text: //===--- SemaInit.cpp - Semantic Analysis for Initializers ----------------===//
  //
  // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
  // See https://llvm.org/LICENSE.txt for license information.
  // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
  //
  //===----------------------------------------------------------------------===//
  //
  // This file implements semantic analysis for initializers.
  //
  //===----------------------------------------------------------------------===//
  
  #include "clang/AST/ASTContext.h"
  #include "clang/AST/DeclObjC.h"
  #include "clang/AST/ExprCXX.h"
  #include "clang/AST/ExprObjC.h"
  #include "clang/AST/ExprOpenMP.h"
  #include "clang/AST/TypeLoc.h"
  #include "clang/Basic/CharInfo.h"
  #include "clang/Basic/SourceManager.h"
  #include "clang/Basic/TargetInfo.h"
  #include "clang/Sema/Designator.h"
  #include "clang/Sema/Initialization.h"
  #include "clang/Sema/Lookup.h"
  #include "clang/Sema/SemaInternal.h"
  #include "llvm/ADT/APInt.h"
  #include "llvm/ADT/SmallString.h"
  #include "llvm/Support/ErrorHandling.h"
  #include "llvm/Support/raw_ostream.h"
  
  using namespace clang;
  
  //===----------------------------------------------------------------------===//
  // Sema Initialization Checking
  //===----------------------------------------------------------------------===//
  
  /// Check whether T is compatible with a wide character type (wchar_t,
  /// char16_t or char32_t).
  static bool IsWideCharCompatible(QualType T, ASTContext &Context) {
    if (Context.typesAreCompatible(Context.getWideCharType(), T))
      return true;
    if (Context.getLangOpts().CPlusPlus || Context.getLangOpts().C11) {
      return Context.typesAreCompatible(Context.Char16Ty, T) ||
             Context.typesAreCompatible(Context.Char32Ty, T);
    }
    return false;
  }
  
  enum StringInitFailureKind {
    SIF_None,
    SIF_NarrowStringIntoWideChar,
    SIF_WideStringIntoChar,
    SIF_IncompatWideStringIntoWideChar,
    SIF_UTF8StringIntoPlainChar,
    SIF_PlainStringIntoUTF8Char,
    SIF_Other
  };
  
  /// Check whether the array of type AT can be initialized by the Init
  /// expression by means of string initialization. Returns SIF_None if so,
  /// otherwise returns a StringInitFailureKind that describes why the
  /// initialization would not work.
  static StringInitFailureKind IsStringInit(Expr *Init, const ArrayType *AT,
                                            ASTContext &Context) {
    if (!isa<ConstantArrayType>(AT) && !isa<IncompleteArrayType>(AT))
      return SIF_Other;
  
    // See if this is a string literal or @encode.
    Init = Init->IgnoreParens();
  
    // Handle @encode, which is a narrow string.
    if (isa<ObjCEncodeExpr>(Init) && AT->getElementType()->isCharType())
      return SIF_None;
  
    // Otherwise we can only handle string literals.
    StringLiteral *SL = dyn_cast<StringLiteral>(Init);
    if (!SL)
      return SIF_Other;
  
    const QualType ElemTy =
        Context.getCanonicalType(AT->getElementType()).getUnqualifiedType();
  
    switch (SL->getKind()) {
    case StringLiteral::UTF8:
      // char8_t array can be initialized with a UTF-8 string.
      if (ElemTy->isChar8Type())
        return SIF_None;
      LLVM_FALLTHROUGH;
    case StringLiteral::Ascii:
      // char array can be initialized with a narrow string.
      // Only allow char x[] = "foo";  not char x[] = L"foo";
      if (ElemTy->isCharType())
        return (SL->getKind() == StringLiteral::UTF8 &&
                Context.getLangOpts().Char8)
                   ? SIF_UTF8StringIntoPlainChar
                   : SIF_None;
      if (ElemTy->isChar8Type())
        return SIF_PlainStringIntoUTF8Char;
      if (IsWideCharCompatible(ElemTy, Context))
        return SIF_NarrowStringIntoWideChar;
      return SIF_Other;
    // C99 6.7.8p15 (with correction from DR343), or C11 6.7.9p15:
    // "An array with element type compatible with a qualified or unqualified
    // version of wchar_t, char16_t, or char32_t may be initialized by a wide
    // string literal with the corresponding encoding prefix (L, u, or U,
    // respectively), optionally enclosed in braces.
    case StringLiteral::UTF16:
      if (Context.typesAreCompatible(Context.Char16Ty, ElemTy))
        return SIF_None;
      if (ElemTy->isCharType() || ElemTy->isChar8Type())
        return SIF_WideStringIntoChar;
      if (IsWideCharCompatible(ElemTy, Context))
        return SIF_IncompatWideStringIntoWideChar;
      return SIF_Other;
    case StringLiteral::UTF32:
      if (Context.typesAreCompatible(Context.Char32Ty, ElemTy))
        return SIF_None;
      if (ElemTy->isCharType() || ElemTy->isChar8Type())
        return SIF_WideStringIntoChar;
      if (IsWideCharCompatible(ElemTy, Context))
        return SIF_IncompatWideStringIntoWideChar;
      return SIF_Other;
    case StringLiteral::Wide:
      if (Context.typesAreCompatible(Context.getWideCharType(), ElemTy))
        return SIF_None;
      if (ElemTy->isCharType() || ElemTy->isChar8Type())
        return SIF_WideStringIntoChar;
      if (IsWideCharCompatible(ElemTy, Context))
        return SIF_IncompatWideStringIntoWideChar;
      return SIF_Other;
    }
  
    llvm_unreachable("missed a StringLiteral kind?");
  }
  
  static StringInitFailureKind IsStringInit(Expr *init, QualType declType,
                                            ASTContext &Context) {
    const ArrayType *arrayType = Context.getAsArrayType(declType);
    if (!arrayType)
      return SIF_Other;
    return IsStringInit(init, arrayType, Context);
  }
  
  /// Update the type of a string literal, including any surrounding parentheses,
  /// to match the type of the object which it is initializing.
  static void updateStringLiteralType(Expr *E, QualType Ty) {
    while (true) {
      E->setType(Ty);
      E->setValueKind(VK_RValue);
      if (isa<StringLiteral>(E) || isa<ObjCEncodeExpr>(E)) {
        break;
      } else if (ParenExpr *PE = dyn_cast<ParenExpr>(E)) {
        E = PE->getSubExpr();
      } else if (UnaryOperator *UO = dyn_cast<UnaryOperator>(E)) {
        assert(UO->getOpcode() == UO_Extension);
        E = UO->getSubExpr();
      } else if (GenericSelectionExpr *GSE = dyn_cast<GenericSelectionExpr>(E)) {
        E = GSE->getResultExpr();
      } else if (ChooseExpr *CE = dyn_cast<ChooseExpr>(E)) {
        E = CE->getChosenSubExpr();
      } else {
        llvm_unreachable("unexpected expr in string literal init");
      }
    }
  }
  
  /// Fix a compound literal initializing an array so it's correctly marked
  /// as an rvalue.
  static void updateGNUCompoundLiteralRValue(Expr *E) {
    while (true) {
      E->setValueKind(VK_RValue);
      if (isa<CompoundLiteralExpr>(E)) {
        break;
      } else if (ParenExpr *PE = dyn_cast<ParenExpr>(E)) {
        E = PE->getSubExpr();
      } else if (UnaryOperator *UO = dyn_cast<UnaryOperator>(E)) {
        assert(UO->getOpcode() == UO_Extension);
        E = UO->getSubExpr();
      } else if (GenericSelectionExpr *GSE = dyn_cast<GenericSelectionExpr>(E)) {
        E = GSE->getResultExpr();
      } else if (ChooseExpr *CE = dyn_cast<ChooseExpr>(E)) {
        E = CE->getChosenSubExpr();
      } else {
        llvm_unreachable("unexpected expr in array compound literal init");
      }
    }
  }
  
  static void CheckStringInit(Expr *Str, QualType &DeclT, const ArrayType *AT,
                              Sema &S) {
    // Get the length of the string as parsed.
    auto *ConstantArrayTy =
        cast<ConstantArrayType>(Str->getType()->getAsArrayTypeUnsafe());
    uint64_t StrLength = ConstantArrayTy->getSize().getZExtValue();
  
    if (const IncompleteArrayType *IAT = dyn_cast<IncompleteArrayType>(AT)) {
      // C99 6.7.8p14. We have an array of character type with unknown size
      // being initialized to a string literal.
      llvm::APInt ConstVal(32, StrLength);
      // Return a new array type (C99 6.7.8p22).
      DeclT = S.Context.getConstantArrayType(IAT->getElementType(),
                                             ConstVal, nullptr,
                                             ArrayType::Normal, 0);
      updateStringLiteralType(Str, DeclT);
      return;
    }
  
    const ConstantArrayType *CAT = cast<ConstantArrayType>(AT);
  
    // We have an array of character type with known size.  However,
    // the size may be smaller or larger than the string we are initializing.
    // FIXME: Avoid truncation for 64-bit length strings.
    if (S.getLangOpts().CPlusPlus) {
      if (StringLiteral *SL = dyn_cast<StringLiteral>(Str->IgnoreParens())) {
        // For Pascal strings it's OK to strip off the terminating null character,
        // so the example below is valid:
        //
        // unsigned char a[2] = "\pa";
        if (SL->isPascal())
          StrLength--;
      }
  
      // [dcl.init.string]p2
      if (StrLength > CAT->getSize().getZExtValue())
        S.Diag(Str->getBeginLoc(),
               diag::err_initializer_string_for_char_array_too_long)
            << Str->getSourceRange();
    } else {
      // C99 6.7.8p14.
      if (StrLength-1 > CAT->getSize().getZExtValue())
        S.Diag(Str->getBeginLoc(),
               diag::ext_initializer_string_for_char_array_too_long)
            << Str->getSourceRange();
    }
  
    // Set the type to the actual size that we are initializing.  If we have
    // something like:
    //   char x[1] = "foo";
    // then this will set the string literal's type to char[1].
    updateStringLiteralType(Str, DeclT);
  }
  
  //===----------------------------------------------------------------------===//
  // Semantic checking for initializer lists.
  //===----------------------------------------------------------------------===//
  
  namespace {
  
  /// Semantic checking for initializer lists.
  ///
  /// The InitListChecker class contains a set of routines that each
  /// handle the initialization of a certain kind of entity, e.g.,
  /// arrays, vectors, struct/union types, scalars, etc. The
  /// InitListChecker itself performs a recursive walk of the subobject
  /// structure of the type to be initialized, while stepping through
  /// the initializer list one element at a time. The IList and Index
  /// parameters to each of the Check* routines contain the active
  /// (syntactic) initializer list and the index into that initializer
  /// list that represents the current initializer. Each routine is
  /// responsible for moving that Index forward as it consumes elements.
  ///
  /// Each Check* routine also has a StructuredList/StructuredIndex
  /// arguments, which contains the current "structured" (semantic)
  /// initializer list and the index into that initializer list where we
  /// are copying initializers as we map them over to the semantic
  /// list. Once we have completed our recursive walk of the subobject
  /// structure, we will have constructed a full semantic initializer
  /// list.
  ///
  /// C99 designators cause changes in the initializer list traversal,
  /// because they make the initialization "jump" into a specific
  /// subobject and then continue the initialization from that
  /// point. CheckDesignatedInitializer() recursively steps into the
  /// designated subobject and manages backing out the recursion to
  /// initialize the subobjects after the one designated.
  ///
  /// If an initializer list contains any designators, we build a placeholder
  /// structured list even in 'verify only' mode, so that we can track which
  /// elements need 'empty' initializtion.
  class InitListChecker {
    Sema &SemaRef;
    bool hadError = false;
    bool VerifyOnly; // No diagnostics.
    bool TreatUnavailableAsInvalid; // Used only in VerifyOnly mode.
    bool InOverloadResolution;
    InitListExpr *FullyStructuredList = nullptr;
    NoInitExpr *DummyExpr = nullptr;
  
    NoInitExpr *getDummyInit() {
      if (!DummyExpr)
        DummyExpr = new (SemaRef.Context) NoInitExpr(SemaRef.Context.VoidTy);
      return DummyExpr;
    }
  
    void CheckImplicitInitList(const InitializedEntity &Entity,
                               InitListExpr *ParentIList, QualType T,
                               unsigned &Index, InitListExpr *StructuredList,
                               unsigned &StructuredIndex);
    void CheckExplicitInitList(const InitializedEntity &Entity,
                               InitListExpr *IList, QualType &T,
                               InitListExpr *StructuredList,
                               bool TopLevelObject = false);
    void CheckListElementTypes(const InitializedEntity &Entity,
                               InitListExpr *IList, QualType &DeclType,
                               bool SubobjectIsDesignatorContext,
                               unsigned &Index,
                               InitListExpr *StructuredList,
                               unsigned &StructuredIndex,
                               bool TopLevelObject = false);
    void CheckSubElementType(const InitializedEntity &Entity,
                             InitListExpr *IList, QualType ElemType,
                             unsigned &Index,
                             InitListExpr *StructuredList,
                             unsigned &StructuredIndex);
    void CheckComplexType(const InitializedEntity &Entity,
                          InitListExpr *IList, QualType DeclType,
                          unsigned &Index,
                          InitListExpr *StructuredList,
                          unsigned &StructuredIndex);
    void CheckScalarType(const InitializedEntity &Entity,
                         InitListExpr *IList, QualType DeclType,
                         unsigned &Index,
                         InitListExpr *StructuredList,
                         unsigned &StructuredIndex);
    void CheckReferenceType(const InitializedEntity &Entity,
                            InitListExpr *IList, QualType DeclType,
                            unsigned &Index,
                            InitListExpr *StructuredList,
                            unsigned &StructuredIndex);
    void CheckVectorType(const InitializedEntity &Entity,
                         InitListExpr *IList, QualType DeclType, unsigned &Index,
                         InitListExpr *StructuredList,
                         unsigned &StructuredIndex);
    void CheckStructUnionTypes(const InitializedEntity &Entity,
                               InitListExpr *IList, QualType DeclType,
                               CXXRecordDecl::base_class_range Bases,
                               RecordDecl::field_iterator Field,
                               bool SubobjectIsDesignatorContext, unsigned &Index,
                               InitListExpr *StructuredList,
                               unsigned &StructuredIndex,
                               bool TopLevelObject = false);
    void CheckArrayType(const InitializedEntity &Entity,
                        InitListExpr *IList, QualType &DeclType,
                        llvm::APSInt elementIndex,
                        bool SubobjectIsDesignatorContext, unsigned &Index,
                        InitListExpr *StructuredList,
                        unsigned &StructuredIndex);
    bool CheckDesignatedInitializer(const InitializedEntity &Entity,
                                    InitListExpr *IList, DesignatedInitExpr *DIE,
                                    unsigned DesigIdx,
                                    QualType &CurrentObjectType,
                                    RecordDecl::field_iterator *NextField,
                                    llvm::APSInt *NextElementIndex,
                                    unsigned &Index,
                                    InitListExpr *StructuredList,
                                    unsigned &StructuredIndex,
                                    bool FinishSubobjectInit,
                                    bool TopLevelObject);
    InitListExpr *getStructuredSubobjectInit(InitListExpr *IList, unsigned Index,
                                             QualType CurrentObjectType,
                                             InitListExpr *StructuredList,
                                             unsigned StructuredIndex,
                                             SourceRange InitRange,
                                             bool IsFullyOverwritten = false);
    void UpdateStructuredListElement(InitListExpr *StructuredList,
                                     unsigned &StructuredIndex,
                                     Expr *expr);
    InitListExpr *createInitListExpr(QualType CurrentObjectType,
                                     SourceRange InitRange,
                                     unsigned ExpectedNumInits);
    int numArrayElements(QualType DeclType);
    int numStructUnionElements(QualType DeclType);
  
    ExprResult PerformEmptyInit(SourceLocation Loc,
                                const InitializedEntity &Entity);
  
    /// Diagnose that OldInit (or part thereof) has been overridden by NewInit.
    void diagnoseInitOverride(Expr *OldInit, SourceRange NewInitRange,
                              bool FullyOverwritten = true) {
      // Overriding an initializer via a designator is valid with C99 designated
      // initializers, but ill-formed with C++20 designated initializers.
      unsigned DiagID = SemaRef.getLangOpts().CPlusPlus
                            ? diag::ext_initializer_overrides
                            : diag::warn_initializer_overrides;
  
      if (InOverloadResolution && SemaRef.getLangOpts().CPlusPlus) {
        // In overload resolution, we have to strictly enforce the rules, and so
        // don't allow any overriding of prior initializers. This matters for a
        // case such as:
        //
        //   union U { int a, b; };
        //   struct S { int a, b; };
        //   void f(U), f(S);
        //
        // Here, f({.a = 1, .b = 2}) is required to call the struct overload. For
        // consistency, we disallow all overriding of prior initializers in
        // overload resolution, not only overriding of union members.
        hadError = true;
      } else if (OldInit->getType().isDestructedType() && !FullyOverwritten) {
        // If we'll be keeping around the old initializer but overwriting part of
        // the object it initialized, and that object is not trivially
        // destructible, this can leak. Don't allow that, not even as an
        // extension.
        //
        // FIXME: It might be reasonable to allow this in cases where the part of
        // the initializer that we're overriding has trivial destruction.
        DiagID = diag::err_initializer_overrides_destructed;
      } else if (!OldInit->getSourceRange().isValid()) {
        // We need to check on source range validity because the previous
        // initializer does not have to be an explicit initializer. e.g.,
        //
        // struct P { int a, b; };
        // struct PP { struct P p } l = { { .a = 2 }, .p.b = 3 };
        //
        // There is an overwrite taking place because the first braced initializer
        // list "{ .a = 2 }" already provides value for .p.b (which is zero).
        //
        // Such overwrites are harmless, so we don't diagnose them. (Note that in
        // C++, this cannot be reached unless we've already seen and diagnosed a
        // different conformance issue, such as a mixture of designated and
        // non-designated initializers or a multi-level designator.)
        return;
      }
  
      if (!VerifyOnly) {
        SemaRef.Diag(NewInitRange.getBegin(), DiagID)
            << NewInitRange << FullyOverwritten << OldInit->getType();
        SemaRef.Diag(OldInit->getBeginLoc(), diag::note_previous_initializer)
            << (OldInit->HasSideEffects(SemaRef.Context) && FullyOverwritten)
            << OldInit->getSourceRange();
      }
    }
  
    // Explanation on the "FillWithNoInit" mode:
    //
    // Assume we have the following definitions (Case#1):
    // struct P { char x[6][6]; } xp = { .x[1] = "bar" };
    // struct PP { struct P lp; } l = { .lp = xp, .lp.x[1][2] = 'f' };
    //
    // l.lp.x[1][0..1] should not be filled with implicit initializers because the
    // "base" initializer "xp" will provide values for them; l.lp.x[1] will be "baf".
    //
    // But if we have (Case#2):
    // struct PP l = { .lp = xp, .lp.x[1] = { [2] = 'f' } };
    //
    // l.lp.x[1][0..1] are implicitly initialized and do not use values from the
    // "base" initializer; l.lp.x[1] will be "\0\0f\0\0\0".
    //
    // To distinguish Case#1 from Case#2, and also to avoid leaving many "holes"
    // in the InitListExpr, the "holes" in Case#1 are filled not with empty
    // initializers but with special "NoInitExpr" place holders, which tells the
    // CodeGen not to generate any initializers for these parts.
    void FillInEmptyInitForBase(unsigned Init, const CXXBaseSpecifier &Base,
                                const InitializedEntity &ParentEntity,
                                InitListExpr *ILE, bool &RequiresSecondPass,
                                bool FillWithNoInit);
    void FillInEmptyInitForField(unsigned Init, FieldDecl *Field,
                                 const InitializedEntity &ParentEntity,
                                 InitListExpr *ILE, bool &RequiresSecondPass,
                                 bool FillWithNoInit = false);
    void FillInEmptyInitializations(const InitializedEntity &Entity,
                                    InitListExpr *ILE, bool &RequiresSecondPass,
                                    InitListExpr *OuterILE, unsigned OuterIndex,
                                    bool FillWithNoInit = false);
    bool CheckFlexibleArrayInit(const InitializedEntity &Entity,
                                Expr *InitExpr, FieldDecl *Field,
                                bool TopLevelObject);
    void CheckEmptyInitializable(const InitializedEntity &Entity,
                                 SourceLocation Loc);
  
  public:
    InitListChecker(Sema &S, const InitializedEntity &Entity, InitListExpr *IL,
                    QualType &T, bool VerifyOnly, bool TreatUnavailableAsInvalid,
                    bool InOverloadResolution = false);
    bool HadError() { return hadError; }
  
    // Retrieves the fully-structured initializer list used for
    // semantic analysis and code generation.
    InitListExpr *getFullyStructuredList() const { return FullyStructuredList; }
  };
  
  } // end anonymous namespace
  
  ExprResult InitListChecker::PerformEmptyInit(SourceLocation Loc,
                                               const InitializedEntity &Entity) {
    InitializationKind Kind = InitializationKind::CreateValue(Loc, Loc, Loc,
                                                              true);
    MultiExprArg SubInit;
    Expr *InitExpr;
    InitListExpr DummyInitList(SemaRef.Context, Loc, None, Loc);
  
    // C++ [dcl.init.aggr]p7:
    //   If there are fewer initializer-clauses in the list than there are
    //   members in the aggregate, then each member not explicitly initialized
    //   ...
    bool EmptyInitList = SemaRef.getLangOpts().CPlusPlus11 &&
        Entity.getType()->getBaseElementTypeUnsafe()->isRecordType();
    if (EmptyInitList) {
      // C++1y / DR1070:
      //   shall be initialized [...] from an empty initializer list.
      //
      // We apply the resolution of this DR to C++11 but not C++98, since C++98
      // does not have useful semantics for initialization from an init list.
      // We treat this as copy-initialization, because aggregate initialization
      // always performs copy-initialization on its elements.
      //
      // Only do this if we're initializing a class type, to avoid filling in
      // the initializer list where possible.
      InitExpr = VerifyOnly ? &DummyInitList : new (SemaRef.Context)
                     InitListExpr(SemaRef.Context, Loc, None, Loc);
      InitExpr->setType(SemaRef.Context.VoidTy);
      SubInit = InitExpr;
      Kind = InitializationKind::CreateCopy(Loc, Loc);
    } else {
      // C++03:
      //   shall be value-initialized.
    }
  
