lib/AST/DeclBase.cpp

//===--- DeclBase.cpp - Declaration AST Node Implementation ---------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the Decl and DeclContext classes.
//
//===----------------------------------------------------------------------===//

#include "clang/AST/DeclBase.h"
#include "clang/AST/Decl.h"
#include "clang/AST/DeclContextInternals.h"
#include "clang/AST/DeclCXX.h"
#include "clang/AST/DeclFriend.h"
#include "clang/AST/DeclObjC.h"
#include "clang/AST/DeclTemplate.h"
#include "clang/AST/DependentDiagnostic.h"
#include "clang/AST/ExternalASTSource.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/Type.h"
#include "clang/AST/Stmt.h"
#include "clang/AST/StmtCXX.h"
#include "clang/AST/ASTMutationListener.h"
#include "clang/Basic/TargetInfo.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/Support/raw_ostream.h"
#include <algorithm>
using namespace clang;

//===----------------------------------------------------------------------===//
//  Statistics
//===----------------------------------------------------------------------===//

#define DECL(DERIVED, BASE) static int n##DERIVED##s = 0;
#define ABSTRACT_DECL(DECL)
#include "clang/AST/DeclNodes.inc"

static bool StatSwitch = false;

const char *Decl::getDeclKindName() const {
  switch (DeclKind) {
  default: assert(0 && "Declaration not in DeclNodes.inc!");
#define DECL(DERIVED, BASE) case DERIVED: return #DERIVED;
#define ABSTRACT_DECL(DECL)
#include "clang/AST/DeclNodes.inc"
  }
}

void Decl::setInvalidDecl(bool Invalid) {
  InvalidDecl = Invalid;
  if (Invalid) {
    // Defensive maneuver for ill-formed code: we're likely not to make it to
    // a point where we set the access specifier, so default it to "public"
    // to avoid triggering asserts elsewhere in the front end.
    setAccess(AS_public);
  }
}

const char *DeclContext::getDeclKindName() const {
  switch (DeclKind) {
  default: assert(0 && "Declaration context not in DeclNodes.inc!");
#define DECL(DERIVED, BASE) case Decl::DERIVED: return #DERIVED;
#define ABSTRACT_DECL(DECL)
#include "clang/AST/DeclNodes.inc"
  }
}

bool Decl::CollectingStats(bool Enable) {
  if (Enable) StatSwitch = true;
  return StatSwitch;
}

void Decl::PrintStats() {
  llvm::errs() << "\n*** Decl Stats:\n";

  int totalDecls = 0;
#define DECL(DERIVED, BASE) totalDecls += n##DERIVED##s;
#define ABSTRACT_DECL(DECL)
#include "clang/AST/DeclNodes.inc"
  llvm::errs() << "  " << totalDecls << " decls total.\n";

  int totalBytes = 0;
#define DECL(DERIVED, BASE)                                             \
  if (n##DERIVED##s > 0) {                                              \
    totalBytes += (int)(n##DERIVED##s * sizeof(DERIVED##Decl));         \
    llvm::errs() << "    " << n##DERIVED##s << " " #DERIVED " decls, "  \
                 << sizeof(DERIVED##Decl) << " each ("                  \
                 << n##DERIVED##s * sizeof(DERIVED##Decl)               \
                 << " bytes)\n";                                        \
  }
#define ABSTRACT_DECL(DECL)
#include "clang/AST/DeclNodes.inc"

  llvm::errs() << "Total bytes = " << totalBytes << "\n";
}

void Decl::add(Kind k) {
  switch (k) {
  default: assert(0 && "Declaration not in DeclNodes.inc!");
#define DECL(DERIVED, BASE) case DERIVED: ++n##DERIVED##s; break;
#define ABSTRACT_DECL(DECL)
#include "clang/AST/DeclNodes.inc"
  }
}

bool Decl::isTemplateParameterPack() const {
  if (const TemplateTypeParmDecl *TTP = dyn_cast<TemplateTypeParmDecl>(this))
    return TTP->isParameterPack();
  if (const NonTypeTemplateParmDecl *NTTP
                                = dyn_cast<NonTypeTemplateParmDecl>(this))
    return NTTP->isParameterPack();
  if (const TemplateTemplateParmDecl *TTP
                                    = dyn_cast<TemplateTemplateParmDecl>(this))
    return TTP->isParameterPack();
  return false;
}

bool Decl::isParameterPack() const {
  if (const ParmVarDecl *Parm = dyn_cast<ParmVarDecl>(this))
    return Parm->isParameterPack();

  return isTemplateParameterPack();
}

bool Decl::isFunctionOrFunctionTemplate() const {
  if (const UsingShadowDecl *UD = dyn_cast<UsingShadowDecl>(this))
    return UD->getTargetDecl()->isFunctionOrFunctionTemplate();

  return isa<FunctionDecl>(this) || isa<FunctionTemplateDecl>(this);
}

bool Decl::isTemplateDecl() const {
  return isa<TemplateDecl>(this);
}

bool Decl::isDefinedOutsideFunctionOrMethod() const {
  for (const DeclContext *DC = getDeclContext();
       DC && !DC->isTranslationUnit();
       DC = DC->getParent())
    if (DC->isFunctionOrMethod())
      return false;

  return true;
}


//===----------------------------------------------------------------------===//
// PrettyStackTraceDecl Implementation
//===----------------------------------------------------------------------===//

void PrettyStackTraceDecl::print(raw_ostream &OS) const {
  SourceLocation TheLoc = Loc;
  if (TheLoc.isInvalid() && TheDecl)
    TheLoc = TheDecl->getLocation();

  if (TheLoc.isValid()) {
    TheLoc.print(OS, SM);
    OS << ": ";
  }

  OS << Message;

  if (const NamedDecl *DN = dyn_cast_or_null<NamedDecl>(TheDecl))
    OS << " '" << DN->getQualifiedNameAsString() << '\'';
  OS << '\n';
}

