), diag::note_previous_definition);
    New->setInvalidDecl();
    return;
  }

  // c99 6.2.2 P4.
  // For an identifier declared with the storage-class specifier extern in a
  // scope in which a prior declaration of that identifier is visible, if
  // the prior declaration specifies internal or external linkage, the linkage
  // of the identifier at the later declaration is the same as the linkage
  // specified at the prior declaration.
  // FIXME. revisit this code.
  if (New->hasExternalStorage() &&
      Old->getLinkage() == InternalLinkage)
    New->setStorageClass(Old->getStorageClass());

  // Merge "used" flag.
  if (Old->isUsed(false))
    New->setUsed();

  // Keep a chain of previous declarations.
  New->setPreviousDeclaration(Old);

  // Inherit access appropriately.
  New->setAccess(Old->getAccess());
}

/// ParsedFreeStandingDeclSpec - This method is invoked when a declspec with
/// no declarator (e.g. "struct foo;") is parsed.
Decl *Sema::ParsedFreeStandingDeclSpec(Scope *S, AccessSpecifier AS,
                                       DeclSpec &DS) {
  return ParsedFreeStandingDeclSpec(S, AS, DS, MultiTemplateParamsArg());
}

/// ParsedFreeStandingDeclSpec - This method is invoked when a declspec with
/// no declarator (e.g. "struct foo;") is parsed. It also accepts template
/// parameters to cope with template friend declarations.
Decl *Sema::ParsedFreeStandingDeclSpec(Scope *S, AccessSpecifier AS,
                                       DeclSpec &DS,
                                       MultiTemplateParamsArg TemplateParams,
                                       bool IsExplicitInstantiation) {
  Decl *TagD = 0;
  TagDecl *Tag = 0;
  if (DS.getTypeSpecType() == DeclSpec::TST_class ||
      DS.getTypeSpecType() == DeclSpec::TST_struct ||
      DS.getTypeSpecType() == DeclSpec::TST_interface ||
      DS.getTypeSpecType() == DeclSpec::TST_union ||
      DS.getTypeSpecType() == DeclSpec::TST_enum) {
    TagD = DS.getRepAsDecl();

    if (!TagD) // We probably had an error
      return 0;

    // Note that the above type specs guarantee that the
    // type rep is a Decl, whereas in many of the others
    // it's a Type.
    if (isa<TagDecl>(TagD))
      Tag = cast<TagDecl>(TagD);
    else if (ClassTemplateDecl *CTD = dyn_cast<ClassTemplateDecl>(TagD))
      Tag = CTD->getTemplatedDecl();
  }

  if (Tag) {
    getASTContext().addUnnamedTag(Tag);
    Tag->setFreeStanding();
    if (Tag->isInvalidDecl())
      return Tag;
  }

  if (unsigned TypeQuals = DS.getTypeQualifiers()) {
    // Enforce C99 6.7.3p2: "Types other than pointer types derived from object
    // or incomplete types shall not be restrict-qualified."
    if (TypeQuals & DeclSpec::TQ_restrict)
      Diag(DS.getRestrictSpecLoc(),
           diag::err_typecheck_invalid_restrict_not_pointer_noarg)
           << DS.getSourceRange();
  }

  if (DS.isConstexprSpecified()) {
    // C++0x [dcl.constexpr]p1: constexpr can only be applied to declarations
    // and definitions of functions and variables.
    if (Tag)
      Diag(DS.getConstexprSpecLoc(), diag::err_constexpr_tag)
        << (DS.getTypeSpecType() == DeclSpec::TST_class ? 0 :
            DS.getTypeSpecType() == DeclSpec::TST_struct ? 1 :
            DS.getTypeSpecType() == DeclSpec::TST_interface ? 2 :
            DS.getTypeSpecType() == DeclSpec::TST_union ? 3 : 4);
    else
      Diag(DS.getConstexprSpecLoc(), diag::err_constexpr_no_declarators);
    // Don't emit warnings after this error.
    return TagD;
  }

  DiagnoseFunctionSpecifiers(DS);

  if (DS.isFriendSpecified()) {
    // If we're dealing with a decl but not a TagDecl, assume that
    // whatever routines created it handled the friendship aspect.
    if (TagD && !Tag)
      return 0;
    return ActOnFriendTypeDecl(S, DS, TemplateParams);
  }

  CXXScopeSpec &SS = DS.getTypeSpecScope();
  bool IsExplicitSpecialization =
    !TemplateParams.empty() && TemplateParams.back()->size() == 0;
  if (Tag && SS.isNotEmpty() && !Tag->isCompleteDefinition() &&
      !IsExplicitInstantiation && !IsExplicitSpecialization) {
    // Per C++ [dcl.type.elab]p1, a class declaration cannot have a
    // nested-name-specifier unless it is an explicit instantiation
    // or an explicit specialization.
    // Per C++ [dcl.enum]p1, an opaque-enum-declaration can't either.
    Diag(SS.getBeginLoc(), diag::err_standalone_class_nested_name_specifier)
      << (DS.getTypeSpecType() == DeclSpec::TST_class ? 0 :
          DS.getTypeSpecType() == DeclSpec::TST_struct ? 1 :
          DS.getTypeSpecType() == DeclSpec::TST_interface ? 2 :
          DS.getTypeSpecType() == DeclSpec::TST_union ? 3 : 4)
      << SS.getRange();
    return 0;
  }

  // Track whether this decl-specifier declares anything.
  bool DeclaresAnything = true;

  // Handle anonymous struct definitions.
  if (RecordDecl *Record = dyn_cast_or_null<RecordDecl>(Tag)) {
    if (!Record->getDeclName() && Record->isCompleteDefinition() &&
        DS.getStorageClassSpec() != DeclSpec::SCS_typedef) {
      if (getLangOpts().CPlusPlus ||
          Record->getDeclContext()->isRecord())
        return BuildAnonymousStructOrUnion(S, DS, AS, Record);

      DeclaresAnything = false;
    }
  }

  // Check for Microsoft C extension: anonymous struct member.
  if (getLangOpts().MicrosoftExt && !getLangOpts().CPlusPlus &&
      CurContext->isRecord() &&
      DS.getStorageClassSpec() == DeclSpec::SCS_unspecified) {
    // Handle 2 kinds of anonymous struct:
    //   struct STRUCT;
    // and
    //   STRUCT_TYPE;  <- where STRUCT_TYPE is a typedef struct.
    RecordDecl *Record = dyn_cast_or_null<RecordDecl>(Tag);
    if ((Record && Record->getDeclName() && !Record->isCompleteDefinition()) ||
        (DS.getTypeSpecType() == DeclSpec::TST_typename &&
         DS.getRepAsType().get()->isStructureType())) {
      Diag(DS.getLocStart(), diag::ext_ms_anonymous_struct)
        << DS.getSourceRange();
      return BuildMicrosoftCAnonymousStruct(S, DS, Record);
    }
  }

  // Skip all the checks below if we have a type error.
  if (DS.getTypeSpecType() == DeclSpec::TST_error ||
      (TagD && TagD->isInvalidDecl()))
    return TagD;

  if (getLangOpts().CPlusPlus &&
      DS.getStorageClassSpec() != DeclSpec::SCS_typedef)
    if (EnumDecl *Enum = dyn_cast_or_null<EnumDecl>(Tag))
      if (Enum->enumerator_begin() == Enum->enumerator_end() &&
          !Enum->getIdentifier() && !Enum->isInvalidDecl())
        DeclaresAnything = false;

  if (!DS.isMissingDeclaratorOk()) {
    // Customize diagnostic for a typedef missing a name.
    if (DS.getStorageClassSpec() == DeclSpec::SCS_typedef)
      Diag(DS.getLocStart(), diag::ext_typedef_without_a_name)
        << DS.getSourceRange();
    else
      DeclaresAnything = false;
  }

  if (DS.isModulePrivateSpecified() &&
      Tag && Tag->getDeclContext()->isFunctionOrMethod())
    Diag(DS.getModulePrivateSpecLoc(), diag::err_module_private_local_class)
      << Tag->getTagKind()
      << FixItHint::CreateRemoval(DS.getModulePrivateSpecLoc());

  ActOnDocumentableDecl(TagD);

  // C 6.7/2:
  //   A declaration [...] shall declare at least a declarator [...], a tag,
  //   or the members of an enumeration.
  // C++ [dcl.dcl]p3:
  //   [If there are no declarators], and except for the declaration of an
  //   unnamed bit-field, the decl-specifier-seq shall introduce one or more
  //   names into the program, or shall redeclare a name introduced by a
  //   previous declaration.
  if (!DeclaresAnything) {
    // In C, we allow this as a (popular) extension / bug. Don't bother
    // producing further diagnostics for redundant qualifiers after this.
    Diag(DS.getLocStart(), diag::ext_no_declarators) << DS.getSourceRange();
    return TagD;
  }

  // C++ [dcl.stc]p1:
  //   If a storage-class-specifier appears in a decl-specifier-seq, [...] the
  //   init-declarator-list of the declaration shall not be empty.
  // C++ [dcl.fct.spec]p1:
  //   If a cv-qualifier appears in a decl-specifier-seq, the
  //   init-declarator-list of the declaration shall not be empty.
  //
  // Spurious qualifiers here appear to be valid in C.
  unsigned DiagID = diag::warn_standalone_specifier;
  if (getLangOpts().CPlusPlus)
    DiagID = diag::ext_standalone_specifier;

  // Note that a linkage-specification sets a storage class, but
  // 'extern "C" struct foo;' is actually valid and not theoretically
  // useless.
  if (DeclSpec::SCS SCS = DS.getStorageClassSpec())
    if (!DS.isExternInLinkageSpec() && SCS != DeclSpec::SCS_typedef)
      Diag(DS.getStorageClassSpecLoc(), DiagID)
        << DeclSpec::getSpecifierName(SCS);

  if (DS.isThreadSpecified())
    Diag(DS.getThreadSpecLoc(), DiagID) << "__thread";
  if (DS.getTypeQualifiers()) {
    if (DS.getTypeQualifiers() & DeclSpec::TQ_const)
      Diag(DS.getConstSpecLoc(), DiagID) << "const";
    if (DS.getTypeQualifiers() & DeclSpec::TQ_volatile)
      Diag(DS.getConstSpecLoc(), DiagID) << "volatile";
    // Restrict is covered above.
  }

