/usr/src/gnu/usr.bin/clang/libclangSema/../../../llvm/clang/lib/Sema/SemaLookup.cpp

Bug Summary

File:	src/gnu/usr.bin/clang/libclangSema/../../../llvm/clang/lib/Sema/SemaLookup.cpp
Warning:	line 108, column 38 Called C++ object pointer is null
Annotated Source Code

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clang -cc1 -cc1 -triple amd64-unknown-openbsd7.0 -analyze -disable-free -disable-llvm-verifier -discard-value-names -main-file-name SemaLookup.cpp -analyzer-store=region -analyzer-opt-analyze-nested-blocks -analyzer-checker=core -analyzer-checker=apiModeling -analyzer-checker=unix -analyzer-checker=deadcode -analyzer-checker=cplusplus -analyzer-checker=security.insecureAPI.UncheckedReturn -analyzer-checker=security.insecureAPI.getpw -analyzer-checker=security.insecureAPI.gets -analyzer-checker=security.insecureAPI.mktemp -analyzer-checker=security.insecureAPI.mkstemp -analyzer-checker=security.insecureAPI.vfork -analyzer-checker=nullability.NullPassedToNonnull -analyzer-checker=nullability.NullReturnedFromNonnull -analyzer-output plist -w -setup-static-analyzer -mrelocation-model static -mframe-pointer=all -relaxed-aliasing -fno-rounding-math -mconstructor-aliases -munwind-tables -target-cpu x86-64 -tune-cpu generic -debugger-tuning=gdb -fcoverage-compilation-dir=/usr/src/gnu/usr.bin/clang/libclangSema/obj -resource-dir /usr/local/lib/clang/13.0.0 -I /usr/src/gnu/usr.bin/clang/libclangSema/obj/../include/clang/Sema -I /usr/src/gnu/usr.bin/clang/libclangSema/../../../llvm/clang/include -I /usr/src/gnu/usr.bin/clang/libclangSema/../../../llvm/llvm/include -I /usr/src/gnu/usr.bin/clang/libclangSema/../include -I /usr/src/gnu/usr.bin/clang/libclangSema/obj -I /usr/src/gnu/usr.bin/clang/libclangSema/obj/../include -D NDEBUG -D __STDC_LIMIT_MACROS -D __STDC_CONSTANT_MACROS -D __STDC_FORMAT_MACROS -D LLVM_PREFIX="/usr" -internal-isystem /usr/include/c++/v1 -internal-isystem /usr/local/lib/clang/13.0.0/include -internal-externc-isystem /usr/include -O2 -Wno-unused-parameter -Wwrite-strings -Wno-missing-field-initializers -Wno-long-long -Wno-comment -std=c++14 -fdeprecated-macro -fdebug-compilation-dir=/usr/src/gnu/usr.bin/clang/libclangSema/obj -ferror-limit 19 -fvisibility-inlines-hidden -fwrapv -stack-protector 2 -fno-rtti -fgnuc-version=4.2.1 -vectorize-loops -vectorize-slp -fno-builtin-malloc -fno-builtin-calloc -fno-builtin-realloc -fno-builtin-valloc -fno-builtin-free -fno-builtin-strdup -fno-builtin-strndup -analyzer-output=html -faddrsig -D__GCC_HAVE_DWARF2_CFI_ASM=1 -o /home/ben/Projects/vmm/scan-build/2022-01-12-194120-40624-1 -x c++ /usr/src/gnu/usr.bin/clang/libclangSema/../../../llvm/clang/lib/Sema/SemaLookup.cpp
1//===--------------------- SemaLookup.cpp - Name Lookup  ------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9//  This file implements name lookup for C, C++, Objective-C, and
10//  Objective-C++.
11//
12//===----------------------------------------------------------------------===//

14#include "clang/AST/ASTContext.h"
15#include "clang/AST/CXXInheritance.h"
16#include "clang/AST/Decl.h"
17#include "clang/AST/DeclCXX.h"
18#include "clang/AST/DeclLookups.h"
19#include "clang/AST/DeclObjC.h"
20#include "clang/AST/DeclTemplate.h"
21#include "clang/AST/Expr.h"
22#include "clang/AST/ExprCXX.h"
23#include "clang/Basic/Builtins.h"
24#include "clang/Basic/FileManager.h"
25#include "clang/Basic/LangOptions.h"
26#include "clang/Lex/HeaderSearch.h"
27#include "clang/Lex/ModuleLoader.h"
28#include "clang/Lex/Preprocessor.h"
29#include "clang/Sema/DeclSpec.h"
30#include "clang/Sema/Lookup.h"
31#include "clang/Sema/Overload.h"
32#include "clang/Sema/Scope.h"
33#include "clang/Sema/ScopeInfo.h"
34#include "clang/Sema/Sema.h"
35#include "clang/Sema/SemaInternal.h"
36#include "clang/Sema/TemplateDeduction.h"
37#include "clang/Sema/TypoCorrection.h"
38#include "llvm/ADT/STLExtras.h"
39#include "llvm/ADT/SmallPtrSet.h"
40#include "llvm/ADT/TinyPtrVector.h"
41#include "llvm/ADT/edit_distance.h"
42#include "llvm/Support/ErrorHandling.h"
43#include <algorithm>
44#include <iterator>
45#include <list>
46#include <set>
47#include <utility>
48#include <vector>

50#include "OpenCLBuiltins.inc"

52using namespace clang;
53using namespace sema;

55namespace {
class UnqualUsingEntry {
  const DeclContext *Nominated;
  const DeclContext *CommonAncestor;

public:
  UnqualUsingEntry(const DeclContext *Nominated,
                   const DeclContext *CommonAncestor)
    : Nominated(Nominated), CommonAncestor(CommonAncestor) {
  }

  const DeclContext *getCommonAncestor() const {
    return CommonAncestor;
  }

  const DeclContext *getNominatedNamespace() const {
    return Nominated;
  }

  // Sort by the pointer value of the common ancestor.
  struct Comparator {
    bool operator()(const UnqualUsingEntry &L, const UnqualUsingEntry &R) {
      return L.getCommonAncestor() < R.getCommonAncestor();
    }

    bool operator()(const UnqualUsingEntry &E, const DeclContext *DC) {
      return E.getCommonAncestor() < DC;
    }

    bool operator()(const DeclContext *DC, const UnqualUsingEntry &E) {
      return DC < E.getCommonAncestor();
    }
  };
};

/// A collection of using directives, as used by C++ unqualified
/// lookup.
class UnqualUsingDirectiveSet {
  Sema &SemaRef;

  typedef SmallVector<UnqualUsingEntry, 8> ListTy;

  ListTy list;
  llvm::SmallPtrSet<DeclContext*, 8> visited;

public:
  UnqualUsingDirectiveSet(Sema &SemaRef) : SemaRef(SemaRef) {}

  void visitScopeChain(Scope *S, Scope *InnermostFileScope) {
    // C++ [namespace.udir]p1:
    //   During unqualified name lookup, the names appear as if they
    //   were declared in the nearest enclosing namespace which contains
    //   both the using-directive and the nominated namespace.
    DeclContext *InnermostFileDC = InnermostFileScope->getEntity();
8
←
Called C++ object pointer is null
    assert(InnermostFileDC && InnermostFileDC->isFileContext())((void)0);

    for (; S; S = S->getParent()) {
      // C++ [namespace.udir]p1:
      //   A using-directive shall not appear in class scope, but may
      //   appear in namespace scope or in block scope.
      DeclContext *Ctx = S->getEntity();
      if (Ctx && Ctx->isFileContext()) {
        visit(Ctx, Ctx);
      } else if (!Ctx || Ctx->isFunctionOrMethod()) {
        for (auto *I : S->using_directives())
          if (SemaRef.isVisible(I))
            visit(I, InnermostFileDC);
      }
    }
  }

  // Visits a context and collect all of its using directives
  // recursively.  Treats all using directives as if they were
  // declared in the context.
  //
  // A given context is only every visited once, so it is important
  // that contexts be visited from the inside out in order to get
  // the effective DCs right.
  void visit(DeclContext *DC, DeclContext *EffectiveDC) {
    if (!visited.insert(DC).second)
      return;

    addUsingDirectives(DC, EffectiveDC);
  }

  // Visits a using directive and collects all of its using
  // directives recursively.  Treats all using directives as if they
  // were declared in the effective DC.
  void visit(UsingDirectiveDecl *UD, DeclContext *EffectiveDC) {
    DeclContext *NS = UD->getNominatedNamespace();
    if (!visited.insert(NS).second)
      return;

    addUsingDirective(UD, EffectiveDC);
    addUsingDirectives(NS, EffectiveDC);
  }

  // Adds all the using directives in a context (and those nominated
  // by its using directives, transitively) as if they appeared in
  // the given effective context.
  void addUsingDirectives(DeclContext *DC, DeclContext *EffectiveDC) {
    SmallVector<DeclContext*, 4> queue;
    while (true) {
      for (auto UD : DC->using_directives()) {
        DeclContext *NS = UD->getNominatedNamespace();
        if (SemaRef.isVisible(UD) && visited.insert(NS).second) {
          addUsingDirective(UD, EffectiveDC);
          queue.push_back(NS);
        }
      }

      if (queue.empty())
        return;

      DC = queue.pop_back_val();
    }
  }

  // Add a using directive as if it had been declared in the given
  // context.  This helps implement C++ [namespace.udir]p3:
  //   The using-directive is transitive: if a scope contains a
  //   using-directive that nominates a second namespace that itself
  //   contains using-directives, the effect is as if the
  //   using-directives from the second namespace also appeared in
  //   the first.
  void addUsingDirective(UsingDirectiveDecl *UD, DeclContext *EffectiveDC) {
    // Find the common ancestor between the effective context and
    // the nominated namespace.
    DeclContext *Common = UD->getNominatedNamespace();
    while (!Common->Encloses(EffectiveDC))
      Common = Common->getParent();
    Common = Common->getPrimaryContext();

    list.push_back(UnqualUsingEntry(UD->getNominatedNamespace(), Common));
  }

  void done() { llvm::sort(list, UnqualUsingEntry::Comparator()); }

  typedef ListTy::const_iterator const_iterator;

  const_iterator begin() const { return list.begin(); }
  const_iterator end() const { return list.end(); }

  llvm::iterator_range<const_iterator>
  getNamespacesFor(DeclContext *DC) const {
    return llvm::make_range(std::equal_range(begin(), end(),
                                             DC->getPrimaryContext(),
                                             UnqualUsingEntry::Comparator()));
  }
};
205} // end anonymous namespace

207// Retrieve the set of identifier namespaces that correspond to a
208// specific kind of name lookup.
209static inline unsigned getIDNS(Sema::LookupNameKind NameKind,
                             bool CPlusPlus,
                             bool Redeclaration) {
unsigned IDNS = 0;
switch (NameKind) {
case Sema::LookupObjCImplicitSelfParam:
case Sema::LookupOrdinaryName:
case Sema::LookupRedeclarationWithLinkage:
case Sema::LookupLocalFriendName:
case Sema::LookupDestructorName:
  IDNS = Decl::IDNS_Ordinary;
  if (CPlusPlus) {
    IDNS |= Decl::IDNS_Tag | Decl::IDNS_Member | Decl::IDNS_Namespace;
    if (Redeclaration)
      IDNS |= Decl::IDNS_TagFriend | Decl::IDNS_OrdinaryFriend;
  }
  if (Redeclaration)
    IDNS |= Decl::IDNS_LocalExtern;
  break;

case Sema::LookupOperatorName:
  // Operator lookup is its own crazy thing;  it is not the same
  // as (e.g.) looking up an operator name for redeclaration.
  assert(!Redeclaration && "cannot do redeclaration operator lookup")((void)0);
  IDNS = Decl::IDNS_NonMemberOperator;
  break;

case Sema::LookupTagName:
  if (CPlusPlus) {
    IDNS = Decl::IDNS_Type;

    // When looking for a redeclaration of a tag name, we add:
    // 1) TagFriend to find undeclared friend decls
    // 2) Namespace because they can't "overload" with tag decls.
    // 3) Tag because it includes class templates, which can't
    //    "overload" with tag decls.
    if (Redeclaration)
      IDNS |= Decl::IDNS_Tag | Decl::IDNS_TagFriend | Decl::IDNS_Namespace;
  } else {
    IDNS = Decl::IDNS_Tag;
  }
  break;

case Sema::LookupLabel:
  IDNS = Decl::IDNS_Label;
  break;

case Sema::LookupMemberName:
  IDNS = Decl::IDNS_Member;
  if (CPlusPlus)
    IDNS |= Decl::IDNS_Tag | Decl::IDNS_Ordinary;
  break;

case Sema::LookupNestedNameSpecifierName:
  IDNS = Decl::IDNS_Type | Decl::IDNS_Namespace;
  break;

case Sema::LookupNamespaceName:
  IDNS = Decl::IDNS_Namespace;
  break;

case Sema::LookupUsingDeclName:
  assert(Redeclaration && "should only be used for redecl lookup")((void)0);
  IDNS = Decl::IDNS_Ordinary | Decl::IDNS_Tag | Decl::IDNS_Member |
         Decl::IDNS_Using | Decl::IDNS_TagFriend | Decl::IDNS_OrdinaryFriend |
         Decl::IDNS_LocalExtern;
  break;

case Sema::LookupObjCProtocolName:
  IDNS = Decl::IDNS_ObjCProtocol;
  break;

case Sema::LookupOMPReductionName:
  IDNS = Decl::IDNS_OMPReduction;
  break;

case Sema::LookupOMPMapperName:
  IDNS = Decl::IDNS_OMPMapper;
  break;

case Sema::LookupAnyName:
  IDNS = Decl::IDNS_Ordinary | Decl::IDNS_Tag | Decl::IDNS_Member
    | Decl::IDNS_Using | Decl::IDNS_Namespace | Decl::IDNS_ObjCProtocol
    | Decl::IDNS_Type;
  break;
}
return IDNS;
296}

298void LookupResult::configure() {
IDNS = getIDNS(LookupKind, getSema().getLangOpts().CPlusPlus,
               isForRedeclaration());

// If we're looking for one of the allocation or deallocation
// operators, make sure that the implicitly-declared new and delete
// operators can be found.
switch (NameInfo.getName().getCXXOverloadedOperator()) {
case OO_New:
case OO_Delete:
case OO_Array_New:
case OO_Array_Delete:
  getSema().DeclareGlobalNewDelete();
  break;

default:
  break;
}

// Compiler builtins are always visible, regardless of where they end
// up being declared.
if (IdentifierInfo *Id = NameInfo.getName().getAsIdentifierInfo()) {
  if (unsigned BuiltinID = Id->getBuiltinID()) {
    if (!getSema().Context.BuiltinInfo.isPredefinedLibFunction(BuiltinID))
      AllowHidden = true;
  }
}
325}

327bool LookupResult::sanity() const {
// This function is never called by NDEBUG builds.
assert(ResultKind != NotFound || Decls.size() == 0)((void)0);
assert(ResultKind != Found || Decls.size() == 1)((void)0);
assert(ResultKind != FoundOverloaded || Decls.size() > 1 ||((void)0)
       (Decls.size() == 1 &&((void)0)
        isa<FunctionTemplateDecl>((*begin())->getUnderlyingDecl())))((void)0);
assert(ResultKind != FoundUnresolvedValue || sanityCheckUnresolved())((void)0);
assert(ResultKind != Ambiguous || Decls.size() > 1 ||((void)0)
       (Decls.size() == 1 && (Ambiguity == AmbiguousBaseSubobjects ||((void)0)
                              Ambiguity == AmbiguousBaseSubobjectTypes)))((void)0);
assert((Paths != nullptr) == (ResultKind == Ambiguous &&((void)0)
                              (Ambiguity == AmbiguousBaseSubobjectTypes ||((void)0)
                               Ambiguity == AmbiguousBaseSubobjects)))((void)0);
return true;
342}

344// Necessary because CXXBasePaths is not complete in Sema.h
345void LookupResult::deletePaths(CXXBasePaths *Paths) {
delete Paths;
347}

349/// Get a representative context for a declaration such that two declarations
350/// will have the same context if they were found within the same scope.
351static DeclContext *getContextForScopeMatching(Decl *D) {
// For function-local declarations, use that function as the context. This
// doesn't account for scopes within the function; the caller must deal with
// those.
DeclContext *DC = D->getLexicalDeclContext();
if (DC->isFunctionOrMethod())
  return DC;

// Otherwise, look at the semantic context of the declaration. The
// declaration must have been found there.
return D->getDeclContext()->getRedeclContext();
362}

364/// Determine whether \p D is a better lookup result than \p Existing,
365/// given that they declare the same entity.
366static bool isPreferredLookupResult(Sema &S, Sema::LookupNameKind Kind,
                                  NamedDecl *D, NamedDecl *Existing) {
// When looking up redeclarations of a using declaration, prefer a using
// shadow declaration over any other declaration of the same entity.
if (Kind == Sema::LookupUsingDeclName && isa<UsingShadowDecl>(D) &&
    !isa<UsingShadowDecl>(Existing))
  return true;

auto *DUnderlying = D->getUnderlyingDecl();
auto *EUnderlying = Existing->getUnderlyingDecl();

// If they have different underlying declarations, prefer a typedef over the
// original type (this happens when two type declarations denote the same
// type), per a generous reading of C++ [dcl.typedef]p3 and p4. The typedef
// might carry additional semantic information, such as an alignment override.
// However, per C++ [dcl.typedef]p5, when looking up a tag name, prefer a tag
// declaration over a typedef. Also prefer a tag over a typedef for
// destructor name lookup because in some contexts we only accept a
// class-name in a destructor declaration.
if (DUnderlying->getCanonicalDecl() != EUnderlying->getCanonicalDecl()) {
  assert(isa<TypeDecl>(DUnderlying) && isa<TypeDecl>(EUnderlying))((void)0);
  bool HaveTag = isa<TagDecl>(EUnderlying);
  bool WantTag =
      Kind == Sema::LookupTagName || Kind == Sema::LookupDestructorName;
  return HaveTag != WantTag;
}

// Pick the function with more default arguments.
// FIXME: In the presence of ambiguous default arguments, we should keep both,
//        so we can diagnose the ambiguity if the default argument is needed.
//        See C++ [over.match.best]p3.
if (auto *DFD = dyn_cast<FunctionDecl>(DUnderlying)) {
  auto *EFD = cast<FunctionDecl>(EUnderlying);
  unsigned DMin = DFD->getMinRequiredArguments();
  unsigned EMin = EFD->getMinRequiredArguments();
  // If D has more default arguments, it is preferred.
  if (DMin != EMin)
    return DMin < EMin;
  // FIXME: When we track visibility for default function arguments, check
  // that we pick the declaration with more visible default arguments.
}

// Pick the template with more default template arguments.
if (auto *DTD = dyn_cast<TemplateDecl>(DUnderlying)) {
  auto *ETD = cast<TemplateDecl>(EUnderlying);
  unsigned DMin = DTD->getTemplateParameters()->getMinRequiredArguments();
  unsigned EMin = ETD->getTemplateParameters()->getMinRequiredArguments();
  // If D has more default arguments, it is preferred. Note that default
  // arguments (and their visibility) is monotonically increasing across the
  // redeclaration chain, so this is a quick proxy for "is more recent".
  if (DMin != EMin)
    return DMin < EMin;
  // If D has more *visible* default arguments, it is preferred. Note, an
  // earlier default argument being visible does not imply that a later
  // default argument is visible, so we can't just check the first one.
  for (unsigned I = DMin, N = DTD->getTemplateParameters()->size();
      I != N; ++I) {
    if (!S.hasVisibleDefaultArgument(
            ETD->getTemplateParameters()->getParam(I)) &&
        S.hasVisibleDefaultArgument(
            DTD->getTemplateParameters()->getParam(I)))
      return true;
  }
}

// VarDecl can have incomplete array types, prefer the one with more complete
// array type.
if (VarDecl *DVD = dyn_cast<VarDecl>(DUnderlying)) {
  VarDecl *EVD = cast<VarDecl>(EUnderlying);
  if (EVD->getType()->isIncompleteType() &&
      !DVD->getType()->isIncompleteType()) {
    // Prefer the decl with a more complete type if visible.
    return S.isVisible(DVD);
  }
  return false; // Avoid picking up a newer decl, just because it was newer.
}

// For most kinds of declaration, it doesn't really matter which one we pick.
if (!isa<FunctionDecl>(DUnderlying) && !isa<VarDecl>(DUnderlying)) {
  // If the existing declaration is hidden, prefer the new one. Otherwise,
  // keep what we've got.
  return !S.isVisible(Existing);
}

// Pick the newer declaration; it might have a more precise type.
for (Decl *Prev = DUnderlying->getPreviousDecl(); Prev;
     Prev = Prev->getPreviousDecl())
  if (Prev == EUnderlying)
    return true;
return false;
456}

458/// Determine whether \p D can hide a tag declaration.
459static bool canHideTag(NamedDecl *D) {
// C++ [basic.scope.declarative]p4:
//   Given a set of declarations in a single declarative region [...]
//   exactly one declaration shall declare a class name or enumeration name
//   that is not a typedef name and the other declarations shall all refer to
//   the same variable, non-static data member, or enumerator, or all refer
//   to functions and function templates; in this case the class name or
//   enumeration name is hidden.
// C++ [basic.scope.hiding]p2:
//   A class name or enumeration name can be hidden by the name of a
//   variable, data member, function, or enumerator declared in the same
//   scope.
// An UnresolvedUsingValueDecl always instantiates to one of these.
D = D->getUnderlyingDecl();
return isa<VarDecl>(D) || isa<EnumConstantDecl>(D) || isa<FunctionDecl>(D) ||
       isa<FunctionTemplateDecl>(D) || isa<FieldDecl>(D) ||
       isa<UnresolvedUsingValueDecl>(D);
476}

478/// Resolves the result kind of this lookup.
479void LookupResult::resolveKind() {
unsigned N = Decls.size();

// Fast case: no possible ambiguity.
if (N == 0) {
  assert(ResultKind == NotFound ||((void)0)
         ResultKind == NotFoundInCurrentInstantiation)((void)0);
  return;
}

// If there's a single decl, we need to examine it to decide what
// kind of lookup this is.
if (N == 1) {
  NamedDecl *D = (*Decls.begin())->getUnderlyingDecl();
  if (isa<FunctionTemplateDecl>(D))
    ResultKind = FoundOverloaded;
  else if (isa<UnresolvedUsingValueDecl>(D))
    ResultKind = FoundUnresolvedValue;
  return;
}

// Don't do any extra resolution if we've already resolved as ambiguous.
if (ResultKind == Ambiguous) return;

llvm::SmallDenseMap<NamedDecl*, unsigned, 16> Unique;
llvm::SmallDenseMap<QualType, unsigned, 16> UniqueTypes;

bool Ambiguous = false;
bool HasTag = false, HasFunction = false;
bool HasFunctionTemplate = false, HasUnresolved = false;
NamedDecl *HasNonFunction = nullptr;

llvm::SmallVector<NamedDecl*, 4> EquivalentNonFunctions;

unsigned UniqueTagIndex = 0;

unsigned I = 0;
while (I < N) {
  NamedDecl *D = Decls[I]->getUnderlyingDecl();
  D = cast<NamedDecl>(D->getCanonicalDecl());

  // Ignore an invalid declaration unless it's the only one left.
  if (D->isInvalidDecl() && !(I == 0 && N == 1)) {
    Decls[I] = Decls[--N];
    continue;
  }

  llvm::Optional<unsigned> ExistingI;

  // Redeclarations of types via typedef can occur both within a scope
  // and, through using declarations and directives, across scopes. There is
  // no ambiguity if they all refer to the same type, so unique based on the
  // canonical type.
  if (TypeDecl *TD = dyn_cast<TypeDecl>(D)) {
    QualType T = getSema().Context.getTypeDeclType(TD);
    auto UniqueResult = UniqueTypes.insert(
        std::make_pair(getSema().Context.getCanonicalType(T), I));
    if (!UniqueResult.second) {
      // The type is not unique.
      ExistingI = UniqueResult.first->second;
    }
  }

  // For non-type declarations, check for a prior lookup result naming this
  // canonical declaration.
  if (!ExistingI) {
    auto UniqueResult = Unique.insert(std::make_pair(D, I));
    if (!UniqueResult.second) {
      // We've seen this entity before.
      ExistingI = UniqueResult.first->second;
    }
  }

  if (ExistingI) {
    // This is not a unique lookup result. Pick one of the results and
    // discard the other.
    if (isPreferredLookupResult(getSema(), getLookupKind(), Decls[I],
                                Decls[*ExistingI]))
      Decls[*ExistingI] = Decls[I];
    Decls[I] = Decls[--N];
    continue;
  }

  // Otherwise, do some decl type analysis and then continue.

  if (isa<UnresolvedUsingValueDecl>(D)) {
    HasUnresolved = true;
  } else if (isa<TagDecl>(D)) {
    if (HasTag)
      Ambiguous = true;
    UniqueTagIndex = I;
    HasTag = true;
  } else if (isa<FunctionTemplateDecl>(D)) {
    HasFunction = true;
    HasFunctionTemplate = true;
  } else if (isa<FunctionDecl>(D)) {
    HasFunction = true;
  } else {
    if (HasNonFunction) {
      // If we're about to create an ambiguity between two declarations that
      // are equivalent, but one is an internal linkage declaration from one
      // module and the other is an internal linkage declaration from another
      // module, just skip it.
      if (getSema().isEquivalentInternalLinkageDeclaration(HasNonFunction,
                                                           D)) {
        EquivalentNonFunctions.push_back(D);
        Decls[I] = Decls[--N];
        continue;
      }

      Ambiguous = true;
    }
    HasNonFunction = D;
  }
  I++;
}

// C++ [basic.scope.hiding]p2:
//   A class name or enumeration name can be hidden by the name of
//   an object, function, or enumerator declared in the same
//   scope. If a class or enumeration name and an object, function,
//   or enumerator are declared in the same scope (in any order)
//   with the same name, the class or enumeration name is hidden
//   wherever the object, function, or enumerator name is visible.
// But it's still an error if there are distinct tag types found,
// even if they're not visible. (ref?)
if (N > 1 && HideTags && HasTag && !Ambiguous &&
    (HasFunction || HasNonFunction || HasUnresolved)) {
  NamedDecl *OtherDecl = Decls[UniqueTagIndex ? 0 : N - 1];
  if (isa<TagDecl>(Decls[UniqueTagIndex]->getUnderlyingDecl()) &&
      getContextForScopeMatching(Decls[UniqueTagIndex])->Equals(
          getContextForScopeMatching(OtherDecl)) &&
      canHideTag(OtherDecl))
    Decls[UniqueTagIndex] = Decls[--N];
  else
    Ambiguous = true;
}

// FIXME: This diagnostic should really be delayed until we're done with
// the lookup result, in case the ambiguity is resolved by the caller.
if (!EquivalentNonFunctions.empty() && !Ambiguous)
  getSema().diagnoseEquivalentInternalLinkageDeclarations(
      getNameLoc(), HasNonFunction, EquivalentNonFunctions);

Decls.set_size(N);

if (HasNonFunction && (HasFunction || HasUnresolved))
  Ambiguous = true;

if (Ambiguous)
  setAmbiguous(LookupResult::AmbiguousReference);
else if (HasUnresolved)
  ResultKind = LookupResult::FoundUnresolvedValue;
else if (N > 1 || HasFunctionTemplate)
  ResultKind = LookupResult::FoundOverloaded;
else
  ResultKind = LookupResult::Found;
636}