//===----------------------------------------------------------------------===//
// Decl Implementation
//===----------------------------------------------------------------------===//

// Out-of-line virtual method providing a home for Decl.
Decl::~Decl() { }

void Decl::setDeclContext(DeclContext *DC) {
  DeclCtx = DC;
}

void Decl::setLexicalDeclContext(DeclContext *DC) {
  if (DC == getLexicalDeclContext())
    return;

  if (isInSemaDC()) {
    MultipleDC *MDC = new (getASTContext()) MultipleDC();
    MDC->SemanticDC = getDeclContext();
    MDC->LexicalDC = DC;
    DeclCtx = MDC;
  } else {
    getMultipleDC()->LexicalDC = DC;
  }
}

bool Decl::isInAnonymousNamespace() const {
  const DeclContext *DC = getDeclContext();
  do {
    if (const NamespaceDecl *ND = dyn_cast<NamespaceDecl>(DC))
      if (ND->isAnonymousNamespace())
        return true;
  } while ((DC = DC->getParent()));

  return false;
}

TranslationUnitDecl *Decl::getTranslationUnitDecl() {
  if (TranslationUnitDecl *TUD = dyn_cast<TranslationUnitDecl>(this))
    return TUD;

  DeclContext *DC = getDeclContext();
  assert(DC && "This decl is not contained in a translation unit!");

  while (!DC->isTranslationUnit()) {
    DC = DC->getParent();
    assert(DC && "This decl is not contained in a translation unit!");
  }

  return cast<TranslationUnitDecl>(DC);
}

ASTContext &Decl::getASTContext() const {
  return getTranslationUnitDecl()->getASTContext();
}

ASTMutationListener *Decl::getASTMutationListener() const {
  return getASTContext().getASTMutationListener();
}

bool Decl::isUsed(bool CheckUsedAttr) const {
  if (Used)
    return true;

  // Check for used attribute.
  if (CheckUsedAttr && hasAttr<UsedAttr>())
    return true;

  // Check redeclarations for used attribute.
  for (redecl_iterator I = redecls_begin(), E = redecls_end(); I != E; ++I) {
    if ((CheckUsedAttr && I->hasAttr<UsedAttr>()) || I->Used)
      return true;
  }

  return false;
}

bool Decl::isReferenced() const {
  if (Referenced)
    return true;

  // Check redeclarations.
  for (redecl_iterator I = redecls_begin(), E = redecls_end(); I != E; ++I)
    if (I->Referenced)
      return true;

  return false;
}

/// \brief Determine the availability of the given declaration based on
/// the target platform.
///
/// When it returns an availability result other than \c AR_Available,
/// if the \p Message parameter is non-NULL, it will be set to a
/// string describing why the entity is unavailable.
///
/// FIXME: Make these strings localizable, since they end up in
/// diagnostics.
static AvailabilityResult CheckAvailability(ASTContext &Context,
                                            const AvailabilityAttr *A,
                                            std::string *Message) {
  StringRef TargetPlatform = Context.getTargetInfo().getPlatformName();
  StringRef PrettyPlatformName
    = AvailabilityAttr::getPrettyPlatformName(TargetPlatform);
  if (PrettyPlatformName.empty())
    PrettyPlatformName = TargetPlatform;

  VersionTuple TargetMinVersion = Context.getTargetInfo().getPlatformMinVersion();
  if (TargetMinVersion.empty())
    return AR_Available;

  // Match the platform name.
  if (A->getPlatform()->getName() != TargetPlatform)
    return AR_Available;

  // Make sure that this declaration has not been marked 'unavailable'.
  if (A->getUnavailable()) {
    if (Message) {
      Message->clear();
      llvm::raw_string_ostream Out(*Message);
      Out << "not available on " << PrettyPlatformName;
    }

    return AR_Unavailable;
  }

  // Make sure that this declaration has already been introduced.
  if (!A->getIntroduced().empty() &&
      TargetMinVersion < A->getIntroduced()) {
    if (Message) {
      Message->clear();
      llvm::raw_string_ostream Out(*Message);
      Out << "introduced in " << PrettyPlatformName << ' '
          << A->getIntroduced();
    }

    return AR_NotYetIntroduced;
  }

  // Make sure that this declaration hasn't been obsoleted.
  if (!A->getObsoleted().empty() && TargetMinVersion >= A->getObsoleted()) {
    if (Message) {
      Message->clear();
      llvm::raw_string_ostream Out(*Message);
      Out << "obsoleted in " << PrettyPlatformName << ' '
          << A->getObsoleted();
    }

    return AR_Unavailable;
  }

  // Make sure that this declaration hasn't been deprecated.
  if (!A->getDeprecated().empty() && TargetMinVersion >= A->getDeprecated()) {
    if (Message) {
      Message->clear();
      llvm::raw_string_ostream Out(*Message);
      Out << "first deprecated in " << PrettyPlatformName << ' '
          << A->getDeprecated();
    }

    return AR_Deprecated;
  }

  return AR_Available;
}

AvailabilityResult Decl::getAvailability(std::string *Message) const {
  AvailabilityResult Result = AR_Available;
  std::string ResultMessage;

  for (attr_iterator A = attr_begin(), AEnd = attr_end(); A != AEnd; ++A) {
    if (DeprecatedAttr *Deprecated = dyn_cast<DeprecatedAttr>(*A)) {
      if (Result >= AR_Deprecated)
        continue;

      if (Message)
        ResultMessage = Deprecated->getMessage();