  // Warn about ignored type attributes, for example:
  // __attribute__((aligned)) struct A;
  // Attributes should be placed after tag to apply to type declaration.
  if (!DS.getAttributes().empty()) {
    DeclSpec::TST TypeSpecType = DS.getTypeSpecType();
    if (TypeSpecType == DeclSpec::TST_class ||
        TypeSpecType == DeclSpec::TST_struct ||
        TypeSpecType == DeclSpec::TST_interface ||
        TypeSpecType == DeclSpec::TST_union ||
        TypeSpecType == DeclSpec::TST_enum) {
      AttributeList* attrs = DS.getAttributes().getList();
      while (attrs) {
        Diag(attrs->getLoc(), diag::warn_declspec_attribute_ignored)
        << attrs->getName()
        << (TypeSpecType == DeclSpec::TST_class ? 0 :
            TypeSpecType == DeclSpec::TST_struct ? 1 :
            TypeSpecType == DeclSpec::TST_union ? 2 :
            TypeSpecType == DeclSpec::TST_interface ? 3 : 4);
        attrs = attrs->getNext();
      }
    }
  }

  return TagD;
}

/// We are trying to inject an anonymous member into the given scope;
/// check if there's an existing declaration that can't be overloaded.
///
/// \return true if this is a forbidden redeclaration
static bool CheckAnonMemberRedeclaration(Sema &SemaRef,
                                         Scope *S,
                                         DeclContext *Owner,
                                         DeclarationName Name,
                                         SourceLocation NameLoc,
                                         unsigned diagnostic) {
  LookupResult R(SemaRef, Name, NameLoc, Sema::LookupMemberName,
                 Sema::ForRedeclaration);
  if (!SemaRef.LookupName(R, S)) return false;

  if (R.getAsSingle<TagDecl>())
    return false;

  // Pick a representative declaration.
  NamedDecl *PrevDecl = R.getRepresentativeDecl()->getUnderlyingDecl();
  assert(PrevDecl && "Expected a non-null Decl");

  if (!SemaRef.isDeclInScope(PrevDecl, Owner, S))
    return false;

  SemaRef.Diag(NameLoc, diagnostic) << Name;
  SemaRef.Diag(PrevDecl->getLocation(), diag::note_previous_declaration);

  return true;
}

/// InjectAnonymousStructOrUnionMembers - Inject the members of the
/// anonymous struct or union AnonRecord into the owning context Owner
/// and scope S. This routine will be invoked just after we realize
/// that an unnamed union or struct is actually an anonymous union or
/// struct, e.g.,
///
/// @code
/// union {
///   int i;
///   float f;
/// }; // InjectAnonymousStructOrUnionMembers called here to inject i and
///    // f into the surrounding scope.x
/// @endcode
///
/// This routine is recursive, injecting the names of nested anonymous
/// structs/unions into the owning context and scope as well.
static bool InjectAnonymousStructOrUnionMembers(Sema &SemaRef, Scope *S,
                                                DeclContext *Owner,
                                                RecordDecl *AnonRecord,
                                                AccessSpecifier AS,
                              SmallVector<NamedDecl*, 2> &Chaining,
                                                      bool MSAnonStruct) {
  unsigned diagKind
    = AnonRecord->isUnion() ? diag::err_anonymous_union_member_redecl
                            : diag::err_anonymous_struct_member_redecl;

  bool Invalid = false;

  // Look every FieldDecl and IndirectFieldDecl with a name.
  for (RecordDecl::decl_iterator D = AnonRecord->decls_begin(),
                               DEnd = AnonRecord->decls_end();
       D != DEnd; ++D) {
    if ((isa<FieldDecl>(*D) || isa<IndirectFieldDecl>(*D)) &&
        cast<NamedDecl>(*D)->getDeclName()) {
      ValueDecl *VD = cast<ValueDecl>(*D);
      if (CheckAnonMemberRedeclaration(SemaRef, S, Owner, VD->getDeclName(),
                                       VD->getLocation(), diagKind)) {
        // C++ [class.union]p2:
        //   The names of the members of an anonymous union shall be
        //   distinct from the names of any other entity in the
        //   scope in which the anonymous union is declared.
        Invalid = true;
      } else {
        // C++ [class.union]p2:
        //   For the purpose of name lookup, after the anonymous union
        //   definition, the members of the anonymous union are
        //   considered to have been defined in the scope in which the
        //   anonymous union is declared.
        unsigned OldChainingSize = Chaining.size();
        if (IndirectFieldDecl *IF = dyn_cast<IndirectFieldDecl>(VD))
          for (IndirectFieldDecl::chain_iterator PI = IF->chain_begin(),
               PE = IF->chain_end(); PI != PE; ++PI)
            Chaining.push_back(*PI);
        else
          Chaining.push_back(VD);

        assert(Chaining.size() >= 2);
        NamedDecl **NamedChain =
          new (SemaRef.Context)NamedDecl*[Chaining.size()];
        for (unsigned i = 0; i < Chaining.size(); i++)
          NamedChain[i] = Chaining[i];

        IndirectFieldDecl* IndirectField =
          IndirectFieldDecl::Create(SemaRef.Context, Owner, VD->getLocation(),
                                    VD->getIdentifier(), VD->getType(),
                                    NamedChain, Chaining.size());

        IndirectField->setAccess(AS);
        IndirectField->setImplicit();
        SemaRef.PushOnScopeChains(IndirectField, S);

        // That includes picking up the appropriate access specifier.
        if (AS != AS_none) IndirectField->setAccess(AS);

        Chaining.resize(OldChainingSize);
      }
    }
  }

  return Invalid;
}

/// StorageClassSpecToVarDeclStorageClass - Maps a DeclSpec::SCS to
/// a VarDecl::StorageClass. Any error reporting is up to the caller:
/// illegal input values are mapped to SC_None.
static StorageClass
StorageClassSpecToVarDeclStorageClass(DeclSpec::SCS StorageClassSpec) {
  switch (StorageClassSpec) {
  case DeclSpec::SCS_unspecified:    return SC_None;
  case DeclSpec::SCS_extern:         return SC_Extern;
  case DeclSpec::SCS_static:         return SC_Static;
  case DeclSpec::SCS_auto:           return SC_Auto;
  case DeclSpec::SCS_register:       return SC_Register;
  case DeclSpec::SCS_private_extern: return SC_PrivateExtern;
    // Illegal SCSs map to None: error reporting is up to the caller.
  case DeclSpec::SCS_mutable:        // Fall through.
  case DeclSpec::SCS_typedef:        return SC_None;
  }
  llvm_unreachable("unknown storage class specifier");
}

/// StorageClassSpecToFunctionDeclStorageClass - Maps a DeclSpec::SCS to
/// a StorageClass. Any error reporting is up to the caller:
/// illegal input values are mapped to SC_None.
static StorageClass
StorageClassSpecToFunctionDeclStorageClass(DeclSpec::SCS StorageClassSpec) {
  switch (StorageClassSpec) {
  case DeclSpec::SCS_unspecified:    return SC_None;
  case DeclSpec::SCS_extern:         return SC_Extern;
  case DeclSpec::SCS_static:         return SC_Static;
  case DeclSpec::SCS_private_extern: return SC_PrivateExtern;
    // Illegal SCSs map to None: error reporting is up to the caller.
  case DeclSpec::SCS_auto:           // Fall through.
  case DeclSpec::SCS_mutable:        // Fall through.
  case DeclSpec::SCS_register:       // Fall through.
  case DeclSpec::SCS_typedef:        return SC_None;
  }
  llvm_unreachable("unknown storage class specifier");
}

/// BuildAnonymousStructOrUnion - Handle the declaration of an
/// anonymous structure or union. Anonymous unions are a C++ feature
/// (C++ [class.union]) and a C11 feature; anonymous structures
/// are a C11 feature and GNU C++ extension.
Decl *Sema::BuildAnonymousStructOrUnion(Scope *S, DeclSpec &DS,
                                             AccessSpecifier AS,
                                             RecordDecl *Record) {
  DeclContext *Owner = Record->getDeclContext();

  // Diagnose whether this anonymous struct/union is an extension.
  if (Record->isUnion() && !getLangOpts().CPlusPlus && !getLangOpts().C11)
    Diag(Record->getLocation(), diag::ext_anonymous_union);
  else if (!Record->isUnion() && getLangOpts().CPlusPlus)
    Diag(Record->getLocation(), diag::ext_gnu_anonymous_struct);
  else if (!Record->isUnion() && !getLangOpts().C11)
    Diag(Record->getLocation(), diag::ext_c11_anonymous_struct);

  // C and C++ require different kinds of checks for anonymous
  // structs/unions.
  bool Invalid = false;
  if (getLangOpts().CPlusPlus) {
    const char* PrevSpec = 0;
    unsigned DiagID;
    if (Record->isUnion()) {
      // C++ [class.union]p6:
      //   Anonymous unions declared in a named namespace or in the
      //   global namespace shall be declared static.
      if (DS.getStorageClassSpec() != DeclSpec::SCS_static &&
          (isa<TranslationUnitDecl>(Owner) ||
           (isa<NamespaceDecl>(Owner) &&
            cast<NamespaceDecl>(Owner)->getDeclName()))) {
        Diag(Record->getLocation(), diag::err_anonymous_union_not_static)
          << FixItHint::CreateInsertion(Record->getLocation(), "static ");

        // Recover by adding 'static'.
        DS.SetStorageClassSpec(*this, DeclSpec::SCS_static, SourceLocation(),
                               PrevSpec, DiagID);
      }
      // C++ [class.union]p6:
      //   A storage class is not allowed in a declaration of an
      //   anonymous union in a class scope.
      else if (DS.getStorageClassSpec() != DeclSpec::SCS_unspecified &&
               isa<RecordDecl>(Owner)) {
        Diag(DS.getStorageClassSpecLoc(),
             diag::err_anonymous_union_with_storage_spec)
          << FixItHint::CreateRemoval(DS.getStorageClassSpecLoc());

        // Recover by removing the storage specifier.
        DS.SetStorageClassSpec(*this, DeclSpec::SCS_unspecified,
                               SourceLocation(),
                               PrevSpec, DiagID);
      }
    }