    InitializationSequence InitSeq(SemaRef, Entity, Kind, SubInit);
    // libstdc++4.6 marks the vector default constructor as explicit in
    // _GLIBCXX_DEBUG mode, so recover using the C++03 logic in that case.
    // stlport does so too. Look for std::__debug for libstdc++, and for
    // std:: for stlport.  This is effectively a compiler-side implementation of
    // LWG2193.
    if (!InitSeq && EmptyInitList && InitSeq.getFailureKind() ==
            InitializationSequence::FK_ExplicitConstructor) {
      OverloadCandidateSet::iterator Best;
      OverloadingResult O =
          InitSeq.getFailedCandidateSet()
              .BestViableFunction(SemaRef, Kind.getLocation(), Best);
      (void)O;
      assert(O == OR_Success && "Inconsistent overload resolution");
      CXXConstructorDecl *CtorDecl = cast<CXXConstructorDecl>(Best->Function);
      CXXRecordDecl *R = CtorDecl->getParent();
  
      if (CtorDecl->getMinRequiredArguments() == 0 &&
          CtorDecl->isExplicit() && R->getDeclName() &&
          SemaRef.SourceMgr.isInSystemHeader(CtorDecl->getLocation())) {
        bool IsInStd = false;
        for (NamespaceDecl *ND = dyn_cast<NamespaceDecl>(R->getDeclContext());
             ND && !IsInStd; ND = dyn_cast<NamespaceDecl>(ND->getParent())) {
          if (SemaRef.getStdNamespace()->InEnclosingNamespaceSetOf(ND))
            IsInStd = true;
        }
  
        if (IsInStd && llvm::StringSwitch<bool>(R->getName())
                .Cases("basic_string", "deque", "forward_list", true)
                .Cases("list", "map", "multimap", "multiset", true)
                .Cases("priority_queue", "queue", "set", "stack", true)
                .Cases("unordered_map", "unordered_set", "vector", true)
                .Default(false)) {
          InitSeq.InitializeFrom(
              SemaRef, Entity,
              InitializationKind::CreateValue(Loc, Loc, Loc, true),
              MultiExprArg(), /*TopLevelOfInitList=*/false,
              TreatUnavailableAsInvalid);
          // Emit a warning for this.  System header warnings aren't shown
          // by default, but people working on system headers should see it.
          if (!VerifyOnly) {
            SemaRef.Diag(CtorDecl->getLocation(),
                         diag::warn_invalid_initializer_from_system_header);
            if (Entity.getKind() == InitializedEntity::EK_Member)
              SemaRef.Diag(Entity.getDecl()->getLocation(),
                           diag::note_used_in_initialization_here);
            else if (Entity.getKind() == InitializedEntity::EK_ArrayElement)
              SemaRef.Diag(Loc, diag::note_used_in_initialization_here);
          }
        }
      }
    }
    if (!InitSeq) {
      if (!VerifyOnly) {
        InitSeq.Diagnose(SemaRef, Entity, Kind, SubInit);
        if (Entity.getKind() == InitializedEntity::EK_Member)
          SemaRef.Diag(Entity.getDecl()->getLocation(),
                       diag::note_in_omitted_aggregate_initializer)
            << /*field*/1 << Entity.getDecl();
        else if (Entity.getKind() == InitializedEntity::EK_ArrayElement) {
          bool IsTrailingArrayNewMember =
              Entity.getParent() &&
              Entity.getParent()->isVariableLengthArrayNew();
          SemaRef.Diag(Loc, diag::note_in_omitted_aggregate_initializer)
            << (IsTrailingArrayNewMember ? 2 : /*array element*/0)
            << Entity.getElementIndex();
        }
      }
      hadError = true;
      return ExprError();
    }
  
    return VerifyOnly ? ExprResult()
                      : InitSeq.Perform(SemaRef, Entity, Kind, SubInit);
  }
  
  void InitListChecker::CheckEmptyInitializable(const InitializedEntity &Entity,
                                                SourceLocation Loc) {
    // If we're building a fully-structured list, we'll check this at the end
    // once we know which elements are actually initialized. Otherwise, we know
    // that there are no designators so we can just check now.
    if (FullyStructuredList)
      return;
    PerformEmptyInit(Loc, Entity);
  }
  
  void InitListChecker::FillInEmptyInitForBase(
      unsigned Init, const CXXBaseSpecifier &Base,
      const InitializedEntity &ParentEntity, InitListExpr *ILE,
      bool &RequiresSecondPass, bool FillWithNoInit) {
    InitializedEntity BaseEntity = InitializedEntity::InitializeBase(
        SemaRef.Context, &Base, false, &ParentEntity);
  
    if (Init >= ILE->getNumInits() || !ILE->getInit(Init)) {
      ExprResult BaseInit = FillWithNoInit
                                ? new (SemaRef.Context) NoInitExpr(Base.getType())
                                : PerformEmptyInit(ILE->getEndLoc(), BaseEntity);
      if (BaseInit.isInvalid()) {
        hadError = true;
        return;
      }
  
      if (!VerifyOnly) {
        assert(Init < ILE->getNumInits() && "should have been expanded");
        ILE->setInit(Init, BaseInit.getAs<Expr>());
      }
    } else if (InitListExpr *InnerILE =
                   dyn_cast<InitListExpr>(ILE->getInit(Init))) {
      FillInEmptyInitializations(BaseEntity, InnerILE, RequiresSecondPass,
                                 ILE, Init, FillWithNoInit);
    } else if (DesignatedInitUpdateExpr *InnerDIUE =
                 dyn_cast<DesignatedInitUpdateExpr>(ILE->getInit(Init))) {
      FillInEmptyInitializations(BaseEntity, InnerDIUE->getUpdater(),
                                 RequiresSecondPass, ILE, Init,
                                 /*FillWithNoInit =*/true);
    }
  }
  
  void InitListChecker::FillInEmptyInitForField(unsigned Init, FieldDecl *Field,
                                          const InitializedEntity &ParentEntity,
                                                InitListExpr *ILE,
                                                bool &RequiresSecondPass,
                                                bool FillWithNoInit) {
    SourceLocation Loc = ILE->getEndLoc();
    unsigned NumInits = ILE->getNumInits();
    InitializedEntity MemberEntity
      = InitializedEntity::InitializeMember(Field, &ParentEntity);
  
    if (Init >= NumInits || !ILE->getInit(Init)) {
      if (const RecordType *RType = ILE->getType()->getAs<RecordType>())
        if (!RType->getDecl()->isUnion())
          assert((Init < NumInits || VerifyOnly) &&
                 "This ILE should have been expanded");
  
      if (FillWithNoInit) {
        assert(!VerifyOnly && "should not fill with no-init in verify-only mode");
        Expr *Filler = new (SemaRef.Context) NoInitExpr(Field->getType());
        if (Init < NumInits)
          ILE->setInit(Init, Filler);
        else
          ILE->updateInit(SemaRef.Context, Init, Filler);
        return;
      }
      // C++1y [dcl.init.aggr]p7:
      //   If there are fewer initializer-clauses in the list than there are
      //   members in the aggregate, then each member not explicitly initialized
      //   shall be initialized from its brace-or-equal-initializer [...]
      if (Field->hasInClassInitializer()) {
        if (VerifyOnly)
          return;
  
        ExprResult DIE = SemaRef.BuildCXXDefaultInitExpr(Loc, Field);
        if (DIE.isInvalid()) {
          hadError = true;
          return;
        }
        SemaRef.checkInitializerLifetime(MemberEntity, DIE.get());
        if (Init < NumInits)
          ILE->setInit(Init, DIE.get());
        else {
          ILE->updateInit(SemaRef.Context, Init, DIE.get());
          RequiresSecondPass = true;
        }
        return;
      }
  
      if (Field->getType()->isReferenceType()) {
        if (!VerifyOnly) {
          // C++ [dcl.init.aggr]p9:
          //   If an incomplete or empty initializer-list leaves a
          //   member of reference type uninitialized, the program is
          //   ill-formed.
          SemaRef.Diag(Loc, diag::err_init_reference_member_uninitialized)
            << Field->getType()
            << ILE->getSyntacticForm()->getSourceRange();
          SemaRef.Diag(Field->getLocation(),
                       diag::note_uninit_reference_member);
        }
        hadError = true;
        return;
      }
  
      ExprResult MemberInit = PerformEmptyInit(Loc, MemberEntity);
      if (MemberInit.isInvalid()) {
        hadError = true;
        return;
      }
  
      if (hadError || VerifyOnly) {
        // Do nothing
      } else if (Init < NumInits) {
        ILE->setInit(Init, MemberInit.getAs<Expr>());
      } else if (!isa<ImplicitValueInitExpr>(MemberInit.get())) {
        // Empty initialization requires a constructor call, so
        // extend the initializer list to include the constructor
        // call and make a note that we'll need to take another pass
        // through the initializer list.
        ILE->updateInit(SemaRef.Context, Init, MemberInit.getAs<Expr>());
        RequiresSecondPass = true;
      }
    } else if (InitListExpr *InnerILE
                 = dyn_cast<InitListExpr>(ILE->getInit(Init))) {
      FillInEmptyInitializations(MemberEntity, InnerILE,
                                 RequiresSecondPass, ILE, Init, FillWithNoInit);
    } else if (DesignatedInitUpdateExpr *InnerDIUE =
                   dyn_cast<DesignatedInitUpdateExpr>(ILE->getInit(Init))) {
      FillInEmptyInitializations(MemberEntity, InnerDIUE->getUpdater(),
                                 RequiresSecondPass, ILE, Init,
                                 /*FillWithNoInit =*/true);
    }
  }
  
  /// Recursively replaces NULL values within the given initializer list
  /// with expressions that perform value-initialization of the
  /// appropriate type, and finish off the InitListExpr formation.
  void
  InitListChecker::FillInEmptyInitializations(const InitializedEntity &Entity,
                                              InitListExpr *ILE,
                                              bool &RequiresSecondPass,
                                              InitListExpr *OuterILE,
                                              unsigned OuterIndex,
                                              bool FillWithNoInit) {
    assert((ILE->getType() != SemaRef.Context.VoidTy) &&
           "Should not have void type");
  
    // We don't need to do any checks when just filling NoInitExprs; that can't
    // fail.
    if (FillWithNoInit && VerifyOnly)
      return;
  
    // If this is a nested initializer list, we might have changed its contents
    // (and therefore some of its properties, such as instantiation-dependence)
    // while filling it in. Inform the outer initializer list so that its state
    // can be updated to match.
    // FIXME: We should fully build the inner initializers before constructing
    // the outer InitListExpr instead of mutating AST nodes after they have
    // been used as subexpressions of other nodes.
    struct UpdateOuterILEWithUpdatedInit {
      InitListExpr *Outer;
      unsigned OuterIndex;
      ~UpdateOuterILEWithUpdatedInit() {
        if (Outer)
          Outer->setInit(OuterIndex, Outer->getInit(OuterIndex));
      }
    } UpdateOuterRAII = {OuterILE, OuterIndex};
  
    // A transparent ILE is not performing aggregate initialization and should
    // not be filled in.
    if (ILE->isTransparent())
      return;
  
    if (const RecordType *RType = ILE->getType()->getAs<RecordType>()) {
      const RecordDecl *RDecl = RType->getDecl();
      if (RDecl->isUnion() && ILE->getInitializedFieldInUnion())
        FillInEmptyInitForField(0, ILE->getInitializedFieldInUnion(),
                                Entity, ILE, RequiresSecondPass, FillWithNoInit);
      else if (RDecl->isUnion() && isa<CXXRecordDecl>(RDecl) &&
               cast<CXXRecordDecl>(RDecl)->hasInClassInitializer()) {
        for (auto *Field : RDecl->fields()) {
          if (Field->hasInClassInitializer()) {
            FillInEmptyInitForField(0, Field, Entity, ILE, RequiresSecondPass,
                                    FillWithNoInit);
            break;
          }
        }
      } else {
        // The fields beyond ILE->getNumInits() are default initialized, so in
        // order to leave them uninitialized, the ILE is expanded and the extra
        // fields are then filled with NoInitExpr.
        unsigned NumElems = numStructUnionElements(ILE->getType());
        if (RDecl->hasFlexibleArrayMember())
          ++NumElems;
        if (!VerifyOnly && ILE->getNumInits() < NumElems)
          ILE->resizeInits(SemaRef.Context, NumElems);
  
        unsigned Init = 0;
  
        if (auto *CXXRD = dyn_cast<CXXRecordDecl>(RDecl)) {
          for (auto &Base : CXXRD->bases()) {
            if (hadError)
              return;
  
            FillInEmptyInitForBase(Init, Base, Entity, ILE, RequiresSecondPass,
                                   FillWithNoInit);
            ++Init;
          }
        }
  
        for (auto *Field : RDecl->fields()) {
          if (Field->isUnnamedBitfield())
            continue;
  
          if (hadError)
            return;
  
          FillInEmptyInitForField(Init, Field, Entity, ILE, RequiresSecondPass,
                                  FillWithNoInit);
          if (hadError)
            return;
  
          ++Init;
  
          // Only look at the first initialization of a union.
          if (RDecl->isUnion())
            break;
        }
      }
  
      return;
    }
  
    QualType ElementType;
  
    InitializedEntity ElementEntity = Entity;
    unsigned NumInits = ILE->getNumInits();
    unsigned NumElements = NumInits;
    if (const ArrayType *AType = SemaRef.Context.getAsArrayType(ILE->getType())) {
      ElementType = AType->getElementType();
      if (const auto *CAType = dyn_cast<ConstantArrayType>(AType))
        NumElements = CAType->getSize().getZExtValue();
      // For an array new with an unknown bound, ask for one additional element
      // in order to populate the array filler.
      if (Entity.isVariableLengthArrayNew())
        ++NumElements;
      ElementEntity = InitializedEntity::InitializeElement(SemaRef.Context,
                                                           0, Entity);
    } else if (const VectorType *VType = ILE->getType()->getAs<VectorType>()) {
      ElementType = VType->getElementType();
      NumElements = VType->getNumElements();
      ElementEntity = InitializedEntity::InitializeElement(SemaRef.Context,
                                                           0, Entity);
    } else
      ElementType = ILE->getType();
  
    bool SkipEmptyInitChecks = false;
    for (unsigned Init = 0; Init != NumElements; ++Init) {
      if (hadError)
        return;
  
      if (ElementEntity.getKind() == InitializedEntity::EK_ArrayElement ||
          ElementEntity.getKind() == InitializedEntity::EK_VectorElement)
        ElementEntity.setElementIndex(Init);
  
      if (Init >= NumInits && (ILE->hasArrayFiller() || SkipEmptyInitChecks))
        return;
  
      Expr *InitExpr = (Init < NumInits ? ILE->getInit(Init) : nullptr);
      if (!InitExpr && Init < NumInits && ILE->hasArrayFiller())
        ILE->setInit(Init, ILE->getArrayFiller());
      else if (!InitExpr && !ILE->hasArrayFiller()) {
        // In VerifyOnly mode, there's no point performing empty initialization
        // more than once.
        if (SkipEmptyInitChecks)
          continue;
  
        Expr *Filler = nullptr;
  
        if (FillWithNoInit)
          Filler = new (SemaRef.Context) NoInitExpr(ElementType);
        else {
          ExprResult ElementInit =
              PerformEmptyInit(ILE->getEndLoc(), ElementEntity);
          if (ElementInit.isInvalid()) {
            hadError = true;
            return;
          }
  
          Filler = ElementInit.getAs<Expr>();
        }
  
        if (hadError) {
          // Do nothing
        } else if (VerifyOnly) {
          SkipEmptyInitChecks = true;
        } else if (Init < NumInits) {
          // For arrays, just set the expression used for value-initialization
          // of the "holes" in the array.
          if (ElementEntity.getKind() == InitializedEntity::EK_ArrayElement)
            ILE->setArrayFiller(Filler);
          else
            ILE->setInit(Init, Filler);
        } else {
          // For arrays, just set the expression used for value-initialization
          // of the rest of elements and exit.
          if (ElementEntity.getKind() == InitializedEntity::EK_ArrayElement) {
            ILE->setArrayFiller(Filler);
            return;
          }
  
          if (!isa<ImplicitValueInitExpr>(Filler) && !isa<NoInitExpr>(Filler)) {
            // Empty initialization requires a constructor call, so
            // extend the initializer list to include the constructor
            // call and make a note that we'll need to take another pass
            // through the initializer list.
            ILE->updateInit(SemaRef.Context, Init, Filler);
            RequiresSecondPass = true;
          }
        }
      } else if (InitListExpr *InnerILE
                   = dyn_cast_or_null<InitListExpr>(InitExpr)) {
        FillInEmptyInitializations(ElementEntity, InnerILE, RequiresSecondPass,
                                   ILE, Init, FillWithNoInit);
      } else if (DesignatedInitUpdateExpr *InnerDIUE =
                     dyn_cast_or_null<DesignatedInitUpdateExpr>(InitExpr)) {
        FillInEmptyInitializations(ElementEntity, InnerDIUE->getUpdater(),
                                   RequiresSecondPass, ILE, Init,
                                   /*FillWithNoInit =*/true);
      }
    }
  }
  
  static bool hasAnyDesignatedInits(const InitListExpr *IL) {
    for (const Stmt *Init : *IL)
      if (Init && isa<DesignatedInitExpr>(Init))
        return true;
    return false;
  }
  
  InitListChecker::InitListChecker(Sema &S, const InitializedEntity &Entity,
                                   InitListExpr *IL, QualType &T, bool VerifyOnly,
                                   bool TreatUnavailableAsInvalid,
                                   bool InOverloadResolution)
      : SemaRef(S), VerifyOnly(VerifyOnly),
        TreatUnavailableAsInvalid(TreatUnavailableAsInvalid),
        InOverloadResolution(InOverloadResolution) {
    if (!VerifyOnly || hasAnyDesignatedInits(IL)) {
      FullyStructuredList =
          createInitListExpr(T, IL->getSourceRange(), IL->getNumInits());
  
      // FIXME: Check that IL isn't already the semantic form of some other
      // InitListExpr. If it is, we'd create a broken AST.
      if (!VerifyOnly)
        FullyStructuredList->setSyntacticForm(IL);
    }
  
    CheckExplicitInitList(Entity, IL, T, FullyStructuredList,
                          /*TopLevelObject=*/true);
  
    if (!hadError && FullyStructuredList) {
      bool RequiresSecondPass = false;
      FillInEmptyInitializations(Entity, FullyStructuredList, RequiresSecondPass,
                                 /*OuterILE=*/nullptr, /*OuterIndex=*/0);
      if (RequiresSecondPass && !hadError)
        FillInEmptyInitializations(Entity, FullyStructuredList,
                                   RequiresSecondPass, nullptr, 0);
    }
  }
  
  int InitListChecker::numArrayElements(QualType DeclType) {
    // FIXME: use a proper constant
    int maxElements = 0x7FFFFFFF;
    if (const ConstantArrayType *CAT =
          SemaRef.Context.getAsConstantArrayType(DeclType)) {
      maxElements = static_cast<int>(CAT->getSize().getZExtValue());
    }
    return maxElements;
  }
  
  int InitListChecker::numStructUnionElements(QualType DeclType) {
    RecordDecl *structDecl = DeclType->castAs<RecordType>()->getDecl();
    int InitializableMembers = 0;
    if (auto *CXXRD = dyn_cast<CXXRecordDecl>(structDecl))
      InitializableMembers += CXXRD->getNumBases();
    for (const auto *Field : structDecl->fields())
      if (!Field->isUnnamedBitfield())
        ++InitializableMembers;
  
    if (structDecl->isUnion())
      return std::min(InitializableMembers, 1);
    return InitializableMembers - structDecl->hasFlexibleArrayMember();
  }
  
  /// Determine whether Entity is an entity for which it is idiomatic to elide
  /// the braces in aggregate initialization.
  static bool isIdiomaticBraceElisionEntity(const InitializedEntity &Entity) {
    // Recursive initialization of the one and only field within an aggregate
    // class is considered idiomatic. This case arises in particular for
    // initialization of std::array, where the C++ standard suggests the idiom of
    //
    //   std::array<T, N> arr = {1, 2, 3};
    //
    // (where std::array is an aggregate struct containing a single array field.
  