      Result = AR_Deprecated;
      continue;
    }

    if (UnavailableAttr *Unavailable = dyn_cast<UnavailableAttr>(*A)) {
      if (Message)
        *Message = Unavailable->getMessage();
      return AR_Unavailable;
    }

    if (AvailabilityAttr *Availability = dyn_cast<AvailabilityAttr>(*A)) {
      AvailabilityResult AR = CheckAvailability(getASTContext(), Availability,
                                                Message);

      if (AR == AR_Unavailable)
        return AR_Unavailable;

      if (AR > Result) {
        Result = AR;
        if (Message)
          ResultMessage.swap(*Message);
      }
      continue;
    }
  }

  if (Message)
    Message->swap(ResultMessage);
  return Result;
}

bool Decl::canBeWeakImported(bool &IsDefinition) const {
  IsDefinition = false;
  if (const VarDecl *Var = dyn_cast<VarDecl>(this)) {
    if (!Var->hasExternalStorage() || Var->getInit()) {
      IsDefinition = true;
      return false;
    }
  } else if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(this)) {
    if (FD->hasBody()) {
      IsDefinition = true;
      return false;
    }
  } else if (isa<ObjCPropertyDecl>(this) || isa<ObjCMethodDecl>(this))
    return false;
  else if (!(getASTContext().getLangOptions().ObjCNonFragileABI &&
             isa<ObjCInterfaceDecl>(this)))
    return false;

  return true;
}

bool Decl::isWeakImported() const {
  bool IsDefinition;
  if (!canBeWeakImported(IsDefinition))
    return false;

  for (attr_iterator A = attr_begin(), AEnd = attr_end(); A != AEnd; ++A) {
    if (isa<WeakImportAttr>(*A))
      return true;

    if (AvailabilityAttr *Availability = dyn_cast<AvailabilityAttr>(*A)) {
      if (CheckAvailability(getASTContext(), Availability, 0)
                                                         == AR_NotYetIntroduced)
        return true;
    }
  }

  return false;
}

unsigned Decl::getIdentifierNamespaceForKind(Kind DeclKind) {
  switch (DeclKind) {
    case Function:
    case CXXMethod:
    case CXXConstructor:
    case CXXDestructor:
    case CXXConversion:
    case EnumConstant:
    case Var:
    case ImplicitParam:
    case ParmVar:
    case NonTypeTemplateParm:
    case ObjCMethod:
    case ObjCProperty:
      return IDNS_Ordinary;
    case Label:
      return IDNS_Label;
    case IndirectField:
      return IDNS_Ordinary | IDNS_Member;

    case ObjCCompatibleAlias:
    case ObjCInterface:
      return IDNS_Ordinary | IDNS_Type;

    case Typedef:
    case TypeAlias:
    case TypeAliasTemplate:
    case UnresolvedUsingTypename:
    case TemplateTypeParm:
      return IDNS_Ordinary | IDNS_Type;

    case UsingShadow:
      return 0; // we'll actually overwrite this later

    case UnresolvedUsingValue:
      return IDNS_Ordinary | IDNS_Using;

    case Using:
      return IDNS_Using;

    case ObjCProtocol:
      return IDNS_ObjCProtocol;

    case Field:
    case ObjCAtDefsField:
    case ObjCIvar:
      return IDNS_Member;

    case Record:
    case CXXRecord:
    case Enum:
      return IDNS_Tag | IDNS_Type;

    case Namespace:
    case NamespaceAlias:
      return IDNS_Namespace;

    case FunctionTemplate:
      return IDNS_Ordinary;

    case ClassTemplate:
    case TemplateTemplateParm:
      return IDNS_Ordinary | IDNS_Tag | IDNS_Type;

    // Never have names.
    case Friend:
    case FriendTemplate:
    case AccessSpec:
    case LinkageSpec:
    case FileScopeAsm:
    case StaticAssert:
    case ObjCClass:
    case ObjCPropertyImpl:
    case ObjCForwardProtocol:
    case Block:
    case TranslationUnit:

    case UsingDirective:
    case ClassTemplateSpecialization:
    case ClassTemplatePartialSpecialization:
    case ClassScopeFunctionSpecialization:
    case ObjCImplementation:
    case ObjCCategory:
    case ObjCCategoryImpl:
      // Never looked up by name.
      return 0;
  }

  return 0;
}

void Decl::setAttrs(const AttrVec &attrs) {
  assert(!HasAttrs && "Decl already contains attrs.");

  AttrVec &AttrBlank = getASTContext().getDeclAttrs(this);
  assert(AttrBlank.empty() && "HasAttrs was wrong?");

  AttrBlank = attrs;
  HasAttrs = true;
}

void Decl::dropAttrs() {
  if (!HasAttrs) return;