638void LookupResult::addDeclsFromBasePaths(const CXXBasePaths &P) {
CXXBasePaths::const_paths_iterator I, E;
for (I = P.begin(), E = P.end(); I != E; ++I)
  for (DeclContext::lookup_iterator DI = I->Decls, DE = DI.end(); DI != DE;
       ++DI)
    addDecl(*DI);
644}

646void LookupResult::setAmbiguousBaseSubobjects(CXXBasePaths &P) {
Paths = new CXXBasePaths;
Paths->swap(P);
addDeclsFromBasePaths(*Paths);
resolveKind();
setAmbiguous(AmbiguousBaseSubobjects);
652}

654void LookupResult::setAmbiguousBaseSubobjectTypes(CXXBasePaths &P) {
Paths = new CXXBasePaths;
Paths->swap(P);
addDeclsFromBasePaths(*Paths);
resolveKind();
setAmbiguous(AmbiguousBaseSubobjectTypes);
660}

662void LookupResult::print(raw_ostream &Out) {
Out << Decls.size() << " result(s)";
if (isAmbiguous()) Out << ", ambiguous";
if (Paths) Out << ", base paths present";

for (iterator I = begin(), E = end(); I != E; ++I) {
  Out << "\n";
  (*I)->print(Out, 2);
}
671}

673LLVM_DUMP_METHOD__attribute__((noinline)) void LookupResult::dump() {
llvm::errs() << "lookup results for " << getLookupName().getAsString()
             << ":\n";
for (NamedDecl *D : *this)
  D->dump();
678}

680/// Diagnose a missing builtin type.
681static QualType diagOpenCLBuiltinTypeError(Sema &S, llvm::StringRef TypeClass,
                                         llvm::StringRef Name) {
S.Diag(SourceLocation(), diag::err_opencl_type_not_found)
    << TypeClass << Name;
return S.Context.VoidTy;
686}

688/// Lookup an OpenCL enum type.
689static QualType getOpenCLEnumType(Sema &S, llvm::StringRef Name) {
LookupResult Result(S, &S.Context.Idents.get(Name), SourceLocation(),
                    Sema::LookupTagName);
S.LookupName(Result, S.TUScope);
if (Result.empty())
  return diagOpenCLBuiltinTypeError(S, "enum", Name);
EnumDecl *Decl = Result.getAsSingle<EnumDecl>();
if (!Decl)
  return diagOpenCLBuiltinTypeError(S, "enum", Name);
return S.Context.getEnumType(Decl);
699}

701/// Lookup an OpenCL typedef type.
702static QualType getOpenCLTypedefType(Sema &S, llvm::StringRef Name) {
LookupResult Result(S, &S.Context.Idents.get(Name), SourceLocation(),
                    Sema::LookupOrdinaryName);
S.LookupName(Result, S.TUScope);
if (Result.empty())
  return diagOpenCLBuiltinTypeError(S, "typedef", Name);
TypedefNameDecl *Decl = Result.getAsSingle<TypedefNameDecl>();
if (!Decl)
  return diagOpenCLBuiltinTypeError(S, "typedef", Name);
return S.Context.getTypedefType(Decl);
712}

714/// Get the QualType instances of the return type and arguments for an OpenCL
715/// builtin function signature.
716/// \param S (in) The Sema instance.
717/// \param OpenCLBuiltin (in) The signature currently handled.
718/// \param GenTypeMaxCnt (out) Maximum number of types contained in a generic
719///        type used as return type or as argument.
720///        Only meaningful for generic types, otherwise equals 1.
721/// \param RetTypes (out) List of the possible return types.
722/// \param ArgTypes (out) List of the possible argument types.  For each
723///        argument, ArgTypes contains QualTypes for the Cartesian product
724///        of (vector sizes) x (types) .
725static void GetQualTypesForOpenCLBuiltin(
  Sema &S, const OpenCLBuiltinStruct &OpenCLBuiltin, unsigned &GenTypeMaxCnt,
  SmallVector<QualType, 1> &RetTypes,
  SmallVector<SmallVector<QualType, 1>, 5> &ArgTypes) {
// Get the QualType instances of the return types.
unsigned Sig = SignatureTable[OpenCLBuiltin.SigTableIndex];
OCL2Qual(S, TypeTable[Sig], RetTypes);
GenTypeMaxCnt = RetTypes.size();

// Get the QualType instances of the arguments.
// First type is the return type, skip it.
for (unsigned Index = 1; Index < OpenCLBuiltin.NumTypes; Index++) {
  SmallVector<QualType, 1> Ty;
  OCL2Qual(S, TypeTable[SignatureTable[OpenCLBuiltin.SigTableIndex + Index]],
           Ty);
  GenTypeMaxCnt = (Ty.size() > GenTypeMaxCnt) ? Ty.size() : GenTypeMaxCnt;
  ArgTypes.push_back(std::move(Ty));
}
743}

745/// Create a list of the candidate function overloads for an OpenCL builtin
746/// function.
747/// \param Context (in) The ASTContext instance.
748/// \param GenTypeMaxCnt (in) Maximum number of types contained in a generic
749///        type used as return type or as argument.
750///        Only meaningful for generic types, otherwise equals 1.
751/// \param FunctionList (out) List of FunctionTypes.
752/// \param RetTypes (in) List of the possible return types.
753/// \param ArgTypes (in) List of the possible types for the arguments.
754static void GetOpenCLBuiltinFctOverloads(
  ASTContext &Context, unsigned GenTypeMaxCnt,
  std::vector<QualType> &FunctionList, SmallVector<QualType, 1> &RetTypes,
  SmallVector<SmallVector<QualType, 1>, 5> &ArgTypes) {
FunctionProtoType::ExtProtoInfo PI(
    Context.getDefaultCallingConvention(false, false, true));
PI.Variadic = false;

// Do not attempt to create any FunctionTypes if there are no return types,
// which happens when a type belongs to a disabled extension.
if (RetTypes.size() == 0)
  return;

// Create FunctionTypes for each (gen)type.
for (unsigned IGenType = 0; IGenType < GenTypeMaxCnt; IGenType++) {
  SmallVector<QualType, 5> ArgList;

  for (unsigned A = 0; A < ArgTypes.size(); A++) {
    // Bail out if there is an argument that has no available types.
    if (ArgTypes[A].size() == 0)
      return;

    // Builtins such as "max" have an "sgentype" argument that represents
    // the corresponding scalar type of a gentype.  The number of gentypes
    // must be a multiple of the number of sgentypes.
    assert(GenTypeMaxCnt % ArgTypes[A].size() == 0 &&((void)0)
           "argument type count not compatible with gentype type count")((void)0);
    unsigned Idx = IGenType % ArgTypes[A].size();
    ArgList.push_back(ArgTypes[A][Idx]);
  }

  FunctionList.push_back(Context.getFunctionType(
      RetTypes[(RetTypes.size() != 1) ? IGenType : 0], ArgList, PI));
}
788}

790/// When trying to resolve a function name, if isOpenCLBuiltin() returns a
791/// non-null <Index, Len> pair, then the name is referencing an OpenCL
792/// builtin function.  Add all candidate signatures to the LookUpResult.
793///
794/// \param S (in) The Sema instance.
795/// \param LR (inout) The LookupResult instance.
796/// \param II (in) The identifier being resolved.
797/// \param FctIndex (in) Starting index in the BuiltinTable.
798/// \param Len (in) The signature list has Len elements.
799static void InsertOCLBuiltinDeclarationsFromTable(Sema &S, LookupResult &LR,
                                                IdentifierInfo *II,
                                                const unsigned FctIndex,
                                                const unsigned Len) {
// The builtin function declaration uses generic types (gentype).
bool HasGenType = false;

// Maximum number of types contained in a generic type used as return type or
// as argument.  Only meaningful for generic types, otherwise equals 1.
unsigned GenTypeMaxCnt;

ASTContext &Context = S.Context;

for (unsigned SignatureIndex = 0; SignatureIndex < Len; SignatureIndex++) {
  const OpenCLBuiltinStruct &OpenCLBuiltin =
      BuiltinTable[FctIndex + SignatureIndex];

  // Ignore this builtin function if it is not available in the currently
  // selected language version.
  if (!isOpenCLVersionContainedInMask(Context.getLangOpts(),
                                      OpenCLBuiltin.Versions))
    continue;

  // Ignore this builtin function if it carries an extension macro that is
  // not defined. This indicates that the extension is not supported by the
  // target, so the builtin function should not be available.
  StringRef Extensions = FunctionExtensionTable[OpenCLBuiltin.Extension];
  if (!Extensions.empty()) {
    SmallVector<StringRef, 2> ExtVec;
    Extensions.split(ExtVec, " ");
    bool AllExtensionsDefined = true;
    for (StringRef Ext : ExtVec) {
      if (!S.getPreprocessor().isMacroDefined(Ext)) {
        AllExtensionsDefined = false;
        break;
      }
    }
    if (!AllExtensionsDefined)
      continue;
  }

  SmallVector<QualType, 1> RetTypes;
  SmallVector<SmallVector<QualType, 1>, 5> ArgTypes;

  // Obtain QualType lists for the function signature.
  GetQualTypesForOpenCLBuiltin(S, OpenCLBuiltin, GenTypeMaxCnt, RetTypes,
                               ArgTypes);
  if (GenTypeMaxCnt > 1) {
    HasGenType = true;
  }

  // Create function overload for each type combination.
  std::vector<QualType> FunctionList;
  GetOpenCLBuiltinFctOverloads(Context, GenTypeMaxCnt, FunctionList, RetTypes,
                               ArgTypes);

  SourceLocation Loc = LR.getNameLoc();
  DeclContext *Parent = Context.getTranslationUnitDecl();
  FunctionDecl *NewOpenCLBuiltin;

  for (const auto &FTy : FunctionList) {
    NewOpenCLBuiltin = FunctionDecl::Create(
        Context, Parent, Loc, Loc, II, FTy, /*TInfo=*/nullptr, SC_Extern,
        false, FTy->isFunctionProtoType());
    NewOpenCLBuiltin->setImplicit();

    // Create Decl objects for each parameter, adding them to the
    // FunctionDecl.
    const auto *FP = cast<FunctionProtoType>(FTy);
    SmallVector<ParmVarDecl *, 4> ParmList;
    for (unsigned IParm = 0, e = FP->getNumParams(); IParm != e; ++IParm) {
      ParmVarDecl *Parm = ParmVarDecl::Create(
          Context, NewOpenCLBuiltin, SourceLocation(), SourceLocation(),
          nullptr, FP->getParamType(IParm), nullptr, SC_None, nullptr);
      Parm->setScopeInfo(0, IParm);
      ParmList.push_back(Parm);
    }
    NewOpenCLBuiltin->setParams(ParmList);

    // Add function attributes.
    if (OpenCLBuiltin.IsPure)
      NewOpenCLBuiltin->addAttr(PureAttr::CreateImplicit(Context));
    if (OpenCLBuiltin.IsConst)
      NewOpenCLBuiltin->addAttr(ConstAttr::CreateImplicit(Context));
    if (OpenCLBuiltin.IsConv)
      NewOpenCLBuiltin->addAttr(ConvergentAttr::CreateImplicit(Context));

    if (!S.getLangOpts().OpenCLCPlusPlus)
      NewOpenCLBuiltin->addAttr(OverloadableAttr::CreateImplicit(Context));

    LR.addDecl(NewOpenCLBuiltin);
  }
}

// If we added overloads, need to resolve the lookup result.
if (Len > 1 || HasGenType)
  LR.resolveKind();
896}

898/// Lookup a builtin function, when name lookup would otherwise
899/// fail.
900bool Sema::LookupBuiltin(LookupResult &R) {
Sema::LookupNameKind NameKind = R.getLookupKind();

// If we didn't find a use of this identifier, and if the identifier
// corresponds to a compiler builtin, create the decl object for the builtin
// now, injecting it into translation unit scope, and return it.
if (NameKind == Sema::LookupOrdinaryName ||
    NameKind == Sema::LookupRedeclarationWithLinkage) {
  IdentifierInfo *II = R.getLookupName().getAsIdentifierInfo();
  if (II) {
    if (getLangOpts().CPlusPlus && NameKind == Sema::LookupOrdinaryName) {
      if (II == getASTContext().getMakeIntegerSeqName()) {
        R.addDecl(getASTContext().getMakeIntegerSeqDecl());
        return true;
      } else if (II == getASTContext().getTypePackElementName()) {
        R.addDecl(getASTContext().getTypePackElementDecl());
        return true;
      }
    }

    // Check if this is an OpenCL Builtin, and if so, insert its overloads.
    if (getLangOpts().OpenCL && getLangOpts().DeclareOpenCLBuiltins) {
      auto Index = isOpenCLBuiltin(II->getName());
      if (Index.first) {
        InsertOCLBuiltinDeclarationsFromTable(*this, R, II, Index.first - 1,
                                              Index.second);
        return true;
      }
    }

    // If this is a builtin on this (or all) targets, create the decl.
    if (unsigned BuiltinID = II->getBuiltinID()) {
      // In C++ and OpenCL (spec v1.2 s6.9.f), we don't have any predefined
      // library functions like 'malloc'. Instead, we'll just error.
      if ((getLangOpts().CPlusPlus || getLangOpts().OpenCL) &&
          Context.BuiltinInfo.isPredefinedLibFunction(BuiltinID))
        return false;

      if (NamedDecl *D =
              LazilyCreateBuiltin(II, BuiltinID, TUScope,
                                  R.isForRedeclaration(), R.getNameLoc())) {
        R.addDecl(D);
        return true;
      }
    }
  }
}

return false;
949}

951/// Looks up the declaration of "struct objc_super" and
952/// saves it for later use in building builtin declaration of
953/// objc_msgSendSuper and objc_msgSendSuper_stret.
954static void LookupPredefedObjCSuperType(Sema &Sema, Scope *S) {
ASTContext &Context = Sema.Context;
LookupResult Result(Sema, &Context.Idents.get("objc_super"), SourceLocation(),
                    Sema::LookupTagName);
Sema.LookupName(Result, S);
if (Result.getResultKind() == LookupResult::Found)
  if (const TagDecl *TD = Result.getAsSingle<TagDecl>())
    Context.setObjCSuperType(Context.getTagDeclType(TD));
962}

964void Sema::LookupNecessaryTypesForBuiltin(Scope *S, unsigned ID) {
if (ID == Builtin::BIobjc_msgSendSuper)
  LookupPredefedObjCSuperType(*this, S);
967}

969/// Determine whether we can declare a special member function within
970/// the class at this point.
971static bool CanDeclareSpecialMemberFunction(const CXXRecordDecl *Class) {
// We need to have a definition for the class.
if (!Class->getDefinition() || Class->isDependentContext())
  return false;

// We can't be in the middle of defining the class.
return !Class->isBeingDefined();
978}

980void Sema::ForceDeclarationOfImplicitMembers(CXXRecordDecl *Class) {
if (!CanDeclareSpecialMemberFunction(Class))
  return;

// If the default constructor has not yet been declared, do so now.
if (Class->needsImplicitDefaultConstructor())
  DeclareImplicitDefaultConstructor(Class);

// If the copy constructor has not yet been declared, do so now.
if (Class->needsImplicitCopyConstructor())
  DeclareImplicitCopyConstructor(Class);

// If the copy assignment operator has not yet been declared, do so now.
if (Class->needsImplicitCopyAssignment())
  DeclareImplicitCopyAssignment(Class);

if (getLangOpts().CPlusPlus11) {
  // If the move constructor has not yet been declared, do so now.
  if (Class->needsImplicitMoveConstructor())
    DeclareImplicitMoveConstructor(Class);

  // If the move assignment operator has not yet been declared, do so now.
  if (Class->needsImplicitMoveAssignment())
    DeclareImplicitMoveAssignment(Class);
}

// If the destructor has not yet been declared, do so now.
if (Class->needsImplicitDestructor())
  DeclareImplicitDestructor(Class);
1009}

1011/// Determine whether this is the name of an implicitly-declared
1012/// special member function.
1013static bool isImplicitlyDeclaredMemberFunctionName(DeclarationName Name) {
switch (Name.getNameKind()) {
case DeclarationName::CXXConstructorName:
case DeclarationName::CXXDestructorName:
  return true;

case DeclarationName::CXXOperatorName:
  return Name.getCXXOverloadedOperator() == OO_Equal;

default:
  break;
}

return false;
1027}

1029/// If there are any implicit member functions with the given name
1030/// that need to be declared in the given declaration context, do so.
1031static void DeclareImplicitMemberFunctionsWithName(Sema &S,
                                                 DeclarationName Name,
                                                 SourceLocation Loc,
                                                 const DeclContext *DC) {
if (!DC)
  return;

switch (Name.getNameKind()) {
case DeclarationName::CXXConstructorName:
  if (const CXXRecordDecl *Record = dyn_cast<CXXRecordDecl>(DC))
    if (Record->getDefinition() && CanDeclareSpecialMemberFunction(Record)) {
      CXXRecordDecl *Class = const_cast<CXXRecordDecl *>(Record);
      if (Record->needsImplicitDefaultConstructor())
        S.DeclareImplicitDefaultConstructor(Class);
      if (Record->needsImplicitCopyConstructor())
        S.DeclareImplicitCopyConstructor(Class);
      if (S.getLangOpts().CPlusPlus11 &&
          Record->needsImplicitMoveConstructor())
        S.DeclareImplicitMoveConstructor(Class);
    }
  break;

case DeclarationName::CXXDestructorName:
  if (const CXXRecordDecl *Record = dyn_cast<CXXRecordDecl>(DC))
    if (Record->getDefinition() && Record->needsImplicitDestructor() &&
        CanDeclareSpecialMemberFunction(Record))
      S.DeclareImplicitDestructor(const_cast<CXXRecordDecl *>(Record));
  break;

case DeclarationName::CXXOperatorName:
  if (Name.getCXXOverloadedOperator() != OO_Equal)
    break;

  if (const CXXRecordDecl *Record = dyn_cast<CXXRecordDecl>(DC)) {
    if (Record->getDefinition() && CanDeclareSpecialMemberFunction(Record)) {
      CXXRecordDecl *Class = const_cast<CXXRecordDecl *>(Record);
      if (Record->needsImplicitCopyAssignment())
        S.DeclareImplicitCopyAssignment(Class);
      if (S.getLangOpts().CPlusPlus11 &&
          Record->needsImplicitMoveAssignment())
        S.DeclareImplicitMoveAssignment(Class);
    }
  }
  break;

case DeclarationName::CXXDeductionGuideName:
  S.DeclareImplicitDeductionGuides(Name.getCXXDeductionGuideTemplate(), Loc);
  break;

default:
  break;
}
1083}

1085// Adds all qualifying matches for a name within a decl context to the
1086// given lookup result.  Returns true if any matches were found.
1087static bool LookupDirect(Sema &S, LookupResult &R, const DeclContext *DC) {
bool Found = false;

// Lazily declare C++ special member functions.
if (S.getLangOpts().CPlusPlus)
  DeclareImplicitMemberFunctionsWithName(S, R.getLookupName(), R.getNameLoc(),
                                         DC);

// Perform lookup into this declaration context.
DeclContext::lookup_result DR = DC->lookup(R.getLookupName());
for (NamedDecl *D : DR) {
  if ((D = R.getAcceptableDecl(D))) {
    R.addDecl(D);
    Found = true;
  }
}

if (!Found && DC->isTranslationUnit() && S.LookupBuiltin(R))
  return true;

if (R.getLookupName().getNameKind()
      != DeclarationName::CXXConversionFunctionName ||
    R.getLookupName().getCXXNameType()->isDependentType() ||
    !isa<CXXRecordDecl>(DC))
  return Found;

// C++ [temp.mem]p6:
//   A specialization of a conversion function template is not found by
//   name lookup. Instead, any conversion function templates visible in the
//   context of the use are considered. [...]
const CXXRecordDecl *Record = cast<CXXRecordDecl>(DC);
if (!Record->isCompleteDefinition())
  return Found;

// For conversion operators, 'operator auto' should only match
// 'operator auto'.  Since 'auto' is not a type, it shouldn't be considered
// as a candidate for template substitution.
auto *ContainedDeducedType =
    R.getLookupName().getCXXNameType()->getContainedDeducedType();
if (R.getLookupName().getNameKind() ==
        DeclarationName::CXXConversionFunctionName &&
    ContainedDeducedType && ContainedDeducedType->isUndeducedType())
  return Found;

for (CXXRecordDecl::conversion_iterator U = Record->conversion_begin(),
       UEnd = Record->conversion_end(); U != UEnd; ++U) {
  FunctionTemplateDecl *ConvTemplate = dyn_cast<FunctionTemplateDecl>(*U);
  if (!ConvTemplate)
    continue;

  // When we're performing lookup for the purposes of redeclaration, just
  // add the conversion function template. When we deduce template
  // arguments for specializations, we'll end up unifying the return
  // type of the new declaration with the type of the function template.
  if (R.isForRedeclaration()) {
    R.addDecl(ConvTemplate);
    Found = true;
    continue;
  }

  // C++ [temp.mem]p6:
  //   [...] For each such operator, if argument deduction succeeds
  //   (14.9.2.3), the resulting specialization is used as if found by
  //   name lookup.
  //
  // When referencing a conversion function for any purpose other than
  // a redeclaration (such that we'll be building an expression with the
  // result), perform template argument deduction and place the
  // specialization into the result set. We do this to avoid forcing all
  // callers to perform special deduction for conversion functions.
  TemplateDeductionInfo Info(R.getNameLoc());
  FunctionDecl *Specialization = nullptr;

  const FunctionProtoType *ConvProto
    = ConvTemplate->getTemplatedDecl()->getType()->getAs<FunctionProtoType>();
  assert(ConvProto && "Nonsensical conversion function template type")((void)0);

  // Compute the type of the function that we would expect the conversion
  // function to have, if it were to match the name given.
  // FIXME: Calling convention!
  FunctionProtoType::ExtProtoInfo EPI = ConvProto->getExtProtoInfo();
  EPI.ExtInfo = EPI.ExtInfo.withCallingConv(CC_C);
  EPI.ExceptionSpec = EST_None;
  QualType ExpectedType
    = R.getSema().Context.getFunctionType(R.getLookupName().getCXXNameType(),
                                          None, EPI);

  // Perform template argument deduction against the type that we would
  // expect the function to have.
  if (R.getSema().DeduceTemplateArguments(ConvTemplate, nullptr, ExpectedType,
                                          Specialization, Info)
        == Sema::TDK_Success) {
    R.addDecl(Specialization);
    Found = true;
  }
}

return Found;
1185}

1187// Performs C++ unqualified lookup into the given file context.
1188static bool
1189CppNamespaceLookup(Sema &S, LookupResult &R, ASTContext &Context,
                 DeclContext *NS, UnqualUsingDirectiveSet &UDirs) {

assert(NS && NS->isFileContext() && "CppNamespaceLookup() requires namespace!")((void)0);

// Perform direct name lookup into the LookupCtx.
bool Found = LookupDirect(S, R, NS);

// Perform direct name lookup into the namespaces nominated by the
// using directives whose common ancestor is this namespace.
for (const UnqualUsingEntry &UUE : UDirs.getNamespacesFor(NS))
  if (LookupDirect(S, R, UUE.getNominatedNamespace()))
    Found = true;

R.resolveKind();

return Found;
1206}

1208static bool isNamespaceOrTranslationUnitScope(Scope *S) {
if (DeclContext *Ctx = S->getEntity())
  return Ctx->isFileContext();
return false;
1212}

1214/// Find the outer declaration context from this scope. This indicates the
1215/// context that we should search up to (exclusive) before considering the
1216/// parent of the specified scope.
1217static DeclContext *findOuterContext(Scope *S) {
for (Scope *OuterS = S->getParent(); OuterS; OuterS = OuterS->getParent())
  if (DeclContext *DC = OuterS->getLookupEntity())
    return DC;
return nullptr;
1222}

1224namespace {
1225/// An RAII object to specify that we want to find block scope extern
1226/// declarations.
1227struct FindLocalExternScope {
FindLocalExternScope(LookupResult &R)
    : R(R), OldFindLocalExtern(R.getIdentifierNamespace() &
                               Decl::IDNS_LocalExtern) {
  R.setFindLocalExtern(R.getIdentifierNamespace() &
                       (Decl::IDNS_Ordinary | Decl::IDNS_NonMemberOperator));
}
void restore() {
  R.setFindLocalExtern(OldFindLocalExtern);
}
~FindLocalExternScope() {
  restore();
}
LookupResult &R;
bool OldFindLocalExtern;
1242};
1243} // end anonymous namespace

1245bool Sema::CppLookupName(LookupResult &R, Scope *S) {
assert(getLangOpts().CPlusPlus && "Can perform only C++ lookup")((void)0);

DeclarationName Name = R.getLookupName();
Sema::LookupNameKind NameKind = R.getLookupKind();

// If this is the name of an implicitly-declared special member function,
// go through the scope stack to implicitly declare
if (isImplicitlyDeclaredMemberFunctionName(Name)) {
  for (Scope *PreS = S; PreS; PreS = PreS->getParent())
    if (DeclContext *DC = PreS->getEntity())
      DeclareImplicitMemberFunctionsWithName(*this, Name, R.getNameLoc(), DC);
}

// Implicitly declare member functions with the name we're looking for, if in
// fact we are in a scope where it matters.

Scope *Initial = S;
IdentifierResolver::iterator
  I = IdResolver.begin(Name),
  IEnd = IdResolver.end();

// First we lookup local scope.
// We don't consider using-directives, as per 7.3.4.p1 [namespace.udir]
// ...During unqualified name lookup (3.4.1), the names appear as if
// they were declared in the nearest enclosing namespace which contains
// both the using-directive and the nominated namespace.
// [Note: in this context, "contains" means "contains directly or
// indirectly".
//
// For example:
// namespace A { int i; }
// void foo() {
//   int i;
//   {
//     using namespace A;
//     ++i; // finds local 'i', A::i appears at global scope
//   }
// }
//
UnqualUsingDirectiveSet UDirs(*this);
bool VisitedUsingDirectives = false;
bool LeftStartingScope = false;

// When performing a scope lookup, we want to find local extern decls.
FindLocalExternScope FindLocals(R);

for (; S && !isNamespaceOrTranslationUnitScope(S); S = S->getParent()) {
  bool SearchNamespaceScope = true;
  // Check whether the IdResolver has anything in this scope.
  for (; I != IEnd && S->isDeclScope(*I); ++I) {
    if (NamedDecl *ND = R.getAcceptableDecl(*I)) {
      if (NameKind == LookupRedeclarationWithLinkage &&
          !(*I)->isTemplateParameter()) {
        // If it's a template parameter, we still find it, so we can diagnose
        // the invalid redeclaration.