    // FIXME: Should aggregate initialization of a struct with a single
    // base class and no members also suppress the warning?
    if (Entity.getKind() != InitializedEntity::EK_Member || !Entity.getParent())
      return false;
  
    auto *ParentRD =
        Entity.getParent()->getType()->castAs<RecordType>()->getDecl();
    if (CXXRecordDecl *CXXRD = dyn_cast<CXXRecordDecl>(ParentRD))
      if (CXXRD->getNumBases())
        return false;
  
    auto FieldIt = ParentRD->field_begin();
    assert(FieldIt != ParentRD->field_end() &&
           "no fields but have initializer for member?");
    return ++FieldIt == ParentRD->field_end();
  }
  
  /// Check whether the range of the initializer \p ParentIList from element
  /// \p Index onwards can be used to initialize an object of type \p T. Update
  /// \p Index to indicate how many elements of the list were consumed.
  ///
  /// This also fills in \p StructuredList, from element \p StructuredIndex
  /// onwards, with the fully-braced, desugared form of the initialization.
  void InitListChecker::CheckImplicitInitList(const InitializedEntity &Entity,
                                              InitListExpr *ParentIList,
                                              QualType T, unsigned &Index,
                                              InitListExpr *StructuredList,
                                              unsigned &StructuredIndex) {
    int maxElements = 0;
  
    if (T->isArrayType())
      maxElements = numArrayElements(T);
    else if (T->isRecordType())
      maxElements = numStructUnionElements(T);
    else if (T->isVectorType())
      maxElements = T->castAs<VectorType>()->getNumElements();
    else
      llvm_unreachable("CheckImplicitInitList(): Illegal type");
  
    if (maxElements == 0) {
      if (!VerifyOnly)
        SemaRef.Diag(ParentIList->getInit(Index)->getBeginLoc(),
                     diag::err_implicit_empty_initializer);
      ++Index;
      hadError = true;
      return;
    }
  
    // Build a structured initializer list corresponding to this subobject.
    InitListExpr *StructuredSubobjectInitList = getStructuredSubobjectInit(
        ParentIList, Index, T, StructuredList, StructuredIndex,
        SourceRange(ParentIList->getInit(Index)->getBeginLoc(),
                    ParentIList->getSourceRange().getEnd()));
    unsigned StructuredSubobjectInitIndex = 0;
  
    // Check the element types and build the structural subobject.
    unsigned StartIndex = Index;
    CheckListElementTypes(Entity, ParentIList, T,
                          /*SubobjectIsDesignatorContext=*/false, Index,
                          StructuredSubobjectInitList,
                          StructuredSubobjectInitIndex);
  
    if (StructuredSubobjectInitList) {
      StructuredSubobjectInitList->setType(T);
  
      unsigned EndIndex = (Index == StartIndex? StartIndex : Index - 1);
      // Update the structured sub-object initializer so that it's ending
      // range corresponds with the end of the last initializer it used.
      if (EndIndex < ParentIList->getNumInits() &&
          ParentIList->getInit(EndIndex)) {
        SourceLocation EndLoc
          = ParentIList->getInit(EndIndex)->getSourceRange().getEnd();
        StructuredSubobjectInitList->setRBraceLoc(EndLoc);
      }
  
      // Complain about missing braces.
      if (!VerifyOnly && (T->isArrayType() || T->isRecordType()) &&
          !ParentIList->isIdiomaticZeroInitializer(SemaRef.getLangOpts()) &&
          !isIdiomaticBraceElisionEntity(Entity)) {
        SemaRef.Diag(StructuredSubobjectInitList->getBeginLoc(),
                     diag::warn_missing_braces)
            << StructuredSubobjectInitList->getSourceRange()
            << FixItHint::CreateInsertion(
                   StructuredSubobjectInitList->getBeginLoc(), "{")
            << FixItHint::CreateInsertion(
                   SemaRef.getLocForEndOfToken(
                       StructuredSubobjectInitList->getEndLoc()),
                   "}");
      }
  
      // Warn if this type won't be an aggregate in future versions of C++.
      auto *CXXRD = T->getAsCXXRecordDecl();
      if (!VerifyOnly && CXXRD && CXXRD->hasUserDeclaredConstructor()) {
        SemaRef.Diag(StructuredSubobjectInitList->getBeginLoc(),
                     diag::warn_cxx20_compat_aggregate_init_with_ctors)
            << StructuredSubobjectInitList->getSourceRange() << T;
      }
    }
  }
  
  /// Warn that \p Entity was of scalar type and was initialized by a
  /// single-element braced initializer list.
  static void warnBracedScalarInit(Sema &S, const InitializedEntity &Entity,
                                   SourceRange Braces) {
    // Don't warn during template instantiation. If the initialization was
    // non-dependent, we warned during the initial parse; otherwise, the
    // type might not be scalar in some uses of the template.
    if (S.inTemplateInstantiation())
      return;
  
    unsigned DiagID = 0;
  
    switch (Entity.getKind()) {
    case InitializedEntity::EK_VectorElement:
    case InitializedEntity::EK_ComplexElement:
    case InitializedEntity::EK_ArrayElement:
    case InitializedEntity::EK_Parameter:
    case InitializedEntity::EK_Parameter_CF_Audited:
    case InitializedEntity::EK_Result:
      // Extra braces here are suspicious.
      DiagID = diag::warn_braces_around_init;
      break;
  
    case InitializedEntity::EK_Member:
      // Warn on aggregate initialization but not on ctor init list or
      // default member initializer.
      if (Entity.getParent())
        DiagID = diag::warn_braces_around_init;
      break;
  
    case InitializedEntity::EK_Variable:
    case InitializedEntity::EK_LambdaCapture:
      // No warning, might be direct-list-initialization.
      // FIXME: Should we warn for copy-list-initialization in these cases?
      break;
  
    case InitializedEntity::EK_New:
    case InitializedEntity::EK_Temporary:
    case InitializedEntity::EK_CompoundLiteralInit:
      // No warning, braces are part of the syntax of the underlying construct.
      break;
  
    case InitializedEntity::EK_RelatedResult:
      // No warning, we already warned when initializing the result.
      break;
  
    case InitializedEntity::EK_Exception:
    case InitializedEntity::EK_Base:
    case InitializedEntity::EK_Delegating:
    case InitializedEntity::EK_BlockElement:
    case InitializedEntity::EK_LambdaToBlockConversionBlockElement:
    case InitializedEntity::EK_Binding:
    case InitializedEntity::EK_StmtExprResult:
      llvm_unreachable("unexpected braced scalar init");
    }
  
    if (DiagID) {
      S.Diag(Braces.getBegin(), DiagID)
          << Entity.getType()->isSizelessBuiltinType() << Braces
          << FixItHint::CreateRemoval(Braces.getBegin())
          << FixItHint::CreateRemoval(Braces.getEnd());
    }
  }
  
  /// Check whether the initializer \p IList (that was written with explicit
  /// braces) can be used to initialize an object of type \p T.
  ///
  /// This also fills in \p StructuredList with the fully-braced, desugared
  /// form of the initialization.
  void InitListChecker::CheckExplicitInitList(const InitializedEntity &Entity,
                                              InitListExpr *IList, QualType &T,
                                              InitListExpr *StructuredList,
                                              bool TopLevelObject) {
    unsigned Index = 0, StructuredIndex = 0;
    CheckListElementTypes(Entity, IList, T, /*SubobjectIsDesignatorContext=*/true,
                          Index, StructuredList, StructuredIndex, TopLevelObject);
    if (StructuredList) {
      QualType ExprTy = T;
      if (!ExprTy->isArrayType())
        ExprTy = ExprTy.getNonLValueExprType(SemaRef.Context);
      if (!VerifyOnly)
        IList->setType(ExprTy);
      StructuredList->setType(ExprTy);
    }
    if (hadError)
      return;
  
    // Don't complain for incomplete types, since we'll get an error elsewhere.
    if (Index < IList->getNumInits() && !T->isIncompleteType()) {
      // We have leftover initializers
      bool ExtraInitsIsError = SemaRef.getLangOpts().CPlusPlus ||
            (SemaRef.getLangOpts().OpenCL && T->isVectorType());
      hadError = ExtraInitsIsError;
      if (VerifyOnly) {
        return;
      } else if (StructuredIndex == 1 &&
                 IsStringInit(StructuredList->getInit(0), T, SemaRef.Context) ==
                     SIF_None) {
        unsigned DK =
            ExtraInitsIsError
                ? diag::err_excess_initializers_in_char_array_initializer
                : diag::ext_excess_initializers_in_char_array_initializer;
        SemaRef.Diag(IList->getInit(Index)->getBeginLoc(), DK)
            << IList->getInit(Index)->getSourceRange();
      } else if (T->isSizelessBuiltinType()) {
        unsigned DK = ExtraInitsIsError
                          ? diag::err_excess_initializers_for_sizeless_type
                          : diag::ext_excess_initializers_for_sizeless_type;
        SemaRef.Diag(IList->getInit(Index)->getBeginLoc(), DK)
            << T << IList->getInit(Index)->getSourceRange();
      } else {
        int initKind = T->isArrayType() ? 0 :
                       T->isVectorType() ? 1 :
                       T->isScalarType() ? 2 :
                       T->isUnionType() ? 3 :
                       4;
  
        unsigned DK = ExtraInitsIsError ? diag::err_excess_initializers
                                        : diag::ext_excess_initializers;
        SemaRef.Diag(IList->getInit(Index)->getBeginLoc(), DK)
            << initKind << IList->getInit(Index)->getSourceRange();
      }
    }
  
    if (!VerifyOnly) {
      if (T->isScalarType() && IList->getNumInits() == 1 &&
          !isa<InitListExpr>(IList->getInit(0)))
        warnBracedScalarInit(SemaRef, Entity, IList->getSourceRange());
  
      // Warn if this is a class type that won't be an aggregate in future
      // versions of C++.
      auto *CXXRD = T->getAsCXXRecordDecl();
      if (CXXRD && CXXRD->hasUserDeclaredConstructor()) {
        // Don't warn if there's an equivalent default constructor that would be
        // used instead.
        bool HasEquivCtor = false;
        if (IList->getNumInits() == 0) {
          auto *CD = SemaRef.LookupDefaultConstructor(CXXRD);
          HasEquivCtor = CD && !CD->isDeleted();
        }
  
        if (!HasEquivCtor) {
          SemaRef.Diag(IList->getBeginLoc(),
                       diag::warn_cxx20_compat_aggregate_init_with_ctors)
              << IList->getSourceRange() << T;
        }
      }
    }
  }
  
  void InitListChecker::CheckListElementTypes(const InitializedEntity &Entity,
                                              InitListExpr *IList,
                                              QualType &DeclType,
                                              bool SubobjectIsDesignatorContext,
                                              unsigned &Index,
                                              InitListExpr *StructuredList,
                                              unsigned &StructuredIndex,
                                              bool TopLevelObject) {
    if (DeclType->isAnyComplexType() && SubobjectIsDesignatorContext) {
      // Explicitly braced initializer for complex type can be real+imaginary
      // parts.
      CheckComplexType(Entity, IList, DeclType, Index,
                       StructuredList, StructuredIndex);
    } else if (DeclType->isScalarType()) {
      CheckScalarType(Entity, IList, DeclType, Index,
                      StructuredList, StructuredIndex);
    } else if (DeclType->isVectorType()) {
      CheckVectorType(Entity, IList, DeclType, Index,
                      StructuredList, StructuredIndex);
    } else if (DeclType->isRecordType()) {
      assert(DeclType->isAggregateType() &&
             "non-aggregate records should be handed in CheckSubElementType");
      RecordDecl *RD = DeclType->castAs<RecordType>()->getDecl();
      auto Bases =
          CXXRecordDecl::base_class_range(CXXRecordDecl::base_class_iterator(),
                                          CXXRecordDecl::base_class_iterator());
      if (auto *CXXRD = dyn_cast<CXXRecordDecl>(RD))
        Bases = CXXRD->bases();
      CheckStructUnionTypes(Entity, IList, DeclType, Bases, RD->field_begin(),
                            SubobjectIsDesignatorContext, Index, StructuredList,
                            StructuredIndex, TopLevelObject);
    } else if (DeclType->isArrayType()) {
      llvm::APSInt Zero(
                      SemaRef.Context.getTypeSize(SemaRef.Context.getSizeType()),
                      false);
      CheckArrayType(Entity, IList, DeclType, Zero,
                     SubobjectIsDesignatorContext, Index,
                     StructuredList, StructuredIndex);
    } else if (DeclType->isVoidType() || DeclType->isFunctionType()) {
      // This type is invalid, issue a diagnostic.
      ++Index;
      if (!VerifyOnly)
        SemaRef.Diag(IList->getBeginLoc(), diag::err_illegal_initializer_type)
            << DeclType;
      hadError = true;
    } else if (DeclType->isReferenceType()) {
      CheckReferenceType(Entity, IList, DeclType, Index,
                         StructuredList, StructuredIndex);
    } else if (DeclType->isObjCObjectType()) {
      if (!VerifyOnly)
        SemaRef.Diag(IList->getBeginLoc(), diag::err_init_objc_class) << DeclType;
      hadError = true;
    } else if (DeclType->isOCLIntelSubgroupAVCType() ||
               DeclType->isSizelessBuiltinType()) {
      // Checks for scalar type are sufficient for these types too.
      CheckScalarType(Entity, IList, DeclType, Index, StructuredList,
                      StructuredIndex);
    } else {
      if (!VerifyOnly)
        SemaRef.Diag(IList->getBeginLoc(), diag::err_illegal_initializer_type)
            << DeclType;
      hadError = true;
    }
  }
  
  void InitListChecker::CheckSubElementType(const InitializedEntity &Entity,
                                            InitListExpr *IList,
                                            QualType ElemType,
                                            unsigned &Index,
                                            InitListExpr *StructuredList,
                                            unsigned &StructuredIndex) {
    Expr *expr = IList->getInit(Index);
  
    if (ElemType->isReferenceType())
      return CheckReferenceType(Entity, IList, ElemType, Index,
                                StructuredList, StructuredIndex);
  
    if (InitListExpr *SubInitList = dyn_cast<InitListExpr>(expr)) {
      if (SubInitList->getNumInits() == 1 &&
          IsStringInit(SubInitList->getInit(0), ElemType, SemaRef.Context) ==
          SIF_None) {
        // FIXME: It would be more faithful and no less correct to include an
        // InitListExpr in the semantic form of the initializer list in this case.
        expr = SubInitList->getInit(0);
      }
      // Nested aggregate initialization and C++ initialization are handled later.
    } else if (isa<ImplicitValueInitExpr>(expr)) {
      // This happens during template instantiation when we see an InitListExpr
      // that we've already checked once.
      assert(SemaRef.Context.hasSameType(expr->getType(), ElemType) &&
             "found implicit initialization for the wrong type");
      UpdateStructuredListElement(StructuredList, StructuredIndex, expr);
      ++Index;
      return;
    }
  
    if (SemaRef.getLangOpts().CPlusPlus || isa<InitListExpr>(expr)) {
      // C++ [dcl.init.aggr]p2:
      //   Each member is copy-initialized from the corresponding
      //   initializer-clause.
  
      // FIXME: Better EqualLoc?
      InitializationKind Kind =
          InitializationKind::CreateCopy(expr->getBeginLoc(), SourceLocation());
  
      // Vector elements can be initialized from other vectors in which case
      // we need initialization entity with a type of a vector (and not a vector
      // element!) initializing multiple vector elements.
      auto TmpEntity =
          (ElemType->isExtVectorType() && !Entity.getType()->isExtVectorType())
              ? InitializedEntity::InitializeTemporary(ElemType)
              : Entity;
  
      InitializationSequence Seq(SemaRef, TmpEntity, Kind, expr,
                                 /*TopLevelOfInitList*/ true);
  
      // C++14 [dcl.init.aggr]p13:
      //   If the assignment-expression can initialize a member, the member is
      //   initialized. Otherwise [...] brace elision is assumed
      //
      // Brace elision is never performed if the element is not an
      // assignment-expression.
      if (Seq || isa<InitListExpr>(expr)) {
        if (!VerifyOnly) {
          ExprResult Result = Seq.Perform(SemaRef, TmpEntity, Kind, expr);
          if (Result.isInvalid())
            hadError = true;
  
          UpdateStructuredListElement(StructuredList, StructuredIndex,
                                      Result.getAs<Expr>());
        } else if (!Seq) {
          hadError = true;
        } else if (StructuredList) {
          UpdateStructuredListElement(StructuredList, StructuredIndex,
                                      getDummyInit());
        }
        ++Index;
        return;
      }
  
      // Fall through for subaggregate initialization
    } else if (ElemType->isScalarType() || ElemType->isAtomicType()) {
      // FIXME: Need to handle atomic aggregate types with implicit init lists.
      return CheckScalarType(Entity, IList, ElemType, Index,
                             StructuredList, StructuredIndex);
    } else if (const ArrayType *arrayType =
                   SemaRef.Context.getAsArrayType(ElemType)) {
      // arrayType can be incomplete if we're initializing a flexible
      // array member.  There's nothing we can do with the completed
      // type here, though.
  
      if (IsStringInit(expr, arrayType, SemaRef.Context) == SIF_None) {
        // FIXME: Should we do this checking in verify-only mode?
        if (!VerifyOnly)
          CheckStringInit(expr, ElemType, arrayType, SemaRef);
        if (StructuredList)
          UpdateStructuredListElement(StructuredList, StructuredIndex, expr);
        ++Index;
        return;
      }
  
      // Fall through for subaggregate initialization.
  
    } else {
      assert((ElemType->isRecordType() || ElemType->isVectorType() ||
              ElemType->isOpenCLSpecificType()) && "Unexpected type");
  
      // C99 6.7.8p13:
      //
      //   The initializer for a structure or union object that has
      //   automatic storage duration shall be either an initializer
      //   list as described below, or a single expression that has
      //   compatible structure or union type. In the latter case, the
      //   initial value of the object, including unnamed members, is
      //   that of the expression.
      ExprResult ExprRes = expr;
      if (SemaRef.CheckSingleAssignmentConstraints(
              ElemType, ExprRes, !VerifyOnly) != Sema::Incompatible) {
        if (ExprRes.isInvalid())
          hadError = true;
        else {
          ExprRes = SemaRef.DefaultFunctionArrayLvalueConversion(ExprRes.get());
          if (ExprRes.isInvalid())
            hadError = true;
        }
        UpdateStructuredListElement(StructuredList, StructuredIndex,
                                    ExprRes.getAs<Expr>());
        ++Index;
        return;
      }
      ExprRes.get();
      // Fall through for subaggregate initialization
    }
  
    // C++ [dcl.init.aggr]p12:
    //
    //   [...] Otherwise, if the member is itself a non-empty
    //   subaggregate, brace elision is assumed and the initializer is
    //   considered for the initialization of the first member of
    //   the subaggregate.
    // OpenCL vector initializer is handled elsewhere.
    if ((!SemaRef.getLangOpts().OpenCL && ElemType->isVectorType()) ||
        ElemType->isAggregateType()) {
      CheckImplicitInitList(Entity, IList, ElemType, Index, StructuredList,
                            StructuredIndex);
      ++StructuredIndex;
    } else {
      if (!VerifyOnly) {
        // We cannot initialize this element, so let PerformCopyInitialization
        // produce the appropriate diagnostic. We already checked that this
        // initialization will fail.
        ExprResult Copy =
            SemaRef.PerformCopyInitialization(Entity, SourceLocation(), expr,
                                              /*TopLevelOfInitList=*/true);
        (void)Copy;
        assert(Copy.isInvalid() &&
               "expected non-aggregate initialization to fail");
      }
      hadError = true;
      ++Index;
      ++StructuredIndex;
    }
  }
  
  void InitListChecker::CheckComplexType(const InitializedEntity &Entity,
                                         InitListExpr *IList, QualType DeclType,
                                         unsigned &Index,
                                         InitListExpr *StructuredList,
                                         unsigned &StructuredIndex) {
    assert(Index == 0 && "Index in explicit init list must be zero");
  
    // As an extension, clang supports complex initializers, which initialize
    // a complex number component-wise.  When an explicit initializer list for
    // a complex number contains two two initializers, this extension kicks in:
    // it exepcts the initializer list to contain two elements convertible to
    // the element type of the complex type. The first element initializes
    // the real part, and the second element intitializes the imaginary part.
  
    if (IList->getNumInits() != 2)
      return CheckScalarType(Entity, IList, DeclType, Index, StructuredList,
                             StructuredIndex);
  
    // This is an extension in C.  (The builtin _Complex type does not exist
    // in the C++ standard.)
    if (!SemaRef.getLangOpts().CPlusPlus && !VerifyOnly)
      SemaRef.Diag(IList->getBeginLoc(), diag::ext_complex_component_init)
          << IList->getSourceRange();
  
    // Initialize the complex number.
    QualType elementType = DeclType->castAs<ComplexType>()->getElementType();
    InitializedEntity ElementEntity =
      InitializedEntity::InitializeElement(SemaRef.Context, 0, Entity);
  
    for (unsigned i = 0; i < 2; ++i) {
      ElementEntity.setElementIndex(Index);
      CheckSubElementType(ElementEntity, IList, elementType, Index,
                          StructuredList, StructuredIndex);
    }
  }
  
  void InitListChecker::CheckScalarType(const InitializedEntity &Entity,
                                        InitListExpr *IList, QualType DeclType,
                                        unsigned &Index,
                                        InitListExpr *StructuredList,
                                        unsigned &StructuredIndex) {
    if (Index >= IList->getNumInits()) {
      if (!VerifyOnly) {
        if (DeclType->isSizelessBuiltinType())
          SemaRef.Diag(IList->getBeginLoc(),
                       SemaRef.getLangOpts().CPlusPlus11
                           ? diag::warn_cxx98_compat_empty_sizeless_initializer
                           : diag::err_empty_sizeless_initializer)
              << DeclType << IList->getSourceRange();
        else
          SemaRef.Diag(IList->getBeginLoc(),
                       SemaRef.getLangOpts().CPlusPlus11
                           ? diag::warn_cxx98_compat_empty_scalar_initializer
                           : diag::err_empty_scalar_initializer)
              << IList->getSourceRange();
      }
      hadError = !SemaRef.getLangOpts().CPlusPlus11;
      ++Index;
      ++StructuredIndex;
      return;
    }
  
    Expr *expr = IList->getInit(Index);
    if (InitListExpr *SubIList = dyn_cast<InitListExpr>(expr)) {
      // FIXME: This is invalid, and accepting it causes overload resolution
      // to pick the wrong overload in some corner cases.
      if (!VerifyOnly)
        SemaRef.Diag(SubIList->getBeginLoc(), diag::ext_many_braces_around_init)
            << DeclType->isSizelessBuiltinType() << SubIList->getSourceRange();
  
      CheckScalarType(Entity, SubIList, DeclType, Index, StructuredList,
                      StructuredIndex);
      return;
    } else if (isa<DesignatedInitExpr>(expr)) {
      if (!VerifyOnly)
        SemaRef.Diag(expr->getBeginLoc(),
                     diag::err_designator_for_scalar_or_sizeless_init)
            << DeclType->isSizelessBuiltinType() << DeclType
            << expr->getSourceRange();
      hadError = true;
      ++Index;
      ++StructuredIndex;
      return;
    }
  
    ExprResult Result;
    if (VerifyOnly) {
      if (SemaRef.CanPerformCopyInitialization(Entity, expr))
        Result = getDummyInit();
      else
        Result = ExprError();
    } else {
      Result =
          SemaRef.PerformCopyInitialization(Entity, expr->getBeginLoc(), expr,
                                            /*TopLevelOfInitList=*/true);
    }
  
    Expr *ResultExpr = nullptr;
  
    if (Result.isInvalid())
      hadError = true; // types weren't compatible.
    else {
      ResultExpr = Result.getAs<Expr>();
  
      if (ResultExpr != expr && !VerifyOnly) {
        // The type was promoted, update initializer list.
        // FIXME: Why are we updating the syntactic init list?
        IList->setInit(Index, ResultExpr);
      }
    }
    if (hadError)
      ++StructuredIndex;
    else
      UpdateStructuredListElement(StructuredList, StructuredIndex, ResultExpr);
    ++Index;
  }
  
  void InitListChecker::CheckReferenceType(const InitializedEntity &Entity,
                                           InitListExpr *IList, QualType DeclType,
                                           unsigned &Index,
                                           InitListExpr *StructuredList,
                                           unsigned &StructuredIndex) {
    if (Index >= IList->getNumInits()) {
      // FIXME: It would be wonderful if we could point at the actual member. In
      // general, it would be useful to pass location information down the stack,
      // so that we know the location (or decl) of the "current object" being
      // initialized.
      if (!VerifyOnly)
        SemaRef.Diag(IList->getBeginLoc(),
                     diag::err_init_reference_member_uninitialized)
            << DeclType << IList->getSourceRange();
      hadError = true;
      ++Index;
      ++StructuredIndex;
      return;
    }
  
