ASTContext.cpp

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//===- ASTContext.cpp - Context to hold long-lived AST nodes --------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
//  This file implements the ASTContext interface.
//
//===----------------------------------------------------------------------===//

#include "clang/AST/ASTContext.h"
#include "CXXABI.h"
#include "Interp/Context.h"
#include "clang/AST/APValue.h"
#include "clang/AST/ASTMutationListener.h"
#include "clang/AST/ASTTypeTraits.h"
#include "clang/AST/Attr.h"
#include "clang/AST/AttrIterator.h"
#include "clang/AST/CharUnits.h"
#include "clang/AST/Comment.h"
#include "clang/AST/Decl.h"
#include "clang/AST/DeclBase.h"
#include "clang/AST/DeclCXX.h"
#include "clang/AST/DeclContextInternals.h"
#include "clang/AST/DeclObjC.h"
#include "clang/AST/DeclOpenMP.h"
#include "clang/AST/DeclTemplate.h"
#include "clang/AST/DeclarationName.h"
#include "clang/AST/Expr.h"
#include "clang/AST/ExprCXX.h"
#include "clang/AST/ExternalASTSource.h"
#include "clang/AST/Mangle.h"
#include "clang/AST/MangleNumberingContext.h"
#include "clang/AST/NestedNameSpecifier.h"
#include "clang/AST/RawCommentList.h"
#include "clang/AST/RecordLayout.h"
#include "clang/AST/RecursiveASTVisitor.h"
#include "clang/AST/Stmt.h"
#include "clang/AST/TemplateBase.h"
#include "clang/AST/TemplateName.h"
#include "clang/AST/Type.h"
#include "clang/AST/TypeLoc.h"
#include "clang/AST/UnresolvedSet.h"
#include "clang/AST/VTableBuilder.h"
#include "clang/Basic/AddressSpaces.h"
#include "clang/Basic/Builtins.h"
#include "clang/Basic/CommentOptions.h"
#include "clang/Basic/ExceptionSpecificationType.h"
#include "clang/Basic/FixedPoint.h"
#include "clang/Basic/IdentifierTable.h"
#include "clang/Basic/LLVM.h"
#include "clang/Basic/LangOptions.h"
#include "clang/Basic/Linkage.h"
#include "clang/Basic/ObjCRuntime.h"
#include "clang/Basic/SanitizerBlacklist.h"
#include "clang/Basic/SourceLocation.h"
#include "clang/Basic/SourceManager.h"
#include "clang/Basic/Specifiers.h"
#include "clang/Basic/TargetCXXABI.h"
#include "clang/Basic/TargetInfo.h"
#include "clang/Basic/XRayLists.h"
#include "llvm/ADT/APInt.h"
#include "llvm/ADT/APSInt.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/DenseSet.h"
#include "llvm/ADT/FoldingSet.h"
#include "llvm/ADT/None.h"
#include "llvm/ADT/Optional.h"
#include "llvm/ADT/PointerUnion.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/Triple.h"
#include "llvm/Support/Capacity.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/raw_ostream.h"
#include <algorithm>
#include <cassert>
#include <cstddef>
#include <cstdint>
#include <cstdlib>
#include <map>
#include <memory>
#include <string>
#include <tuple>
#include <utility>

using namespace clang;

enum FloatingRank {
  Float16Rank, HalfRank, FloatRank, DoubleRank, LongDoubleRank, Float128Rank
};

/// \returns location that is relevant when searching for Doc comments related
/// to \p D.
static SourceLocation getDeclLocForCommentSearch(const Decl *D,
                                                 SourceManager &SourceMgr) {
  assert(D);

  // User can not attach documentation to implicit declarations.
  if (D->isImplicit())
    return {};

  // User can not attach documentation to implicit instantiations.
  if (const auto *FD = dyn_cast<FunctionDecl>(D)) {
    if (FD->getTemplateSpecializationKind() == TSK_ImplicitInstantiation)
      return {};
  }

  if (const auto *VD = dyn_cast<VarDecl>(D)) {
    if (VD->isStaticDataMember() &&
        VD->getTemplateSpecializationKind() == TSK_ImplicitInstantiation)
      return {};
  }

  if (const auto *CRD = dyn_cast<CXXRecordDecl>(D)) {
    if (CRD->getTemplateSpecializationKind() == TSK_ImplicitInstantiation)
      return {};
  }

  if (const auto *CTSD = dyn_cast<ClassTemplateSpecializationDecl>(D)) {
    TemplateSpecializationKind TSK = CTSD->getSpecializationKind();
    if (TSK == TSK_ImplicitInstantiation ||
        TSK == TSK_Undeclared)
      return {};
  }

  if (const auto *ED = dyn_cast<EnumDecl>(D)) {
    if (ED->getTemplateSpecializationKind() == TSK_ImplicitInstantiation)
      return {};
  }
  if (const auto *TD = dyn_cast<TagDecl>(D)) {
    // When tag declaration (but not definition!) is part of the
    // decl-specifier-seq of some other declaration, it doesn't get comment
    if (TD->isEmbeddedInDeclarator() && !TD->isCompleteDefinition())
      return {};
  }
  // TODO: handle comments for function parameters properly.
  if (isa<ParmVarDecl>(D))
    return {};

  // TODO: we could look up template parameter documentation in the template
  // documentation.
  if (isa<TemplateTypeParmDecl>(D) ||
      isa<NonTypeTemplateParmDecl>(D) ||
      isa<TemplateTemplateParmDecl>(D))
    return {};

  // Find declaration location.
  // For Objective-C declarations we generally don't expect to have multiple
  // declarators, thus use declaration starting location as the "declaration
  // location".
  // For all other declarations multiple declarators are used quite frequently,
  // so we use the location of the identifier as the "declaration location".
  if (isa<ObjCMethodDecl>(D) || isa<ObjCContainerDecl>(D) ||
      isa<ObjCPropertyDecl>(D) ||
      isa<RedeclarableTemplateDecl>(D) ||
      isa<ClassTemplateSpecializationDecl>(D))
    return D->getBeginLoc();
  else {
    const SourceLocation DeclLoc = D->getLocation();
    if (DeclLoc.isMacroID()) {
      if (isa<TypedefDecl>(D)) {
        // If location of the typedef name is in a macro, it is because being
        // declared via a macro. Try using declaration's starting location as
        // the "declaration location".
        return D->getBeginLoc();
      } else if (const auto *TD = dyn_cast<TagDecl>(D)) {
        // If location of the tag decl is inside a macro, but the spelling of
        // the tag name comes from a macro argument, it looks like a special
        // macro like NS_ENUM is being used to define the tag decl.  In that
        // case, adjust the source location to the expansion loc so that we can
        // attach the comment to the tag decl.
        if (SourceMgr.isMacroArgExpansion(DeclLoc) &&
            TD->isCompleteDefinition())
          return SourceMgr.getExpansionLoc(DeclLoc);
      }
    }
    return DeclLoc;
  }

  return {};
}

RawComment *ASTContext::getRawCommentForDeclNoCacheImpl(
    const Decl *D, const SourceLocation RepresentativeLocForDecl,
    const std::map<unsigned, RawComment *> &CommentsInTheFile) const {
  // If the declaration doesn't map directly to a location in a file, we
  // can't find the comment.
  if (RepresentativeLocForDecl.isInvalid() ||
      !RepresentativeLocForDecl.isFileID())
    return nullptr;

  // If there are no comments anywhere, we won't find anything.
  if (CommentsInTheFile.empty())
    return nullptr;

  // Decompose the location for the declaration and find the beginning of the
  // file buffer.
  const std::pair<FileID, unsigned> DeclLocDecomp =
      SourceMgr.getDecomposedLoc(RepresentativeLocForDecl);

  // Slow path.
  auto OffsetCommentBehindDecl =
      CommentsInTheFile.lower_bound(DeclLocDecomp.second);

  // First check whether we have a trailing comment.
  if (OffsetCommentBehindDecl != CommentsInTheFile.end()) {
    RawComment *CommentBehindDecl = OffsetCommentBehindDecl->second;
    if ((CommentBehindDecl->isDocumentation() ||
         LangOpts.CommentOpts.ParseAllComments) &&
        CommentBehindDecl->isTrailingComment() &&
        (isa<FieldDecl>(D) || isa<EnumConstantDecl>(D) || isa<VarDecl>(D) ||
         isa<ObjCMethodDecl>(D) || isa<ObjCPropertyDecl>(D))) {

      // Check that Doxygen trailing comment comes after the declaration, starts
      // on the same line and in the same file as the declaration.
      if (SourceMgr.getLineNumber(DeclLocDecomp.first, DeclLocDecomp.second) ==
          Comments.getCommentBeginLine(CommentBehindDecl, DeclLocDecomp.first,
                                       OffsetCommentBehindDecl->first)) {
        return CommentBehindDecl;
      }
    }
  }

  // The comment just after the declaration was not a trailing comment.
  // Let's look at the previous comment.
  if (OffsetCommentBehindDecl == CommentsInTheFile.begin())
    return nullptr;

  auto OffsetCommentBeforeDecl = --OffsetCommentBehindDecl;
  RawComment *CommentBeforeDecl = OffsetCommentBeforeDecl->second;

  // Check that we actually have a non-member Doxygen comment.
  if (!(CommentBeforeDecl->isDocumentation() ||
        LangOpts.CommentOpts.ParseAllComments) ||
      CommentBeforeDecl->isTrailingComment())
    return nullptr;

  // Decompose the end of the comment.
  const unsigned CommentEndOffset =
      Comments.getCommentEndOffset(CommentBeforeDecl);

  // Get the corresponding buffer.
  bool Invalid = false;
  const char *Buffer = SourceMgr.getBufferData(DeclLocDecomp.first,
                                               &Invalid).data();
  if (Invalid)
    return nullptr;

  // Extract text between the comment and declaration.
  StringRef Text(Buffer + CommentEndOffset,
                 DeclLocDecomp.second - CommentEndOffset);

  // There should be no other declarations or preprocessor directives between
  // comment and declaration.
  if (Text.find_first_of(";{}#@") != StringRef::npos)
    return nullptr;

  return CommentBeforeDecl;
}

RawComment *ASTContext::getRawCommentForDeclNoCache(const Decl *D) const {
  const SourceLocation DeclLoc = getDeclLocForCommentSearch(D, SourceMgr);

  // If the declaration doesn't map directly to a location in a file, we
  // can't find the comment.
  if (DeclLoc.isInvalid() || !DeclLoc.isFileID())
    return nullptr;

  if (ExternalSource && !CommentsLoaded) {
    ExternalSource->ReadComments();
    CommentsLoaded = true;
  }

  if (Comments.empty())
    return nullptr;

  const FileID File = SourceMgr.getDecomposedLoc(DeclLoc).first;
  const auto CommentsInThisFile = Comments.getCommentsInFile(File);
  if (!CommentsInThisFile || CommentsInThisFile->empty())
    return nullptr;

  return getRawCommentForDeclNoCacheImpl(D, DeclLoc, *CommentsInThisFile);
}

/// If we have a 'templated' declaration for a template, adjust 'D' to
/// refer to the actual template.
/// If we have an implicit instantiation, adjust 'D' to refer to template.
static const Decl &adjustDeclToTemplate(const Decl &D) {
  if (const auto *FD = dyn_cast<FunctionDecl>(&D)) {
    // Is this function declaration part of a function template?
    if (const FunctionTemplateDecl *FTD = FD->getDescribedFunctionTemplate())
      return *FTD;

    // Nothing to do if function is not an implicit instantiation.
    if (FD->getTemplateSpecializationKind() != TSK_ImplicitInstantiation)
      return D;

    // Function is an implicit instantiation of a function template?
    if (const FunctionTemplateDecl *FTD = FD->getPrimaryTemplate())
      return *FTD;

    // Function is instantiated from a member definition of a class template?
    if (const FunctionDecl *MemberDecl =
            FD->getInstantiatedFromMemberFunction())
      return *MemberDecl;

    return D;
  }
  if (const auto *VD = dyn_cast<VarDecl>(&D)) {
    // Static data member is instantiated from a member definition of a class
    // template?
    if (VD->isStaticDataMember())
      if (const VarDecl *MemberDecl = VD->getInstantiatedFromStaticDataMember())
        return *MemberDecl;

    return D;
  }
  if (const auto *CRD = dyn_cast<CXXRecordDecl>(&D)) {
    // Is this class declaration part of a class template?
    if (const ClassTemplateDecl *CTD = CRD->getDescribedClassTemplate())
      return *CTD;

    // Class is an implicit instantiation of a class template or partial
    // specialization?
    if (const auto *CTSD = dyn_cast<ClassTemplateSpecializationDecl>(CRD)) {
      if (CTSD->getSpecializationKind() != TSK_ImplicitInstantiation)
        return D;
      llvm::PointerUnion<ClassTemplateDecl *,
                         ClassTemplatePartialSpecializationDecl *>
          PU = CTSD->getSpecializedTemplateOrPartial();
      return PU.is<ClassTemplateDecl *>()
                 ? *static_cast<const Decl *>(PU.get<ClassTemplateDecl *>())
                 : *static_cast<const Decl *>(
                       PU.get<ClassTemplatePartialSpecializationDecl *>());
    }

    // Class is instantiated from a member definition of a class template?
    if (const MemberSpecializationInfo *Info =
            CRD->getMemberSpecializationInfo())
      return *Info->getInstantiatedFrom();

    return D;
  }
  if (const auto *ED = dyn_cast<EnumDecl>(&D)) {
    // Enum is instantiated from a member definition of a class template?
    if (const EnumDecl *MemberDecl = ED->getInstantiatedFromMemberEnum())
      return *MemberDecl;

    return D;
  }
  // FIXME: Adjust alias templates?
  return D;
}

const RawComment *ASTContext::getRawCommentForAnyRedecl(
                                                const Decl *D,
                                                const Decl **OriginalDecl) const {
  if (!D) {
    if (OriginalDecl)
      OriginalDecl = nullptr;
    return nullptr;
  }

  D = &adjustDeclToTemplate(*D);

  // Any comment directly attached to D?
  {
    auto DeclComment = DeclRawComments.find(D);
    if (DeclComment != DeclRawComments.end()) {
      if (OriginalDecl)
        *OriginalDecl = D;
      return DeclComment->second;
    }
  }

  // Any comment attached to any redeclaration of D?
  const Decl *CanonicalD = D->getCanonicalDecl();
  if (!CanonicalD)
    return nullptr;

  {
    auto RedeclComment = RedeclChainComments.find(CanonicalD);
    if (RedeclComment != RedeclChainComments.end()) {
      if (OriginalDecl)
        *OriginalDecl = RedeclComment->second;
      auto CommentAtRedecl = DeclRawComments.find(RedeclComment->second);
      assert(CommentAtRedecl != DeclRawComments.end() &&
             "This decl is supposed to have comment attached.");
      return CommentAtRedecl->second;
    }
  }

  // Any redeclarations of D that we haven't checked for comments yet?
  // We can't use DenseMap::iterator directly since it'd get invalid.
  auto LastCheckedRedecl = [this, CanonicalD]() -> const Decl * {
    auto LookupRes = CommentlessRedeclChains.find(CanonicalD);
    if (LookupRes != CommentlessRedeclChains.end())
      return LookupRes->second;
    return nullptr;
  }();

  for (const auto Redecl : D->redecls()) {
    assert(Redecl);
    // Skip all redeclarations that have been checked previously.
    if (LastCheckedRedecl) {
      if (LastCheckedRedecl == Redecl) {
        LastCheckedRedecl = nullptr;
      }
      continue;
    }
    const RawComment *RedeclComment = getRawCommentForDeclNoCache(Redecl);
    if (RedeclComment) {
      cacheRawCommentForDecl(*Redecl, *RedeclComment);
      if (OriginalDecl)
        *OriginalDecl = Redecl;
      return RedeclComment;
    }
    CommentlessRedeclChains[CanonicalD] = Redecl;
  }

  if (OriginalDecl)
    *OriginalDecl = nullptr;
  return nullptr;
}

void ASTContext::cacheRawCommentForDecl(const Decl &OriginalD,
                                        const RawComment &Comment) const {
  assert(Comment.isDocumentation() || LangOpts.CommentOpts.ParseAllComments);
  DeclRawComments.try_emplace(&OriginalD, &Comment);
  const Decl *const CanonicalDecl = OriginalD.getCanonicalDecl();
  RedeclChainComments.try_emplace(CanonicalDecl, &OriginalD);
  CommentlessRedeclChains.erase(CanonicalDecl);
}

static void addRedeclaredMethods(const ObjCMethodDecl *ObjCMethod,
                   SmallVectorImpl<const NamedDecl *> &Redeclared) {
  const DeclContext *DC = ObjCMethod->getDeclContext();
  if (const auto *IMD = dyn_cast<ObjCImplDecl>(DC)) {
    const ObjCInterfaceDecl *ID = IMD->getClassInterface();
    if (!ID)
      return;
    // Add redeclared method here.
    for (const auto *Ext : ID->known_extensions()) {
      if (ObjCMethodDecl *RedeclaredMethod =
            Ext->getMethod(ObjCMethod->getSelector(),
                                  ObjCMethod->isInstanceMethod()))
        Redeclared.push_back(RedeclaredMethod);
    }
  }
}

void ASTContext::attachCommentsToJustParsedDecls(ArrayRef<Decl *> Decls,
                                                 const Preprocessor *PP) {
  if (Comments.empty() || Decls.empty())
    return;

  // See if there are any new comments that are not attached to a decl.
  // The location doesn't have to be precise - we care only about the file.
  const FileID File =
      SourceMgr.getDecomposedLoc((*Decls.begin())->getLocation()).first;
  auto CommentsInThisFile = Comments.getCommentsInFile(File);
  if (!CommentsInThisFile || CommentsInThisFile->empty() ||
      CommentsInThisFile->rbegin()->second->isAttached())
    return;

  // There is at least one comment not attached to a decl.
  // Maybe it should be attached to one of Decls?
  //
  // Note that this way we pick up not only comments that precede the
  // declaration, but also comments that *follow* the declaration -- thanks to
  // the lookahead in the lexer: we've consumed the semicolon and looked
  // ahead through comments.

  for (const Decl *D : Decls) {
    assert(D);
    if (D->isInvalidDecl())
      continue;

    D = &adjustDeclToTemplate(*D);

    const SourceLocation DeclLoc = getDeclLocForCommentSearch(D, SourceMgr);

    if (DeclLoc.isInvalid() || !DeclLoc.isFileID())
      continue;

    if (DeclRawComments.count(D) > 0)
      continue;

    if (RawComment *const DocComment =
            getRawCommentForDeclNoCacheImpl(D, DeclLoc, *CommentsInThisFile)) {
      cacheRawCommentForDecl(*D, *DocComment);
      comments::FullComment *FC = DocComment->parse(*this, PP, D);
      ParsedComments[D->getCanonicalDecl()] = FC;
    }
  }
}

comments::FullComment *ASTContext::cloneFullComment(comments::FullComment *FC,
                                                    const Decl *D) const {
  auto *ThisDeclInfo = new (*this) comments::DeclInfo;
  ThisDeclInfo->CommentDecl = D;
  ThisDeclInfo->IsFilled = false;
  ThisDeclInfo->fill();
  ThisDeclInfo->CommentDecl = FC->getDecl();
  if (!ThisDeclInfo->TemplateParameters)
    ThisDeclInfo->TemplateParameters = FC->getDeclInfo()->TemplateParameters;
  comments::FullComment *CFC =
    new (*this) comments::FullComment(FC->getBlocks(),
                                      ThisDeclInfo);
  return CFC;
}

comments::FullComment *ASTContext::getLocalCommentForDeclUncached(const Decl *D) const {
  const RawComment *RC = getRawCommentForDeclNoCache(D);
  return RC ? RC->parse(*this, nullptr, D) : nullptr;
}

comments::FullComment *ASTContext::getCommentForDecl(
                                              const Decl *D,
                                              const Preprocessor *PP) const {
  if (!D || D->isInvalidDecl())
    return nullptr;
  D = &adjustDeclToTemplate(*D);

  const Decl *Canonical = D->getCanonicalDecl();
  llvm::DenseMap<const Decl *, comments::FullComment *>::iterator Pos =
      ParsedComments.find(Canonical);

  if (Pos != ParsedComments.end()) {
    if (Canonical != D) {
      comments::FullComment *FC = Pos->second;
      comments::FullComment *CFC = cloneFullComment(FC, D);
      return CFC;
    }
    return Pos->second;
  }

  const Decl *OriginalDecl = nullptr;

  const RawComment *RC = getRawCommentForAnyRedecl(D, &OriginalDecl);
  if (!RC) {
    if (isa<ObjCMethodDecl>(D) || isa<FunctionDecl>(D)) {
      SmallVector<const NamedDecl*, 8> Overridden;
      const auto *OMD = dyn_cast<ObjCMethodDecl>(D);
      if (OMD && OMD->isPropertyAccessor())
        if (const ObjCPropertyDecl *PDecl = OMD->findPropertyDecl())
          if (comments::FullComment *FC = getCommentForDecl(PDecl, PP))
            return cloneFullComment(FC, D);
      if (OMD)
        addRedeclaredMethods(OMD, Overridden);
      getOverriddenMethods(dyn_cast<NamedDecl>(D), Overridden);
      for (unsigned i = 0, e = Overridden.size(); i < e; i++)
        if (comments::FullComment *FC = getCommentForDecl(Overridden[i], PP))
          return cloneFullComment(FC, D);
    }
    else if (const auto *TD = dyn_cast<TypedefNameDecl>(D)) {
      // Attach any tag type's documentation to its typedef if latter
      // does not have one of its own.
      QualType QT = TD->getUnderlyingType();
      if (const auto *TT = QT->getAs<TagType>())
        if (const Decl *TD = TT->getDecl())
          if (comments::FullComment *FC = getCommentForDecl(TD, PP))
            return cloneFullComment(FC, D);
    }
    else if (const auto *IC = dyn_cast<ObjCInterfaceDecl>(D)) {
      while (IC->getSuperClass()) {
        IC = IC->getSuperClass();
        if (comments::FullComment *FC = getCommentForDecl(IC, PP))
          return cloneFullComment(FC, D);
      }
    }
    else if (const auto *CD = dyn_cast<ObjCCategoryDecl>(D)) {
      if (const ObjCInterfaceDecl *IC = CD->getClassInterface())
        if (comments::FullComment *FC = getCommentForDecl(IC, PP))
          return cloneFullComment(FC, D);
    }
    else if (const auto *RD = dyn_cast<CXXRecordDecl>(D)) {
      if (!(RD = RD->getDefinition()))
        return nullptr;
      // Check non-virtual bases.
      for (const auto &I : RD->bases()) {
        if (I.isVirtual() || (I.getAccessSpecifier() != AS_public))
          continue;
        QualType Ty = I.getType();
        if (Ty.isNull())
          continue;
        if (const CXXRecordDecl *NonVirtualBase = Ty->getAsCXXRecordDecl()) {
          if (!(NonVirtualBase= NonVirtualBase->getDefinition()))
            continue;

          if (comments::FullComment *FC = getCommentForDecl((NonVirtualBase), PP))
            return cloneFullComment(FC, D);
        }
      }
      // Check virtual bases.
      for (const auto &I : RD->vbases()) {
        if (I.getAccessSpecifier() != AS_public)
          continue;
        QualType Ty = I.getType();
        if (Ty.isNull())
          continue;
        if (const CXXRecordDecl *VirtualBase = Ty->getAsCXXRecordDecl()) {
          if (!(VirtualBase= VirtualBase->getDefinition()))
            continue;
          if (comments::FullComment *FC = getCommentForDecl((VirtualBase), PP))
            return cloneFullComment(FC, D);
        }
      }
    }
    return nullptr;
  }

  // If the RawComment was attached to other redeclaration of this Decl, we
  // should parse the comment in context of that other Decl.  This is important
  // because comments can contain references to parameter names which can be
  // different across redeclarations.
  if (D != OriginalDecl && OriginalDecl)
    return getCommentForDecl(OriginalDecl, PP);

  comments::FullComment *FC = RC->parse(*this, PP, D);
  ParsedComments[Canonical] = FC;
  return FC;
}

void
ASTContext::CanonicalTemplateTemplateParm::Profile(llvm::FoldingSetNodeID &ID,
                                               TemplateTemplateParmDecl *Parm) {
  ID.AddInteger(Parm->getDepth());
  ID.AddInteger(Parm->getPosition());
  ID.AddBoolean(Parm->isParameterPack());

  TemplateParameterList *Params = Parm->getTemplateParameters();
  ID.AddInteger(Params->size());
  for (TemplateParameterList::const_iterator P = Params->begin(),
                                          PEnd = Params->end();
       P != PEnd; ++P) {
    if (const auto *TTP = dyn_cast<TemplateTypeParmDecl>(*P)) {
      ID.AddInteger(0);
      ID.AddBoolean(TTP->isParameterPack());
      continue;
    }

    if (const auto *NTTP = dyn_cast<NonTypeTemplateParmDecl>(*P)) {
      ID.AddInteger(1);
      ID.AddBoolean(NTTP->isParameterPack());
      ID.AddPointer(NTTP->getType().getCanonicalType().getAsOpaquePtr());
      if (NTTP->isExpandedParameterPack()) {
        ID.AddBoolean(true);
        ID.AddInteger(NTTP->getNumExpansionTypes());
        for (unsigned I = 0, N = NTTP->getNumExpansionTypes(); I != N; ++I) {
          QualType T = NTTP->getExpansionType(I);
          ID.AddPointer(T.getCanonicalType().getAsOpaquePtr());
        }
      } else
        ID.AddBoolean(false);
      continue;
    }

    auto *TTP = cast<TemplateTemplateParmDecl>(*P);
    ID.AddInteger(2);
    Profile(ID, TTP);
  }
}

TemplateTemplateParmDecl *
ASTContext::getCanonicalTemplateTemplateParmDecl(
                                          TemplateTemplateParmDecl *TTP) const {
  // Check if we already have a canonical template template parameter.
  llvm::FoldingSetNodeID ID;
  CanonicalTemplateTemplateParm::Profile(ID, TTP);
  void *InsertPos = nullptr;
  CanonicalTemplateTemplateParm *Canonical
    = CanonTemplateTemplateParms.FindNodeOrInsertPos(ID, InsertPos);
  if (Canonical)
    return Canonical->getParam();

  // Build a canonical template parameter list.
  TemplateParameterList *Params = TTP->getTemplateParameters();
  SmallVector<NamedDecl *, 4> CanonParams;
  CanonParams.reserve(Params->size());
  for (TemplateParameterList::const_iterator P = Params->begin(),
                                          PEnd = Params->end();
       P != PEnd; ++P) {
    if (const auto *TTP = dyn_cast<TemplateTypeParmDecl>(*P))
      CanonParams.push_back(
                  TemplateTypeParmDecl::Create(*this, getTranslationUnitDecl(),
                                               SourceLocation(),
                                               SourceLocation(),
                                               TTP->getDepth(),
                                               TTP->getIndex(), nullptr, false,
                                               TTP->isParameterPack()));
    else if (const auto *NTTP = dyn_cast<NonTypeTemplateParmDecl>(*P)) {
      QualType T = getCanonicalType(NTTP->getType());
      TypeSourceInfo *TInfo = getTrivialTypeSourceInfo(T);
      NonTypeTemplateParmDecl *Param;
      if (NTTP->isExpandedParameterPack()) {
        SmallVector<QualType, 2> ExpandedTypes;
        SmallVector<TypeSourceInfo *, 2> ExpandedTInfos;
        for (unsigned I = 0, N = NTTP->getNumExpansionTypes(); I != N; ++I) {
          ExpandedTypes.push_back(getCanonicalType(NTTP->getExpansionType(I)));
          ExpandedTInfos.push_back(
                                getTrivialTypeSourceInfo(ExpandedTypes.back()));
        }