    // Ignore const/volatile/restrict qualifiers.
    if (DS.getTypeQualifiers()) {
      if (DS.getTypeQualifiers() & DeclSpec::TQ_const)
        Diag(DS.getConstSpecLoc(), diag::ext_anonymous_struct_union_qualified)
          << Record->isUnion() << 0
          << FixItHint::CreateRemoval(DS.getConstSpecLoc());
      if (DS.getTypeQualifiers() & DeclSpec::TQ_volatile)
        Diag(DS.getVolatileSpecLoc(),
             diag::ext_anonymous_struct_union_qualified)
          << Record->isUnion() << 1
          << FixItHint::CreateRemoval(DS.getVolatileSpecLoc());
      if (DS.getTypeQualifiers() & DeclSpec::TQ_restrict)
        Diag(DS.getRestrictSpecLoc(),
             diag::ext_anonymous_struct_union_qualified)
          << Record->isUnion() << 2
          << FixItHint::CreateRemoval(DS.getRestrictSpecLoc());

      DS.ClearTypeQualifiers();
    }

    // C++ [class.union]p2:
    //   The member-specification of an anonymous union shall only
    //   define non-static data members. [Note: nested types and
    //   functions cannot be declared within an anonymous union. ]
    for (DeclContext::decl_iterator Mem = Record->decls_begin(),
                                 MemEnd = Record->decls_end();
         Mem != MemEnd; ++Mem) {
      if (FieldDecl *FD = dyn_cast<FieldDecl>(*Mem)) {
        // C++ [class.union]p3:
        //   An anonymous union shall not have private or protected
        //   members (clause 11).
        assert(FD->getAccess() != AS_none);
        if (FD->getAccess() != AS_public) {
          Diag(FD->getLocation(), diag::err_anonymous_record_nonpublic_member)
            << (int)Record->isUnion() << (int)(FD->getAccess() == AS_protected);
          Invalid = true;
        }

        // C++ [class.union]p1
        //   An object of a class with a non-trivial constructor, a non-trivial
        //   copy constructor, a non-trivial destructor, or a non-trivial copy
        //   assignment operator cannot be a member of a union, nor can an
        //   array of such objects.
        if (CheckNontrivialField(FD))
          Invalid = true;
      } else if ((*Mem)->isImplicit()) {
        // Any implicit members are fine.
      } else if (isa<TagDecl>(*Mem) && (*Mem)->getDeclContext() != Record) {
        // This is a type that showed up in an
        // elaborated-type-specifier inside the anonymous struct or
        // union, but which actually declares a type outside of the
        // anonymous struct or union. It's okay.
      } else if (RecordDecl *MemRecord = dyn_cast<RecordDecl>(*Mem)) {
        if (!MemRecord->isAnonymousStructOrUnion() &&
            MemRecord->getDeclName()) {
          // Visual C++ allows type definition in anonymous struct or union.
          if (getLangOpts().MicrosoftExt)
            Diag(MemRecord->getLocation(), diag::ext_anonymous_record_with_type)
              << (int)Record->isUnion();
          else {
            // This is a nested type declaration.
            Diag(MemRecord->getLocation(), diag::err_anonymous_record_with_type)
              << (int)Record->isUnion();
            Invalid = true;
          }
        } else {
          // This is an anonymous type definition within another anonymous type.
          // This is a popular extension, provided by Plan9, MSVC and GCC, but
          // not part of standard C++.
          Diag(MemRecord->getLocation(),
               diag::ext_anonymous_record_with_anonymous_type)
            << (int)Record->isUnion();
        }
      } else if (isa<AccessSpecDecl>(*Mem)) {
        // Any access specifier is fine.
      } else {
        // We have something that isn't a non-static data
        // member. Complain about it.
        unsigned DK = diag::err_anonymous_record_bad_member;
        if (isa<TypeDecl>(*Mem))
          DK = diag::err_anonymous_record_with_type;
        else if (isa<FunctionDecl>(*Mem))
          DK = diag::err_anonymous_record_with_function;
        else if (isa<VarDecl>(*Mem))
          DK = diag::err_anonymous_record_with_static;

        // Visual C++ allows type definition in anonymous struct or union.
        if (getLangOpts().MicrosoftExt &&
            DK == diag::err_anonymous_record_with_type)
          Diag((*Mem)->getLocation(), diag::ext_anonymous_record_with_type)
            << (int)Record->isUnion();
        else {
          Diag((*Mem)->getLocation(), DK)
              << (int)Record->isUnion();
          Invalid = true;
        }
      }
    }
  }

  if (!Record->isUnion() && !Owner->isRecord()) {
    Diag(Record->getLocation(), diag::err_anonymous_struct_not_member)
      << (int)getLangOpts().CPlusPlus;
    Invalid = true;
  }

  // Mock up a declarator.
  Declarator Dc(DS, Declarator::MemberContext);
  TypeSourceInfo *TInfo = GetTypeForDeclarator(Dc, S);
  assert(TInfo && "couldn't build declarator info for anonymous struct/union");

  // Create a declaration for this anonymous struct/union.
  NamedDecl *Anon = 0;
  if (RecordDecl *OwningClass = dyn_cast<RecordDecl>(Owner)) {
    Anon = FieldDecl::Create(Context, OwningClass,
                             DS.getLocStart(),
                             Record->getLocation(),
                             /*IdentifierInfo=*/0,
                             Context.getTypeDeclType(Record),
                             TInfo,
                             /*BitWidth=*/0, /*Mutable=*/false,
                             /*InitStyle=*/ICIS_NoInit);
    Anon->setAccess(AS);
    if (getLangOpts().CPlusPlus)
      FieldCollector->Add(cast<FieldDecl>(Anon));
  } else {
    DeclSpec::SCS SCSpec = DS.getStorageClassSpec();
    assert(SCSpec != DeclSpec::SCS_typedef &&
           "Parser allowed 'typedef' as storage class VarDecl.");
    VarDecl::StorageClass SC = StorageClassSpecToVarDeclStorageClass(SCSpec);
    if (SCSpec == DeclSpec::SCS_mutable) {
      // mutable can only appear on non-static class members, so it's always
      // an error here
      Diag(Record->getLocation(), diag::err_mutable_nonmember);
      Invalid = true;
      SC = SC_None;
    }
    SCSpec = DS.getStorageClassSpecAsWritten();
    VarDecl::StorageClass SCAsWritten
      = StorageClassSpecToVarDeclStorageClass(SCSpec);

    Anon = VarDecl::Create(Context, Owner,
                           DS.getLocStart(),
                           Record->getLocation(), /*IdentifierInfo=*/0,
                           Context.getTypeDeclType(Record),
                           TInfo, SC, SCAsWritten);

    // Default-initialize the implicit variable. This initialization will be
    // trivial in almost all cases, except if a union member has an in-class
    // initializer:
    //   union { int n = 0; };
    ActOnUninitializedDecl(Anon, /*TypeMayContainAuto=*/false);
  }
  Anon->setImplicit();

  // Add the anonymous struct/union object to the current
  // context. We'll be referencing this object when we refer to one of
  // its members.
  Owner->addDecl(Anon);

  // Inject the members of the anonymous struct/union into the owning
  // context and into the identifier resolver chain for name lookup
  // purposes.
  SmallVector<NamedDecl*, 2> Chain;
  Chain.push_back(Anon);

  if (InjectAnonymousStructOrUnionMembers(*this, S, Owner, Record, AS,
                                          Chain, false))
    Invalid = true;

  // Mark this as an anonymous struct/union type. Note that we do not
  // do this until after we have already checked and injected the
  // members of this anonymous struct/union type, because otherwise
  // the members could be injected twice: once by DeclContext when it
  // builds its lookup table, and once by
  // InjectAnonymousStructOrUnionMembers.
  Record->setAnonymousStructOrUnion(true);

  if (Invalid)
    Anon->setInvalidDecl();

  return Anon;
}

/// BuildMicrosoftCAnonymousStruct - Handle the declaration of an
/// Microsoft C anonymous structure.
/// Ref: http://msdn.microsoft.com/en-us/library/z2cx9y4f.aspx
/// Example:
///
/// struct A { int a; };
/// struct B { struct A; int b; };
///
/// void foo() {
///   B var;
///   var.a = 3;
/// }
///
Decl *Sema::BuildMicrosoftCAnonymousStruct(Scope *S, DeclSpec &DS,
                                           RecordDecl *Record) {

  // If there is no Record, get the record via the typedef.
  if (!Record)
    Record = DS.getRepAsType().get()->getAsStructureType()->getDecl();

  // Mock up a declarator.
  Declarator Dc(DS, Declarator::TypeNameContext);
  TypeSourceInfo *TInfo = GetTypeForDeclarator(Dc, S);
  assert(TInfo && "couldn't build declarator info for anonymous struct");

  // Create a declaration for this anonymous struct.
  NamedDecl* Anon = FieldDecl::Create(Context,
                             cast<RecordDecl>(CurContext),
                             DS.getLocStart(),
                             DS.getLocStart(),
                             /*IdentifierInfo=*/0,
                             Context.getTypeDeclType(Record),
                             TInfo,
                             /*BitWidth=*/0, /*Mutable=*/false,
                             /*InitStyle=*/ICIS_NoInit);
  Anon->setImplicit();

  // Add the anonymous struct object to the current context.
  CurContext->addDecl(Anon);

  // Inject the members of the anonymous struct into the current
  // context and into the identifier resolver chain for name lookup
  // purposes.
  SmallVector<NamedDecl*, 2> Chain;
  Chain.push_back(Anon);

  RecordDecl *RecordDef = Record->getDefinition();
  if (!RecordDef || InjectAnonymousStructOrUnionMembers(*this, S, CurContext,
                                                        RecordDef, AS_none,
                                                        Chain, true))
    Anon->setInvalidDecl();

  return Anon;
}

/// GetNameForDeclarator - Determine the full declaration name for the
/// given Declarator.
DeclarationNameInfo Sema::GetNameForDeclarator(Declarator &D) {
  return GetNameFromUnqualifiedId(D.getName());
}