    Expr *expr = IList->getInit(Index);
    if (isa<InitListExpr>(expr) && !SemaRef.getLangOpts().CPlusPlus11) {
      if (!VerifyOnly)
        SemaRef.Diag(IList->getBeginLoc(), diag::err_init_non_aggr_init_list)
            << DeclType << IList->getSourceRange();
      hadError = true;
      ++Index;
      ++StructuredIndex;
      return;
    }
  
    ExprResult Result;
    if (VerifyOnly) {
      if (SemaRef.CanPerformCopyInitialization(Entity,expr))
        Result = getDummyInit();
      else
        Result = ExprError();
    } else {
      Result =
          SemaRef.PerformCopyInitialization(Entity, expr->getBeginLoc(), expr,
                                            /*TopLevelOfInitList=*/true);
    }
  
    if (Result.isInvalid())
      hadError = true;
  
    expr = Result.getAs<Expr>();
    // FIXME: Why are we updating the syntactic init list?
    if (!VerifyOnly && expr)
      IList->setInit(Index, expr);
  
    if (hadError)
      ++StructuredIndex;
    else
      UpdateStructuredListElement(StructuredList, StructuredIndex, expr);
    ++Index;
  }
  
  void InitListChecker::CheckVectorType(const InitializedEntity &Entity,
                                        InitListExpr *IList, QualType DeclType,
                                        unsigned &Index,
                                        InitListExpr *StructuredList,
                                        unsigned &StructuredIndex) {
    const VectorType *VT = DeclType->castAs<VectorType>();
    unsigned maxElements = VT->getNumElements();
    unsigned numEltsInit = 0;
    QualType elementType = VT->getElementType();
  
    if (Index >= IList->getNumInits()) {
      // Make sure the element type can be value-initialized.
      CheckEmptyInitializable(
          InitializedEntity::InitializeElement(SemaRef.Context, 0, Entity),
          IList->getEndLoc());
      return;
    }
  
    if (!SemaRef.getLangOpts().OpenCL) {
      // If the initializing element is a vector, try to copy-initialize
      // instead of breaking it apart (which is doomed to failure anyway).
      Expr *Init = IList->getInit(Index);
      if (!isa<InitListExpr>(Init) && Init->getType()->isVectorType()) {
        ExprResult Result;
        if (VerifyOnly) {
          if (SemaRef.CanPerformCopyInitialization(Entity, Init))
            Result = getDummyInit();
          else
            Result = ExprError();
        } else {
          Result =
              SemaRef.PerformCopyInitialization(Entity, Init->getBeginLoc(), Init,
                                                /*TopLevelOfInitList=*/true);
        }
  
        Expr *ResultExpr = nullptr;
        if (Result.isInvalid())
          hadError = true; // types weren't compatible.
        else {
          ResultExpr = Result.getAs<Expr>();
  
          if (ResultExpr != Init && !VerifyOnly) {
            // The type was promoted, update initializer list.
            // FIXME: Why are we updating the syntactic init list?
            IList->setInit(Index, ResultExpr);
          }
        }
        if (hadError)
          ++StructuredIndex;
        else
          UpdateStructuredListElement(StructuredList, StructuredIndex,
                                      ResultExpr);
        ++Index;
        return;
      }
  
      InitializedEntity ElementEntity =
        InitializedEntity::InitializeElement(SemaRef.Context, 0, Entity);
  
      for (unsigned i = 0; i < maxElements; ++i, ++numEltsInit) {
        // Don't attempt to go past the end of the init list
        if (Index >= IList->getNumInits()) {
          CheckEmptyInitializable(ElementEntity, IList->getEndLoc());
          break;
        }
  
        ElementEntity.setElementIndex(Index);
        CheckSubElementType(ElementEntity, IList, elementType, Index,
                            StructuredList, StructuredIndex);
      }
  
      if (VerifyOnly)
        return;
  
      bool isBigEndian = SemaRef.Context.getTargetInfo().isBigEndian();
      const VectorType *T = Entity.getType()->castAs<VectorType>();
      if (isBigEndian && (T->getVectorKind() == VectorType::NeonVector ||
                          T->getVectorKind() == VectorType::NeonPolyVector)) {
        // The ability to use vector initializer lists is a GNU vector extension
        // and is unrelated to the NEON intrinsics in arm_neon.h. On little
        // endian machines it works fine, however on big endian machines it
        // exhibits surprising behaviour:
        //
        //   uint32x2_t x = {42, 64};
        //   return vget_lane_u32(x, 0); // Will return 64.
        //
        // Because of this, explicitly call out that it is non-portable.
        //
        SemaRef.Diag(IList->getBeginLoc(),
                     diag::warn_neon_vector_initializer_non_portable);
  
        const char *typeCode;
        unsigned typeSize = SemaRef.Context.getTypeSize(elementType);
  
        if (elementType->isFloatingType())
          typeCode = "f";
        else if (elementType->isSignedIntegerType())
          typeCode = "s";
        else if (elementType->isUnsignedIntegerType())
          typeCode = "u";
        else
          llvm_unreachable("Invalid element type!");
  
        SemaRef.Diag(IList->getBeginLoc(),
                     SemaRef.Context.getTypeSize(VT) > 64
                         ? diag::note_neon_vector_initializer_non_portable_q
                         : diag::note_neon_vector_initializer_non_portable)
            << typeCode << typeSize;
      }
  
      return;
    }
  
    InitializedEntity ElementEntity =
      InitializedEntity::InitializeElement(SemaRef.Context, 0, Entity);
  
    // OpenCL initializers allows vectors to be constructed from vectors.
    for (unsigned i = 0; i < maxElements; ++i) {
      // Don't attempt to go past the end of the init list
      if (Index >= IList->getNumInits())
        break;
  
      ElementEntity.setElementIndex(Index);
  
      QualType IType = IList->getInit(Index)->getType();
      if (!IType->isVectorType()) {
        CheckSubElementType(ElementEntity, IList, elementType, Index,
                            StructuredList, StructuredIndex);
        ++numEltsInit;
      } else {
        QualType VecType;
        const VectorType *IVT = IType->castAs<VectorType>();
        unsigned numIElts = IVT->getNumElements();
  
        if (IType->isExtVectorType())
          VecType = SemaRef.Context.getExtVectorType(elementType, numIElts);
        else
          VecType = SemaRef.Context.getVectorType(elementType, numIElts,
                                                  IVT->getVectorKind());
        CheckSubElementType(ElementEntity, IList, VecType, Index,
                            StructuredList, StructuredIndex);
        numEltsInit += numIElts;
      }
    }
  
    // OpenCL requires all elements to be initialized.
    if (numEltsInit != maxElements) {
      if (!VerifyOnly)
        SemaRef.Diag(IList->getBeginLoc(),
                     diag::err_vector_incorrect_num_initializers)
            << (numEltsInit < maxElements) << maxElements << numEltsInit;
      hadError = true;
    }
  }
  
  /// Check if the type of a class element has an accessible destructor, and marks
  /// it referenced. Returns true if we shouldn't form a reference to the
  /// destructor.
  ///
  /// Aggregate initialization requires a class element's destructor be
  /// accessible per 11.6.1 [dcl.init.aggr]:
  ///
  /// The destructor for each element of class type is potentially invoked
  /// (15.4 [class.dtor]) from the context where the aggregate initialization
  /// occurs.
  static bool checkDestructorReference(QualType ElementType, SourceLocation Loc,
                                       Sema &SemaRef) {
    auto *CXXRD = ElementType->getAsCXXRecordDecl();
    if (!CXXRD)
      return false;
  
    CXXDestructorDecl *Destructor = SemaRef.LookupDestructor(CXXRD);
    SemaRef.CheckDestructorAccess(Loc, Destructor,
                                  SemaRef.PDiag(diag::err_access_dtor_temp)
                                  << ElementType);
    SemaRef.MarkFunctionReferenced(Loc, Destructor);
    return SemaRef.DiagnoseUseOfDecl(Destructor, Loc);
  }
  
  void InitListChecker::CheckArrayType(const InitializedEntity &Entity,
                                       InitListExpr *IList, QualType &DeclType,
                                       llvm::APSInt elementIndex,
                                       bool SubobjectIsDesignatorContext,
                                       unsigned &Index,
                                       InitListExpr *StructuredList,
                                       unsigned &StructuredIndex) {
    const ArrayType *arrayType = SemaRef.Context.getAsArrayType(DeclType);
  
    if (!VerifyOnly) {
      if (checkDestructorReference(arrayType->getElementType(),
                                   IList->getEndLoc(), SemaRef)) {
        hadError = true;
        return;
      }
    }
  
    // Check for the special-case of initializing an array with a string.
    if (Index < IList->getNumInits()) {
      if (IsStringInit(IList->getInit(Index), arrayType, SemaRef.Context) ==
          SIF_None) {
        // We place the string literal directly into the resulting
        // initializer list. This is the only place where the structure
        // of the structured initializer list doesn't match exactly,
        // because doing so would involve allocating one character
        // constant for each string.
        // FIXME: Should we do these checks in verify-only mode too?
        if (!VerifyOnly)
          CheckStringInit(IList->getInit(Index), DeclType, arrayType, SemaRef);
        if (StructuredList) {
          UpdateStructuredListElement(StructuredList, StructuredIndex,
                                      IList->getInit(Index));
          StructuredList->resizeInits(SemaRef.Context, StructuredIndex);
        }
        ++Index;
        return;
      }
    }
    if (const VariableArrayType *VAT = dyn_cast<VariableArrayType>(arrayType)) {
      // Check for VLAs; in standard C it would be possible to check this
      // earlier, but I don't know where clang accepts VLAs (gcc accepts
      // them in all sorts of strange places).
      if (!VerifyOnly)
        SemaRef.Diag(VAT->getSizeExpr()->getBeginLoc(),
                     diag::err_variable_object_no_init)
            << VAT->getSizeExpr()->getSourceRange();
      hadError = true;
      ++Index;
      ++StructuredIndex;
      return;
    }
  
    // We might know the maximum number of elements in advance.
    llvm::APSInt maxElements(elementIndex.getBitWidth(),
                             elementIndex.isUnsigned());
    bool maxElementsKnown = false;
    if (const ConstantArrayType *CAT = dyn_cast<ConstantArrayType>(arrayType)) {
      maxElements = CAT->getSize();
      elementIndex = elementIndex.extOrTrunc(maxElements.getBitWidth());
      elementIndex.setIsUnsigned(maxElements.isUnsigned());
      maxElementsKnown = true;
    }
  
    QualType elementType = arrayType->getElementType();
    while (Index < IList->getNumInits()) {
      Expr *Init = IList->getInit(Index);
      if (DesignatedInitExpr *DIE = dyn_cast<DesignatedInitExpr>(Init)) {
        // If we're not the subobject that matches up with the '{' for
        // the designator, we shouldn't be handling the
        // designator. Return immediately.
        if (!SubobjectIsDesignatorContext)
          return;
  
        // Handle this designated initializer. elementIndex will be
        // updated to be the next array element we'll initialize.
        if (CheckDesignatedInitializer(Entity, IList, DIE, 0,
                                       DeclType, nullptr, &elementIndex, Index,
                                       StructuredList, StructuredIndex, true,
                                       false)) {
          hadError = true;
          continue;
        }
  
        if (elementIndex.getBitWidth() > maxElements.getBitWidth())
          maxElements = maxElements.extend(elementIndex.getBitWidth());
        else if (elementIndex.getBitWidth() < maxElements.getBitWidth())
          elementIndex = elementIndex.extend(maxElements.getBitWidth());
        elementIndex.setIsUnsigned(maxElements.isUnsigned());
  
        // If the array is of incomplete type, keep track of the number of
        // elements in the initializer.
        if (!maxElementsKnown && elementIndex > maxElements)
          maxElements = elementIndex;
  
        continue;
      }
  
      // If we know the maximum number of elements, and we've already
      // hit it, stop consuming elements in the initializer list.
      if (maxElementsKnown && elementIndex == maxElements)
        break;
  
      InitializedEntity ElementEntity =
        InitializedEntity::InitializeElement(SemaRef.Context, StructuredIndex,
                                             Entity);
      // Check this element.
      CheckSubElementType(ElementEntity, IList, elementType, Index,
                          StructuredList, StructuredIndex);
      ++elementIndex;
  
      // If the array is of incomplete type, keep track of the number of
      // elements in the initializer.
      if (!maxElementsKnown && elementIndex > maxElements)
        maxElements = elementIndex;
    }
    if (!hadError && DeclType->isIncompleteArrayType() && !VerifyOnly) {
      // If this is an incomplete array type, the actual type needs to
      // be calculated here.
      llvm::APSInt Zero(maxElements.getBitWidth(), maxElements.isUnsigned());
      if (maxElements == Zero && !Entity.isVariableLengthArrayNew()) {
        // Sizing an array implicitly to zero is not allowed by ISO C,
        // but is supported by GNU.
        SemaRef.Diag(IList->getBeginLoc(), diag::ext_typecheck_zero_array_size);
      }
  
      DeclType = SemaRef.Context.getConstantArrayType(
          elementType, maxElements, nullptr, ArrayType::Normal, 0);
    }
    if (!hadError) {
      // If there are any members of the array that get value-initialized, check
      // that is possible. That happens if we know the bound and don't have
      // enough elements, or if we're performing an array new with an unknown
      // bound.
      if ((maxElementsKnown && elementIndex < maxElements) ||
          Entity.isVariableLengthArrayNew())
        CheckEmptyInitializable(
            InitializedEntity::InitializeElement(SemaRef.Context, 0, Entity),
            IList->getEndLoc());
    }
  }
  
  bool InitListChecker::CheckFlexibleArrayInit(const InitializedEntity &Entity,
                                               Expr *InitExpr,
                                               FieldDecl *Field,
                                               bool TopLevelObject) {
    // Handle GNU flexible array initializers.
    unsigned FlexArrayDiag;
    if (isa<InitListExpr>(InitExpr) &&
        cast<InitListExpr>(InitExpr)->getNumInits() == 0) {
      // Empty flexible array init always allowed as an extension
      FlexArrayDiag = diag::ext_flexible_array_init;
    } else if (SemaRef.getLangOpts().CPlusPlus) {
      // Disallow flexible array init in C++; it is not required for gcc
      // compatibility, and it needs work to IRGen correctly in general.
      FlexArrayDiag = diag::err_flexible_array_init;
    } else if (!TopLevelObject) {
      // Disallow flexible array init on non-top-level object
      FlexArrayDiag = diag::err_flexible_array_init;
    } else if (Entity.getKind() != InitializedEntity::EK_Variable) {
      // Disallow flexible array init on anything which is not a variable.
      FlexArrayDiag = diag::err_flexible_array_init;
    } else if (cast<VarDecl>(Entity.getDecl())->hasLocalStorage()) {
      // Disallow flexible array init on local variables.
      FlexArrayDiag = diag::err_flexible_array_init;
    } else {
      // Allow other cases.
      FlexArrayDiag = diag::ext_flexible_array_init;
    }
  
    if (!VerifyOnly) {
      SemaRef.Diag(InitExpr->getBeginLoc(), FlexArrayDiag)
          << InitExpr->getBeginLoc();
      SemaRef.Diag(Field->getLocation(), diag::note_flexible_array_member)
        << Field;
    }
  
    return FlexArrayDiag != diag::ext_flexible_array_init;
  }
  
  void InitListChecker::CheckStructUnionTypes(
      const InitializedEntity &Entity, InitListExpr *IList, QualType DeclType,
      CXXRecordDecl::base_class_range Bases, RecordDecl::field_iterator Field,
      bool SubobjectIsDesignatorContext, unsigned &Index,
      InitListExpr *StructuredList, unsigned &StructuredIndex,
      bool TopLevelObject) {
    RecordDecl *structDecl = DeclType->castAs<RecordType>()->getDecl();
  
    // If the record is invalid, some of it's members are invalid. To avoid
    // confusion, we forgo checking the intializer for the entire record.
    if (structDecl->isInvalidDecl()) {
      // Assume it was supposed to consume a single initializer.
      ++Index;
      hadError = true;
      return;
    }
  
    if (DeclType->isUnionType() && IList->getNumInits() == 0) {
      RecordDecl *RD = DeclType->castAs<RecordType>()->getDecl();
  
      if (!VerifyOnly)
        for (FieldDecl *FD : RD->fields()) {
          QualType ET = SemaRef.Context.getBaseElementType(FD->getType());
          if (checkDestructorReference(ET, IList->getEndLoc(), SemaRef)) {
            hadError = true;
            return;
          }
        }
  
      // If there's a default initializer, use it.
      if (isa<CXXRecordDecl>(RD) &&
          cast<CXXRecordDecl>(RD)->hasInClassInitializer()) {
        if (!StructuredList)
          return;
        for (RecordDecl::field_iterator FieldEnd = RD->field_end();
             Field != FieldEnd; ++Field) {
          if (Field->hasInClassInitializer()) {
            StructuredList->setInitializedFieldInUnion(*Field);
            // FIXME: Actually build a CXXDefaultInitExpr?
            return;
          }
        }
      }
  
      // Value-initialize the first member of the union that isn't an unnamed
      // bitfield.
      for (RecordDecl::field_iterator FieldEnd = RD->field_end();
           Field != FieldEnd; ++Field) {
        if (!Field->isUnnamedBitfield()) {
          CheckEmptyInitializable(
              InitializedEntity::InitializeMember(*Field, &Entity),
              IList->getEndLoc());
          if (StructuredList)
            StructuredList->setInitializedFieldInUnion(*Field);
          break;
        }
      }
      return;
    }
  
    bool InitializedSomething = false;
  
    // If we have any base classes, they are initialized prior to the fields.
    for (auto &Base : Bases) {
      Expr *Init = Index < IList->getNumInits() ? IList->getInit(Index) : nullptr;
  
      // Designated inits always initialize fields, so if we see one, all
      // remaining base classes have no explicit initializer.
      if (Init && isa<DesignatedInitExpr>(Init))
        Init = nullptr;
  
      SourceLocation InitLoc = Init ? Init->getBeginLoc() : IList->getEndLoc();
      InitializedEntity BaseEntity = InitializedEntity::InitializeBase(
          SemaRef.Context, &Base, false, &Entity);
      if (Init) {
        CheckSubElementType(BaseEntity, IList, Base.getType(), Index,
                            StructuredList, StructuredIndex);
        InitializedSomething = true;
      } else {
        CheckEmptyInitializable(BaseEntity, InitLoc);
      }
  
      if (!VerifyOnly)
        if (checkDestructorReference(Base.getType(), InitLoc, SemaRef)) {
          hadError = true;
          return;
        }
    }
  
    // If structDecl is a forward declaration, this loop won't do
    // anything except look at designated initializers; That's okay,
    // because an error should get printed out elsewhere. It might be
    // worthwhile to skip over the rest of the initializer, though.
    RecordDecl *RD = DeclType->castAs<RecordType>()->getDecl();
    RecordDecl::field_iterator FieldEnd = RD->field_end();
    bool CheckForMissingFields =
      !IList->isIdiomaticZeroInitializer(SemaRef.getLangOpts());
    bool HasDesignatedInit = false;
  
    while (Index < IList->getNumInits()) {
      Expr *Init = IList->getInit(Index);
      SourceLocation InitLoc = Init->getBeginLoc();
  
      if (DesignatedInitExpr *DIE = dyn_cast<DesignatedInitExpr>(Init)) {
        // If we're not the subobject that matches up with the '{' for
        // the designator, we shouldn't be handling the
        // designator. Return immediately.
        if (!SubobjectIsDesignatorContext)
          return;
  
        HasDesignatedInit = true;
  
        // Handle this designated initializer. Field will be updated to
        // the next field that we'll be initializing.
        if (CheckDesignatedInitializer(Entity, IList, DIE, 0,
                                       DeclType, &Field, nullptr, Index,
                                       StructuredList, StructuredIndex,
                                       true, TopLevelObject))
          hadError = true;
        else if (!VerifyOnly) {
          // Find the field named by the designated initializer.
          RecordDecl::field_iterator F = RD->field_begin();
          while (std::next(F) != Field)
            ++F;
          QualType ET = SemaRef.Context.getBaseElementType(F->getType());
          if (checkDestructorReference(ET, InitLoc, SemaRef)) {
            hadError = true;
            return;
          }
        }
  
        InitializedSomething = true;
  
        // Disable check for missing fields when designators are used.
        // This matches gcc behaviour.
        CheckForMissingFields = false;
        continue;
      }
  
      if (Field == FieldEnd) {
        // We've run out of fields. We're done.
        break;
      }
  
      // We've already initialized a member of a union. We're done.
      if (InitializedSomething && DeclType->isUnionType())
        break;
  
      // If we've hit the flexible array member at the end, we're done.
      if (Field->getType()->isIncompleteArrayType())
        break;
  
      if (Field->isUnnamedBitfield()) {
        // Don't initialize unnamed bitfields, e.g. "int : 20;"
        ++Field;
        continue;
      }
  
      // Make sure we can use this declaration.
      bool InvalidUse;
      if (VerifyOnly)
        InvalidUse = !SemaRef.CanUseDecl(*Field, TreatUnavailableAsInvalid);
      else
        InvalidUse = SemaRef.DiagnoseUseOfDecl(
            *Field, IList->getInit(Index)->getBeginLoc());
      if (InvalidUse) {
        ++Index;
        ++Field;
        hadError = true;
        continue;
      }
  
      if (!VerifyOnly) {
        QualType ET = SemaRef.Context.getBaseElementType(Field->getType());
        if (checkDestructorReference(ET, InitLoc, SemaRef)) {
          hadError = true;
          return;
        }
      }
  
      InitializedEntity MemberEntity =
        InitializedEntity::InitializeMember(*Field, &Entity);
      CheckSubElementType(MemberEntity, IList, Field->getType(), Index,
                          StructuredList, StructuredIndex);
      InitializedSomething = true;
  
      if (DeclType->isUnionType() && StructuredList) {
        // Initialize the first field within the union.
        StructuredList->setInitializedFieldInUnion(*Field);
      }
  
      ++Field;
    }
  
    // Emit warnings for missing struct field initializers.
    if (!VerifyOnly && InitializedSomething && CheckForMissingFields &&
        Field != FieldEnd && !Field->getType()->isIncompleteArrayType() &&
        !DeclType->isUnionType()) {
      // It is possible we have one or more unnamed bitfields remaining.
      // Find first (if any) named field and emit warning.
      for (RecordDecl::field_iterator it = Field, end = RD->field_end();
           it != end; ++it) {
        if (!it->isUnnamedBitfield() && !it->hasInClassInitializer()) {
          SemaRef.Diag(IList->getSourceRange().getEnd(),
                       diag::warn_missing_field_initializers) << *it;
          break;
        }
      }
    }
  