        Param = NonTypeTemplateParmDecl::Create(*this, getTranslationUnitDecl(),
                                                SourceLocation(),
                                                SourceLocation(),
                                                NTTP->getDepth(),
                                                NTTP->getPosition(), nullptr,
                                                T,
                                                TInfo,
                                                ExpandedTypes,
                                                ExpandedTInfos);
      } else {
        Param = NonTypeTemplateParmDecl::Create(*this, getTranslationUnitDecl(),
                                                SourceLocation(),
                                                SourceLocation(),
                                                NTTP->getDepth(),
                                                NTTP->getPosition(), nullptr,
                                                T,
                                                NTTP->isParameterPack(),
                                                TInfo);
      }
      CanonParams.push_back(Param);

    } else
      CanonParams.push_back(getCanonicalTemplateTemplateParmDecl(
                                           cast<TemplateTemplateParmDecl>(*P)));
  }

  assert(!TTP->getTemplateParameters()->getRequiresClause() &&
         "Unexpected requires-clause on template template-parameter");
  Expr *const CanonRequiresClause = nullptr;

  TemplateTemplateParmDecl *CanonTTP
    = TemplateTemplateParmDecl::Create(*this, getTranslationUnitDecl(),
                                       SourceLocation(), TTP->getDepth(),
                                       TTP->getPosition(),
                                       TTP->isParameterPack(),
                                       nullptr,
                         TemplateParameterList::Create(*this, SourceLocation(),
                                                       SourceLocation(),
                                                       CanonParams,
                                                       SourceLocation(),
                                                       CanonRequiresClause));

  // Get the new insert position for the node we care about.
  Canonical = CanonTemplateTemplateParms.FindNodeOrInsertPos(ID, InsertPos);
  assert(!Canonical && "Shouldn't be in the map!");
  (void)Canonical;

  // Create the canonical template template parameter entry.
  Canonical = new (*this) CanonicalTemplateTemplateParm(CanonTTP);
  CanonTemplateTemplateParms.InsertNode(Canonical, InsertPos);
  return CanonTTP;
}

CXXABI *ASTContext::createCXXABI(const TargetInfo &T) {
  if (!LangOpts.CPlusPlus) return nullptr;

  switch (T.getCXXABI().getKind()) {
  case TargetCXXABI::GenericARM: // Same as Itanium at this level
  case TargetCXXABI::iOS:
  case TargetCXXABI::iOS64:
  case TargetCXXABI::WatchOS:
  case TargetCXXABI::GenericAArch64:
  case TargetCXXABI::GenericMIPS:
  case TargetCXXABI::GenericItanium:
  case TargetCXXABI::WebAssembly:
    return CreateItaniumCXXABI(*this);
  case TargetCXXABI::Microsoft:
    return CreateMicrosoftCXXABI(*this);
  }
  llvm_unreachable("Invalid CXXABI type!");
}

interp::Context &ASTContext::getInterpContext() {
  if (!InterpContext) {
    InterpContext.reset(new interp::Context(*this));
  }
  return *InterpContext.get();
}

static const LangASMap *getAddressSpaceMap(const TargetInfo &T,
                                           const LangOptions &LOpts) {
  if (LOpts.FakeAddressSpaceMap) {
    // The fake address space map must have a distinct entry for each
    // language-specific address space.
    static const unsigned FakeAddrSpaceMap[] = {
      0, // Default
      1, // opencl_global
      3, // opencl_local
      2, // opencl_constant
      0, // opencl_private
      4, // opencl_generic
      5, // cuda_device
      6, // cuda_constant
      7  // cuda_shared
    };
    return &FakeAddrSpaceMap;
  } else {
    return &T.getAddressSpaceMap();
  }
}

static bool isAddrSpaceMapManglingEnabled(const TargetInfo &TI,
                                          const LangOptions &LangOpts) {
  switch (LangOpts.getAddressSpaceMapMangling()) {
  case LangOptions::ASMM_Target:
    return TI.useAddressSpaceMapMangling();
  case LangOptions::ASMM_On:
    return true;
  case LangOptions::ASMM_Off:
    return false;
  }
  llvm_unreachable("getAddressSpaceMapMangling() doesn't cover anything.");
}

ASTContext::ASTContext(LangOptions &LOpts, SourceManager &SM,
                       IdentifierTable &idents, SelectorTable &sels,
                       Builtin::Context &builtins)
    : ConstantArrayTypes(this_()), FunctionProtoTypes(this_()),
      TemplateSpecializationTypes(this_()),
      DependentTemplateSpecializationTypes(this_()),
      SubstTemplateTemplateParmPacks(this_()), SourceMgr(SM), LangOpts(LOpts),
      SanitizerBL(new SanitizerBlacklist(LangOpts.SanitizerBlacklistFiles, SM)),
      XRayFilter(new XRayFunctionFilter(LangOpts.XRayAlwaysInstrumentFiles,
                                        LangOpts.XRayNeverInstrumentFiles,
                                        LangOpts.XRayAttrListFiles, SM)),
      PrintingPolicy(LOpts), Idents(idents), Selectors(sels),
      BuiltinInfo(builtins), DeclarationNames(*this), Comments(SM),
      CommentCommandTraits(BumpAlloc, LOpts.CommentOpts),
      CompCategories(this_()), LastSDM(nullptr, 0) {
  TUDecl = TranslationUnitDecl::Create(*this);
  TraversalScope = {TUDecl};
}

ASTContext::~ASTContext() {
  // Release the DenseMaps associated with DeclContext objects.
  // FIXME: Is this the ideal solution?
  ReleaseDeclContextMaps();

  // Call all of the deallocation functions on all of their targets.
  for (auto &Pair : Deallocations)
    (Pair.first)(Pair.second);

  // ASTRecordLayout objects in ASTRecordLayouts must always be destroyed
  // because they can contain DenseMaps.
  for (llvm::DenseMap<const ObjCContainerDecl*,
       const ASTRecordLayout*>::iterator
       I = ObjCLayouts.begin(), E = ObjCLayouts.end(); I != E; )
    // Increment in loop to prevent using deallocated memory.
    if (auto *R = const_cast<ASTRecordLayout *>((I++)->second))
      R->Destroy(*this);

  for (llvm::DenseMap<const RecordDecl*, const ASTRecordLayout*>::iterator
       I = ASTRecordLayouts.begin(), E = ASTRecordLayouts.end(); I != E; ) {
    // Increment in loop to prevent using deallocated memory.
    if (auto *R = const_cast<ASTRecordLayout *>((I++)->second))
      R->Destroy(*this);
  }

  for (llvm::DenseMap<const Decl*, AttrVec*>::iterator A = DeclAttrs.begin(),
                                                    AEnd = DeclAttrs.end();
       A != AEnd; ++A)
    A->second->~AttrVec();

  for (std::pair<const MaterializeTemporaryExpr *, APValue *> &MTVPair :
       MaterializedTemporaryValues)
    MTVPair.second->~APValue();

  for (const auto &Value : ModuleInitializers)
    Value.second->~PerModuleInitializers();

  for (APValue *Value : APValueCleanups)
    Value->~APValue();
}

class ASTContext::ParentMap {
  /// Contains parents of a node.
  using ParentVector = llvm::SmallVector<ast_type_traits::DynTypedNode, 2>;

  /// Maps from a node to its parents. This is used for nodes that have
  /// pointer identity only, which are more common and we can save space by
  /// only storing a unique pointer to them.
  using ParentMapPointers = llvm::DenseMap<
      const void *,
      llvm::PointerUnion4<const Decl *, const Stmt *,
                          ast_type_traits::DynTypedNode *, ParentVector *>>;

  /// Parent map for nodes without pointer identity. We store a full
  /// DynTypedNode for all keys.
  using ParentMapOtherNodes = llvm::DenseMap<
      ast_type_traits::DynTypedNode,
      llvm::PointerUnion4<const Decl *, const Stmt *,
                          ast_type_traits::DynTypedNode *, ParentVector *>>;

  ParentMapPointers PointerParents;
  ParentMapOtherNodes OtherParents;
  class ASTVisitor;

  static ast_type_traits::DynTypedNode
  getSingleDynTypedNodeFromParentMap(ParentMapPointers::mapped_type U) {
    if (const auto *D = U.dyn_cast<const Decl *>())
      return ast_type_traits::DynTypedNode::create(*D);
    if (const auto *S = U.dyn_cast<const Stmt *>())
      return ast_type_traits::DynTypedNode::create(*S);
    return *U.get<ast_type_traits::DynTypedNode *>();
  }

  template <typename NodeTy, typename MapTy>
  static ASTContext::DynTypedNodeList getDynNodeFromMap(const NodeTy &Node,
                                                        const MapTy &Map) {
    auto I = Map.find(Node);
    if (I == Map.end()) {
      return llvm::ArrayRef<ast_type_traits::DynTypedNode>();
    }
    if (const auto *V = I->second.template dyn_cast<ParentVector *>()) {
      return llvm::makeArrayRef(*V);
    }
    return getSingleDynTypedNodeFromParentMap(I->second);
  }

public:
  ParentMap(ASTContext &Ctx);
  ~ParentMap() {
    for (const auto &Entry : PointerParents) {
      if (Entry.second.is<ast_type_traits::DynTypedNode *>()) {
        delete Entry.second.get<ast_type_traits::DynTypedNode *>();
      } else if (Entry.second.is<ParentVector *>()) {
        delete Entry.second.get<ParentVector *>();
      }
    }
    for (const auto &Entry : OtherParents) {
      if (Entry.second.is<ast_type_traits::DynTypedNode *>()) {
        delete Entry.second.get<ast_type_traits::DynTypedNode *>();
      } else if (Entry.second.is<ParentVector *>()) {
        delete Entry.second.get<ParentVector *>();
      }
    }
  }

  DynTypedNodeList getParents(const ast_type_traits::DynTypedNode &Node) {
    if (Node.getNodeKind().hasPointerIdentity())
      return getDynNodeFromMap(Node.getMemoizationData(), PointerParents);
    return getDynNodeFromMap(Node, OtherParents);
  }
};

void ASTContext::setTraversalScope(const std::vector<Decl *> &TopLevelDecls) {
  TraversalScope = TopLevelDecls;
  Parents.reset();
}

void ASTContext::AddDeallocation(void (*Callback)(void *), void *Data) const {
  Deallocations.push_back({Callback, Data});
}

void
ASTContext::setExternalSource(IntrusiveRefCntPtr<ExternalASTSource> Source) {
  ExternalSource = std::move(Source);
}

void ASTContext::PrintStats() const {
  llvm::errs() << "\n*** AST Context Stats:\n";
  llvm::errs() << "  " << Types.size() << " types total.\n";

  unsigned counts[] = {
#define TYPE(Name, Parent) 0,
#define ABSTRACT_TYPE(Name, Parent)
#include "clang/AST/TypeNodes.inc"
    0 // Extra
  };

  for (unsigned i = 0, e = Types.size(); i != e; ++i) {
    Type *T = Types[i];
    counts[(unsigned)T->getTypeClass()]++;
  }

  unsigned Idx = 0;
  unsigned TotalBytes = 0;
#define TYPE(Name, Parent)                                              \
  if (counts[Idx])                                                      \
    llvm::errs() << "    " << counts[Idx] << " " << #Name               \
                 << " types, " << sizeof(Name##Type) << " each "        \
                 << "(" << counts[Idx] * sizeof(Name##Type)             \
                 << " bytes)\n";                                        \
  TotalBytes += counts[Idx] * sizeof(Name##Type);                       \
  ++Idx;
#define ABSTRACT_TYPE(Name, Parent)
#include "clang/AST/TypeNodes.inc"

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

  // Implicit special member functions.
  llvm::errs() << NumImplicitDefaultConstructorsDeclared << "/"
               << NumImplicitDefaultConstructors
               << " implicit default constructors created\n";
  llvm::errs() << NumImplicitCopyConstructorsDeclared << "/"
               << NumImplicitCopyConstructors
               << " implicit copy constructors created\n";
  if (getLangOpts().CPlusPlus)
    llvm::errs() << NumImplicitMoveConstructorsDeclared << "/"
                 << NumImplicitMoveConstructors
                 << " implicit move constructors created\n";
  llvm::errs() << NumImplicitCopyAssignmentOperatorsDeclared << "/"
               << NumImplicitCopyAssignmentOperators
               << " implicit copy assignment operators created\n";
  if (getLangOpts().CPlusPlus)
    llvm::errs() << NumImplicitMoveAssignmentOperatorsDeclared << "/"
                 << NumImplicitMoveAssignmentOperators
                 << " implicit move assignment operators created\n";
  llvm::errs() << NumImplicitDestructorsDeclared << "/"
               << NumImplicitDestructors
               << " implicit destructors created\n";

  if (ExternalSource) {
    llvm::errs() << "\n";
    ExternalSource->PrintStats();
  }

  BumpAlloc.PrintStats();
}

void ASTContext::mergeDefinitionIntoModule(NamedDecl *ND, Module *M,
                                           bool NotifyListeners) {
  if (NotifyListeners)
    if (auto *Listener = getASTMutationListener())
      Listener->RedefinedHiddenDefinition(ND, M);

  MergedDefModules[cast<NamedDecl>(ND->getCanonicalDecl())].push_back(M);
}

void ASTContext::deduplicateMergedDefinitonsFor(NamedDecl *ND) {
  auto It = MergedDefModules.find(cast<NamedDecl>(ND->getCanonicalDecl()));
  if (It == MergedDefModules.end())
    return;

  auto &Merged = It->second;
  llvm::DenseSet<Module*> Found;
  for (Module *&M : Merged)
    if (!Found.insert(M).second)
      M = nullptr;
  Merged.erase(std::remove(Merged.begin(), Merged.end(), nullptr), Merged.end());
}

void ASTContext::PerModuleInitializers::resolve(ASTContext &Ctx) {
  if (LazyInitializers.empty())
    return;

  auto *Source = Ctx.getExternalSource();
  assert(Source && "lazy initializers but no external source");

  auto LazyInits = std::move(LazyInitializers);
  LazyInitializers.clear();

  for (auto ID : LazyInits)
    Initializers.push_back(Source->GetExternalDecl(ID));

  assert(LazyInitializers.empty() &&
         "GetExternalDecl for lazy module initializer added more inits");
}

void ASTContext::addModuleInitializer(Module *M, Decl *D) {
  // One special case: if we add a module initializer that imports another
  // module, and that module's only initializer is an ImportDecl, simplify.
  if (const auto *ID = dyn_cast<ImportDecl>(D)) {
    auto It = ModuleInitializers.find(ID->getImportedModule());

    // Maybe the ImportDecl does nothing at all. (Common case.)
    if (It == ModuleInitializers.end())
      return;

    // Maybe the ImportDecl only imports another ImportDecl.
    auto &Imported = *It->second;
    if (Imported.Initializers.size() + Imported.LazyInitializers.size() == 1) {
      Imported.resolve(*this);
      auto *OnlyDecl = Imported.Initializers.front();
      if (isa<ImportDecl>(OnlyDecl))
        D = OnlyDecl;
    }
  }

  auto *&Inits = ModuleInitializers[M];
  if (!Inits)
    Inits = new (*this) PerModuleInitializers;
  Inits->Initializers.push_back(D);
}

void ASTContext::addLazyModuleInitializers(Module *M, ArrayRef<uint32_t> IDs) {
  auto *&Inits = ModuleInitializers[M];
  if (!Inits)
    Inits = new (*this) PerModuleInitializers;
  Inits->LazyInitializers.insert(Inits->LazyInitializers.end(),
                                 IDs.begin(), IDs.end());
}

ArrayRef<Decl *> ASTContext::getModuleInitializers(Module *M) {
  auto It = ModuleInitializers.find(M);
  if (It == ModuleInitializers.end())
    return None;

  auto *Inits = It->second;
  Inits->resolve(*this);
  return Inits->Initializers;
}

ExternCContextDecl *ASTContext::getExternCContextDecl() const {
  if (!ExternCContext)
    ExternCContext = ExternCContextDecl::Create(*this, getTranslationUnitDecl());

  return ExternCContext;
}

BuiltinTemplateDecl *
ASTContext::buildBuiltinTemplateDecl(BuiltinTemplateKind BTK,
                                     const IdentifierInfo *II) const {
  auto *BuiltinTemplate = BuiltinTemplateDecl::Create(*this, TUDecl, II, BTK);
  BuiltinTemplate->setImplicit();
  TUDecl->addDecl(BuiltinTemplate);

  return BuiltinTemplate;
}

BuiltinTemplateDecl *
ASTContext::getMakeIntegerSeqDecl() const {
  if (!MakeIntegerSeqDecl)
    MakeIntegerSeqDecl = buildBuiltinTemplateDecl(BTK__make_integer_seq,
                                                  getMakeIntegerSeqName());
  return MakeIntegerSeqDecl;
}

BuiltinTemplateDecl *
ASTContext::getTypePackElementDecl() const {
  if (!TypePackElementDecl)
    TypePackElementDecl = buildBuiltinTemplateDecl(BTK__type_pack_element,
                                                   getTypePackElementName());
  return TypePackElementDecl;
}

RecordDecl *ASTContext::buildImplicitRecord(StringRef Name,
                                            RecordDecl::TagKind TK) const {
  SourceLocation Loc;
  RecordDecl *NewDecl;
  if (getLangOpts().CPlusPlus)
    NewDecl = CXXRecordDecl::Create(*this, TK, getTranslationUnitDecl(), Loc,
                                    Loc, &Idents.get(Name));
  else
    NewDecl = RecordDecl::Create(*this, TK, getTranslationUnitDecl(), Loc, Loc,
                                 &Idents.get(Name));
  NewDecl->setImplicit();
  NewDecl->addAttr(TypeVisibilityAttr::CreateImplicit(
      const_cast<ASTContext &>(*this), TypeVisibilityAttr::Default));
  return NewDecl;
}

TypedefDecl *ASTContext::buildImplicitTypedef(QualType T,
                                              StringRef Name) const {
  TypeSourceInfo *TInfo = getTrivialTypeSourceInfo(T);
  TypedefDecl *NewDecl = TypedefDecl::Create(
      const_cast<ASTContext &>(*this), getTranslationUnitDecl(),
      SourceLocation(), SourceLocation(), &Idents.get(Name), TInfo);
  NewDecl->setImplicit();
  return NewDecl;
}

TypedefDecl *ASTContext::getInt128Decl() const {
  if (!Int128Decl)
    Int128Decl = buildImplicitTypedef(Int128Ty, "__int128_t");
  return Int128Decl;
}

TypedefDecl *ASTContext::getUInt128Decl() const {
  if (!UInt128Decl)
    UInt128Decl = buildImplicitTypedef(UnsignedInt128Ty, "__uint128_t");
  return UInt128Decl;
}

void ASTContext::InitBuiltinType(CanQualType &R, BuiltinType::Kind K) {
  auto *Ty = new (*this, TypeAlignment) BuiltinType(K);
  R = CanQualType::CreateUnsafe(QualType(Ty, 0));
  Types.push_back(Ty);
}

void ASTContext::InitBuiltinTypes(const TargetInfo &Target,
                                  const TargetInfo *AuxTarget) {
  assert((!this->Target || this->Target == &Target) &&
         "Incorrect target reinitialization");
  assert(VoidTy.isNull() && "Context reinitialized?");

  this->Target = &Target;
  this->AuxTarget = AuxTarget;

  ABI.reset(createCXXABI(Target));
  AddrSpaceMap = getAddressSpaceMap(Target, LangOpts);
  AddrSpaceMapMangling = isAddrSpaceMapManglingEnabled(Target, LangOpts);

  // C99 6.2.5p19.
  InitBuiltinType(VoidTy,              BuiltinType::Void);

  // C99 6.2.5p2.
  InitBuiltinType(BoolTy,              BuiltinType::Bool);
  // C99 6.2.5p3.
  if (LangOpts.CharIsSigned)
    InitBuiltinType(CharTy,            BuiltinType::Char_S);
  else
    InitBuiltinType(CharTy,            BuiltinType::Char_U);
  // C99 6.2.5p4.
  InitBuiltinType(SignedCharTy,        BuiltinType::SChar);
  InitBuiltinType(ShortTy,             BuiltinType::Short);
  InitBuiltinType(IntTy,               BuiltinType::Int);
  InitBuiltinType(LongTy,              BuiltinType::Long);
  InitBuiltinType(LongLongTy,          BuiltinType::LongLong);

  // C99 6.2.5p6.
  InitBuiltinType(UnsignedCharTy,      BuiltinType::UChar);
  InitBuiltinType(UnsignedShortTy,     BuiltinType::UShort);
  InitBuiltinType(UnsignedIntTy,       BuiltinType::UInt);
  InitBuiltinType(UnsignedLongTy,      BuiltinType::ULong);
  InitBuiltinType(UnsignedLongLongTy,  BuiltinType::ULongLong);

  // C99 6.2.5p10.
  InitBuiltinType(FloatTy,             BuiltinType::Float);
  InitBuiltinType(DoubleTy,            BuiltinType::Double);
  InitBuiltinType(LongDoubleTy,        BuiltinType::LongDouble);

  // GNU extension, __float128 for IEEE quadruple precision
  InitBuiltinType(Float128Ty,          BuiltinType::Float128);

  // C11 extension ISO/IEC TS 18661-3
  InitBuiltinType(Float16Ty,           BuiltinType::Float16);

  // ISO/IEC JTC1 SC22 WG14 N1169 Extension
  InitBuiltinType(ShortAccumTy,            BuiltinType::ShortAccum);
  InitBuiltinType(AccumTy,                 BuiltinType::Accum);
  InitBuiltinType(LongAccumTy,             BuiltinType::LongAccum);
  InitBuiltinType(UnsignedShortAccumTy,    BuiltinType::UShortAccum);
  InitBuiltinType(UnsignedAccumTy,         BuiltinType::UAccum);
  InitBuiltinType(UnsignedLongAccumTy,     BuiltinType::ULongAccum);
  InitBuiltinType(ShortFractTy,            BuiltinType::ShortFract);
  InitBuiltinType(FractTy,                 BuiltinType::Fract);
  InitBuiltinType(LongFractTy,             BuiltinType::LongFract);
  InitBuiltinType(UnsignedShortFractTy,    BuiltinType::UShortFract);
  InitBuiltinType(UnsignedFractTy,         BuiltinType::UFract);
  InitBuiltinType(UnsignedLongFractTy,     BuiltinType::ULongFract);
  InitBuiltinType(SatShortAccumTy,         BuiltinType::SatShortAccum);
  InitBuiltinType(SatAccumTy,              BuiltinType::SatAccum);
  InitBuiltinType(SatLongAccumTy,          BuiltinType::SatLongAccum);
  InitBuiltinType(SatUnsignedShortAccumTy, BuiltinType::SatUShortAccum);
  InitBuiltinType(SatUnsignedAccumTy,      BuiltinType::SatUAccum);
  InitBuiltinType(SatUnsignedLongAccumTy,  BuiltinType::SatULongAccum);
  InitBuiltinType(SatShortFractTy,         BuiltinType::SatShortFract);
  InitBuiltinType(SatFractTy,              BuiltinType::SatFract);
  InitBuiltinType(SatLongFractTy,          BuiltinType::SatLongFract);
  InitBuiltinType(SatUnsignedShortFractTy, BuiltinType::SatUShortFract);
  InitBuiltinType(SatUnsignedFractTy,      BuiltinType::SatUFract);
  InitBuiltinType(SatUnsignedLongFractTy,  BuiltinType::SatULongFract);

  // GNU extension, 128-bit integers.
  InitBuiltinType(Int128Ty,            BuiltinType::Int128);
  InitBuiltinType(UnsignedInt128Ty,    BuiltinType::UInt128);

  // C++ 3.9.1p5
  if (TargetInfo::isTypeSigned(Target.getWCharType()))
    InitBuiltinType(WCharTy,           BuiltinType::WChar_S);
  else  // -fshort-wchar makes wchar_t be unsigned.
    InitBuiltinType(WCharTy,           BuiltinType::WChar_U);
  if (LangOpts.CPlusPlus && LangOpts.WChar)
    WideCharTy = WCharTy;
  else {
    // C99 (or C++ using -fno-wchar).
    WideCharTy = getFromTargetType(Target.getWCharType());
  }

  WIntTy = getFromTargetType(Target.getWIntType());

  // C++20 (proposed)
  InitBuiltinType(Char8Ty,              BuiltinType::Char8);

  if (LangOpts.CPlusPlus) // C++0x 3.9.1p5, extension for C++
    InitBuiltinType(Char16Ty,           BuiltinType::Char16);
  else // C99
    Char16Ty = getFromTargetType(Target.getChar16Type());

  if (LangOpts.CPlusPlus) // C++0x 3.9.1p5, extension for C++
    InitBuiltinType(Char32Ty,           BuiltinType::Char32);
  else // C99
    Char32Ty = getFromTargetType(Target.getChar32Type());

  // Placeholder type for type-dependent expressions whose type is
  // completely unknown. No code should ever check a type against
  // DependentTy and users should never see it; however, it is here to
  // help diagnose failures to properly check for type-dependent
  // expressions.
  InitBuiltinType(DependentTy,         BuiltinType::Dependent);

  // Placeholder type for functions.
  InitBuiltinType(OverloadTy,          BuiltinType::Overload);

  // Placeholder type for bound members.
  InitBuiltinType(BoundMemberTy,       BuiltinType::BoundMember);

  // Placeholder type for pseudo-objects.
  InitBuiltinType(PseudoObjectTy,      BuiltinType::PseudoObject);

  // "any" type; useful for debugger-like clients.
  InitBuiltinType(UnknownAnyTy,        BuiltinType::UnknownAny);

  // Placeholder type for unbridged ARC casts.
  InitBuiltinType(ARCUnbridgedCastTy,  BuiltinType::ARCUnbridgedCast);

  // Placeholder type for builtin functions.
  InitBuiltinType(BuiltinFnTy,  BuiltinType::BuiltinFn);

  // Placeholder type for OMP array sections.
  if (LangOpts.OpenMP)
    InitBuiltinType(OMPArraySectionTy, BuiltinType::OMPArraySection);

  // C99 6.2.5p11.
  FloatComplexTy      = getComplexType(FloatTy);
  DoubleComplexTy     = getComplexType(DoubleTy);
  LongDoubleComplexTy = getComplexType(LongDoubleTy);
  Float128ComplexTy   = getComplexType(Float128Ty);

  // Builtin types for 'id', 'Class', and 'SEL'.
  InitBuiltinType(ObjCBuiltinIdTy, BuiltinType::ObjCId);
  InitBuiltinType(ObjCBuiltinClassTy, BuiltinType::ObjCClass);
  InitBuiltinType(ObjCBuiltinSelTy, BuiltinType::ObjCSel);

  if (LangOpts.OpenCL) {
#define IMAGE_TYPE(ImgType, Id, SingletonId, Access, Suffix) \
    InitBuiltinType(SingletonId, BuiltinType::Id);
#include "clang/Basic/OpenCLImageTypes.def"

    InitBuiltinType(OCLSamplerTy, BuiltinType::OCLSampler);
    InitBuiltinType(OCLEventTy, BuiltinType::OCLEvent);
    InitBuiltinType(OCLClkEventTy, BuiltinType::OCLClkEvent);
    InitBuiltinType(OCLQueueTy, BuiltinType::OCLQueue);
    InitBuiltinType(OCLReserveIDTy, BuiltinType::OCLReserveID);

#define EXT_OPAQUE_TYPE(ExtType, Id, Ext) \
    InitBuiltinType(Id##Ty, BuiltinType::Id);
#include "clang/Basic/OpenCLExtensionTypes.def"
  }

  if (Target.hasAArch64SVETypes()) {
#define SVE_TYPE(Name, Id, SingletonId) \
    InitBuiltinType(SingletonId, BuiltinType::Id);
#include "clang/Basic/AArch64SVEACLETypes.def"
  }