/// \brief Retrieves the declaration name from a parsed unqualified-id.
DeclarationNameInfo
Sema::GetNameFromUnqualifiedId(const UnqualifiedId &Name) {
  DeclarationNameInfo NameInfo;
  NameInfo.setLoc(Name.StartLocation);

  switch (Name.getKind()) {

  case UnqualifiedId::IK_ImplicitSelfParam:
  case UnqualifiedId::IK_Identifier:
    NameInfo.setName(Name.Identifier);
    NameInfo.setLoc(Name.StartLocation);
    return NameInfo;

  case UnqualifiedId::IK_OperatorFunctionId:
    NameInfo.setName(Context.DeclarationNames.getCXXOperatorName(
                                           Name.OperatorFunctionId.Operator));
    NameInfo.setLoc(Name.StartLocation);
    NameInfo.getInfo().CXXOperatorName.BeginOpNameLoc
      = Name.OperatorFunctionId.SymbolLocations[0];
    NameInfo.getInfo().CXXOperatorName.EndOpNameLoc
      = Name.EndLocation.getRawEncoding();
    return NameInfo;

  case UnqualifiedId::IK_LiteralOperatorId:
    NameInfo.setName(Context.DeclarationNames.getCXXLiteralOperatorName(
                                                           Name.Identifier));
    NameInfo.setLoc(Name.StartLocation);
    NameInfo.setCXXLiteralOperatorNameLoc(Name.EndLocation);
    return NameInfo;

  case UnqualifiedId::IK_ConversionFunctionId: {
    TypeSourceInfo *TInfo;
    QualType Ty = GetTypeFromParser(Name.ConversionFunctionId, &TInfo);
    if (Ty.isNull())
      return DeclarationNameInfo();
    NameInfo.setName(Context.DeclarationNames.getCXXConversionFunctionName(
                                               Context.getCanonicalType(Ty)));
    NameInfo.setLoc(Name.StartLocation);
    NameInfo.setNamedTypeInfo(TInfo);
    return NameInfo;
  }

  case UnqualifiedId::IK_ConstructorName: {
    TypeSourceInfo *TInfo;
    QualType Ty = GetTypeFromParser(Name.ConstructorName, &TInfo);
    if (Ty.isNull())
      return DeclarationNameInfo();
    NameInfo.setName(Context.DeclarationNames.getCXXConstructorName(
                                              Context.getCanonicalType(Ty)));
    NameInfo.setLoc(Name.StartLocation);
    NameInfo.setNamedTypeInfo(TInfo);
    return NameInfo;
  }

  case UnqualifiedId::IK_ConstructorTemplateId: {
    // In well-formed code, we can only have a constructor
    // template-id that refers to the current context, so go there
    // to find the actual type being constructed.
    CXXRecordDecl *CurClass = dyn_cast<CXXRecordDecl>(CurContext);
    if (!CurClass || CurClass->getIdentifier() != Name.TemplateId->Name)
      return DeclarationNameInfo();

    // Determine the type of the class being constructed.
    QualType CurClassType = Context.getTypeDeclType(CurClass);

    // FIXME: Check two things: that the template-id names the same type as
    // CurClassType, and that the template-id does not occur when the name
    // was qualified.

    NameInfo.setName(Context.DeclarationNames.getCXXConstructorName(
                                    Context.getCanonicalType(CurClassType)));
    NameInfo.setLoc(Name.StartLocation);
    // FIXME: should we retrieve TypeSourceInfo?
    NameInfo.setNamedTypeInfo(0);
    return NameInfo;
  }

  case UnqualifiedId::IK_DestructorName: {
    TypeSourceInfo *TInfo;
    QualType Ty = GetTypeFromParser(Name.DestructorName, &TInfo);
    if (Ty.isNull())
      return DeclarationNameInfo();
    NameInfo.setName(Context.DeclarationNames.getCXXDestructorName(
                                              Context.getCanonicalType(Ty)));
    NameInfo.setLoc(Name.StartLocation);
    NameInfo.setNamedTypeInfo(TInfo);
    return NameInfo;
  }

  case UnqualifiedId::IK_TemplateId: {
    TemplateName TName = Name.TemplateId->Template.get();
    SourceLocation TNameLoc = Name.TemplateId->TemplateNameLoc;
    return Context.getNameForTemplate(TName, TNameLoc);
  }

  } // switch (Name.getKind())

  llvm_unreachable("Unknown name kind");
}

static QualType getCoreType(QualType Ty) {
  do {
    if (Ty->isPointerType() || Ty->isReferenceType())
      Ty = Ty->getPointeeType();
    else if (Ty->isArrayType())
      Ty = Ty->castAsArrayTypeUnsafe()->getElementType();
    else
      return Ty.withoutLocalFastQualifiers();
  } while (true);
}

/// hasSimilarParameters - Determine whether the C++ functions Declaration
/// and Definition have "nearly" matching parameters. This heuristic is
/// used to improve diagnostics in the case where an out-of-line function
/// definition doesn't match any declaration within the class or namespace.
/// Also sets Params to the list of indices to the parameters that differ
/// between the declaration and the definition. If hasSimilarParameters
/// returns true and Params is empty, then all of the parameters match.
static bool hasSimilarParameters(ASTContext &Context,
                                     FunctionDecl *Declaration,
                                     FunctionDecl *Definition,
                                     SmallVectorImpl<unsigned> &Params) {
  Params.clear();
  if (Declaration->param_size() != Definition->param_size())
    return false;
  for (unsigned Idx = 0; Idx < Declaration->param_size(); ++Idx) {
    QualType DeclParamTy = Declaration->getParamDecl(Idx)->getType();
    QualType DefParamTy = Definition->getParamDecl(Idx)->getType();

    // The parameter types are identical
    if (Context.hasSameType(DefParamTy, DeclParamTy))
      continue;

    QualType DeclParamBaseTy = getCoreType(DeclParamTy);
    QualType DefParamBaseTy = getCoreType(DefParamTy);
    const IdentifierInfo *DeclTyName = DeclParamBaseTy.getBaseTypeIdentifier();
    const IdentifierInfo *DefTyName = DefParamBaseTy.getBaseTypeIdentifier();

    if (Context.hasSameUnqualifiedType(DeclParamBaseTy, DefParamBaseTy) ||
        (DeclTyName && DeclTyName == DefTyName))
      Params.push_back(Idx);
    else  // The two parameters aren't even close
      return false;
  }

  return true;
}

/// NeedsRebuildingInCurrentInstantiation - Checks whether the given
/// declarator needs to be rebuilt in the current instantiation.
/// Any bits of declarator which appear before the name are valid for
/// consideration here.  That's specifically the type in the decl spec
/// and the base type in any member-pointer chunks.
static bool RebuildDeclaratorInCurrentInstantiation(Sema &S, Declarator &D,
                                                    DeclarationName Name) {
  // The types we specifically need to rebuild are:
  //   - typenames, typeofs, and decltypes
  //   - types which will become injected class names
  // Of course, we also need to rebuild any type referencing such a
  // type.  It's safest to just say "dependent", but we call out a
  // few cases here.

  DeclSpec &DS = D.getMutableDeclSpec();
  switch (DS.getTypeSpecType()) {
  case DeclSpec::TST_typename:
  case DeclSpec::TST_typeofType:
  case DeclSpec::TST_underlyingType:
  case DeclSpec::TST_atomic: {
    // Grab the type from the parser.
    TypeSourceInfo *TSI = 0;
    QualType T = S.GetTypeFromParser(DS.getRepAsType(), &TSI);
    if (T.isNull() || !T->isDependentType()) break;

    // Make sure there's a type source info.  This isn't really much
    // of a waste; most dependent types should have type source info
    // attached already.
    if (!TSI)
      TSI = S.Context.getTrivialTypeSourceInfo(T, DS.getTypeSpecTypeLoc());

    // Rebuild the type in the current instantiation.
    TSI = S.RebuildTypeInCurrentInstantiation(TSI, D.getIdentifierLoc(), Name);
    if (!TSI) return true;

    // Store the new type back in the decl spec.
    ParsedType LocType = S.CreateParsedType(TSI->getType(), TSI);
    DS.UpdateTypeRep(LocType);
    break;
  }

  case DeclSpec::TST_decltype:
  case DeclSpec::TST_typeofExpr: {
    Expr *E = DS.getRepAsExpr();
    ExprResult Result = S.RebuildExprInCurrentInstantiation(E);
    if (Result.isInvalid()) return true;
    DS.UpdateExprRep(Result.get());
    break;
  }

  default:
    // Nothing to do for these decl specs.
    break;
  }

  // It doesn't matter what order we do this in.
  for (unsigned I = 0, E = D.getNumTypeObjects(); I != E; ++I) {
    DeclaratorChunk &Chunk = D.getTypeObject(I);

    // The only type information in the declarator which can come
    // before the declaration name is the base type of a member
    // pointer.
    if (Chunk.Kind != DeclaratorChunk::MemberPointer)
      continue;

    // Rebuild the scope specifier in-place.
    CXXScopeSpec &SS = Chunk.Mem.Scope();
    if (S.RebuildNestedNameSpecifierInCurrentInstantiation(SS))
      return true;
  }

  return false;
}

Decl *Sema::ActOnDeclarator(Scope *S, Declarator &D) {
  D.setFunctionDefinitionKind(FDK_Declaration);
  Decl *Dcl = HandleDeclarator(S, D, MultiTemplateParamsArg());

  if (OriginalLexicalContext && OriginalLexicalContext->isObjCContainer() &&
      Dcl && Dcl->getDeclContext()->isFileContext())
    Dcl->setTopLevelDeclInObjCContainer();

  return Dcl;
}

/// DiagnoseClassNameShadow - Implement C++ [class.mem]p13:
///   If T is the name of a class, then each of the following shall have a
///   name different from T:
///     - every static data member of class T;
///     - every member function of class T
///     - every member of class T that is itself a type;
/// \returns true if the declaration name violates these rules.
bool Sema::DiagnoseClassNameShadow(DeclContext *DC,
                                   DeclarationNameInfo NameInfo) {
  DeclarationName Name = NameInfo.getName();

  if (CXXRecordDecl *Record = dyn_cast<CXXRecordDecl>(DC))
    if (Record->getIdentifier() && Record->getDeclName() == Name) {
      Diag(NameInfo.getLoc(), diag::err_member_name_of_class) << Name;
      return true;
    }

  return false;
}

/// \brief Diagnose a declaration whose declarator-id has the given
/// nested-name-specifier.
///
/// \param SS The nested-name-specifier of the declarator-id.
///
/// \param DC The declaration context to which the nested-name-specifier
/// resolves.
///
/// \param Name The name of the entity being declared.
///
/// \param Loc The location of the name of the entity being declared.
///
/// \returns true if we cannot safely recover from this error, false otherwise.
bool Sema::diagnoseQualifiedDeclaration(CXXScopeSpec &SS, DeclContext *DC,
                                        DeclarationName Name,
                                      SourceLocation Loc) {
  DeclContext *Cur = CurContext;
  while (isa<LinkageSpecDecl>(Cur))
    Cur = Cur->getParent();

  // C++ [dcl.meaning]p1:
  //   A declarator-id shall not be qualified except for the definition
  //   of a member function (9.3) or static data member (9.4) outside of
  //   its class, the definition or explicit instantiation of a function
  //   or variable member of a namespace outside of its namespace, or the
  //   definition of an explicit specialization outside of its namespace,
  //   or the declaration of a friend function that is a member of
  //   another class or namespace (11.3). [...]