        // Determine whether this (or a previous) declaration is
        // out-of-scope.
        if (!LeftStartingScope && !Initial->isDeclScope(*I))
          LeftStartingScope = true;

        // If we found something outside of our starting scope that
        // does not have linkage, skip it.
        if (LeftStartingScope && !((*I)->hasLinkage())) {
          R.setShadowed();
          continue;
        }
      } else {
        // We found something in this scope, we should not look at the
        // namespace scope
        SearchNamespaceScope = false;
      }
      R.addDecl(ND);
    }
  }
  if (!SearchNamespaceScope) {
    R.resolveKind();
    if (S->isClassScope())
      if (CXXRecordDecl *Record =
              dyn_cast_or_null<CXXRecordDecl>(S->getEntity()))
        R.setNamingClass(Record);
    return true;
  }

  if (NameKind == LookupLocalFriendName && !S->isClassScope()) {
    // C++11 [class.friend]p11:
    //   If a friend declaration appears in a local class and the name
    //   specified is an unqualified name, a prior declaration is
    //   looked up without considering scopes that are outside the
    //   innermost enclosing non-class scope.
    return false;
  }

  if (DeclContext *Ctx = S->getLookupEntity()) {
    DeclContext *OuterCtx = findOuterContext(S);
    for (; Ctx && !Ctx->Equals(OuterCtx); Ctx = Ctx->getLookupParent()) {
      // We do not directly look into transparent contexts, since
      // those entities will be found in the nearest enclosing
      // non-transparent context.
      if (Ctx->isTransparentContext())
        continue;

      // We do not look directly into function or method contexts,
      // since all of the local variables and parameters of the
      // function/method are present within the Scope.
      if (Ctx->isFunctionOrMethod()) {
        // If we have an Objective-C instance method, look for ivars
        // in the corresponding interface.
        if (ObjCMethodDecl *Method = dyn_cast<ObjCMethodDecl>(Ctx)) {
          if (Method->isInstanceMethod() && Name.getAsIdentifierInfo())
            if (ObjCInterfaceDecl *Class = Method->getClassInterface()) {
              ObjCInterfaceDecl *ClassDeclared;
              if (ObjCIvarDecl *Ivar = Class->lookupInstanceVariable(
                                               Name.getAsIdentifierInfo(),
                                                           ClassDeclared)) {
                if (NamedDecl *ND = R.getAcceptableDecl(Ivar)) {
                  R.addDecl(ND);
                  R.resolveKind();
                  return true;
                }
              }
            }
        }

        continue;
      }

      // If this is a file context, we need to perform unqualified name
      // lookup considering using directives.
      if (Ctx->isFileContext()) {
        // If we haven't handled using directives yet, do so now.
        if (!VisitedUsingDirectives) {
          // Add using directives from this context up to the top level.
          for (DeclContext *UCtx = Ctx; UCtx; UCtx = UCtx->getParent()) {
            if (UCtx->isTransparentContext())
              continue;

            UDirs.visit(UCtx, UCtx);
          }

          // Find the innermost file scope, so we can add using directives
          // from local scopes.
          Scope *InnermostFileScope = S;
          while (InnermostFileScope &&
                 !isNamespaceOrTranslationUnitScope(InnermostFileScope))
            InnermostFileScope = InnermostFileScope->getParent();
          UDirs.visitScopeChain(Initial, InnermostFileScope);

          UDirs.done();

          VisitedUsingDirectives = true;
        }

        if (CppNamespaceLookup(*this, R, Context, Ctx, UDirs)) {
          R.resolveKind();
          return true;
        }

        continue;
      }

      // Perform qualified name lookup into this context.
      // FIXME: In some cases, we know that every name that could be found by
      // this qualified name lookup will also be on the identifier chain. For
      // example, inside a class without any base classes, we never need to
      // perform qualified lookup because all of the members are on top of the
      // identifier chain.
      if (LookupQualifiedName(R, Ctx, /*InUnqualifiedLookup=*/true))
        return true;
    }
  }
}

// Stop if we ran out of scopes.
// FIXME:  This really, really shouldn't be happening.
if (!S) return false;

// If we are looking for members, no need to look into global/namespace scope.
if (NameKind == LookupMemberName)
  return false;

// Collect UsingDirectiveDecls in all scopes, and recursively all
// nominated namespaces by those using-directives.
//
// FIXME: Cache this sorted list in Scope structure, and DeclContext, so we
// don't build it for each lookup!
if (!VisitedUsingDirectives) {
  UDirs.visitScopeChain(Initial, S);
  UDirs.done();
}

// If we're not performing redeclaration lookup, do not look for local
// extern declarations outside of a function scope.
if (!R.isForRedeclaration())
  FindLocals.restore();

// Lookup namespace scope, and global scope.
// Unqualified name lookup in C++ requires looking into scopes
// that aren't strictly lexical, and therefore we walk through the
// context as well as walking through the scopes.
for (; S; S = S->getParent()) {
  // Check whether the IdResolver has anything in this scope.
  bool Found = false;
  for (; I != IEnd && S->isDeclScope(*I); ++I) {
    if (NamedDecl *ND = R.getAcceptableDecl(*I)) {
      // We found something.  Look for anything else in our scope
      // with this same name and in an acceptable identifier
      // namespace, so that we can construct an overload set if we
      // need to.
      Found = true;
      R.addDecl(ND);
    }
  }

  if (Found && S->isTemplateParamScope()) {
    R.resolveKind();
    return true;
  }

  DeclContext *Ctx = S->getLookupEntity();
  if (Ctx) {
    DeclContext *OuterCtx = findOuterContext(S);
    for (; Ctx && !Ctx->Equals(OuterCtx); Ctx = Ctx->getLookupParent()) {
      // We do not directly look into transparent contexts, since
      // those entities will be found in the nearest enclosing
      // non-transparent context.
      if (Ctx->isTransparentContext())
        continue;

      // If we have a context, and it's not a context stashed in the
      // template parameter scope for an out-of-line definition, also
      // look into that context.
      if (!(Found && S->isTemplateParamScope())) {
        assert(Ctx->isFileContext() &&((void)0)
            "We should have been looking only at file context here already.")((void)0);

        // Look into context considering using-directives.
        if (CppNamespaceLookup(*this, R, Context, Ctx, UDirs))
          Found = true;
      }

      if (Found) {
        R.resolveKind();
        return true;
      }

      if (R.isForRedeclaration() && !Ctx->isTransparentContext())
        return false;
    }
  }

  if (R.isForRedeclaration() && Ctx && !Ctx->isTransparentContext())
    return false;
}

return !R.empty();
1502}

1504void Sema::makeMergedDefinitionVisible(NamedDecl *ND) {
if (auto *M = getCurrentModule())
  Context.mergeDefinitionIntoModule(ND, M);
else
  // We're not building a module; just make the definition visible.
  ND->setVisibleDespiteOwningModule();

// If ND is a template declaration, make the template parameters
// visible too. They're not (necessarily) within a mergeable DeclContext.
if (auto *TD = dyn_cast<TemplateDecl>(ND))
  for (auto *Param : *TD->getTemplateParameters())
    makeMergedDefinitionVisible(Param);
1516}

1518/// Find the module in which the given declaration was defined.
1519static Module *getDefiningModule(Sema &S, Decl *Entity) {
if (FunctionDecl *FD = dyn_cast<FunctionDecl>(Entity)) {
  // If this function was instantiated from a template, the defining module is
  // the module containing the pattern.
  if (FunctionDecl *Pattern = FD->getTemplateInstantiationPattern())
    Entity = Pattern;
} else if (CXXRecordDecl *RD = dyn_cast<CXXRecordDecl>(Entity)) {
  if (CXXRecordDecl *Pattern = RD->getTemplateInstantiationPattern())
    Entity = Pattern;
} else if (EnumDecl *ED = dyn_cast<EnumDecl>(Entity)) {
  if (auto *Pattern = ED->getTemplateInstantiationPattern())
    Entity = Pattern;
} else if (VarDecl *VD = dyn_cast<VarDecl>(Entity)) {
  if (VarDecl *Pattern = VD->getTemplateInstantiationPattern())
    Entity = Pattern;
}

// Walk up to the containing context. That might also have been instantiated
// from a template.
DeclContext *Context = Entity->getLexicalDeclContext();
if (Context->isFileContext())
  return S.getOwningModule(Entity);
return getDefiningModule(S, cast<Decl>(Context));
1542}

1544llvm::DenseSet<Module*> &Sema::getLookupModules() {
unsigned N = CodeSynthesisContexts.size();
for (unsigned I = CodeSynthesisContextLookupModules.size();
     I != N; ++I) {
  Module *M = CodeSynthesisContexts[I].Entity ?
              getDefiningModule(*this, CodeSynthesisContexts[I].Entity) :
              nullptr;
  if (M && !LookupModulesCache.insert(M).second)
    M = nullptr;
  CodeSynthesisContextLookupModules.push_back(M);
}
return LookupModulesCache;
1556}

1558/// Determine whether the module M is part of the current module from the
1559/// perspective of a module-private visibility check.
1560static bool isInCurrentModule(const Module *M, const LangOptions &LangOpts) {
// If M is the global module fragment of a module that we've not yet finished
// parsing, then it must be part of the current module.
return M->getTopLevelModuleName() == LangOpts.CurrentModule ||
       (M->Kind == Module::GlobalModuleFragment && !M->Parent);
1565}

1567bool Sema::hasVisibleMergedDefinition(NamedDecl *Def) {
for (const Module *Merged : Context.getModulesWithMergedDefinition(Def))
  if (isModuleVisible(Merged))
    return true;
return false;
1572}

1574bool Sema::hasMergedDefinitionInCurrentModule(NamedDecl *Def) {
for (const Module *Merged : Context.getModulesWithMergedDefinition(Def))
  if (isInCurrentModule(Merged, getLangOpts()))
    return true;
return false;
1579}

1581template<typename ParmDecl>
1582static bool
1583hasVisibleDefaultArgument(Sema &S, const ParmDecl *D,
                        llvm::SmallVectorImpl<Module *> *Modules) {
if (!D->hasDefaultArgument())
  return false;

while (D) {
  auto &DefaultArg = D->getDefaultArgStorage();
  if (!DefaultArg.isInherited() && S.isVisible(D))
    return true;

  if (!DefaultArg.isInherited() && Modules) {
    auto *NonConstD = const_cast<ParmDecl*>(D);
    Modules->push_back(S.getOwningModule(NonConstD));
  }

  // If there was a previous default argument, maybe its parameter is visible.
  D = DefaultArg.getInheritedFrom();
}
return false;
1602}

1604bool Sema::hasVisibleDefaultArgument(const NamedDecl *D,
                                   llvm::SmallVectorImpl<Module *> *Modules) {
if (auto *P = dyn_cast<TemplateTypeParmDecl>(D))
  return ::hasVisibleDefaultArgument(*this, P, Modules);
if (auto *P = dyn_cast<NonTypeTemplateParmDecl>(D))
  return ::hasVisibleDefaultArgument(*this, P, Modules);
return ::hasVisibleDefaultArgument(*this, cast<TemplateTemplateParmDecl>(D),
                                   Modules);
1612}

1614template<typename Filter>
1615static bool hasVisibleDeclarationImpl(Sema &S, const NamedDecl *D,
                                    llvm::SmallVectorImpl<Module *> *Modules,
                                    Filter F) {
bool HasFilteredRedecls = false;

for (auto *Redecl : D->redecls()) {
  auto *R = cast<NamedDecl>(Redecl);
  if (!F(R))
    continue;

  if (S.isVisible(R))
    return true;

  HasFilteredRedecls = true;

  if (Modules)
    Modules->push_back(R->getOwningModule());
}

// Only return false if there is at least one redecl that is not filtered out.
if (HasFilteredRedecls)
  return false;

return true;
1639}

1641bool Sema::hasVisibleExplicitSpecialization(
  const NamedDecl *D, llvm::SmallVectorImpl<Module *> *Modules) {
return hasVisibleDeclarationImpl(*this, D, Modules, [](const NamedDecl *D) {
  if (auto *RD = dyn_cast<CXXRecordDecl>(D))
    return RD->getTemplateSpecializationKind() == TSK_ExplicitSpecialization;
  if (auto *FD = dyn_cast<FunctionDecl>(D))
    return FD->getTemplateSpecializationKind() == TSK_ExplicitSpecialization;
  if (auto *VD = dyn_cast<VarDecl>(D))
    return VD->getTemplateSpecializationKind() == TSK_ExplicitSpecialization;
  llvm_unreachable("unknown explicit specialization kind")__builtin_unreachable();
});
1652}

1654bool Sema::hasVisibleMemberSpecialization(
  const NamedDecl *D, llvm::SmallVectorImpl<Module *> *Modules) {
assert(isa<CXXRecordDecl>(D->getDeclContext()) &&((void)0)
       "not a member specialization")((void)0);
return hasVisibleDeclarationImpl(*this, D, Modules, [](const NamedDecl *D) {
  // If the specialization is declared at namespace scope, then it's a member
  // specialization declaration. If it's lexically inside the class
  // definition then it was instantiated.
  //
  // FIXME: This is a hack. There should be a better way to determine this.
  // FIXME: What about MS-style explicit specializations declared within a
  //        class definition?
  return D->getLexicalDeclContext()->isFileContext();
});
1668}

1670/// Determine whether a declaration is visible to name lookup.
1671///
1672/// This routine determines whether the declaration D is visible in the current
1673/// lookup context, taking into account the current template instantiation
1674/// stack. During template instantiation, a declaration is visible if it is
1675/// visible from a module containing any entity on the template instantiation
1676/// path (by instantiating a template, you allow it to see the declarations that
1677/// your module can see, including those later on in your module).
1678bool LookupResult::isVisibleSlow(Sema &SemaRef, NamedDecl *D) {
assert(!D->isUnconditionallyVisible() &&((void)0)
       "should not call this: not in slow case")((void)0);

Module *DeclModule = SemaRef.getOwningModule(D);
assert(DeclModule && "hidden decl has no owning module")((void)0);

// If the owning module is visible, the decl is visible.
if (SemaRef.isModuleVisible(DeclModule, D->isModulePrivate()))
  return true;

// Determine whether a decl context is a file context for the purpose of
// visibility. This looks through some (export and linkage spec) transparent
// contexts, but not others (enums).
auto IsEffectivelyFileContext = [](const DeclContext *DC) {
  return DC->isFileContext() || isa<LinkageSpecDecl>(DC) ||
         isa<ExportDecl>(DC);
};

// If this declaration is not at namespace scope
// then it is visible if its lexical parent has a visible definition.
DeclContext *DC = D->getLexicalDeclContext();
if (DC && !IsEffectivelyFileContext(DC)) {
  // For a parameter, check whether our current template declaration's
  // lexical context is visible, not whether there's some other visible
  // definition of it, because parameters aren't "within" the definition.
  //
  // In C++ we need to check for a visible definition due to ODR merging,
  // and in C we must not because each declaration of a function gets its own
  // set of declarations for tags in prototype scope.
  bool VisibleWithinParent;
  if (D->isTemplateParameter()) {
    bool SearchDefinitions = true;
    if (const auto *DCD = dyn_cast<Decl>(DC)) {
      if (const auto *TD = DCD->getDescribedTemplate()) {
        TemplateParameterList *TPL = TD->getTemplateParameters();
        auto Index = getDepthAndIndex(D).second;
        SearchDefinitions = Index >= TPL->size() || TPL->getParam(Index) != D;
      }
    }
    if (SearchDefinitions)
      VisibleWithinParent = SemaRef.hasVisibleDefinition(cast<NamedDecl>(DC));
    else
      VisibleWithinParent = isVisible(SemaRef, cast<NamedDecl>(DC));
  } else if (isa<ParmVarDecl>(D) ||
             (isa<FunctionDecl>(DC) && !SemaRef.getLangOpts().CPlusPlus))
    VisibleWithinParent = isVisible(SemaRef, cast<NamedDecl>(DC));
  else if (D->isModulePrivate()) {
    // A module-private declaration is only visible if an enclosing lexical
    // parent was merged with another definition in the current module.
    VisibleWithinParent = false;
    do {
      if (SemaRef.hasMergedDefinitionInCurrentModule(cast<NamedDecl>(DC))) {
        VisibleWithinParent = true;
        break;
      }
      DC = DC->getLexicalParent();
    } while (!IsEffectivelyFileContext(DC));
  } else {
    VisibleWithinParent = SemaRef.hasVisibleDefinition(cast<NamedDecl>(DC));
  }

  if (VisibleWithinParent && SemaRef.CodeSynthesisContexts.empty() &&
      // FIXME: Do something better in this case.
      !SemaRef.getLangOpts().ModulesLocalVisibility) {
    // Cache the fact that this declaration is implicitly visible because
    // its parent has a visible definition.
    D->setVisibleDespiteOwningModule();
  }
  return VisibleWithinParent;
}

return false;
1751}

1753bool Sema::isModuleVisible(const Module *M, bool ModulePrivate) {
// The module might be ordinarily visible. For a module-private query, that
// means it is part of the current module. For any other query, that means it
// is in our visible module set.
if (ModulePrivate) {
  if (isInCurrentModule(M, getLangOpts()))
    return true;
} else {
  if (VisibleModules.isVisible(M))
    return true;
}

// Otherwise, it might be visible by virtue of the query being within a
// template instantiation or similar that is permitted to look inside M.

// Find the extra places where we need to look.
const auto &LookupModules = getLookupModules();
if (LookupModules.empty())
  return false;

// If our lookup set contains the module, it's visible.
if (LookupModules.count(M))
  return true;

// For a module-private query, that's everywhere we get to look.
if (ModulePrivate)
  return false;

// Check whether M is transitively exported to an import of the lookup set.
return llvm::any_of(LookupModules, [&](const Module *LookupM) {
  return LookupM->isModuleVisible(M);
});
1785}

1787bool Sema::isVisibleSlow(const NamedDecl *D) {
return LookupResult::isVisible(*this, const_cast<NamedDecl*>(D));
1789}

1791bool Sema::shouldLinkPossiblyHiddenDecl(LookupResult &R, const NamedDecl *New) {
// FIXME: If there are both visible and hidden declarations, we need to take
// into account whether redeclaration is possible. Example:
//
// Non-imported module:
//   int f(T);        // #1
// Some TU:
//   static int f(U); // #2, not a redeclaration of #1
//   int f(T);        // #3, finds both, should link with #1 if T != U, but
//                    // with #2 if T == U; neither should be ambiguous.
for (auto *D : R) {
  if (isVisible(D))
    return true;
  assert(D->isExternallyDeclarable() &&((void)0)
         "should not have hidden, non-externally-declarable result here")((void)0);
}

// This function is called once "New" is essentially complete, but before a
// previous declaration is attached. We can't query the linkage of "New" in
// general, because attaching the previous declaration can change the
// linkage of New to match the previous declaration.
//
// However, because we've just determined that there is no *visible* prior
// declaration, we can compute the linkage here. There are two possibilities:
//
//  * This is not a redeclaration; it's safe to compute the linkage now.
//
//  * This is a redeclaration of a prior declaration that is externally
//    redeclarable. In that case, the linkage of the declaration is not
//    changed by attaching the prior declaration, because both are externally
//    declarable (and thus ExternalLinkage or VisibleNoLinkage).
//
// FIXME: This is subtle and fragile.
return New->isExternallyDeclarable();
1825}

1827/// Retrieve the visible declaration corresponding to D, if any.
1828///
1829/// This routine determines whether the declaration D is visible in the current
1830/// module, with the current imports. If not, it checks whether any
1831/// redeclaration of D is visible, and if so, returns that declaration.
1832///
1833/// \returns D, or a visible previous declaration of D, whichever is more recent
1834/// and visible. If no declaration of D is visible, returns null.
1835static NamedDecl *findAcceptableDecl(Sema &SemaRef, NamedDecl *D,
                                   unsigned IDNS) {
assert(!LookupResult::isVisible(SemaRef, D) && "not in slow case")((void)0);

for (auto RD : D->redecls()) {
  // Don't bother with extra checks if we already know this one isn't visible.
  if (RD == D)
    continue;

  auto ND = cast<NamedDecl>(RD);
  // FIXME: This is wrong in the case where the previous declaration is not
  // visible in the same scope as D. This needs to be done much more
  // carefully.
  if (ND->isInIdentifierNamespace(IDNS) &&
      LookupResult::isVisible(SemaRef, ND))
    return ND;
}

return nullptr;
1854}

1856bool Sema::hasVisibleDeclarationSlow(const NamedDecl *D,
                                   llvm::SmallVectorImpl<Module *> *Modules) {
assert(!isVisible(D) && "not in slow case")((void)0);
return hasVisibleDeclarationImpl(*this, D, Modules,
                                 [](const NamedDecl *) { return true; });
1861}

1863NamedDecl *LookupResult::getAcceptableDeclSlow(NamedDecl *D) const {
if (auto *ND = dyn_cast<NamespaceDecl>(D)) {
  // Namespaces are a bit of a special case: we expect there to be a lot of
  // redeclarations of some namespaces, all declarations of a namespace are
  // essentially interchangeable, all declarations are found by name lookup
  // if any is, and namespaces are never looked up during template
  // instantiation. So we benefit from caching the check in this case, and
  // it is correct to do so.
  auto *Key = ND->getCanonicalDecl();
  if (auto *Acceptable = getSema().VisibleNamespaceCache.lookup(Key))
    return Acceptable;
  auto *Acceptable = isVisible(getSema(), Key)
                         ? Key
                         : findAcceptableDecl(getSema(), Key, IDNS);
  if (Acceptable)
    getSema().VisibleNamespaceCache.insert(std::make_pair(Key, Acceptable));
  return Acceptable;
}

return findAcceptableDecl(getSema(), D, IDNS);
1883}

1885/// Perform unqualified name lookup starting from a given
1886/// scope.
1887///
1888/// Unqualified name lookup (C++ [basic.lookup.unqual], C99 6.2.1) is
1889/// used to find names within the current scope. For example, 'x' in
1890/// @code
1891/// int x;
1892/// int f() {
1893///   return x; // unqualified name look finds 'x' in the global scope
1894/// }
1895/// @endcode
1896///
1897/// Different lookup criteria can find different names. For example, a
1898/// particular scope can have both a struct and a function of the same
1899/// name, and each can be found by certain lookup criteria. For more
1900/// information about lookup criteria, see the documentation for the
1901/// class LookupCriteria.
1902///
1903/// @param S        The scope from which unqualified name lookup will
1904/// begin. If the lookup criteria permits, name lookup may also search
1905/// in the parent scopes.
1906///
1907/// @param [in,out] R Specifies the lookup to perform (e.g., the name to
1908/// look up and the lookup kind), and is updated with the results of lookup
1909/// including zero or more declarations and possibly additional information
1910/// used to diagnose ambiguities.
1911///
1912/// @returns \c true if lookup succeeded and false otherwise.
1913bool Sema::LookupName(LookupResult &R, Scope *S, bool AllowBuiltinCreation) {
DeclarationName Name = R.getLookupName();
if (!Name) return false;

LookupNameKind NameKind = R.getLookupKind();

if (!getLangOpts().CPlusPlus) {
  // Unqualified name lookup in C/Objective-C is purely lexical, so
  // search in the declarations attached to the name.
  if (NameKind == Sema::LookupRedeclarationWithLinkage) {
    // Find the nearest non-transparent declaration scope.
    while (!(S->getFlags() & Scope::DeclScope) ||
           (S->getEntity() && S->getEntity()->isTransparentContext()))
      S = S->getParent();
  }

  // When performing a scope lookup, we want to find local extern decls.
  FindLocalExternScope FindLocals(R);

  // Scan up the scope chain looking for a decl that matches this
  // identifier that is in the appropriate namespace.  This search
  // should not take long, as shadowing of names is uncommon, and
  // deep shadowing is extremely uncommon.
  bool LeftStartingScope = false;

  for (IdentifierResolver::iterator I = IdResolver.begin(Name),
                                 IEnd = IdResolver.end();
       I != IEnd; ++I)
    if (NamedDecl *D = R.getAcceptableDecl(*I)) {
      if (NameKind == LookupRedeclarationWithLinkage) {
        // Determine whether this (or a previous) declaration is
        // out-of-scope.
        if (!LeftStartingScope && !S->isDeclScope(*I))
          LeftStartingScope = true;

        // If we found something outside of our starting scope that
        // does not have linkage, skip it.
        if (LeftStartingScope && !((*I)->hasLinkage())) {
          R.setShadowed();
          continue;
        }
      }
      else if (NameKind == LookupObjCImplicitSelfParam &&
               !isa<ImplicitParamDecl>(*I))
        continue;

      R.addDecl(D);

      // Check whether there are any other declarations with the same name
      // and in the same scope.
      if (I != IEnd) {
        // Find the scope in which this declaration was declared (if it
        // actually exists in a Scope).
        while (S && !S->isDeclScope(D))
          S = S->getParent();

        // If the scope containing the declaration is the translation unit,
        // then we'll need to perform our checks based on the matching
        // DeclContexts rather than matching scopes.
        if (S && isNamespaceOrTranslationUnitScope(S))
          S = nullptr;

        // Compute the DeclContext, if we need it.
        DeclContext *DC = nullptr;
        if (!S)
          DC = (*I)->getDeclContext()->getRedeclContext();

        IdentifierResolver::iterator LastI = I;
        for (++LastI; LastI != IEnd; ++LastI) {
          if (S) {
            // Match based on scope.
            if (!S->isDeclScope(*LastI))
              break;
          } else {
            // Match based on DeclContext.
            DeclContext *LastDC
              = (*LastI)->getDeclContext()->getRedeclContext();
            if (!LastDC->Equals(DC))
              break;
          }

          // If the declaration is in the right namespace and visible, add it.
          if (NamedDecl *LastD = R.getAcceptableDecl(*LastI))
            R.addDecl(LastD);
        }

        R.resolveKind();
      }

      return true;
    }
} else {
  // Perform C++ unqualified name lookup.
  if (CppLookupName(R, S))
    return true;
}

// If we didn't find a use of this identifier, and if the identifier
// corresponds to a compiler builtin, create the decl object for the builtin
// now, injecting it into translation unit scope, and return it.
if (AllowBuiltinCreation && LookupBuiltin(R))
  return true;

// If we didn't find a use of this identifier, the ExternalSource
// may be able to handle the situation.
// Note: some lookup failures are expected!
// See e.g. R.isForRedeclaration().
return (ExternalSource && ExternalSource->LookupUnqualified(R, S));
2021}

2023/// Perform qualified name lookup in the namespaces nominated by
2024/// using directives by the given context.
2025///
2026/// C++98 [namespace.qual]p2:
2027///   Given X::m (where X is a user-declared namespace), or given \::m
2028///   (where X is the global namespace), let S be the set of all
2029///   declarations of m in X and in the transitive closure of all
2030///   namespaces nominated by using-directives in X and its used
2031///   namespaces, except that using-directives are ignored in any
2032///   namespace, including X, directly containing one or more
2033///   declarations of m. No namespace is searched more than once in
2034///   the lookup of a name. If S is the empty set, the program is
2035///   ill-formed. Otherwise, if S has exactly one member, or if the
2036///   context of the reference is a using-declaration
2037///   (namespace.udecl), S is the required set of declarations of
2038///   m. Otherwise if the use of m is not one that allows a unique
2039///   declaration to be chosen from S, the program is ill-formed.
2040///
2041/// C++98 [namespace.qual]p5:
2042///   During the lookup of a qualified namespace member name, if the
2043///   lookup finds more than one declaration of the member, and if one
2044///   declaration introduces a class name or enumeration name and the
2045///   other declarations either introduce the same object, the same
2046///   enumerator or a set of functions, the non-type name hides the
2047///   class or enumeration name if and only if the declarations are
2048///   from the same namespace; otherwise (the declarations are from
2049///   different namespaces), the program is ill-formed.
2050static bool LookupQualifiedNameInUsingDirectives(Sema &S, LookupResult &R,
                                               DeclContext *StartDC) {
assert(StartDC->isFileContext() && "start context is not a file context")((void)0);