  // Builtin type for __objc_yes and __objc_no
  ObjCBuiltinBoolTy = (Target.useSignedCharForObjCBool() ?
                       SignedCharTy : BoolTy);

  ObjCConstantStringType = QualType();

  ObjCSuperType = QualType();

  // void * type
  if (LangOpts.OpenCLVersion >= 200) {
    auto Q = VoidTy.getQualifiers();
    Q.setAddressSpace(LangAS::opencl_generic);
    VoidPtrTy = getPointerType(getCanonicalType(
        getQualifiedType(VoidTy.getUnqualifiedType(), Q)));
  } else {
    VoidPtrTy = getPointerType(VoidTy);
  }

  // nullptr type (C++0x 2.14.7)
  InitBuiltinType(NullPtrTy,           BuiltinType::NullPtr);

  // half type (OpenCL 6.1.1.1) / ARM NEON __fp16
  InitBuiltinType(HalfTy, BuiltinType::Half);

  // Builtin type used to help define __builtin_va_list.
  VaListTagDecl = nullptr;
}

DiagnosticsEngine &ASTContext::getDiagnostics() const {
  return SourceMgr.getDiagnostics();
}

AttrVec& ASTContext::getDeclAttrs(const Decl *D) {
  AttrVec *&Result = DeclAttrs[D];
  if (!Result) {
    void *Mem = Allocate(sizeof(AttrVec));
    Result = new (Mem) AttrVec;
  }

  return *Result;
}

/// Erase the attributes corresponding to the given declaration.
void ASTContext::eraseDeclAttrs(const Decl *D) {
  llvm::DenseMap<const Decl*, AttrVec*>::iterator Pos = DeclAttrs.find(D);
  if (Pos != DeclAttrs.end()) {
    Pos->second->~AttrVec();
    DeclAttrs.erase(Pos);
  }
}

// FIXME: Remove ?
MemberSpecializationInfo *
ASTContext::getInstantiatedFromStaticDataMember(const VarDecl *Var) {
  assert(Var->isStaticDataMember() && "Not a static data member");
  return getTemplateOrSpecializationInfo(Var)
      .dyn_cast<MemberSpecializationInfo *>();
}

ASTContext::TemplateOrSpecializationInfo
ASTContext::getTemplateOrSpecializationInfo(const VarDecl *Var) {
  llvm::DenseMap<const VarDecl *, TemplateOrSpecializationInfo>::iterator Pos =
      TemplateOrInstantiation.find(Var);
  if (Pos == TemplateOrInstantiation.end())
    return {};

  return Pos->second;
}

void
ASTContext::setInstantiatedFromStaticDataMember(VarDecl *Inst, VarDecl *Tmpl,
                                                TemplateSpecializationKind TSK,
                                          SourceLocation PointOfInstantiation) {
  assert(Inst->isStaticDataMember() && "Not a static data member");
  assert(Tmpl->isStaticDataMember() && "Not a static data member");
  setTemplateOrSpecializationInfo(Inst, new (*this) MemberSpecializationInfo(
                                            Tmpl, TSK, PointOfInstantiation));
}

void
ASTContext::setTemplateOrSpecializationInfo(VarDecl *Inst,
                                            TemplateOrSpecializationInfo TSI) {
  assert(!TemplateOrInstantiation[Inst] &&
         "Already noted what the variable was instantiated from");
  TemplateOrInstantiation[Inst] = TSI;
}

NamedDecl *
ASTContext::getInstantiatedFromUsingDecl(NamedDecl *UUD) {
  auto Pos = InstantiatedFromUsingDecl.find(UUD);
  if (Pos == InstantiatedFromUsingDecl.end())
    return nullptr;

  return Pos->second;
}

void
ASTContext::setInstantiatedFromUsingDecl(NamedDecl *Inst, NamedDecl *Pattern) {
  assert((isa<UsingDecl>(Pattern) ||
          isa<UnresolvedUsingValueDecl>(Pattern) ||
          isa<UnresolvedUsingTypenameDecl>(Pattern)) &&
         "pattern decl is not a using decl");
  assert((isa<UsingDecl>(Inst) ||
          isa<UnresolvedUsingValueDecl>(Inst) ||
          isa<UnresolvedUsingTypenameDecl>(Inst)) &&
         "instantiation did not produce a using decl");
  assert(!InstantiatedFromUsingDecl[Inst] && "pattern already exists");
  InstantiatedFromUsingDecl[Inst] = Pattern;
}

UsingShadowDecl *
ASTContext::getInstantiatedFromUsingShadowDecl(UsingShadowDecl *Inst) {
  llvm::DenseMap<UsingShadowDecl*, UsingShadowDecl*>::const_iterator Pos
    = InstantiatedFromUsingShadowDecl.find(Inst);
  if (Pos == InstantiatedFromUsingShadowDecl.end())
    return nullptr;

  return Pos->second;
}

void
ASTContext::setInstantiatedFromUsingShadowDecl(UsingShadowDecl *Inst,
                                               UsingShadowDecl *Pattern) {
  assert(!InstantiatedFromUsingShadowDecl[Inst] && "pattern already exists");
  InstantiatedFromUsingShadowDecl[Inst] = Pattern;
}

FieldDecl *ASTContext::getInstantiatedFromUnnamedFieldDecl(FieldDecl *Field) {
  llvm::DenseMap<FieldDecl *, FieldDecl *>::iterator Pos
    = InstantiatedFromUnnamedFieldDecl.find(Field);
  if (Pos == InstantiatedFromUnnamedFieldDecl.end())
    return nullptr;

  return Pos->second;
}

void ASTContext::setInstantiatedFromUnnamedFieldDecl(FieldDecl *Inst,
                                                     FieldDecl *Tmpl) {
  assert(!Inst->getDeclName() && "Instantiated field decl is not unnamed");
  assert(!Tmpl->getDeclName() && "Template field decl is not unnamed");
  assert(!InstantiatedFromUnnamedFieldDecl[Inst] &&
         "Already noted what unnamed field was instantiated from");

  InstantiatedFromUnnamedFieldDecl[Inst] = Tmpl;
}

ASTContext::overridden_cxx_method_iterator
ASTContext::overridden_methods_begin(const CXXMethodDecl *Method) const {
  return overridden_methods(Method).begin();
}

ASTContext::overridden_cxx_method_iterator
ASTContext::overridden_methods_end(const CXXMethodDecl *Method) const {
  return overridden_methods(Method).end();
}

unsigned
ASTContext::overridden_methods_size(const CXXMethodDecl *Method) const {
  auto Range = overridden_methods(Method);
  return Range.end() - Range.begin();
}

ASTContext::overridden_method_range
ASTContext::overridden_methods(const CXXMethodDecl *Method) const {
  llvm::DenseMap<const CXXMethodDecl *, CXXMethodVector>::const_iterator Pos =
      OverriddenMethods.find(Method->getCanonicalDecl());
  if (Pos == OverriddenMethods.end())
    return overridden_method_range(nullptr, nullptr);
  return overridden_method_range(Pos->second.begin(), Pos->second.end());
}

void ASTContext::addOverriddenMethod(const CXXMethodDecl *Method,
                                     const CXXMethodDecl *Overridden) {
  assert(Method->isCanonicalDecl() && Overridden->isCanonicalDecl());
  OverriddenMethods[Method].push_back(Overridden);
}

void ASTContext::getOverriddenMethods(
                      const NamedDecl *D,
                      SmallVectorImpl<const NamedDecl *> &Overridden) const {
  assert(D);

  if (const auto *CXXMethod = dyn_cast<CXXMethodDecl>(D)) {
    Overridden.append(overridden_methods_begin(CXXMethod),
                      overridden_methods_end(CXXMethod));
    return;
  }

  const auto *Method = dyn_cast<ObjCMethodDecl>(D);
  if (!Method)
    return;

  SmallVector<const ObjCMethodDecl *, 8> OverDecls;
  Method->getOverriddenMethods(OverDecls);
  Overridden.append(OverDecls.begin(), OverDecls.end());
}

void ASTContext::addedLocalImportDecl(ImportDecl *Import) {
  assert(!Import->NextLocalImport && "Import declaration already in the chain");
  assert(!Import->isFromASTFile() && "Non-local import declaration");
  if (!FirstLocalImport) {
    FirstLocalImport = Import;
    LastLocalImport = Import;
    return;
  }

  LastLocalImport->NextLocalImport = Import;
  LastLocalImport = Import;
}

//===----------------------------------------------------------------------===//
//                         Type Sizing and Analysis
//===----------------------------------------------------------------------===//

/// getFloatTypeSemantics - Return the APFloat 'semantics' for the specified
/// scalar floating point type.
const llvm::fltSemantics &ASTContext::getFloatTypeSemantics(QualType T) const {
  switch (T->castAs<BuiltinType>()->getKind()) {
  default:
    llvm_unreachable("Not a floating point type!");
  case BuiltinType::Float16:
  case BuiltinType::Half:
    return Target->getHalfFormat();
  case BuiltinType::Float:      return Target->getFloatFormat();
  case BuiltinType::Double:     return Target->getDoubleFormat();
  case BuiltinType::LongDouble:
    if (getLangOpts().OpenMP && getLangOpts().OpenMPIsDevice)
      return AuxTarget->getLongDoubleFormat();
    return Target->getLongDoubleFormat();
  case BuiltinType::Float128:
    if (getLangOpts().OpenMP && getLangOpts().OpenMPIsDevice)
      return AuxTarget->getFloat128Format();
    return Target->getFloat128Format();
  }
}

CharUnits ASTContext::getDeclAlign(const Decl *D, bool ForAlignof) const {
  unsigned Align = Target->getCharWidth();

  bool UseAlignAttrOnly = false;
  if (unsigned AlignFromAttr = D->getMaxAlignment()) {
    Align = AlignFromAttr;

    // __attribute__((aligned)) can increase or decrease alignment
    // *except* on a struct or struct member, where it only increases
    // alignment unless 'packed' is also specified.
    //
    // It is an error for alignas to decrease alignment, so we can
    // ignore that possibility;  Sema should diagnose it.
    if (isa<FieldDecl>(D)) {
      UseAlignAttrOnly = D->hasAttr<PackedAttr>() ||
        cast<FieldDecl>(D)->getParent()->hasAttr<PackedAttr>();
    } else {
      UseAlignAttrOnly = true;
    }
  }
  else if (isa<FieldDecl>(D))
      UseAlignAttrOnly =
        D->hasAttr<PackedAttr>() ||
        cast<FieldDecl>(D)->getParent()->hasAttr<PackedAttr>();

  // If we're using the align attribute only, just ignore everything
  // else about the declaration and its type.
  if (UseAlignAttrOnly) {
    // do nothing
  } else if (const auto *VD = dyn_cast<ValueDecl>(D)) {
    QualType T = VD->getType();
    if (const auto *RT = T->getAs<ReferenceType>()) {
      if (ForAlignof)
        T = RT->getPointeeType();
      else
        T = getPointerType(RT->getPointeeType());
    }
    QualType BaseT = getBaseElementType(T);
    if (T->isFunctionType())
      Align = getTypeInfoImpl(T.getTypePtr()).Align;
    else if (!BaseT->isIncompleteType()) {
      // Adjust alignments of declarations with array type by the
      // large-array alignment on the target.
      if (const ArrayType *arrayType = getAsArrayType(T)) {
        unsigned MinWidth = Target->getLargeArrayMinWidth();
        if (!ForAlignof && MinWidth) {
          if (isa<VariableArrayType>(arrayType))
            Align = std::max(Align, Target->getLargeArrayAlign());
          else if (isa<ConstantArrayType>(arrayType) &&
                   MinWidth <= getTypeSize(cast<ConstantArrayType>(arrayType)))
            Align = std::max(Align, Target->getLargeArrayAlign());
        }
      }
      Align = std::max(Align, getPreferredTypeAlign(T.getTypePtr()));
      if (BaseT.getQualifiers().hasUnaligned())
        Align = Target->getCharWidth();
      if (const auto *VD = dyn_cast<VarDecl>(D)) {
        if (VD->hasGlobalStorage() && !ForAlignof) {
          uint64_t TypeSize = getTypeSize(T.getTypePtr());
          Align = std::max(Align, getTargetInfo().getMinGlobalAlign(TypeSize));
        }
      }
    }

    // Fields can be subject to extra alignment constraints, like if
    // the field is packed, the struct is packed, or the struct has a
    // a max-field-alignment constraint (#pragma pack).  So calculate
    // the actual alignment of the field within the struct, and then
    // (as we're expected to) constrain that by the alignment of the type.
    if (const auto *Field = dyn_cast<FieldDecl>(VD)) {
      const RecordDecl *Parent = Field->getParent();
      // We can only produce a sensible answer if the record is valid.
      if (!Parent->isInvalidDecl()) {
        const ASTRecordLayout &Layout = getASTRecordLayout(Parent);

        // Start with the record's overall alignment.
        unsigned FieldAlign = toBits(Layout.getAlignment());

        // Use the GCD of that and the offset within the record.
        uint64_t Offset = Layout.getFieldOffset(Field->getFieldIndex());
        if (Offset > 0) {
          // Alignment is always a power of 2, so the GCD will be a power of 2,
          // which means we get to do this crazy thing instead of Euclid's.
          uint64_t LowBitOfOffset = Offset & (~Offset + 1);
          if (LowBitOfOffset < FieldAlign)
            FieldAlign = static_cast<unsigned>(LowBitOfOffset);
        }

        Align = std::min(Align, FieldAlign);
      }
    }
  }

  return toCharUnitsFromBits(Align);
}

// getTypeInfoDataSizeInChars - Return the size of a type, in
// chars. If the type is a record, its data size is returned.  This is
// the size of the memcpy that's performed when assigning this type
// using a trivial copy/move assignment operator.
std::pair<CharUnits, CharUnits>
ASTContext::getTypeInfoDataSizeInChars(QualType T) const {
  std::pair<CharUnits, CharUnits> sizeAndAlign = getTypeInfoInChars(T);

  // In C++, objects can sometimes be allocated into the tail padding
  // of a base-class subobject.  We decide whether that's possible
  // during class layout, so here we can just trust the layout results.
  if (getLangOpts().CPlusPlus) {
    if (const auto *RT = T->getAs<RecordType>()) {
      const ASTRecordLayout &layout = getASTRecordLayout(RT->getDecl());
      sizeAndAlign.first = layout.getDataSize();
    }
  }

  return sizeAndAlign;
}

/// getConstantArrayInfoInChars - Performing the computation in CharUnits
/// instead of in bits prevents overflowing the uint64_t for some large arrays.
std::pair<CharUnits, CharUnits>
static getConstantArrayInfoInChars(const ASTContext &Context,
                                   const ConstantArrayType *CAT) {
  std::pair<CharUnits, CharUnits> EltInfo =
      Context.getTypeInfoInChars(CAT->getElementType());
  uint64_t Size = CAT->getSize().getZExtValue();
  assert((Size == 0 || static_cast<uint64_t>(EltInfo.first.getQuantity()) <=
              (uint64_t)(-1)/Size) &&
         "Overflow in array type char size evaluation");
  uint64_t Width = EltInfo.first.getQuantity() * Size;
  unsigned Align = EltInfo.second.getQuantity();
  if (!Context.getTargetInfo().getCXXABI().isMicrosoft() ||
      Context.getTargetInfo().getPointerWidth(0) == 64)
    Width = llvm::alignTo(Width, Align);
  return std::make_pair(CharUnits::fromQuantity(Width),
                        CharUnits::fromQuantity(Align));
}

std::pair<CharUnits, CharUnits>
ASTContext::getTypeInfoInChars(const Type *T) const {
  if (const auto *CAT = dyn_cast<ConstantArrayType>(T))
    return getConstantArrayInfoInChars(*this, CAT);
  TypeInfo Info = getTypeInfo(T);
  return std::make_pair(toCharUnitsFromBits(Info.Width),
                        toCharUnitsFromBits(Info.Align));
}

std::pair<CharUnits, CharUnits>
ASTContext::getTypeInfoInChars(QualType T) const {
  return getTypeInfoInChars(T.getTypePtr());
}

bool ASTContext::isAlignmentRequired(const Type *T) const {
  return getTypeInfo(T).AlignIsRequired;
}

bool ASTContext::isAlignmentRequired(QualType T) const {
  return isAlignmentRequired(T.getTypePtr());
}

unsigned ASTContext::getTypeAlignIfKnown(QualType T) const {
  // An alignment on a typedef overrides anything else.
  if (const auto *TT = T->getAs<TypedefType>())
    if (unsigned Align = TT->getDecl()->getMaxAlignment())
      return Align;

  // If we have an (array of) complete type, we're done.
  T = getBaseElementType(T);
  if (!T->isIncompleteType())
    return getTypeAlign(T);

  // If we had an array type, its element type might be a typedef
  // type with an alignment attribute.
  if (const auto *TT = T->getAs<TypedefType>())
    if (unsigned Align = TT->getDecl()->getMaxAlignment())
      return Align;

  // Otherwise, see if the declaration of the type had an attribute.
  if (const auto *TT = T->getAs<TagType>())
    return TT->getDecl()->getMaxAlignment();

  return 0;
}

TypeInfo ASTContext::getTypeInfo(const Type *T) const {
  TypeInfoMap::iterator I = MemoizedTypeInfo.find(T);
  if (I != MemoizedTypeInfo.end())
    return I->second;

  // This call can invalidate MemoizedTypeInfo[T], so we need a second lookup.
  TypeInfo TI = getTypeInfoImpl(T);
  MemoizedTypeInfo[T] = TI;
  return TI;
}

/// getTypeInfoImpl - Return the size of the specified type, in bits.  This
/// method does not work on incomplete types.
///
/// FIXME: Pointers into different addr spaces could have different sizes and
/// alignment requirements: getPointerInfo should take an AddrSpace, this
/// should take a QualType, &c.
TypeInfo ASTContext::getTypeInfoImpl(const Type *T) const {
  uint64_t Width = 0;
  unsigned Align = 8;
  bool AlignIsRequired = false;
  unsigned AS = 0;
  switch (T->getTypeClass()) {
#define TYPE(Class, Base)
#define ABSTRACT_TYPE(Class, Base)
#define NON_CANONICAL_TYPE(Class, Base)
#define DEPENDENT_TYPE(Class, Base) case Type::Class:
#define NON_CANONICAL_UNLESS_DEPENDENT_TYPE(Class, Base)                       \
  case Type::Class:                                                            \
  assert(!T->isDependentType() && "should not see dependent types here");      \
  return getTypeInfo(cast<Class##Type>(T)->desugar().getTypePtr());
#include "clang/AST/TypeNodes.inc"
    llvm_unreachable("Should not see dependent types");

  case Type::FunctionNoProto:
  case Type::FunctionProto:
    // GCC extension: alignof(function) = 32 bits
    Width = 0;
    Align = 32;
    break;

  case Type::IncompleteArray:
  case Type::VariableArray:
    Width = 0;
    Align = getTypeAlign(cast<ArrayType>(T)->getElementType());
    break;

  case Type::ConstantArray: {
    const auto *CAT = cast<ConstantArrayType>(T);

    TypeInfo EltInfo = getTypeInfo(CAT->getElementType());
    uint64_t Size = CAT->getSize().getZExtValue();
    assert((Size == 0 || EltInfo.Width <= (uint64_t)(-1) / Size) &&
           "Overflow in array type bit size evaluation");
    Width = EltInfo.Width * Size;
    Align = EltInfo.Align;
    if (!getTargetInfo().getCXXABI().isMicrosoft() ||
        getTargetInfo().getPointerWidth(0) == 64)
      Width = llvm::alignTo(Width, Align);
    break;
  }
  case Type::ExtVector:
  case Type::Vector: {
    const auto *VT = cast<VectorType>(T);
    TypeInfo EltInfo = getTypeInfo(VT->getElementType());
    Width = EltInfo.Width * VT->getNumElements();
    Align = Width;
    // If the alignment is not a power of 2, round up to the next power of 2.
    // This happens for non-power-of-2 length vectors.
    if (Align & (Align-1)) {
      Align = llvm::NextPowerOf2(Align);
      Width = llvm::alignTo(Width, Align);
    }
    // Adjust the alignment based on the target max.
    uint64_t TargetVectorAlign = Target->getMaxVectorAlign();
    if (TargetVectorAlign && TargetVectorAlign < Align)
      Align = TargetVectorAlign;
    break;
  }

  case Type::Builtin:
    switch (cast<BuiltinType>(T)->getKind()) {
    default: llvm_unreachable("Unknown builtin type!");
    case BuiltinType::Void:
      // GCC extension: alignof(void) = 8 bits.
      Width = 0;
      Align = 8;
      break;
    case BuiltinType::Bool:
      Width = Target->getBoolWidth();
      Align = Target->getBoolAlign();
      break;
    case BuiltinType::Char_S:
    case BuiltinType::Char_U:
    case BuiltinType::UChar:
    case BuiltinType::SChar:
    case BuiltinType::Char8:
      Width = Target->getCharWidth();
      Align = Target->getCharAlign();
      break;
    case BuiltinType::WChar_S:
    case BuiltinType::WChar_U:
      Width = Target->getWCharWidth();
      Align = Target->getWCharAlign();
      break;
    case BuiltinType::Char16:
      Width = Target->getChar16Width();
      Align = Target->getChar16Align();
      break;
    case BuiltinType::Char32:
      Width = Target->getChar32Width();
      Align = Target->getChar32Align();
      break;
    case BuiltinType::UShort:
    case BuiltinType::Short:
      Width = Target->getShortWidth();
      Align = Target->getShortAlign();
      break;
    case BuiltinType::UInt:
    case BuiltinType::Int:
      Width = Target->getIntWidth();
      Align = Target->getIntAlign();
      break;
    case BuiltinType::ULong:
    case BuiltinType::Long:
      Width = Target->getLongWidth();
      Align = Target->getLongAlign();
      break;
    case BuiltinType::ULongLong:
    case BuiltinType::LongLong:
      Width = Target->getLongLongWidth();
      Align = Target->getLongLongAlign();
      break;
    case BuiltinType::Int128:
    case BuiltinType::UInt128:
      Width = 128;
      Align = 128; // int128_t is 128-bit aligned on all targets.
      break;
    case BuiltinType::ShortAccum:
    case BuiltinType::UShortAccum:
    case BuiltinType::SatShortAccum:
    case BuiltinType::SatUShortAccum:
      Width = Target->getShortAccumWidth();
      Align = Target->getShortAccumAlign();
      break;
    case BuiltinType::Accum:
    case BuiltinType::UAccum:
    case BuiltinType::SatAccum:
    case BuiltinType::SatUAccum:
      Width = Target->getAccumWidth();
      Align = Target->getAccumAlign();
      break;
    case BuiltinType::LongAccum:
    case BuiltinType::ULongAccum:
    case BuiltinType::SatLongAccum:
    case BuiltinType::SatULongAccum:
      Width = Target->getLongAccumWidth();
      Align = Target->getLongAccumAlign();
      break;
    case BuiltinType::ShortFract:
    case BuiltinType::UShortFract:
    case BuiltinType::SatShortFract:
    case BuiltinType::SatUShortFract:
      Width = Target->getShortFractWidth();
      Align = Target->getShortFractAlign();
      break;
    case BuiltinType::Fract:
    case BuiltinType::UFract:
    case BuiltinType::SatFract:
    case BuiltinType::SatUFract:
      Width = Target->getFractWidth();
      Align = Target->getFractAlign();
      break;
    case BuiltinType::LongFract:
    case BuiltinType::ULongFract:
    case BuiltinType::SatLongFract:
    case BuiltinType::SatULongFract:
      Width = Target->getLongFractWidth();
      Align = Target->getLongFractAlign();
      break;
    case BuiltinType::Float16:
    case BuiltinType::Half:
      if (Target->hasFloat16Type() || !getLangOpts().OpenMP ||
          !getLangOpts().OpenMPIsDevice) {
        Width = Target->getHalfWidth();
        Align = Target->getHalfAlign();
      } else {
        assert(getLangOpts().OpenMP && getLangOpts().OpenMPIsDevice &&
               "Expected OpenMP device compilation.");
        Width = AuxTarget->getHalfWidth();
        Align = AuxTarget->getHalfAlign();
      }
      break;
    case BuiltinType::Float:
      Width = Target->getFloatWidth();
      Align = Target->getFloatAlign();
      break;
    case BuiltinType::Double:
      Width = Target->getDoubleWidth();
      Align = Target->getDoubleAlign();
      break;
    case BuiltinType::LongDouble:
      if (getLangOpts().OpenMP && getLangOpts().OpenMPIsDevice &&
          (Target->getLongDoubleWidth() != AuxTarget->getLongDoubleWidth() ||
           Target->getLongDoubleAlign() != AuxTarget->getLongDoubleAlign())) {
        Width = AuxTarget->getLongDoubleWidth();
        Align = AuxTarget->getLongDoubleAlign();
      } else {
        Width = Target->getLongDoubleWidth();
        Align = Target->getLongDoubleAlign();
      }
      break;
    case BuiltinType::Float128:
      if (Target->hasFloat128Type() || !getLangOpts().OpenMP ||
          !getLangOpts().OpenMPIsDevice) {
        Width = Target->getFloat128Width();
        Align = Target->getFloat128Align();
      } else {
        assert(getLangOpts().OpenMP && getLangOpts().OpenMPIsDevice &&
               "Expected OpenMP device compilation.");
        Width = AuxTarget->getFloat128Width();
        Align = AuxTarget->getFloat128Align();
      }
      break;
    case BuiltinType::NullPtr:
      Width = Target->getPointerWidth(0); // C++ 3.9.1p11: sizeof(nullptr_t)
      Align = Target->getPointerAlign(0); //   == sizeof(void*)
      break;
    case BuiltinType::ObjCId:
    case BuiltinType::ObjCClass:
    case BuiltinType::ObjCSel:
      Width = Target->getPointerWidth(0);
      Align = Target->getPointerAlign(0);
      break;
    case BuiltinType::OCLSampler:
    case BuiltinType::OCLEvent:
    case BuiltinType::OCLClkEvent:
    case BuiltinType::OCLQueue:
    case BuiltinType::OCLReserveID:
#define IMAGE_TYPE(ImgType, Id, SingletonId, Access, Suffix) \
    case BuiltinType::Id:
#include "clang/Basic/OpenCLImageTypes.def"
#define EXT_OPAQUE_TYPE(ExtType, Id, Ext) \
  case BuiltinType::Id:
#include "clang/Basic/OpenCLExtensionTypes.def"
      AS = getTargetAddressSpace(
          Target->getOpenCLTypeAddrSpace(getOpenCLTypeKind(T)));
      Width = Target->getPointerWidth(AS);
      Align = Target->getPointerAlign(AS);
      break;
    // The SVE types are effectively target-specific.  The length of an
    // SVE_VECTOR_TYPE is only known at runtime, but it is always a multiple
    // of 128 bits.  There is one predicate bit for each vector byte, so the
    // length of an SVE_PREDICATE_TYPE is always a multiple of 16 bits.
    //
    // Because the length is only known at runtime, we use a dummy value
    // of 0 for the static length.  The alignment values are those defined
    // by the Procedure Call Standard for the Arm Architecture.
#define SVE_VECTOR_TYPE(Name, Id, SingletonId, ElKind, ElBits, IsSigned, IsFP)\
    case BuiltinType::Id: \
      Width = 0; \
      Align = 128; \
      break;
#define SVE_PREDICATE_TYPE(Name, Id, SingletonId, ElKind) \
    case BuiltinType::Id: \
      Width = 0; \
      Align = 16; \
      break;
#include "clang/Basic/AArch64SVEACLETypes.def"
    }
    break;
  case Type::ObjCObjectPointer:
    Width = Target->getPointerWidth(0);
    Align = Target->getPointerAlign(0);
    break;
  case Type::BlockPointer:
    AS = getTargetAddressSpace(cast<BlockPointerType>(T)->getPointeeType());
    Width = Target->getPointerWidth(AS);
    Align = Target->getPointerAlign(AS);
    break;
  case Type::LValueReference:
  case Type::RValueReference:
    // alignof and sizeof should never enter this code path here, so we go
    // the pointer route.
    AS = getTargetAddressSpace(cast<ReferenceType>(T)->getPointeeType());
    Width = Target->getPointerWidth(AS);
    Align = Target->getPointerAlign(AS);
    break;
  case Type::Pointer:
    AS = getTargetAddressSpace(cast<PointerType>(T)->getPointeeType());
    Width = Target->getPointerWidth(AS);
    Align = Target->getPointerAlign(AS);
    break;
  case Type::MemberPointer: {
    const auto *MPT = cast<MemberPointerType>(T);
    CXXABI::MemberPointerInfo MPI = ABI->getMemberPointerInfo(MPT);
    Width = MPI.Width;
    Align = MPI.Align;
    break;
  }
  case Type::Complex: {
    // Complex types have the same alignment as their elements, but twice the
    // size.
    TypeInfo EltInfo = getTypeInfo(cast<ComplexType>(T)->getElementType());
    Width = EltInfo.Width * 2;
    Align = EltInfo.Align;
    break;
  }
  case Type::ObjCObject:
    return getTypeInfo(cast<ObjCObjectType>(T)->getBaseType().getTypePtr());
  case Type::Adjusted:
  case Type::Decayed:
    return getTypeInfo(cast<AdjustedType>(T)->getAdjustedType().getTypePtr());
  case Type::ObjCInterface: {
    const auto *ObjCI = cast<ObjCInterfaceType>(T);
    const ASTRecordLayout &Layout = getASTObjCInterfaceLayout(ObjCI->getDecl());
    Width = toBits(Layout.getSize());
    Align = toBits(Layout.getAlignment());
    break;
  }
  case Type::Record:
  case Type::Enum: {
    const auto *TT = cast<TagType>(T);