  // The user provided a superfluous scope specifier that refers back to the
  // class or namespaces in which the entity is already declared.
  //
  // class X {
  //   void X::f();
  // };
  if (Cur->Equals(DC)) {
    Diag(Loc, LangOpts.MicrosoftExt? diag::warn_member_extra_qualification
                                   : diag::err_member_extra_qualification)
      << Name << FixItHint::CreateRemoval(SS.getRange());
    SS.clear();
    return false;
  }

  // Check whether the qualifying scope encloses the scope of the original
  // declaration.
  if (!Cur->Encloses(DC)) {
    if (Cur->isRecord())
      Diag(Loc, diag::err_member_qualification)
        << Name << SS.getRange();
    else if (isa<TranslationUnitDecl>(DC))
      Diag(Loc, diag::err_invalid_declarator_global_scope)
        << Name << SS.getRange();
    else if (isa<FunctionDecl>(Cur))
      Diag(Loc, diag::err_invalid_declarator_in_function)
        << Name << SS.getRange();
    else
      Diag(Loc, diag::err_invalid_declarator_scope)
      << Name << cast<NamedDecl>(Cur) << cast<NamedDecl>(DC) << SS.getRange();

    return true;
  }

  if (Cur->isRecord()) {
    // Cannot qualify members within a class.
    Diag(Loc, diag::err_member_qualification)
      << Name << SS.getRange();
    SS.clear();

    // C++ constructors and destructors with incorrect scopes can break
    // our AST invariants by having the wrong underlying types. If
    // that's the case, then drop this declaration entirely.
    if ((Name.getNameKind() == DeclarationName::CXXConstructorName ||
         Name.getNameKind() == DeclarationName::CXXDestructorName) &&
        !Context.hasSameType(Name.getCXXNameType(),
                             Context.getTypeDeclType(cast<CXXRecordDecl>(Cur))))
      return true;

    return false;
  }

  // C++11 [dcl.meaning]p1:
  //   [...] "The nested-name-specifier of the qualified declarator-id shall
  //   not begin with a decltype-specifer"
  NestedNameSpecifierLoc SpecLoc(SS.getScopeRep(), SS.location_data());
  while (SpecLoc.getPrefix())
    SpecLoc = SpecLoc.getPrefix();
  if (dyn_cast_or_null<DecltypeType>(
        SpecLoc.getNestedNameSpecifier()->getAsType()))
    Diag(Loc, diag::err_decltype_in_declarator)
      << SpecLoc.getTypeLoc().getSourceRange();

  return false;
}

NamedDecl *Sema::HandleDeclarator(Scope *S, Declarator &D,
                                  MultiTemplateParamsArg TemplateParamLists) {
  // TODO: consider using NameInfo for diagnostic.
  DeclarationNameInfo NameInfo = GetNameForDeclarator(D);
  DeclarationName Name = NameInfo.getName();

  // All of these full declarators require an identifier.  If it doesn't have
  // one, the ParsedFreeStandingDeclSpec action should be used.
  if (!Name) {
    if (!D.isInvalidType())  // Reject this if we think it is valid.
      Diag(D.getDeclSpec().getLocStart(),
           diag::err_declarator_need_ident)
        << D.getDeclSpec().getSourceRange() << D.getSourceRange();
    return 0;
  } else if (DiagnoseUnexpandedParameterPack(NameInfo, UPPC_DeclarationType))
    return 0;

  // The scope passed in may not be a decl scope.  Zip up the scope tree until
  // we find one that is.
  while ((S->getFlags() & Scope::DeclScope) == 0 ||
         (S->getFlags() & Scope::TemplateParamScope) != 0)
    S = S->getParent();

  DeclContext *DC = CurContext;
  if (D.getCXXScopeSpec().isInvalid())
    D.setInvalidType();
  else if (D.getCXXScopeSpec().isSet()) {
    if (DiagnoseUnexpandedParameterPack(D.getCXXScopeSpec(),
                                        UPPC_DeclarationQualifier))
      return 0;

    bool EnteringContext = !D.getDeclSpec().isFriendSpecified();
    DC = computeDeclContext(D.getCXXScopeSpec(), EnteringContext);
    if (!DC) {
      // If we could not compute the declaration context, it's because the
      // declaration context is dependent but does not refer to a class,
      // class template, or class template partial specialization. Complain
      // and return early, to avoid the coming semantic disaster.
      Diag(D.getIdentifierLoc(),
           diag::err_template_qualified_declarator_no_match)
        << (NestedNameSpecifier*)D.getCXXScopeSpec().getScopeRep()
        << D.getCXXScopeSpec().getRange();
      return 0;
    }
    bool IsDependentContext = DC->isDependentContext();

    if (!IsDependentContext &&
        RequireCompleteDeclContext(D.getCXXScopeSpec(), DC))
      return 0;

    if (isa<CXXRecordDecl>(DC) && !cast<CXXRecordDecl>(DC)->hasDefinition()) {
      Diag(D.getIdentifierLoc(),
           diag::err_member_def_undefined_record)
        << Name << DC << D.getCXXScopeSpec().getRange();
      D.setInvalidType();
    } else if (!D.getDeclSpec().isFriendSpecified()) {
      if (diagnoseQualifiedDeclaration(D.getCXXScopeSpec(), DC,
                                      Name, D.getIdentifierLoc())) {
        if (DC->isRecord())
          return 0;

        D.setInvalidType();
      }
    }

    // Check whether we need to rebuild the type of the given
    // declaration in the current instantiation.
    if (EnteringContext && IsDependentContext &&
        TemplateParamLists.size() != 0) {
      ContextRAII SavedContext(*this, DC);
      if (RebuildDeclaratorInCurrentInstantiation(*this, D, Name))
        D.setInvalidType();
    }
  }

  if (DiagnoseClassNameShadow(DC, NameInfo))
    // If this is a typedef, we'll end up spewing multiple diagnostics.
    // Just return early; it's safer.
    if (D.getDeclSpec().getStorageClassSpec() == DeclSpec::SCS_typedef)
      return 0;

  TypeSourceInfo *TInfo = GetTypeForDeclarator(D, S);
  QualType R = TInfo->getType();

  if (DiagnoseUnexpandedParameterPack(D.getIdentifierLoc(), TInfo,
                                      UPPC_DeclarationType))
    D.setInvalidType();

  LookupResult Previous(*this, NameInfo, LookupOrdinaryName,
                        ForRedeclaration);

  // See if this is a redefinition of a variable in the same scope.
  if (!D.getCXXScopeSpec().isSet()) {
    bool IsLinkageLookup = false;

    // If the declaration we're planning to build will be a function
    // or object with linkage, then look for another declaration with
    // linkage (C99 6.2.2p4-5 and C++ [basic.link]p6).
    if (D.getDeclSpec().getStorageClassSpec() == DeclSpec::SCS_typedef)
      /* Do nothing*/;
    else if (R->isFunctionType()) {
      if (CurContext->isFunctionOrMethod() ||
          D.getDeclSpec().getStorageClassSpec() != DeclSpec::SCS_static)
        IsLinkageLookup = true;
    } else if (D.getDeclSpec().getStorageClassSpec() == DeclSpec::SCS_extern)
      IsLinkageLookup = true;
    else if (CurContext->getRedeclContext()->isTranslationUnit() &&
             D.getDeclSpec().getStorageClassSpec() != DeclSpec::SCS_static)
      IsLinkageLookup = true;

    if (IsLinkageLookup)
      Previous.clear(LookupRedeclarationWithLinkage);

    LookupName(Previous, S, /* CreateBuiltins = */ IsLinkageLookup);
  } else { // Something like "int foo::x;"
    LookupQualifiedName(Previous, DC);

    // C++ [dcl.meaning]p1:
    //   When the declarator-id is qualified, the declaration shall refer to a
    //  previously declared member of the class or namespace to which the
    //  qualifier refers (or, in the case of a namespace, of an element of the
    //  inline namespace set of that namespace (7.3.1)) or to a specialization
    //  thereof; [...]
    //
    // Note that we already checked the context above, and that we do not have
    // enough information to make sure that Previous contains the declaration
    // we want to match. For example, given:
    //
    //   class X {
    //     void f();
    //     void f(float);
    //   };
    //
    //   void X::f(int) { } // ill-formed
    //
    // In this case, Previous will point to the overload set
    // containing the two f's declared in X, but neither of them
    // matches.