  HasAttrs = false;
  getASTContext().eraseDeclAttrs(this);
}

const AttrVec &Decl::getAttrs() const {
  assert(HasAttrs && "No attrs to get!");
  return getASTContext().getDeclAttrs(this);
}

void Decl::swapAttrs(Decl *RHS) {
  bool HasLHSAttr = this->HasAttrs;
  bool HasRHSAttr = RHS->HasAttrs;

  // Usually, neither decl has attrs, nothing to do.
  if (!HasLHSAttr && !HasRHSAttr) return;

  // If 'this' has no attrs, swap the other way.
  if (!HasLHSAttr)
    return RHS->swapAttrs(this);

  ASTContext &Context = getASTContext();

  // Handle the case when both decls have attrs.
  if (HasRHSAttr) {
    std::swap(Context.getDeclAttrs(this), Context.getDeclAttrs(RHS));
    return;
  }

  // Otherwise, LHS has an attr and RHS doesn't.
  Context.getDeclAttrs(RHS) = Context.getDeclAttrs(this);
  Context.eraseDeclAttrs(this);
  this->HasAttrs = false;
  RHS->HasAttrs = true;
}

Decl *Decl::castFromDeclContext (const DeclContext *D) {
  Decl::Kind DK = D->getDeclKind();
  switch(DK) {
#define DECL(NAME, BASE)
#define DECL_CONTEXT(NAME) \
    case Decl::NAME:       \
      return static_cast<NAME##Decl*>(const_cast<DeclContext*>(D));
#define DECL_CONTEXT_BASE(NAME)
#include "clang/AST/DeclNodes.inc"
    default:
#define DECL(NAME, BASE)
#define DECL_CONTEXT_BASE(NAME)                  \
      if (DK >= first##NAME && DK <= last##NAME) \
        return static_cast<NAME##Decl*>(const_cast<DeclContext*>(D));
#include "clang/AST/DeclNodes.inc"
      assert(false && "a decl that inherits DeclContext isn't handled");
      return 0;
  }
}

DeclContext *Decl::castToDeclContext(const Decl *D) {
  Decl::Kind DK = D->getKind();
  switch(DK) {
#define DECL(NAME, BASE)
#define DECL_CONTEXT(NAME) \
    case Decl::NAME:       \
      return static_cast<NAME##Decl*>(const_cast<Decl*>(D));
#define DECL_CONTEXT_BASE(NAME)
#include "clang/AST/DeclNodes.inc"
    default:
#define DECL(NAME, BASE)
#define DECL_CONTEXT_BASE(NAME)                                   \
      if (DK >= first##NAME && DK <= last##NAME)                  \
        return static_cast<NAME##Decl*>(const_cast<Decl*>(D));
#include "clang/AST/DeclNodes.inc"
      assert(false && "a decl that inherits DeclContext isn't handled");
      return 0;
  }
}

SourceLocation Decl::getBodyRBrace() const {
  // Special handling of FunctionDecl to avoid de-serializing the body from PCH.
  // FunctionDecl stores EndRangeLoc for this purpose.
  if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(this)) {
    const FunctionDecl *Definition;
    if (FD->hasBody(Definition))
      return Definition->getSourceRange().getEnd();
    return SourceLocation();
  }

  if (Stmt *Body = getBody())
    return Body->getSourceRange().getEnd();

  return SourceLocation();
}

void Decl::CheckAccessDeclContext() const {
#ifndef NDEBUG
  // Suppress this check if any of the following hold:
  // 1. this is the translation unit (and thus has no parent)
  // 2. this is a template parameter (and thus doesn't belong to its context)
  // 3. this is a non-type template parameter
  // 4. the context is not a record
  // 5. it's invalid
  // 6. it's a C++0x static_assert.
  if (isa<TranslationUnitDecl>(this) ||
      isa<TemplateTypeParmDecl>(this) ||
      isa<NonTypeTemplateParmDecl>(this) ||
      !isa<CXXRecordDecl>(getDeclContext()) ||
      isInvalidDecl() ||
      isa<StaticAssertDecl>(this) ||
      // FIXME: a ParmVarDecl can have ClassTemplateSpecialization
      // as DeclContext (?).
      isa<ParmVarDecl>(this) ||
      // FIXME: a ClassTemplateSpecialization or CXXRecordDecl can have
      // AS_none as access specifier.
      isa<CXXRecordDecl>(this) ||
      isa<ClassScopeFunctionSpecializationDecl>(this))
    return;

  assert(Access != AS_none &&
         "Access specifier is AS_none inside a record decl");
#endif
}

DeclContext *Decl::getNonClosureContext() {
  DeclContext *DC = getDeclContext();

  // This is basically "while (DC->isClosure()) DC = DC->getParent();"
  // except that it's significantly more efficient to cast to a known
  // decl type and call getDeclContext() than to call getParent().
  while (isa<BlockDecl>(DC))
    DC = cast<BlockDecl>(DC)->getDeclContext();

  assert(!DC->isClosure());
  return DC;
}

//===----------------------------------------------------------------------===//
// DeclContext Implementation
//===----------------------------------------------------------------------===//

bool DeclContext::classof(const Decl *D) {
  switch (D->getKind()) {
#define DECL(NAME, BASE)
#define DECL_CONTEXT(NAME) case Decl::NAME:
#define DECL_CONTEXT_BASE(NAME)
#include "clang/AST/DeclNodes.inc"
      return true;
    default:
#define DECL(NAME, BASE)
#define DECL_CONTEXT_BASE(NAME)                 \
      if (D->getKind() >= Decl::first##NAME &&  \
          D->getKind() <= Decl::last##NAME)     \
        return true;
#include "clang/AST/DeclNodes.inc"
      return false;
  }
}