    if (TT->getDecl()->isInvalidDecl()) {
      Width = 8;
      Align = 8;
      break;
    }

    if (const auto *ET = dyn_cast<EnumType>(TT)) {
      const EnumDecl *ED = ET->getDecl();
      TypeInfo Info =
          getTypeInfo(ED->getIntegerType()->getUnqualifiedDesugaredType());
      if (unsigned AttrAlign = ED->getMaxAlignment()) {
        Info.Align = AttrAlign;
        Info.AlignIsRequired = true;
      }
      return Info;
    }

    const auto *RT = cast<RecordType>(TT);
    const RecordDecl *RD = RT->getDecl();
    const ASTRecordLayout &Layout = getASTRecordLayout(RD);
    Width = toBits(Layout.getSize());
    Align = toBits(Layout.getAlignment());
    AlignIsRequired = RD->hasAttr<AlignedAttr>();
    break;
  }

  case Type::SubstTemplateTypeParm:
    return getTypeInfo(cast<SubstTemplateTypeParmType>(T)->
                       getReplacementType().getTypePtr());

  case Type::Auto:
  case Type::DeducedTemplateSpecialization: {
    const auto *A = cast<DeducedType>(T);
    assert(!A->getDeducedType().isNull() &&
           "cannot request the size of an undeduced or dependent auto type");
    return getTypeInfo(A->getDeducedType().getTypePtr());
  }

  case Type::Paren:
    return getTypeInfo(cast<ParenType>(T)->getInnerType().getTypePtr());

  case Type::MacroQualified:
    return getTypeInfo(
        cast<MacroQualifiedType>(T)->getUnderlyingType().getTypePtr());

  case Type::ObjCTypeParam:
    return getTypeInfo(cast<ObjCTypeParamType>(T)->desugar().getTypePtr());

  case Type::Typedef: {
    const TypedefNameDecl *Typedef = cast<TypedefType>(T)->getDecl();
    TypeInfo Info = getTypeInfo(Typedef->getUnderlyingType().getTypePtr());
    // If the typedef has an aligned attribute on it, it overrides any computed
    // alignment we have.  This violates the GCC documentation (which says that
    // attribute(aligned) can only round up) but matches its implementation.
    if (unsigned AttrAlign = Typedef->getMaxAlignment()) {
      Align = AttrAlign;
      AlignIsRequired = true;
    } else {
      Align = Info.Align;
      AlignIsRequired = Info.AlignIsRequired;
    }
    Width = Info.Width;
    break;
  }

  case Type::Elaborated:
    return getTypeInfo(cast<ElaboratedType>(T)->getNamedType().getTypePtr());

  case Type::Attributed:
    return getTypeInfo(
                  cast<AttributedType>(T)->getEquivalentType().getTypePtr());

  case Type::Atomic: {
    // Start with the base type information.
    TypeInfo Info = getTypeInfo(cast<AtomicType>(T)->getValueType());
    Width = Info.Width;
    Align = Info.Align;

    if (!Width) {
      // An otherwise zero-sized type should still generate an
      // atomic operation.
      Width = Target->getCharWidth();
      assert(Align);
    } else if (Width <= Target->getMaxAtomicPromoteWidth()) {
      // If the size of the type doesn't exceed the platform's max
      // atomic promotion width, make the size and alignment more
      // favorable to atomic operations:

      // Round the size up to a power of 2.
      if (!llvm::isPowerOf2_64(Width))
        Width = llvm::NextPowerOf2(Width);

      // Set the alignment equal to the size.
      Align = static_cast<unsigned>(Width);
    }
  }
  break;

  case Type::Pipe:
    Width = Target->getPointerWidth(getTargetAddressSpace(LangAS::opencl_global));
    Align = Target->getPointerAlign(getTargetAddressSpace(LangAS::opencl_global));
    break;
  }

  assert(llvm::isPowerOf2_32(Align) && "Alignment must be power of 2");
  return TypeInfo(Width, Align, AlignIsRequired);
}

unsigned ASTContext::getTypeUnadjustedAlign(const Type *T) const {
  UnadjustedAlignMap::iterator I = MemoizedUnadjustedAlign.find(T);
  if (I != MemoizedUnadjustedAlign.end())
    return I->second;

  unsigned UnadjustedAlign;
  if (const auto *RT = T->getAs<RecordType>()) {
    const RecordDecl *RD = RT->getDecl();
    const ASTRecordLayout &Layout = getASTRecordLayout(RD);
    UnadjustedAlign = toBits(Layout.getUnadjustedAlignment());
  } else if (const auto *ObjCI = T->getAs<ObjCInterfaceType>()) {
    const ASTRecordLayout &Layout = getASTObjCInterfaceLayout(ObjCI->getDecl());
    UnadjustedAlign = toBits(Layout.getUnadjustedAlignment());
  } else {
    UnadjustedAlign = getTypeAlign(T->getUnqualifiedDesugaredType());
  }

  MemoizedUnadjustedAlign[T] = UnadjustedAlign;
  return UnadjustedAlign;
}

unsigned ASTContext::getOpenMPDefaultSimdAlign(QualType T) const {
  unsigned SimdAlign = getTargetInfo().getSimdDefaultAlign();
  // Target ppc64 with QPX: simd default alignment for pointer to double is 32.
  if ((getTargetInfo().getTriple().getArch() == llvm::Triple::ppc64 ||
       getTargetInfo().getTriple().getArch() == llvm::Triple::ppc64le) &&
      getTargetInfo().getABI() == "elfv1-qpx" &&
      T->isSpecificBuiltinType(BuiltinType::Double))
    SimdAlign = 256;
  return SimdAlign;
}

/// toCharUnitsFromBits - Convert a size in bits to a size in characters.
CharUnits ASTContext::toCharUnitsFromBits(int64_t BitSize) const {
  return CharUnits::fromQuantity(BitSize / getCharWidth());
}

/// toBits - Convert a size in characters to a size in characters.
int64_t ASTContext::toBits(CharUnits CharSize) const {
  return CharSize.getQuantity() * getCharWidth();
}

/// getTypeSizeInChars - Return the size of the specified type, in characters.
/// This method does not work on incomplete types.
CharUnits ASTContext::getTypeSizeInChars(QualType T) const {
  return getTypeInfoInChars(T).first;
}
CharUnits ASTContext::getTypeSizeInChars(const Type *T) const {
  return getTypeInfoInChars(T).first;
}

/// getTypeAlignInChars - Return the ABI-specified alignment of a type, in
/// characters. This method does not work on incomplete types.
CharUnits ASTContext::getTypeAlignInChars(QualType T) const {
  return toCharUnitsFromBits(getTypeAlign(T));
}
CharUnits ASTContext::getTypeAlignInChars(const Type *T) const {
  return toCharUnitsFromBits(getTypeAlign(T));
}

/// getTypeUnadjustedAlignInChars - Return the ABI-specified alignment of a
/// type, in characters, before alignment adustments. This method does
/// not work on incomplete types.
CharUnits ASTContext::getTypeUnadjustedAlignInChars(QualType T) const {
  return toCharUnitsFromBits(getTypeUnadjustedAlign(T));
}
CharUnits ASTContext::getTypeUnadjustedAlignInChars(const Type *T) const {
  return toCharUnitsFromBits(getTypeUnadjustedAlign(T));
}

/// getPreferredTypeAlign - Return the "preferred" alignment of the specified
/// type for the current target in bits.  This can be different than the ABI
/// alignment in cases where it is beneficial for performance to overalign
/// a data type.
unsigned ASTContext::getPreferredTypeAlign(const Type *T) const {
  TypeInfo TI = getTypeInfo(T);
  unsigned ABIAlign = TI.Align;

  T = T->getBaseElementTypeUnsafe();

  // The preferred alignment of member pointers is that of a pointer.
  if (T->isMemberPointerType())
    return getPreferredTypeAlign(getPointerDiffType().getTypePtr());

  if (!Target->allowsLargerPreferedTypeAlignment())
    return ABIAlign;

  // Double and long long should be naturally aligned if possible.
  if (const auto *CT = T->getAs<ComplexType>())
    T = CT->getElementType().getTypePtr();
  if (const auto *ET = T->getAs<EnumType>())
    T = ET->getDecl()->getIntegerType().getTypePtr();
  if (T->isSpecificBuiltinType(BuiltinType::Double) ||
      T->isSpecificBuiltinType(BuiltinType::LongLong) ||
      T->isSpecificBuiltinType(BuiltinType::ULongLong))
    // Don't increase the alignment if an alignment attribute was specified on a
    // typedef declaration.
    if (!TI.AlignIsRequired)
      return std::max(ABIAlign, (unsigned)getTypeSize(T));

  return ABIAlign;
}

/// getTargetDefaultAlignForAttributeAligned - Return the default alignment
/// for __attribute__((aligned)) on this target, to be used if no alignment
/// value is specified.
unsigned ASTContext::getTargetDefaultAlignForAttributeAligned() const {
  return getTargetInfo().getDefaultAlignForAttributeAligned();
}

/// getAlignOfGlobalVar - Return the alignment in bits that should be given
/// to a global variable of the specified type.
unsigned ASTContext::getAlignOfGlobalVar(QualType T) const {
  uint64_t TypeSize = getTypeSize(T.getTypePtr());
  return std::max(getTypeAlign(T), getTargetInfo().getMinGlobalAlign(TypeSize));
}

/// getAlignOfGlobalVarInChars - Return the alignment in characters that
/// should be given to a global variable of the specified type.
CharUnits ASTContext::getAlignOfGlobalVarInChars(QualType T) const {
  return toCharUnitsFromBits(getAlignOfGlobalVar(T));
}

CharUnits ASTContext::getOffsetOfBaseWithVBPtr(const CXXRecordDecl *RD) const {
  CharUnits Offset = CharUnits::Zero();
  const ASTRecordLayout *Layout = &getASTRecordLayout(RD);
  while (const CXXRecordDecl *Base = Layout->getBaseSharingVBPtr()) {
    Offset += Layout->getBaseClassOffset(Base);
    Layout = &getASTRecordLayout(Base);
  }
  return Offset;
}

/// DeepCollectObjCIvars -
/// This routine first collects all declared, but not synthesized, ivars in
/// super class and then collects all ivars, including those synthesized for
/// current class. This routine is used for implementation of current class
/// when all ivars, declared and synthesized are known.
void ASTContext::DeepCollectObjCIvars(const ObjCInterfaceDecl *OI,
                                      bool leafClass,
                            SmallVectorImpl<const ObjCIvarDecl*> &Ivars) const {
  if (const ObjCInterfaceDecl *SuperClass = OI->getSuperClass())
    DeepCollectObjCIvars(SuperClass, false, Ivars);
  if (!leafClass) {
    for (const auto *I : OI->ivars())
      Ivars.push_back(I);
  } else {
    auto *IDecl = const_cast<ObjCInterfaceDecl *>(OI);
    for (const ObjCIvarDecl *Iv = IDecl->all_declared_ivar_begin(); Iv;
         Iv= Iv->getNextIvar())
      Ivars.push_back(Iv);
  }
}

/// CollectInheritedProtocols - Collect all protocols in current class and
/// those inherited by it.
void ASTContext::CollectInheritedProtocols(const Decl *CDecl,
                          llvm::SmallPtrSet<ObjCProtocolDecl*, 8> &Protocols) {
  if (const auto *OI = dyn_cast<ObjCInterfaceDecl>(CDecl)) {
    // We can use protocol_iterator here instead of
    // all_referenced_protocol_iterator since we are walking all categories.
    for (auto *Proto : OI->all_referenced_protocols()) {
      CollectInheritedProtocols(Proto, Protocols);
    }

    // Categories of this Interface.
    for (const auto *Cat : OI->visible_categories())
      CollectInheritedProtocols(Cat, Protocols);

    if (ObjCInterfaceDecl *SD = OI->getSuperClass())
      while (SD) {
        CollectInheritedProtocols(SD, Protocols);
        SD = SD->getSuperClass();
      }
  } else if (const auto *OC = dyn_cast<ObjCCategoryDecl>(CDecl)) {
    for (auto *Proto : OC->protocols()) {
      CollectInheritedProtocols(Proto, Protocols);
    }
  } else if (const auto *OP = dyn_cast<ObjCProtocolDecl>(CDecl)) {
    // Insert the protocol.
    if (!Protocols.insert(
          const_cast<ObjCProtocolDecl *>(OP->getCanonicalDecl())).second)
      return;

    for (auto *Proto : OP->protocols())
      CollectInheritedProtocols(Proto, Protocols);
  }
}

static bool unionHasUniqueObjectRepresentations(const ASTContext &Context,
                                                const RecordDecl *RD) {
  assert(RD->isUnion() && "Must be union type");
  CharUnits UnionSize = Context.getTypeSizeInChars(RD->getTypeForDecl());

  for (const auto *Field : RD->fields()) {
    if (!Context.hasUniqueObjectRepresentations(Field->getType()))
      return false;
    CharUnits FieldSize = Context.getTypeSizeInChars(Field->getType());
    if (FieldSize != UnionSize)
      return false;
  }
  return !RD->field_empty();
}

static bool isStructEmpty(QualType Ty) {
  const RecordDecl *RD = Ty->castAs<RecordType>()->getDecl();

  if (!RD->field_empty())
    return false;

  if (const auto *ClassDecl = dyn_cast<CXXRecordDecl>(RD))
    return ClassDecl->isEmpty();

  return true;
}

static llvm::Optional<int64_t>
structHasUniqueObjectRepresentations(const ASTContext &Context,
                                     const RecordDecl *RD) {
  assert(!RD->isUnion() && "Must be struct/class type");
  const auto &Layout = Context.getASTRecordLayout(RD);

  int64_t CurOffsetInBits = 0;
  if (const auto *ClassDecl = dyn_cast<CXXRecordDecl>(RD)) {
    if (ClassDecl->isDynamicClass())
      return llvm::None;

    SmallVector<std::pair<QualType, int64_t>, 4> Bases;
    for (const auto Base : ClassDecl->bases()) {
      // Empty types can be inherited from, and non-empty types can potentially
      // have tail padding, so just make sure there isn't an error.
      if (!isStructEmpty(Base.getType())) {
        llvm::Optional<int64_t> Size = structHasUniqueObjectRepresentations(
            Context, Base.getType()->castAs<RecordType>()->getDecl());
        if (!Size)
          return llvm::None;
        Bases.emplace_back(Base.getType(), Size.getValue());
      }
    }

    llvm::sort(Bases, [&](const std::pair<QualType, int64_t> &L,
                          const std::pair<QualType, int64_t> &R) {
      return Layout.getBaseClassOffset(L.first->getAsCXXRecordDecl()) <
             Layout.getBaseClassOffset(R.first->getAsCXXRecordDecl());
    });

    for (const auto Base : Bases) {
      int64_t BaseOffset = Context.toBits(
          Layout.getBaseClassOffset(Base.first->getAsCXXRecordDecl()));
      int64_t BaseSize = Base.second;
      if (BaseOffset != CurOffsetInBits)
        return llvm::None;
      CurOffsetInBits = BaseOffset + BaseSize;
    }
  }

  for (const auto *Field : RD->fields()) {
    if (!Field->getType()->isReferenceType() &&
        !Context.hasUniqueObjectRepresentations(Field->getType()))
      return llvm::None;

    int64_t FieldSizeInBits =
        Context.toBits(Context.getTypeSizeInChars(Field->getType()));
    if (Field->isBitField()) {
      int64_t BitfieldSize = Field->getBitWidthValue(Context);

      if (BitfieldSize > FieldSizeInBits)
        return llvm::None;
      FieldSizeInBits = BitfieldSize;
    }

    int64_t FieldOffsetInBits = Context.getFieldOffset(Field);

    if (FieldOffsetInBits != CurOffsetInBits)
      return llvm::None;

    CurOffsetInBits = FieldSizeInBits + FieldOffsetInBits;
  }

  return CurOffsetInBits;
}

bool ASTContext::hasUniqueObjectRepresentations(QualType Ty) const {
  // C++17 [meta.unary.prop]:
  //   The predicate condition for a template specialization
  //   has_unique_object_representations<T> shall be
  //   satisfied if and only if:
  //     (9.1) - T is trivially copyable, and
  //     (9.2) - any two objects of type T with the same value have the same
  //     object representation, where two objects
  //   of array or non-union class type are considered to have the same value
  //   if their respective sequences of
  //   direct subobjects have the same values, and two objects of union type
  //   are considered to have the same
  //   value if they have the same active member and the corresponding members
  //   have the same value.
  //   The set of scalar types for which this condition holds is
  //   implementation-defined. [ Note: If a type has padding
  //   bits, the condition does not hold; otherwise, the condition holds true
  //   for unsigned integral types. -- end note ]
  assert(!Ty.isNull() && "Null QualType sent to unique object rep check");

  // Arrays are unique only if their element type is unique.
  if (Ty->isArrayType())
    return hasUniqueObjectRepresentations(getBaseElementType(Ty));

  // (9.1) - T is trivially copyable...
  if (!Ty.isTriviallyCopyableType(*this))
    return false;

  // All integrals and enums are unique.
  if (Ty->isIntegralOrEnumerationType())
    return true;

  // All other pointers are unique.
  if (Ty->isPointerType())
    return true;

  if (Ty->isMemberPointerType()) {
    const auto *MPT = Ty->getAs<MemberPointerType>();
    return !ABI->getMemberPointerInfo(MPT).HasPadding;
  }

  if (Ty->isRecordType()) {
    const RecordDecl *Record = Ty->castAs<RecordType>()->getDecl();

    if (Record->isInvalidDecl())
      return false;

    if (Record->isUnion())
      return unionHasUniqueObjectRepresentations(*this, Record);

    Optional<int64_t> StructSize =
        structHasUniqueObjectRepresentations(*this, Record);

    return StructSize &&
           StructSize.getValue() == static_cast<int64_t>(getTypeSize(Ty));
  }

  // FIXME: More cases to handle here (list by rsmith):
  // vectors (careful about, eg, vector of 3 foo)
  // _Complex int and friends
  // _Atomic T
  // Obj-C block pointers
  // Obj-C object pointers
  // and perhaps OpenCL's various builtin types (pipe, sampler_t, event_t,
  // clk_event_t, queue_t, reserve_id_t)
  // There're also Obj-C class types and the Obj-C selector type, but I think it
  // makes sense for those to return false here.

  return false;
}

unsigned ASTContext::CountNonClassIvars(const ObjCInterfaceDecl *OI) const {
  unsigned count = 0;
  // Count ivars declared in class extension.
  for (const auto *Ext : OI->known_extensions())
    count += Ext->ivar_size();

  // Count ivar defined in this class's implementation.  This
  // includes synthesized ivars.
  if (ObjCImplementationDecl *ImplDecl = OI->getImplementation())
    count += ImplDecl->ivar_size();

  return count;
}

bool ASTContext::isSentinelNullExpr(const Expr *E) {
  if (!E)
    return false;

  // nullptr_t is always treated as null.
  if (E->getType()->isNullPtrType()) return true;

  if (E->getType()->isAnyPointerType() &&
      E->IgnoreParenCasts()->isNullPointerConstant(*this,
                                                Expr::NPC_ValueDependentIsNull))
    return true;

  // Unfortunately, __null has type 'int'.
  if (isa<GNUNullExpr>(E)) return true;

  return false;
}

/// Get the implementation of ObjCInterfaceDecl, or nullptr if none
/// exists.
ObjCImplementationDecl *ASTContext::getObjCImplementation(ObjCInterfaceDecl *D) {
  llvm::DenseMap<ObjCContainerDecl*, ObjCImplDecl*>::iterator
    I = ObjCImpls.find(D);
  if (I != ObjCImpls.end())
    return cast<ObjCImplementationDecl>(I->second);
  return nullptr;
}

/// Get the implementation of ObjCCategoryDecl, or nullptr if none
/// exists.
ObjCCategoryImplDecl *ASTContext::getObjCImplementation(ObjCCategoryDecl *D) {
  llvm::DenseMap<ObjCContainerDecl*, ObjCImplDecl*>::iterator
    I = ObjCImpls.find(D);
  if (I != ObjCImpls.end())
    return cast<ObjCCategoryImplDecl>(I->second);
  return nullptr;
}

/// Set the implementation of ObjCInterfaceDecl.
void ASTContext::setObjCImplementation(ObjCInterfaceDecl *IFaceD,
                           ObjCImplementationDecl *ImplD) {
  assert(IFaceD && ImplD && "Passed null params");
  ObjCImpls[IFaceD] = ImplD;
}

/// Set the implementation of ObjCCategoryDecl.
void ASTContext::setObjCImplementation(ObjCCategoryDecl *CatD,
                           ObjCCategoryImplDecl *ImplD) {
  assert(CatD && ImplD && "Passed null params");
  ObjCImpls[CatD] = ImplD;
}

const ObjCMethodDecl *
ASTContext::getObjCMethodRedeclaration(const ObjCMethodDecl *MD) const {
  return ObjCMethodRedecls.lookup(MD);
}

void ASTContext::setObjCMethodRedeclaration(const ObjCMethodDecl *MD,
                                            const ObjCMethodDecl *Redecl) {
  assert(!getObjCMethodRedeclaration(MD) && "MD already has a redeclaration");
  ObjCMethodRedecls[MD] = Redecl;
}

const ObjCInterfaceDecl *ASTContext::getObjContainingInterface(
                                              const NamedDecl *ND) const {
  if (const auto *ID = dyn_cast<ObjCInterfaceDecl>(ND->getDeclContext()))
    return ID;
  if (const auto *CD = dyn_cast<ObjCCategoryDecl>(ND->getDeclContext()))
    return CD->getClassInterface();
  if (const auto *IMD = dyn_cast<ObjCImplDecl>(ND->getDeclContext()))
    return IMD->getClassInterface();

  return nullptr;
}

/// Get the copy initialization expression of VarDecl, or nullptr if
/// none exists.
ASTContext::BlockVarCopyInit
ASTContext::getBlockVarCopyInit(const VarDecl*VD) const {
  assert(VD && "Passed null params");
  assert(VD->hasAttr<BlocksAttr>() &&
         "getBlockVarCopyInits - not __block var");
  auto I = BlockVarCopyInits.find(VD);
  if (I != BlockVarCopyInits.end())
    return I->second;
  return {nullptr, false};
}

/// Set the copy initialization expression of a block var decl.
void ASTContext::setBlockVarCopyInit(const VarDecl*VD, Expr *CopyExpr,
                                     bool CanThrow) {
  assert(VD && CopyExpr && "Passed null params");
  assert(VD->hasAttr<BlocksAttr>() &&
         "setBlockVarCopyInits - not __block var");
  BlockVarCopyInits[VD].setExprAndFlag(CopyExpr, CanThrow);
}

TypeSourceInfo *ASTContext::CreateTypeSourceInfo(QualType T,
                                                 unsigned DataSize) const {
  if (!DataSize)
    DataSize = TypeLoc::getFullDataSizeForType(T);
  else
    assert(DataSize == TypeLoc::getFullDataSizeForType(T) &&
           "incorrect data size provided to CreateTypeSourceInfo!");

  auto *TInfo =
    (TypeSourceInfo*)BumpAlloc.Allocate(sizeof(TypeSourceInfo) + DataSize, 8);
  new (TInfo) TypeSourceInfo(T);
  return TInfo;
}

TypeSourceInfo *ASTContext::getTrivialTypeSourceInfo(QualType T,
                                                     SourceLocation L) const {
  TypeSourceInfo *DI = CreateTypeSourceInfo(T);
  DI->getTypeLoc().initialize(const_cast<ASTContext &>(*this), L);
  return DI;
}

const ASTRecordLayout &
ASTContext::getASTObjCInterfaceLayout(const ObjCInterfaceDecl *D) const {
  return getObjCLayout(D, nullptr);
}

const ASTRecordLayout &
ASTContext::getASTObjCImplementationLayout(
                                        const ObjCImplementationDecl *D) const {
  return getObjCLayout(D->getClassInterface(), D);
}

//===----------------------------------------------------------------------===//
//                   Type creation/memoization methods
//===----------------------------------------------------------------------===//

QualType
ASTContext::getExtQualType(const Type *baseType, Qualifiers quals) const {
  unsigned fastQuals = quals.getFastQualifiers();
  quals.removeFastQualifiers();

  // Check if we've already instantiated this type.
  llvm::FoldingSetNodeID ID;
  ExtQuals::Profile(ID, baseType, quals);
  void *insertPos = nullptr;
  if (ExtQuals *eq = ExtQualNodes.FindNodeOrInsertPos(ID, insertPos)) {
    assert(eq->getQualifiers() == quals);
    return QualType(eq, fastQuals);
  }

  // If the base type is not canonical, make the appropriate canonical type.
  QualType canon;
  if (!baseType->isCanonicalUnqualified()) {
    SplitQualType canonSplit = baseType->getCanonicalTypeInternal().split();
    canonSplit.Quals.addConsistentQualifiers(quals);
    canon = getExtQualType(canonSplit.Ty, canonSplit.Quals);

    // Re-find the insert position.
    (void) ExtQualNodes.FindNodeOrInsertPos(ID, insertPos);
  }

  auto *eq = new (*this, TypeAlignment) ExtQuals(baseType, canon, quals);
  ExtQualNodes.InsertNode(eq, insertPos);
  return QualType(eq, fastQuals);
}

QualType ASTContext::getAddrSpaceQualType(QualType T,
                                          LangAS AddressSpace) const {
  QualType CanT = getCanonicalType(T);
  if (CanT.getAddressSpace() == AddressSpace)
    return T;

  // If we are composing extended qualifiers together, merge together
  // into one ExtQuals node.
  QualifierCollector Quals;
  const Type *TypeNode = Quals.strip(T);