    // C++ [dcl.meaning]p1:
    //   [...] the member shall not merely have been introduced by a
    //   using-declaration in the scope of the class or namespace nominated by
    //   the nested-name-specifier of the declarator-id.
    RemoveUsingDecls(Previous);
  }

  if (Previous.isSingleResult() &&
      Previous.getFoundDecl()->isTemplateParameter()) {
    // Maybe we will complain about the shadowed template parameter.
    if (!D.isInvalidType())
      DiagnoseTemplateParameterShadow(D.getIdentifierLoc(),
                                      Previous.getFoundDecl());

    // Just pretend that we didn't see the previous declaration.
    Previous.clear();
  }

  // In C++, the previous declaration we find might be a tag type
  // (class or enum). In this case, the new declaration will hide the
  // tag type. Note that this does does not apply if we're declaring a
  // typedef (C++ [dcl.typedef]p4).
  if (Previous.isSingleTagDecl() &&
      D.getDeclSpec().getStorageClassSpec() != DeclSpec::SCS_typedef)
    Previous.clear();

  // Check that there are no default arguments other than in the parameters
  // of a function declaration (C++ only).
  if (getLangOpts().CPlusPlus)
    CheckExtraCXXDefaultArguments(D);

  NamedDecl *New;

  bool AddToScope = true;
  if (D.getDeclSpec().getStorageClassSpec() == DeclSpec::SCS_typedef) {
    if (TemplateParamLists.size()) {
      Diag(D.getIdentifierLoc(), diag::err_template_typedef);
      return 0;
    }

    New = ActOnTypedefDeclarator(S, D, DC, TInfo, Previous);
  } else if (R->isFunctionType()) {
    New = ActOnFunctionDeclarator(S, D, DC, TInfo, Previous,
                                  TemplateParamLists,
                                  AddToScope);
  } else {
    New = ActOnVariableDeclarator(S, D, DC, TInfo, Previous,
                                  TemplateParamLists);
  }

  if (New == 0)
    return 0;

  // If this has an identifier and is not an invalid redeclaration or
  // function template specialization, add it to the scope stack.
  if (New->getDeclName() && AddToScope &&
       !(D.isRedeclaration() && New->isInvalidDecl()))
    PushOnScopeChains(New, S);

  return New;
}

/// Helper method to turn variable array types into constant array
/// types in certain situations which would otherwise be errors (for
/// GCC compatibility).
static QualType TryToFixInvalidVariablyModifiedType(QualType T,
                                                    ASTContext &Context,
                                                    bool &SizeIsNegative,
                                                    llvm::APSInt &Oversized) {
  // This method tries to turn a variable array into a constant
  // array even when the size isn't an ICE.  This is necessary
  // for compatibility with code that depends on gcc's buggy
  // constant expression folding, like struct {char x[(int)(char*)2];}
  SizeIsNegative = false;
  Oversized = 0;

  if (T->isDependentType())
    return QualType();

  QualifierCollector Qs;
  const Type *Ty = Qs.strip(T);

  if (const PointerType* PTy = dyn_cast<PointerType>(Ty)) {
    QualType Pointee = PTy->getPointeeType();
    QualType FixedType =
        TryToFixInvalidVariablyModifiedType(Pointee, Context, SizeIsNegative,
                                            Oversized);
    if (FixedType.isNull()) return FixedType;
    FixedType = Context.getPointerType(FixedType);
    return Qs.apply(Context, FixedType);
  }
  if (const ParenType* PTy = dyn_cast<ParenType>(Ty)) {
    QualType Inner = PTy->getInnerType();
    QualType FixedType =
        TryToFixInvalidVariablyModifiedType(Inner, Context, SizeIsNegative,
                                            Oversized);
    if (FixedType.isNull()) return FixedType;
    FixedType = Context.getParenType(FixedType);
    return Qs.apply(Context, FixedType);
  }

  const VariableArrayType* VLATy = dyn_cast<VariableArrayType>(T);
  if (!VLATy)
    return QualType();
  // FIXME: We should probably handle this case
  if (VLATy->getElementType()->isVariablyModifiedType())
    return QualType();

  llvm::APSInt Res;
  if (!VLATy->getSizeExpr() ||
      !VLATy->getSizeExpr()->EvaluateAsInt(Res, Context))
    return QualType();

  // Check whether the array size is negative.
  if (Res.isSigned() && Res.isNegative()) {
    SizeIsNegative = true;
    return QualType();
  }

  // Check whether the array is too large to be addressed.
  unsigned ActiveSizeBits
    = ConstantArrayType::getNumAddressingBits(Context, VLATy->getElementType(),
                                              Res);
  if (ActiveSizeBits > ConstantArrayType::getMaxSizeBits(Context)) {
    Oversized = Res;
    return QualType();
  }

  return Context.getConstantArrayType(VLATy->getElementType(),
                                      Res, ArrayType::Normal, 0);
}

static void
FixInvalidVariablyModifiedTypeLoc(TypeLoc SrcTL, TypeLoc DstTL) {
  if (PointerTypeLoc SrcPTL = SrcTL.getAs<PointerTypeLoc>()) {
    PointerTypeLoc DstPTL = DstTL.castAs<PointerTypeLoc>();
    FixInvalidVariablyModifiedTypeLoc(SrcPTL.getPointeeLoc(),
                                      DstPTL.getPointeeLoc());
    DstPTL.setStarLoc(SrcPTL.getStarLoc());
    return;
  }
  if (ParenTypeLoc SrcPTL = SrcTL.getAs<ParenTypeLoc>()) {
    ParenTypeLoc DstPTL = DstTL.castAs<ParenTypeLoc>();
    FixInvalidVariablyModifiedTypeLoc(SrcPTL.getInnerLoc(),
                                      DstPTL.getInnerLoc());
    DstPTL.setLParenLoc(SrcPTL.getLParenLoc());
    DstPTL.setRParenLoc(SrcPTL.getRParenLoc());
    return;
  }
  ArrayTypeLoc SrcATL = SrcTL.castAs<ArrayTypeLoc>();
  ArrayTypeLoc DstATL = DstTL.castAs<ArrayTypeLoc>();
  TypeLoc SrcElemTL = SrcATL.getElementLoc();
  TypeLoc DstElemTL = DstATL.getElementLoc();
  DstElemTL.initializeFullCopy(SrcElemTL);
  DstATL.setLBracketLoc(SrcATL.getLBracketLoc());
  DstATL.setSizeExpr(SrcATL.getSizeExpr());
  DstATL.setRBracketLoc(SrcATL.getRBracketLoc());
}

/// Helper method to turn variable array types into constant array
/// types in certain situations which would otherwise be errors (for
/// GCC compatibility).
static TypeSourceInfo*
TryToFixInvalidVariablyModifiedTypeSourceInfo(TypeSourceInfo *TInfo,
                                              ASTContext &Context,
                                              bool &SizeIsNegative,
                                              llvm::APSInt &Oversized) {
  QualType FixedTy
    = TryToFixInvalidVariablyModifiedType(TInfo->getType(), Context,
                                          SizeIsNegative, Oversized);
  if (FixedTy.isNull())
    return 0;
  TypeSourceInfo *FixedTInfo = Context.getTrivialTypeSourceInfo(FixedTy);
  FixInvalidVariablyModifiedTypeLoc(TInfo->getTypeLoc(),
                                    FixedTInfo->getTypeLoc());
  return FixedTInfo;
}

/// \brief Register the given locally-scoped extern "C" declaration so
/// that it can be found later for redeclarations
void
Sema::RegisterLocallyScopedExternCDecl(NamedDecl *ND,
                                       const LookupResult &Previous,
                                       Scope *S) {
  assert(ND->getLexicalDeclContext()->isFunctionOrMethod() &&
         "Decl is not a locally-scoped decl!");
  // Note that we have a locally-scoped external with this name.
  LocallyScopedExternCDecls[ND->getDeclName()] = ND;

  if (!Previous.isSingleResult())
    return;

  NamedDecl *PrevDecl = Previous.getFoundDecl();

  // If there was a previous declaration of this entity, it may be in
  // our identifier chain. Update the identifier chain with the new
  // declaration.
  if (S && IdResolver.ReplaceDecl(PrevDecl, ND)) {
    // The previous declaration was found on the identifer resolver
    // chain, so remove it from its scope.

    if (S->isDeclScope(PrevDecl)) {
      // Special case for redeclarations in the SAME scope.
      // Because this declaration is going to be added to the identifier chain
      // later, we should temporarily take it OFF the chain.
      IdResolver.RemoveDecl(ND);

    } else {
      // Find the scope for the original declaration.
      while (S && !S->isDeclScope(PrevDecl))
        S = S->getParent();
    }

    if (S)
      S->RemoveDecl(PrevDecl);
  }
}

llvm::DenseMap<DeclarationName, NamedDecl *>::iterator
Sema::findLocallyScopedExternCDecl(DeclarationName Name) {
  if (ExternalSource) {
    // Load locally-scoped external decls from the external source.
    SmallVector<NamedDecl *, 4> Decls;
    ExternalSource->ReadLocallyScopedExternCDecls(Decls);
    for (unsigned I = 0, N = Decls.size(); I != N; ++I) {
      llvm::DenseMap<DeclarationName, NamedDecl *>::iterator Pos
        = LocallyScopedExternCDecls.find(Decls[I]->getDeclName());
      if (Pos == LocallyScopedExternCDecls.end())
        LocallyScopedExternCDecls[Decls[I]->getDeclName()] = Decls[I];
    }
  }

  return LocallyScopedExternCDecls.find(Name);
}

/// \brief Diagnose function specifiers on a declaration of an identifier that
/// does not identify a function.
void Sema::DiagnoseFunctionSpecifiers(const DeclSpec &DS) {
  // FIXME: We should probably indicate the identifier in question to avoid
  // confusion for constructs like "inline int a(), b;"
  if (DS.isInlineSpecified())
    Diag(DS.getInlineSpecLoc(),
         diag::err_inline_non_function);

  if (DS.isVirtualSpecified())
    Diag(DS.getVirtualSpecLoc(),
         diag::err_virtual_non_function);

  if (DS.isExplicitSpecified())
    Diag(DS.getExplicitSpecLoc(),
         diag::err_explicit_non_function);

  if (DS.isNoreturnSpecified())
    Diag(DS.getNoreturnSpecLoc(),
         diag::err_noreturn_non_function);
}

NamedDecl*
Sema::ActOnTypedefDeclarator(Scope* S, Declarator& D, DeclContext* DC,
                             TypeSourceInfo *TInfo, LookupResult &Previous) {
  // Typedef declarators cannot be qualified (C++ [dcl.meaning]p1).
  if (D.getCXXScopeSpec().isSet()) {
    Diag(D.getIdentifierLoc(), diag::err_qualified_typedef_declarator)
      << D.getCXXScopeSpec().getRange();
    D.setInvalidType();
    // Pretend we didn't see the scope specifier.
    DC = CurContext;
    Previous.clear();
  }