// We have not yet looked into these namespaces, much less added
// their "using-children" to the queue.
SmallVector<NamespaceDecl*, 8> Queue;

// We have at least added all these contexts to the queue.
llvm::SmallPtrSet<DeclContext*, 8> Visited;
Visited.insert(StartDC);

// We have already looked into the initial namespace; seed the queue
// with its using-children.
for (auto *I : StartDC->using_directives()) {
  NamespaceDecl *ND = I->getNominatedNamespace()->getOriginalNamespace();
  if (S.isVisible(I) && Visited.insert(ND).second)
    Queue.push_back(ND);
}

// The easiest way to implement the restriction in [namespace.qual]p5
// is to check whether any of the individual results found a tag
// and, if so, to declare an ambiguity if the final result is not
// a tag.
bool FoundTag = false;
bool FoundNonTag = false;

LookupResult LocalR(LookupResult::Temporary, R);

bool Found = false;
while (!Queue.empty()) {
  NamespaceDecl *ND = Queue.pop_back_val();

  // We go through some convolutions here to avoid copying results
  // between LookupResults.
  bool UseLocal = !R.empty();
  LookupResult &DirectR = UseLocal ? LocalR : R;
  bool FoundDirect = LookupDirect(S, DirectR, ND);

  if (FoundDirect) {
    // First do any local hiding.
    DirectR.resolveKind();

    // If the local result is a tag, remember that.
    if (DirectR.isSingleTagDecl())
      FoundTag = true;
    else
      FoundNonTag = true;

    // Append the local results to the total results if necessary.
    if (UseLocal) {
      R.addAllDecls(LocalR);
      LocalR.clear();
    }
  }

  // If we find names in this namespace, ignore its using directives.
  if (FoundDirect) {
    Found = true;
    continue;
  }

  for (auto I : ND->using_directives()) {
    NamespaceDecl *Nom = I->getNominatedNamespace();
    if (S.isVisible(I) && Visited.insert(Nom).second)
      Queue.push_back(Nom);
  }
}

if (Found) {
  if (FoundTag && FoundNonTag)
    R.setAmbiguousQualifiedTagHiding();
  else
    R.resolveKind();
}

return Found;
2127}

2129/// Perform qualified name lookup into a given context.
2130///
2131/// Qualified name lookup (C++ [basic.lookup.qual]) is used to find
2132/// names when the context of those names is explicit specified, e.g.,
2133/// "std::vector" or "x->member", or as part of unqualified name lookup.
2134///
2135/// Different lookup criteria can find different names. For example, a
2136/// particular scope can have both a struct and a function of the same
2137/// name, and each can be found by certain lookup criteria. For more
2138/// information about lookup criteria, see the documentation for the
2139/// class LookupCriteria.
2140///
2141/// \param R captures both the lookup criteria and any lookup results found.
2142///
2143/// \param LookupCtx The context in which qualified name lookup will
2144/// search. If the lookup criteria permits, name lookup may also search
2145/// in the parent contexts or (for C++ classes) base classes.
2146///
2147/// \param InUnqualifiedLookup true if this is qualified name lookup that
2148/// occurs as part of unqualified name lookup.
2149///
2150/// \returns true if lookup succeeded, false if it failed.
2151bool Sema::LookupQualifiedName(LookupResult &R, DeclContext *LookupCtx,
                             bool InUnqualifiedLookup) {
assert(LookupCtx && "Sema::LookupQualifiedName requires a lookup context")((void)0);

if (!R.getLookupName())
  return false;

// Make sure that the declaration context is complete.
assert((!isa<TagDecl>(LookupCtx) ||((void)0)
        LookupCtx->isDependentContext() ||((void)0)
        cast<TagDecl>(LookupCtx)->isCompleteDefinition() ||((void)0)
        cast<TagDecl>(LookupCtx)->isBeingDefined()) &&((void)0)
       "Declaration context must already be complete!")((void)0);

struct QualifiedLookupInScope {
  bool oldVal;
  DeclContext *Context;
  // Set flag in DeclContext informing debugger that we're looking for qualified name
  QualifiedLookupInScope(DeclContext *ctx) : Context(ctx) {
    oldVal = ctx->setUseQualifiedLookup();
  }
  ~QualifiedLookupInScope() {
    Context->setUseQualifiedLookup(oldVal);
  }
} QL(LookupCtx);

if (LookupDirect(*this, R, LookupCtx)) {
  R.resolveKind();
  if (isa<CXXRecordDecl>(LookupCtx))
    R.setNamingClass(cast<CXXRecordDecl>(LookupCtx));
  return true;
}

// Don't descend into implied contexts for redeclarations.
// C++98 [namespace.qual]p6:
//   In a declaration for a namespace member in which the
//   declarator-id is a qualified-id, given that the qualified-id
//   for the namespace member has the form
//     nested-name-specifier unqualified-id
//   the unqualified-id shall name a member of the namespace
//   designated by the nested-name-specifier.
// See also [class.mfct]p5 and [class.static.data]p2.
if (R.isForRedeclaration())
  return false;

// If this is a namespace, look it up in the implied namespaces.
if (LookupCtx->isFileContext())
  return LookupQualifiedNameInUsingDirectives(*this, R, LookupCtx);

// If this isn't a C++ class, we aren't allowed to look into base
// classes, we're done.
CXXRecordDecl *LookupRec = dyn_cast<CXXRecordDecl>(LookupCtx);
if (!LookupRec || !LookupRec->getDefinition())
  return false;

// We're done for lookups that can never succeed for C++ classes.
if (R.getLookupKind() == LookupOperatorName ||
    R.getLookupKind() == LookupNamespaceName ||
    R.getLookupKind() == LookupObjCProtocolName ||
    R.getLookupKind() == LookupLabel)
  return false;

// If we're performing qualified name lookup into a dependent class,
// then we are actually looking into a current instantiation. If we have any
// dependent base classes, then we either have to delay lookup until
// template instantiation time (at which point all bases will be available)
// or we have to fail.
if (!InUnqualifiedLookup && LookupRec->isDependentContext() &&
    LookupRec->hasAnyDependentBases()) {
  R.setNotFoundInCurrentInstantiation();
  return false;
}

// Perform lookup into our base classes.

DeclarationName Name = R.getLookupName();
unsigned IDNS = R.getIdentifierNamespace();

// Look for this member in our base classes.
auto BaseCallback = [Name, IDNS](const CXXBaseSpecifier *Specifier,
                                 CXXBasePath &Path) -> bool {
  CXXRecordDecl *BaseRecord = Specifier->getType()->getAsCXXRecordDecl();
  // Drop leading non-matching lookup results from the declaration list so
  // we don't need to consider them again below.
  for (Path.Decls = BaseRecord->lookup(Name).begin();
       Path.Decls != Path.Decls.end(); ++Path.Decls) {
    if ((*Path.Decls)->isInIdentifierNamespace(IDNS))
      return true;
  }
  return false;
};

CXXBasePaths Paths;
Paths.setOrigin(LookupRec);
if (!LookupRec->lookupInBases(BaseCallback, Paths))
  return false;

R.setNamingClass(LookupRec);

// C++ [class.member.lookup]p2:
//   [...] If the resulting set of declarations are not all from
//   sub-objects of the same type, or the set has a nonstatic member
//   and includes members from distinct sub-objects, there is an
//   ambiguity and the program is ill-formed. Otherwise that set is
//   the result of the lookup.
QualType SubobjectType;
int SubobjectNumber = 0;
AccessSpecifier SubobjectAccess = AS_none;

// Check whether the given lookup result contains only static members.
auto HasOnlyStaticMembers = [&](DeclContext::lookup_iterator Result) {
  for (DeclContext::lookup_iterator I = Result, E = I.end(); I != E; ++I)
    if ((*I)->isInIdentifierNamespace(IDNS) && (*I)->isCXXInstanceMember())
      return false;
  return true;
};

bool TemplateNameLookup = R.isTemplateNameLookup();

// Determine whether two sets of members contain the same members, as
// required by C++ [class.member.lookup]p6.
auto HasSameDeclarations = [&](DeclContext::lookup_iterator A,
                               DeclContext::lookup_iterator B) {
  using Iterator = DeclContextLookupResult::iterator;
  using Result = const void *;

  auto Next = [&](Iterator &It, Iterator End) -> Result {
    while (It != End) {
      NamedDecl *ND = *It++;
      if (!ND->isInIdentifierNamespace(IDNS))
        continue;

      // C++ [temp.local]p3:
      //   A lookup that finds an injected-class-name (10.2) can result in
      //   an ambiguity in certain cases (for example, if it is found in
      //   more than one base class). If all of the injected-class-names
      //   that are found refer to specializations of the same class
      //   template, and if the name is used as a template-name, the
      //   reference refers to the class template itself and not a
      //   specialization thereof, and is not ambiguous.
      if (TemplateNameLookup)
        if (auto *TD = getAsTemplateNameDecl(ND))
          ND = TD;

      // C++ [class.member.lookup]p3:
      //   type declarations (including injected-class-names) are replaced by
      //   the types they designate
      if (const TypeDecl *TD = dyn_cast<TypeDecl>(ND->getUnderlyingDecl())) {
        QualType T = Context.getTypeDeclType(TD);
        return T.getCanonicalType().getAsOpaquePtr();
      }

      return ND->getUnderlyingDecl()->getCanonicalDecl();
    }
    return nullptr;
  };

  // We'll often find the declarations are in the same order. Handle this
  // case (and the special case of only one declaration) efficiently.
  Iterator AIt = A, BIt = B, AEnd, BEnd;
  while (true) {
    Result AResult = Next(AIt, AEnd);
    Result BResult = Next(BIt, BEnd);
    if (!AResult && !BResult)
      return true;
    if (!AResult || !BResult)
      return false;
    if (AResult != BResult) {
      // Found a mismatch; carefully check both lists, accounting for the
      // possibility of declarations appearing more than once.
      llvm::SmallDenseMap<Result, bool, 32> AResults;
      for (; AResult; AResult = Next(AIt, AEnd))
        AResults.insert({AResult, /*FoundInB*/false});
      unsigned Found = 0;
      for (; BResult; BResult = Next(BIt, BEnd)) {
        auto It = AResults.find(BResult);
        if (It == AResults.end())
          return false;
        if (!It->second) {
          It->second = true;
          ++Found;
        }
      }
      return AResults.size() == Found;
    }
  }
};

for (CXXBasePaths::paths_iterator Path = Paths.begin(), PathEnd = Paths.end();
     Path != PathEnd; ++Path) {
  const CXXBasePathElement &PathElement = Path->back();

  // Pick the best (i.e. most permissive i.e. numerically lowest) access
  // across all paths.
  SubobjectAccess = std::min(SubobjectAccess, Path->Access);

  // Determine whether we're looking at a distinct sub-object or not.
  if (SubobjectType.isNull()) {
    // This is the first subobject we've looked at. Record its type.
    SubobjectType = Context.getCanonicalType(PathElement.Base->getType());
    SubobjectNumber = PathElement.SubobjectNumber;
    continue;
  }

  if (SubobjectType !=
      Context.getCanonicalType(PathElement.Base->getType())) {
    // We found members of the given name in two subobjects of
    // different types. If the declaration sets aren't the same, this
    // lookup is ambiguous.
    //
    // FIXME: The language rule says that this applies irrespective of
    // whether the sets contain only static members.
    if (HasOnlyStaticMembers(Path->Decls) &&
        HasSameDeclarations(Paths.begin()->Decls, Path->Decls))
      continue;

    R.setAmbiguousBaseSubobjectTypes(Paths);
    return true;
  }

  // FIXME: This language rule no longer exists. Checking for ambiguous base
  // subobjects should be done as part of formation of a class member access
  // expression (when converting the object parameter to the member's type).
  if (SubobjectNumber != PathElement.SubobjectNumber) {
    // We have a different subobject of the same type.

    // C++ [class.member.lookup]p5:
    //   A static member, a nested type or an enumerator defined in
    //   a base class T can unambiguously be found even if an object
    //   has more than one base class subobject of type T.
    if (HasOnlyStaticMembers(Path->Decls))
      continue;

    // We have found a nonstatic member name in multiple, distinct
    // subobjects. Name lookup is ambiguous.
    R.setAmbiguousBaseSubobjects(Paths);
    return true;
  }
}

// Lookup in a base class succeeded; return these results.

for (DeclContext::lookup_iterator I = Paths.front().Decls, E = I.end();
     I != E; ++I) {
  AccessSpecifier AS = CXXRecordDecl::MergeAccess(SubobjectAccess,
                                                  (*I)->getAccess());
  if (NamedDecl *ND = R.getAcceptableDecl(*I))
    R.addDecl(ND, AS);
}
R.resolveKind();
return true;
2402}

2404/// Performs qualified name lookup or special type of lookup for
2405/// "__super::" scope specifier.
2406///
2407/// This routine is a convenience overload meant to be called from contexts
2408/// that need to perform a qualified name lookup with an optional C++ scope
2409/// specifier that might require special kind of lookup.
2410///
2411/// \param R captures both the lookup criteria and any lookup results found.
2412///
2413/// \param LookupCtx The context in which qualified name lookup will
2414/// search.
2415///
2416/// \param SS An optional C++ scope-specifier.
2417///
2418/// \returns true if lookup succeeded, false if it failed.
2419bool Sema::LookupQualifiedName(LookupResult &R, DeclContext *LookupCtx,
                             CXXScopeSpec &SS) {
auto *NNS = SS.getScopeRep();
if (NNS && NNS->getKind() == NestedNameSpecifier::Super)
  return LookupInSuper(R, NNS->getAsRecordDecl());
else

  return LookupQualifiedName(R, LookupCtx);
2427}

2429/// Performs name lookup for a name that was parsed in the
2430/// source code, and may contain a C++ scope specifier.
2431///
2432/// This routine is a convenience routine meant to be called from
2433/// contexts that receive a name and an optional C++ scope specifier
2434/// (e.g., "N::M::x"). It will then perform either qualified or
2435/// unqualified name lookup (with LookupQualifiedName or LookupName,
2436/// respectively) on the given name and return those results. It will
2437/// perform a special type of lookup for "__super::" scope specifier.
2438///
2439/// @param S        The scope from which unqualified name lookup will
2440/// begin.
2441///
2442/// @param SS       An optional C++ scope-specifier, e.g., "::N::M".
2443///
2444/// @param EnteringContext Indicates whether we are going to enter the
2445/// context of the scope-specifier SS (if present).
2446///
2447/// @returns True if any decls were found (but possibly ambiguous)
2448bool Sema::LookupParsedName(LookupResult &R, Scope *S, CXXScopeSpec *SS,
                          bool AllowBuiltinCreation, bool EnteringContext) {
if (SS && SS->isInvalid()) {
  // When the scope specifier is invalid, don't even look for
  // anything.
  return false;
}

if (SS && SS->isSet()) {
  NestedNameSpecifier *NNS = SS->getScopeRep();
  if (NNS->getKind() == NestedNameSpecifier::Super)
    return LookupInSuper(R, NNS->getAsRecordDecl());

  if (DeclContext *DC = computeDeclContext(*SS, EnteringContext)) {
    // We have resolved the scope specifier to a particular declaration
    // contex, and will perform name lookup in that context.
    if (!DC->isDependentContext() && RequireCompleteDeclContext(*SS, DC))
      return false;

    R.setContextRange(SS->getRange());
    return LookupQualifiedName(R, DC);
  }

  // We could not resolve the scope specified to a specific declaration
  // context, which means that SS refers to an unknown specialization.
  // Name lookup can't find anything in this case.
  R.setNotFoundInCurrentInstantiation();
  R.setContextRange(SS->getRange());
  return false;
}

// Perform unqualified name lookup starting in the given scope.
return LookupName(R, S, AllowBuiltinCreation);
2481}

2483/// Perform qualified name lookup into all base classes of the given
2484/// class.
2485///
2486/// \param R captures both the lookup criteria and any lookup results found.
2487///
2488/// \param Class The context in which qualified name lookup will
2489/// search. Name lookup will search in all base classes merging the results.
2490///
2491/// @returns True if any decls were found (but possibly ambiguous)
2492bool Sema::LookupInSuper(LookupResult &R, CXXRecordDecl *Class) {
// The access-control rules we use here are essentially the rules for
// doing a lookup in Class that just magically skipped the direct
// members of Class itself.  That is, the naming class is Class, and the
// access includes the access of the base.
for (const auto &BaseSpec : Class->bases()) {
  CXXRecordDecl *RD = cast<CXXRecordDecl>(
      BaseSpec.getType()->castAs<RecordType>()->getDecl());
  LookupResult Result(*this, R.getLookupNameInfo(), R.getLookupKind());
  Result.setBaseObjectType(Context.getRecordType(Class));
  LookupQualifiedName(Result, RD);

  // Copy the lookup results into the target, merging the base's access into
  // the path access.
  for (auto I = Result.begin(), E = Result.end(); I != E; ++I) {
    R.addDecl(I.getDecl(),
              CXXRecordDecl::MergeAccess(BaseSpec.getAccessSpecifier(),
                                         I.getAccess()));
  }

  Result.suppressDiagnostics();
}

R.resolveKind();
R.setNamingClass(Class);

return !R.empty();
2519}

2521/// Produce a diagnostic describing the ambiguity that resulted
2522/// from name lookup.
2523///
2524/// \param Result The result of the ambiguous lookup to be diagnosed.
2525void Sema::DiagnoseAmbiguousLookup(LookupResult &Result) {
assert(Result.isAmbiguous() && "Lookup result must be ambiguous")((void)0);

DeclarationName Name = Result.getLookupName();
SourceLocation NameLoc = Result.getNameLoc();
SourceRange LookupRange = Result.getContextRange();

switch (Result.getAmbiguityKind()) {
case LookupResult::AmbiguousBaseSubobjects: {
  CXXBasePaths *Paths = Result.getBasePaths();
  QualType SubobjectType = Paths->front().back().Base->getType();
  Diag(NameLoc, diag::err_ambiguous_member_multiple_subobjects)
    << Name << SubobjectType << getAmbiguousPathsDisplayString(*Paths)
    << LookupRange;

  DeclContext::lookup_iterator Found = Paths->front().Decls;
  while (isa<CXXMethodDecl>(*Found) &&
         cast<CXXMethodDecl>(*Found)->isStatic())
    ++Found;

  Diag((*Found)->getLocation(), diag::note_ambiguous_member_found);
  break;
}

case LookupResult::AmbiguousBaseSubobjectTypes: {
  Diag(NameLoc, diag::err_ambiguous_member_multiple_subobject_types)
    << Name << LookupRange;

  CXXBasePaths *Paths = Result.getBasePaths();
  std::set<const NamedDecl *> DeclsPrinted;
  for (CXXBasePaths::paths_iterator Path = Paths->begin(),
                                    PathEnd = Paths->end();
       Path != PathEnd; ++Path) {
    const NamedDecl *D = *Path->Decls;
    if (!D->isInIdentifierNamespace(Result.getIdentifierNamespace()))
      continue;
    if (DeclsPrinted.insert(D).second) {
      if (const auto *TD = dyn_cast<TypedefNameDecl>(D->getUnderlyingDecl()))
        Diag(D->getLocation(), diag::note_ambiguous_member_type_found)
            << TD->getUnderlyingType();
      else if (const auto *TD = dyn_cast<TypeDecl>(D->getUnderlyingDecl()))
        Diag(D->getLocation(), diag::note_ambiguous_member_type_found)
            << Context.getTypeDeclType(TD);
      else
        Diag(D->getLocation(), diag::note_ambiguous_member_found);
    }
  }
  break;
}

case LookupResult::AmbiguousTagHiding: {
  Diag(NameLoc, diag::err_ambiguous_tag_hiding) << Name << LookupRange;

  llvm::SmallPtrSet<NamedDecl*, 8> TagDecls;

  for (auto *D : Result)
    if (TagDecl *TD = dyn_cast<TagDecl>(D)) {
      TagDecls.insert(TD);
      Diag(TD->getLocation(), diag::note_hidden_tag);
    }

  for (auto *D : Result)
    if (!isa<TagDecl>(D))
      Diag(D->getLocation(), diag::note_hiding_object);

  // For recovery purposes, go ahead and implement the hiding.
  LookupResult::Filter F = Result.makeFilter();
  while (F.hasNext()) {
    if (TagDecls.count(F.next()))
      F.erase();
  }
  F.done();
  break;
}

case LookupResult::AmbiguousReference: {
  Diag(NameLoc, diag::err_ambiguous_reference) << Name << LookupRange;

  for (auto *D : Result)
    Diag(D->getLocation(), diag::note_ambiguous_candidate) << D;
  break;
}
}
2608}

2610namespace {
struct AssociatedLookup {
  AssociatedLookup(Sema &S, SourceLocation InstantiationLoc,
                   Sema::AssociatedNamespaceSet &Namespaces,
                   Sema::AssociatedClassSet &Classes)
    : S(S), Namespaces(Namespaces), Classes(Classes),
      InstantiationLoc(InstantiationLoc) {
  }

  bool addClassTransitive(CXXRecordDecl *RD) {
    Classes.insert(RD);
    return ClassesTransitive.insert(RD);
  }

  Sema &S;
  Sema::AssociatedNamespaceSet &Namespaces;
  Sema::AssociatedClassSet &Classes;
  SourceLocation InstantiationLoc;

private:
  Sema::AssociatedClassSet ClassesTransitive;
};
2632} // end anonymous namespace

2634static void
2635addAssociatedClassesAndNamespaces(AssociatedLookup &Result, QualType T);

2637// Given the declaration context \param Ctx of a class, class template or
2638// enumeration, add the associated namespaces to \param Namespaces as described
2639// in [basic.lookup.argdep]p2.
2640static void CollectEnclosingNamespace(Sema::AssociatedNamespaceSet &Namespaces,
                                    DeclContext *Ctx) {
// The exact wording has been changed in C++14 as a result of
// CWG 1691 (see also CWG 1690 and CWG 1692). We apply it unconditionally
// to all language versions since it is possible to return a local type
// from a lambda in C++11.
//
// C++14 [basic.lookup.argdep]p2:
//   If T is a class type [...]. Its associated namespaces are the innermost
//   enclosing namespaces of its associated classes. [...]
//
//   If T is an enumeration type, its associated namespace is the innermost
//   enclosing namespace of its declaration. [...]

// We additionally skip inline namespaces. The innermost non-inline namespace
// contains all names of all its nested inline namespaces anyway, so we can
// replace the entire inline namespace tree with its root.
while (!Ctx->isFileContext() || Ctx->isInlineNamespace())
  Ctx = Ctx->getParent();

Namespaces.insert(Ctx->getPrimaryContext());
2661}

2663// Add the associated classes and namespaces for argument-dependent
2664// lookup that involves a template argument (C++ [basic.lookup.argdep]p2).
2665static void
2666addAssociatedClassesAndNamespaces(AssociatedLookup &Result,
                                const TemplateArgument &Arg) {
// C++ [basic.lookup.argdep]p2, last bullet:
//   -- [...] ;
switch (Arg.getKind()) {
  case TemplateArgument::Null:
    break;

  case TemplateArgument::Type:
    // [...] the namespaces and classes associated with the types of the
    // template arguments provided for template type parameters (excluding
    // template template parameters)
    addAssociatedClassesAndNamespaces(Result, Arg.getAsType());
    break;

  case TemplateArgument::Template:
  case TemplateArgument::TemplateExpansion: {
    // [...] the namespaces in which any template template arguments are
    // defined; and the classes in which any member templates used as
    // template template arguments are defined.
    TemplateName Template = Arg.getAsTemplateOrTemplatePattern();
    if (ClassTemplateDecl *ClassTemplate
               = dyn_cast<ClassTemplateDecl>(Template.getAsTemplateDecl())) {
      DeclContext *Ctx = ClassTemplate->getDeclContext();
      if (CXXRecordDecl *EnclosingClass = dyn_cast<CXXRecordDecl>(Ctx))
        Result.Classes.insert(EnclosingClass);
      // Add the associated namespace for this class.
      CollectEnclosingNamespace(Result.Namespaces, Ctx);
    }
    break;
  }

  case TemplateArgument::Declaration:
  case TemplateArgument::Integral:
  case TemplateArgument::Expression:
  case TemplateArgument::NullPtr:
    // [Note: non-type template arguments do not contribute to the set of
    //  associated namespaces. ]
    break;

  case TemplateArgument::Pack:
    for (const auto &P : Arg.pack_elements())
      addAssociatedClassesAndNamespaces(Result, P);
    break;
}
2711}

2713// Add the associated classes and namespaces for argument-dependent lookup
2714// with an argument of class type (C++ [basic.lookup.argdep]p2).
2715static void
2716addAssociatedClassesAndNamespaces(AssociatedLookup &Result,
                                CXXRecordDecl *Class) {

// Just silently ignore anything whose name is __va_list_tag.
if (Class->getDeclName() == Result.S.VAListTagName)
  return;

// C++ [basic.lookup.argdep]p2:
//   [...]
//     -- If T is a class type (including unions), its associated
//        classes are: the class itself; the class of which it is a
//        member, if any; and its direct and indirect base classes.
//        Its associated namespaces are the innermost enclosing
//        namespaces of its associated classes.