  // If this type already has an address space specified, it cannot get
  // another one.
  assert(!Quals.hasAddressSpace() &&
         "Type cannot be in multiple addr spaces!");
  Quals.addAddressSpace(AddressSpace);

  return getExtQualType(TypeNode, Quals);
}

QualType ASTContext::removeAddrSpaceQualType(QualType T) const {
  // If we are composing extended qualifiers together, merge together
  // into one ExtQuals node.
  QualifierCollector Quals;
  const Type *TypeNode = Quals.strip(T);

  // If the qualifier doesn't have an address space just return it.
  if (!Quals.hasAddressSpace())
    return T;

  Quals.removeAddressSpace();

  // Removal of the address space can mean there are no longer any
  // non-fast qualifiers, so creating an ExtQualType isn't possible (asserts)
  // or required.
  if (Quals.hasNonFastQualifiers())
    return getExtQualType(TypeNode, Quals);
  else
    return QualType(TypeNode, Quals.getFastQualifiers());
}

QualType ASTContext::getObjCGCQualType(QualType T,
                                       Qualifiers::GC GCAttr) const {
  QualType CanT = getCanonicalType(T);
  if (CanT.getObjCGCAttr() == GCAttr)
    return T;

  if (const auto *ptr = T->getAs<PointerType>()) {
    QualType Pointee = ptr->getPointeeType();
    if (Pointee->isAnyPointerType()) {
      QualType ResultType = getObjCGCQualType(Pointee, GCAttr);
      return getPointerType(ResultType);
    }
  }

  // If we are composing extended qualifiers together, merge together
  // into one ExtQuals node.
  QualifierCollector Quals;
  const Type *TypeNode = Quals.strip(T);

  // If this type already has an ObjCGC specified, it cannot get
  // another one.
  assert(!Quals.hasObjCGCAttr() &&
         "Type cannot have multiple ObjCGCs!");
  Quals.addObjCGCAttr(GCAttr);

  return getExtQualType(TypeNode, Quals);
}

const FunctionType *ASTContext::adjustFunctionType(const FunctionType *T,
                                                   FunctionType::ExtInfo Info) {
  if (T->getExtInfo() == Info)
    return T;

  QualType Result;
  if (const auto *FNPT = dyn_cast<FunctionNoProtoType>(T)) {
    Result = getFunctionNoProtoType(FNPT->getReturnType(), Info);
  } else {
    const auto *FPT = cast<FunctionProtoType>(T);
    FunctionProtoType::ExtProtoInfo EPI = FPT->getExtProtoInfo();
    EPI.ExtInfo = Info;
    Result = getFunctionType(FPT->getReturnType(), FPT->getParamTypes(), EPI);
  }

  return cast<FunctionType>(Result.getTypePtr());
}

void ASTContext::adjustDeducedFunctionResultType(FunctionDecl *FD,
                                                 QualType ResultType) {
  FD = FD->getMostRecentDecl();
  while (true) {
    const auto *FPT = FD->getType()->castAs<FunctionProtoType>();
    FunctionProtoType::ExtProtoInfo EPI = FPT->getExtProtoInfo();
    FD->setType(getFunctionType(ResultType, FPT->getParamTypes(), EPI));
    if (FunctionDecl *Next = FD->getPreviousDecl())
      FD = Next;
    else
      break;
  }
  if (ASTMutationListener *L = getASTMutationListener())
    L->DeducedReturnType(FD, ResultType);
}

/// Get a function type and produce the equivalent function type with the
/// specified exception specification. Type sugar that can be present on a
/// declaration of a function with an exception specification is permitted
/// and preserved. Other type sugar (for instance, typedefs) is not.
QualType ASTContext::getFunctionTypeWithExceptionSpec(
    QualType Orig, const FunctionProtoType::ExceptionSpecInfo &ESI) {
  // Might have some parens.
  if (const auto *PT = dyn_cast<ParenType>(Orig))
    return getParenType(
        getFunctionTypeWithExceptionSpec(PT->getInnerType(), ESI));

  // Might be wrapped in a macro qualified type.
  if (const auto *MQT = dyn_cast<MacroQualifiedType>(Orig))
    return getMacroQualifiedType(
        getFunctionTypeWithExceptionSpec(MQT->getUnderlyingType(), ESI),
        MQT->getMacroIdentifier());

  // Might have a calling-convention attribute.
  if (const auto *AT = dyn_cast<AttributedType>(Orig))
    return getAttributedType(
        AT->getAttrKind(),
        getFunctionTypeWithExceptionSpec(AT->getModifiedType(), ESI),
        getFunctionTypeWithExceptionSpec(AT->getEquivalentType(), ESI));

  // Anything else must be a function type. Rebuild it with the new exception
  // specification.
  const auto *Proto = Orig->castAs<FunctionProtoType>();
  return getFunctionType(
      Proto->getReturnType(), Proto->getParamTypes(),
      Proto->getExtProtoInfo().withExceptionSpec(ESI));
}

bool ASTContext::hasSameFunctionTypeIgnoringExceptionSpec(QualType T,
                                                          QualType U) {
  return hasSameType(T, U) ||
         (getLangOpts().CPlusPlus17 &&
          hasSameType(getFunctionTypeWithExceptionSpec(T, EST_None),
                      getFunctionTypeWithExceptionSpec(U, EST_None)));
}

void ASTContext::adjustExceptionSpec(
    FunctionDecl *FD, const FunctionProtoType::ExceptionSpecInfo &ESI,
    bool AsWritten) {
  // Update the type.
  QualType Updated =
      getFunctionTypeWithExceptionSpec(FD->getType(), ESI);
  FD->setType(Updated);

  if (!AsWritten)
    return;

  // Update the type in the type source information too.
  if (TypeSourceInfo *TSInfo = FD->getTypeSourceInfo()) {
    // If the type and the type-as-written differ, we may need to update
    // the type-as-written too.
    if (TSInfo->getType() != FD->getType())
      Updated = getFunctionTypeWithExceptionSpec(TSInfo->getType(), ESI);

    // FIXME: When we get proper type location information for exceptions,
    // we'll also have to rebuild the TypeSourceInfo. For now, we just patch
    // up the TypeSourceInfo;
    assert(TypeLoc::getFullDataSizeForType(Updated) ==
               TypeLoc::getFullDataSizeForType(TSInfo->getType()) &&
           "TypeLoc size mismatch from updating exception specification");
    TSInfo->overrideType(Updated);
  }
}

/// getComplexType - Return the uniqued reference to the type for a complex
/// number with the specified element type.
QualType ASTContext::getComplexType(QualType T) const {
  // Unique pointers, to guarantee there is only one pointer of a particular
  // structure.
  llvm::FoldingSetNodeID ID;
  ComplexType::Profile(ID, T);

  void *InsertPos = nullptr;
  if (ComplexType *CT = ComplexTypes.FindNodeOrInsertPos(ID, InsertPos))
    return QualType(CT, 0);

  // If the pointee type isn't canonical, this won't be a canonical type either,
  // so fill in the canonical type field.
  QualType Canonical;
  if (!T.isCanonical()) {
    Canonical = getComplexType(getCanonicalType(T));

    // Get the new insert position for the node we care about.
    ComplexType *NewIP = ComplexTypes.FindNodeOrInsertPos(ID, InsertPos);
    assert(!NewIP && "Shouldn't be in the map!"); (void)NewIP;
  }
  auto *New = new (*this, TypeAlignment) ComplexType(T, Canonical);
  Types.push_back(New);
  ComplexTypes.InsertNode(New, InsertPos);
  return QualType(New, 0);
}

/// getPointerType - Return the uniqued reference to the type for a pointer to
/// the specified type.
QualType ASTContext::getPointerType(QualType T) const {
  // Unique pointers, to guarantee there is only one pointer of a particular
  // structure.
  llvm::FoldingSetNodeID ID;
  PointerType::Profile(ID, T);

  void *InsertPos = nullptr;
  if (PointerType *PT = PointerTypes.FindNodeOrInsertPos(ID, InsertPos))
    return QualType(PT, 0);

  // If the pointee type isn't canonical, this won't be a canonical type either,
  // so fill in the canonical type field.
  QualType Canonical;
  if (!T.isCanonical()) {
    Canonical = getPointerType(getCanonicalType(T));

    // Get the new insert position for the node we care about.
    PointerType *NewIP = PointerTypes.FindNodeOrInsertPos(ID, InsertPos);
    assert(!NewIP && "Shouldn't be in the map!"); (void)NewIP;
  }
  auto *New = new (*this, TypeAlignment) PointerType(T, Canonical);
  Types.push_back(New);
  PointerTypes.InsertNode(New, InsertPos);
  return QualType(New, 0);
}

QualType ASTContext::getAdjustedType(QualType Orig, QualType New) const {
  llvm::FoldingSetNodeID ID;
  AdjustedType::Profile(ID, Orig, New);
  void *InsertPos = nullptr;
  AdjustedType *AT = AdjustedTypes.FindNodeOrInsertPos(ID, InsertPos);
  if (AT)
    return QualType(AT, 0);

  QualType Canonical = getCanonicalType(New);

  // Get the new insert position for the node we care about.
  AT = AdjustedTypes.FindNodeOrInsertPos(ID, InsertPos);
  assert(!AT && "Shouldn't be in the map!");

  AT = new (*this, TypeAlignment)
      AdjustedType(Type::Adjusted, Orig, New, Canonical);
  Types.push_back(AT);
  AdjustedTypes.InsertNode(AT, InsertPos);
  return QualType(AT, 0);
}

QualType ASTContext::getDecayedType(QualType T) const {
  assert((T->isArrayType() || T->isFunctionType()) && "T does not decay");

  QualType Decayed;

  // C99 6.7.5.3p7:
  //   A declaration of a parameter as "array of type" shall be
  //   adjusted to "qualified pointer to type", where the type
  //   qualifiers (if any) are those specified within the [ and ] of
  //   the array type derivation.
  if (T->isArrayType())
    Decayed = getArrayDecayedType(T);

  // C99 6.7.5.3p8:
  //   A declaration of a parameter as "function returning type"
  //   shall be adjusted to "pointer to function returning type", as
  //   in 6.3.2.1.
  if (T->isFunctionType())
    Decayed = getPointerType(T);

  llvm::FoldingSetNodeID ID;
  AdjustedType::Profile(ID, T, Decayed);
  void *InsertPos = nullptr;
  AdjustedType *AT = AdjustedTypes.FindNodeOrInsertPos(ID, InsertPos);
  if (AT)
    return QualType(AT, 0);

  QualType Canonical = getCanonicalType(Decayed);

  // Get the new insert position for the node we care about.
  AT = AdjustedTypes.FindNodeOrInsertPos(ID, InsertPos);
  assert(!AT && "Shouldn't be in the map!");

  AT = new (*this, TypeAlignment) DecayedType(T, Decayed, Canonical);
  Types.push_back(AT);
  AdjustedTypes.InsertNode(AT, InsertPos);
  return QualType(AT, 0);
}

/// getBlockPointerType - Return the uniqued reference to the type for
/// a pointer to the specified block.
QualType ASTContext::getBlockPointerType(QualType T) const {
  assert(T->isFunctionType() && "block of function types only");
  // Unique pointers, to guarantee there is only one block of a particular
  // structure.
  llvm::FoldingSetNodeID ID;
  BlockPointerType::Profile(ID, T);

  void *InsertPos = nullptr;
  if (BlockPointerType *PT =
        BlockPointerTypes.FindNodeOrInsertPos(ID, InsertPos))
    return QualType(PT, 0);

  // If the block pointee type isn't canonical, this won't be a canonical
  // type either so fill in the canonical type field.
  QualType Canonical;
  if (!T.isCanonical()) {
    Canonical = getBlockPointerType(getCanonicalType(T));

    // Get the new insert position for the node we care about.
    BlockPointerType *NewIP =
      BlockPointerTypes.FindNodeOrInsertPos(ID, InsertPos);
    assert(!NewIP && "Shouldn't be in the map!"); (void)NewIP;
  }
  auto *New = new (*this, TypeAlignment) BlockPointerType(T, Canonical);
  Types.push_back(New);
  BlockPointerTypes.InsertNode(New, InsertPos);
  return QualType(New, 0);
}

/// getLValueReferenceType - Return the uniqued reference to the type for an
/// lvalue reference to the specified type.
QualType
ASTContext::getLValueReferenceType(QualType T, bool SpelledAsLValue) const {
  assert(getCanonicalType(T) != OverloadTy &&
         "Unresolved overloaded function type");

  // Unique pointers, to guarantee there is only one pointer of a particular
  // structure.
  llvm::FoldingSetNodeID ID;
  ReferenceType::Profile(ID, T, SpelledAsLValue);

  void *InsertPos = nullptr;
  if (LValueReferenceType *RT =
        LValueReferenceTypes.FindNodeOrInsertPos(ID, InsertPos))
    return QualType(RT, 0);

  const auto *InnerRef = T->getAs<ReferenceType>();

  // If the referencee type isn't canonical, this won't be a canonical type
  // either, so fill in the canonical type field.
  QualType Canonical;
  if (!SpelledAsLValue || InnerRef || !T.isCanonical()) {
    QualType PointeeType = (InnerRef ? InnerRef->getPointeeType() : T);
    Canonical = getLValueReferenceType(getCanonicalType(PointeeType));

    // Get the new insert position for the node we care about.
    LValueReferenceType *NewIP =
      LValueReferenceTypes.FindNodeOrInsertPos(ID, InsertPos);
    assert(!NewIP && "Shouldn't be in the map!"); (void)NewIP;
  }

  auto *New = new (*this, TypeAlignment) LValueReferenceType(T, Canonical,
                                                             SpelledAsLValue);
  Types.push_back(New);
  LValueReferenceTypes.InsertNode(New, InsertPos);

  return QualType(New, 0);
}

/// getRValueReferenceType - Return the uniqued reference to the type for an
/// rvalue reference to the specified type.
QualType ASTContext::getRValueReferenceType(QualType T) const {
  // Unique pointers, to guarantee there is only one pointer of a particular
  // structure.
  llvm::FoldingSetNodeID ID;
  ReferenceType::Profile(ID, T, false);

  void *InsertPos = nullptr;
  if (RValueReferenceType *RT =
        RValueReferenceTypes.FindNodeOrInsertPos(ID, InsertPos))
    return QualType(RT, 0);

  const auto *InnerRef = T->getAs<ReferenceType>();

  // If the referencee type isn't canonical, this won't be a canonical type
  // either, so fill in the canonical type field.
  QualType Canonical;
  if (InnerRef || !T.isCanonical()) {
    QualType PointeeType = (InnerRef ? InnerRef->getPointeeType() : T);
    Canonical = getRValueReferenceType(getCanonicalType(PointeeType));

    // Get the new insert position for the node we care about.
    RValueReferenceType *NewIP =
      RValueReferenceTypes.FindNodeOrInsertPos(ID, InsertPos);
    assert(!NewIP && "Shouldn't be in the map!"); (void)NewIP;
  }

  auto *New = new (*this, TypeAlignment) RValueReferenceType(T, Canonical);
  Types.push_back(New);
  RValueReferenceTypes.InsertNode(New, InsertPos);
  return QualType(New, 0);
}

/// getMemberPointerType - Return the uniqued reference to the type for a
/// member pointer to the specified type, in the specified class.
QualType ASTContext::getMemberPointerType(QualType T, const Type *Cls) const {
  // Unique pointers, to guarantee there is only one pointer of a particular
  // structure.
  llvm::FoldingSetNodeID ID;
  MemberPointerType::Profile(ID, T, Cls);

  void *InsertPos = nullptr;
  if (MemberPointerType *PT =
      MemberPointerTypes.FindNodeOrInsertPos(ID, InsertPos))
    return QualType(PT, 0);

  // If the pointee or class type isn't canonical, this won't be a canonical
  // type either, so fill in the canonical type field.
  QualType Canonical;
  if (!T.isCanonical() || !Cls->isCanonicalUnqualified()) {
    Canonical = getMemberPointerType(getCanonicalType(T),getCanonicalType(Cls));

    // Get the new insert position for the node we care about.
    MemberPointerType *NewIP =
      MemberPointerTypes.FindNodeOrInsertPos(ID, InsertPos);
    assert(!NewIP && "Shouldn't be in the map!"); (void)NewIP;
  }
  auto *New = new (*this, TypeAlignment) MemberPointerType(T, Cls, Canonical);
  Types.push_back(New);
  MemberPointerTypes.InsertNode(New, InsertPos);
  return QualType(New, 0);
}

/// getConstantArrayType - Return the unique reference to the type for an
/// array of the specified element type.
QualType ASTContext::getConstantArrayType(QualType EltTy,
                                          const llvm::APInt &ArySizeIn,
                                          const Expr *SizeExpr,
                                          ArrayType::ArraySizeModifier ASM,
                                          unsigned IndexTypeQuals) const {
  assert((EltTy->isDependentType() ||
          EltTy->isIncompleteType() || EltTy->isConstantSizeType()) &&
         "Constant array of VLAs is illegal!");

  // We only need the size as part of the type if it's instantiation-dependent.
  if (SizeExpr && !SizeExpr->isInstantiationDependent())
    SizeExpr = nullptr;

  // Convert the array size into a canonical width matching the pointer size for
  // the target.
  llvm::APInt ArySize(ArySizeIn);
  ArySize = ArySize.zextOrTrunc(Target->getMaxPointerWidth());

  llvm::FoldingSetNodeID ID;
  ConstantArrayType::Profile(ID, *this, EltTy, ArySize, SizeExpr, ASM,
                             IndexTypeQuals);

  void *InsertPos = nullptr;
  if (ConstantArrayType *ATP =
      ConstantArrayTypes.FindNodeOrInsertPos(ID, InsertPos))
    return QualType(ATP, 0);

  // If the element type isn't canonical or has qualifiers, or the array bound
  // is instantiation-dependent, this won't be a canonical type either, so fill
  // in the canonical type field.
  QualType Canon;
  if (!EltTy.isCanonical() || EltTy.hasLocalQualifiers() || SizeExpr) {
    SplitQualType canonSplit = getCanonicalType(EltTy).split();
    Canon = getConstantArrayType(QualType(canonSplit.Ty, 0), ArySize, nullptr,
                                 ASM, IndexTypeQuals);
    Canon = getQualifiedType(Canon, canonSplit.Quals);

    // Get the new insert position for the node we care about.
    ConstantArrayType *NewIP =
      ConstantArrayTypes.FindNodeOrInsertPos(ID, InsertPos);
    assert(!NewIP && "Shouldn't be in the map!"); (void)NewIP;
  }

  void *Mem = Allocate(
      ConstantArrayType::totalSizeToAlloc<const Expr *>(SizeExpr ? 1 : 0),
      TypeAlignment);
  auto *New = new (Mem)
    ConstantArrayType(EltTy, Canon, ArySize, SizeExpr, ASM, IndexTypeQuals);
  ConstantArrayTypes.InsertNode(New, InsertPos);
  Types.push_back(New);
  return QualType(New, 0);
}

/// getVariableArrayDecayedType - Turns the given type, which may be
/// variably-modified, into the corresponding type with all the known
/// sizes replaced with [*].
QualType ASTContext::getVariableArrayDecayedType(QualType type) const {
  // Vastly most common case.
  if (!type->isVariablyModifiedType()) return type;

  QualType result;

  SplitQualType split = type.getSplitDesugaredType();
  const Type *ty = split.Ty;
  switch (ty->getTypeClass()) {
#define TYPE(Class, Base)
#define ABSTRACT_TYPE(Class, Base)
#define NON_CANONICAL_TYPE(Class, Base) case Type::Class:
#include "clang/AST/TypeNodes.inc"
    llvm_unreachable("didn't desugar past all non-canonical types?");

  // These types should never be variably-modified.
  case Type::Builtin:
  case Type::Complex:
  case Type::Vector:
  case Type::DependentVector:
  case Type::ExtVector:
  case Type::DependentSizedExtVector:
  case Type::DependentAddressSpace:
  case Type::ObjCObject:
  case Type::ObjCInterface:
  case Type::ObjCObjectPointer:
  case Type::Record:
  case Type::Enum:
  case Type::UnresolvedUsing:
  case Type::TypeOfExpr:
  case Type::TypeOf:
  case Type::Decltype:
  case Type::UnaryTransform:
  case Type::DependentName:
  case Type::InjectedClassName:
  case Type::TemplateSpecialization:
  case Type::DependentTemplateSpecialization:
  case Type::TemplateTypeParm:
  case Type::SubstTemplateTypeParmPack:
  case Type::Auto:
  case Type::DeducedTemplateSpecialization:
  case Type::PackExpansion:
    llvm_unreachable("type should never be variably-modified");

  // These types can be variably-modified but should never need to
  // further decay.
  case Type::FunctionNoProto:
  case Type::FunctionProto:
  case Type::BlockPointer:
  case Type::MemberPointer:
  case Type::Pipe:
    return type;

  // These types can be variably-modified.  All these modifications
  // preserve structure except as noted by comments.
  // TODO: if we ever care about optimizing VLAs, there are no-op
  // optimizations available here.
  case Type::Pointer:
    result = getPointerType(getVariableArrayDecayedType(
                              cast<PointerType>(ty)->getPointeeType()));
    break;

  case Type::LValueReference: {
    const auto *lv = cast<LValueReferenceType>(ty);
    result = getLValueReferenceType(
                 getVariableArrayDecayedType(lv->getPointeeType()),
                                    lv->isSpelledAsLValue());
    break;
  }

  case Type::RValueReference: {
    const auto *lv = cast<RValueReferenceType>(ty);
    result = getRValueReferenceType(
                 getVariableArrayDecayedType(lv->getPointeeType()));
    break;
  }

  case Type::Atomic: {
    const auto *at = cast<AtomicType>(ty);
    result = getAtomicType(getVariableArrayDecayedType(at->getValueType()));
    break;
  }

  case Type::ConstantArray: {
    const auto *cat = cast<ConstantArrayType>(ty);
    result = getConstantArrayType(
                 getVariableArrayDecayedType(cat->getElementType()),
                                  cat->getSize(),
                                  cat->getSizeExpr(),
                                  cat->getSizeModifier(),
                                  cat->getIndexTypeCVRQualifiers());
    break;
  }

  case Type::DependentSizedArray: {
    const auto *dat = cast<DependentSizedArrayType>(ty);
    result = getDependentSizedArrayType(
                 getVariableArrayDecayedType(dat->getElementType()),
                                        dat->getSizeExpr(),
                                        dat->getSizeModifier(),
                                        dat->getIndexTypeCVRQualifiers(),
                                        dat->getBracketsRange());
    break;
  }

  // Turn incomplete types into [*] types.
  case Type::IncompleteArray: {
    const auto *iat = cast<IncompleteArrayType>(ty);
    result = getVariableArrayType(
                 getVariableArrayDecayedType(iat->getElementType()),
                                  /*size*/ nullptr,
                                  ArrayType::Normal,
                                  iat->getIndexTypeCVRQualifiers(),
                                  SourceRange());
    break;
  }

  // Turn VLA types into [*] types.
  case Type::VariableArray: {
    const auto *vat = cast<VariableArrayType>(ty);
    result = getVariableArrayType(
                 getVariableArrayDecayedType(vat->getElementType()),
                                  /*size*/ nullptr,
                                  ArrayType::Star,
                                  vat->getIndexTypeCVRQualifiers(),
                                  vat->getBracketsRange());
    break;
  }
  }

  // Apply the top-level qualifiers from the original.
  return getQualifiedType(result, split.Quals);
}

/// getVariableArrayType - Returns a non-unique reference to the type for a
/// variable array of the specified element type.
QualType ASTContext::getVariableArrayType(QualType EltTy,
                                          Expr *NumElts,
                                          ArrayType::ArraySizeModifier ASM,
                                          unsigned IndexTypeQuals,
                                          SourceRange Brackets) const {
  // Since we don't unique expressions, it isn't possible to unique VLA's
  // that have an expression provided for their size.
  QualType Canon;

  // Be sure to pull qualifiers off the element type.
  if (!EltTy.isCanonical() || EltTy.hasLocalQualifiers()) {
    SplitQualType canonSplit = getCanonicalType(EltTy).split();
    Canon = getVariableArrayType(QualType(canonSplit.Ty, 0), NumElts, ASM,
                                 IndexTypeQuals, Brackets);
    Canon = getQualifiedType(Canon, canonSplit.Quals);
  }

  auto *New = new (*this, TypeAlignment)
    VariableArrayType(EltTy, Canon, NumElts, ASM, IndexTypeQuals, Brackets);

  VariableArrayTypes.push_back(New);
  Types.push_back(New);
  return QualType(New, 0);
}

/// getDependentSizedArrayType - Returns a non-unique reference to
/// the type for a dependently-sized array of the specified element
/// type.
QualType ASTContext::getDependentSizedArrayType(QualType elementType,
                                                Expr *numElements,
                                                ArrayType::ArraySizeModifier ASM,
                                                unsigned elementTypeQuals,
                                                SourceRange brackets) const {
  assert((!numElements || numElements->isTypeDependent() ||
          numElements->isValueDependent()) &&
         "Size must be type- or value-dependent!");

  // Dependently-sized array types that do not have a specified number
  // of elements will have their sizes deduced from a dependent
  // initializer.  We do no canonicalization here at all, which is okay
  // because they can't be used in most locations.
  if (!numElements) {
    auto *newType
      = new (*this, TypeAlignment)
          DependentSizedArrayType(*this, elementType, QualType(),
                                  numElements, ASM, elementTypeQuals,
                                  brackets);
    Types.push_back(newType);
    return QualType(newType, 0);
  }

  // Otherwise, we actually build a new type every time, but we
  // also build a canonical type.