    // Check that any remaining fields can be value-initialized if we're not
    // building a structured list. (If we are, we'll check this later.)
    if (!StructuredList && Field != FieldEnd && !DeclType->isUnionType() &&
        !Field->getType()->isIncompleteArrayType()) {
      for (; Field != FieldEnd && !hadError; ++Field) {
        if (!Field->isUnnamedBitfield() && !Field->hasInClassInitializer())
          CheckEmptyInitializable(
              InitializedEntity::InitializeMember(*Field, &Entity),
              IList->getEndLoc());
      }
    }
  
    // Check that the types of the remaining fields have accessible destructors.
    if (!VerifyOnly) {
      // If the initializer expression has a designated initializer, check the
      // elements for which a designated initializer is not provided too.
      RecordDecl::field_iterator I = HasDesignatedInit ? RD->field_begin()
                                                       : Field;
      for (RecordDecl::field_iterator E = RD->field_end(); I != E; ++I) {
        QualType ET = SemaRef.Context.getBaseElementType(I->getType());
        if (checkDestructorReference(ET, IList->getEndLoc(), SemaRef)) {
          hadError = true;
          return;
        }
      }
    }
  
    if (Field == FieldEnd || !Field->getType()->isIncompleteArrayType() ||
        Index >= IList->getNumInits())
      return;
  
    if (CheckFlexibleArrayInit(Entity, IList->getInit(Index), *Field,
                               TopLevelObject)) {
      hadError = true;
      ++Index;
      return;
    }
  
    InitializedEntity MemberEntity =
      InitializedEntity::InitializeMember(*Field, &Entity);
  
    if (isa<InitListExpr>(IList->getInit(Index)))
      CheckSubElementType(MemberEntity, IList, Field->getType(), Index,
                          StructuredList, StructuredIndex);
    else
      CheckImplicitInitList(MemberEntity, IList, Field->getType(), Index,
                            StructuredList, StructuredIndex);
  }
  
  /// Expand a field designator that refers to a member of an
  /// anonymous struct or union into a series of field designators that
  /// refers to the field within the appropriate subobject.
  ///
  static void ExpandAnonymousFieldDesignator(Sema &SemaRef,
                                             DesignatedInitExpr *DIE,
                                             unsigned DesigIdx,
                                             IndirectFieldDecl *IndirectField) {
    typedef DesignatedInitExpr::Designator Designator;
  
    // Build the replacement designators.
    SmallVector<Designator, 4> Replacements;
    for (IndirectFieldDecl::chain_iterator PI = IndirectField->chain_begin(),
         PE = IndirectField->chain_end(); PI != PE; ++PI) {
      if (PI + 1 == PE)
        Replacements.push_back(Designator((IdentifierInfo *)nullptr,
                                      DIE->getDesignator(DesigIdx)->getDotLoc(),
                                  DIE->getDesignator(DesigIdx)->getFieldLoc()));
      else
        Replacements.push_back(Designator((IdentifierInfo *)nullptr,
                                          SourceLocation(), SourceLocation()));
      assert(isa<FieldDecl>(*PI));
      Replacements.back().setField(cast<FieldDecl>(*PI));
    }
  
    // Expand the current designator into the set of replacement
    // designators, so we have a full subobject path down to where the
    // member of the anonymous struct/union is actually stored.
    DIE->ExpandDesignator(SemaRef.Context, DesigIdx, &Replacements[0],
                          &Replacements[0] + Replacements.size());
  }
  
  static DesignatedInitExpr *CloneDesignatedInitExpr(Sema &SemaRef,
                                                     DesignatedInitExpr *DIE) {
    unsigned NumIndexExprs = DIE->getNumSubExprs() - 1;
    SmallVector<Expr*, 4> IndexExprs(NumIndexExprs);
    for (unsigned I = 0; I < NumIndexExprs; ++I)
      IndexExprs[I] = DIE->getSubExpr(I + 1);
    return DesignatedInitExpr::Create(SemaRef.Context, DIE->designators(),
                                      IndexExprs,
                                      DIE->getEqualOrColonLoc(),
                                      DIE->usesGNUSyntax(), DIE->getInit());
  }
  
  namespace {
  
  // Callback to only accept typo corrections that are for field members of
  // the given struct or union.
  class FieldInitializerValidatorCCC final : public CorrectionCandidateCallback {
   public:
    explicit FieldInitializerValidatorCCC(RecordDecl *RD)
        : Record(RD) {}
  
    bool ValidateCandidate(const TypoCorrection &candidate) override {
      FieldDecl *FD = candidate.getCorrectionDeclAs<FieldDecl>();
      return FD && FD->getDeclContext()->getRedeclContext()->Equals(Record);
    }
  
    std::unique_ptr<CorrectionCandidateCallback> clone() override {
      return std::make_unique<FieldInitializerValidatorCCC>(*this);
    }
  
   private:
    RecordDecl *Record;
  };
  
  } // end anonymous namespace
  
  /// Check the well-formedness of a C99 designated initializer.
  ///
  /// Determines whether the designated initializer @p DIE, which
  /// resides at the given @p Index within the initializer list @p
  /// IList, is well-formed for a current object of type @p DeclType
  /// (C99 6.7.8). The actual subobject that this designator refers to
  /// within the current subobject is returned in either
  /// @p NextField or @p NextElementIndex (whichever is appropriate).
  ///
  /// @param IList  The initializer list in which this designated
  /// initializer occurs.
  ///
  /// @param DIE The designated initializer expression.
  ///
  /// @param DesigIdx  The index of the current designator.
  ///
  /// @param CurrentObjectType The type of the "current object" (C99 6.7.8p17),
  /// into which the designation in @p DIE should refer.
  ///
  /// @param NextField  If non-NULL and the first designator in @p DIE is
  /// a field, this will be set to the field declaration corresponding
  /// to the field named by the designator. On input, this is expected to be
  /// the next field that would be initialized in the absence of designation,
  /// if the complete object being initialized is a struct.
  ///
  /// @param NextElementIndex  If non-NULL and the first designator in @p
  /// DIE is an array designator or GNU array-range designator, this
  /// will be set to the last index initialized by this designator.
  ///
  /// @param Index  Index into @p IList where the designated initializer
  /// @p DIE occurs.
  ///
  /// @param StructuredList  The initializer list expression that
  /// describes all of the subobject initializers in the order they'll
  /// actually be initialized.
  ///
  /// @returns true if there was an error, false otherwise.
  bool
  InitListChecker::CheckDesignatedInitializer(const InitializedEntity &Entity,
                                              InitListExpr *IList,
                                              DesignatedInitExpr *DIE,
                                              unsigned DesigIdx,
                                              QualType &CurrentObjectType,
                                            RecordDecl::field_iterator *NextField,
                                              llvm::APSInt *NextElementIndex,
                                              unsigned &Index,
                                              InitListExpr *StructuredList,
                                              unsigned &StructuredIndex,
                                              bool FinishSubobjectInit,
                                              bool TopLevelObject) {
    if (DesigIdx == DIE->size()) {
      // C++20 designated initialization can result in direct-list-initialization
      // of the designated subobject. This is the only way that we can end up
      // performing direct initialization as part of aggregate initialization, so
      // it needs special handling.
      if (DIE->isDirectInit()) {
        Expr *Init = DIE->getInit();
        assert(isa<InitListExpr>(Init) &&
               "designator result in direct non-list initialization?");
        InitializationKind Kind = InitializationKind::CreateDirectList(
            DIE->getBeginLoc(), Init->getBeginLoc(), Init->getEndLoc());
        InitializationSequence Seq(SemaRef, Entity, Kind, Init,
                                   /*TopLevelOfInitList*/ true);
        if (StructuredList) {
          ExprResult Result = VerifyOnly
                                  ? getDummyInit()
                                  : Seq.Perform(SemaRef, Entity, Kind, Init);
          UpdateStructuredListElement(StructuredList, StructuredIndex,
                                      Result.get());
        }
        ++Index;
        return !Seq;
      }
  
      // Check the actual initialization for the designated object type.
      bool prevHadError = hadError;
  
      // Temporarily remove the designator expression from the
      // initializer list that the child calls see, so that we don't try
      // to re-process the designator.
      unsigned OldIndex = Index;
      IList->setInit(OldIndex, DIE->getInit());
  
      CheckSubElementType(Entity, IList, CurrentObjectType, Index,
                          StructuredList, StructuredIndex);
  
      // Restore the designated initializer expression in the syntactic
      // form of the initializer list.
      if (IList->getInit(OldIndex) != DIE->getInit())
        DIE->setInit(IList->getInit(OldIndex));
      IList->setInit(OldIndex, DIE);
  
      return hadError && !prevHadError;
    }
  
    DesignatedInitExpr::Designator *D = DIE->getDesignator(DesigIdx);
    bool IsFirstDesignator = (DesigIdx == 0);
    if (IsFirstDesignator ? FullyStructuredList : StructuredList) {
      // Determine the structural initializer list that corresponds to the
      // current subobject.
      if (IsFirstDesignator)
        StructuredList = FullyStructuredList;
      else {
        Expr *ExistingInit = StructuredIndex < StructuredList->getNumInits() ?
            StructuredList->getInit(StructuredIndex) : nullptr;
        if (!ExistingInit && StructuredList->hasArrayFiller())
          ExistingInit = StructuredList->getArrayFiller();
  
        if (!ExistingInit)
          StructuredList = getStructuredSubobjectInit(
              IList, Index, CurrentObjectType, StructuredList, StructuredIndex,
              SourceRange(D->getBeginLoc(), DIE->getEndLoc()));
        else if (InitListExpr *Result = dyn_cast<InitListExpr>(ExistingInit))
          StructuredList = Result;
        else {
          // We are creating an initializer list that initializes the
          // subobjects of the current object, but there was already an
          // initialization that completely initialized the current
          // subobject, e.g., by a compound literal:
          //
          // struct X { int a, b; };
          // struct X xs[] = { [0] = (struct X) { 1, 2 }, [0].b = 3 };
          //
          // Here, xs[0].a == 1 and xs[0].b == 3, since the second,
          // designated initializer re-initializes only its current object
          // subobject [0].b.
          diagnoseInitOverride(ExistingInit,
                               SourceRange(D->getBeginLoc(), DIE->getEndLoc()),
                               /*FullyOverwritten=*/false);
  
          if (!VerifyOnly) {
            if (DesignatedInitUpdateExpr *E =
                    dyn_cast<DesignatedInitUpdateExpr>(ExistingInit))
              StructuredList = E->getUpdater();
            else {
              DesignatedInitUpdateExpr *DIUE = new (SemaRef.Context)
                  DesignatedInitUpdateExpr(SemaRef.Context, D->getBeginLoc(),
                                           ExistingInit, DIE->getEndLoc());
              StructuredList->updateInit(SemaRef.Context, StructuredIndex, DIUE);
              StructuredList = DIUE->getUpdater();
            }
          } else {
            // We don't need to track the structured representation of a
            // designated init update of an already-fully-initialized object in
            // verify-only mode. The only reason we would need the structure is
            // to determine where the uninitialized "holes" are, and in this
            // case, we know there aren't any and we can't introduce any.
            StructuredList = nullptr;
          }
        }
      }
    }
  
    if (D->isFieldDesignator()) {
      // C99 6.7.8p7:
      //
      //   If a designator has the form
      //
      //      . identifier
      //
      //   then the current object (defined below) shall have
      //   structure or union type and the identifier shall be the
      //   name of a member of that type.
      const RecordType *RT = CurrentObjectType->getAs<RecordType>();
      if (!RT) {
        SourceLocation Loc = D->getDotLoc();
        if (Loc.isInvalid())
          Loc = D->getFieldLoc();
        if (!VerifyOnly)
          SemaRef.Diag(Loc, diag::err_field_designator_non_aggr)
            << SemaRef.getLangOpts().CPlusPlus << CurrentObjectType;
        ++Index;
        return true;
      }
  
      FieldDecl *KnownField = D->getField();
      if (!KnownField) {
        IdentifierInfo *FieldName = D->getFieldName();
        DeclContext::lookup_result Lookup = RT->getDecl()->lookup(FieldName);
        for (NamedDecl *ND : Lookup) {
          if (auto *FD = dyn_cast<FieldDecl>(ND)) {
            KnownField = FD;
            break;
          }
          if (auto *IFD = dyn_cast<IndirectFieldDecl>(ND)) {
            // In verify mode, don't modify the original.
            if (VerifyOnly)
              DIE = CloneDesignatedInitExpr(SemaRef, DIE);
            ExpandAnonymousFieldDesignator(SemaRef, DIE, DesigIdx, IFD);
            D = DIE->getDesignator(DesigIdx);
            KnownField = cast<FieldDecl>(*IFD->chain_begin());
            break;
          }
        }
        if (!KnownField) {
          if (VerifyOnly) {
            ++Index;
            return true;  // No typo correction when just trying this out.
          }
  
          // Name lookup found something, but it wasn't a field.
          if (!Lookup.empty()) {
            SemaRef.Diag(D->getFieldLoc(), diag::err_field_designator_nonfield)
              << FieldName;
            SemaRef.Diag(Lookup.front()->getLocation(),
                         diag::note_field_designator_found);
            ++Index;
            return true;
          }
  
          // Name lookup didn't find anything.
          // Determine whether this was a typo for another field name.
          FieldInitializerValidatorCCC CCC(RT->getDecl());
          if (TypoCorrection Corrected = SemaRef.CorrectTypo(
                  DeclarationNameInfo(FieldName, D->getFieldLoc()),
                  Sema::LookupMemberName, /*Scope=*/nullptr, /*SS=*/nullptr, CCC,
                  Sema::CTK_ErrorRecovery, RT->getDecl())) {
            SemaRef.diagnoseTypo(
                Corrected,
                SemaRef.PDiag(diag::err_field_designator_unknown_suggest)
                  << FieldName << CurrentObjectType);
            KnownField = Corrected.getCorrectionDeclAs<FieldDecl>();
            hadError = true;
          } else {
            // Typo correction didn't find anything.
            SemaRef.Diag(D->getFieldLoc(), diag::err_field_designator_unknown)
              << FieldName << CurrentObjectType;
            ++Index;
            return true;
          }
        }
      }
  
      unsigned NumBases = 0;
      if (auto *CXXRD = dyn_cast<CXXRecordDecl>(RT->getDecl()))
        NumBases = CXXRD->getNumBases();
  
      unsigned FieldIndex = NumBases;
  
      for (auto *FI : RT->getDecl()->fields()) {
        if (FI->isUnnamedBitfield())
          continue;
        if (declaresSameEntity(KnownField, FI)) {
          KnownField = FI;
          break;
        }
        ++FieldIndex;
      }
  
      RecordDecl::field_iterator Field =
          RecordDecl::field_iterator(DeclContext::decl_iterator(KnownField));
  
      // All of the fields of a union are located at the same place in
      // the initializer list.
      if (RT->getDecl()->isUnion()) {
        FieldIndex = 0;
        if (StructuredList) {
          FieldDecl *CurrentField = StructuredList->getInitializedFieldInUnion();
          if (CurrentField && !declaresSameEntity(CurrentField, *Field)) {
            assert(StructuredList->getNumInits() == 1
                   && "A union should never have more than one initializer!");
  
            Expr *ExistingInit = StructuredList->getInit(0);
            if (ExistingInit) {
              // We're about to throw away an initializer, emit warning.
              diagnoseInitOverride(
                  ExistingInit, SourceRange(D->getBeginLoc(), DIE->getEndLoc()));
            }
  
            // remove existing initializer
            StructuredList->resizeInits(SemaRef.Context, 0);
            StructuredList->setInitializedFieldInUnion(nullptr);
          }
  
          StructuredList->setInitializedFieldInUnion(*Field);
        }
      }
  
      // Make sure we can use this declaration.
      bool InvalidUse;
      if (VerifyOnly)
        InvalidUse = !SemaRef.CanUseDecl(*Field, TreatUnavailableAsInvalid);
      else
        InvalidUse = SemaRef.DiagnoseUseOfDecl(*Field, D->getFieldLoc());
      if (InvalidUse) {
        ++Index;
        return true;
      }
  
      // C++20 [dcl.init.list]p3:
      //   The ordered identifiers in the designators of the designated-
      //   initializer-list shall form a subsequence of the ordered identifiers
      //   in the direct non-static data members of T.
      //
      // Note that this is not a condition on forming the aggregate
      // initialization, only on actually performing initialization,
      // so it is not checked in VerifyOnly mode.
      //
      // FIXME: This is the only reordering diagnostic we produce, and it only
      // catches cases where we have a top-level field designator that jumps
      // backwards. This is the only such case that is reachable in an
      // otherwise-valid C++20 program, so is the only case that's required for
      // conformance, but for consistency, we should diagnose all the other
      // cases where a designator takes us backwards too.
      if (IsFirstDesignator && !VerifyOnly && SemaRef.getLangOpts().CPlusPlus &&
          NextField &&
          (*NextField == RT->getDecl()->field_end() ||
           (*NextField)->getFieldIndex() > Field->getFieldIndex() + 1)) {
        // Find the field that we just initialized.
        FieldDecl *PrevField = nullptr;
        for (auto FI = RT->getDecl()->field_begin();
             FI != RT->getDecl()->field_end(); ++FI) {
          if (FI->isUnnamedBitfield())
            continue;
          if (*NextField != RT->getDecl()->field_end() &&
              declaresSameEntity(*FI, **NextField))
            break;
          PrevField = *FI;
        }
  
        if (PrevField &&
            PrevField->getFieldIndex() > KnownField->getFieldIndex()) {
          SemaRef.Diag(DIE->getBeginLoc(), diag::ext_designated_init_reordered)
              << KnownField << PrevField << DIE->getSourceRange();
  
          unsigned OldIndex = NumBases + PrevField->getFieldIndex();
          if (StructuredList && OldIndex <= StructuredList->getNumInits()) {
            if (Expr *PrevInit = StructuredList->getInit(OldIndex)) {
              SemaRef.Diag(PrevInit->getBeginLoc(),
                           diag::note_previous_field_init)
                  << PrevField << PrevInit->getSourceRange();
            }
          }
        }
      }
  
  
      // Update the designator with the field declaration.
      if (!VerifyOnly)
        D->setField(*Field);
  
      // Make sure that our non-designated initializer list has space
      // for a subobject corresponding to this field.
      if (StructuredList && FieldIndex >= StructuredList->getNumInits())
        StructuredList->resizeInits(SemaRef.Context, FieldIndex + 1);
  
      // This designator names a flexible array member.
      if (Field->getType()->isIncompleteArrayType()) {
        bool Invalid = false;
        if ((DesigIdx + 1) != DIE->size()) {
          // We can't designate an object within the flexible array
          // member (because GCC doesn't allow it).
          if (!VerifyOnly) {
            DesignatedInitExpr::Designator *NextD
              = DIE->getDesignator(DesigIdx + 1);
            SemaRef.Diag(NextD->getBeginLoc(),
                         diag::err_designator_into_flexible_array_member)
                << SourceRange(NextD->getBeginLoc(), DIE->getEndLoc());
            SemaRef.Diag(Field->getLocation(), diag::note_flexible_array_member)
              << *Field;
          }
          Invalid = true;
        }
  
        if (!hadError && !isa<InitListExpr>(DIE->getInit()) &&
            !isa<StringLiteral>(DIE->getInit())) {
          // The initializer is not an initializer list.
          if (!VerifyOnly) {
            SemaRef.Diag(DIE->getInit()->getBeginLoc(),
                         diag::err_flexible_array_init_needs_braces)
                << DIE->getInit()->getSourceRange();
            SemaRef.Diag(Field->getLocation(), diag::note_flexible_array_member)
              << *Field;
          }
          Invalid = true;
        }
  
        // Check GNU flexible array initializer.
        if (!Invalid && CheckFlexibleArrayInit(Entity, DIE->getInit(), *Field,
                                               TopLevelObject))
          Invalid = true;
  
        if (Invalid) {
          ++Index;
          return true;
        }
  
        // Initialize the array.
        bool prevHadError = hadError;
        unsigned newStructuredIndex = FieldIndex;
        unsigned OldIndex = Index;
        IList->setInit(Index, DIE->getInit());
  
        InitializedEntity MemberEntity =
          InitializedEntity::InitializeMember(*Field, &Entity);
        CheckSubElementType(MemberEntity, IList, Field->getType(), Index,
                            StructuredList, newStructuredIndex);
  
        IList->setInit(OldIndex, DIE);
        if (hadError && !prevHadError) {
          ++Field;
          ++FieldIndex;
          if (NextField)
            *NextField = Field;
          StructuredIndex = FieldIndex;
          return true;
        }
      } else {
        // Recurse to check later designated subobjects.
        QualType FieldType = Field->getType();
        unsigned newStructuredIndex = FieldIndex;
  
        InitializedEntity MemberEntity =
          InitializedEntity::InitializeMember(*Field, &Entity);
        if (CheckDesignatedInitializer(MemberEntity, IList, DIE, DesigIdx + 1,
                                       FieldType, nullptr, nullptr, Index,
                                       StructuredList, newStructuredIndex,
                                       FinishSubobjectInit, false))
          return true;
      }
  
      // Find the position of the next field to be initialized in this
      // subobject.
      ++Field;
      ++FieldIndex;
  
      // If this the first designator, our caller will continue checking
      // the rest of this struct/class/union subobject.
      if (IsFirstDesignator) {
        if (NextField)
          *NextField = Field;
        StructuredIndex = FieldIndex;
        return false;
      }
  
      if (!FinishSubobjectInit)
        return false;
  
      // We've already initialized something in the union; we're done.
      if (RT->getDecl()->isUnion())
        return hadError;
  
      // Check the remaining fields within this class/struct/union subobject.
      bool prevHadError = hadError;
  
      auto NoBases =
          CXXRecordDecl::base_class_range(CXXRecordDecl::base_class_iterator(),
                                          CXXRecordDecl::base_class_iterator());
      CheckStructUnionTypes(Entity, IList, CurrentObjectType, NoBases, Field,
                            false, Index, StructuredList, FieldIndex);
      return hadError && !prevHadError;
    }
  
    // C99 6.7.8p6:
    //
    //   If a designator has the form
    //
    //      [ constant-expression ]
    //
    //   then the current object (defined below) shall have array
    //   type and the expression shall be an integer constant
    //   expression. If the array is of unknown size, any
    //   nonnegative value is valid.
    //
    // Additionally, cope with the GNU extension that permits
    // designators of the form
    //
    //      [ constant-expression ... constant-expression ]
    const ArrayType *AT = SemaRef.Context.getAsArrayType(CurrentObjectType);
    if (!AT) {
      if (!VerifyOnly)
        SemaRef.Diag(D->getLBracketLoc(), diag::err_array_designator_non_array)
          << CurrentObjectType;
      ++Index;
      return true;
    }
  