// Add the class of which it is a member, if any.
DeclContext *Ctx = Class->getDeclContext();
if (CXXRecordDecl *EnclosingClass = dyn_cast<CXXRecordDecl>(Ctx))
  Result.Classes.insert(EnclosingClass);

// Add the associated namespace for this class.
CollectEnclosingNamespace(Result.Namespaces, Ctx);

// -- If T is a template-id, its associated namespaces and classes are
//    the namespace in which the template is defined; for member
//    templates, the member template's class; the namespaces and classes
//    associated with the types of the template arguments provided for
//    template type parameters (excluding template template parameters); the
//    namespaces in which any template template arguments are defined; and
//    the classes in which any member templates used as template template
//    arguments are defined. [Note: non-type template arguments do not
//    contribute to the set of associated namespaces. ]
if (ClassTemplateSpecializationDecl *Spec
      = dyn_cast<ClassTemplateSpecializationDecl>(Class)) {
  DeclContext *Ctx = Spec->getSpecializedTemplate()->getDeclContext();
  if (CXXRecordDecl *EnclosingClass = dyn_cast<CXXRecordDecl>(Ctx))
    Result.Classes.insert(EnclosingClass);
  // Add the associated namespace for this class.
  CollectEnclosingNamespace(Result.Namespaces, Ctx);

  const TemplateArgumentList &TemplateArgs = Spec->getTemplateArgs();
  for (unsigned I = 0, N = TemplateArgs.size(); I != N; ++I)
    addAssociatedClassesAndNamespaces(Result, TemplateArgs[I]);
}

// Add the class itself. If we've already transitively visited this class,
// we don't need to visit base classes.
if (!Result.addClassTransitive(Class))
  return;

// Only recurse into base classes for complete types.
if (!Result.S.isCompleteType(Result.InstantiationLoc,
                             Result.S.Context.getRecordType(Class)))
  return;

// Add direct and indirect base classes along with their associated
// namespaces.
SmallVector<CXXRecordDecl *, 32> Bases;
Bases.push_back(Class);
while (!Bases.empty()) {
  // Pop this class off the stack.
  Class = Bases.pop_back_val();

  // Visit the base classes.
  for (const auto &Base : Class->bases()) {
    const RecordType *BaseType = Base.getType()->getAs<RecordType>();
    // In dependent contexts, we do ADL twice, and the first time around,
    // the base type might be a dependent TemplateSpecializationType, or a
    // TemplateTypeParmType. If that happens, simply ignore it.
    // FIXME: If we want to support export, we probably need to add the
    // namespace of the template in a TemplateSpecializationType, or even
    // the classes and namespaces of known non-dependent arguments.
    if (!BaseType)
      continue;
    CXXRecordDecl *BaseDecl = cast<CXXRecordDecl>(BaseType->getDecl());
    if (Result.addClassTransitive(BaseDecl)) {
      // Find the associated namespace for this base class.
      DeclContext *BaseCtx = BaseDecl->getDeclContext();
      CollectEnclosingNamespace(Result.Namespaces, BaseCtx);

      // Make sure we visit the bases of this base class.
      if (BaseDecl->bases_begin() != BaseDecl->bases_end())
        Bases.push_back(BaseDecl);
    }
  }
}
2802}

2804// Add the associated classes and namespaces for
2805// argument-dependent lookup with an argument of type T
2806// (C++ [basic.lookup.koenig]p2).
2807static void
2808addAssociatedClassesAndNamespaces(AssociatedLookup &Result, QualType Ty) {
// C++ [basic.lookup.koenig]p2:
//
//   For each argument type T in the function call, there is a set
//   of zero or more associated namespaces and a set of zero or more
//   associated classes to be considered. The sets of namespaces and
//   classes is determined entirely by the types of the function
//   arguments (and the namespace of any template template
//   argument). Typedef names and using-declarations used to specify
//   the types do not contribute to this set. The sets of namespaces
//   and classes are determined in the following way:

SmallVector<const Type *, 16> Queue;
const Type *T = Ty->getCanonicalTypeInternal().getTypePtr();

while (true) {
  switch (T->getTypeClass()) {

2826#define TYPE(Class, Base)
2827#define DEPENDENT_TYPE(Class, Base) case Type::Class:
2828#define NON_CANONICAL_TYPE(Class, Base) case Type::Class:
2829#define NON_CANONICAL_UNLESS_DEPENDENT_TYPE(Class, Base) case Type::Class:
2830#define ABSTRACT_TYPE(Class, Base)
2831#include "clang/AST/TypeNodes.inc"
    // T is canonical.  We can also ignore dependent types because
    // we don't need to do ADL at the definition point, but if we
    // wanted to implement template export (or if we find some other
    // use for associated classes and namespaces...) this would be
    // wrong.
    break;

  //    -- If T is a pointer to U or an array of U, its associated
  //       namespaces and classes are those associated with U.
  case Type::Pointer:
    T = cast<PointerType>(T)->getPointeeType().getTypePtr();
    continue;
  case Type::ConstantArray:
  case Type::IncompleteArray:
  case Type::VariableArray:
    T = cast<ArrayType>(T)->getElementType().getTypePtr();
    continue;

  //     -- If T is a fundamental type, its associated sets of
  //        namespaces and classes are both empty.
  case Type::Builtin:
    break;

  //     -- If T is a class type (including unions), its associated
  //        classes are: the class itself; the class of which it is
  //        a member, if any; and its direct and indirect base classes.
  //        Its associated namespaces are the innermost enclosing
  //        namespaces of its associated classes.
  case Type::Record: {
    CXXRecordDecl *Class =
        cast<CXXRecordDecl>(cast<RecordType>(T)->getDecl());
    addAssociatedClassesAndNamespaces(Result, Class);
    break;
  }

  //     -- If T is an enumeration type, its associated namespace
  //        is the innermost enclosing namespace of its declaration.
  //        If it is a class member, its associated class is the
  //        member’s class; else it has no associated class.
  case Type::Enum: {
    EnumDecl *Enum = cast<EnumType>(T)->getDecl();

    DeclContext *Ctx = Enum->getDeclContext();
    if (CXXRecordDecl *EnclosingClass = dyn_cast<CXXRecordDecl>(Ctx))
      Result.Classes.insert(EnclosingClass);

    // Add the associated namespace for this enumeration.
    CollectEnclosingNamespace(Result.Namespaces, Ctx);

    break;
  }

  //     -- If T is a function type, its associated namespaces and
  //        classes are those associated with the function parameter
  //        types and those associated with the return type.
  case Type::FunctionProto: {
    const FunctionProtoType *Proto = cast<FunctionProtoType>(T);
    for (const auto &Arg : Proto->param_types())
      Queue.push_back(Arg.getTypePtr());
    // fallthrough
    LLVM_FALLTHROUGH[[gnu::fallthrough]];
  }
  case Type::FunctionNoProto: {
    const FunctionType *FnType = cast<FunctionType>(T);
    T = FnType->getReturnType().getTypePtr();
    continue;
  }

  //     -- If T is a pointer to a member function of a class X, its
  //        associated namespaces and classes are those associated
  //        with the function parameter types and return type,
  //        together with those associated with X.
  //
  //     -- If T is a pointer to a data member of class X, its
  //        associated namespaces and classes are those associated
  //        with the member type together with those associated with
  //        X.
  case Type::MemberPointer: {
    const MemberPointerType *MemberPtr = cast<MemberPointerType>(T);

    // Queue up the class type into which this points.
    Queue.push_back(MemberPtr->getClass());

    // And directly continue with the pointee type.
    T = MemberPtr->getPointeeType().getTypePtr();
    continue;
  }

  // As an extension, treat this like a normal pointer.
  case Type::BlockPointer:
    T = cast<BlockPointerType>(T)->getPointeeType().getTypePtr();
    continue;

  // References aren't covered by the standard, but that's such an
  // obvious defect that we cover them anyway.
  case Type::LValueReference:
  case Type::RValueReference:
    T = cast<ReferenceType>(T)->getPointeeType().getTypePtr();
    continue;

  // These are fundamental types.
  case Type::Vector:
  case Type::ExtVector:
  case Type::ConstantMatrix:
  case Type::Complex:
  case Type::ExtInt:
    break;

  // Non-deduced auto types only get here for error cases.
  case Type::Auto:
  case Type::DeducedTemplateSpecialization:
    break;

  // If T is an Objective-C object or interface type, or a pointer to an
  // object or interface type, the associated namespace is the global
  // namespace.
  case Type::ObjCObject:
  case Type::ObjCInterface:
  case Type::ObjCObjectPointer:
    Result.Namespaces.insert(Result.S.Context.getTranslationUnitDecl());
    break;

  // Atomic types are just wrappers; use the associations of the
  // contained type.
  case Type::Atomic:
    T = cast<AtomicType>(T)->getValueType().getTypePtr();
    continue;
  case Type::Pipe:
    T = cast<PipeType>(T)->getElementType().getTypePtr();
    continue;
  }

  if (Queue.empty())
    break;
  T = Queue.pop_back_val();
}
2968}

2970/// Find the associated classes and namespaces for
2971/// argument-dependent lookup for a call with the given set of
2972/// arguments.
2973///
2974/// This routine computes the sets of associated classes and associated
2975/// namespaces searched by argument-dependent lookup
2976/// (C++ [basic.lookup.argdep]) for a given set of arguments.
2977void Sema::FindAssociatedClassesAndNamespaces(
  SourceLocation InstantiationLoc, ArrayRef<Expr *> Args,
  AssociatedNamespaceSet &AssociatedNamespaces,
  AssociatedClassSet &AssociatedClasses) {
AssociatedNamespaces.clear();
AssociatedClasses.clear();

AssociatedLookup Result(*this, InstantiationLoc,
                        AssociatedNamespaces, AssociatedClasses);

// C++ [basic.lookup.koenig]p2:
//   For each argument type T in the function call, there is a set
//   of zero or more associated namespaces and a set of zero or more
//   associated classes to be considered. The sets of namespaces and
//   classes is determined entirely by the types of the function
//   arguments (and the namespace of any template template
//   argument).
for (unsigned ArgIdx = 0; ArgIdx != Args.size(); ++ArgIdx) {
  Expr *Arg = Args[ArgIdx];

  if (Arg->getType() != Context.OverloadTy) {
    addAssociatedClassesAndNamespaces(Result, Arg->getType());
    continue;
  }

  // [...] In addition, if the argument is the name or address of a
  // set of overloaded functions and/or function templates, its
  // associated classes and namespaces are the union of those
  // associated with each of the members of the set: the namespace
  // in which the function or function template is defined and the
  // classes and namespaces associated with its (non-dependent)
  // parameter types and return type.
  OverloadExpr *OE = OverloadExpr::find(Arg).Expression;

  for (const NamedDecl *D : OE->decls()) {
    // Look through any using declarations to find the underlying function.
    const FunctionDecl *FDecl = D->getUnderlyingDecl()->getAsFunction();

    // Add the classes and namespaces associated with the parameter
    // types and return type of this function.
    addAssociatedClassesAndNamespaces(Result, FDecl->getType());
  }
}
3020}

3022NamedDecl *Sema::LookupSingleName(Scope *S, DeclarationName Name,
                                SourceLocation Loc,
                                LookupNameKind NameKind,
                                RedeclarationKind Redecl) {
LookupResult R(*this, Name, Loc, NameKind, Redecl);
LookupName(R, S);
return R.getAsSingle<NamedDecl>();
3029}

3031/// Find the protocol with the given name, if any.
3032ObjCProtocolDecl *Sema::LookupProtocol(IdentifierInfo *II,
                                     SourceLocation IdLoc,
                                     RedeclarationKind Redecl) {
Decl *D = LookupSingleName(TUScope, II, IdLoc,
                           LookupObjCProtocolName, Redecl);
return cast_or_null<ObjCProtocolDecl>(D);
3038}

3040void Sema::LookupOverloadedOperatorName(OverloadedOperatorKind Op, Scope *S,
                                      UnresolvedSetImpl &Functions) {
// C++ [over.match.oper]p3:
//     -- The set of non-member candidates is the result of the
//        unqualified lookup of operator@ in the context of the
//        expression according to the usual rules for name lookup in
//        unqualified function calls (3.4.2) except that all member
//        functions are ignored.
DeclarationName OpName = Context.DeclarationNames.getCXXOperatorName(Op);
LookupResult Operators(*this, OpName, SourceLocation(), LookupOperatorName);
LookupName(Operators, S);

assert(!Operators.isAmbiguous() && "Operator lookup cannot be ambiguous")((void)0);
Functions.append(Operators.begin(), Operators.end());
3054}

3056Sema::SpecialMemberOverloadResult Sema::LookupSpecialMember(CXXRecordDecl *RD,
                                                         CXXSpecialMember SM,
                                                         bool ConstArg,
                                                         bool VolatileArg,
                                                         bool RValueThis,
                                                         bool ConstThis,
                                                         bool VolatileThis) {
assert(CanDeclareSpecialMemberFunction(RD) &&((void)0)
       "doing special member lookup into record that isn't fully complete")((void)0);
RD = RD->getDefinition();
if (RValueThis || ConstThis || VolatileThis)
  assert((SM == CXXCopyAssignment || SM == CXXMoveAssignment) &&((void)0)
         "constructors and destructors always have unqualified lvalue this")((void)0);
if (ConstArg || VolatileArg)
  assert((SM != CXXDefaultConstructor && SM != CXXDestructor) &&((void)0)
         "parameter-less special members can't have qualified arguments")((void)0);

// FIXME: Get the caller to pass in a location for the lookup.
SourceLocation LookupLoc = RD->getLocation();

llvm::FoldingSetNodeID ID;
ID.AddPointer(RD);
ID.AddInteger(SM);
ID.AddInteger(ConstArg);
ID.AddInteger(VolatileArg);
ID.AddInteger(RValueThis);
ID.AddInteger(ConstThis);
ID.AddInteger(VolatileThis);

void *InsertPoint;
SpecialMemberOverloadResultEntry *Result =
  SpecialMemberCache.FindNodeOrInsertPos(ID, InsertPoint);

// This was already cached
if (Result)
  return *Result;

Result = BumpAlloc.Allocate<SpecialMemberOverloadResultEntry>();
Result = new (Result) SpecialMemberOverloadResultEntry(ID);
SpecialMemberCache.InsertNode(Result, InsertPoint);

if (SM == CXXDestructor) {
  if (RD->needsImplicitDestructor()) {
    runWithSufficientStackSpace(RD->getLocation(), [&] {
      DeclareImplicitDestructor(RD);
    });
  }
  CXXDestructorDecl *DD = RD->getDestructor();
  Result->setMethod(DD);
  Result->setKind(DD && !DD->isDeleted()
                      ? SpecialMemberOverloadResult::Success
                      : SpecialMemberOverloadResult::NoMemberOrDeleted);
  return *Result;
}

// Prepare for overload resolution. Here we construct a synthetic argument
// if necessary and make sure that implicit functions are declared.
CanQualType CanTy = Context.getCanonicalType(Context.getTagDeclType(RD));
DeclarationName Name;
Expr *Arg = nullptr;
unsigned NumArgs;

QualType ArgType = CanTy;
ExprValueKind VK = VK_LValue;

if (SM == CXXDefaultConstructor) {
  Name = Context.DeclarationNames.getCXXConstructorName(CanTy);
  NumArgs = 0;
  if (RD->needsImplicitDefaultConstructor()) {
    runWithSufficientStackSpace(RD->getLocation(), [&] {
      DeclareImplicitDefaultConstructor(RD);
    });
  }
} else {
  if (SM == CXXCopyConstructor || SM == CXXMoveConstructor) {
    Name = Context.DeclarationNames.getCXXConstructorName(CanTy);
    if (RD->needsImplicitCopyConstructor()) {
      runWithSufficientStackSpace(RD->getLocation(), [&] {
        DeclareImplicitCopyConstructor(RD);
      });
    }
    if (getLangOpts().CPlusPlus11 && RD->needsImplicitMoveConstructor()) {
      runWithSufficientStackSpace(RD->getLocation(), [&] {
        DeclareImplicitMoveConstructor(RD);
      });
    }
  } else {
    Name = Context.DeclarationNames.getCXXOperatorName(OO_Equal);
    if (RD->needsImplicitCopyAssignment()) {
      runWithSufficientStackSpace(RD->getLocation(), [&] {
        DeclareImplicitCopyAssignment(RD);
      });
    }
    if (getLangOpts().CPlusPlus11 && RD->needsImplicitMoveAssignment()) {
      runWithSufficientStackSpace(RD->getLocation(), [&] {
        DeclareImplicitMoveAssignment(RD);
      });
    }
  }

  if (ConstArg)
    ArgType.addConst();
  if (VolatileArg)
    ArgType.addVolatile();

  // This isn't /really/ specified by the standard, but it's implied
  // we should be working from a PRValue in the case of move to ensure
  // that we prefer to bind to rvalue references, and an LValue in the
  // case of copy to ensure we don't bind to rvalue references.
  // Possibly an XValue is actually correct in the case of move, but
  // there is no semantic difference for class types in this restricted
  // case.
  if (SM == CXXCopyConstructor || SM == CXXCopyAssignment)
    VK = VK_LValue;
  else
    VK = VK_PRValue;
}

OpaqueValueExpr FakeArg(LookupLoc, ArgType, VK);

if (SM != CXXDefaultConstructor) {
  NumArgs = 1;
  Arg = &FakeArg;
}

// Create the object argument
QualType ThisTy = CanTy;
if (ConstThis)
  ThisTy.addConst();
if (VolatileThis)
  ThisTy.addVolatile();
Expr::Classification Classification =
    OpaqueValueExpr(LookupLoc, ThisTy, RValueThis ? VK_PRValue : VK_LValue)
        .Classify(Context);

// Now we perform lookup on the name we computed earlier and do overload
// resolution. Lookup is only performed directly into the class since there
// will always be a (possibly implicit) declaration to shadow any others.
OverloadCandidateSet OCS(LookupLoc, OverloadCandidateSet::CSK_Normal);
DeclContext::lookup_result R = RD->lookup(Name);

if (R.empty()) {
  // We might have no default constructor because we have a lambda's closure
  // type, rather than because there's some other declared constructor.
  // Every class has a copy/move constructor, copy/move assignment, and
  // destructor.
  assert(SM == CXXDefaultConstructor &&((void)0)
         "lookup for a constructor or assignment operator was empty")((void)0);
  Result->setMethod(nullptr);
  Result->setKind(SpecialMemberOverloadResult::NoMemberOrDeleted);
  return *Result;
}

// Copy the candidates as our processing of them may load new declarations
// from an external source and invalidate lookup_result.
SmallVector<NamedDecl *, 8> Candidates(R.begin(), R.end());

for (NamedDecl *CandDecl : Candidates) {
  if (CandDecl->isInvalidDecl())
    continue;

  DeclAccessPair Cand = DeclAccessPair::make(CandDecl, AS_public);
  auto CtorInfo = getConstructorInfo(Cand);
  if (CXXMethodDecl *M = dyn_cast<CXXMethodDecl>(Cand->getUnderlyingDecl())) {
    if (SM == CXXCopyAssignment || SM == CXXMoveAssignment)
      AddMethodCandidate(M, Cand, RD, ThisTy, Classification,
                         llvm::makeArrayRef(&Arg, NumArgs), OCS, true);
    else if (CtorInfo)
      AddOverloadCandidate(CtorInfo.Constructor, CtorInfo.FoundDecl,
                           llvm::makeArrayRef(&Arg, NumArgs), OCS,
                           /*SuppressUserConversions*/ true);
    else
      AddOverloadCandidate(M, Cand, llvm::makeArrayRef(&Arg, NumArgs), OCS,
                           /*SuppressUserConversions*/ true);
  } else if (FunctionTemplateDecl *Tmpl =
               dyn_cast<FunctionTemplateDecl>(Cand->getUnderlyingDecl())) {
    if (SM == CXXCopyAssignment || SM == CXXMoveAssignment)
      AddMethodTemplateCandidate(
          Tmpl, Cand, RD, nullptr, ThisTy, Classification,
          llvm::makeArrayRef(&Arg, NumArgs), OCS, true);
    else if (CtorInfo)
      AddTemplateOverloadCandidate(
          CtorInfo.ConstructorTmpl, CtorInfo.FoundDecl, nullptr,
          llvm::makeArrayRef(&Arg, NumArgs), OCS, true);
    else
      AddTemplateOverloadCandidate(
          Tmpl, Cand, nullptr, llvm::makeArrayRef(&Arg, NumArgs), OCS, true);
  } else {
    assert(isa<UsingDecl>(Cand.getDecl()) &&((void)0)
           "illegal Kind of operator = Decl")((void)0);
  }
}

OverloadCandidateSet::iterator Best;
switch (OCS.BestViableFunction(*this, LookupLoc, Best)) {
  case OR_Success:
    Result->setMethod(cast<CXXMethodDecl>(Best->Function));
    Result->setKind(SpecialMemberOverloadResult::Success);
    break;

  case OR_Deleted:
    Result->setMethod(cast<CXXMethodDecl>(Best->Function));
    Result->setKind(SpecialMemberOverloadResult::NoMemberOrDeleted);
    break;

  case OR_Ambiguous:
    Result->setMethod(nullptr);
    Result->setKind(SpecialMemberOverloadResult::Ambiguous);
    break;

  case OR_No_Viable_Function:
    Result->setMethod(nullptr);
    Result->setKind(SpecialMemberOverloadResult::NoMemberOrDeleted);
    break;
}

return *Result;
3273}

3275/// Look up the default constructor for the given class.
3276CXXConstructorDecl *Sema::LookupDefaultConstructor(CXXRecordDecl *Class) {
SpecialMemberOverloadResult Result =
  LookupSpecialMember(Class, CXXDefaultConstructor, false, false, false,
                      false, false);

return cast_or_null<CXXConstructorDecl>(Result.getMethod());
3282}

3284/// Look up the copying constructor for the given class.
3285CXXConstructorDecl *Sema::LookupCopyingConstructor(CXXRecordDecl *Class,
                                                 unsigned Quals) {
assert(!(Quals & ~(Qualifiers::Const | Qualifiers::Volatile)) &&((void)0)
       "non-const, non-volatile qualifiers for copy ctor arg")((void)0);
SpecialMemberOverloadResult Result =
  LookupSpecialMember(Class, CXXCopyConstructor, Quals & Qualifiers::Const,
                      Quals & Qualifiers::Volatile, false, false, false);

return cast_or_null<CXXConstructorDecl>(Result.getMethod());
3294}

3296/// Look up the moving constructor for the given class.
3297CXXConstructorDecl *Sema::LookupMovingConstructor(CXXRecordDecl *Class,
                                                unsigned Quals) {
SpecialMemberOverloadResult Result =
  LookupSpecialMember(Class, CXXMoveConstructor, Quals & Qualifiers::Const,
                      Quals & Qualifiers::Volatile, false, false, false);

return cast_or_null<CXXConstructorDecl>(Result.getMethod());
3304}

3306/// Look up the constructors for the given class.
3307DeclContext::lookup_result Sema::LookupConstructors(CXXRecordDecl *Class) {
// If the implicit constructors have not yet been declared, do so now.
if (CanDeclareSpecialMemberFunction(Class)) {
  runWithSufficientStackSpace(Class->getLocation(), [&] {
    if (Class->needsImplicitDefaultConstructor())
      DeclareImplicitDefaultConstructor(Class);
    if (Class->needsImplicitCopyConstructor())
      DeclareImplicitCopyConstructor(Class);
    if (getLangOpts().CPlusPlus11 && Class->needsImplicitMoveConstructor())
      DeclareImplicitMoveConstructor(Class);
  });
}

CanQualType T = Context.getCanonicalType(Context.getTypeDeclType(Class));
DeclarationName Name = Context.DeclarationNames.getCXXConstructorName(T);
return Class->lookup(Name);
3323}

3325/// Look up the copying assignment operator for the given class.
3326CXXMethodDecl *Sema::LookupCopyingAssignment(CXXRecordDecl *Class,
                                           unsigned Quals, bool RValueThis,
                                           unsigned ThisQuals) {
assert(!(Quals & ~(Qualifiers::Const | Qualifiers::Volatile)) &&((void)0)
       "non-const, non-volatile qualifiers for copy assignment arg")((void)0);
assert(!(ThisQuals & ~(Qualifiers::Const | Qualifiers::Volatile)) &&((void)0)
       "non-const, non-volatile qualifiers for copy assignment this")((void)0);
SpecialMemberOverloadResult Result =
  LookupSpecialMember(Class, CXXCopyAssignment, Quals & Qualifiers::Const,
                      Quals & Qualifiers::Volatile, RValueThis,
                      ThisQuals & Qualifiers::Const,
                      ThisQuals & Qualifiers::Volatile);

return Result.getMethod();
3340}

3342/// Look up the moving assignment operator for the given class.
3343CXXMethodDecl *Sema::LookupMovingAssignment(CXXRecordDecl *Class,
                                          unsigned Quals,
                                          bool RValueThis,
                                          unsigned ThisQuals) {
assert(!(ThisQuals & ~(Qualifiers::Const | Qualifiers::Volatile)) &&((void)0)
       "non-const, non-volatile qualifiers for copy assignment this")((void)0);
SpecialMemberOverloadResult Result =
  LookupSpecialMember(Class, CXXMoveAssignment, Quals & Qualifiers::Const,
                      Quals & Qualifiers::Volatile, RValueThis,
                      ThisQuals & Qualifiers::Const,
                      ThisQuals & Qualifiers::Volatile);

return Result.getMethod();
3356}

3358/// Look for the destructor of the given class.
3359///
3360/// During semantic analysis, this routine should be used in lieu of
3361/// CXXRecordDecl::getDestructor().
3362///
3363/// \returns The destructor for this class.
3364CXXDestructorDecl *Sema::LookupDestructor(CXXRecordDecl *Class) {
return cast<CXXDestructorDecl>(LookupSpecialMember(Class, CXXDestructor,
                                                   false, false, false,
                                                   false, false).getMethod());
3368}

3370/// LookupLiteralOperator - Determine which literal operator should be used for
3371/// a user-defined literal, per C++11 [lex.ext].
3372///
3373/// Normal overload resolution is not used to select which literal operator to
3374/// call for a user-defined literal. Look up the provided literal operator name,
3375/// and filter the results to the appropriate set for the given argument types.
3376Sema::LiteralOperatorLookupResult
3377Sema::LookupLiteralOperator(Scope *S, LookupResult &R,
                          ArrayRef<QualType> ArgTys, bool AllowRaw,
                          bool AllowTemplate, bool AllowStringTemplatePack,
                          bool DiagnoseMissing, StringLiteral *StringLit) {
LookupName(R, S);
assert(R.getResultKind() != LookupResult::Ambiguous &&((void)0)
       "literal operator lookup can't be ambiguous")((void)0);

// Filter the lookup results appropriately.
LookupResult::Filter F = R.makeFilter();

bool AllowCooked = true;
bool FoundRaw = false;
bool FoundTemplate = false;
bool FoundStringTemplatePack = false;
bool FoundCooked = false;

while (F.hasNext()) {
  Decl *D = F.next();
  if (UsingShadowDecl *USD = dyn_cast<UsingShadowDecl>(D))
    D = USD->getTargetDecl();

  // If the declaration we found is invalid, skip it.
  if (D->isInvalidDecl()) {
    F.erase();
    continue;
  }

  bool IsRaw = false;
  bool IsTemplate = false;
  bool IsStringTemplatePack = false;
  bool IsCooked = false;

  if (FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
    if (FD->getNumParams() == 1 &&
        FD->getParamDecl(0)->getType()->getAs<PointerType>())
      IsRaw = true;
    else if (FD->getNumParams() == ArgTys.size()) {
      IsCooked = true;
      for (unsigned ArgIdx = 0; ArgIdx != ArgTys.size(); ++ArgIdx) {
        QualType ParamTy = FD->getParamDecl(ArgIdx)->getType();
        if (!Context.hasSameUnqualifiedType(ArgTys[ArgIdx], ParamTy)) {
          IsCooked = false;
          break;
        }
      }
    }
  }
  if (FunctionTemplateDecl *FD = dyn_cast<FunctionTemplateDecl>(D)) {
    TemplateParameterList *Params = FD->getTemplateParameters();
    if (Params->size() == 1) {
      IsTemplate = true;
      if (!Params->getParam(0)->isTemplateParameterPack() && !StringLit) {
        // Implied but not stated: user-defined integer and floating literals
        // only ever use numeric literal operator templates, not templates
        // taking a parameter of class type.
        F.erase();
        continue;
      }

      // A string literal template is only considered if the string literal
      // is a well-formed template argument for the template parameter.
      if (StringLit) {
        SFINAETrap Trap(*this);
        SmallVector<TemplateArgument, 1> Checked;
        TemplateArgumentLoc Arg(TemplateArgument(StringLit), StringLit);
        if (CheckTemplateArgument(Params->getParam(0), Arg, FD,
                                  R.getNameLoc(), R.getNameLoc(), 0,
                                  Checked) ||
            Trap.hasErrorOccurred())
          IsTemplate = false;
      }
    } else {
      IsStringTemplatePack = true;
    }
  }

  if (AllowTemplate && StringLit && IsTemplate) {
    FoundTemplate = true;
    AllowRaw = false;
    AllowCooked = false;
    AllowStringTemplatePack = false;
    if (FoundRaw || FoundCooked || FoundStringTemplatePack) {
      F.restart();
      FoundRaw = FoundCooked = FoundStringTemplatePack = false;
    }
  } else if (AllowCooked && IsCooked) {
    FoundCooked = true;
    AllowRaw = false;
    AllowTemplate = StringLit;
    AllowStringTemplatePack = false;
    if (FoundRaw || FoundTemplate || FoundStringTemplatePack) {
      // Go through again and remove the raw and template decls we've
      // already found.
      F.restart();
      FoundRaw = FoundTemplate = FoundStringTemplatePack = false;
    }
  } else if (AllowRaw && IsRaw) {
    FoundRaw = true;
  } else if (AllowTemplate && IsTemplate) {
    FoundTemplate = true;
  } else if (AllowStringTemplatePack && IsStringTemplatePack) {
    FoundStringTemplatePack = true;
  } else {
    F.erase();
  }
}