  SplitQualType canonElementType = getCanonicalType(elementType).split();

  void *insertPos = nullptr;
  llvm::FoldingSetNodeID ID;
  DependentSizedArrayType::Profile(ID, *this,
                                   QualType(canonElementType.Ty, 0),
                                   ASM, elementTypeQuals, numElements);

  // Look for an existing type with these properties.
  DependentSizedArrayType *canonTy =
    DependentSizedArrayTypes.FindNodeOrInsertPos(ID, insertPos);

  // If we don't have one, build one.
  if (!canonTy) {
    canonTy = new (*this, TypeAlignment)
      DependentSizedArrayType(*this, QualType(canonElementType.Ty, 0),
                              QualType(), numElements, ASM, elementTypeQuals,
                              brackets);
    DependentSizedArrayTypes.InsertNode(canonTy, insertPos);
    Types.push_back(canonTy);
  }

  // Apply qualifiers from the element type to the array.
  QualType canon = getQualifiedType(QualType(canonTy,0),
                                    canonElementType.Quals);

  // If we didn't need extra canonicalization for the element type or the size
  // expression, then just use that as our result.
  if (QualType(canonElementType.Ty, 0) == elementType &&
      canonTy->getSizeExpr() == numElements)
    return canon;

  // Otherwise, we need to build a type which follows the spelling
  // of the element type.
  auto *sugaredType
    = new (*this, TypeAlignment)
        DependentSizedArrayType(*this, elementType, canon, numElements,
                                ASM, elementTypeQuals, brackets);
  Types.push_back(sugaredType);
  return QualType(sugaredType, 0);
}

QualType ASTContext::getIncompleteArrayType(QualType elementType,
                                            ArrayType::ArraySizeModifier ASM,
                                            unsigned elementTypeQuals) const {
  llvm::FoldingSetNodeID ID;
  IncompleteArrayType::Profile(ID, elementType, ASM, elementTypeQuals);

  void *insertPos = nullptr;
  if (IncompleteArrayType *iat =
       IncompleteArrayTypes.FindNodeOrInsertPos(ID, insertPos))
    return QualType(iat, 0);

  // If the element type isn't canonical, this won't be a canonical type
  // either, so fill in the canonical type field.  We also have to pull
  // qualifiers off the element type.
  QualType canon;

  if (!elementType.isCanonical() || elementType.hasLocalQualifiers()) {
    SplitQualType canonSplit = getCanonicalType(elementType).split();
    canon = getIncompleteArrayType(QualType(canonSplit.Ty, 0),
                                   ASM, elementTypeQuals);
    canon = getQualifiedType(canon, canonSplit.Quals);

    // Get the new insert position for the node we care about.
    IncompleteArrayType *existing =
      IncompleteArrayTypes.FindNodeOrInsertPos(ID, insertPos);
    assert(!existing && "Shouldn't be in the map!"); (void) existing;
  }

  auto *newType = new (*this, TypeAlignment)
    IncompleteArrayType(elementType, canon, ASM, elementTypeQuals);

  IncompleteArrayTypes.InsertNode(newType, insertPos);
  Types.push_back(newType);
  return QualType(newType, 0);
}

/// getVectorType - Return the unique reference to a vector type of
/// the specified element type and size. VectorType must be a built-in type.
QualType ASTContext::getVectorType(QualType vecType, unsigned NumElts,
                                   VectorType::VectorKind VecKind) const {
  assert(vecType->isBuiltinType());

  // Check if we've already instantiated a vector of this type.
  llvm::FoldingSetNodeID ID;
  VectorType::Profile(ID, vecType, NumElts, Type::Vector, VecKind);

  void *InsertPos = nullptr;
  if (VectorType *VTP = VectorTypes.FindNodeOrInsertPos(ID, InsertPos))
    return QualType(VTP, 0);

  // If the element type isn't canonical, this won't be a canonical type either,
  // so fill in the canonical type field.
  QualType Canonical;
  if (!vecType.isCanonical()) {
    Canonical = getVectorType(getCanonicalType(vecType), NumElts, VecKind);

    // Get the new insert position for the node we care about.
    VectorType *NewIP = VectorTypes.FindNodeOrInsertPos(ID, InsertPos);
    assert(!NewIP && "Shouldn't be in the map!"); (void)NewIP;
  }
  auto *New = new (*this, TypeAlignment)
    VectorType(vecType, NumElts, Canonical, VecKind);
  VectorTypes.InsertNode(New, InsertPos);
  Types.push_back(New);
  return QualType(New, 0);
}

QualType
ASTContext::getDependentVectorType(QualType VecType, Expr *SizeExpr,
                                   SourceLocation AttrLoc,
                                   VectorType::VectorKind VecKind) const {
  llvm::FoldingSetNodeID ID;
  DependentVectorType::Profile(ID, *this, getCanonicalType(VecType), SizeExpr,
                               VecKind);
  void *InsertPos = nullptr;
  DependentVectorType *Canon =
      DependentVectorTypes.FindNodeOrInsertPos(ID, InsertPos);
  DependentVectorType *New;

  if (Canon) {
    New = new (*this, TypeAlignment) DependentVectorType(
        *this, VecType, QualType(Canon, 0), SizeExpr, AttrLoc, VecKind);
  } else {
    QualType CanonVecTy = getCanonicalType(VecType);
    if (CanonVecTy == VecType) {
      New = new (*this, TypeAlignment) DependentVectorType(
          *this, VecType, QualType(), SizeExpr, AttrLoc, VecKind);

      DependentVectorType *CanonCheck =
          DependentVectorTypes.FindNodeOrInsertPos(ID, InsertPos);
      assert(!CanonCheck &&
             "Dependent-sized vector_size canonical type broken");
      (void)CanonCheck;
      DependentVectorTypes.InsertNode(New, InsertPos);
    } else {
      QualType Canon = getDependentSizedExtVectorType(CanonVecTy, SizeExpr,
                                                      SourceLocation());
      New = new (*this, TypeAlignment) DependentVectorType(
          *this, VecType, Canon, SizeExpr, AttrLoc, VecKind);
    }
  }

  Types.push_back(New);
  return QualType(New, 0);
}

/// getExtVectorType - Return the unique reference to an extended vector type of
/// the specified element type and size. VectorType must be a built-in type.
QualType
ASTContext::getExtVectorType(QualType vecType, unsigned NumElts) const {
  assert(vecType->isBuiltinType() || vecType->isDependentType());

  // Check if we've already instantiated a vector of this type.
  llvm::FoldingSetNodeID ID;
  VectorType::Profile(ID, vecType, NumElts, Type::ExtVector,
                      VectorType::GenericVector);
  void *InsertPos = nullptr;
  if (VectorType *VTP = VectorTypes.FindNodeOrInsertPos(ID, InsertPos))
    return QualType(VTP, 0);

  // If the element type isn't canonical, this won't be a canonical type either,
  // so fill in the canonical type field.
  QualType Canonical;
  if (!vecType.isCanonical()) {
    Canonical = getExtVectorType(getCanonicalType(vecType), NumElts);

    // Get the new insert position for the node we care about.
    VectorType *NewIP = VectorTypes.FindNodeOrInsertPos(ID, InsertPos);
    assert(!NewIP && "Shouldn't be in the map!"); (void)NewIP;
  }
  auto *New = new (*this, TypeAlignment)
    ExtVectorType(vecType, NumElts, Canonical);
  VectorTypes.InsertNode(New, InsertPos);
  Types.push_back(New);
  return QualType(New, 0);
}

QualType
ASTContext::getDependentSizedExtVectorType(QualType vecType,
                                           Expr *SizeExpr,
                                           SourceLocation AttrLoc) const {
  llvm::FoldingSetNodeID ID;
  DependentSizedExtVectorType::Profile(ID, *this, getCanonicalType(vecType),
                                       SizeExpr);

  void *InsertPos = nullptr;
  DependentSizedExtVectorType *Canon
    = DependentSizedExtVectorTypes.FindNodeOrInsertPos(ID, InsertPos);
  DependentSizedExtVectorType *New;
  if (Canon) {
    // We already have a canonical version of this array type; use it as
    // the canonical type for a newly-built type.
    New = new (*this, TypeAlignment)
      DependentSizedExtVectorType(*this, vecType, QualType(Canon, 0),
                                  SizeExpr, AttrLoc);
  } else {
    QualType CanonVecTy = getCanonicalType(vecType);
    if (CanonVecTy == vecType) {
      New = new (*this, TypeAlignment)
        DependentSizedExtVectorType(*this, vecType, QualType(), SizeExpr,
                                    AttrLoc);

      DependentSizedExtVectorType *CanonCheck
        = DependentSizedExtVectorTypes.FindNodeOrInsertPos(ID, InsertPos);
      assert(!CanonCheck && "Dependent-sized ext_vector canonical type broken");
      (void)CanonCheck;
      DependentSizedExtVectorTypes.InsertNode(New, InsertPos);
    } else {
      QualType Canon = getDependentSizedExtVectorType(CanonVecTy, SizeExpr,
                                                      SourceLocation());
      New = new (*this, TypeAlignment)
        DependentSizedExtVectorType(*this, vecType, Canon, SizeExpr, AttrLoc);
    }
  }

  Types.push_back(New);
  return QualType(New, 0);
}

QualType ASTContext::getDependentAddressSpaceType(QualType PointeeType,
                                                  Expr *AddrSpaceExpr,
                                                  SourceLocation AttrLoc) const {
  assert(AddrSpaceExpr->isInstantiationDependent());

  QualType canonPointeeType = getCanonicalType(PointeeType);

  void *insertPos = nullptr;
  llvm::FoldingSetNodeID ID;
  DependentAddressSpaceType::Profile(ID, *this, canonPointeeType,
                                     AddrSpaceExpr);

  DependentAddressSpaceType *canonTy =
    DependentAddressSpaceTypes.FindNodeOrInsertPos(ID, insertPos);

  if (!canonTy) {
    canonTy = new (*this, TypeAlignment)
      DependentAddressSpaceType(*this, canonPointeeType,
                                QualType(), AddrSpaceExpr, AttrLoc);
    DependentAddressSpaceTypes.InsertNode(canonTy, insertPos);
    Types.push_back(canonTy);
  }

  if (canonPointeeType == PointeeType &&
      canonTy->getAddrSpaceExpr() == AddrSpaceExpr)
    return QualType(canonTy, 0);

  auto *sugaredType
    = new (*this, TypeAlignment)
        DependentAddressSpaceType(*this, PointeeType, QualType(canonTy, 0),
                                  AddrSpaceExpr, AttrLoc);
  Types.push_back(sugaredType);
  return QualType(sugaredType, 0);
}

/// Determine whether \p T is canonical as the result type of a function.
static bool isCanonicalResultType(QualType T) {
  return T.isCanonical() &&
         (T.getObjCLifetime() == Qualifiers::OCL_None ||
          T.getObjCLifetime() == Qualifiers::OCL_ExplicitNone);
}

/// getFunctionNoProtoType - Return a K&R style C function type like 'int()'.
QualType
ASTContext::getFunctionNoProtoType(QualType ResultTy,
                                   const FunctionType::ExtInfo &Info) const {
  // Unique functions, to guarantee there is only one function of a particular
  // structure.
  llvm::FoldingSetNodeID ID;
  FunctionNoProtoType::Profile(ID, ResultTy, Info);

  void *InsertPos = nullptr;
  if (FunctionNoProtoType *FT =
        FunctionNoProtoTypes.FindNodeOrInsertPos(ID, InsertPos))
    return QualType(FT, 0);

  QualType Canonical;
  if (!isCanonicalResultType(ResultTy)) {
    Canonical =
      getFunctionNoProtoType(getCanonicalFunctionResultType(ResultTy), Info);

    // Get the new insert position for the node we care about.
    FunctionNoProtoType *NewIP =
      FunctionNoProtoTypes.FindNodeOrInsertPos(ID, InsertPos);
    assert(!NewIP && "Shouldn't be in the map!"); (void)NewIP;
  }

  auto *New = new (*this, TypeAlignment)
    FunctionNoProtoType(ResultTy, Canonical, Info);
  Types.push_back(New);
  FunctionNoProtoTypes.InsertNode(New, InsertPos);
  return QualType(New, 0);
}

CanQualType
ASTContext::getCanonicalFunctionResultType(QualType ResultType) const {
  CanQualType CanResultType = getCanonicalType(ResultType);

  // Canonical result types do not have ARC lifetime qualifiers.
  if (CanResultType.getQualifiers().hasObjCLifetime()) {
    Qualifiers Qs = CanResultType.getQualifiers();
    Qs.removeObjCLifetime();
    return CanQualType::CreateUnsafe(
             getQualifiedType(CanResultType.getUnqualifiedType(), Qs));
  }

  return CanResultType;
}

static bool isCanonicalExceptionSpecification(
    const FunctionProtoType::ExceptionSpecInfo &ESI, bool NoexceptInType) {
  if (ESI.Type == EST_None)
    return true;
  if (!NoexceptInType)
    return false;

  // C++17 onwards: exception specification is part of the type, as a simple
  // boolean "can this function type throw".
  if (ESI.Type == EST_BasicNoexcept)
    return true;

  // A noexcept(expr) specification is (possibly) canonical if expr is
  // value-dependent.
  if (ESI.Type == EST_DependentNoexcept)
    return true;

  // A dynamic exception specification is canonical if it only contains pack
  // expansions (so we can't tell whether it's non-throwing) and all its
  // contained types are canonical.
  if (ESI.Type == EST_Dynamic) {
    bool AnyPackExpansions = false;
    for (QualType ET : ESI.Exceptions) {
      if (!ET.isCanonical())
        return false;
      if (ET->getAs<PackExpansionType>())
        AnyPackExpansions = true;
    }
    return AnyPackExpansions;
  }

  return false;
}

QualType ASTContext::getFunctionTypeInternal(
    QualType ResultTy, ArrayRef<QualType> ArgArray,
    const FunctionProtoType::ExtProtoInfo &EPI, bool OnlyWantCanonical) const {
  size_t NumArgs = ArgArray.size();

  // Unique functions, to guarantee there is only one function of a particular
  // structure.
  llvm::FoldingSetNodeID ID;
  FunctionProtoType::Profile(ID, ResultTy, ArgArray.begin(), NumArgs, EPI,
                             *this, true);

  QualType Canonical;
  bool Unique = false;

  void *InsertPos = nullptr;
  if (FunctionProtoType *FPT =
        FunctionProtoTypes.FindNodeOrInsertPos(ID, InsertPos)) {
    QualType Existing = QualType(FPT, 0);

    // If we find a pre-existing equivalent FunctionProtoType, we can just reuse
    // it so long as our exception specification doesn't contain a dependent
    // noexcept expression, or we're just looking for a canonical type.
    // Otherwise, we're going to need to create a type
    // sugar node to hold the concrete expression.
    if (OnlyWantCanonical || !isComputedNoexcept(EPI.ExceptionSpec.Type) ||
        EPI.ExceptionSpec.NoexceptExpr == FPT->getNoexceptExpr())
      return Existing;

    // We need a new type sugar node for this one, to hold the new noexcept
    // expression. We do no canonicalization here, but that's OK since we don't
    // expect to see the same noexcept expression much more than once.
    Canonical = getCanonicalType(Existing);
    Unique = true;
  }

  bool NoexceptInType = getLangOpts().CPlusPlus17;
  bool IsCanonicalExceptionSpec =
      isCanonicalExceptionSpecification(EPI.ExceptionSpec, NoexceptInType);

  // Determine whether the type being created is already canonical or not.
  bool isCanonical = !Unique && IsCanonicalExceptionSpec &&
                     isCanonicalResultType(ResultTy) && !EPI.HasTrailingReturn;
  for (unsigned i = 0; i != NumArgs && isCanonical; ++i)
    if (!ArgArray[i].isCanonicalAsParam())
      isCanonical = false;

  if (OnlyWantCanonical)
    assert(isCanonical &&
           "given non-canonical parameters constructing canonical type");

  // If this type isn't canonical, get the canonical version of it if we don't
  // already have it. The exception spec is only partially part of the
  // canonical type, and only in C++17 onwards.
  if (!isCanonical && Canonical.isNull()) {
    SmallVector<QualType, 16> CanonicalArgs;
    CanonicalArgs.reserve(NumArgs);
    for (unsigned i = 0; i != NumArgs; ++i)
      CanonicalArgs.push_back(getCanonicalParamType(ArgArray[i]));

    llvm::SmallVector<QualType, 8> ExceptionTypeStorage;
    FunctionProtoType::ExtProtoInfo CanonicalEPI = EPI;
    CanonicalEPI.HasTrailingReturn = false;

    if (IsCanonicalExceptionSpec) {
      // Exception spec is already OK.
    } else if (NoexceptInType) {
      switch (EPI.ExceptionSpec.Type) {
      case EST_Unparsed: case EST_Unevaluated: case EST_Uninstantiated:
        // We don't know yet. It shouldn't matter what we pick here; no-one
        // should ever look at this.
        LLVM_FALLTHROUGH;
      case EST_None: case EST_MSAny: case EST_NoexceptFalse:
        CanonicalEPI.ExceptionSpec.Type = EST_None;
        break;

        // A dynamic exception specification is almost always "not noexcept",
        // with the exception that a pack expansion might expand to no types.
      case EST_Dynamic: {
        bool AnyPacks = false;
        for (QualType ET : EPI.ExceptionSpec.Exceptions) {
          if (ET->getAs<PackExpansionType>())
            AnyPacks = true;
          ExceptionTypeStorage.push_back(getCanonicalType(ET));
        }
        if (!AnyPacks)
          CanonicalEPI.ExceptionSpec.Type = EST_None;
        else {
          CanonicalEPI.ExceptionSpec.Type = EST_Dynamic;
          CanonicalEPI.ExceptionSpec.Exceptions = ExceptionTypeStorage;
        }
        break;
      }

      case EST_DynamicNone:
      case EST_BasicNoexcept:
      case EST_NoexceptTrue:
      case EST_NoThrow:
        CanonicalEPI.ExceptionSpec.Type = EST_BasicNoexcept;
        break;

      case EST_DependentNoexcept:
        llvm_unreachable("dependent noexcept is already canonical");
      }
    } else {
      CanonicalEPI.ExceptionSpec = FunctionProtoType::ExceptionSpecInfo();
    }

    // Adjust the canonical function result type.
    CanQualType CanResultTy = getCanonicalFunctionResultType(ResultTy);
    Canonical =
        getFunctionTypeInternal(CanResultTy, CanonicalArgs, CanonicalEPI, true);

    // Get the new insert position for the node we care about.
    FunctionProtoType *NewIP =
      FunctionProtoTypes.FindNodeOrInsertPos(ID, InsertPos);
    assert(!NewIP && "Shouldn't be in the map!"); (void)NewIP;
  }

  // Compute the needed size to hold this FunctionProtoType and the
  // various trailing objects.
  auto ESH = FunctionProtoType::getExceptionSpecSize(
      EPI.ExceptionSpec.Type, EPI.ExceptionSpec.Exceptions.size());
  size_t Size = FunctionProtoType::totalSizeToAlloc<
      QualType, FunctionType::FunctionTypeExtraBitfields,
      FunctionType::ExceptionType, Expr *, FunctionDecl *,
      FunctionProtoType::ExtParameterInfo, Qualifiers>(
      NumArgs, FunctionProtoType::hasExtraBitfields(EPI.ExceptionSpec.Type),
      ESH.NumExceptionType, ESH.NumExprPtr, ESH.NumFunctionDeclPtr,
      EPI.ExtParameterInfos ? NumArgs : 0,
      EPI.TypeQuals.hasNonFastQualifiers() ? 1 : 0);

  auto *FTP = (FunctionProtoType *)Allocate(Size, TypeAlignment);
  FunctionProtoType::ExtProtoInfo newEPI = EPI;
  new (FTP) FunctionProtoType(ResultTy, ArgArray, Canonical, newEPI);
  Types.push_back(FTP);
  if (!Unique)
    FunctionProtoTypes.InsertNode(FTP, InsertPos);
  return QualType(FTP, 0);
}

QualType ASTContext::getPipeType(QualType T, bool ReadOnly) const {
  llvm::FoldingSetNodeID ID;
  PipeType::Profile(ID, T, ReadOnly);

  void *InsertPos = nullptr;
  if (PipeType *PT = PipeTypes.FindNodeOrInsertPos(ID, InsertPos))
    return QualType(PT, 0);

  // If the pipe element type isn't canonical, this won't be a canonical type
  // either, so fill in the canonical type field.
  QualType Canonical;
  if (!T.isCanonical()) {
    Canonical = getPipeType(getCanonicalType(T), ReadOnly);

    // Get the new insert position for the node we care about.
    PipeType *NewIP = PipeTypes.FindNodeOrInsertPos(ID, InsertPos);
    assert(!NewIP && "Shouldn't be in the map!");
    (void)NewIP;
  }
  auto *New = new (*this, TypeAlignment) PipeType(T, Canonical, ReadOnly);
  Types.push_back(New);
  PipeTypes.InsertNode(New, InsertPos);
  return QualType(New, 0);
}

QualType ASTContext::adjustStringLiteralBaseType(QualType Ty) const {
  // OpenCL v1.1 s6.5.3: a string literal is in the constant address space.
  return LangOpts.OpenCL ? getAddrSpaceQualType(Ty, LangAS::opencl_constant)
                         : Ty;
}

QualType ASTContext::getReadPipeType(QualType T) const {
  return getPipeType(T, true);
}

QualType ASTContext::getWritePipeType(QualType T) const {
  return getPipeType(T, false);
}

#ifndef NDEBUG
static bool NeedsInjectedClassNameType(const RecordDecl *D) {
  if (!isa<CXXRecordDecl>(D)) return false;
  const auto *RD = cast<CXXRecordDecl>(D);
  if (isa<ClassTemplatePartialSpecializationDecl>(RD))
    return true;
  if (RD->getDescribedClassTemplate() &&
      !isa<ClassTemplateSpecializationDecl>(RD))
    return true;
  return false;
}
#endif

/// getInjectedClassNameType - Return the unique reference to the
/// injected class name type for the specified templated declaration.
QualType ASTContext::getInjectedClassNameType(CXXRecordDecl *Decl,
                                              QualType TST) const {
  assert(NeedsInjectedClassNameType(Decl));
  if (Decl->TypeForDecl) {
    assert(isa<InjectedClassNameType>(Decl->TypeForDecl));
  } else if (CXXRecordDecl *PrevDecl = Decl->getPreviousDecl()) {
    assert(PrevDecl->TypeForDecl && "previous declaration has no type");
    Decl->TypeForDecl = PrevDecl->TypeForDecl;
    assert(isa<InjectedClassNameType>(Decl->TypeForDecl));
  } else {
    Type *newType =
      new (*this, TypeAlignment) InjectedClassNameType(Decl, TST);
    Decl->TypeForDecl = newType;
    Types.push_back(newType);
  }
  return QualType(Decl->TypeForDecl, 0);
}

/// getTypeDeclType - Return the unique reference to the type for the
/// specified type declaration.
QualType ASTContext::getTypeDeclTypeSlow(const TypeDecl *Decl) const {
  assert(Decl && "Passed null for Decl param");
  assert(!Decl->TypeForDecl && "TypeForDecl present in slow case");

  if (const auto *Typedef = dyn_cast<TypedefNameDecl>(Decl))
    return getTypedefType(Typedef);

  assert(!isa<TemplateTypeParmDecl>(Decl) &&
         "Template type parameter types are always available.");

  if (const auto *Record = dyn_cast<RecordDecl>(Decl)) {
    assert(Record->isFirstDecl() && "struct/union has previous declaration");
    assert(!NeedsInjectedClassNameType(Record));
    return getRecordType(Record);
  } else if (const auto *Enum = dyn_cast<EnumDecl>(Decl)) {
    assert(Enum->isFirstDecl() && "enum has previous declaration");
    return getEnumType(Enum);
  } else if (const auto *Using = dyn_cast<UnresolvedUsingTypenameDecl>(Decl)) {
    Type *newType = new (*this, TypeAlignment) UnresolvedUsingType(Using);
    Decl->TypeForDecl = newType;
    Types.push_back(newType);
  } else
    llvm_unreachable("TypeDecl without a type?");

  return QualType(Decl->TypeForDecl, 0);
}

/// getTypedefType - Return the unique reference to the type for the
/// specified typedef name decl.
QualType
ASTContext::getTypedefType(const TypedefNameDecl *Decl,
                           QualType Canonical) const {
  if (Decl->TypeForDecl) return QualType(Decl->TypeForDecl, 0);

  if (Canonical.isNull())
    Canonical = getCanonicalType(Decl->getUnderlyingType());
  auto *newType = new (*this, TypeAlignment)
    TypedefType(Type::Typedef, Decl, Canonical);
  Decl->TypeForDecl = newType;
  Types.push_back(newType);
  return QualType(newType, 0);
}

QualType ASTContext::getRecordType(const RecordDecl *Decl) const {
  if (Decl->TypeForDecl) return QualType(Decl->TypeForDecl, 0);

  if (const RecordDecl *PrevDecl = Decl->getPreviousDecl())
    if (PrevDecl->TypeForDecl)
      return QualType(Decl->TypeForDecl = PrevDecl->TypeForDecl, 0);

  auto *newType = new (*this, TypeAlignment) RecordType(Decl);
  Decl->TypeForDecl = newType;
  Types.push_back(newType);
  return QualType(newType, 0);
}

QualType ASTContext::getEnumType(const EnumDecl *Decl) const {
  if (Decl->TypeForDecl) return QualType(Decl->TypeForDecl, 0);

  if (const EnumDecl *PrevDecl = Decl->getPreviousDecl())
    if (PrevDecl->TypeForDecl)
      return QualType(Decl->TypeForDecl = PrevDecl->TypeForDecl, 0);

  auto *newType = new (*this, TypeAlignment) EnumType(Decl);
  Decl->TypeForDecl = newType;
  Types.push_back(newType);
  return QualType(newType, 0);
}

QualType ASTContext::getAttributedType(attr::Kind attrKind,
                                       QualType modifiedType,
                                       QualType equivalentType) {
  llvm::FoldingSetNodeID id;
  AttributedType::Profile(id, attrKind, modifiedType, equivalentType);

  void *insertPos = nullptr;
  AttributedType *type = AttributedTypes.FindNodeOrInsertPos(id, insertPos);
  if (type) return QualType(type, 0);

  QualType canon = getCanonicalType(equivalentType);
  type = new (*this, TypeAlignment)
      AttributedType(canon, attrKind, modifiedType, equivalentType);

  Types.push_back(type);
  AttributedTypes.InsertNode(type, insertPos);

  return QualType(type, 0);
}

/// Retrieve a substitution-result type.
QualType
ASTContext::getSubstTemplateTypeParmType(const TemplateTypeParmType *Parm,
                                         QualType Replacement) const {
  assert(Replacement.isCanonical()
         && "replacement types must always be canonical");

  llvm::FoldingSetNodeID ID;
  SubstTemplateTypeParmType::Profile(ID, Parm, Replacement);
  void *InsertPos = nullptr;
  SubstTemplateTypeParmType *SubstParm
    = SubstTemplateTypeParmTypes.FindNodeOrInsertPos(ID, InsertPos);

  if (!SubstParm) {
    SubstParm = new (*this, TypeAlignment)
      SubstTemplateTypeParmType(Parm, Replacement);
    Types.push_back(SubstParm);
    SubstTemplateTypeParmTypes.InsertNode(SubstParm, InsertPos);
  }

  return QualType(SubstParm, 0);
}

/// Retrieve a
QualType ASTContext::getSubstTemplateTypeParmPackType(
                                          const TemplateTypeParmType *Parm,
                                              const TemplateArgument &ArgPack) {
#ifndef NDEBUG
  for (const auto &P : ArgPack.pack_elements()) {
    assert(P.getKind() == TemplateArgument::Type &&"Pack contains a non-type");
    assert(P.getAsType().isCanonical() && "Pack contains non-canonical type");
  }
#endif

  llvm::FoldingSetNodeID ID;
  SubstTemplateTypeParmPackType::Profile(ID, Parm, ArgPack);
  void *InsertPos = nullptr;
  if (SubstTemplateTypeParmPackType *SubstParm
        = SubstTemplateTypeParmPackTypes.FindNodeOrInsertPos(ID, InsertPos))
    return QualType(SubstParm, 0);

  QualType Canon;
  if (!Parm->isCanonicalUnqualified()) {
    Canon = getCanonicalType(QualType(Parm, 0));
    Canon = getSubstTemplateTypeParmPackType(cast<TemplateTypeParmType>(Canon),
                                             ArgPack);
    SubstTemplateTypeParmPackTypes.FindNodeOrInsertPos(ID, InsertPos);
  }

  auto *SubstParm
    = new (*this, TypeAlignment) SubstTemplateTypeParmPackType(Parm, Canon,
                                                               ArgPack);
  Types.push_back(SubstParm);
  SubstTemplateTypeParmPackTypes.InsertNode(SubstParm, InsertPos);
  return QualType(SubstParm, 0);
}

/// Retrieve the template type parameter type for a template
/// parameter or parameter pack with the given depth, index, and (optionally)
/// name.
QualType ASTContext::getTemplateTypeParmType(unsigned Depth, unsigned Index,
                                             bool ParameterPack,
                                             TemplateTypeParmDecl *TTPDecl) const {
  llvm::FoldingSetNodeID ID;
  TemplateTypeParmType::Profile(ID, Depth, Index, ParameterPack, TTPDecl);
  void *InsertPos = nullptr;
  TemplateTypeParmType *TypeParm
    = TemplateTypeParmTypes.FindNodeOrInsertPos(ID, InsertPos);

  if (TypeParm)
    return QualType(TypeParm, 0);

  if (TTPDecl) {
    QualType Canon = getTemplateTypeParmType(Depth, Index, ParameterPack);
    TypeParm = new (*this, TypeAlignment) TemplateTypeParmType(TTPDecl, Canon);

    TemplateTypeParmType *TypeCheck
      = TemplateTypeParmTypes.FindNodeOrInsertPos(ID, InsertPos);
    assert(!TypeCheck && "Template type parameter canonical type broken");
    (void)TypeCheck;
  } else
    TypeParm = new (*this, TypeAlignment)
      TemplateTypeParmType(Depth, Index, ParameterPack);