    Expr *IndexExpr = nullptr;
    llvm::APSInt DesignatedStartIndex, DesignatedEndIndex;
    if (D->isArrayDesignator()) {
      IndexExpr = DIE->getArrayIndex(*D);
      DesignatedStartIndex = IndexExpr->EvaluateKnownConstInt(SemaRef.Context);
      DesignatedEndIndex = DesignatedStartIndex;
    } else {
      assert(D->isArrayRangeDesignator() && "Need array-range designator");
  
      DesignatedStartIndex =
        DIE->getArrayRangeStart(*D)->EvaluateKnownConstInt(SemaRef.Context);
      DesignatedEndIndex =
        DIE->getArrayRangeEnd(*D)->EvaluateKnownConstInt(SemaRef.Context);
      IndexExpr = DIE->getArrayRangeEnd(*D);
  
      // Codegen can't handle evaluating array range designators that have side
      // effects, because we replicate the AST value for each initialized element.
      // As such, set the sawArrayRangeDesignator() bit if we initialize multiple
      // elements with something that has a side effect, so codegen can emit an
      // "error unsupported" error instead of miscompiling the app.
      if (DesignatedStartIndex.getZExtValue()!=DesignatedEndIndex.getZExtValue()&&
          DIE->getInit()->HasSideEffects(SemaRef.Context) && !VerifyOnly)
        FullyStructuredList->sawArrayRangeDesignator();
    }
  
    if (isa<ConstantArrayType>(AT)) {
      llvm::APSInt MaxElements(cast<ConstantArrayType>(AT)->getSize(), false);
      DesignatedStartIndex
        = DesignatedStartIndex.extOrTrunc(MaxElements.getBitWidth());
      DesignatedStartIndex.setIsUnsigned(MaxElements.isUnsigned());
      DesignatedEndIndex
        = DesignatedEndIndex.extOrTrunc(MaxElements.getBitWidth());
      DesignatedEndIndex.setIsUnsigned(MaxElements.isUnsigned());
      if (DesignatedEndIndex >= MaxElements) {
        if (!VerifyOnly)
          SemaRef.Diag(IndexExpr->getBeginLoc(),
                       diag::err_array_designator_too_large)
              << DesignatedEndIndex.toString(10) << MaxElements.toString(10)
              << IndexExpr->getSourceRange();
        ++Index;
        return true;
      }
    } else {
      unsigned DesignatedIndexBitWidth =
        ConstantArrayType::getMaxSizeBits(SemaRef.Context);
      DesignatedStartIndex =
        DesignatedStartIndex.extOrTrunc(DesignatedIndexBitWidth);
      DesignatedEndIndex =
        DesignatedEndIndex.extOrTrunc(DesignatedIndexBitWidth);
      DesignatedStartIndex.setIsUnsigned(true);
      DesignatedEndIndex.setIsUnsigned(true);
    }
  
    bool IsStringLiteralInitUpdate =
        StructuredList && StructuredList->isStringLiteralInit();
    if (IsStringLiteralInitUpdate && VerifyOnly) {
      // We're just verifying an update to a string literal init. We don't need
      // to split the string up into individual characters to do that.
      StructuredList = nullptr;
    } else if (IsStringLiteralInitUpdate) {
      // We're modifying a string literal init; we have to decompose the string
      // so we can modify the individual characters.
      ASTContext &Context = SemaRef.Context;
      Expr *SubExpr = StructuredList->getInit(0)->IgnoreParens();
  
      // Compute the character type
      QualType CharTy = AT->getElementType();
  
      // Compute the type of the integer literals.
      QualType PromotedCharTy = CharTy;
      if (CharTy->isPromotableIntegerType())
        PromotedCharTy = Context.getPromotedIntegerType(CharTy);
      unsigned PromotedCharTyWidth = Context.getTypeSize(PromotedCharTy);
  
      if (StringLiteral *SL = dyn_cast<StringLiteral>(SubExpr)) {
        // Get the length of the string.
        uint64_t StrLen = SL->getLength();
        if (cast<ConstantArrayType>(AT)->getSize().ult(StrLen))
          StrLen = cast<ConstantArrayType>(AT)->getSize().getZExtValue();
        StructuredList->resizeInits(Context, StrLen);
  
        // Build a literal for each character in the string, and put them into
        // the init list.
        for (unsigned i = 0, e = StrLen; i != e; ++i) {
          llvm::APInt CodeUnit(PromotedCharTyWidth, SL->getCodeUnit(i));
          Expr *Init = new (Context) IntegerLiteral(
              Context, CodeUnit, PromotedCharTy, SubExpr->getExprLoc());
          if (CharTy != PromotedCharTy)
            Init = ImplicitCastExpr::Create(Context, CharTy, CK_IntegralCast,
                                            Init, nullptr, VK_RValue);
          StructuredList->updateInit(Context, i, Init);
        }
      } else {
        ObjCEncodeExpr *E = cast<ObjCEncodeExpr>(SubExpr);
        std::string Str;
        Context.getObjCEncodingForType(E->getEncodedType(), Str);
  
        // Get the length of the string.
        uint64_t StrLen = Str.size();
        if (cast<ConstantArrayType>(AT)->getSize().ult(StrLen))
          StrLen = cast<ConstantArrayType>(AT)->getSize().getZExtValue();
        StructuredList->resizeInits(Context, StrLen);
  
        // Build a literal for each character in the string, and put them into
        // the init list.
        for (unsigned i = 0, e = StrLen; i != e; ++i) {
          llvm::APInt CodeUnit(PromotedCharTyWidth, Str[i]);
          Expr *Init = new (Context) IntegerLiteral(
              Context, CodeUnit, PromotedCharTy, SubExpr->getExprLoc());
          if (CharTy != PromotedCharTy)
            Init = ImplicitCastExpr::Create(Context, CharTy, CK_IntegralCast,
                                            Init, nullptr, VK_RValue);
          StructuredList->updateInit(Context, i, Init);
        }
      }
    }
  
    // Make sure that our non-designated initializer list has space
    // for a subobject corresponding to this array element.
    if (StructuredList &&
        DesignatedEndIndex.getZExtValue() >= StructuredList->getNumInits())
      StructuredList->resizeInits(SemaRef.Context,
                                  DesignatedEndIndex.getZExtValue() + 1);
  
    // Repeatedly perform subobject initializations in the range
    // [DesignatedStartIndex, DesignatedEndIndex].
  
    // Move to the next designator
    unsigned ElementIndex = DesignatedStartIndex.getZExtValue();
    unsigned OldIndex = Index;
  
    InitializedEntity ElementEntity =
      InitializedEntity::InitializeElement(SemaRef.Context, 0, Entity);
  
    while (DesignatedStartIndex <= DesignatedEndIndex) {
      // Recurse to check later designated subobjects.
      QualType ElementType = AT->getElementType();
      Index = OldIndex;
  
      ElementEntity.setElementIndex(ElementIndex);
      if (CheckDesignatedInitializer(
              ElementEntity, IList, DIE, DesigIdx + 1, ElementType, nullptr,
              nullptr, Index, StructuredList, ElementIndex,
              FinishSubobjectInit && (DesignatedStartIndex == DesignatedEndIndex),
              false))
        return true;
  
      // Move to the next index in the array that we'll be initializing.
      ++DesignatedStartIndex;
      ElementIndex = DesignatedStartIndex.getZExtValue();
    }
  
    // If this the first designator, our caller will continue checking
    // the rest of this array subobject.
    if (IsFirstDesignator) {
      if (NextElementIndex)
        *NextElementIndex = DesignatedStartIndex;
      StructuredIndex = ElementIndex;
      return false;
    }
  
    if (!FinishSubobjectInit)
      return false;
  
    // Check the remaining elements within this array subobject.
    bool prevHadError = hadError;
    CheckArrayType(Entity, IList, CurrentObjectType, DesignatedStartIndex,
                   /*SubobjectIsDesignatorContext=*/false, Index,
                   StructuredList, ElementIndex);
    return hadError && !prevHadError;
  }
  
  // Get the structured initializer list for a subobject of type
  // @p CurrentObjectType.
  InitListExpr *
  InitListChecker::getStructuredSubobjectInit(InitListExpr *IList, unsigned Index,
                                              QualType CurrentObjectType,
                                              InitListExpr *StructuredList,
                                              unsigned StructuredIndex,
                                              SourceRange InitRange,
                                              bool IsFullyOverwritten) {
    if (!StructuredList)
      return nullptr;
  
    Expr *ExistingInit = nullptr;
    if (StructuredIndex < StructuredList->getNumInits())
      ExistingInit = StructuredList->getInit(StructuredIndex);
  
    if (InitListExpr *Result = dyn_cast_or_null<InitListExpr>(ExistingInit))
      // There might have already been initializers for subobjects of the current
      // object, but a subsequent initializer list will overwrite the entirety
      // of the current object. (See DR 253 and C99 6.7.8p21). e.g.,
      //
      // struct P { char x[6]; };
      // struct P l = { .x[2] = 'x', .x = { [0] = 'f' } };
      //
      // The first designated initializer is ignored, and l.x is just "f".
      if (!IsFullyOverwritten)
        return Result;
  
    if (ExistingInit) {
      // We are creating an initializer list that initializes the
      // subobjects of the current object, but there was already an
      // initialization that completely initialized the current
      // subobject:
      //
      // struct X { int a, b; };
      // struct X xs[] = { [0] = { 1, 2 }, [0].b = 3 };
      //
      // Here, xs[0].a == 1 and xs[0].b == 3, since the second,
      // designated initializer overwrites the [0].b initializer
      // from the prior initialization.
      //
      // When the existing initializer is an expression rather than an
      // initializer list, we cannot decompose and update it in this way.
      // For example:
      //
      // struct X xs[] = { [0] = (struct X) { 1, 2 }, [0].b = 3 };
      //
      // This case is handled by CheckDesignatedInitializer.
      diagnoseInitOverride(ExistingInit, InitRange);
    }
  
    unsigned ExpectedNumInits = 0;
    if (Index < IList->getNumInits()) {
      if (auto *Init = dyn_cast_or_null<InitListExpr>(IList->getInit(Index)))
        ExpectedNumInits = Init->getNumInits();
      else
        ExpectedNumInits = IList->getNumInits() - Index;
    }
  
    InitListExpr *Result =
        createInitListExpr(CurrentObjectType, InitRange, ExpectedNumInits);
  
    // Link this new initializer list into the structured initializer
    // lists.
    StructuredList->updateInit(SemaRef.Context, StructuredIndex, Result);
    return Result;
  }
  
  InitListExpr *
  InitListChecker::createInitListExpr(QualType CurrentObjectType,
                                      SourceRange InitRange,
                                      unsigned ExpectedNumInits) {
    InitListExpr *Result
      = new (SemaRef.Context) InitListExpr(SemaRef.Context,
                                           InitRange.getBegin(), None,
                                           InitRange.getEnd());
  
    QualType ResultType = CurrentObjectType;
    if (!ResultType->isArrayType())
      ResultType = ResultType.getNonLValueExprType(SemaRef.Context);
    Result->setType(ResultType);
  
    // Pre-allocate storage for the structured initializer list.
    unsigned NumElements = 0;
  
    if (const ArrayType *AType
        = SemaRef.Context.getAsArrayType(CurrentObjectType)) {
      if (const ConstantArrayType *CAType = dyn_cast<ConstantArrayType>(AType)) {
        NumElements = CAType->getSize().getZExtValue();
        // Simple heuristic so that we don't allocate a very large
        // initializer with many empty entries at the end.
        if (NumElements > ExpectedNumInits)
          NumElements = 0;
      }
    } else if (const VectorType *VType = CurrentObjectType->getAs<VectorType>()) {
      NumElements = VType->getNumElements();
    } else if (CurrentObjectType->isRecordType()) {
      NumElements = numStructUnionElements(CurrentObjectType);
    }
  
    Result->reserveInits(SemaRef.Context, NumElements);
  
    return Result;
  }
  
  /// Update the initializer at index @p StructuredIndex within the
  /// structured initializer list to the value @p expr.
  void InitListChecker::UpdateStructuredListElement(InitListExpr *StructuredList,
                                                    unsigned &StructuredIndex,
                                                    Expr *expr) {
    // No structured initializer list to update
    if (!StructuredList)
      return;
  
    if (Expr *PrevInit = StructuredList->updateInit(SemaRef.Context,
                                                    StructuredIndex, expr)) {
      // This initializer overwrites a previous initializer. Warn.
      diagnoseInitOverride(PrevInit, expr->getSourceRange());
    }
  
    ++StructuredIndex;
  }
  
  /// Determine whether we can perform aggregate initialization for the purposes
  /// of overload resolution.
  bool Sema::CanPerformAggregateInitializationForOverloadResolution(
      const InitializedEntity &Entity, InitListExpr *From) {
    QualType Type = Entity.getType();
    InitListChecker Check(*this, Entity, From, Type, /*VerifyOnly=*/true,
                          /*TreatUnavailableAsInvalid=*/false,
                          /*InOverloadResolution=*/true);
    return !Check.HadError();
  }
  
  /// Check that the given Index expression is a valid array designator
  /// value. This is essentially just a wrapper around
  /// VerifyIntegerConstantExpression that also checks for negative values
  /// and produces a reasonable diagnostic if there is a
  /// failure. Returns the index expression, possibly with an implicit cast
  /// added, on success.  If everything went okay, Value will receive the
  /// value of the constant expression.
  static ExprResult
  CheckArrayDesignatorExpr(Sema &S, Expr *Index, llvm::APSInt &Value) {
    SourceLocation Loc = Index->getBeginLoc();
  
    // Make sure this is an integer constant expression.
    ExprResult Result = S.VerifyIntegerConstantExpression(Index, &Value);
    if (Result.isInvalid())
      return Result;
  
    if (Value.isSigned() && Value.isNegative())
      return S.Diag(Loc, diag::err_array_designator_negative)
        << Value.toString(10) << Index->getSourceRange();
  
    Value.setIsUnsigned(true);
    return Result;
  }
  
  ExprResult Sema::ActOnDesignatedInitializer(Designation &Desig,
                                              SourceLocation EqualOrColonLoc,
                                              bool GNUSyntax,
                                              ExprResult Init) {
    typedef DesignatedInitExpr::Designator ASTDesignator;
  
    bool Invalid = false;
    SmallVector<ASTDesignator, 32> Designators;
    SmallVector<Expr *, 32> InitExpressions;
  
    // Build designators and check array designator expressions.
    for (unsigned Idx = 0; Idx < Desig.getNumDesignators(); ++Idx) {
      const Designator &D = Desig.getDesignator(Idx);
      switch (D.getKind()) {
      case Designator::FieldDesignator:
        Designators.push_back(ASTDesignator(D.getField(), D.getDotLoc(),
                                            D.getFieldLoc()));
        break;
  
      case Designator::ArrayDesignator: {
        Expr *Index = static_cast<Expr *>(D.getArrayIndex());
        llvm::APSInt IndexValue;
        if (!Index->isTypeDependent() && !Index->isValueDependent())
          Index = CheckArrayDesignatorExpr(*this, Index, IndexValue).get();
        if (!Index)
          Invalid = true;
        else {
          Designators.push_back(ASTDesignator(InitExpressions.size(),
                                              D.getLBracketLoc(),
                                              D.getRBracketLoc()));
          InitExpressions.push_back(Index);
        }
        break;
      }
  
      case Designator::ArrayRangeDesignator: {
        Expr *StartIndex = static_cast<Expr *>(D.getArrayRangeStart());
        Expr *EndIndex = static_cast<Expr *>(D.getArrayRangeEnd());
        llvm::APSInt StartValue;
        llvm::APSInt EndValue;
        bool StartDependent = StartIndex->isTypeDependent() ||
                              StartIndex->isValueDependent();
        bool EndDependent = EndIndex->isTypeDependent() ||
                            EndIndex->isValueDependent();
        if (!StartDependent)
          StartIndex =
              CheckArrayDesignatorExpr(*this, StartIndex, StartValue).get();
        if (!EndDependent)
          EndIndex = CheckArrayDesignatorExpr(*this, EndIndex, EndValue).get();
  
        if (!StartIndex || !EndIndex)
          Invalid = true;
        else {
          // Make sure we're comparing values with the same bit width.
          if (StartDependent || EndDependent) {
            // Nothing to compute.
          } else if (StartValue.getBitWidth() > EndValue.getBitWidth())
            EndValue = EndValue.extend(StartValue.getBitWidth());
          else if (StartValue.getBitWidth() < EndValue.getBitWidth())
            StartValue = StartValue.extend(EndValue.getBitWidth());
  
          if (!StartDependent && !EndDependent && EndValue < StartValue) {
            Diag(D.getEllipsisLoc(), diag::err_array_designator_empty_range)
              << StartValue.toString(10) << EndValue.toString(10)
              << StartIndex->getSourceRange() << EndIndex->getSourceRange();
            Invalid = true;
          } else {
            Designators.push_back(ASTDesignator(InitExpressions.size(),
                                                D.getLBracketLoc(),
                                                D.getEllipsisLoc(),
                                                D.getRBracketLoc()));
            InitExpressions.push_back(StartIndex);
            InitExpressions.push_back(EndIndex);
          }
        }
        break;
      }
      }
    }
  
    if (Invalid || Init.isInvalid())
      return ExprError();
  
    // Clear out the expressions within the designation.
    Desig.ClearExprs(*this);
  
    return DesignatedInitExpr::Create(Context, Designators, InitExpressions,
                                      EqualOrColonLoc, GNUSyntax,
                                      Init.getAs<Expr>());
  }
  
  //===----------------------------------------------------------------------===//
  // Initialization entity
  //===----------------------------------------------------------------------===//
  
  InitializedEntity::InitializedEntity(ASTContext &Context, unsigned Index,
                                       const InitializedEntity &Parent)
    : Parent(&Parent), Index(Index)
  {
    if (const ArrayType *AT = Context.getAsArrayType(Parent.getType())) {
      Kind = EK_ArrayElement;
      Type = AT->getElementType();
    } else if (const VectorType *VT = Parent.getType()->getAs<VectorType>()) {
      Kind = EK_VectorElement;
      Type = VT->getElementType();
    } else {
      const ComplexType *CT = Parent.getType()->getAs<ComplexType>();
      assert(CT && "Unexpected type");
      Kind = EK_ComplexElement;
      Type = CT->getElementType();
    }
  }
  
  InitializedEntity
  InitializedEntity::InitializeBase(ASTContext &Context,
                                    const CXXBaseSpecifier *Base,
                                    bool IsInheritedVirtualBase,
                                    const InitializedEntity *Parent) {
    InitializedEntity Result;
    Result.Kind = EK_Base;
    Result.Parent = Parent;
    Result.Base = reinterpret_cast<uintptr_t>(Base);
    if (IsInheritedVirtualBase)
      Result.Base |= 0x01;
  
    Result.Type = Base->getType();
    return Result;
  }
  
  DeclarationName InitializedEntity::getName() const {
    switch (getKind()) {
    case EK_Parameter:
    case EK_Parameter_CF_Audited: {
      ParmVarDecl *D = reinterpret_cast<ParmVarDecl*>(Parameter & ~0x1);
      return (D ? D->getDeclName() : DeclarationName());
    }
  
    case EK_Variable:
    case EK_Member:
    case EK_Binding:
      return Variable.VariableOrMember->getDeclName();
  
    case EK_LambdaCapture:
      return DeclarationName(Capture.VarID);
  
    case EK_Result:
    case EK_StmtExprResult:
    case EK_Exception:
    case EK_New:
    case EK_Temporary:
    case EK_Base:
    case EK_Delegating:
    case EK_ArrayElement:
    case EK_VectorElement:
    case EK_ComplexElement:
    case EK_BlockElement:
    case EK_LambdaToBlockConversionBlockElement:
    case EK_CompoundLiteralInit:
    case EK_RelatedResult:
      return DeclarationName();
    }
  
    llvm_unreachable("Invalid EntityKind!");
  }
  
  ValueDecl *InitializedEntity::getDecl() const {
    switch (getKind()) {
    case EK_Variable:
    case EK_Member:
    case EK_Binding:
      return Variable.VariableOrMember;
  
    case EK_Parameter:
    case EK_Parameter_CF_Audited:
      return reinterpret_cast<ParmVarDecl*>(Parameter & ~0x1);
  
    case EK_Result:
    case EK_StmtExprResult:
    case EK_Exception:
    case EK_New:
    case EK_Temporary:
    case EK_Base:
    case EK_Delegating:
    case EK_ArrayElement:
    case EK_VectorElement:
    case EK_ComplexElement:
    case EK_BlockElement:
    case EK_LambdaToBlockConversionBlockElement:
    case EK_LambdaCapture:
    case EK_CompoundLiteralInit:
    case EK_RelatedResult:
      return nullptr;
    }
  
    llvm_unreachable("Invalid EntityKind!");
  }
  
  bool InitializedEntity::allowsNRVO() const {
    switch (getKind()) {
    case EK_Result:
    case EK_Exception:
      return LocAndNRVO.NRVO;
  
    case EK_StmtExprResult:
    case EK_Variable:
    case EK_Parameter:
    case EK_Parameter_CF_Audited:
    case EK_Member:
    case EK_Binding:
    case EK_New:
    case EK_Temporary:
    case EK_CompoundLiteralInit:
    case EK_Base:
    case EK_Delegating:
    case EK_ArrayElement:
    case EK_VectorElement:
    case EK_ComplexElement:
    case EK_BlockElement:
    case EK_LambdaToBlockConversionBlockElement:
    case EK_LambdaCapture:
    case EK_RelatedResult:
      break;
    }
  
    return false;
  }
  
  unsigned InitializedEntity::dumpImpl(raw_ostream &OS) const {
    assert(getParent() != this);
    unsigned Depth = getParent() ? getParent()->dumpImpl(OS) : 0;
    for (unsigned I = 0; I != Depth; ++I)
      OS << "`-";
  
    switch (getKind()) {
    case EK_Variable: OS << "Variable"; break;
    case EK_Parameter: OS << "Parameter"; break;
    case EK_Parameter_CF_Audited: OS << "CF audited function Parameter";
      break;
    case EK_Result: OS << "Result"; break;
    case EK_StmtExprResult: OS << "StmtExprResult"; break;
    case EK_Exception: OS << "Exception"; break;
    case EK_Member: OS << "Member"; break;
    case EK_Binding: OS << "Binding"; break;
    case EK_New: OS << "New"; break;
    case EK_Temporary: OS << "Temporary"; break;
    case EK_CompoundLiteralInit: OS << "CompoundLiteral";break;
    case EK_RelatedResult: OS << "RelatedResult"; break;
    case EK_Base: OS << "Base"; break;
    case EK_Delegating: OS << "Delegating"; break;
    case EK_ArrayElement: OS << "ArrayElement " << Index; break;
    case EK_VectorElement: OS << "VectorElement " << Index; break;
    case EK_ComplexElement: OS << "ComplexElement " << Index; break;
    case EK_BlockElement: OS << "Block"; break;
    case EK_LambdaToBlockConversionBlockElement:
      OS << "Block (lambda)";
      break;
    case EK_LambdaCapture:
      OS << "LambdaCapture ";
      OS << DeclarationName(Capture.VarID);
      break;
    }
  
    if (auto *D = getDecl()) {
      OS << " ";
      D->printQualifiedName(OS);
    }
  