F.done();

// Per C++20 [lex.ext]p5, we prefer the template form over the non-template
// form for string literal operator templates.
if (StringLit && FoundTemplate)
  return LOLR_Template;

// C++11 [lex.ext]p3, p4: If S contains a literal operator with a matching
// parameter type, that is used in preference to a raw literal operator
// or literal operator template.
if (FoundCooked)
  return LOLR_Cooked;

// C++11 [lex.ext]p3, p4: S shall contain a raw literal operator or a literal
// operator template, but not both.
if (FoundRaw && FoundTemplate) {
  Diag(R.getNameLoc(), diag::err_ovl_ambiguous_call) << R.getLookupName();
  for (LookupResult::iterator I = R.begin(), E = R.end(); I != E; ++I)
    NoteOverloadCandidate(*I, (*I)->getUnderlyingDecl()->getAsFunction());
  return LOLR_Error;
}

if (FoundRaw)
  return LOLR_Raw;

if (FoundTemplate)
  return LOLR_Template;

if (FoundStringTemplatePack)
  return LOLR_StringTemplatePack;

// Didn't find anything we could use.
if (DiagnoseMissing) {
  Diag(R.getNameLoc(), diag::err_ovl_no_viable_literal_operator)
      << R.getLookupName() << (int)ArgTys.size() << ArgTys[0]
      << (ArgTys.size() == 2 ? ArgTys[1] : QualType()) << AllowRaw
      << (AllowTemplate || AllowStringTemplatePack);
  return LOLR_Error;
}

return LOLR_ErrorNoDiagnostic;
3526}

3528void ADLResult::insert(NamedDecl *New) {
NamedDecl *&Old = Decls[cast<NamedDecl>(New->getCanonicalDecl())];

// If we haven't yet seen a decl for this key, or the last decl
// was exactly this one, we're done.
if (Old == nullptr || Old == New) {
  Old = New;
  return;
}

// Otherwise, decide which is a more recent redeclaration.
FunctionDecl *OldFD = Old->getAsFunction();
FunctionDecl *NewFD = New->getAsFunction();

FunctionDecl *Cursor = NewFD;
while (true) {
  Cursor = Cursor->getPreviousDecl();

  // If we got to the end without finding OldFD, OldFD is the newer
  // declaration;  leave things as they are.
  if (!Cursor) return;

  // If we do find OldFD, then NewFD is newer.
  if (Cursor == OldFD) break;

  // Otherwise, keep looking.
}

Old = New;
3557}

3559void Sema::ArgumentDependentLookup(DeclarationName Name, SourceLocation Loc,
                                 ArrayRef<Expr *> Args, ADLResult &Result) {
// Find all of the associated namespaces and classes based on the
// arguments we have.
AssociatedNamespaceSet AssociatedNamespaces;
AssociatedClassSet AssociatedClasses;
FindAssociatedClassesAndNamespaces(Loc, Args,
                                   AssociatedNamespaces,
                                   AssociatedClasses);

// C++ [basic.lookup.argdep]p3:
//   Let X be the lookup set produced by unqualified lookup (3.4.1)
//   and let Y be the lookup set produced by argument dependent
//   lookup (defined as follows). If X contains [...] then Y is
//   empty. Otherwise Y is the set of declarations found in the
//   namespaces associated with the argument types as described
//   below. The set of declarations found by the lookup of the name
//   is the union of X and Y.
//
// Here, we compute Y and add its members to the overloaded
// candidate set.
for (auto *NS : AssociatedNamespaces) {
  //   When considering an associated namespace, the lookup is the
  //   same as the lookup performed when the associated namespace is
  //   used as a qualifier (3.4.3.2) except that:
  //
  //     -- Any using-directives in the associated namespace are
  //        ignored.
  //
  //     -- Any namespace-scope friend functions declared in
  //        associated classes are visible within their respective
  //        namespaces even if they are not visible during an ordinary
  //        lookup (11.4).
  DeclContext::lookup_result R = NS->lookup(Name);
  for (auto *D : R) {
    auto *Underlying = D;
    if (auto *USD = dyn_cast<UsingShadowDecl>(D))
      Underlying = USD->getTargetDecl();

    if (!isa<FunctionDecl>(Underlying) &&
        !isa<FunctionTemplateDecl>(Underlying))
      continue;

    // The declaration is visible to argument-dependent lookup if either
    // it's ordinarily visible or declared as a friend in an associated
    // class.
    bool Visible = false;
    for (D = D->getMostRecentDecl(); D;
         D = cast_or_null<NamedDecl>(D->getPreviousDecl())) {
      if (D->getIdentifierNamespace() & Decl::IDNS_Ordinary) {
        if (isVisible(D)) {
          Visible = true;
          break;
        }
      } else if (D->getFriendObjectKind()) {
        auto *RD = cast<CXXRecordDecl>(D->getLexicalDeclContext());
        if (AssociatedClasses.count(RD) && isVisible(D)) {
          Visible = true;
          break;
        }
      }
    }

    // FIXME: Preserve D as the FoundDecl.
    if (Visible)
      Result.insert(Underlying);
  }
}
3627}

3629//----------------------------------------------------------------------------
3630// Search for all visible declarations.
3631//----------------------------------------------------------------------------
3632VisibleDeclConsumer::~VisibleDeclConsumer() { }

3634bool VisibleDeclConsumer::includeHiddenDecls() const { return false; }

3636namespace {

3638class ShadowContextRAII;

3640class VisibleDeclsRecord {
3641public:
/// An entry in the shadow map, which is optimized to store a
/// single declaration (the common case) but can also store a list
/// of declarations.
typedef llvm::TinyPtrVector<NamedDecl*> ShadowMapEntry;

3647private:
/// A mapping from declaration names to the declarations that have
/// this name within a particular scope.
typedef llvm::DenseMap<DeclarationName, ShadowMapEntry> ShadowMap;

/// A list of shadow maps, which is used to model name hiding.
std::list<ShadowMap> ShadowMaps;

/// The declaration contexts we have already visited.
llvm::SmallPtrSet<DeclContext *, 8> VisitedContexts;

friend class ShadowContextRAII;

3660public:
/// Determine whether we have already visited this context
/// (and, if not, note that we are going to visit that context now).
bool visitedContext(DeclContext *Ctx) {
  return !VisitedContexts.insert(Ctx).second;
}

bool alreadyVisitedContext(DeclContext *Ctx) {
  return VisitedContexts.count(Ctx);
}

/// Determine whether the given declaration is hidden in the
/// current scope.
///
/// \returns the declaration that hides the given declaration, or
/// NULL if no such declaration exists.
NamedDecl *checkHidden(NamedDecl *ND);

/// Add a declaration to the current shadow map.
void add(NamedDecl *ND) {
  ShadowMaps.back()[ND->getDeclName()].push_back(ND);
}
3682};

3684/// RAII object that records when we've entered a shadow context.
3685class ShadowContextRAII {
VisibleDeclsRecord &Visible;

typedef VisibleDeclsRecord::ShadowMap ShadowMap;

3690public:
ShadowContextRAII(VisibleDeclsRecord &Visible) : Visible(Visible) {
  Visible.ShadowMaps.emplace_back();
}

~ShadowContextRAII() {
  Visible.ShadowMaps.pop_back();
}
3698};

3700} // end anonymous namespace

3702NamedDecl *VisibleDeclsRecord::checkHidden(NamedDecl *ND) {
unsigned IDNS = ND->getIdentifierNamespace();
std::list<ShadowMap>::reverse_iterator SM = ShadowMaps.rbegin();
for (std::list<ShadowMap>::reverse_iterator SMEnd = ShadowMaps.rend();
     SM != SMEnd; ++SM) {
  ShadowMap::iterator Pos = SM->find(ND->getDeclName());
  if (Pos == SM->end())
    continue;

  for (auto *D : Pos->second) {
    // A tag declaration does not hide a non-tag declaration.
    if (D->hasTagIdentifierNamespace() &&
        (IDNS & (Decl::IDNS_Member | Decl::IDNS_Ordinary |
                 Decl::IDNS_ObjCProtocol)))
      continue;

    // Protocols are in distinct namespaces from everything else.
    if (((D->getIdentifierNamespace() & Decl::IDNS_ObjCProtocol)
         || (IDNS & Decl::IDNS_ObjCProtocol)) &&
        D->getIdentifierNamespace() != IDNS)
      continue;

    // Functions and function templates in the same scope overload
    // rather than hide.  FIXME: Look for hiding based on function
    // signatures!
    if (D->getUnderlyingDecl()->isFunctionOrFunctionTemplate() &&
        ND->getUnderlyingDecl()->isFunctionOrFunctionTemplate() &&
        SM == ShadowMaps.rbegin())
      continue;

    // A shadow declaration that's created by a resolved using declaration
    // is not hidden by the same using declaration.
    if (isa<UsingShadowDecl>(ND) && isa<UsingDecl>(D) &&
        cast<UsingShadowDecl>(ND)->getIntroducer() == D)
      continue;

    // We've found a declaration that hides this one.
    return D;
  }
}

return nullptr;
3744}

3746namespace {
3747class LookupVisibleHelper {
3748public:
LookupVisibleHelper(VisibleDeclConsumer &Consumer, bool IncludeDependentBases,
                    bool LoadExternal)
    : Consumer(Consumer), IncludeDependentBases(IncludeDependentBases),
      LoadExternal(LoadExternal) {}

void lookupVisibleDecls(Sema &SemaRef, Scope *S, Sema::LookupNameKind Kind,
                        bool IncludeGlobalScope) {
  // Determine the set of using directives available during
  // unqualified name lookup.
  Scope *Initial = S;
  UnqualUsingDirectiveSet UDirs(SemaRef);
  if (SemaRef.getLangOpts().CPlusPlus) {
3
←
Assuming field 'CPlusPlus' is not equal to 0→
4
←
Taking true branch→
    // Find the first namespace or translation-unit scope.
    while (S && !isNamespaceOrTranslationUnitScope(S))
5
←
Assuming 'S' is null→
      S = S->getParent();

    UDirs.visitScopeChain(Initial, S);
6
←
Passing null pointer value via 2nd parameter 'InnermostFileScope'→
7
←
Calling 'UnqualUsingDirectiveSet::visitScopeChain'→
  }
  UDirs.done();

  // Look for visible declarations.
  LookupResult Result(SemaRef, DeclarationName(), SourceLocation(), Kind);
  Result.setAllowHidden(Consumer.includeHiddenDecls());
  if (!IncludeGlobalScope)
    Visited.visitedContext(SemaRef.getASTContext().getTranslationUnitDecl());
  ShadowContextRAII Shadow(Visited);
  lookupInScope(Initial, Result, UDirs);
}

void lookupVisibleDecls(Sema &SemaRef, DeclContext *Ctx,
                        Sema::LookupNameKind Kind, bool IncludeGlobalScope) {
  LookupResult Result(SemaRef, DeclarationName(), SourceLocation(), Kind);
  Result.setAllowHidden(Consumer.includeHiddenDecls());
  if (!IncludeGlobalScope)
    Visited.visitedContext(SemaRef.getASTContext().getTranslationUnitDecl());

  ShadowContextRAII Shadow(Visited);
  lookupInDeclContext(Ctx, Result, /*QualifiedNameLookup=*/true,
                      /*InBaseClass=*/false);
}

3790private:
void lookupInDeclContext(DeclContext *Ctx, LookupResult &Result,
                         bool QualifiedNameLookup, bool InBaseClass) {
  if (!Ctx)
    return;

  // Make sure we don't visit the same context twice.
  if (Visited.visitedContext(Ctx->getPrimaryContext()))
    return;

  Consumer.EnteredContext(Ctx);

  // Outside C++, lookup results for the TU live on identifiers.
  if (isa<TranslationUnitDecl>(Ctx) &&
      !Result.getSema().getLangOpts().CPlusPlus) {
    auto &S = Result.getSema();
    auto &Idents = S.Context.Idents;

    // Ensure all external identifiers are in the identifier table.
    if (LoadExternal)
      if (IdentifierInfoLookup *External =
              Idents.getExternalIdentifierLookup()) {
        std::unique_ptr<IdentifierIterator> Iter(External->getIdentifiers());
        for (StringRef Name = Iter->Next(); !Name.empty();
             Name = Iter->Next())
          Idents.get(Name);
      }

    // Walk all lookup results in the TU for each identifier.
    for (const auto &Ident : Idents) {
      for (auto I = S.IdResolver.begin(Ident.getValue()),
                E = S.IdResolver.end();
           I != E; ++I) {
        if (S.IdResolver.isDeclInScope(*I, Ctx)) {
          if (NamedDecl *ND = Result.getAcceptableDecl(*I)) {
            Consumer.FoundDecl(ND, Visited.checkHidden(ND), Ctx, InBaseClass);
            Visited.add(ND);
          }
        }
      }
    }

    return;
  }

  if (CXXRecordDecl *Class = dyn_cast<CXXRecordDecl>(Ctx))
    Result.getSema().ForceDeclarationOfImplicitMembers(Class);

  llvm::SmallVector<NamedDecl *, 4> DeclsToVisit;
  // We sometimes skip loading namespace-level results (they tend to be huge).
  bool Load = LoadExternal ||
              !(isa<TranslationUnitDecl>(Ctx) || isa<NamespaceDecl>(Ctx));
  // Enumerate all of the results in this context.
  for (DeclContextLookupResult R :
       Load ? Ctx->lookups()
            : Ctx->noload_lookups(/*PreserveInternalState=*/false)) {
    for (auto *D : R) {
      if (auto *ND = Result.getAcceptableDecl(D)) {
        // Rather than visit immediatelly, we put ND into a vector and visit
        // all decls, in order, outside of this loop. The reason is that
        // Consumer.FoundDecl() may invalidate the iterators used in the two
        // loops above.
        DeclsToVisit.push_back(ND);
      }
    }
  }

  for (auto *ND : DeclsToVisit) {
    Consumer.FoundDecl(ND, Visited.checkHidden(ND), Ctx, InBaseClass);
    Visited.add(ND);
  }
  DeclsToVisit.clear();

  // Traverse using directives for qualified name lookup.
  if (QualifiedNameLookup) {
    ShadowContextRAII Shadow(Visited);
    for (auto I : Ctx->using_directives()) {
      if (!Result.getSema().isVisible(I))
        continue;
      lookupInDeclContext(I->getNominatedNamespace(), Result,
                          QualifiedNameLookup, InBaseClass);
    }
  }

  // Traverse the contexts of inherited C++ classes.
  if (CXXRecordDecl *Record = dyn_cast<CXXRecordDecl>(Ctx)) {
    if (!Record->hasDefinition())
      return;

    for (const auto &B : Record->bases()) {
      QualType BaseType = B.getType();

      RecordDecl *RD;
      if (BaseType->isDependentType()) {
        if (!IncludeDependentBases) {
          // Don't look into dependent bases, because name lookup can't look
          // there anyway.
          continue;
        }
        const auto *TST = BaseType->getAs<TemplateSpecializationType>();
        if (!TST)
          continue;
        TemplateName TN = TST->getTemplateName();
        const auto *TD =
            dyn_cast_or_null<ClassTemplateDecl>(TN.getAsTemplateDecl());
        if (!TD)
          continue;
        RD = TD->getTemplatedDecl();
      } else {
        const auto *Record = BaseType->getAs<RecordType>();
        if (!Record)
          continue;
        RD = Record->getDecl();
      }

      // FIXME: It would be nice to be able to determine whether referencing
      // a particular member would be ambiguous. For example, given
      //
      //   struct A { int member; };
      //   struct B { int member; };
      //   struct C : A, B { };
      //
      //   void f(C *c) { c->### }
      //
      // accessing 'member' would result in an ambiguity. However, we
      // could be smart enough to qualify the member with the base
      // class, e.g.,
      //
      //   c->B::member
      //
      // or
      //
      //   c->A::member

      // Find results in this base class (and its bases).
      ShadowContextRAII Shadow(Visited);
      lookupInDeclContext(RD, Result, QualifiedNameLookup,
                          /*InBaseClass=*/true);
    }
  }

  // Traverse the contexts of Objective-C classes.
  if (ObjCInterfaceDecl *IFace = dyn_cast<ObjCInterfaceDecl>(Ctx)) {
    // Traverse categories.
    for (auto *Cat : IFace->visible_categories()) {
      ShadowContextRAII Shadow(Visited);
      lookupInDeclContext(Cat, Result, QualifiedNameLookup,
                          /*InBaseClass=*/false);
    }

    // Traverse protocols.
    for (auto *I : IFace->all_referenced_protocols()) {
      ShadowContextRAII Shadow(Visited);
      lookupInDeclContext(I, Result, QualifiedNameLookup,
                          /*InBaseClass=*/false);
    }

    // Traverse the superclass.
    if (IFace->getSuperClass()) {
      ShadowContextRAII Shadow(Visited);
      lookupInDeclContext(IFace->getSuperClass(), Result, QualifiedNameLookup,
                          /*InBaseClass=*/true);
    }

    // If there is an implementation, traverse it. We do this to find
    // synthesized ivars.
    if (IFace->getImplementation()) {
      ShadowContextRAII Shadow(Visited);
      lookupInDeclContext(IFace->getImplementation(), Result,
                          QualifiedNameLookup, InBaseClass);
    }
  } else if (ObjCProtocolDecl *Protocol = dyn_cast<ObjCProtocolDecl>(Ctx)) {
    for (auto *I : Protocol->protocols()) {
      ShadowContextRAII Shadow(Visited);
      lookupInDeclContext(I, Result, QualifiedNameLookup,
                          /*InBaseClass=*/false);
    }
  } else if (ObjCCategoryDecl *Category = dyn_cast<ObjCCategoryDecl>(Ctx)) {
    for (auto *I : Category->protocols()) {
      ShadowContextRAII Shadow(Visited);
      lookupInDeclContext(I, Result, QualifiedNameLookup,
                          /*InBaseClass=*/false);
    }

    // If there is an implementation, traverse it.
    if (Category->getImplementation()) {
      ShadowContextRAII Shadow(Visited);
      lookupInDeclContext(Category->getImplementation(), Result,
                          QualifiedNameLookup, /*InBaseClass=*/true);
    }
  }
}

void lookupInScope(Scope *S, LookupResult &Result,
                   UnqualUsingDirectiveSet &UDirs) {
  // No clients run in this mode and it's not supported. Please add tests and
  // remove the assertion if you start relying on it.
  assert(!IncludeDependentBases && "Unsupported flag for lookupInScope")((void)0);

  if (!S)
    return;

  if (!S->getEntity() ||
      (!S->getParent() && !Visited.alreadyVisitedContext(S->getEntity())) ||
      (S->getEntity())->isFunctionOrMethod()) {
    FindLocalExternScope FindLocals(Result);
    // Walk through the declarations in this Scope. The consumer might add new
    // decls to the scope as part of deserialization, so make a copy first.
    SmallVector<Decl *, 8> ScopeDecls(S->decls().begin(), S->decls().end());
    for (Decl *D : ScopeDecls) {
      if (NamedDecl *ND = dyn_cast<NamedDecl>(D))
        if ((ND = Result.getAcceptableDecl(ND))) {
          Consumer.FoundDecl(ND, Visited.checkHidden(ND), nullptr, false);
          Visited.add(ND);
        }
    }
  }

  DeclContext *Entity = S->getLookupEntity();
  if (Entity) {
    // Look into this scope's declaration context, along with any of its
    // parent lookup contexts (e.g., enclosing classes), up to the point
    // where we hit the context stored in the next outer scope.
    DeclContext *OuterCtx = findOuterContext(S);

    for (DeclContext *Ctx = Entity; Ctx && !Ctx->Equals(OuterCtx);
         Ctx = Ctx->getLookupParent()) {
      if (ObjCMethodDecl *Method = dyn_cast<ObjCMethodDecl>(Ctx)) {
        if (Method->isInstanceMethod()) {
          // For instance methods, look for ivars in the method's interface.
          LookupResult IvarResult(Result.getSema(), Result.getLookupName(),
                                  Result.getNameLoc(),
                                  Sema::LookupMemberName);
          if (ObjCInterfaceDecl *IFace = Method->getClassInterface()) {
            lookupInDeclContext(IFace, IvarResult,
                                /*QualifiedNameLookup=*/false,
                                /*InBaseClass=*/false);
          }
        }

        // We've already performed all of the name lookup that we need
        // to for Objective-C methods; the next context will be the
        // outer scope.
        break;
      }

      if (Ctx->isFunctionOrMethod())
        continue;

      lookupInDeclContext(Ctx, Result, /*QualifiedNameLookup=*/false,
                          /*InBaseClass=*/false);
    }
  } else if (!S->getParent()) {
    // Look into the translation unit scope. We walk through the translation
    // unit's declaration context, because the Scope itself won't have all of
    // the declarations if we loaded a precompiled header.
    // FIXME: We would like the translation unit's Scope object to point to
    // the translation unit, so we don't need this special "if" branch.
    // However, doing so would force the normal C++ name-lookup code to look
    // into the translation unit decl when the IdentifierInfo chains would
    // suffice. Once we fix that problem (which is part of a more general
    // "don't look in DeclContexts unless we have to" optimization), we can
    // eliminate this.
    Entity = Result.getSema().Context.getTranslationUnitDecl();
    lookupInDeclContext(Entity, Result, /*QualifiedNameLookup=*/false,
                        /*InBaseClass=*/false);
  }

  if (Entity) {
    // Lookup visible declarations in any namespaces found by using
    // directives.
    for (const UnqualUsingEntry &UUE : UDirs.getNamespacesFor(Entity))
      lookupInDeclContext(
          const_cast<DeclContext *>(UUE.getNominatedNamespace()), Result,
          /*QualifiedNameLookup=*/false,
          /*InBaseClass=*/false);
  }

  // Lookup names in the parent scope.
  ShadowContextRAII Shadow(Visited);
  lookupInScope(S->getParent(), Result, UDirs);
}

4073private:
VisibleDeclsRecord Visited;
VisibleDeclConsumer &Consumer;
bool IncludeDependentBases;
bool LoadExternal;
4078};
4079} // namespace

4081void Sema::LookupVisibleDecls(Scope *S, LookupNameKind Kind,
                            VisibleDeclConsumer &Consumer,
                            bool IncludeGlobalScope, bool LoadExternal) {
LookupVisibleHelper H(Consumer, /*IncludeDependentBases=*/false,
                      LoadExternal);
H.lookupVisibleDecls(*this, S, Kind, IncludeGlobalScope);
1
Passing value via 2nd parameter 'S'→
2
←
Calling 'LookupVisibleHelper::lookupVisibleDecls'→
4087}

4089void Sema::LookupVisibleDecls(DeclContext *Ctx, LookupNameKind Kind,
                            VisibleDeclConsumer &Consumer,
                            bool IncludeGlobalScope,
                            bool IncludeDependentBases, bool LoadExternal) {
LookupVisibleHelper H(Consumer, IncludeDependentBases, LoadExternal);
H.lookupVisibleDecls(*this, Ctx, Kind, IncludeGlobalScope);
4095}

4097/// LookupOrCreateLabel - Do a name lookup of a label with the specified name.
4098/// If GnuLabelLoc is a valid source location, then this is a definition
4099/// of an __label__ label name, otherwise it is a normal label definition
4100/// or use.
4101LabelDecl *Sema::LookupOrCreateLabel(IdentifierInfo *II, SourceLocation Loc,
                                   SourceLocation GnuLabelLoc) {
// Do a lookup to see if we have a label with this name already.
NamedDecl *Res = nullptr;

if (GnuLabelLoc.isValid()) {
  // Local label definitions always shadow existing labels.
  Res = LabelDecl::Create(Context, CurContext, Loc, II, GnuLabelLoc);
  Scope *S = CurScope;
  PushOnScopeChains(Res, S, true);
  return cast<LabelDecl>(Res);
}

// Not a GNU local label.
Res = LookupSingleName(CurScope, II, Loc, LookupLabel, NotForRedeclaration);
// If we found a label, check to see if it is in the same context as us.
// When in a Block, we don't want to reuse a label in an enclosing function.
if (Res && Res->getDeclContext() != CurContext)
  Res = nullptr;
if (!Res) {
  // If not forward referenced or defined already, create the backing decl.
  Res = LabelDecl::Create(Context, CurContext, Loc, II);
  Scope *S = CurScope->getFnParent();
  assert(S && "Not in a function?")((void)0);
  PushOnScopeChains(Res, S, true);
}
return cast<LabelDecl>(Res);
4128}

4130//===----------------------------------------------------------------------===//
4131// Typo correction
4132//===----------------------------------------------------------------------===//

4134static bool isCandidateViable(CorrectionCandidateCallback &CCC,
                            TypoCorrection &Candidate) {
Candidate.setCallbackDistance(CCC.RankCandidate(Candidate));
return Candidate.getEditDistance(false) != TypoCorrection::InvalidDistance;
4138}

4140static void LookupPotentialTypoResult(Sema &SemaRef,
                                    LookupResult &Res,
                                    IdentifierInfo *Name,
                                    Scope *S, CXXScopeSpec *SS,
                                    DeclContext *MemberContext,
                                    bool EnteringContext,
                                    bool isObjCIvarLookup,
                                    bool FindHidden);

4149/// Check whether the declarations found for a typo correction are
4150/// visible. Set the correction's RequiresImport flag to true if none of the
4151/// declarations are visible, false otherwise.
4152static void checkCorrectionVisibility(Sema &SemaRef, TypoCorrection &TC) {
TypoCorrection::decl_iterator DI = TC.begin(), DE = TC.end();

for (/**/; DI != DE; ++DI)
  if (!LookupResult::isVisible(SemaRef, *DI))
    break;
// No filtering needed if all decls are visible.
if (DI == DE) {
  TC.setRequiresImport(false);
  return;
}

llvm::SmallVector<NamedDecl*, 4> NewDecls(TC.begin(), DI);
bool AnyVisibleDecls = !NewDecls.empty();

for (/**/; DI != DE; ++DI) {
  if (LookupResult::isVisible(SemaRef, *DI)) {
    if (!AnyVisibleDecls) {
      // Found a visible decl, discard all hidden ones.
      AnyVisibleDecls = true;
      NewDecls.clear();
    }
    NewDecls.push_back(*DI);
  } else if (!AnyVisibleDecls && !(*DI)->isModulePrivate())
    NewDecls.push_back(*DI);
}

if (NewDecls.empty())
  TC = TypoCorrection();
else {
  TC.setCorrectionDecls(NewDecls);
  TC.setRequiresImport(!AnyVisibleDecls);
}
4185}