DeclContext::~DeclContext() { }

/// \brief Find the parent context of this context that will be
/// used for unqualified name lookup.
///
/// Generally, the parent lookup context is the semantic context. However, for
/// a friend function the parent lookup context is the lexical context, which
/// is the class in which the friend is declared.
DeclContext *DeclContext::getLookupParent() {
  // FIXME: Find a better way to identify friends
  if (isa<FunctionDecl>(this))
    if (getParent()->getRedeclContext()->isFileContext() &&
        getLexicalParent()->getRedeclContext()->isRecord())
      return getLexicalParent();

  return getParent();
}

bool DeclContext::isInlineNamespace() const {
  return isNamespace() &&
         cast<NamespaceDecl>(this)->isInline();
}

bool DeclContext::isDependentContext() const {
  if (isFileContext())
    return false;

  if (isa<ClassTemplatePartialSpecializationDecl>(this))
    return true;

  if (const CXXRecordDecl *Record = dyn_cast<CXXRecordDecl>(this))
    if (Record->getDescribedClassTemplate())
      return true;

  if (const FunctionDecl *Function = dyn_cast<FunctionDecl>(this)) {
    if (Function->getDescribedFunctionTemplate())
      return true;

    // Friend function declarations are dependent if their *lexical*
    // context is dependent.
    if (cast<Decl>(this)->getFriendObjectKind())
      return getLexicalParent()->isDependentContext();
  }

  return getParent() && getParent()->isDependentContext();
}

bool DeclContext::isTransparentContext() const {
  if (DeclKind == Decl::Enum)
    return !cast<EnumDecl>(this)->isScoped();
  else if (DeclKind == Decl::LinkageSpec)
    return true;

  return false;
}

bool DeclContext::isExternCContext() const {
  const DeclContext *DC = this;
  while (DC->DeclKind != Decl::TranslationUnit) {
    if (DC->DeclKind == Decl::LinkageSpec)
      return cast<LinkageSpecDecl>(DC)->getLanguage()
        == LinkageSpecDecl::lang_c;
    DC = DC->getParent();
  }
  return false;
}

bool DeclContext::Encloses(const DeclContext *DC) const {
  if (getPrimaryContext() != this)
    return getPrimaryContext()->Encloses(DC);

  for (; DC; DC = DC->getParent())
    if (DC->getPrimaryContext() == this)
      return true;
  return false;
}

DeclContext *DeclContext::getPrimaryContext() {
  switch (DeclKind) {
  case Decl::TranslationUnit:
  case Decl::LinkageSpec:
  case Decl::Block:
    // There is only one DeclContext for these entities.
    return this;

  case Decl::Namespace:
    // The original namespace is our primary context.
    return static_cast<NamespaceDecl*>(this)->getOriginalNamespace();

  case Decl::ObjCMethod:
    return this;

  case Decl::ObjCInterface:
  case Decl::ObjCProtocol:
  case Decl::ObjCCategory:
    // FIXME: Can Objective-C interfaces be forward-declared?
    return this;

  case Decl::ObjCImplementation:
  case Decl::ObjCCategoryImpl:
    return this;

  default:
    if (DeclKind >= Decl::firstTag && DeclKind <= Decl::lastTag) {
      // If this is a tag type that has a definition or is currently
      // being defined, that definition is our primary context.
      TagDecl *Tag = cast<TagDecl>(this);
      assert(isa<TagType>(Tag->TypeForDecl) ||
             isa<InjectedClassNameType>(Tag->TypeForDecl));

      if (TagDecl *Def = Tag->getDefinition())
        return Def;

      if (!isa<InjectedClassNameType>(Tag->TypeForDecl)) {
        const TagType *TagTy = cast<TagType>(Tag->TypeForDecl);
        if (TagTy->isBeingDefined())
          // FIXME: is it necessarily being defined in the decl
          // that owns the type?
          return TagTy->getDecl();
      }

      return Tag;
    }

    assert(DeclKind >= Decl::firstFunction && DeclKind <= Decl::lastFunction &&
          "Unknown DeclContext kind");
    return this;
  }
}

DeclContext *DeclContext::getNextContext() {
  switch (DeclKind) {
  case Decl::Namespace:
    // Return the next namespace
    return static_cast<NamespaceDecl*>(this)->getNextNamespace();

  default:
    return 0;
  }
}

std::pair<Decl *, Decl *>
DeclContext::BuildDeclChain(const SmallVectorImpl<Decl*> &Decls) {
  // Build up a chain of declarations via the Decl::NextDeclInContext field.
  Decl *FirstNewDecl = 0;
  Decl *PrevDecl = 0;
  for (unsigned I = 0, N = Decls.size(); I != N; ++I) {
    Decl *D = Decls[I];
    if (PrevDecl)
      PrevDecl->NextDeclInContext = D;
    else
      FirstNewDecl = D;