    OS << " '" << getType().getAsString() << "'\n";
  
    return Depth + 1;
  }
  
  LLVM_DUMP_METHOD void InitializedEntity::dump() const {
    dumpImpl(llvm::errs());
  }
  
  //===----------------------------------------------------------------------===//
  // Initialization sequence
  //===----------------------------------------------------------------------===//
  
  void InitializationSequence::Step::Destroy() {
    switch (Kind) {
    case SK_ResolveAddressOfOverloadedFunction:
    case SK_CastDerivedToBaseRValue:
    case SK_CastDerivedToBaseXValue:
    case SK_CastDerivedToBaseLValue:
    case SK_BindReference:
    case SK_BindReferenceToTemporary:
    case SK_FinalCopy:
    case SK_ExtraneousCopyToTemporary:
    case SK_UserConversion:
    case SK_QualificationConversionRValue:
    case SK_QualificationConversionXValue:
    case SK_QualificationConversionLValue:
    case SK_AtomicConversion:
    case SK_ListInitialization:
    case SK_UnwrapInitList:
    case SK_RewrapInitList:
    case SK_ConstructorInitialization:
    case SK_ConstructorInitializationFromList:
    case SK_ZeroInitialization:
    case SK_CAssignment:
    case SK_StringInit:
    case SK_ObjCObjectConversion:
    case SK_ArrayLoopIndex:
    case SK_ArrayLoopInit:
    case SK_ArrayInit:
    case SK_GNUArrayInit:
    case SK_ParenthesizedArrayInit:
    case SK_PassByIndirectCopyRestore:
    case SK_PassByIndirectRestore:
    case SK_ProduceObjCObject:
    case SK_StdInitializerList:
    case SK_StdInitializerListConstructorCall:
    case SK_OCLSamplerInit:
    case SK_OCLZeroOpaqueType:
      break;
  
    case SK_ConversionSequence:
    case SK_ConversionSequenceNoNarrowing:
      delete ICS;
    }
  }
  
  bool InitializationSequence::isDirectReferenceBinding() const {
    // There can be some lvalue adjustments after the SK_BindReference step.
    for (auto I = Steps.rbegin(); I != Steps.rend(); ++I) {
      if (I->Kind == SK_BindReference)
        return true;
      if (I->Kind == SK_BindReferenceToTemporary)
        return false;
    }
    return false;
  }
  
  bool InitializationSequence::isAmbiguous() const {
    if (!Failed())
      return false;
  
    switch (getFailureKind()) {
    case FK_TooManyInitsForReference:
    case FK_ParenthesizedListInitForReference:
    case FK_ArrayNeedsInitList:
    case FK_ArrayNeedsInitListOrStringLiteral:
    case FK_ArrayNeedsInitListOrWideStringLiteral:
    case FK_NarrowStringIntoWideCharArray:
    case FK_WideStringIntoCharArray:
    case FK_IncompatWideStringIntoWideChar:
    case FK_PlainStringIntoUTF8Char:
    case FK_UTF8StringIntoPlainChar:
    case FK_AddressOfOverloadFailed: // FIXME: Could do better
    case FK_NonConstLValueReferenceBindingToTemporary:
    case FK_NonConstLValueReferenceBindingToBitfield:
    case FK_NonConstLValueReferenceBindingToVectorElement:
    case FK_NonConstLValueReferenceBindingToMatrixElement:
    case FK_NonConstLValueReferenceBindingToUnrelated:
    case FK_RValueReferenceBindingToLValue:
    case FK_ReferenceAddrspaceMismatchTemporary:
    case FK_ReferenceInitDropsQualifiers:
    case FK_ReferenceInitFailed:
    case FK_ConversionFailed:
    case FK_ConversionFromPropertyFailed:
    case FK_TooManyInitsForScalar:
    case FK_ParenthesizedListInitForScalar:
    case FK_ReferenceBindingToInitList:
    case FK_InitListBadDestinationType:
    case FK_DefaultInitOfConst:
    case FK_Incomplete:
    case FK_ArrayTypeMismatch:
    case FK_NonConstantArrayInit:
    case FK_ListInitializationFailed:
    case FK_VariableLengthArrayHasInitializer:
    case FK_PlaceholderType:
    case FK_ExplicitConstructor:
    case FK_AddressOfUnaddressableFunction:
      return false;
  
    case FK_ReferenceInitOverloadFailed:
    case FK_UserConversionOverloadFailed:
    case FK_ConstructorOverloadFailed:
    case FK_ListConstructorOverloadFailed:
      return FailedOverloadResult == OR_Ambiguous;
    }
  
    llvm_unreachable("Invalid EntityKind!");
  }
  
  bool InitializationSequence::isConstructorInitialization() const {
    return !Steps.empty() && Steps.back().Kind == SK_ConstructorInitialization;
  }
  
  void
  InitializationSequence
  ::AddAddressOverloadResolutionStep(FunctionDecl *Function,
                                     DeclAccessPair Found,
                                     bool HadMultipleCandidates) {
    Step S;
    S.Kind = SK_ResolveAddressOfOverloadedFunction;
    S.Type = Function->getType();
    S.Function.HadMultipleCandidates = HadMultipleCandidates;
    S.Function.Function = Function;
    S.Function.FoundDecl = Found;
    Steps.push_back(S);
  }
  
  void InitializationSequence::AddDerivedToBaseCastStep(QualType BaseType,
                                                        ExprValueKind VK) {
    Step S;
    switch (VK) {
    case VK_RValue: S.Kind = SK_CastDerivedToBaseRValue; break;
    case VK_XValue: S.Kind = SK_CastDerivedToBaseXValue; break;
    case VK_LValue: S.Kind = SK_CastDerivedToBaseLValue; break;
    }
    S.Type = BaseType;
    Steps.push_back(S);
  }
  
  void InitializationSequence::AddReferenceBindingStep(QualType T,
                                                       bool BindingTemporary) {
    Step S;
    S.Kind = BindingTemporary? SK_BindReferenceToTemporary : SK_BindReference;
    S.Type = T;
    Steps.push_back(S);
  }
  
  void InitializationSequence::AddFinalCopy(QualType T) {
    Step S;
    S.Kind = SK_FinalCopy;
    S.Type = T;
    Steps.push_back(S);
  }
  
  void InitializationSequence::AddExtraneousCopyToTemporary(QualType T) {
    Step S;
    S.Kind = SK_ExtraneousCopyToTemporary;
    S.Type = T;
    Steps.push_back(S);
  }
  
  void
  InitializationSequence::AddUserConversionStep(FunctionDecl *Function,
                                                DeclAccessPair FoundDecl,
                                                QualType T,
                                                bool HadMultipleCandidates) {
    Step S;
    S.Kind = SK_UserConversion;
    S.Type = T;
    S.Function.HadMultipleCandidates = HadMultipleCandidates;
    S.Function.Function = Function;
    S.Function.FoundDecl = FoundDecl;
    Steps.push_back(S);
  }
  
  void InitializationSequence::AddQualificationConversionStep(QualType Ty,
                                                              ExprValueKind VK) {
    Step S;
    S.Kind = SK_QualificationConversionRValue; // work around a gcc warning
    switch (VK) {
    case VK_RValue:
      S.Kind = SK_QualificationConversionRValue;
      break;
    case VK_XValue:
      S.Kind = SK_QualificationConversionXValue;
      break;
    case VK_LValue:
      S.Kind = SK_QualificationConversionLValue;
      break;
    }
    S.Type = Ty;
    Steps.push_back(S);
  }
  
  void InitializationSequence::AddAtomicConversionStep(QualType Ty) {
    Step S;
    S.Kind = SK_AtomicConversion;
    S.Type = Ty;
    Steps.push_back(S);
  }
  
  void InitializationSequence::AddConversionSequenceStep(
      const ImplicitConversionSequence &ICS, QualType T,
      bool TopLevelOfInitList) {
    Step S;
    S.Kind = TopLevelOfInitList ? SK_ConversionSequenceNoNarrowing
                                : SK_ConversionSequence;
    S.Type = T;
    S.ICS = new ImplicitConversionSequence(ICS);
    Steps.push_back(S);
  }
  
  void InitializationSequence::AddListInitializationStep(QualType T) {
    Step S;
    S.Kind = SK_ListInitialization;
    S.Type = T;
    Steps.push_back(S);
  }
  
  void InitializationSequence::AddConstructorInitializationStep(
      DeclAccessPair FoundDecl, CXXConstructorDecl *Constructor, QualType T,
      bool HadMultipleCandidates, bool FromInitList, bool AsInitList) {
    Step S;
    S.Kind = FromInitList ? AsInitList ? SK_StdInitializerListConstructorCall
                                       : SK_ConstructorInitializationFromList
                          : SK_ConstructorInitialization;
    S.Type = T;
    S.Function.HadMultipleCandidates = HadMultipleCandidates;
    S.Function.Function = Constructor;
    S.Function.FoundDecl = FoundDecl;
    Steps.push_back(S);
  }
  
  void InitializationSequence::AddZeroInitializationStep(QualType T) {
    Step S;
    S.Kind = SK_ZeroInitialization;
    S.Type = T;
    Steps.push_back(S);
  }
  
  void InitializationSequence::AddCAssignmentStep(QualType T) {
    Step S;
    S.Kind = SK_CAssignment;
    S.Type = T;
    Steps.push_back(S);
  }
  
  void InitializationSequence::AddStringInitStep(QualType T) {
    Step S;
    S.Kind = SK_StringInit;
    S.Type = T;
    Steps.push_back(S);
  }
  
  void InitializationSequence::AddObjCObjectConversionStep(QualType T) {
    Step S;
    S.Kind = SK_ObjCObjectConversion;
    S.Type = T;
    Steps.push_back(S);
  }
  
  void InitializationSequence::AddArrayInitStep(QualType T, bool IsGNUExtension) {
    Step S;
    S.Kind = IsGNUExtension ? SK_GNUArrayInit : SK_ArrayInit;
    S.Type = T;
    Steps.push_back(S);
  }
  
  void InitializationSequence::AddArrayInitLoopStep(QualType T, QualType EltT) {
    Step S;
    S.Kind = SK_ArrayLoopIndex;
    S.Type = EltT;
    Steps.insert(Steps.begin(), S);
  
    S.Kind = SK_ArrayLoopInit;
    S.Type = T;
    Steps.push_back(S);
  }
  
  void InitializationSequence::AddParenthesizedArrayInitStep(QualType T) {
    Step S;
    S.Kind = SK_ParenthesizedArrayInit;
    S.Type = T;
    Steps.push_back(S);
  }
  
  void InitializationSequence::AddPassByIndirectCopyRestoreStep(QualType type,
                                                                bool shouldCopy) {
    Step s;
    s.Kind = (shouldCopy ? SK_PassByIndirectCopyRestore
                         : SK_PassByIndirectRestore);
    s.Type = type;
    Steps.push_back(s);
  }
  
  void InitializationSequence::AddProduceObjCObjectStep(QualType T) {
    Step S;
    S.Kind = SK_ProduceObjCObject;
    S.Type = T;
    Steps.push_back(S);
  }
  
  void InitializationSequence::AddStdInitializerListConstructionStep(QualType T) {
    Step S;
    S.Kind = SK_StdInitializerList;
    S.Type = T;
    Steps.push_back(S);
  }
  
  void InitializationSequence::AddOCLSamplerInitStep(QualType T) {
    Step S;
    S.Kind = SK_OCLSamplerInit;
    S.Type = T;
    Steps.push_back(S);
  }
  
  void InitializationSequence::AddOCLZeroOpaqueTypeStep(QualType T) {
    Step S;
    S.Kind = SK_OCLZeroOpaqueType;
    S.Type = T;
    Steps.push_back(S);
  }
  
  void InitializationSequence::RewrapReferenceInitList(QualType T,
                                                       InitListExpr *Syntactic) {
    assert(Syntactic->getNumInits() == 1 &&
           "Can only rewrap trivial init lists.");
    Step S;
    S.Kind = SK_UnwrapInitList;
    S.Type = Syntactic->getInit(0)->getType();
    Steps.insert(Steps.begin(), S);
  
    S.Kind = SK_RewrapInitList;
    S.Type = T;
    S.WrappingSyntacticList = Syntactic;
    Steps.push_back(S);
  }
  
  void InitializationSequence::SetOverloadFailure(FailureKind Failure,
                                                  OverloadingResult Result) {
    setSequenceKind(FailedSequence);
    this->Failure = Failure;
    this->FailedOverloadResult = Result;
  }
  
  //===----------------------------------------------------------------------===//
  // Attempt initialization
  //===----------------------------------------------------------------------===//
  
  /// Tries to add a zero initializer. Returns true if that worked.
  static bool
  maybeRecoverWithZeroInitialization(Sema &S, InitializationSequence &Sequence,
                                     const InitializedEntity &Entity) {
    if (Entity.getKind() != InitializedEntity::EK_Variable)
      return false;
  
    VarDecl *VD = cast<VarDecl>(Entity.getDecl());
    if (VD->getInit() || VD->getEndLoc().isMacroID())
      return false;
  
    QualType VariableTy = VD->getType().getCanonicalType();
    SourceLocation Loc = S.getLocForEndOfToken(VD->getEndLoc());
    std::string Init = S.getFixItZeroInitializerForType(VariableTy, Loc);
    if (!Init.empty()) {
      Sequence.AddZeroInitializationStep(Entity.getType());
      Sequence.SetZeroInitializationFixit(Init, Loc);
      return true;
    }
    return false;
  }
  
  static void MaybeProduceObjCObject(Sema &S,
                                     InitializationSequence &Sequence,
                                     const InitializedEntity &Entity) {
    if (!S.getLangOpts().ObjCAutoRefCount) return;
  
    /// When initializing a parameter, produce the value if it's marked
    /// __attribute__((ns_consumed)).
    if (Entity.isParameterKind()) {
      if (!Entity.isParameterConsumed())
        return;
  
      assert(Entity.getType()->isObjCRetainableType() &&
             "consuming an object of unretainable type?");
      Sequence.AddProduceObjCObjectStep(Entity.getType());
  
    /// When initializing a return value, if the return type is a
    /// retainable type, then returns need to immediately retain the
    /// object.  If an autorelease is required, it will be done at the
    /// last instant.
    } else if (Entity.getKind() == InitializedEntity::EK_Result ||
               Entity.getKind() == InitializedEntity::EK_StmtExprResult) {
      if (!Entity.getType()->isObjCRetainableType())
        return;
  
      Sequence.AddProduceObjCObjectStep(Entity.getType());
    }
  }
  
  static void TryListInitialization(Sema &S,
                                    const InitializedEntity &Entity,
                                    const InitializationKind &Kind,
                                    InitListExpr *InitList,
                                    InitializationSequence &Sequence,
                                    bool TreatUnavailableAsInvalid);
  
  /// When initializing from init list via constructor, handle
  /// initialization of an object of type std::initializer_list<T>.
  ///
  /// \return true if we have handled initialization of an object of type
  /// std::initializer_list<T>, false otherwise.
  static bool TryInitializerListConstruction(Sema &S,
                                             InitListExpr *List,
                                             QualType DestType,
                                             InitializationSequence &Sequence,
                                             bool TreatUnavailableAsInvalid) {
    QualType E;
    if (!S.isStdInitializerList(DestType, &E))
      return false;
  
    if (!S.isCompleteType(List->getExprLoc(), E)) {
      Sequence.setIncompleteTypeFailure(E);
      return true;
    }
  
    // Try initializing a temporary array from the init list.
    QualType ArrayType = S.Context.getConstantArrayType(
        E.withConst(),
        llvm::APInt(S.Context.getTypeSize(S.Context.getSizeType()),
                    List->getNumInits()),
        nullptr, clang::ArrayType::Normal, 0);
    InitializedEntity HiddenArray =
        InitializedEntity::InitializeTemporary(ArrayType);
    InitializationKind Kind = InitializationKind::CreateDirectList(
        List->getExprLoc(), List->getBeginLoc(), List->getEndLoc());
    TryListInitialization(S, HiddenArray, Kind, List, Sequence,
                          TreatUnavailableAsInvalid);
    if (Sequence)
      Sequence.AddStdInitializerListConstructionStep(DestType);
    return true;
  }
  
  /// Determine if the constructor has the signature of a copy or move
  /// constructor for the type T of the class in which it was found. That is,
  /// determine if its first parameter is of type T or reference to (possibly
  /// cv-qualified) T.
  static bool hasCopyOrMoveCtorParam(ASTContext &Ctx,
                                     const ConstructorInfo &Info) {
    if (Info.Constructor->getNumParams() == 0)
      return false;
  
    QualType ParmT =
        Info.Constructor->getParamDecl(0)->getType().getNonReferenceType();
    QualType ClassT =
        Ctx.getRecordType(cast<CXXRecordDecl>(Info.FoundDecl->getDeclContext()));
  
    return Ctx.hasSameUnqualifiedType(ParmT, ClassT);
  }
  
  static OverloadingResult
  ResolveConstructorOverload(Sema &S, SourceLocation DeclLoc,
                             MultiExprArg Args,
                             OverloadCandidateSet &CandidateSet,
                             QualType DestType,
                             DeclContext::lookup_result Ctors,
                             OverloadCandidateSet::iterator &Best,
                             bool CopyInitializing, bool AllowExplicit,
                             bool OnlyListConstructors, bool IsListInit,
                             bool SecondStepOfCopyInit = false) {
    CandidateSet.clear(OverloadCandidateSet::CSK_InitByConstructor);
    CandidateSet.setDestAS(DestType.getQualifiers().getAddressSpace());
  
    for (NamedDecl *D : Ctors) {
      auto Info = getConstructorInfo(D);
      if (!Info.Constructor || Info.Constructor->isInvalidDecl())
        continue;
  
      if (OnlyListConstructors && !S.isInitListConstructor(Info.Constructor))
        continue;
  
      // C++11 [over.best.ics]p4:
      //   ... and the constructor or user-defined conversion function is a
      //   candidate by
      //   - 13.3.1.3, when the argument is the temporary in the second step
      //     of a class copy-initialization, or
      //   - 13.3.1.4, 13.3.1.5, or 13.3.1.6 (in all cases), [not handled here]
      //   - the second phase of 13.3.1.7 when the initializer list has exactly
      //     one element that is itself an initializer list, and the target is
      //     the first parameter of a constructor of class X, and the conversion
      //     is to X or reference to (possibly cv-qualified X),
      //   user-defined conversion sequences are not considered.
      bool SuppressUserConversions =
          SecondStepOfCopyInit ||
          (IsListInit && Args.size() == 1 && isa<InitListExpr>(Args[0]) &&
           hasCopyOrMoveCtorParam(S.Context, Info));
  
      if (Info.ConstructorTmpl)
        S.AddTemplateOverloadCandidate(
            Info.ConstructorTmpl, Info.FoundDecl,
            /*ExplicitArgs*/ nullptr, Args, CandidateSet, SuppressUserConversions,
            /*PartialOverloading=*/false, AllowExplicit);
      else {
        // C++ [over.match.copy]p1:
        //   - When initializing a temporary to be bound to the first parameter
        //     of a constructor [for type T] that takes a reference to possibly
        //     cv-qualified T as its first argument, called with a single
        //     argument in the context of direct-initialization, explicit
        //     conversion functions are also considered.
        // FIXME: What if a constructor template instantiates to such a signature?
        bool AllowExplicitConv = AllowExplicit && !CopyInitializing &&
                                 Args.size() == 1 &&
                                 hasCopyOrMoveCtorParam(S.Context, Info);
        S.AddOverloadCandidate(Info.Constructor, Info.FoundDecl, Args,
                               CandidateSet, SuppressUserConversions,
                               /*PartialOverloading=*/false, AllowExplicit,
                               AllowExplicitConv);
      }
    }
  
    // FIXME: Work around a bug in C++17 guaranteed copy elision.
    //
    // When initializing an object of class type T by constructor
    // ([over.match.ctor]) or by list-initialization ([over.match.list])
    // from a single expression of class type U, conversion functions of
    // U that convert to the non-reference type cv T are candidates.
    // Explicit conversion functions are only candidates during
    // direct-initialization.
    //
    // Note: SecondStepOfCopyInit is only ever true in this case when
    // evaluating whether to produce a C++98 compatibility warning.
    if (S.getLangOpts().CPlusPlus17 && Args.size() == 1 &&
        !SecondStepOfCopyInit) {
      Expr *Initializer = Args[0];
      auto *SourceRD = Initializer->getType()->getAsCXXRecordDecl();
      if (SourceRD && S.isCompleteType(DeclLoc, Initializer->getType())) {
        const auto &Conversions = SourceRD->getVisibleConversionFunctions();
        for (auto I = Conversions.begin(), E = Conversions.end(); I != E; ++I) {
          NamedDecl *D = *I;
          CXXRecordDecl *ActingDC = cast<CXXRecordDecl>(D->getDeclContext());
          D = D->getUnderlyingDecl();
  
          FunctionTemplateDecl *ConvTemplate = dyn_cast<FunctionTemplateDecl>(D);
          CXXConversionDecl *Conv;
          if (ConvTemplate)
            Conv = cast<CXXConversionDecl>(ConvTemplate->getTemplatedDecl());
          else
            Conv = cast<CXXConversionDecl>(D);
  
          if (ConvTemplate)
            S.AddTemplateConversionCandidate(
                ConvTemplate, I.getPair(), ActingDC, Initializer, DestType,
                CandidateSet, AllowExplicit, AllowExplicit,
                /*AllowResultConversion*/ false);
          else
            S.AddConversionCandidate(Conv, I.getPair(), ActingDC, Initializer,
                                     DestType, CandidateSet, AllowExplicit,
                                     AllowExplicit,
                                     /*AllowResultConversion*/ false);
        }
      }
    }
  