4187// Fill the supplied vector with the IdentifierInfo pointers for each piece of
4188// the given NestedNameSpecifier (i.e. given a NestedNameSpecifier "foo::bar::",
4189// fill the vector with the IdentifierInfo pointers for "foo" and "bar").
4190static void getNestedNameSpecifierIdentifiers(
  NestedNameSpecifier *NNS,
  SmallVectorImpl<const IdentifierInfo*> &Identifiers) {
if (NestedNameSpecifier *Prefix = NNS->getPrefix())
  getNestedNameSpecifierIdentifiers(Prefix, Identifiers);
else
  Identifiers.clear();

const IdentifierInfo *II = nullptr;

switch (NNS->getKind()) {
case NestedNameSpecifier::Identifier:
  II = NNS->getAsIdentifier();
  break;

case NestedNameSpecifier::Namespace:
  if (NNS->getAsNamespace()->isAnonymousNamespace())
    return;
  II = NNS->getAsNamespace()->getIdentifier();
  break;

case NestedNameSpecifier::NamespaceAlias:
  II = NNS->getAsNamespaceAlias()->getIdentifier();
  break;

case NestedNameSpecifier::TypeSpecWithTemplate:
case NestedNameSpecifier::TypeSpec:
  II = QualType(NNS->getAsType(), 0).getBaseTypeIdentifier();
  break;

case NestedNameSpecifier::Global:
case NestedNameSpecifier::Super:
  return;
}

if (II)
  Identifiers.push_back(II);
4227}

4229void TypoCorrectionConsumer::FoundDecl(NamedDecl *ND, NamedDecl *Hiding,
                                     DeclContext *Ctx, bool InBaseClass) {
// Don't consider hidden names for typo correction.
if (Hiding)
  return;

// Only consider entities with identifiers for names, ignoring
// special names (constructors, overloaded operators, selectors,
// etc.).
IdentifierInfo *Name = ND->getIdentifier();
if (!Name)
  return;

// Only consider visible declarations and declarations from modules with
// names that exactly match.
if (!LookupResult::isVisible(SemaRef, ND) && Name != Typo)
  return;

FoundName(Name->getName());
4248}

4250void TypoCorrectionConsumer::FoundName(StringRef Name) {
// Compute the edit distance between the typo and the name of this
// entity, and add the identifier to the list of results.
addName(Name, nullptr);
4254}

4256void TypoCorrectionConsumer::addKeywordResult(StringRef Keyword) {
// Compute the edit distance between the typo and this keyword,
// and add the keyword to the list of results.
addName(Keyword, nullptr, nullptr, true);
4260}

4262void TypoCorrectionConsumer::addName(StringRef Name, NamedDecl *ND,
                                   NestedNameSpecifier *NNS, bool isKeyword) {
// Use a simple length-based heuristic to determine the minimum possible
// edit distance. If the minimum isn't good enough, bail out early.
StringRef TypoStr = Typo->getName();
unsigned MinED = abs((int)Name.size() - (int)TypoStr.size());
if (MinED && TypoStr.size() / MinED < 3)
  return;

// Compute an upper bound on the allowable edit distance, so that the
// edit-distance algorithm can short-circuit.
unsigned UpperBound = (TypoStr.size() + 2) / 3;
unsigned ED = TypoStr.edit_distance(Name, true, UpperBound);
if (ED > UpperBound) return;

TypoCorrection TC(&SemaRef.Context.Idents.get(Name), ND, NNS, ED);
if (isKeyword) TC.makeKeyword();
TC.setCorrectionRange(nullptr, Result.getLookupNameInfo());
addCorrection(TC);
4281}

4283static const unsigned MaxTypoDistanceResultSets = 5;

4285void TypoCorrectionConsumer::addCorrection(TypoCorrection Correction) {
StringRef TypoStr = Typo->getName();
StringRef Name = Correction.getCorrectionAsIdentifierInfo()->getName();

// For very short typos, ignore potential corrections that have a different
// base identifier from the typo or which have a normalized edit distance
// longer than the typo itself.
if (TypoStr.size() < 3 &&
    (Name != TypoStr || Correction.getEditDistance(true) > TypoStr.size()))
  return;

// If the correction is resolved but is not viable, ignore it.
if (Correction.isResolved()) {
  checkCorrectionVisibility(SemaRef, Correction);
  if (!Correction || !isCandidateViable(*CorrectionValidator, Correction))
    return;
}

TypoResultList &CList =
    CorrectionResults[Correction.getEditDistance(false)][Name];

if (!CList.empty() && !CList.back().isResolved())
  CList.pop_back();
if (NamedDecl *NewND = Correction.getCorrectionDecl()) {
  std::string CorrectionStr = Correction.getAsString(SemaRef.getLangOpts());
  for (TypoResultList::iterator RI = CList.begin(), RIEnd = CList.end();
       RI != RIEnd; ++RI) {
    // If the Correction refers to a decl already in the result list,
    // replace the existing result if the string representation of Correction
    // comes before the current result alphabetically, then stop as there is
    // nothing more to be done to add Correction to the candidate set.
    if (RI->getCorrectionDecl() == NewND) {
      if (CorrectionStr < RI->getAsString(SemaRef.getLangOpts()))
        *RI = Correction;
      return;
    }
  }
}
if (CList.empty() || Correction.isResolved())
  CList.push_back(Correction);

while (CorrectionResults.size() > MaxTypoDistanceResultSets)
  CorrectionResults.erase(std::prev(CorrectionResults.end()));
4328}

4330void TypoCorrectionConsumer::addNamespaces(
  const llvm::MapVector<NamespaceDecl *, bool> &KnownNamespaces) {
SearchNamespaces = true;

for (auto KNPair : KnownNamespaces)
  Namespaces.addNameSpecifier(KNPair.first);

bool SSIsTemplate = false;
if (NestedNameSpecifier *NNS =
        (SS && SS->isValid()) ? SS->getScopeRep() : nullptr) {
  if (const Type *T = NNS->getAsType())
    SSIsTemplate = T->getTypeClass() == Type::TemplateSpecialization;
}
// Do not transform this into an iterator-based loop. The loop body can
// trigger the creation of further types (through lazy deserialization) and
// invalid iterators into this list.
auto &Types = SemaRef.getASTContext().getTypes();
for (unsigned I = 0; I != Types.size(); ++I) {
  const auto *TI = Types[I];
  if (CXXRecordDecl *CD = TI->getAsCXXRecordDecl()) {
    CD = CD->getCanonicalDecl();
    if (!CD->isDependentType() && !CD->isAnonymousStructOrUnion() &&
        !CD->isUnion() && CD->getIdentifier() &&
        (SSIsTemplate || !isa<ClassTemplateSpecializationDecl>(CD)) &&
        (CD->isBeingDefined() || CD->isCompleteDefinition()))
      Namespaces.addNameSpecifier(CD);
  }
}
4358}

4360const TypoCorrection &TypoCorrectionConsumer::getNextCorrection() {
if (++CurrentTCIndex < ValidatedCorrections.size())
  return ValidatedCorrections[CurrentTCIndex];

CurrentTCIndex = ValidatedCorrections.size();
while (!CorrectionResults.empty()) {
  auto DI = CorrectionResults.begin();
  if (DI->second.empty()) {
    CorrectionResults.erase(DI);
    continue;
  }

  auto RI = DI->second.begin();
  if (RI->second.empty()) {
    DI->second.erase(RI);
    performQualifiedLookups();
    continue;
  }

  TypoCorrection TC = RI->second.pop_back_val();
  if (TC.isResolved() || TC.requiresImport() || resolveCorrection(TC)) {
    ValidatedCorrections.push_back(TC);
    return ValidatedCorrections[CurrentTCIndex];
  }
}
return ValidatedCorrections[0];  // The empty correction.
4386}

4388bool TypoCorrectionConsumer::resolveCorrection(TypoCorrection &Candidate) {
IdentifierInfo *Name = Candidate.getCorrectionAsIdentifierInfo();
DeclContext *TempMemberContext = MemberContext;
CXXScopeSpec *TempSS = SS.get();
4392retry_lookup:
LookupPotentialTypoResult(SemaRef, Result, Name, S, TempSS, TempMemberContext,
                          EnteringContext,
                          CorrectionValidator->IsObjCIvarLookup,
                          Name == Typo && !Candidate.WillReplaceSpecifier());
switch (Result.getResultKind()) {
case LookupResult::NotFound:
case LookupResult::NotFoundInCurrentInstantiation:
case LookupResult::FoundUnresolvedValue:
  if (TempSS) {
    // Immediately retry the lookup without the given CXXScopeSpec
    TempSS = nullptr;
    Candidate.WillReplaceSpecifier(true);
    goto retry_lookup;
  }
  if (TempMemberContext) {
    if (SS && !TempSS)
      TempSS = SS.get();
    TempMemberContext = nullptr;
    goto retry_lookup;
  }
  if (SearchNamespaces)
    QualifiedResults.push_back(Candidate);
  break;

case LookupResult::Ambiguous:
  // We don't deal with ambiguities.
  break;

case LookupResult::Found:
case LookupResult::FoundOverloaded:
  // Store all of the Decls for overloaded symbols
  for (auto *TRD : Result)
    Candidate.addCorrectionDecl(TRD);
  checkCorrectionVisibility(SemaRef, Candidate);
  if (!isCandidateViable(*CorrectionValidator, Candidate)) {
    if (SearchNamespaces)
      QualifiedResults.push_back(Candidate);
    break;
  }
  Candidate.setCorrectionRange(SS.get(), Result.getLookupNameInfo());
  return true;
}
return false;
4436}

4438void TypoCorrectionConsumer::performQualifiedLookups() {
unsigned TypoLen = Typo->getName().size();
for (const TypoCorrection &QR : QualifiedResults) {
  for (const auto &NSI : Namespaces) {
    DeclContext *Ctx = NSI.DeclCtx;
    const Type *NSType = NSI.NameSpecifier->getAsType();

    // If the current NestedNameSpecifier refers to a class and the
    // current correction candidate is the name of that class, then skip
    // it as it is unlikely a qualified version of the class' constructor
    // is an appropriate correction.
    if (CXXRecordDecl *NSDecl = NSType ? NSType->getAsCXXRecordDecl() :
                                         nullptr) {
      if (NSDecl->getIdentifier() == QR.getCorrectionAsIdentifierInfo())
        continue;
    }

    TypoCorrection TC(QR);
    TC.ClearCorrectionDecls();
    TC.setCorrectionSpecifier(NSI.NameSpecifier);
    TC.setQualifierDistance(NSI.EditDistance);
    TC.setCallbackDistance(0); // Reset the callback distance

    // If the current correction candidate and namespace combination are
    // too far away from the original typo based on the normalized edit
    // distance, then skip performing a qualified name lookup.
    unsigned TmpED = TC.getEditDistance(true);
    if (QR.getCorrectionAsIdentifierInfo() != Typo && TmpED &&
        TypoLen / TmpED < 3)
      continue;

    Result.clear();
    Result.setLookupName(QR.getCorrectionAsIdentifierInfo());
    if (!SemaRef.LookupQualifiedName(Result, Ctx))
      continue;

    // Any corrections added below will be validated in subsequent
    // iterations of the main while() loop over the Consumer's contents.
    switch (Result.getResultKind()) {
    case LookupResult::Found:
    case LookupResult::FoundOverloaded: {
      if (SS && SS->isValid()) {
        std::string NewQualified = TC.getAsString(SemaRef.getLangOpts());
        std::string OldQualified;
        llvm::raw_string_ostream OldOStream(OldQualified);
        SS->getScopeRep()->print(OldOStream, SemaRef.getPrintingPolicy());
        OldOStream << Typo->getName();
        // If correction candidate would be an identical written qualified
        // identifier, then the existing CXXScopeSpec probably included a
        // typedef that didn't get accounted for properly.
        if (OldOStream.str() == NewQualified)
          break;
      }
      for (LookupResult::iterator TRD = Result.begin(), TRDEnd = Result.end();
           TRD != TRDEnd; ++TRD) {
        if (SemaRef.CheckMemberAccess(TC.getCorrectionRange().getBegin(),
                                      NSType ? NSType->getAsCXXRecordDecl()
                                             : nullptr,
                                      TRD.getPair()) == Sema::AR_accessible)
          TC.addCorrectionDecl(*TRD);
      }
      if (TC.isResolved()) {
        TC.setCorrectionRange(SS.get(), Result.getLookupNameInfo());
        addCorrection(TC);
      }
      break;
    }
    case LookupResult::NotFound:
    case LookupResult::NotFoundInCurrentInstantiation:
    case LookupResult::Ambiguous:
    case LookupResult::FoundUnresolvedValue:
      break;
    }
  }
}
QualifiedResults.clear();
4514}

4516TypoCorrectionConsumer::NamespaceSpecifierSet::NamespaceSpecifierSet(
  ASTContext &Context, DeclContext *CurContext, CXXScopeSpec *CurScopeSpec)
  : Context(Context), CurContextChain(buildContextChain(CurContext)) {
if (NestedNameSpecifier *NNS =
        CurScopeSpec ? CurScopeSpec->getScopeRep() : nullptr) {
  llvm::raw_string_ostream SpecifierOStream(CurNameSpecifier);
  NNS->print(SpecifierOStream, Context.getPrintingPolicy());

  getNestedNameSpecifierIdentifiers(NNS, CurNameSpecifierIdentifiers);
}
// Build the list of identifiers that would be used for an absolute
// (from the global context) NestedNameSpecifier referring to the current
// context.
for (DeclContext *C : llvm::reverse(CurContextChain)) {
  if (auto *ND = dyn_cast_or_null<NamespaceDecl>(C))
    CurContextIdentifiers.push_back(ND->getIdentifier());
}

// Add the global context as a NestedNameSpecifier
SpecifierInfo SI = {cast<DeclContext>(Context.getTranslationUnitDecl()),
                    NestedNameSpecifier::GlobalSpecifier(Context), 1};
DistanceMap[1].push_back(SI);
4538}

4540auto TypoCorrectionConsumer::NamespaceSpecifierSet::buildContextChain(
  DeclContext *Start) -> DeclContextList {
assert(Start && "Building a context chain from a null context")((void)0);
DeclContextList Chain;
for (DeclContext *DC = Start->getPrimaryContext(); DC != nullptr;
     DC = DC->getLookupParent()) {
  NamespaceDecl *ND = dyn_cast_or_null<NamespaceDecl>(DC);
  if (!DC->isInlineNamespace() && !DC->isTransparentContext() &&
      !(ND && ND->isAnonymousNamespace()))
    Chain.push_back(DC->getPrimaryContext());
}
return Chain;
4552}

4554unsigned
4555TypoCorrectionConsumer::NamespaceSpecifierSet::buildNestedNameSpecifier(
  DeclContextList &DeclChain, NestedNameSpecifier *&NNS) {
unsigned NumSpecifiers = 0;
for (DeclContext *C : llvm::reverse(DeclChain)) {
  if (auto *ND = dyn_cast_or_null<NamespaceDecl>(C)) {
    NNS = NestedNameSpecifier::Create(Context, NNS, ND);
    ++NumSpecifiers;
  } else if (auto *RD = dyn_cast_or_null<RecordDecl>(C)) {
    NNS = NestedNameSpecifier::Create(Context, NNS, RD->isTemplateDecl(),
                                      RD->getTypeForDecl());
    ++NumSpecifiers;
  }
}
return NumSpecifiers;
4569}

4571void TypoCorrectionConsumer::NamespaceSpecifierSet::addNameSpecifier(
  DeclContext *Ctx) {
NestedNameSpecifier *NNS = nullptr;
unsigned NumSpecifiers = 0;
DeclContextList NamespaceDeclChain(buildContextChain(Ctx));
DeclContextList FullNamespaceDeclChain(NamespaceDeclChain);

// Eliminate common elements from the two DeclContext chains.
for (DeclContext *C : llvm::reverse(CurContextChain)) {
  if (NamespaceDeclChain.empty() || NamespaceDeclChain.back() != C)
    break;
  NamespaceDeclChain.pop_back();
}

// Build the NestedNameSpecifier from what is left of the NamespaceDeclChain
NumSpecifiers = buildNestedNameSpecifier(NamespaceDeclChain, NNS);

// Add an explicit leading '::' specifier if needed.
if (NamespaceDeclChain.empty()) {
  // Rebuild the NestedNameSpecifier as a globally-qualified specifier.
  NNS = NestedNameSpecifier::GlobalSpecifier(Context);
  NumSpecifiers =
      buildNestedNameSpecifier(FullNamespaceDeclChain, NNS);
} else if (NamedDecl *ND =
               dyn_cast_or_null<NamedDecl>(NamespaceDeclChain.back())) {
  IdentifierInfo *Name = ND->getIdentifier();
  bool SameNameSpecifier = false;
  if (std::find(CurNameSpecifierIdentifiers.begin(),
                CurNameSpecifierIdentifiers.end(),
                Name) != CurNameSpecifierIdentifiers.end()) {
    std::string NewNameSpecifier;
    llvm::raw_string_ostream SpecifierOStream(NewNameSpecifier);
    SmallVector<const IdentifierInfo *, 4> NewNameSpecifierIdentifiers;
    getNestedNameSpecifierIdentifiers(NNS, NewNameSpecifierIdentifiers);
    NNS->print(SpecifierOStream, Context.getPrintingPolicy());
    SpecifierOStream.flush();
    SameNameSpecifier = NewNameSpecifier == CurNameSpecifier;
  }
  if (SameNameSpecifier || llvm::find(CurContextIdentifiers, Name) !=
                               CurContextIdentifiers.end()) {
    // Rebuild the NestedNameSpecifier as a globally-qualified specifier.
    NNS = NestedNameSpecifier::GlobalSpecifier(Context);
    NumSpecifiers =
        buildNestedNameSpecifier(FullNamespaceDeclChain, NNS);
  }
}

// If the built NestedNameSpecifier would be replacing an existing
// NestedNameSpecifier, use the number of component identifiers that
// would need to be changed as the edit distance instead of the number
// of components in the built NestedNameSpecifier.
if (NNS && !CurNameSpecifierIdentifiers.empty()) {
  SmallVector<const IdentifierInfo*, 4> NewNameSpecifierIdentifiers;
  getNestedNameSpecifierIdentifiers(NNS, NewNameSpecifierIdentifiers);
  NumSpecifiers = llvm::ComputeEditDistance(
      llvm::makeArrayRef(CurNameSpecifierIdentifiers),
      llvm::makeArrayRef(NewNameSpecifierIdentifiers));
}

SpecifierInfo SI = {Ctx, NNS, NumSpecifiers};
DistanceMap[NumSpecifiers].push_back(SI);
4632}

4634/// Perform name lookup for a possible result for typo correction.
4635static void LookupPotentialTypoResult(Sema &SemaRef,
                                    LookupResult &Res,
                                    IdentifierInfo *Name,
                                    Scope *S, CXXScopeSpec *SS,
                                    DeclContext *MemberContext,
                                    bool EnteringContext,
                                    bool isObjCIvarLookup,
                                    bool FindHidden) {
Res.suppressDiagnostics();
Res.clear();
Res.setLookupName(Name);
Res.setAllowHidden(FindHidden);
if (MemberContext) {
  if (ObjCInterfaceDecl *Class = dyn_cast<ObjCInterfaceDecl>(MemberContext)) {
    if (isObjCIvarLookup) {
      if (ObjCIvarDecl *Ivar = Class->lookupInstanceVariable(Name)) {
        Res.addDecl(Ivar);
        Res.resolveKind();
        return;
      }
    }

    if (ObjCPropertyDecl *Prop = Class->FindPropertyDeclaration(
            Name, ObjCPropertyQueryKind::OBJC_PR_query_instance)) {
      Res.addDecl(Prop);
      Res.resolveKind();
      return;
    }
  }

  SemaRef.LookupQualifiedName(Res, MemberContext);
  return;
}

SemaRef.LookupParsedName(Res, S, SS, /*AllowBuiltinCreation=*/false,
                         EnteringContext);

// Fake ivar lookup; this should really be part of
// LookupParsedName.
if (ObjCMethodDecl *Method = SemaRef.getCurMethodDecl()) {
  if (Method->isInstanceMethod() && Method->getClassInterface() &&
      (Res.empty() ||
       (Res.isSingleResult() &&
        Res.getFoundDecl()->isDefinedOutsideFunctionOrMethod()))) {
     if (ObjCIvarDecl *IV
           = Method->getClassInterface()->lookupInstanceVariable(Name)) {
       Res.addDecl(IV);
       Res.resolveKind();
     }
   }
}
4686}

4688/// Add keywords to the consumer as possible typo corrections.
4689static void AddKeywordsToConsumer(Sema &SemaRef,
                                TypoCorrectionConsumer &Consumer,
                                Scope *S, CorrectionCandidateCallback &CCC,
                                bool AfterNestedNameSpecifier) {
if (AfterNestedNameSpecifier) {
  // For 'X::', we know exactly which keywords can appear next.
  Consumer.addKeywordResult("template");
  if (CCC.WantExpressionKeywords)
    Consumer.addKeywordResult("operator");
  return;
}

if (CCC.WantObjCSuper)
  Consumer.addKeywordResult("super");

if (CCC.WantTypeSpecifiers) {
  // Add type-specifier keywords to the set of results.
  static const char *const CTypeSpecs[] = {
    "char", "const", "double", "enum", "float", "int", "long", "short",
    "signed", "struct", "union", "unsigned", "void", "volatile",
    "_Complex", "_Imaginary",
    // storage-specifiers as well
    "extern", "inline", "static", "typedef"
  };

  const unsigned NumCTypeSpecs = llvm::array_lengthof(CTypeSpecs);
  for (unsigned I = 0; I != NumCTypeSpecs; ++I)
    Consumer.addKeywordResult(CTypeSpecs[I]);

  if (SemaRef.getLangOpts().C99)
    Consumer.addKeywordResult("restrict");
  if (SemaRef.getLangOpts().Bool || SemaRef.getLangOpts().CPlusPlus)
    Consumer.addKeywordResult("bool");
  else if (SemaRef.getLangOpts().C99)
    Consumer.addKeywordResult("_Bool");

  if (SemaRef.getLangOpts().CPlusPlus) {
    Consumer.addKeywordResult("class");
    Consumer.addKeywordResult("typename");
    Consumer.addKeywordResult("wchar_t");

    if (SemaRef.getLangOpts().CPlusPlus11) {
      Consumer.addKeywordResult("char16_t");
      Consumer.addKeywordResult("char32_t");
      Consumer.addKeywordResult("constexpr");
      Consumer.addKeywordResult("decltype");
      Consumer.addKeywordResult("thread_local");
    }
  }

  if (SemaRef.getLangOpts().GNUKeywords)
    Consumer.addKeywordResult("typeof");
} else if (CCC.WantFunctionLikeCasts) {
  static const char *const CastableTypeSpecs[] = {
    "char", "double", "float", "int", "long", "short",
    "signed", "unsigned", "void"
  };
  for (auto *kw : CastableTypeSpecs)
    Consumer.addKeywordResult(kw);
}

if (CCC.WantCXXNamedCasts && SemaRef.getLangOpts().CPlusPlus) {
  Consumer.addKeywordResult("const_cast");
  Consumer.addKeywordResult("dynamic_cast");
  Consumer.addKeywordResult("reinterpret_cast");
  Consumer.addKeywordResult("static_cast");
}

if (CCC.WantExpressionKeywords) {
  Consumer.addKeywordResult("sizeof");
  if (SemaRef.getLangOpts().Bool || SemaRef.getLangOpts().CPlusPlus) {
    Consumer.addKeywordResult("false");
    Consumer.addKeywordResult("true");
  }

  if (SemaRef.getLangOpts().CPlusPlus) {
    static const char *const CXXExprs[] = {
      "delete", "new", "operator", "throw", "typeid"
    };
    const unsigned NumCXXExprs = llvm::array_lengthof(CXXExprs);
    for (unsigned I = 0; I != NumCXXExprs; ++I)
      Consumer.addKeywordResult(CXXExprs[I]);

    if (isa<CXXMethodDecl>(SemaRef.CurContext) &&
        cast<CXXMethodDecl>(SemaRef.CurContext)->isInstance())
      Consumer.addKeywordResult("this");

    if (SemaRef.getLangOpts().CPlusPlus11) {
      Consumer.addKeywordResult("alignof");
      Consumer.addKeywordResult("nullptr");
    }
  }

  if (SemaRef.getLangOpts().C11) {
    // FIXME: We should not suggest _Alignof if the alignof macro
    // is present.
    Consumer.addKeywordResult("_Alignof");
  }
}

if (CCC.WantRemainingKeywords) {
  if (SemaRef.getCurFunctionOrMethodDecl() || SemaRef.getCurBlock()) {
    // Statements.
    static const char *const CStmts[] = {
      "do", "else", "for", "goto", "if", "return", "switch", "while" };
    const unsigned NumCStmts = llvm::array_lengthof(CStmts);
    for (unsigned I = 0; I != NumCStmts; ++I)
      Consumer.addKeywordResult(CStmts[I]);

    if (SemaRef.getLangOpts().CPlusPlus) {
      Consumer.addKeywordResult("catch");
      Consumer.addKeywordResult("try");
    }

    if (S && S->getBreakParent())
      Consumer.addKeywordResult("break");

    if (S && S->getContinueParent())
      Consumer.addKeywordResult("continue");

    if (SemaRef.getCurFunction() &&
        !SemaRef.getCurFunction()->SwitchStack.empty()) {
      Consumer.addKeywordResult("case");
      Consumer.addKeywordResult("default");
    }
  } else {
    if (SemaRef.getLangOpts().CPlusPlus) {
      Consumer.addKeywordResult("namespace");
      Consumer.addKeywordResult("template");
    }

    if (S && S->isClassScope()) {
      Consumer.addKeywordResult("explicit");
      Consumer.addKeywordResult("friend");
      Consumer.addKeywordResult("mutable");
      Consumer.addKeywordResult("private");
      Consumer.addKeywordResult("protected");
      Consumer.addKeywordResult("public");
      Consumer.addKeywordResult("virtual");
    }
  }

  if (SemaRef.getLangOpts().CPlusPlus) {
    Consumer.addKeywordResult("using");

    if (SemaRef.getLangOpts().CPlusPlus11)
      Consumer.addKeywordResult("static_assert");
  }
}
4838}

4840std::unique_ptr<TypoCorrectionConsumer> Sema::makeTypoCorrectionConsumer(
  const DeclarationNameInfo &TypoName, Sema::LookupNameKind LookupKind,
  Scope *S, CXXScopeSpec *SS, CorrectionCandidateCallback &CCC,
  DeclContext *MemberContext, bool EnteringContext,
  const ObjCObjectPointerType *OPT, bool ErrorRecovery) {

if (Diags.hasFatalErrorOccurred() || !getLangOpts().SpellChecking ||
    DisableTypoCorrection)
  return nullptr;

// In Microsoft mode, don't perform typo correction in a template member
// function dependent context because it interferes with the "lookup into
// dependent bases of class templates" feature.
if (getLangOpts().MSVCCompat && CurContext->isDependentContext() &&
    isa<CXXMethodDecl>(CurContext))
  return nullptr;

// We only attempt to correct typos for identifiers.
IdentifierInfo *Typo = TypoName.getName().getAsIdentifierInfo();
if (!Typo)
  return nullptr;

// If the scope specifier itself was invalid, don't try to correct
// typos.
if (SS && SS->isInvalid())
  return nullptr;