    PrevDecl = D;
  }

  return std::make_pair(FirstNewDecl, PrevDecl);
}

/// \brief Load the declarations within this lexical storage from an
/// external source.
void
DeclContext::LoadLexicalDeclsFromExternalStorage() const {
  ExternalASTSource *Source = getParentASTContext().getExternalSource();
  assert(hasExternalLexicalStorage() && Source && "No external storage?");

  // Notify that we have a DeclContext that is initializing.
  ExternalASTSource::Deserializing ADeclContext(Source);

  // We may have already loaded just the fields of this record, in which case
  // we remove all of the fields from the list. The fields will be reloaded
  // from the external source as part of re-establishing the context.
  if (const RecordDecl *RD = dyn_cast<RecordDecl>(this)) {
    if (RD->LoadedFieldsFromExternalStorage) {
      while (FirstDecl && isa<FieldDecl>(FirstDecl)) {
        Decl *Next = FirstDecl->NextDeclInContext;
        FirstDecl->NextDeclInContext = 0;
        FirstDecl = Next;
      }

      if (!FirstDecl)
        LastDecl = 0;
    }
  }

  // Load the external declarations, if any.
  SmallVector<Decl*, 64> Decls;
  ExternalLexicalStorage = false;
  switch (Source->FindExternalLexicalDecls(this, Decls)) {
  case ELR_Success:
    break;

  case ELR_Failure:
  case ELR_AlreadyLoaded:
    return;
  }

  if (Decls.empty())
    return;

  // Splice the newly-read declarations into the beginning of the list
  // of declarations.
  Decl *ExternalFirst, *ExternalLast;
  llvm::tie(ExternalFirst, ExternalLast) = BuildDeclChain(Decls);
  ExternalLast->NextDeclInContext = FirstDecl;
  FirstDecl = ExternalFirst;
  if (!LastDecl)
    LastDecl = ExternalLast;
}

DeclContext::lookup_result
ExternalASTSource::SetNoExternalVisibleDeclsForName(const DeclContext *DC,
                                                    DeclarationName Name) {
  ASTContext &Context = DC->getParentASTContext();
  StoredDeclsMap *Map;
  if (!(Map = DC->LookupPtr))
    Map = DC->CreateStoredDeclsMap(Context);

  StoredDeclsList &List = (*Map)[Name];
  assert(List.isNull());
  (void) List;

  return DeclContext::lookup_result();
}

DeclContext::lookup_result
ExternalASTSource::SetExternalVisibleDeclsForName(const DeclContext *DC,
                                                  DeclarationName Name,
                                                  ArrayRef<NamedDecl*> Decls) {
  ASTContext &Context = DC->getParentASTContext();;

  StoredDeclsMap *Map;
  if (!(Map = DC->LookupPtr))
    Map = DC->CreateStoredDeclsMap(Context);

  StoredDeclsList &List = (*Map)[Name];
  for (ArrayRef<NamedDecl*>::iterator
         I = Decls.begin(), E = Decls.end(); I != E; ++I) {
    if (List.isNull())
      List.setOnlyValue(*I);
    else
      List.AddSubsequentDecl(*I);
  }

  return List.getLookupResult();
}

DeclContext::decl_iterator DeclContext::noload_decls_begin() const {
  return decl_iterator(FirstDecl);
}

DeclContext::decl_iterator DeclContext::noload_decls_end() const {
  return decl_iterator();
}

DeclContext::decl_iterator DeclContext::decls_begin() const {
  if (hasExternalLexicalStorage())
    LoadLexicalDeclsFromExternalStorage();

  return decl_iterator(FirstDecl);
}

DeclContext::decl_iterator DeclContext::decls_end() const {
  if (hasExternalLexicalStorage())
    LoadLexicalDeclsFromExternalStorage();

  return decl_iterator();
}

bool DeclContext::decls_empty() const {
  if (hasExternalLexicalStorage())
    LoadLexicalDeclsFromExternalStorage();

  return !FirstDecl;
}

void DeclContext::removeDecl(Decl *D) {
  assert(D->getLexicalDeclContext() == this &&
         "decl being removed from non-lexical context");
  assert((D->NextDeclInContext || D == LastDecl) &&
         "decl is not in decls list");

  // Remove D from the decl chain.  This is O(n) but hopefully rare.
  if (D == FirstDecl) {
    if (D == LastDecl)
      FirstDecl = LastDecl = 0;
    else
      FirstDecl = D->NextDeclInContext;
  } else {
    for (Decl *I = FirstDecl; true; I = I->NextDeclInContext) {
      assert(I && "decl not found in linked list");
      if (I->NextDeclInContext == D) {
        I->NextDeclInContext = D->NextDeclInContext;
        if (D == LastDecl) LastDecl = I;
        break;
      }
    }
  }

  // Mark that D is no longer in the decl chain.
  D->NextDeclInContext = 0;

  // Remove D from the lookup table if necessary.
  if (isa<NamedDecl>(D)) {
    NamedDecl *ND = cast<NamedDecl>(D);

    // Remove only decls that have a name
    if (!ND->getDeclName()) return;

    StoredDeclsMap *Map = getPrimaryContext()->LookupPtr;
    if (!Map) return;

    StoredDeclsMap::iterator Pos = Map->find(ND->getDeclName());
    assert(Pos != Map->end() && "no lookup entry for decl");
    Pos->second.remove(ND);
  }
}

void DeclContext::addHiddenDecl(Decl *D) {
  assert(D->getLexicalDeclContext() == this &&
         "Decl inserted into wrong lexical context");
  assert(!D->getNextDeclInContext() && D != LastDecl &&
         "Decl already inserted into a DeclContext");

  if (FirstDecl) {
    LastDecl->NextDeclInContext = D;
    LastDecl = D;
  } else {
    FirstDecl = LastDecl = D;
  }