  Types.push_back(TypeParm);
  TemplateTypeParmTypes.InsertNode(TypeParm, InsertPos);

  return QualType(TypeParm, 0);
}

TypeSourceInfo *
ASTContext::getTemplateSpecializationTypeInfo(TemplateName Name,
                                              SourceLocation NameLoc,
                                        const TemplateArgumentListInfo &Args,
                                              QualType Underlying) const {
  assert(!Name.getAsDependentTemplateName() &&
         "No dependent template names here!");
  QualType TST = getTemplateSpecializationType(Name, Args, Underlying);

  TypeSourceInfo *DI = CreateTypeSourceInfo(TST);
  TemplateSpecializationTypeLoc TL =
      DI->getTypeLoc().castAs<TemplateSpecializationTypeLoc>();
  TL.setTemplateKeywordLoc(SourceLocation());
  TL.setTemplateNameLoc(NameLoc);
  TL.setLAngleLoc(Args.getLAngleLoc());
  TL.setRAngleLoc(Args.getRAngleLoc());
  for (unsigned i = 0, e = TL.getNumArgs(); i != e; ++i)
    TL.setArgLocInfo(i, Args[i].getLocInfo());
  return DI;
}

QualType
ASTContext::getTemplateSpecializationType(TemplateName Template,
                                          const TemplateArgumentListInfo &Args,
                                          QualType Underlying) const {
  assert(!Template.getAsDependentTemplateName() &&
         "No dependent template names here!");

  SmallVector<TemplateArgument, 4> ArgVec;
  ArgVec.reserve(Args.size());
  for (const TemplateArgumentLoc &Arg : Args.arguments())
    ArgVec.push_back(Arg.getArgument());

  return getTemplateSpecializationType(Template, ArgVec, Underlying);
}

#ifndef NDEBUG
static bool hasAnyPackExpansions(ArrayRef<TemplateArgument> Args) {
  for (const TemplateArgument &Arg : Args)
    if (Arg.isPackExpansion())
      return true;

  return true;
}
#endif

QualType
ASTContext::getTemplateSpecializationType(TemplateName Template,
                                          ArrayRef<TemplateArgument> Args,
                                          QualType Underlying) const {
  assert(!Template.getAsDependentTemplateName() &&
         "No dependent template names here!");
  // Look through qualified template names.
  if (QualifiedTemplateName *QTN = Template.getAsQualifiedTemplateName())
    Template = TemplateName(QTN->getTemplateDecl());

  bool IsTypeAlias =
    Template.getAsTemplateDecl() &&
    isa<TypeAliasTemplateDecl>(Template.getAsTemplateDecl());
  QualType CanonType;
  if (!Underlying.isNull())
    CanonType = getCanonicalType(Underlying);
  else {
    // We can get here with an alias template when the specialization contains
    // a pack expansion that does not match up with a parameter pack.
    assert((!IsTypeAlias || hasAnyPackExpansions(Args)) &&
           "Caller must compute aliased type");
    IsTypeAlias = false;
    CanonType = getCanonicalTemplateSpecializationType(Template, Args);
  }

  // Allocate the (non-canonical) template specialization type, but don't
  // try to unique it: these types typically have location information that
  // we don't unique and don't want to lose.
  void *Mem = Allocate(sizeof(TemplateSpecializationType) +
                       sizeof(TemplateArgument) * Args.size() +
                       (IsTypeAlias? sizeof(QualType) : 0),
                       TypeAlignment);
  auto *Spec
    = new (Mem) TemplateSpecializationType(Template, Args, CanonType,
                                         IsTypeAlias ? Underlying : QualType());

  Types.push_back(Spec);
  return QualType(Spec, 0);
}

QualType ASTContext::getCanonicalTemplateSpecializationType(
    TemplateName Template, ArrayRef<TemplateArgument> Args) const {
  assert(!Template.getAsDependentTemplateName() &&
         "No dependent template names here!");

  // Look through qualified template names.
  if (QualifiedTemplateName *QTN = Template.getAsQualifiedTemplateName())
    Template = TemplateName(QTN->getTemplateDecl());

  // Build the canonical template specialization type.
  TemplateName CanonTemplate = getCanonicalTemplateName(Template);
  SmallVector<TemplateArgument, 4> CanonArgs;
  unsigned NumArgs = Args.size();
  CanonArgs.reserve(NumArgs);
  for (const TemplateArgument &Arg : Args)
    CanonArgs.push_back(getCanonicalTemplateArgument(Arg));

  // Determine whether this canonical template specialization type already
  // exists.
  llvm::FoldingSetNodeID ID;
  TemplateSpecializationType::Profile(ID, CanonTemplate,
                                      CanonArgs, *this);

  void *InsertPos = nullptr;
  TemplateSpecializationType *Spec
    = TemplateSpecializationTypes.FindNodeOrInsertPos(ID, InsertPos);

  if (!Spec) {
    // Allocate a new canonical template specialization type.
    void *Mem = Allocate((sizeof(TemplateSpecializationType) +
                          sizeof(TemplateArgument) * NumArgs),
                         TypeAlignment);
    Spec = new (Mem) TemplateSpecializationType(CanonTemplate,
                                                CanonArgs,
                                                QualType(), QualType());
    Types.push_back(Spec);
    TemplateSpecializationTypes.InsertNode(Spec, InsertPos);
  }

  assert(Spec->isDependentType() &&
         "Non-dependent template-id type must have a canonical type");
  return QualType(Spec, 0);
}

QualType ASTContext::getElaboratedType(ElaboratedTypeKeyword Keyword,
                                       NestedNameSpecifier *NNS,
                                       QualType NamedType,
                                       TagDecl *OwnedTagDecl) const {
  llvm::FoldingSetNodeID ID;
  ElaboratedType::Profile(ID, Keyword, NNS, NamedType, OwnedTagDecl);

  void *InsertPos = nullptr;
  ElaboratedType *T = ElaboratedTypes.FindNodeOrInsertPos(ID, InsertPos);
  if (T)
    return QualType(T, 0);

  QualType Canon = NamedType;
  if (!Canon.isCanonical()) {
    Canon = getCanonicalType(NamedType);
    ElaboratedType *CheckT = ElaboratedTypes.FindNodeOrInsertPos(ID, InsertPos);
    assert(!CheckT && "Elaborated canonical type broken");
    (void)CheckT;
  }

  void *Mem = Allocate(ElaboratedType::totalSizeToAlloc<TagDecl *>(!!OwnedTagDecl),
                       TypeAlignment);
  T = new (Mem) ElaboratedType(Keyword, NNS, NamedType, Canon, OwnedTagDecl);

  Types.push_back(T);
  ElaboratedTypes.InsertNode(T, InsertPos);
  return QualType(T, 0);
}

QualType
ASTContext::getParenType(QualType InnerType) const {
  llvm::FoldingSetNodeID ID;
  ParenType::Profile(ID, InnerType);

  void *InsertPos = nullptr;
  ParenType *T = ParenTypes.FindNodeOrInsertPos(ID, InsertPos);
  if (T)
    return QualType(T, 0);

  QualType Canon = InnerType;
  if (!Canon.isCanonical()) {
    Canon = getCanonicalType(InnerType);
    ParenType *CheckT = ParenTypes.FindNodeOrInsertPos(ID, InsertPos);
    assert(!CheckT && "Paren canonical type broken");
    (void)CheckT;
  }

  T = new (*this, TypeAlignment) ParenType(InnerType, Canon);
  Types.push_back(T);
  ParenTypes.InsertNode(T, InsertPos);
  return QualType(T, 0);
}

QualType
ASTContext::getMacroQualifiedType(QualType UnderlyingTy,
                                  const IdentifierInfo *MacroII) const {
  QualType Canon = UnderlyingTy;
  if (!Canon.isCanonical())
    Canon = getCanonicalType(UnderlyingTy);

  auto *newType = new (*this, TypeAlignment)
      MacroQualifiedType(UnderlyingTy, Canon, MacroII);
  Types.push_back(newType);
  return QualType(newType, 0);
}

QualType ASTContext::getDependentNameType(ElaboratedTypeKeyword Keyword,
                                          NestedNameSpecifier *NNS,
                                          const IdentifierInfo *Name,
                                          QualType Canon) const {
  if (Canon.isNull()) {
    NestedNameSpecifier *CanonNNS = getCanonicalNestedNameSpecifier(NNS);
    if (CanonNNS != NNS)
      Canon = getDependentNameType(Keyword, CanonNNS, Name);
  }

  llvm::FoldingSetNodeID ID;
  DependentNameType::Profile(ID, Keyword, NNS, Name);

  void *InsertPos = nullptr;
  DependentNameType *T
    = DependentNameTypes.FindNodeOrInsertPos(ID, InsertPos);
  if (T)
    return QualType(T, 0);

  T = new (*this, TypeAlignment) DependentNameType(Keyword, NNS, Name, Canon);
  Types.push_back(T);
  DependentNameTypes.InsertNode(T, InsertPos);
  return QualType(T, 0);
}

QualType
ASTContext::getDependentTemplateSpecializationType(
                                 ElaboratedTypeKeyword Keyword,
                                 NestedNameSpecifier *NNS,
                                 const IdentifierInfo *Name,
                                 const TemplateArgumentListInfo &Args) const {
  // TODO: avoid this copy
  SmallVector<TemplateArgument, 16> ArgCopy;
  for (unsigned I = 0, E = Args.size(); I != E; ++I)
    ArgCopy.push_back(Args[I].getArgument());
  return getDependentTemplateSpecializationType(Keyword, NNS, Name, ArgCopy);
}

QualType
ASTContext::getDependentTemplateSpecializationType(
                                 ElaboratedTypeKeyword Keyword,
                                 NestedNameSpecifier *NNS,
                                 const IdentifierInfo *Name,
                                 ArrayRef<TemplateArgument> Args) const {
  assert((!NNS || NNS->isDependent()) &&
         "nested-name-specifier must be dependent");

  llvm::FoldingSetNodeID ID;
  DependentTemplateSpecializationType::Profile(ID, *this, Keyword, NNS,
                                               Name, Args);

  void *InsertPos = nullptr;
  DependentTemplateSpecializationType *T
    = DependentTemplateSpecializationTypes.FindNodeOrInsertPos(ID, InsertPos);
  if (T)
    return QualType(T, 0);

  NestedNameSpecifier *CanonNNS = getCanonicalNestedNameSpecifier(NNS);

  ElaboratedTypeKeyword CanonKeyword = Keyword;
  if (Keyword == ETK_None) CanonKeyword = ETK_Typename;

  bool AnyNonCanonArgs = false;
  unsigned NumArgs = Args.size();
  SmallVector<TemplateArgument, 16> CanonArgs(NumArgs);
  for (unsigned I = 0; I != NumArgs; ++I) {
    CanonArgs[I] = getCanonicalTemplateArgument(Args[I]);
    if (!CanonArgs[I].structurallyEquals(Args[I]))
      AnyNonCanonArgs = true;
  }

  QualType Canon;
  if (AnyNonCanonArgs || CanonNNS != NNS || CanonKeyword != Keyword) {
    Canon = getDependentTemplateSpecializationType(CanonKeyword, CanonNNS,
                                                   Name,
                                                   CanonArgs);

    // Find the insert position again.
    DependentTemplateSpecializationTypes.FindNodeOrInsertPos(ID, InsertPos);
  }

  void *Mem = Allocate((sizeof(DependentTemplateSpecializationType) +
                        sizeof(TemplateArgument) * NumArgs),
                       TypeAlignment);
  T = new (Mem) DependentTemplateSpecializationType(Keyword, NNS,
                                                    Name, Args, Canon);
  Types.push_back(T);
  DependentTemplateSpecializationTypes.InsertNode(T, InsertPos);
  return QualType(T, 0);
}

TemplateArgument ASTContext::getInjectedTemplateArg(NamedDecl *Param) {
  TemplateArgument Arg;
  if (const auto *TTP = dyn_cast<TemplateTypeParmDecl>(Param)) {
    QualType ArgType = getTypeDeclType(TTP);
    if (TTP->isParameterPack())
      ArgType = getPackExpansionType(ArgType, None);

    Arg = TemplateArgument(ArgType);
  } else if (auto *NTTP = dyn_cast<NonTypeTemplateParmDecl>(Param)) {
    Expr *E = new (*this) DeclRefExpr(
        *this, NTTP, /*enclosing*/ false,
        NTTP->getType().getNonLValueExprType(*this),
        Expr::getValueKindForType(NTTP->getType()), NTTP->getLocation());

    if (NTTP->isParameterPack())
      E = new (*this) PackExpansionExpr(DependentTy, E, NTTP->getLocation(),
                                        None);
    Arg = TemplateArgument(E);
  } else {
    auto *TTP = cast<TemplateTemplateParmDecl>(Param);
    if (TTP->isParameterPack())
      Arg = TemplateArgument(TemplateName(TTP), Optional<unsigned>());
    else
      Arg = TemplateArgument(TemplateName(TTP));
  }

  if (Param->isTemplateParameterPack())
    Arg = TemplateArgument::CreatePackCopy(*this, Arg);

  return Arg;
}

void
ASTContext::getInjectedTemplateArgs(const TemplateParameterList *Params,
                                    SmallVectorImpl<TemplateArgument> &Args) {
  Args.reserve(Args.size() + Params->size());

  for (NamedDecl *Param : *Params)
    Args.push_back(getInjectedTemplateArg(Param));
}

QualType ASTContext::getPackExpansionType(QualType Pattern,
                                          Optional<unsigned> NumExpansions) {
  llvm::FoldingSetNodeID ID;
  PackExpansionType::Profile(ID, Pattern, NumExpansions);

  // A deduced type can deduce to a pack, eg
  //   auto ...x = some_pack;
  // That declaration isn't (yet) valid, but is created as part of building an
  // init-capture pack:
  //   [...x = some_pack] {}
  assert((Pattern->containsUnexpandedParameterPack() ||
          Pattern->getContainedDeducedType()) &&
         "Pack expansions must expand one or more parameter packs");
  void *InsertPos = nullptr;
  PackExpansionType *T
    = PackExpansionTypes.FindNodeOrInsertPos(ID, InsertPos);
  if (T)
    return QualType(T, 0);

  QualType Canon;
  if (!Pattern.isCanonical()) {
    Canon = getCanonicalType(Pattern);
    // The canonical type might not contain an unexpanded parameter pack, if it
    // contains an alias template specialization which ignores one of its
    // parameters.
    if (Canon->containsUnexpandedParameterPack()) {
      Canon = getPackExpansionType(Canon, NumExpansions);

      // Find the insert position again, in case we inserted an element into
      // PackExpansionTypes and invalidated our insert position.
      PackExpansionTypes.FindNodeOrInsertPos(ID, InsertPos);
    }
  }

  T = new (*this, TypeAlignment)
      PackExpansionType(Pattern, Canon, NumExpansions);
  Types.push_back(T);
  PackExpansionTypes.InsertNode(T, InsertPos);
  return QualType(T, 0);
}

/// CmpProtocolNames - Comparison predicate for sorting protocols
/// alphabetically.
static int CmpProtocolNames(ObjCProtocolDecl *const *LHS,
                            ObjCProtocolDecl *const *RHS) {
  return DeclarationName::compare((*LHS)->getDeclName(), (*RHS)->getDeclName());
}

static bool areSortedAndUniqued(ArrayRef<ObjCProtocolDecl *> Protocols) {
  if (Protocols.empty()) return true;

  if (Protocols[0]->getCanonicalDecl() != Protocols[0])
    return false;

  for (unsigned i = 1; i != Protocols.size(); ++i)
    if (CmpProtocolNames(&Protocols[i - 1], &Protocols[i]) >= 0 ||
        Protocols[i]->getCanonicalDecl() != Protocols[i])
      return false;
  return true;
}

static void
SortAndUniqueProtocols(SmallVectorImpl<ObjCProtocolDecl *> &Protocols) {
  // Sort protocols, keyed by name.
  llvm::array_pod_sort(Protocols.begin(), Protocols.end(), CmpProtocolNames);

  // Canonicalize.
  for (ObjCProtocolDecl *&P : Protocols)
    P = P->getCanonicalDecl();

  // Remove duplicates.
  auto ProtocolsEnd = std::unique(Protocols.begin(), Protocols.end());
  Protocols.erase(ProtocolsEnd, Protocols.end());
}

QualType ASTContext::getObjCObjectType(QualType BaseType,
                                       ObjCProtocolDecl * const *Protocols,
                                       unsigned NumProtocols) const {
  return getObjCObjectType(BaseType, {},
                           llvm::makeArrayRef(Protocols, NumProtocols),
                           /*isKindOf=*/false);
}

QualType ASTContext::getObjCObjectType(
           QualType baseType,
           ArrayRef<QualType> typeArgs,
           ArrayRef<ObjCProtocolDecl *> protocols,
           bool isKindOf) const {
  // If the base type is an interface and there aren't any protocols or
  // type arguments to add, then the interface type will do just fine.
  if (typeArgs.empty() && protocols.empty() && !isKindOf &&
      isa<ObjCInterfaceType>(baseType))
    return baseType;

  // Look in the folding set for an existing type.
  llvm::FoldingSetNodeID ID;
  ObjCObjectTypeImpl::Profile(ID, baseType, typeArgs, protocols, isKindOf);
  void *InsertPos = nullptr;
  if (ObjCObjectType *QT = ObjCObjectTypes.FindNodeOrInsertPos(ID, InsertPos))
    return QualType(QT, 0);

  // Determine the type arguments to be used for canonicalization,
  // which may be explicitly specified here or written on the base
  // type.
  ArrayRef<QualType> effectiveTypeArgs = typeArgs;
  if (effectiveTypeArgs.empty()) {
    if (const auto *baseObject = baseType->getAs<ObjCObjectType>())
      effectiveTypeArgs = baseObject->getTypeArgs();
  }

  // Build the canonical type, which has the canonical base type and a
  // sorted-and-uniqued list of protocols and the type arguments
  // canonicalized.
  QualType canonical;
  bool typeArgsAreCanonical = std::all_of(effectiveTypeArgs.begin(),
                                          effectiveTypeArgs.end(),
                                          [&](QualType type) {
                                            return type.isCanonical();
                                          });
  bool protocolsSorted = areSortedAndUniqued(protocols);
  if (!typeArgsAreCanonical || !protocolsSorted || !baseType.isCanonical()) {
    // Determine the canonical type arguments.
    ArrayRef<QualType> canonTypeArgs;
    SmallVector<QualType, 4> canonTypeArgsVec;
    if (!typeArgsAreCanonical) {
      canonTypeArgsVec.reserve(effectiveTypeArgs.size());
      for (auto typeArg : effectiveTypeArgs)
        canonTypeArgsVec.push_back(getCanonicalType(typeArg));
      canonTypeArgs = canonTypeArgsVec;
    } else {
      canonTypeArgs = effectiveTypeArgs;
    }

    ArrayRef<ObjCProtocolDecl *> canonProtocols;
    SmallVector<ObjCProtocolDecl*, 8> canonProtocolsVec;
    if (!protocolsSorted) {
      canonProtocolsVec.append(protocols.begin(), protocols.end());
      SortAndUniqueProtocols(canonProtocolsVec);
      canonProtocols = canonProtocolsVec;
    } else {
      canonProtocols = protocols;
    }

    canonical = getObjCObjectType(getCanonicalType(baseType), canonTypeArgs,
                                  canonProtocols, isKindOf);

    // Regenerate InsertPos.
    ObjCObjectTypes.FindNodeOrInsertPos(ID, InsertPos);
  }

  unsigned size = sizeof(ObjCObjectTypeImpl);
  size += typeArgs.size() * sizeof(QualType);
  size += protocols.size() * sizeof(ObjCProtocolDecl *);
  void *mem = Allocate(size, TypeAlignment);
  auto *T =
    new (mem) ObjCObjectTypeImpl(canonical, baseType, typeArgs, protocols,
                                 isKindOf);

  Types.push_back(T);
  ObjCObjectTypes.InsertNode(T, InsertPos);
  return QualType(T, 0);
}

/// Apply Objective-C protocol qualifiers to the given type.
/// If this is for the canonical type of a type parameter, we can apply
/// protocol qualifiers on the ObjCObjectPointerType.
QualType
ASTContext::applyObjCProtocolQualifiers(QualType type,
                  ArrayRef<ObjCProtocolDecl *> protocols, bool &hasError,
                  bool allowOnPointerType) const {
  hasError = false;

  if (const auto *objT = dyn_cast<ObjCTypeParamType>(type.getTypePtr())) {
    return getObjCTypeParamType(objT->getDecl(), protocols);
  }

  // Apply protocol qualifiers to ObjCObjectPointerType.
  if (allowOnPointerType) {
    if (const auto *objPtr =
            dyn_cast<ObjCObjectPointerType>(type.getTypePtr())) {
      const ObjCObjectType *objT = objPtr->getObjectType();
      // Merge protocol lists and construct ObjCObjectType.
      SmallVector<ObjCProtocolDecl*, 8> protocolsVec;
      protocolsVec.append(objT->qual_begin(),
                          objT->qual_end());
      protocolsVec.append(protocols.begin(), protocols.end());
      ArrayRef<ObjCProtocolDecl *> protocols = protocolsVec;
      type = getObjCObjectType(
             objT->getBaseType(),
             objT->getTypeArgsAsWritten(),
             protocols,
             objT->isKindOfTypeAsWritten());
      return getObjCObjectPointerType(type);
    }
  }

  // Apply protocol qualifiers to ObjCObjectType.
  if (const auto *objT = dyn_cast<ObjCObjectType>(type.getTypePtr())){
    // FIXME: Check for protocols to which the class type is already
    // known to conform.

    return getObjCObjectType(objT->getBaseType(),
                             objT->getTypeArgsAsWritten(),
                             protocols,
                             objT->isKindOfTypeAsWritten());
  }

  // If the canonical type is ObjCObjectType, ...
  if (type->isObjCObjectType()) {
    // Silently overwrite any existing protocol qualifiers.
    // TODO: determine whether that's the right thing to do.

    // FIXME: Check for protocols to which the class type is already
    // known to conform.
    return getObjCObjectType(type, {}, protocols, false);
  }

  // id<protocol-list>
  if (type->isObjCIdType()) {
    const auto *objPtr = type->castAs<ObjCObjectPointerType>();
    type = getObjCObjectType(ObjCBuiltinIdTy, {}, protocols,
                                 objPtr->isKindOfType());
    return getObjCObjectPointerType(type);
  }

  // Class<protocol-list>
  if (type->isObjCClassType()) {
    const auto *objPtr = type->castAs<ObjCObjectPointerType>();
    type = getObjCObjectType(ObjCBuiltinClassTy, {}, protocols,
                                 objPtr->isKindOfType());
    return getObjCObjectPointerType(type);
  }

  hasError = true;
  return type;
}

QualType
ASTContext::getObjCTypeParamType(const ObjCTypeParamDecl *Decl,
                                 ArrayRef<ObjCProtocolDecl *> protocols) const {
  // Look in the folding set for an existing type.
  llvm::FoldingSetNodeID ID;
  ObjCTypeParamType::Profile(ID, Decl, protocols);
  void *InsertPos = nullptr;
  if (ObjCTypeParamType *TypeParam =
      ObjCTypeParamTypes.FindNodeOrInsertPos(ID, InsertPos))
    return QualType(TypeParam, 0);

  // We canonicalize to the underlying type.
  QualType Canonical = getCanonicalType(Decl->getUnderlyingType());
  if (!protocols.empty()) {
    // Apply the protocol qualifers.
    bool hasError;
    Canonical = getCanonicalType(applyObjCProtocolQualifiers(
        Canonical, protocols, hasError, true /*allowOnPointerType*/));
    assert(!hasError && "Error when apply protocol qualifier to bound type");
  }

  unsigned size = sizeof(ObjCTypeParamType);
  size += protocols.size() * sizeof(ObjCProtocolDecl *);
  void *mem = Allocate(size, TypeAlignment);
  auto *newType = new (mem) ObjCTypeParamType(Decl, Canonical, protocols);

  Types.push_back(newType);
  ObjCTypeParamTypes.InsertNode(newType, InsertPos);
  return QualType(newType, 0);
}

/// ObjCObjectAdoptsQTypeProtocols - Checks that protocols in IC's
/// protocol list adopt all protocols in QT's qualified-id protocol
/// list.
bool ASTContext::ObjCObjectAdoptsQTypeProtocols(QualType QT,
                                                ObjCInterfaceDecl *IC) {
  if (!QT->isObjCQualifiedIdType())
    return false;

  if (const auto *OPT = QT->getAs<ObjCObjectPointerType>()) {
    // If both the right and left sides have qualifiers.
    for (auto *Proto : OPT->quals()) {
      if (!IC->ClassImplementsProtocol(Proto, false))
        return false;
    }
    return true;
  }
  return false;
}

/// QIdProtocolsAdoptObjCObjectProtocols - Checks that protocols in
/// QT's qualified-id protocol list adopt all protocols in IDecl's list
/// of protocols.
bool ASTContext::QIdProtocolsAdoptObjCObjectProtocols(QualType QT,
                                                ObjCInterfaceDecl *IDecl) {
  if (!QT->isObjCQualifiedIdType())
    return false;
  const auto *OPT = QT->getAs<ObjCObjectPointerType>();
  if (!OPT)
    return false;
  if (!IDecl->hasDefinition())
    return false;
  llvm::SmallPtrSet<ObjCProtocolDecl *, 8> InheritedProtocols;
  CollectInheritedProtocols(IDecl, InheritedProtocols);
  if (InheritedProtocols.empty())
    return false;
  // Check that if every protocol in list of id<plist> conforms to a protocol
  // of IDecl's, then bridge casting is ok.
  bool Conforms = false;
  for (auto *Proto : OPT->quals()) {
    Conforms = false;
    for (auto *PI : InheritedProtocols) {
      if (ProtocolCompatibleWithProtocol(Proto, PI)) {
        Conforms = true;
        break;
      }
    }
    if (!Conforms)
      break;
  }
  if (Conforms)
    return true;

  for (auto *PI : InheritedProtocols) {
    // If both the right and left sides have qualifiers.
    bool Adopts = false;
    for (auto *Proto : OPT->quals()) {
      // return 'true' if 'PI' is in the inheritance hierarchy of Proto
      if ((Adopts = ProtocolCompatibleWithProtocol(PI, Proto)))
        break;
    }
    if (!Adopts)
      return false;
  }
  return true;
}

/// getObjCObjectPointerType - Return a ObjCObjectPointerType type for
/// the given object type.
QualType ASTContext::getObjCObjectPointerType(QualType ObjectT) const {
  llvm::FoldingSetNodeID ID;
  ObjCObjectPointerType::Profile(ID, ObjectT);

  void *InsertPos = nullptr;
  if (ObjCObjectPointerType *QT =
              ObjCObjectPointerTypes.FindNodeOrInsertPos(ID, InsertPos))
    return QualType(QT, 0);

  // Find the canonical object type.
  QualType Canonical;
  if (!ObjectT.isCanonical()) {
    Canonical = getObjCObjectPointerType(getCanonicalType(ObjectT));

    // Regenerate InsertPos.
    ObjCObjectPointerTypes.FindNodeOrInsertPos(ID, InsertPos);
  }

  // No match.
  void *Mem = Allocate(sizeof(ObjCObjectPointerType), TypeAlignment);
  auto *QType =
    new (Mem) ObjCObjectPointerType(Canonical, ObjectT);

  Types.push_back(QType);
  ObjCObjectPointerTypes.InsertNode(QType, InsertPos);
  return QualType(QType, 0);
}