// Never try to correct typos during any kind of code synthesis.
if (!CodeSynthesisContexts.empty())
  return nullptr;

// Don't try to correct 'super'.
if (S && S->isInObjcMethodScope() && Typo == getSuperIdentifier())
  return nullptr;

// Abort if typo correction already failed for this specific typo.
IdentifierSourceLocations::iterator locs = TypoCorrectionFailures.find(Typo);
if (locs != TypoCorrectionFailures.end() &&
    locs->second.count(TypoName.getLoc()))
  return nullptr;

// Don't try to correct the identifier "vector" when in AltiVec mode.
// TODO: Figure out why typo correction misbehaves in this case, fix it, and
// remove this workaround.
if ((getLangOpts().AltiVec || getLangOpts().ZVector) && Typo->isStr("vector"))
  return nullptr;

// Provide a stop gap for files that are just seriously broken.  Trying
// to correct all typos can turn into a HUGE performance penalty, causing
// some files to take minutes to get rejected by the parser.
unsigned Limit = getDiagnostics().getDiagnosticOptions().SpellCheckingLimit;
if (Limit && TyposCorrected >= Limit)
  return nullptr;
++TyposCorrected;

// If we're handling a missing symbol error, using modules, and the
// special search all modules option is used, look for a missing import.
if (ErrorRecovery && getLangOpts().Modules &&
    getLangOpts().ModulesSearchAll) {
  // The following has the side effect of loading the missing module.
  getModuleLoader().lookupMissingImports(Typo->getName(),
                                         TypoName.getBeginLoc());
}

// Extend the lifetime of the callback. We delayed this until here
// to avoid allocations in the hot path (which is where no typo correction
// occurs). Note that CorrectionCandidateCallback is polymorphic and
// initially stack-allocated.
std::unique_ptr<CorrectionCandidateCallback> ClonedCCC = CCC.clone();
auto Consumer = std::make_unique<TypoCorrectionConsumer>(
    *this, TypoName, LookupKind, S, SS, std::move(ClonedCCC), MemberContext,
    EnteringContext);

// Perform name lookup to find visible, similarly-named entities.
bool IsUnqualifiedLookup = false;
DeclContext *QualifiedDC = MemberContext;
if (MemberContext) {
  LookupVisibleDecls(MemberContext, LookupKind, *Consumer);

  // Look in qualified interfaces.
  if (OPT) {
    for (auto *I : OPT->quals())
      LookupVisibleDecls(I, LookupKind, *Consumer);
  }
} else if (SS && SS->isSet()) {
  QualifiedDC = computeDeclContext(*SS, EnteringContext);
  if (!QualifiedDC)
    return nullptr;

  LookupVisibleDecls(QualifiedDC, LookupKind, *Consumer);
} else {
  IsUnqualifiedLookup = true;
}

// Determine whether we are going to search in the various namespaces for
// corrections.
bool SearchNamespaces
  = getLangOpts().CPlusPlus &&
    (IsUnqualifiedLookup || (SS && SS->isSet()));

if (IsUnqualifiedLookup || SearchNamespaces) {
  // For unqualified lookup, look through all of the names that we have
  // seen in this translation unit.
  // FIXME: Re-add the ability to skip very unlikely potential corrections.
  for (const auto &I : Context.Idents)
    Consumer->FoundName(I.getKey());

  // Walk through identifiers in external identifier sources.
  // FIXME: Re-add the ability to skip very unlikely potential corrections.
  if (IdentifierInfoLookup *External
                          = Context.Idents.getExternalIdentifierLookup()) {
    std::unique_ptr<IdentifierIterator> Iter(External->getIdentifiers());
    do {
      StringRef Name = Iter->Next();
      if (Name.empty())
        break;

      Consumer->FoundName(Name);
    } while (true);
  }
}

AddKeywordsToConsumer(*this, *Consumer, S,
                      *Consumer->getCorrectionValidator(),
                      SS && SS->isNotEmpty());

// Build the NestedNameSpecifiers for the KnownNamespaces, if we're going
// to search those namespaces.
if (SearchNamespaces) {
  // Load any externally-known namespaces.
  if (ExternalSource && !LoadedExternalKnownNamespaces) {
    SmallVector<NamespaceDecl *, 4> ExternalKnownNamespaces;
    LoadedExternalKnownNamespaces = true;
    ExternalSource->ReadKnownNamespaces(ExternalKnownNamespaces);
    for (auto *N : ExternalKnownNamespaces)
      KnownNamespaces[N] = true;
  }

  Consumer->addNamespaces(KnownNamespaces);
}

return Consumer;
4982}

4984/// Try to "correct" a typo in the source code by finding
4985/// visible declarations whose names are similar to the name that was
4986/// present in the source code.
4987///
4988/// \param TypoName the \c DeclarationNameInfo structure that contains
4989/// the name that was present in the source code along with its location.
4990///
4991/// \param LookupKind the name-lookup criteria used to search for the name.
4992///
4993/// \param S the scope in which name lookup occurs.
4994///
4995/// \param SS the nested-name-specifier that precedes the name we're
4996/// looking for, if present.
4997///
4998/// \param CCC A CorrectionCandidateCallback object that provides further
4999/// validation of typo correction candidates. It also provides flags for
5000/// determining the set of keywords permitted.
5001///
5002/// \param MemberContext if non-NULL, the context in which to look for
5003/// a member access expression.
5004///
5005/// \param EnteringContext whether we're entering the context described by
5006/// the nested-name-specifier SS.
5007///
5008/// \param OPT when non-NULL, the search for visible declarations will
5009/// also walk the protocols in the qualified interfaces of \p OPT.
5010///
5011/// \returns a \c TypoCorrection containing the corrected name if the typo
5012/// along with information such as the \c NamedDecl where the corrected name
5013/// was declared, and any additional \c NestedNameSpecifier needed to access
5014/// it (C++ only). The \c TypoCorrection is empty if there is no correction.
5015TypoCorrection Sema::CorrectTypo(const DeclarationNameInfo &TypoName,
                               Sema::LookupNameKind LookupKind,
                               Scope *S, CXXScopeSpec *SS,
                               CorrectionCandidateCallback &CCC,
                               CorrectTypoKind Mode,
                               DeclContext *MemberContext,
                               bool EnteringContext,
                               const ObjCObjectPointerType *OPT,
                               bool RecordFailure) {
// Always let the ExternalSource have the first chance at correction, even
// if we would otherwise have given up.
if (ExternalSource) {
  if (TypoCorrection Correction =
          ExternalSource->CorrectTypo(TypoName, LookupKind, S, SS, CCC,
                                      MemberContext, EnteringContext, OPT))
    return Correction;
}

// Ugly hack equivalent to CTC == CTC_ObjCMessageReceiver;
// WantObjCSuper is only true for CTC_ObjCMessageReceiver and for
// some instances of CTC_Unknown, while WantRemainingKeywords is true
// for CTC_Unknown but not for CTC_ObjCMessageReceiver.
bool ObjCMessageReceiver = CCC.WantObjCSuper && !CCC.WantRemainingKeywords;

IdentifierInfo *Typo = TypoName.getName().getAsIdentifierInfo();
auto Consumer = makeTypoCorrectionConsumer(TypoName, LookupKind, S, SS, CCC,
                                           MemberContext, EnteringContext,
                                           OPT, Mode == CTK_ErrorRecovery);

if (!Consumer)
  return TypoCorrection();

// If we haven't found anything, we're done.
if (Consumer->empty())
  return FailedCorrection(Typo, TypoName.getLoc(), RecordFailure);

// Make sure the best edit distance (prior to adding any namespace qualifiers)
// is not more that about a third of the length of the typo's identifier.
unsigned ED = Consumer->getBestEditDistance(true);
unsigned TypoLen = Typo->getName().size();
if (ED > 0 && TypoLen / ED < 3)
  return FailedCorrection(Typo, TypoName.getLoc(), RecordFailure);

TypoCorrection BestTC = Consumer->getNextCorrection();
TypoCorrection SecondBestTC = Consumer->getNextCorrection();
if (!BestTC)
  return FailedCorrection(Typo, TypoName.getLoc(), RecordFailure);

ED = BestTC.getEditDistance();

if (TypoLen >= 3 && ED > 0 && TypoLen / ED < 3) {
  // If this was an unqualified lookup and we believe the callback
  // object wouldn't have filtered out possible corrections, note
  // that no correction was found.
  return FailedCorrection(Typo, TypoName.getLoc(), RecordFailure);
}

// If only a single name remains, return that result.
if (!SecondBestTC ||
    SecondBestTC.getEditDistance(false) > BestTC.getEditDistance(false)) {
  const TypoCorrection &Result = BestTC;

  // Don't correct to a keyword that's the same as the typo; the keyword
  // wasn't actually in scope.
  if (ED == 0 && Result.isKeyword())
    return FailedCorrection(Typo, TypoName.getLoc(), RecordFailure);

  TypoCorrection TC = Result;
  TC.setCorrectionRange(SS, TypoName);
  checkCorrectionVisibility(*this, TC);
  return TC;
} else if (SecondBestTC && ObjCMessageReceiver) {
  // Prefer 'super' when we're completing in a message-receiver
  // context.

  if (BestTC.getCorrection().getAsString() != "super") {
    if (SecondBestTC.getCorrection().getAsString() == "super")
      BestTC = SecondBestTC;
    else if ((*Consumer)["super"].front().isKeyword())
      BestTC = (*Consumer)["super"].front();
  }
  // Don't correct to a keyword that's the same as the typo; the keyword
  // wasn't actually in scope.
  if (BestTC.getEditDistance() == 0 ||
      BestTC.getCorrection().getAsString() != "super")
    return FailedCorrection(Typo, TypoName.getLoc(), RecordFailure);

  BestTC.setCorrectionRange(SS, TypoName);
  return BestTC;
}

// Record the failure's location if needed and return an empty correction. If
// this was an unqualified lookup and we believe the callback object did not
// filter out possible corrections, also cache the failure for the typo.
return FailedCorrection(Typo, TypoName.getLoc(), RecordFailure && !SecondBestTC);
5110}

5112/// Try to "correct" a typo in the source code by finding
5113/// visible declarations whose names are similar to the name that was
5114/// present in the source code.
5115///
5116/// \param TypoName the \c DeclarationNameInfo structure that contains
5117/// the name that was present in the source code along with its location.
5118///
5119/// \param LookupKind the name-lookup criteria used to search for the name.
5120///
5121/// \param S the scope in which name lookup occurs.
5122///
5123/// \param SS the nested-name-specifier that precedes the name we're
5124/// looking for, if present.
5125///
5126/// \param CCC A CorrectionCandidateCallback object that provides further
5127/// validation of typo correction candidates. It also provides flags for
5128/// determining the set of keywords permitted.
5129///
5130/// \param TDG A TypoDiagnosticGenerator functor that will be used to print
5131/// diagnostics when the actual typo correction is attempted.
5132///
5133/// \param TRC A TypoRecoveryCallback functor that will be used to build an
5134/// Expr from a typo correction candidate.
5135///
5136/// \param MemberContext if non-NULL, the context in which to look for
5137/// a member access expression.
5138///
5139/// \param EnteringContext whether we're entering the context described by
5140/// the nested-name-specifier SS.
5141///
5142/// \param OPT when non-NULL, the search for visible declarations will
5143/// also walk the protocols in the qualified interfaces of \p OPT.
5144///
5145/// \returns a new \c TypoExpr that will later be replaced in the AST with an
5146/// Expr representing the result of performing typo correction, or nullptr if
5147/// typo correction is not possible. If nullptr is returned, no diagnostics will
5148/// be emitted and it is the responsibility of the caller to emit any that are
5149/// needed.
5150TypoExpr *Sema::CorrectTypoDelayed(
  const DeclarationNameInfo &TypoName, Sema::LookupNameKind LookupKind,
  Scope *S, CXXScopeSpec *SS, CorrectionCandidateCallback &CCC,
  TypoDiagnosticGenerator TDG, TypoRecoveryCallback TRC, CorrectTypoKind Mode,
  DeclContext *MemberContext, bool EnteringContext,
  const ObjCObjectPointerType *OPT) {
auto Consumer = makeTypoCorrectionConsumer(TypoName, LookupKind, S, SS, CCC,
                                           MemberContext, EnteringContext,
                                           OPT, Mode == CTK_ErrorRecovery);

// Give the external sema source a chance to correct the typo.
TypoCorrection ExternalTypo;
if (ExternalSource && Consumer) {
  ExternalTypo = ExternalSource->CorrectTypo(
      TypoName, LookupKind, S, SS, *Consumer->getCorrectionValidator(),
      MemberContext, EnteringContext, OPT);
  if (ExternalTypo)
    Consumer->addCorrection(ExternalTypo);
}

if (!Consumer || Consumer->empty())
  return nullptr;

// Make sure the best edit distance (prior to adding any namespace qualifiers)
// is not more that about a third of the length of the typo's identifier.
unsigned ED = Consumer->getBestEditDistance(true);
IdentifierInfo *Typo = TypoName.getName().getAsIdentifierInfo();
if (!ExternalTypo && ED > 0 && Typo->getName().size() / ED < 3)
  return nullptr;
ExprEvalContexts.back().NumTypos++;
return createDelayedTypo(std::move(Consumer), std::move(TDG), std::move(TRC),
                         TypoName.getLoc());
5182}

5184void TypoCorrection::addCorrectionDecl(NamedDecl *CDecl) {
if (!CDecl) return;

if (isKeyword())
  CorrectionDecls.clear();

CorrectionDecls.push_back(CDecl);

if (!CorrectionName)
  CorrectionName = CDecl->getDeclName();
5194}

5196std::string TypoCorrection::getAsString(const LangOptions &LO) const {
if (CorrectionNameSpec) {
  std::string tmpBuffer;
  llvm::raw_string_ostream PrefixOStream(tmpBuffer);
  CorrectionNameSpec->print(PrefixOStream, PrintingPolicy(LO));
  PrefixOStream << CorrectionName;
  return PrefixOStream.str();
}

return CorrectionName.getAsString();
5206}

5208bool CorrectionCandidateCallback::ValidateCandidate(
  const TypoCorrection &candidate) {
if (!candidate.isResolved())
  return true;

if (candidate.isKeyword())
  return WantTypeSpecifiers || WantExpressionKeywords || WantCXXNamedCasts ||
         WantRemainingKeywords || WantObjCSuper;

bool HasNonType = false;
bool HasStaticMethod = false;
bool HasNonStaticMethod = false;
for (Decl *D : candidate) {
  if (FunctionTemplateDecl *FTD = dyn_cast<FunctionTemplateDecl>(D))
    D = FTD->getTemplatedDecl();
  if (CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(D)) {
    if (Method->isStatic())
      HasStaticMethod = true;
    else
      HasNonStaticMethod = true;
  }
  if (!isa<TypeDecl>(D))
    HasNonType = true;
}

if (IsAddressOfOperand && HasNonStaticMethod && !HasStaticMethod &&
    !candidate.getCorrectionSpecifier())
  return false;

return WantTypeSpecifiers || HasNonType;
5238}

5240FunctionCallFilterCCC::FunctionCallFilterCCC(Sema &SemaRef, unsigned NumArgs,
                                           bool HasExplicitTemplateArgs,
                                           MemberExpr *ME)
  : NumArgs(NumArgs), HasExplicitTemplateArgs(HasExplicitTemplateArgs),
    CurContext(SemaRef.CurContext), MemberFn(ME) {
WantTypeSpecifiers = false;
WantFunctionLikeCasts = SemaRef.getLangOpts().CPlusPlus &&
                        !HasExplicitTemplateArgs && NumArgs == 1;
WantCXXNamedCasts = HasExplicitTemplateArgs && NumArgs == 1;
WantRemainingKeywords = false;
5250}

5252bool FunctionCallFilterCCC::ValidateCandidate(const TypoCorrection &candidate) {
if (!candidate.getCorrectionDecl())
  return candidate.isKeyword();

for (auto *C : candidate) {
  FunctionDecl *FD = nullptr;
  NamedDecl *ND = C->getUnderlyingDecl();
  if (FunctionTemplateDecl *FTD = dyn_cast<FunctionTemplateDecl>(ND))
    FD = FTD->getTemplatedDecl();
  if (!HasExplicitTemplateArgs && !FD) {
    if (!(FD = dyn_cast<FunctionDecl>(ND)) && isa<ValueDecl>(ND)) {
      // If the Decl is neither a function nor a template function,
      // determine if it is a pointer or reference to a function. If so,
      // check against the number of arguments expected for the pointee.
      QualType ValType = cast<ValueDecl>(ND)->getType();
      if (ValType.isNull())
        continue;
      if (ValType->isAnyPointerType() || ValType->isReferenceType())
        ValType = ValType->getPointeeType();
      if (const FunctionProtoType *FPT = ValType->getAs<FunctionProtoType>())
        if (FPT->getNumParams() == NumArgs)
          return true;
    }
  }

  // A typo for a function-style cast can look like a function call in C++.
  if ((HasExplicitTemplateArgs ? getAsTypeTemplateDecl(ND) != nullptr
                               : isa<TypeDecl>(ND)) &&
      CurContext->getParentASTContext().getLangOpts().CPlusPlus)
    // Only a class or class template can take two or more arguments.
    return NumArgs <= 1 || HasExplicitTemplateArgs || isa<CXXRecordDecl>(ND);

  // Skip the current candidate if it is not a FunctionDecl or does not accept
  // the current number of arguments.
  if (!FD || !(FD->getNumParams() >= NumArgs &&
               FD->getMinRequiredArguments() <= NumArgs))
    continue;

  // If the current candidate is a non-static C++ method, skip the candidate
  // unless the method being corrected--or the current DeclContext, if the
  // function being corrected is not a method--is a method in the same class
  // or a descendent class of the candidate's parent class.
  if (CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(FD)) {
    if (MemberFn || !MD->isStatic()) {
      CXXMethodDecl *CurMD =
          MemberFn
              ? dyn_cast_or_null<CXXMethodDecl>(MemberFn->getMemberDecl())
              : dyn_cast_or_null<CXXMethodDecl>(CurContext);
      CXXRecordDecl *CurRD =
          CurMD ? CurMD->getParent()->getCanonicalDecl() : nullptr;
      CXXRecordDecl *RD = MD->getParent()->getCanonicalDecl();
      if (!CurRD || (CurRD != RD && !CurRD->isDerivedFrom(RD)))
        continue;
    }
  }
  return true;
}
return false;
5310}

5312void Sema::diagnoseTypo(const TypoCorrection &Correction,
                      const PartialDiagnostic &TypoDiag,
                      bool ErrorRecovery) {
diagnoseTypo(Correction, TypoDiag, PDiag(diag::note_previous_decl),
             ErrorRecovery);
5317}

5319/// Find which declaration we should import to provide the definition of
5320/// the given declaration.
5321static NamedDecl *getDefinitionToImport(NamedDecl *D) {
if (VarDecl *VD = dyn_cast<VarDecl>(D))
  return VD->getDefinition();
if (FunctionDecl *FD = dyn_cast<FunctionDecl>(D))
  return FD->getDefinition();
if (TagDecl *TD = dyn_cast<TagDecl>(D))
  return TD->getDefinition();
// The first definition for this ObjCInterfaceDecl might be in the TU
// and not associated with any module. Use the one we know to be complete
// and have just seen in a module.
if (ObjCInterfaceDecl *ID = dyn_cast<ObjCInterfaceDecl>(D))
  return ID;
if (ObjCProtocolDecl *PD = dyn_cast<ObjCProtocolDecl>(D))
  return PD->getDefinition();
if (TemplateDecl *TD = dyn_cast<TemplateDecl>(D))
  if (NamedDecl *TTD = TD->getTemplatedDecl())
    return getDefinitionToImport(TTD);
return nullptr;
5339}

5341void Sema::diagnoseMissingImport(SourceLocation Loc, NamedDecl *Decl,
                               MissingImportKind MIK, bool Recover) {
// Suggest importing a module providing the definition of this entity, if
// possible.
NamedDecl *Def = getDefinitionToImport(Decl);
if (!Def)
  Def = Decl;

Module *Owner = getOwningModule(Def);
assert(Owner && "definition of hidden declaration is not in a module")((void)0);

llvm::SmallVector<Module*, 8> OwningModules;
OwningModules.push_back(Owner);
auto Merged = Context.getModulesWithMergedDefinition(Def);
OwningModules.insert(OwningModules.end(), Merged.begin(), Merged.end());

diagnoseMissingImport(Loc, Def, Def->getLocation(), OwningModules, MIK,
                      Recover);
5359}

5361/// Get a "quoted.h" or <angled.h> include path to use in a diagnostic
5362/// suggesting the addition of a #include of the specified file.
5363static std::string getHeaderNameForHeader(Preprocessor &PP, const FileEntry *E,
                                        llvm::StringRef IncludingFile) {
bool IsSystem = false;
auto Path = PP.getHeaderSearchInfo().suggestPathToFileForDiagnostics(
    E, IncludingFile, &IsSystem);
return (IsSystem ? '<' : '"') + Path + (IsSystem ? '>' : '"');
5369}

5371void Sema::diagnoseMissingImport(SourceLocation UseLoc, NamedDecl *Decl,
                               SourceLocation DeclLoc,
                               ArrayRef<Module *> Modules,
                               MissingImportKind MIK, bool Recover) {
assert(!Modules.empty())((void)0);

auto NotePrevious = [&] {
  // FIXME: Suppress the note backtrace even under
  // -fdiagnostics-show-note-include-stack. We don't care how this
  // declaration was previously reached.
  Diag(DeclLoc, diag::note_unreachable_entity) << (int)MIK;
};

// Weed out duplicates from module list.
llvm::SmallVector<Module*, 8> UniqueModules;
llvm::SmallDenseSet<Module*, 8> UniqueModuleSet;
for (auto *M : Modules) {
  if (M->Kind == Module::GlobalModuleFragment)
    continue;
  if (UniqueModuleSet.insert(M).second)
    UniqueModules.push_back(M);
}

// Try to find a suitable header-name to #include.
std::string HeaderName;
if (const FileEntry *Header =
        PP.getHeaderToIncludeForDiagnostics(UseLoc, DeclLoc)) {
  if (const FileEntry *FE =
          SourceMgr.getFileEntryForID(SourceMgr.getFileID(UseLoc)))
    HeaderName = getHeaderNameForHeader(PP, Header, FE->tryGetRealPathName());
}

// If we have a #include we should suggest, or if all definition locations
// were in global module fragments, don't suggest an import.
if (!HeaderName.empty() || UniqueModules.empty()) {
  // FIXME: Find a smart place to suggest inserting a #include, and add
  // a FixItHint there.
  Diag(UseLoc, diag::err_module_unimported_use_header)
      << (int)MIK << Decl << !HeaderName.empty() << HeaderName;
  // Produce a note showing where the entity was declared.
  NotePrevious();
  if (Recover)
    createImplicitModuleImportForErrorRecovery(UseLoc, Modules[0]);
  return;
}

Modules = UniqueModules;

if (Modules.size() > 1) {
  std::string ModuleList;
  unsigned N = 0;
  for (Module *M : Modules) {
    ModuleList += "\n        ";
    if (++N == 5 && N != Modules.size()) {
      ModuleList += "[...]";
      break;
    }
    ModuleList += M->getFullModuleName();
  }

  Diag(UseLoc, diag::err_module_unimported_use_multiple)
    << (int)MIK << Decl << ModuleList;
} else {
  // FIXME: Add a FixItHint that imports the corresponding module.
  Diag(UseLoc, diag::err_module_unimported_use)
    << (int)MIK << Decl << Modules[0]->getFullModuleName();
}

NotePrevious();

// Try to recover by implicitly importing this module.
if (Recover)
  createImplicitModuleImportForErrorRecovery(UseLoc, Modules[0]);
5444}

5446/// Diagnose a successfully-corrected typo. Separated from the correction
5447/// itself to allow external validation of the result, etc.
5448///
5449/// \param Correction The result of performing typo correction.
5450/// \param TypoDiag The diagnostic to produce. This will have the corrected
5451///        string added to it (and usually also a fixit).
5452/// \param PrevNote A note to use when indicating the location of the entity to
5453///        which we are correcting. Will have the correction string added to it.
5454/// \param ErrorRecovery If \c true (the default), the caller is going to
5455///        recover from the typo as if the corrected string had been typed.
5456///        In this case, \c PDiag must be an error, and we will attach a fixit
5457///        to it.
5458void Sema::diagnoseTypo(const TypoCorrection &Correction,
                      const PartialDiagnostic &TypoDiag,
                      const PartialDiagnostic &PrevNote,
                      bool ErrorRecovery) {
std::string CorrectedStr = Correction.getAsString(getLangOpts());
std::string CorrectedQuotedStr = Correction.getQuoted(getLangOpts());
FixItHint FixTypo = FixItHint::CreateReplacement(
    Correction.getCorrectionRange(), CorrectedStr);

// Maybe we're just missing a module import.
if (Correction.requiresImport()) {
  NamedDecl *Decl = Correction.getFoundDecl();
  assert(Decl && "import required but no declaration to import")((void)0);

  diagnoseMissingImport(Correction.getCorrectionRange().getBegin(), Decl,
                        MissingImportKind::Declaration, ErrorRecovery);
  return;
}

Diag(Correction.getCorrectionRange().getBegin(), TypoDiag)
  << CorrectedQuotedStr << (ErrorRecovery ? FixTypo : FixItHint());

NamedDecl *ChosenDecl =
    Correction.isKeyword() ? nullptr : Correction.getFoundDecl();
if (PrevNote.getDiagID() && ChosenDecl)
  Diag(ChosenDecl->getLocation(), PrevNote)
    << CorrectedQuotedStr << (ErrorRecovery ? FixItHint() : FixTypo);

// Add any extra diagnostics.
for (const PartialDiagnostic &PD : Correction.getExtraDiagnostics())
  Diag(Correction.getCorrectionRange().getBegin(), PD);
5489}

5491TypoExpr *Sema::createDelayedTypo(std::unique_ptr<TypoCorrectionConsumer> TCC,
                                TypoDiagnosticGenerator TDG,
                                TypoRecoveryCallback TRC,
                                SourceLocation TypoLoc) {
assert(TCC && "createDelayedTypo requires a valid TypoCorrectionConsumer")((void)0);
auto TE = new (Context) TypoExpr(Context.DependentTy, TypoLoc);
auto &State = DelayedTypos[TE];
State.Consumer = std::move(TCC);
State.DiagHandler = std::move(TDG);
State.RecoveryHandler = std::move(TRC);
if (TE)
  TypoExprs.push_back(TE);
return TE;
5504}

5506const Sema::TypoExprState &Sema::getTypoExprState(TypoExpr *TE) const {
auto Entry = DelayedTypos.find(TE);
assert(Entry != DelayedTypos.end() &&((void)0)
       "Failed to get the state for a TypoExpr!")((void)0);
return Entry->second;
5511}

5513void Sema::clearDelayedTypo(TypoExpr *TE) {
DelayedTypos.erase(TE);
5515}

5517void Sema::ActOnPragmaDump(Scope *S, SourceLocation IILoc, IdentifierInfo *II) {
DeclarationNameInfo Name(II, IILoc);
LookupResult R(*this, Name, LookupAnyName, Sema::NotForRedeclaration);
R.suppressDiagnostics();
R.setHideTags(false);
LookupName(R, S);
R.dump();
5524}