  // Notify a C++ record declaration that we've added a member, so it can
  // update it's class-specific state.
  if (CXXRecordDecl *Record = dyn_cast<CXXRecordDecl>(this))
    Record->addedMember(D);
}

void DeclContext::addDecl(Decl *D) {
  addHiddenDecl(D);

  if (NamedDecl *ND = dyn_cast<NamedDecl>(D))
    ND->getDeclContext()->makeDeclVisibleInContext(ND);
}

/// buildLookup - Build the lookup data structure with all of the
/// declarations in DCtx (and any other contexts linked to it or
/// transparent contexts nested within it).
void DeclContext::buildLookup(DeclContext *DCtx) {
  for (; DCtx; DCtx = DCtx->getNextContext()) {
    for (decl_iterator D = DCtx->decls_begin(),
                    DEnd = DCtx->decls_end();
         D != DEnd; ++D) {
      // Insert this declaration into the lookup structure, but only
      // if it's semantically in its decl context.  During non-lazy
      // lookup building, this is implicitly enforced by addDecl.
      if (NamedDecl *ND = dyn_cast<NamedDecl>(*D))
        if (D->getDeclContext() == DCtx)
          makeDeclVisibleInContextImpl(ND);

      // Insert any forward-declared Objective-C interface into the lookup
      // data structure.
      if (ObjCClassDecl *Class = dyn_cast<ObjCClassDecl>(*D))
        makeDeclVisibleInContextImpl(Class->getForwardInterfaceDecl());

      // If this declaration is itself a transparent declaration context or
      // inline namespace, add its members (recursively).
      if (DeclContext *InnerCtx = dyn_cast<DeclContext>(*D))
        if (InnerCtx->isTransparentContext() || InnerCtx->isInlineNamespace())
          buildLookup(InnerCtx->getPrimaryContext());
    }
  }
}

DeclContext::lookup_result
DeclContext::lookup(DeclarationName Name) {
  DeclContext *PrimaryContext = getPrimaryContext();
  if (PrimaryContext != this)
    return PrimaryContext->lookup(Name);

  if (hasExternalVisibleStorage()) {
    // Check to see if we've already cached the lookup results.
    if (LookupPtr) {
      StoredDeclsMap::iterator I = LookupPtr->find(Name);
      if (I != LookupPtr->end())
        return I->second.getLookupResult();
    }

    ExternalASTSource *Source = getParentASTContext().getExternalSource();
    return Source->FindExternalVisibleDeclsByName(this, Name);
  }

  /// If there is no lookup data structure, build one now by walking
  /// all of the linked DeclContexts (in declaration order!) and
  /// inserting their values.
  if (!LookupPtr) {
    buildLookup(this);

    if (!LookupPtr)
      return lookup_result(lookup_iterator(0), lookup_iterator(0));
  }

  StoredDeclsMap::iterator Pos = LookupPtr->find(Name);
  if (Pos == LookupPtr->end())
    return lookup_result(lookup_iterator(0), lookup_iterator(0));
  return Pos->second.getLookupResult();
}

DeclContext::lookup_const_result
DeclContext::lookup(DeclarationName Name) const {
  return const_cast<DeclContext*>(this)->lookup(Name);
}

DeclContext *DeclContext::getRedeclContext() {
  DeclContext *Ctx = this;
  // Skip through transparent contexts.
  while (Ctx->isTransparentContext())
    Ctx = Ctx->getParent();
  return Ctx;
}

DeclContext *DeclContext::getEnclosingNamespaceContext() {
  DeclContext *Ctx = this;
  // Skip through non-namespace, non-translation-unit contexts.
  while (!Ctx->isFileContext())
    Ctx = Ctx->getParent();
  return Ctx->getPrimaryContext();
}

bool DeclContext::InEnclosingNamespaceSetOf(const DeclContext *O) const {
  // For non-file contexts, this is equivalent to Equals.
  if (!isFileContext())
    return O->Equals(this);

  do {
    if (O->Equals(this))
      return true;

    const NamespaceDecl *NS = dyn_cast<NamespaceDecl>(O);
    if (!NS || !NS->isInline())
      break;
    O = NS->getParent();
  } while (O);

  return false;
}

void DeclContext::makeDeclVisibleInContext(NamedDecl *D, bool Recoverable) {
  // FIXME: This feels like a hack. Should DeclarationName support
  // template-ids, or is there a better way to keep specializations
  // from being visible?
  if (isa<ClassTemplateSpecializationDecl>(D) || D->isTemplateParameter())
    return;
  if (FunctionDecl *FD = dyn_cast<FunctionDecl>(D))
    if (FD->isFunctionTemplateSpecialization())
      return;

  DeclContext *PrimaryContext = getPrimaryContext();
  if (PrimaryContext != this) {
    PrimaryContext->makeDeclVisibleInContext(D, Recoverable);
    return;
  }

  // If we already have a lookup data structure, perform the insertion
  // into it. If we haven't deserialized externally stored decls, deserialize
  // them so we can add the decl. Otherwise, be lazy and don't build that
  // structure until someone asks for it.
  if (LookupPtr || !Recoverable || hasExternalVisibleStorage())
    makeDeclVisibleInContextImpl(D);