/// getObjCInterfaceType - Return the unique reference to the type for the
/// specified ObjC interface decl. The list of protocols is optional.
QualType ASTContext::getObjCInterfaceType(const ObjCInterfaceDecl *Decl,
                                          ObjCInterfaceDecl *PrevDecl) const {
  if (Decl->TypeForDecl)
    return QualType(Decl->TypeForDecl, 0);

  if (PrevDecl) {
    assert(PrevDecl->TypeForDecl && "previous decl has no TypeForDecl");
    Decl->TypeForDecl = PrevDecl->TypeForDecl;
    return QualType(PrevDecl->TypeForDecl, 0);
  }

  // Prefer the definition, if there is one.
  if (const ObjCInterfaceDecl *Def = Decl->getDefinition())
    Decl = Def;

  void *Mem = Allocate(sizeof(ObjCInterfaceType), TypeAlignment);
  auto *T = new (Mem) ObjCInterfaceType(Decl);
  Decl->TypeForDecl = T;
  Types.push_back(T);
  return QualType(T, 0);
}

/// getTypeOfExprType - Unlike many "get<Type>" functions, we can't unique
/// TypeOfExprType AST's (since expression's are never shared). For example,
/// multiple declarations that refer to "typeof(x)" all contain different
/// DeclRefExpr's. This doesn't effect the type checker, since it operates
/// on canonical type's (which are always unique).
QualType ASTContext::getTypeOfExprType(Expr *tofExpr) const {
  TypeOfExprType *toe;
  if (tofExpr->isTypeDependent()) {
    llvm::FoldingSetNodeID ID;
    DependentTypeOfExprType::Profile(ID, *this, tofExpr);

    void *InsertPos = nullptr;
    DependentTypeOfExprType *Canon
      = DependentTypeOfExprTypes.FindNodeOrInsertPos(ID, InsertPos);
    if (Canon) {
      // We already have a "canonical" version of an identical, dependent
      // typeof(expr) type. Use that as our canonical type.
      toe = new (*this, TypeAlignment) TypeOfExprType(tofExpr,
                                          QualType((TypeOfExprType*)Canon, 0));
    } else {
      // Build a new, canonical typeof(expr) type.
      Canon
        = new (*this, TypeAlignment) DependentTypeOfExprType(*this, tofExpr);
      DependentTypeOfExprTypes.InsertNode(Canon, InsertPos);
      toe = Canon;
    }
  } else {
    QualType Canonical = getCanonicalType(tofExpr->getType());
    toe = new (*this, TypeAlignment) TypeOfExprType(tofExpr, Canonical);
  }
  Types.push_back(toe);
  return QualType(toe, 0);
}

/// getTypeOfType -  Unlike many "get<Type>" functions, we don't unique
/// TypeOfType nodes. The only motivation to unique these nodes would be
/// memory savings. Since typeof(t) is fairly uncommon, space shouldn't be
/// an issue. This doesn't affect the type checker, since it operates
/// on canonical types (which are always unique).
QualType ASTContext::getTypeOfType(QualType tofType) const {
  QualType Canonical = getCanonicalType(tofType);
  auto *tot = new (*this, TypeAlignment) TypeOfType(tofType, Canonical);
  Types.push_back(tot);
  return QualType(tot, 0);
}

/// Unlike many "get<Type>" functions, we don't unique DecltypeType
/// nodes. This would never be helpful, since each such type has its own
/// expression, and would not give a significant memory saving, since there
/// is an Expr tree under each such type.
QualType ASTContext::getDecltypeType(Expr *e, QualType UnderlyingType) const {
  DecltypeType *dt;

  // C++11 [temp.type]p2:
  //   If an expression e involves a template parameter, decltype(e) denotes a
  //   unique dependent type. Two such decltype-specifiers refer to the same
  //   type only if their expressions are equivalent (14.5.6.1).
  if (e->isInstantiationDependent()) {
    llvm::FoldingSetNodeID ID;
    DependentDecltypeType::Profile(ID, *this, e);

    void *InsertPos = nullptr;
    DependentDecltypeType *Canon
      = DependentDecltypeTypes.FindNodeOrInsertPos(ID, InsertPos);
    if (!Canon) {
      // Build a new, canonical decltype(expr) type.
      Canon = new (*this, TypeAlignment) DependentDecltypeType(*this, e);
      DependentDecltypeTypes.InsertNode(Canon, InsertPos);
    }
    dt = new (*this, TypeAlignment)
        DecltypeType(e, UnderlyingType, QualType((DecltypeType *)Canon, 0));
  } else {
    dt = new (*this, TypeAlignment)
        DecltypeType(e, UnderlyingType, getCanonicalType(UnderlyingType));
  }
  Types.push_back(dt);
  return QualType(dt, 0);
}

/// getUnaryTransformationType - We don't unique these, since the memory
/// savings are minimal and these are rare.
QualType ASTContext::getUnaryTransformType(QualType BaseType,
                                           QualType UnderlyingType,
                                           UnaryTransformType::UTTKind Kind)
    const {
  UnaryTransformType *ut = nullptr;

  if (BaseType->isDependentType()) {
    // Look in the folding set for an existing type.
    llvm::FoldingSetNodeID ID;
    DependentUnaryTransformType::Profile(ID, getCanonicalType(BaseType), Kind);

    void *InsertPos = nullptr;
    DependentUnaryTransformType *Canon
      = DependentUnaryTransformTypes.FindNodeOrInsertPos(ID, InsertPos);

    if (!Canon) {
      // Build a new, canonical __underlying_type(type) type.
      Canon = new (*this, TypeAlignment)
             DependentUnaryTransformType(*this, getCanonicalType(BaseType),
                                         Kind);
      DependentUnaryTransformTypes.InsertNode(Canon, InsertPos);
    }
    ut = new (*this, TypeAlignment) UnaryTransformType (BaseType,
                                                        QualType(), Kind,
                                                        QualType(Canon, 0));
  } else {
    QualType CanonType = getCanonicalType(UnderlyingType);
    ut = new (*this, TypeAlignment) UnaryTransformType (BaseType,
                                                        UnderlyingType, Kind,
                                                        CanonType);
  }
  Types.push_back(ut);
  return QualType(ut, 0);
}

/// getAutoType - Return the uniqued reference to the 'auto' type which has been
/// deduced to the given type, or to the canonical undeduced 'auto' type, or the
/// canonical deduced-but-dependent 'auto' type.
QualType ASTContext::getAutoType(QualType DeducedType, AutoTypeKeyword Keyword,
                                 bool IsDependent, bool IsPack) const {
  assert((!IsPack || IsDependent) && "only use IsPack for a dependent pack");
  if (DeducedType.isNull() && Keyword == AutoTypeKeyword::Auto && !IsDependent)
    return getAutoDeductType();

  // Look in the folding set for an existing type.
  void *InsertPos = nullptr;
  llvm::FoldingSetNodeID ID;
  AutoType::Profile(ID, DeducedType, Keyword, IsDependent, IsPack);
  if (AutoType *AT = AutoTypes.FindNodeOrInsertPos(ID, InsertPos))
    return QualType(AT, 0);

  auto *AT = new (*this, TypeAlignment)
      AutoType(DeducedType, Keyword, IsDependent, IsPack);
  Types.push_back(AT);
  if (InsertPos)
    AutoTypes.InsertNode(AT, InsertPos);
  return QualType(AT, 0);
}

/// Return the uniqued reference to the deduced template specialization type
/// which has been deduced to the given type, or to the canonical undeduced
/// such type, or the canonical deduced-but-dependent such type.
QualType ASTContext::getDeducedTemplateSpecializationType(
    TemplateName Template, QualType DeducedType, bool IsDependent) const {
  // Look in the folding set for an existing type.
  void *InsertPos = nullptr;
  llvm::FoldingSetNodeID ID;
  DeducedTemplateSpecializationType::Profile(ID, Template, DeducedType,
                                             IsDependent);
  if (DeducedTemplateSpecializationType *DTST =
          DeducedTemplateSpecializationTypes.FindNodeOrInsertPos(ID, InsertPos))
    return QualType(DTST, 0);

  auto *DTST = new (*this, TypeAlignment)
      DeducedTemplateSpecializationType(Template, DeducedType, IsDependent);
  Types.push_back(DTST);
  if (InsertPos)
    DeducedTemplateSpecializationTypes.InsertNode(DTST, InsertPos);
  return QualType(DTST, 0);
}

/// getAtomicType - Return the uniqued reference to the atomic type for
/// the given value type.
QualType ASTContext::getAtomicType(QualType T) const {
  // Unique pointers, to guarantee there is only one pointer of a particular
  // structure.
  llvm::FoldingSetNodeID ID;
  AtomicType::Profile(ID, T);

  void *InsertPos = nullptr;
  if (AtomicType *AT = AtomicTypes.FindNodeOrInsertPos(ID, InsertPos))
    return QualType(AT, 0);

  // If the atomic value type isn't canonical, this won't be a canonical type
  // either, so fill in the canonical type field.
  QualType Canonical;
  if (!T.isCanonical()) {
    Canonical = getAtomicType(getCanonicalType(T));

    // Get the new insert position for the node we care about.
    AtomicType *NewIP = AtomicTypes.FindNodeOrInsertPos(ID, InsertPos);
    assert(!NewIP && "Shouldn't be in the map!"); (void)NewIP;
  }
  auto *New = new (*this, TypeAlignment) AtomicType(T, Canonical);
  Types.push_back(New);
  AtomicTypes.InsertNode(New, InsertPos);
  return QualType(New, 0);
}

/// getAutoDeductType - Get type pattern for deducing against 'auto'.
QualType ASTContext::getAutoDeductType() const {
  if (AutoDeductTy.isNull())
    AutoDeductTy = QualType(
      new (*this, TypeAlignment) AutoType(QualType(), AutoTypeKeyword::Auto,
                                          /*dependent*/false, /*pack*/false),
      0);
  return AutoDeductTy;
}

/// getAutoRRefDeductType - Get type pattern for deducing against 'auto &&'.
QualType ASTContext::getAutoRRefDeductType() const {
  if (AutoRRefDeductTy.isNull())
    AutoRRefDeductTy = getRValueReferenceType(getAutoDeductType());
  assert(!AutoRRefDeductTy.isNull() && "can't build 'auto &&' pattern");
  return AutoRRefDeductTy;
}

/// getTagDeclType - Return the unique reference to the type for the
/// specified TagDecl (struct/union/class/enum) decl.
QualType ASTContext::getTagDeclType(const TagDecl *Decl) const {
  assert(Decl);
  // FIXME: What is the design on getTagDeclType when it requires casting
  // away const?  mutable?
  return getTypeDeclType(const_cast<TagDecl*>(Decl));
}

/// getSizeType - Return the unique type for "size_t" (C99 7.17), the result
/// of the sizeof operator (C99 6.5.3.4p4). The value is target dependent and
/// needs to agree with the definition in <stddef.h>.
CanQualType ASTContext::getSizeType() const {
  return getFromTargetType(Target->getSizeType());
}

/// Return the unique signed counterpart of the integer type
/// corresponding to size_t.
CanQualType ASTContext::getSignedSizeType() const {
  return getFromTargetType(Target->getSignedSizeType());
}

/// getIntMaxType - Return the unique type for "intmax_t" (C99 7.18.1.5).
CanQualType ASTContext::getIntMaxType() const {
  return getFromTargetType(Target->getIntMaxType());
}

/// getUIntMaxType - Return the unique type for "uintmax_t" (C99 7.18.1.5).
CanQualType ASTContext::getUIntMaxType() const {
  return getFromTargetType(Target->getUIntMaxType());
}

/// getSignedWCharType - Return the type of "signed wchar_t".
/// Used when in C++, as a GCC extension.
QualType ASTContext::getSignedWCharType() const {
  // FIXME: derive from "Target" ?
  return WCharTy;
}

/// getUnsignedWCharType - Return the type of "unsigned wchar_t".
/// Used when in C++, as a GCC extension.
QualType ASTContext::getUnsignedWCharType() const {
  // FIXME: derive from "Target" ?
  return UnsignedIntTy;
}

QualType ASTContext::getIntPtrType() const {
  return getFromTargetType(Target->getIntPtrType());
}

QualType ASTContext::getUIntPtrType() const {
  return getCorrespondingUnsignedType(getIntPtrType());
}

/// getPointerDiffType - Return the unique type for "ptrdiff_t" (C99 7.17)
/// defined in <stddef.h>. Pointer - pointer requires this (C99 6.5.6p9).
QualType ASTContext::getPointerDiffType() const {
  return getFromTargetType(Target->getPtrDiffType(0));
}

/// Return the unique unsigned counterpart of "ptrdiff_t"
/// integer type. The standard (C11 7.21.6.1p7) refers to this type
/// in the definition of %tu format specifier.
QualType ASTContext::getUnsignedPointerDiffType() const {
  return getFromTargetType(Target->getUnsignedPtrDiffType(0));
}

/// Return the unique type for "pid_t" defined in
/// <sys/types.h>. We need this to compute the correct type for vfork().
QualType ASTContext::getProcessIDType() const {
  return getFromTargetType(Target->getProcessIDType());
}

//===----------------------------------------------------------------------===//
//                              Type Operators
//===----------------------------------------------------------------------===//

CanQualType ASTContext::getCanonicalParamType(QualType T) const {
  // Push qualifiers into arrays, and then discard any remaining
  // qualifiers.
  T = getCanonicalType(T);
  T = getVariableArrayDecayedType(T);
  const Type *Ty = T.getTypePtr();
  QualType Result;
  if (isa<ArrayType>(Ty)) {
    Result = getArrayDecayedType(QualType(Ty,0));
  } else if (isa<FunctionType>(Ty)) {
    Result = getPointerType(QualType(Ty, 0));
  } else {
    Result = QualType(Ty, 0);
  }

  return CanQualType::CreateUnsafe(Result);
}

QualType ASTContext::getUnqualifiedArrayType(QualType type,
                                             Qualifiers &quals) {
  SplitQualType splitType = type.getSplitUnqualifiedType();

  // FIXME: getSplitUnqualifiedType() actually walks all the way to
  // the unqualified desugared type and then drops it on the floor.
  // We then have to strip that sugar back off with
  // getUnqualifiedDesugaredType(), which is silly.
  const auto *AT =
      dyn_cast<ArrayType>(splitType.Ty->getUnqualifiedDesugaredType());

  // If we don't have an array, just use the results in splitType.
  if (!AT) {
    quals = splitType.Quals;
    return QualType(splitType.Ty, 0);
  }

  // Otherwise, recurse on the array's element type.
  QualType elementType = AT->getElementType();
  QualType unqualElementType = getUnqualifiedArrayType(elementType, quals);

  // If that didn't change the element type, AT has no qualifiers, so we
  // can just use the results in splitType.
  if (elementType == unqualElementType) {
    assert(quals.empty()); // from the recursive call
    quals = splitType.Quals;
    return QualType(splitType.Ty, 0);
  }

  // Otherwise, add in the qualifiers from the outermost type, then
  // build the type back up.
  quals.addConsistentQualifiers(splitType.Quals);

  if (const auto *CAT = dyn_cast<ConstantArrayType>(AT)) {
    return getConstantArrayType(unqualElementType, CAT->getSize(),
                                CAT->getSizeExpr(), CAT->getSizeModifier(), 0);
  }

  if (const auto *IAT = dyn_cast<IncompleteArrayType>(AT)) {
    return getIncompleteArrayType(unqualElementType, IAT->getSizeModifier(), 0);
  }

  if (const auto *VAT = dyn_cast<VariableArrayType>(AT)) {
    return getVariableArrayType(unqualElementType,
                                VAT->getSizeExpr(),
                                VAT->getSizeModifier(),
                                VAT->getIndexTypeCVRQualifiers(),
                                VAT->getBracketsRange());
  }

  const auto *DSAT = cast<DependentSizedArrayType>(AT);
  return getDependentSizedArrayType(unqualElementType, DSAT->getSizeExpr(),
                                    DSAT->getSizeModifier(), 0,
                                    SourceRange());
}

/// Attempt to unwrap two types that may both be array types with the same bound
/// (or both be array types of unknown bound) for the purpose of comparing the
/// cv-decomposition of two types per C++ [conv.qual].
bool ASTContext::UnwrapSimilarArrayTypes(QualType &T1, QualType &T2) {
  bool UnwrappedAny = false;
  while (true) {
    auto *AT1 = getAsArrayType(T1);
    if (!AT1) return UnwrappedAny;

    auto *AT2 = getAsArrayType(T2);
    if (!AT2) return UnwrappedAny;

    // If we don't have two array types with the same constant bound nor two
    // incomplete array types, we've unwrapped everything we can.
    if (auto *CAT1 = dyn_cast<ConstantArrayType>(AT1)) {
      auto *CAT2 = dyn_cast<ConstantArrayType>(AT2);
      if (!CAT2 || CAT1->getSize() != CAT2->getSize())
        return UnwrappedAny;
    } else if (!isa<IncompleteArrayType>(AT1) ||
               !isa<IncompleteArrayType>(AT2)) {
      return UnwrappedAny;
    }

    T1 = AT1->getElementType();
    T2 = AT2->getElementType();
    UnwrappedAny = true;
  }
}

/// Attempt to unwrap two types that may be similar (C++ [conv.qual]).
///
/// If T1 and T2 are both pointer types of the same kind, or both array types
/// with the same bound, unwraps layers from T1 and T2 until a pointer type is
/// unwrapped. Top-level qualifiers on T1 and T2 are ignored.
///
/// This function will typically be called in a loop that successively
/// "unwraps" pointer and pointer-to-member types to compare them at each
/// level.
///
/// \return \c true if a pointer type was unwrapped, \c false if we reached a
/// pair of types that can't be unwrapped further.
bool ASTContext::UnwrapSimilarTypes(QualType &T1, QualType &T2) {
  UnwrapSimilarArrayTypes(T1, T2);

  const auto *T1PtrType = T1->getAs<PointerType>();
  const auto *T2PtrType = T2->getAs<PointerType>();
  if (T1PtrType && T2PtrType) {
    T1 = T1PtrType->getPointeeType();
    T2 = T2PtrType->getPointeeType();
    return true;
  }

  const auto *T1MPType = T1->getAs<MemberPointerType>();
  const auto *T2MPType = T2->getAs<MemberPointerType>();
  if (T1MPType && T2MPType &&
      hasSameUnqualifiedType(QualType(T1MPType->getClass(), 0),
                             QualType(T2MPType->getClass(), 0))) {
    T1 = T1MPType->getPointeeType();
    T2 = T2MPType->getPointeeType();
    return true;
  }

  if (getLangOpts().ObjC) {
    const auto *T1OPType = T1->getAs<ObjCObjectPointerType>();
    const auto *T2OPType = T2->getAs<ObjCObjectPointerType>();
    if (T1OPType && T2OPType) {
      T1 = T1OPType->getPointeeType();
      T2 = T2OPType->getPointeeType();
      return true;
    }
  }

  // FIXME: Block pointers, too?

  return false;
}

bool ASTContext::hasSimilarType(QualType T1, QualType T2) {
  while (true) {
    Qualifiers Quals;
    T1 = getUnqualifiedArrayType(T1, Quals);
    T2 = getUnqualifiedArrayType(T2, Quals);
    if (hasSameType(T1, T2))
      return true;
    if (!UnwrapSimilarTypes(T1, T2))
      return false;
  }
}

bool ASTContext::hasCvrSimilarType(QualType T1, QualType T2) {
  while (true) {
    Qualifiers Quals1, Quals2;
    T1 = getUnqualifiedArrayType(T1, Quals1);
    T2 = getUnqualifiedArrayType(T2, Quals2);

    Quals1.removeCVRQualifiers();
    Quals2.removeCVRQualifiers();
    if (Quals1 != Quals2)
      return false;

    if (hasSameType(T1, T2))
      return true;

    if (!UnwrapSimilarTypes(T1, T2))
      return false;
  }
}

DeclarationNameInfo
ASTContext::getNameForTemplate(TemplateName Name,
                               SourceLocation NameLoc) const {
  switch (Name.getKind()) {
  case TemplateName::QualifiedTemplate:
  case TemplateName::Template:
    // DNInfo work in progress: CHECKME: what about DNLoc?
    return DeclarationNameInfo(Name.getAsTemplateDecl()->getDeclName(),
                               NameLoc);

  case TemplateName::OverloadedTemplate: {
    OverloadedTemplateStorage *Storage = Name.getAsOverloadedTemplate();
    // DNInfo work in progress: CHECKME: what about DNLoc?
    return DeclarationNameInfo((*Storage->begin())->getDeclName(), NameLoc);
  }

  case TemplateName::AssumedTemplate: {
    AssumedTemplateStorage *Storage = Name.getAsAssumedTemplateName();
    return DeclarationNameInfo(Storage->getDeclName(), NameLoc);
  }

  case TemplateName::DependentTemplate: {
    DependentTemplateName *DTN = Name.getAsDependentTemplateName();
    DeclarationName DName;
    if (DTN->isIdentifier()) {
      DName = DeclarationNames.getIdentifier(DTN->getIdentifier());
      return DeclarationNameInfo(DName, NameLoc);
    } else {
      DName = DeclarationNames.getCXXOperatorName(DTN->getOperator());
      // DNInfo work in progress: FIXME: source locations?
      DeclarationNameLoc DNLoc;
      DNLoc.CXXOperatorName.BeginOpNameLoc = SourceLocation().getRawEncoding();
      DNLoc.CXXOperatorName.EndOpNameLoc = SourceLocation().getRawEncoding();
      return DeclarationNameInfo(DName, NameLoc, DNLoc);
    }
  }

  case TemplateName::SubstTemplateTemplateParm: {
    SubstTemplateTemplateParmStorage *subst
      = Name.getAsSubstTemplateTemplateParm();
    return DeclarationNameInfo(subst->getParameter()->getDeclName(),
                               NameLoc);
  }

  case TemplateName::SubstTemplateTemplateParmPack: {
    SubstTemplateTemplateParmPackStorage *subst
      = Name.getAsSubstTemplateTemplateParmPack();
    return DeclarationNameInfo(subst->getParameterPack()->getDeclName(),
                               NameLoc);
  }
  }

  llvm_unreachable("bad template name kind!");
}

TemplateName ASTContext::getCanonicalTemplateName(TemplateName Name) const {
  switch (Name.getKind()) {
  case TemplateName::QualifiedTemplate:
  case TemplateName::Template: {
    TemplateDecl *Template = Name.getAsTemplateDecl();
    if (auto *TTP  = dyn_cast<TemplateTemplateParmDecl>(Template))
      Template = getCanonicalTemplateTemplateParmDecl(TTP);

    // The canonical template name is the canonical template declaration.
    return TemplateName(cast<TemplateDecl>(Template->getCanonicalDecl()));
  }

  case TemplateName::OverloadedTemplate:
  case TemplateName::AssumedTemplate:
    llvm_unreachable("cannot canonicalize unresolved template");

  case TemplateName::DependentTemplate: {
    DependentTemplateName *DTN = Name.getAsDependentTemplateName();
    assert(DTN && "Non-dependent template names must refer to template decls.");
    return DTN->CanonicalTemplateName;
  }

  case TemplateName::SubstTemplateTemplateParm: {
    SubstTemplateTemplateParmStorage *subst
      = Name.getAsSubstTemplateTemplateParm();
    return getCanonicalTemplateName(subst->getReplacement());
  }

  case TemplateName::SubstTemplateTemplateParmPack: {
    SubstTemplateTemplateParmPackStorage *subst
                                  = Name.getAsSubstTemplateTemplateParmPack();
    TemplateTemplateParmDecl *canonParameter
      = getCanonicalTemplateTemplateParmDecl(subst->getParameterPack());
    TemplateArgument canonArgPack
      = getCanonicalTemplateArgument(subst->getArgumentPack());
    return getSubstTemplateTemplateParmPack(canonParameter, canonArgPack);
  }
  }

  llvm_unreachable("bad template name!");
}

bool ASTContext::hasSameTemplateName(TemplateName X, TemplateName Y) {
  X = getCanonicalTemplateName(X);
  Y = getCanonicalTemplateName(Y);
  return X.getAsVoidPointer() == Y.getAsVoidPointer();
}

TemplateArgument
ASTContext::getCanonicalTemplateArgument(const TemplateArgument &Arg) const {
  switch (Arg.getKind()) {
    case TemplateArgument::Null:
      return Arg;

    case TemplateArgument::Expression:
      return Arg;

    case TemplateArgument::Declaration: {
      auto *D = cast<ValueDecl>(Arg.getAsDecl()->getCanonicalDecl());
      return TemplateArgument(D, Arg.getParamTypeForDecl());
    }

    case TemplateArgument::NullPtr:
      return TemplateArgument(getCanonicalType(Arg.getNullPtrType()),
                              /*isNullPtr*/true);

    case TemplateArgument::Template:
      return TemplateArgument(getCanonicalTemplateName(Arg.getAsTemplate()));

    case TemplateArgument::TemplateExpansion:
      return TemplateArgument(getCanonicalTemplateName(
                                         Arg.getAsTemplateOrTemplatePattern()),
                              Arg.getNumTemplateExpansions());

    case TemplateArgument::Integral:
      return TemplateArgument(Arg, getCanonicalType(Arg.getIntegralType()));

    case TemplateArgument::Type:
      return TemplateArgument(getCanonicalType(Arg.getAsType()));

    case TemplateArgument::Pack: {
      if (Arg.pack_size() == 0)
        return Arg;

      auto *CanonArgs = new (*this) TemplateArgument[Arg.pack_size()];
      unsigned Idx = 0;
      for (TemplateArgument::pack_iterator A = Arg.pack_begin(),
                                        AEnd = Arg.pack_end();
           A != AEnd; (void)++A, ++Idx)
        CanonArgs[Idx] = getCanonicalTemplateArgument(*A);

      return TemplateArgument(llvm::makeArrayRef(CanonArgs, Arg.pack_size()));
    }
  }

  // Silence GCC warning
  llvm_unreachable("Unhandled template argument kind");
}

NestedNameSpecifier *
ASTContext::getCanonicalNestedNameSpecifier(NestedNameSpecifier *NNS) const {
  if (!NNS)
    return nullptr;

  switch (NNS->getKind()) {
  case NestedNameSpecifier::Identifier:
    // Canonicalize the prefix but keep the identifier the same.
    return NestedNameSpecifier::Create(*this,
                         getCanonicalNestedNameSpecifier(NNS->getPrefix()),
                                       NNS->getAsIdentifier());

  case NestedNameSpecifier::Namespace:
    // A namespace is canonical; build a nested-name-specifier with
    // this namespace and no prefix.
    return NestedNameSpecifier::Create(*this, nullptr,
                                 NNS->getAsNamespace()->getOriginalNamespace());

  case NestedNameSpecifier::NamespaceAlias:
    // A namespace is canonical; build a nested-name-specifier with
    // this namespace and no prefix.
    return NestedNameSpecifier::Create(*this, nullptr,
                                    NNS->getAsNamespaceAlias()->getNamespace()
                                                      ->getOriginalNamespace());

  case NestedNameSpecifier::TypeSpec:
  case NestedNameSpecifier::TypeSpecWithTemplate: {
    QualType T = getCanonicalType(QualType(NNS->getAsType(), 0));

    // If we have some kind of dependent-named type (e.g., "typename T::type"),
    // break it apart into its prefix and identifier, then reconsititute those
    // as the canonical nested-name-specifier. This is required to canonicalize
    // a dependent nested-name-specifier involving typedefs of dependent-name
    // types, e.g.,
    //   typedef typename T::type T1;
    //   typedef typename T1::type T2;
    if (const auto *DNT = T->getAs<DependentNameType>())
      return NestedNameSpecifier::Create(*this, DNT->getQualifier(),
                           const_cast<IdentifierInfo *>(DNT->getIdentifier()));

    // Otherwise, just canonicalize the type, and force it to be a TypeSpec.
    // FIXME: Why are TypeSpec and TypeSpecWithTemplate distinct in the
    // first place?
    return NestedNameSpecifier::Create(*this, nullptr, false,
                                       const_cast<Type *>(T.getTypePtr()));
  }

  case