  DiagnoseFunctionSpecifiers(D.getDeclSpec());

  if (D.getDeclSpec().isThreadSpecified())
    Diag(D.getDeclSpec().getThreadSpecLoc(), diag::err_invalid_thread);
  if (D.getDeclSpec().isConstexprSpecified())
    Diag(D.getDeclSpec().getConstexprSpecLoc(), diag::err_invalid_constexpr)
      << 1;

  if (D.getName().Kind != UnqualifiedId::IK_Identifier) {
    Diag(D.getName().StartLocation, diag::err_typedef_not_identifier)
      << D.getName().getSourceRange();
    return 0;
  }

  TypedefDecl *NewTD = ParseTypedefDecl(S, D, TInfo->getType(), TInfo);
  if (!NewTD) return 0;

  // Handle attributes prior to checking for duplicates in MergeVarDecl
  ProcessDeclAttributes(S, NewTD, D);

  CheckTypedefForVariablyModifiedType(S, NewTD);

  bool Redeclaration = D.isRedeclaration();
  NamedDecl *ND = ActOnTypedefNameDecl(S, DC, NewTD, Previous, Redeclaration);
  D.setRedeclaration(Redeclaration);
  return ND;
}

void
Sema::CheckTypedefForVariablyModifiedType(Scope *S, TypedefNameDecl *NewTD) {
  // C99 6.7.7p2: If a typedef name specifies a variably modified type
  // then it shall have block scope.
  // Note that variably modified types must be fixed before merging the decl so
  // that redeclarations will match.
  TypeSourceInfo *TInfo = NewTD->getTypeSourceInfo();
  QualType T = TInfo->getType();
  if (T->isVariablyModifiedType()) {
    getCurFunction()->setHasBranchProtectedScope();

    if (S->getFnParent() == 0) {
      bool SizeIsNegative;
      llvm::APSInt Oversized;
      TypeSourceInfo *FixedTInfo =
        TryToFixInvalidVariablyModifiedTypeSourceInfo(TInfo, Context,
                                                      SizeIsNegative,
                                                      Oversized);
      if (FixedTInfo) {
        Diag(NewTD->getLocation(), diag::warn_illegal_constant_array_size);
        NewTD->setTypeSourceInfo(FixedTInfo);
      } else {
        if (SizeIsNegative)
          Diag(NewTD->getLocation(), diag::err_typecheck_negative_array_size);
        else if (T->isVariableArrayType())
          Diag(NewTD->getLocation(), diag::err_vla_decl_in_file_scope);
        else if (Oversized.getBoolValue())
          Diag(NewTD->getLocation(), diag::err_array_too_large)
            << Oversized.toString(10);
        else
          Diag(NewTD->getLocation(), diag::err_vm_decl_in_file_scope);
        NewTD->setInvalidDecl();
      }
    }
  }
}


/// ActOnTypedefNameDecl - Perform semantic checking for a declaration which
/// declares a typedef-name, either using the 'typedef' type specifier or via
/// a C++0x [dcl.typedef]p2 alias-declaration: 'using T = A;'.
NamedDecl*
Sema::ActOnTypedefNameDecl(Scope *S, DeclContext *DC, TypedefNameDecl *NewTD,
                           LookupResult &Previous, bool &Redeclaration) {
  // Merge the decl with the existing one if appropriate. If the decl is
  // in an outer scope, it isn't the same thing.
  FilterLookupForScope(Previous, DC, S, /*ConsiderLinkage*/ false,
                       /*ExplicitInstantiationOrSpecialization=*/false);
  filterNonConflictingPreviousDecls(Context, NewTD, Previous);
  if (!Previous.empty()) {
    Redeclaration = true;
    MergeTypedefNameDecl(NewTD, Previous);
  }

  // If this is the C FILE type, notify the AST context.
  if (IdentifierInfo *II = NewTD->getIdentifier())
    if (!NewTD->isInvalidDecl() &&
        NewTD->getDeclContext()->getRedeclContext()->isTranslationUnit()) {
      if (II->isStr("FILE"))
        Context.setFILEDecl(NewTD);
      else if (II->isStr("jmp_buf"))
        Context.setjmp_bufDecl(NewTD);
      else if (II->isStr("sigjmp_buf"))
        Context.setsigjmp_bufDecl(NewTD);
      else if (II->isStr("ucontext_t"))
        Context.setucontext_tDecl(NewTD);
    }

  return NewTD;
}

/// \brief Determines whether the given declaration is an out-of-scope
/// previous declaration.
///
/// This routine should be invoked when name lookup has found a
/// previous declaration (PrevDecl) that is not in the scope where a
/// new declaration by the same name is being introduced. If the new
/// declaration occurs in a local scope, previous declarations with
/// linkage may still be considered previous declarations (C99
/// 6.2.2p4-5, C++ [basic.link]p6).
///
/// \param PrevDecl the previous declaration found by name
/// lookup
///
/// \param DC the context in which the new declaration is being
/// declared.
///
/// \returns true if PrevDecl is an out-of-scope previous declaration
/// for a new delcaration with the same name.
static bool
isOutOfScopePreviousDeclaration(NamedDecl *PrevDecl, DeclContext *DC,
                                ASTContext &Context) {
  if (!PrevDecl)
    return false;

  if (!PrevDecl->hasLinkage())
    return false;

  if (Context.getLangOpts().CPlusPlus) {
    // C++ [basic.link]p6:
    //   If there is a visible declaration of an entity with linkage
    //   having the same name and type, ignoring entities declared
    //   outside the innermost enclosing namespace scope, the block
    //   scope declaration declares that same entity and receives the
    //   linkage of the previous declaration.
    DeclContext *OuterContext = DC->getRedeclContext();
    if (!OuterContext->isFunctionOrMethod())
      // This rule only applies to block-scope declarations.
      return false;

    DeclContext *PrevOuterContext = PrevDecl->getDeclContext();
    if (PrevOuterContext->isRecord())
      // We found a member function: ignore it.
      return false;

    // Find the innermost enclosing namespace for the new and
    // previous declarations.
    OuterContext = OuterContext->getEnclosingNamespaceContext();
    PrevOuterContext = PrevOuterContext->getEnclosingNamespaceContext();

    // The previous declaration is in a different namespace, so it
    // isn't the same function.
    if (!OuterContext->Equals(PrevOuterContext))
      return false;
  }

  return true;
}

static void SetNestedNameSpecifier(DeclaratorDecl *DD, Declarator &D) {
  CXXScopeSpec &SS = D.getCXXScopeSpec();
  if (!SS.isSet()) return;
  DD->setQualifierInfo(SS.getWithLocInContext(DD->getASTContext()));
}

bool Sema::inferObjCARCLifetime(ValueDecl *decl) {
  QualType type = decl->getType();
  Qualifiers::ObjCLifetime lifetime = type.getObjCLifetime();
  if (lifetime == Qualifiers::OCL_Autoreleasing) {
    // Various kinds of declaration aren't allowed to be __autoreleasing.
    unsigned kind = -1U;
    if (VarDecl *var = dyn_cast<VarDecl>(decl)) {
      if (var->hasAttr<BlocksAttr>())
        kind = 0; // __block
      else if (!var->hasLocalStorage())
        kind = 1; // global
    } else if (isa<ObjCIvarDecl>(decl)) {
      kind = 3; // ivar
    } else if (isa<FieldDecl>(decl)) {
      kind = 2; // field
    }

    if (kind != -1U) {
      Diag(decl->getLocation(), diag::err_arc_autoreleasing_var)
        << kind;
    }
  } else if (lifetime == Qualifiers::OCL_None) {
    // Try to infer lifetime.
    if (!type->isObjCLifetimeType())
      return false;

    lifetime = type->getObjCARCImplicitLifetime();
    type = Context.getLifetimeQualifiedType(type, lifetime);
    decl->setType(type);
  }

  if (VarDecl *var = dyn_cast<VarDecl>(decl)) {
    // Thread-local variables cannot have lifetime.
    if (lifetime && lifetime != Qualifiers::OCL_ExplicitNone &&
        var->isThreadSpecified()) {
      Diag(var->getLocation(), diag::err_arc_thread_ownership)
        << var->getType();
      return true;
    }
  }

  return false;
}

static void checkAttributesAfterMerging(Sema &S, NamedDecl &ND) {
  // 'weak' only applies to declarations with external linkage.
  if (WeakAttr *Attr = ND.getAttr<WeakAttr>()) {
    if (ND.getLinkage() != ExternalLinkage) {
      S.Diag(Attr->getLocation(), diag::err_attribute_weak_static);
      ND.dropAttr<WeakAttr>();
    }
  }
  if (WeakRefAttr *Attr = ND.getAttr<WeakRefAttr>()) {
    if (ND.hasExternalLinkage()) {
      S.Diag(Attr->getLocation(), diag::err_attribute_weakref_not_static);
      ND.dropAttr<WeakRefAttr>();
    }
  }
}

static bool shouldConsiderLinkage(const VarDecl *VD) {
  const DeclContext *DC = VD->getDeclContext()->getRedeclContext();
  if (DC->isFunctionOrMethod())
    return VD->hasExternalStorageAsWritten();
  if (DC->isFileContext())
    return true;
  if (DC->isRecord())
    return false;
  llvm_unreachable("Unexpected context");
}

static bool shouldConsiderLinkage(const FunctionDecl *FD) {
  const DeclContext *DC = FD->getDeclContext()->getRedeclContext();
  if (DC->isFileContext() || DC->isFunctionOrMethod())
    return true;
  if (DC->isRecord())
    return false;
  llvm_unreachable("Unexpected context");
}

NamedDecl*
Sema::ActOnVariableDeclarator(Scope *S, Declarator &D, DeclContext *DC,
                              TypeSourceInfo *TInfo, LookupResult &Previous,
                              MultiTemplateParamsArg TemplateParamLists) {
  QualType R = TInfo->getType();
  DeclarationName Name = GetNameForDeclarator(D).getName();