  // If we are a transparent context or inline namespace, insert into our
  // parent context, too. This operation is recursive.
  if (isTransparentContext() || isInlineNamespace())
    getParent()->makeDeclVisibleInContext(D, Recoverable);

  Decl *DCAsDecl = cast<Decl>(this);
  // Notify that a decl was made visible unless it's a Tag being defined.
  if (!(isa<TagDecl>(DCAsDecl) && cast<TagDecl>(DCAsDecl)->isBeingDefined()))
    if (ASTMutationListener *L = DCAsDecl->getASTMutationListener())
      L->AddedVisibleDecl(this, D);
}

void DeclContext::makeDeclVisibleInContextImpl(NamedDecl *D) {
  // Skip unnamed declarations.
  if (!D->getDeclName())
    return;

  // Skip entities that can't be found by name lookup into a particular
  // context.
  if ((D->getIdentifierNamespace() == 0 && !isa<UsingDirectiveDecl>(D)) ||
      D->isTemplateParameter())
    return;

  ASTContext *C = 0;
  if (!LookupPtr) {
    C = &getParentASTContext();
    CreateStoredDeclsMap(*C);
  }

  // If there is an external AST source, load any declarations it knows about
  // with this declaration's name.
  // If the lookup table contains an entry about this name it means that we
  // have already checked the external source.
  if (ExternalASTSource *Source = getParentASTContext().getExternalSource())
    if (hasExternalVisibleStorage() &&
        LookupPtr->find(D->getDeclName()) == LookupPtr->end())
      Source->FindExternalVisibleDeclsByName(this, D->getDeclName());

  // Insert this declaration into the map.
  StoredDeclsList &DeclNameEntries = (*LookupPtr)[D->getDeclName()];
  if (DeclNameEntries.isNull()) {
    DeclNameEntries.setOnlyValue(D);
    return;
  }

  // If it is possible that this is a redeclaration, check to see if there is
  // already a decl for which declarationReplaces returns true.  If there is
  // one, just replace it and return.
  if (DeclNameEntries.HandleRedeclaration(D))
    return;

  // Put this declaration into the appropriate slot.
  DeclNameEntries.AddSubsequentDecl(D);
}

/// Returns iterator range [First, Last) of UsingDirectiveDecls stored within
/// this context.
DeclContext::udir_iterator_range
DeclContext::getUsingDirectives() const {
  lookup_const_result Result = lookup(UsingDirectiveDecl::getName());
  return udir_iterator_range(reinterpret_cast<udir_iterator>(Result.first),
                             reinterpret_cast<udir_iterator>(Result.second));
}

//===----------------------------------------------------------------------===//
// Creation and Destruction of StoredDeclsMaps.                               //
//===----------------------------------------------------------------------===//

StoredDeclsMap *DeclContext::CreateStoredDeclsMap(ASTContext &C) const {
  assert(!LookupPtr && "context already has a decls map");
  assert(getPrimaryContext() == this &&
         "creating decls map on non-primary context");

  StoredDeclsMap *M;
  bool Dependent = isDependentContext();
  if (Dependent)
    M = new DependentStoredDeclsMap();
  else
    M = new StoredDeclsMap();
  M->Previous = C.LastSDM;
  C.LastSDM = llvm::PointerIntPair<StoredDeclsMap*,1>(M, Dependent);
  LookupPtr = M;
  return M;
}

void ASTContext::ReleaseDeclContextMaps() {
  // It's okay to delete DependentStoredDeclsMaps via a StoredDeclsMap
  // pointer because the subclass doesn't add anything that needs to
  // be deleted.
  StoredDeclsMap::DestroyAll(LastSDM.getPointer(), LastSDM.getInt());
}

void StoredDeclsMap::DestroyAll(StoredDeclsMap *Map, bool Dependent) {
  while (Map) {
    // Advance the iteration before we invalidate memory.
    llvm::PointerIntPair<StoredDeclsMap*,1> Next = Map->Previous;

    if (Dependent)
      delete static_cast<DependentStoredDeclsMap*>(Map);
    else
      delete Map;

    Map = Next.getPointer();
    Dependent = Next.getInt();
  }
}

DependentDiagnostic *DependentDiagnostic::Create(ASTContext &C,
                                                 DeclContext *Parent,
                                           const PartialDiagnostic &PDiag) {
  assert(Parent->isDependentContext()
         && "cannot iterate dependent diagnostics of non-dependent context");
  Parent = Parent->getPrimaryContext();
  if (!Parent->LookupPtr)
    Parent->CreateStoredDeclsMap(C);

  DependentStoredDeclsMap *Map
    = static_cast<DependentStoredDeclsMap*>(Parent->LookupPtr);

  // Allocate the copy of the PartialDiagnostic via the ASTContext's
  // BumpPtrAllocator, rather than the ASTContext itself.
  PartialDiagnostic::Storage *DiagStorage = 0;
  if (PDiag.hasStorage())
    DiagStorage = new (C) PartialDiagnostic::Storage;

  DependentDiagnostic *DD = new (C) DependentDiagnostic(PDiag, DiagStorage);

  // TODO: Maybe we shouldn't reverse the order during insertion.
  DD->NextDiagnostic = Map->FirstDiagnostic;
  Map->FirstDiagnostic = DD;

  return DD;
}