  DeclSpec::SCS SCSpec = D.getDeclSpec().getStorageClassSpec();
  assert(SCSpec != DeclSpec::SCS_typedef &&
         "Parser allowed 'typedef' as storage class VarDecl.");
  VarDecl::StorageClass SC = StorageClassSpecToVarDeclStorageClass(SCSpec);

  if (getLangOpts().OpenCL && !getOpenCLOptions().cl_khr_fp16)
  {
    // OpenCL v1.2 s6.1.1.1: reject declaring variables of the half and
    // half array type (unless the cl_khr_fp16 extension is enabled).
    if (Context.getBaseElementType(R)->isHalfType()) {
      Diag(D.getIdentifierLoc(), diag::err_opencl_half_declaration) << R;
      D.setInvalidType();
    }
  }

  if (SCSpec == DeclSpec::SCS_mutable) {
    // mutable can only appear on non-static class members, so it's always
    // an error here
    Diag(D.getIdentifierLoc(), diag::err_mutable_nonmember);
    D.setInvalidType();
    SC = SC_None;
  }
  SCSpec = D.getDeclSpec().getStorageClassSpecAsWritten();
  VarDecl::StorageClass SCAsWritten
    = StorageClassSpecToVarDeclStorageClass(SCSpec);

  IdentifierInfo *II = Name.getAsIdentifierInfo();
  if (!II) {
    Diag(D.getIdentifierLoc(), diag::err_bad_variable_name)
      << Name;
    return 0;
  }

  DiagnoseFunctionSpecifiers(D.getDeclSpec());

  if (!DC->isRecord() && S->getFnParent() == 0) {
    // C99 6.9p2: The storage-class specifiers auto and register shall not
    // appear in the declaration specifiers in an external declaration.
    if (SC == SC_Auto || SC == SC_Register) {

      // If this is a register variable with an asm label specified, then this
      // is a GNU extension.
      if (SC == SC_Register && D.getAsmLabel())
        Diag(D.getIdentifierLoc(), diag::err_unsupported_global_register);
      else
        Diag(D.getIdentifierLoc(), diag::err_typecheck_sclass_fscope);
      D.setInvalidType();
    }
  }

  if (getLangOpts().OpenCL) {
    // Set up the special work-group-local storage class for variables in the
    // OpenCL __local address space.
    if (R.getAddressSpace() == LangAS::opencl_local) {
      SC = SC_OpenCLWorkGroupLocal;
      SCAsWritten = SC_OpenCLWorkGroupLocal;
    }

    // OpenCL v1.2 s6.9.b p4:
    // The sampler type cannot be used with the __local and __global address
    // space qualifiers.
    if (R->isSamplerT() && (R.getAddressSpace() == LangAS::opencl_local ||
      R.getAddressSpace() == LangAS::opencl_global)) {
      Diag(D.getIdentifierLoc(), diag::err_wrong_sampler_addressspace);
    }

    // OpenCL 1.2 spec, p6.9 r:
    // The event type cannot be used to declare a program scope variable.
    // The event type cannot be used with the __local, __constant and __global
    // address space qualifiers.
    if (R->isEventT()) {
      if (S->getParent() == 0) {
        Diag(D.getLocStart(), diag::err_event_t_global_var);
        D.setInvalidType();
      }

      if (R.getAddressSpace()) {
        Diag(D.getLocStart(), diag::err_event_t_addr_space_qual);
        D.setInvalidType();
      }
    }
  }

  bool isExplicitSpecialization = false;
  VarDecl *NewVD;
  if (!getLangOpts().CPlusPlus) {
    NewVD = VarDecl::Create(Context, DC, D.getLocStart(),
                            D.getIdentifierLoc(), II,
                            R, TInfo, SC, SCAsWritten);

    if (D.isInvalidType())
      NewVD->setInvalidDecl();
  } else {
    if (DC->isRecord() && !CurContext->isRecord()) {
      // This is an out-of-line definition of a static data member.
      if (SC == SC_Static) {
        Diag(D.getDeclSpec().getStorageClassSpecLoc(),
             diag::err_static_out_of_line)
          << FixItHint::CreateRemoval(D.getDeclSpec().getStorageClassSpecLoc());
      } else if (SC == SC_None)
        SC = SC_Static;
    }
    if (SC == SC_Static && CurContext->isRecord()) {
      if (const CXXRecordDecl *RD = dyn_cast<CXXRecordDecl>(DC)) {
        if (RD->isLocalClass())
          Diag(D.getIdentifierLoc(),
               diag::err_static_data_member_not_allowed_in_local_class)
            << Name << RD->getDeclName();

        // C++98 [class.union]p1: If a union contains a static data member,
        // the program is ill-formed. C++11 drops this restriction.
        if (RD->isUnion())
          Diag(D.getIdentifierLoc(),
               getLangOpts().CPlusPlus11
                 ? diag::warn_cxx98_compat_static_data_member_in_union
                 : diag::ext_static_data_member_in_union) << Name;
        // We conservatively disallow static data members in anonymous structs.
        else if (!RD->getDeclName())
          Diag(D.getIdentifierLoc(),
               diag::err_static_data_member_not_allowed_in_anon_struct)
            << Name << RD->isUnion();
      }
    }

    // Match up the template parameter lists with the scope specifier, then
    // determine whether we have a template or a template specialization.
    isExplicitSpecialization = false;
    bool Invalid = false;
    if (TemplateParameterList *TemplateParams
        = MatchTemplateParametersToScopeSpecifier(
                                  D.getDeclSpec().getLocStart(),
                                                  D.getIdentifierLoc(),
                                                  D.getCXXScopeSpec(),
                                                  TemplateParamLists.data(),
                                                  TemplateParamLists.size(),
                                                  /*never a friend*/ false,
                                                  isExplicitSpecialization,
                                                  Invalid)) {
      if (TemplateParams->size() > 0) {
        // There is no such thing as a variable template.
        Diag(D.getIdentifierLoc(), diag::err_template_variable)
          << II
          << SourceRange(TemplateParams->getTemplateLoc(),
                         TemplateParams->getRAngleLoc());
        return 0;
      } else {
        // There is an extraneous 'template<>' for this variable. Complain
        // about it, but allow the declaration of the variable.
        Diag(TemplateParams->getTemplateLoc(),
             diag::err_template_variable_noparams)
          << II
          << SourceRange(TemplateParams->getTemplateLoc(),
                         TemplateParams->getRAngleLoc());
      }
    }

    NewVD = VarDecl::Create(Context, DC, D.getLocStart(),
                            D.getIdentifierLoc(), II,
                            R, TInfo, SC, SCAsWritten);

    // If this decl has an auto type in need of deduction, make a note of the
    // Decl so we can diagnose uses of it in its own initializer.
    if (D.getDeclSpec().getTypeSpecType() == DeclSpec::TST_auto &&
        R->getContainedAutoType())
      ParsingInitForAutoVars.insert(NewVD);

    if (D.isInvalidType() || Invalid)
      NewVD->setInvalidDecl();

    SetNestedNameSpecifier(NewVD, D);

    if (TemplateParamLists.size() > 0 && D.getCXXScopeSpec().isSet()) {
      NewVD->setTemplateParameterListsInfo(Context,
                                           TemplateParamLists.size(),
                                           TemplateParamLists.data());
    }

    if (D.getDeclSpec().isConstexprSpecified())
      NewVD->setConstexpr(true);
  }

  // Set the lexical context. If the declarator has a C++ scope specifier, the
  // lexical context will be different from the semantic context.
  NewVD->setLexicalDeclContext(CurContext);

  if (D.getDeclSpec().isThreadSpecified()) {
    if (NewVD->hasLocalStorage())
      Diag(D.getDeclSpec().getThreadSpecLoc(), diag::err_thread_non_global);
    else if (!Context.getTargetInfo().isTLSSupported())
      Diag(D.getDeclSpec().getThreadSpecLoc(), diag::err_thread_unsupported);
    else
      NewVD->setThreadSpecified(true);
  }

  if (D.getDeclSpec().isModulePrivateSpecified()) {
    if (isExplicitSpecialization)
      Diag(NewVD->getLocation(), diag::err_module_private_specialization)
        << 2
        << FixItHint::CreateRemoval(D.getDeclSpec().getModulePrivateSpecLoc());
    else if (NewVD->hasLocalStorage())
      Diag(NewVD->getLocation(), diag::err_module_private_local)
        << 0 << NewVD->getDeclName()
        << SourceRange(D.getDeclSpec().getModulePrivateSpecLoc())
        << FixItHint::CreateRemoval(D.getDeclSpec().getModulePrivateSpecLoc());
    else
      NewVD->setModulePrivate();
  }

  // Handle attributes prior to checking for duplicates in MergeVarDecl
  ProcessDeclAttributes(S, NewVD, D);

  if (NewVD->hasAttrs())
    CheckAlignasUnderalignment(NewVD);

  if (getLangOpts().CUDA) {
    // CUDA B.2.5: "__shared__ and __constant__ variables have implied static
    // storage [duration]."
    if (SC == SC_None && S->getFnParent() != 0 &&
        (NewVD->hasAttr<CUDASharedAttr>() ||
         NewVD->hasAttr<CUDAConstantAttr>())) {
      NewVD->setStorageClass(SC_Static);
      NewVD->setStorageClassAsWritten(SC_Static);
    }
  }

  // In auto-retain/release, infer strong retension for variables of
  // retainable type.
  if (getLangOpts().ObjCAutoRefCount && inferObjCARCLifetime(NewVD))
    NewVD->setInvalidDecl();

  // Handle GNU asm-label extension (encoded as an attribute).
  if (Expr *E = (Expr*)D.getAsmLabel()) {
    // The parser guarantees this is a string.
    StringLiteral *SE = cast<StringLiteral>(E);
    StringRef Label = SE->getString();
    if (S->getFnParent() != 0) {
      switch (SC) {
      case SC_None:
      case SC_Auto:
        Diag(E->getExprLoc(), diag::warn_asm_label_on_auto_decl) << Label;
        break;
      case SC_Register:
        if (!Context.getTargetInfo().isValidGCCRegisterName(Label))
          Diag(E->getExprLoc(), diag::err_asm_unknown_register_name) << Label;
        break;
      case SC_Static:
      case SC_Extern:
      case SC_PrivateExtern:
      case SC_OpenCLWorkGroupLocal:
        break;
      }
    }

    NewVD->addAttr(::new (Context) AsmLabelAttr(SE->getStrTokenLoc(0),
                                                Context, Label));
  } else if (!ExtnameUndeclaredIdentifiers.empty()) {
    llvm::DenseMap<IdentifierInfo*,AsmLabelAttr*>::