    // Perform overload resolution and return the result.
    return CandidateSet.BestViableFunction(S, DeclLoc, Best);
  }
  
  /// Attempt initialization by constructor (C++ [dcl.init]), which
  /// enumerates the constructors of the initialized entity and performs overload
  /// resolution to select the best.
  /// \param DestType       The destination class type.
  /// \param DestArrayType  The destination type, which is either DestType or
  ///                       a (possibly multidimensional) array of DestType.
  /// \param IsListInit     Is this list-initialization?
  /// \param IsInitListCopy Is this non-list-initialization resulting from a
  ///                       list-initialization from {x} where x is the same
  ///                       type as the entity?
  static void TryConstructorInitialization(Sema &S,
                                           const InitializedEntity &Entity,
                                           const InitializationKind &Kind,
                                           MultiExprArg Args, QualType DestType,
                                           QualType DestArrayType,
                                           InitializationSequence &Sequence,
                                           bool IsListInit = false,
                                           bool IsInitListCopy = false) {
    assert(((!IsListInit && !IsInitListCopy) ||
            (Args.size() == 1 && isa<InitListExpr>(Args[0]))) &&
           "IsListInit/IsInitListCopy must come with a single initializer list "
           "argument.");
    InitListExpr *ILE =
        (IsListInit || IsInitListCopy) ? cast<InitListExpr>(Args[0]) : nullptr;
    MultiExprArg UnwrappedArgs =
        ILE ? MultiExprArg(ILE->getInits(), ILE->getNumInits()) : Args;
  
    // The type we're constructing needs to be complete.
    if (!S.isCompleteType(Kind.getLocation(), DestType)) {
      Sequence.setIncompleteTypeFailure(DestType);
      return;
    }
  
    // C++17 [dcl.init]p17:
    //     - If the initializer expression is a prvalue and the cv-unqualified
    //       version of the source type is the same class as the class of the
    //       destination, the initializer expression is used to initialize the
    //       destination object.
    // Per DR (no number yet), this does not apply when initializing a base
    // class or delegating to another constructor from a mem-initializer.
    // ObjC++: Lambda captured by the block in the lambda to block conversion
    // should avoid copy elision.
    if (S.getLangOpts().CPlusPlus17 &&
        Entity.getKind() != InitializedEntity::EK_Base &&
        Entity.getKind() != InitializedEntity::EK_Delegating &&
        Entity.getKind() !=
            InitializedEntity::EK_LambdaToBlockConversionBlockElement &&
        UnwrappedArgs.size() == 1 && UnwrappedArgs[0]->isRValue() &&
        S.Context.hasSameUnqualifiedType(UnwrappedArgs[0]->getType(), DestType)) {
      // Convert qualifications if necessary.
      Sequence.AddQualificationConversionStep(DestType, VK_RValue);
      if (ILE)
        Sequence.RewrapReferenceInitList(DestType, ILE);
      return;
    }
  
    const RecordType *DestRecordType = DestType->getAs<RecordType>();
    assert(DestRecordType && "Constructor initialization requires record type");
    CXXRecordDecl *DestRecordDecl
      = cast<CXXRecordDecl>(DestRecordType->getDecl());
  
    // Build the candidate set directly in the initialization sequence
    // structure, so that it will persist if we fail.
    OverloadCandidateSet &CandidateSet = Sequence.getFailedCandidateSet();
  
    // Determine whether we are allowed to call explicit constructors or
    // explicit conversion operators.
    bool AllowExplicit = Kind.AllowExplicit() || IsListInit;
    bool CopyInitialization = Kind.getKind() == InitializationKind::IK_Copy;
  
    //   - Otherwise, if T is a class type, constructors are considered. The
    //     applicable constructors are enumerated, and the best one is chosen
    //     through overload resolution.
    DeclContext::lookup_result Ctors = S.LookupConstructors(DestRecordDecl);
  
    OverloadingResult Result = OR_No_Viable_Function;
    OverloadCandidateSet::iterator Best;
    bool AsInitializerList = false;
  
    // C++11 [over.match.list]p1, per DR1467:
    //   When objects of non-aggregate type T are list-initialized, such that
    //   8.5.4 [dcl.init.list] specifies that overload resolution is performed
    //   according to the rules in this section, overload resolution selects
    //   the constructor in two phases:
    //
    //   - Initially, the candidate functions are the initializer-list
    //     constructors of the class T and the argument list consists of the
    //     initializer list as a single argument.
    if (IsListInit) {
      AsInitializerList = true;
  
      // If the initializer list has no elements and T has a default constructor,
      // the first phase is omitted.
      if (!(UnwrappedArgs.empty() && S.LookupDefaultConstructor(DestRecordDecl)))
        Result = ResolveConstructorOverload(S, Kind.getLocation(), Args,
                                            CandidateSet, DestType, Ctors, Best,
                                            CopyInitialization, AllowExplicit,
                                            /*OnlyListConstructors=*/true,
                                            IsListInit);
    }
  
    // C++11 [over.match.list]p1:
    //   - If no viable initializer-list constructor is found, overload resolution
    //     is performed again, where the candidate functions are all the
    //     constructors of the class T and the argument list consists of the
    //     elements of the initializer list.
    if (Result == OR_No_Viable_Function) {
      AsInitializerList = false;
      Result = ResolveConstructorOverload(S, Kind.getLocation(), UnwrappedArgs,
                                          CandidateSet, DestType, Ctors, Best,
                                          CopyInitialization, AllowExplicit,
                                          /*OnlyListConstructors=*/false,
                                          IsListInit);
    }
    if (Result) {
      Sequence.SetOverloadFailure(IsListInit ?
                        InitializationSequence::FK_ListConstructorOverloadFailed :
                        InitializationSequence::FK_ConstructorOverloadFailed,
                                  Result);
      return;
    }
  
    bool HadMultipleCandidates = (CandidateSet.size() > 1);
  
    // In C++17, ResolveConstructorOverload can select a conversion function
    // instead of a constructor.
    if (auto *CD = dyn_cast<CXXConversionDecl>(Best->Function)) {
      // Add the user-defined conversion step that calls the conversion function.
      QualType ConvType = CD->getConversionType();
      assert(S.Context.hasSameUnqualifiedType(ConvType, DestType) &&
             "should not have selected this conversion function");
      Sequence.AddUserConversionStep(CD, Best->FoundDecl, ConvType,
                                     HadMultipleCandidates);
      if (!S.Context.hasSameType(ConvType, DestType))
        Sequence.AddQualificationConversionStep(DestType, VK_RValue);
      if (IsListInit)
        Sequence.RewrapReferenceInitList(Entity.getType(), ILE);
      return;
    }
  
    // C++11 [dcl.init]p6:
    //   If a program calls for the default initialization of an object
    //   of a const-qualified type T, T shall be a class type with a
    //   user-provided default constructor.
    // C++ core issue 253 proposal:
    //   If the implicit default constructor initializes all subobjects, no
    //   initializer should be required.
    // The 253 proposal is for example needed to process libstdc++ headers in 5.x.
    CXXConstructorDecl *CtorDecl = cast<CXXConstructorDecl>(Best->Function);
    if (Kind.getKind() == InitializationKind::IK_Default &&
        Entity.getType().isConstQualified()) {
      if (!CtorDecl->getParent()->allowConstDefaultInit()) {
        if (!maybeRecoverWithZeroInitialization(S, Sequence, Entity))
          Sequence.SetFailed(InitializationSequence::FK_DefaultInitOfConst);
        return;
      }
    }
  
    // C++11 [over.match.list]p1:
    //   In copy-list-initialization, if an explicit constructor is chosen, the
    //   initializer is ill-formed.
    if (IsListInit && !Kind.AllowExplicit() && CtorDecl->isExplicit()) {
      Sequence.SetFailed(InitializationSequence::FK_ExplicitConstructor);
      return;
    }
  
    // Add the constructor initialization step. Any cv-qualification conversion is
    // subsumed by the initialization.
    Sequence.AddConstructorInitializationStep(
        Best->FoundDecl, CtorDecl, DestArrayType, HadMultipleCandidates,
        IsListInit | IsInitListCopy, AsInitializerList);
  }
  
  static bool
  ResolveOverloadedFunctionForReferenceBinding(Sema &S,
                                               Expr *Initializer,
                                               QualType &SourceType,
                                               QualType &UnqualifiedSourceType,
                                               QualType UnqualifiedTargetType,
                                               InitializationSequence &Sequence) {
    if (S.Context.getCanonicalType(UnqualifiedSourceType) ==
          S.Context.OverloadTy) {
      DeclAccessPair Found;
      bool HadMultipleCandidates = false;
      if (FunctionDecl *Fn
          = S.ResolveAddressOfOverloadedFunction(Initializer,
                                                 UnqualifiedTargetType,
                                                 false, Found,
                                                 &HadMultipleCandidates)) {
        Sequence.AddAddressOverloadResolutionStep(Fn, Found,
                                                  HadMultipleCandidates);
        SourceType = Fn->getType();
        UnqualifiedSourceType = SourceType.getUnqualifiedType();
      } else if (!UnqualifiedTargetType->isRecordType()) {
        Sequence.SetFailed(InitializationSequence::FK_AddressOfOverloadFailed);
        return true;
      }
    }
    return false;
  }
  
  static void TryReferenceInitializationCore(Sema &S,
                                             const InitializedEntity &Entity,
                                             const InitializationKind &Kind,
                                             Expr *Initializer,
                                             QualType cv1T1, QualType T1,
                                             Qualifiers T1Quals,
                                             QualType cv2T2, QualType T2,
                                             Qualifiers T2Quals,
                                             InitializationSequence &Sequence);
  
  static void TryValueInitialization(Sema &S,
                                     const InitializedEntity &Entity,
                                     const InitializationKind &Kind,
                                     InitializationSequence &Sequence,
                                     InitListExpr *InitList = nullptr);
  
  /// Attempt list initialization of a reference.
  static void TryReferenceListInitialization(Sema &S,
                                             const InitializedEntity &Entity,
                                             const InitializationKind &Kind,
                                             InitListExpr *InitList,
                                             InitializationSequence &Sequence,
                                             bool TreatUnavailableAsInvalid) {
    // First, catch C++03 where this isn't possible.
    if (!S.getLangOpts().CPlusPlus11) {
      Sequence.SetFailed(InitializationSequence::FK_ReferenceBindingToInitList);
      return;
    }
    // Can't reference initialize a compound literal.
    if (Entity.getKind() == InitializedEntity::EK_CompoundLiteralInit) {
      Sequence.SetFailed(InitializationSequence::FK_ReferenceBindingToInitList);
      return;
    }
  
    QualType DestType = Entity.getType();
    QualType cv1T1 = DestType->castAs<ReferenceType>()->getPointeeType();
    Qualifiers T1Quals;
    QualType T1 = S.Context.getUnqualifiedArrayType(cv1T1, T1Quals);
  
    // Reference initialization via an initializer list works thus:
    // If the initializer list consists of a single element that is
    // reference-related to the referenced type, bind directly to that element
    // (possibly creating temporaries).
    // Otherwise, initialize a temporary with the initializer list and
    // bind to that.
    if (InitList->getNumInits() == 1) {
      Expr *Initializer = InitList->getInit(0);
      QualType cv2T2 = Initializer->getType();
      Qualifiers T2Quals;
      QualType T2 = S.Context.getUnqualifiedArrayType(cv2T2, T2Quals);
  
      // If this fails, creating a temporary wouldn't work either.
      if (ResolveOverloadedFunctionForReferenceBinding(S, Initializer, cv2T2, T2,
                                                       T1, Sequence))
        return;
  
      SourceLocation DeclLoc = Initializer->getBeginLoc();
      Sema::ReferenceCompareResult RefRelationship
        = S.CompareReferenceRelationship(DeclLoc, cv1T1, cv2T2);
      if (RefRelationship >= Sema::Ref_Related) {
        // Try to bind the reference here.
        TryReferenceInitializationCore(S, Entity, Kind, Initializer, cv1T1, T1,
                                       T1Quals, cv2T2, T2, T2Quals, Sequence);
        if (Sequence)
          Sequence.RewrapReferenceInitList(cv1T1, InitList);
        return;
      }
  
      // Update the initializer if we've resolved an overloaded function.
      if (Sequence.step_begin() != Sequence.step_end())
        Sequence.RewrapReferenceInitList(cv1T1, InitList);
    }
  
    // Not reference-related. Create a temporary and bind to that.
    InitializedEntity TempEntity = InitializedEntity::InitializeTemporary(cv1T1);
  
    TryListInitialization(S, TempEntity, Kind, InitList, Sequence,
                          TreatUnavailableAsInvalid);
    if (Sequence) {
      if (DestType->isRValueReferenceType() ||
          (T1Quals.hasConst() && !T1Quals.hasVolatile()))
        Sequence.AddReferenceBindingStep(cv1T1, /*BindingTemporary=*/true);
      else
        Sequence.SetFailed(
            InitializationSequence::FK_NonConstLValueReferenceBindingToTemporary);
    }
  }
  
  /// Attempt list initialization (C++0x [dcl.init.list])
  static void TryListInitialization(Sema &S,
                                    const InitializedEntity &Entity,
                                    const InitializationKind &Kind,
                                    InitListExpr *InitList,
                                    InitializationSequence &Sequence,
                                    bool TreatUnavailableAsInvalid) {
    QualType DestType = Entity.getType();
  
    // C++ doesn't allow scalar initialization with more than one argument.
    // But C99 complex numbers are scalars and it makes sense there.
    if (S.getLangOpts().CPlusPlus && DestType->isScalarType() &&
        !DestType->isAnyComplexType() && InitList->getNumInits() > 1) {
      Sequence.SetFailed(InitializationSequence::FK_TooManyInitsForScalar);
      return;
    }
    if (DestType->isReferenceType()) {
      TryReferenceListInitialization(S, Entity, Kind, InitList, Sequence,
                                     TreatUnavailableAsInvalid);
      return;
    }
  
    if (DestType->isRecordType() &&
        !S.isCompleteType(InitList->getBeginLoc(), DestType)) {
      Sequence.setIncompleteTypeFailure(DestType);
      return;
    }
  
    // C++11 [dcl.init.list]p3, per DR1467:
    // - If T is a class type and the initializer list has a single element of
    //   type cv U, where U is T or a class derived from T, the object is
    //   initialized from that element (by copy-initialization for
    //   copy-list-initialization, or by direct-initialization for
    //   direct-list-initialization).
    // - Otherwise, if T is a character array and the initializer list has a
    //   single element that is an appropriately-typed string literal
    //   (8.5.2 [dcl.init.string]), initialization is performed as described
    //   in that section.
    // - Otherwise, if T is an aggregate, [...] (continue below).
    if (S.getLangOpts().CPlusPlus11 && InitList->getNumInits() == 1) {
      if (DestType->isRecordType()) {
        QualType InitType = InitList->getInit(0)->getType();
        if (S.Context.hasSameUnqualifiedType(InitType, DestType) ||
            S.IsDerivedFrom(InitList->getBeginLoc(), InitType, DestType)) {
          Expr *InitListAsExpr = InitList;
          TryConstructorInitialization(S, Entity, Kind, InitListAsExpr, DestType,
                                       DestType, Sequence,
                                       /*InitListSyntax*/false,
                                       /*IsInitListCopy*/true);
          return;
        }
      }
      if (const ArrayType *DestAT = S.Context.getAsArrayType(DestType)) {
        Expr *SubInit[1] = {InitList->getInit(0)};
        if (!isa<VariableArrayType>(DestAT) &&
            IsStringInit(SubInit[0], DestAT, S.Context) == SIF_None) {
          InitializationKind SubKind =
              Kind.getKind() == InitializationKind::IK_DirectList
                  ? InitializationKind::CreateDirect(Kind.getLocation(),
                                                     InitList->getLBraceLoc(),
                                                     InitList->getRBraceLoc())
                  : Kind;
          Sequence.InitializeFrom(S, Entity, SubKind, SubInit,
                                  /*TopLevelOfInitList*/ true,
                                  TreatUnavailableAsInvalid);
  
          // TryStringLiteralInitialization() (in InitializeFrom()) will fail if
          // the element is not an appropriately-typed string literal, in which
          // case we should proceed as in C++11 (below).
          if (Sequence) {
            Sequence.RewrapReferenceInitList(Entity.getType(), InitList);
            return;
          }
        }
      }
    }
  
    // C++11 [dcl.init.list]p3:
    //   - If T is an aggregate, aggregate initialization is performed.
    if ((DestType->isRecordType() && !DestType->isAggregateType()) ||
        (S.getLangOpts().CPlusPlus11 &&
         S.isStdInitializerList(DestType, nullptr))) {
      if (S.getLangOpts().CPlusPlus11) {
        //   - Otherwise, if the initializer list has no elements and T is a
        //     class type with a default constructor, the object is
        //     value-initialized.
        if (InitList->getNumInits() == 0) {
          CXXRecordDecl *RD = DestType->getAsCXXRecordDecl();
          if (S.LookupDefaultConstructor(RD)) {
            TryValueInitialization(S, Entity, Kind, Sequence, InitList);
            return;
          }
        }
  
        //   - Otherwise, if T is a specialization of std::initializer_list<E>,
        //     an initializer_list object constructed [...]
        if (TryInitializerListConstruction(S, InitList, DestType, Sequence,
                                           TreatUnavailableAsInvalid))
          return;
  
        //   - Otherwise, if T is a class type, constructors are considered.
        Expr *InitListAsExpr = InitList;
        TryConstructorInitialization(S, Entity, Kind, InitListAsExpr, DestType,
                                     DestType, Sequence, /*InitListSyntax*/true);
      } else
        Sequence.SetFailed(InitializationSequence::FK_InitListBadDestinationType);
      return;
    }
  
    if (S.getLangOpts().CPlusPlus && !DestType->isAggregateType() &&
        InitList->getNumInits() == 1) {
      Expr *E = InitList->getInit(0);
  
      //   - Otherwise, if T is an enumeration with a fixed underlying type,
      //     the initializer-list has a single element v, and the initialization
      //     is direct-list-initialization, the object is initialized with the
      //     value T(v); if a narrowing conversion is required to convert v to
      //     the underlying type of T, the program is ill-formed.
      auto *ET = DestType->getAs<EnumType>();
      if (S.getLangOpts().CPlusPlus17 &&
          Kind.getKind() == InitializationKind::IK_DirectList &&
          ET && ET->getDecl()->isFixed() &&
          !S.Context.hasSameUnqualifiedType(E->getType(), DestType) &&
          (E->getType()->isIntegralOrEnumerationType() ||
           E->getType()->isFloatingType())) {
        // There are two ways that T(v) can work when T is an enumeration type.
        // If there is either an implicit conversion sequence from v to T or
        // a conversion function that can convert from v to T, then we use that.
        // Otherwise, if v is of integral, enumeration, or floating-point type,
        // it is converted to the enumeration type via its underlying type.
        // There is no overlap possible between these two cases (except when the
        // source value is already of the destination type), and the first
        // case is handled by the general case for single-element lists below.
        ImplicitConversionSequence ICS;
        ICS.setStandard();
        ICS.Standard.setAsIdentityConversion();
        if (!E->isRValue())
          ICS.Standard.First = ICK_Lvalue_To_Rvalue;
        // If E is of a floating-point type, then the conversion is ill-formed
        // due to narrowing, but go through the motions in order to produce the
        // right diagnostic.
        ICS.Standard.Second = E->getType()->isFloatingType()
                                  ? ICK_Floating_Integral
                                  : ICK_Integral_Conversion;
        ICS.Standard.setFromType(E->getType());
        ICS.Standard.setToType(0, E->getType());
        ICS.Standard.setToType(1, DestType);
        ICS.Standard.setToType(2, DestType);
        Sequence.AddConversionSequenceStep(ICS, ICS.Standard.getToType(2),
                                           /*TopLevelOfInitList*/true);
        Sequence.RewrapReferenceInitList(Entity.getType(), InitList);
        return;
      }
  
      //   - Otherwise, if the initializer list has a single element of type E
      //     [...references are handled above...], the object or reference is
      //     initialized from that element (by copy-initialization for
      //     copy-list-initialization, or by direct-initialization for
      //     direct-list-initialization); if a narrowing conversion is required
      //     to convert the element to T, the program is ill-formed.
      //
      // Per core-24034, this is direct-initialization if we were performing
      // direct-list-initialization and copy-initialization otherwise.
      // We can't use InitListChecker for this, because it always performs
      // copy-initialization. This only matters if we might use an 'explicit'
      // conversion operator, or for the special case conversion of nullptr_t to
      // bool, so we only need to handle those cases.
      //
      // FIXME: Why not do this in all cases?
      Expr *Init = InitList->getInit(0);
      if (Init->getType()->isRecordType() ||
          (Init->getType()->isNullPtrType() && DestType->isBooleanType())) {
        InitializationKind SubKind =
            Kind.getKind() == InitializationKind::IK_DirectList
                ? InitializationKind::CreateDirect(Kind.getLocation(),
                                                   InitList->getLBraceLoc(),
                                                   InitList->getRBraceLoc())
                : Kind;
        Expr *SubInit[1] = { Init };
        Sequence.InitializeFrom(S, Entity, SubKind, SubInit,
                                /*TopLevelOfInitList*/true,
                                TreatUnavailableAsInvalid);
        if (Sequence)
          Sequence.RewrapReferenceInitList(Entity.getType(), InitList);
        return;
      }
    }
  
    InitListChecker CheckInitList(S, Entity, InitList,
            DestType, /*VerifyOnly=*/true, TreatUnavailableAsInvalid);
    if (CheckInitList.HadError()) {
      Sequence.SetFailed(InitializationSequence::FK_ListInitializationFailed);
      return;
    }
  
    // Add the list initialization step with the built init list.
    Sequence.AddListInitializationStep(DestType);
  }
  
  /// Try a reference initialization that involves calling a conversion
  /// function.
  static OverloadingResult TryRefInitWithConversionFunction(
      Sema &S, const InitializedEntity &Entity, const InitializationKind &Kind,
      Expr *Initializer, bool AllowRValues, bool IsLValueRef,
      InitializationSequence &Sequence) {
    QualType DestType = Entity.getType();
    QualType cv1T1 = DestType->castAs<ReferenceType>()->getPointeeType();
    QualType T1 = cv1T1.getUnqualifiedType();
    QualType cv2T2 = Initializer->getType();
    QualType T2 = cv2T2.getUnqualifiedType();
  
    assert(!S.CompareReferenceRelationship(Initializer->getBeginLoc(), T1, T2) &&
           "Must have incompatible references when binding via conversion");
  
    // Build the candidate set directly in the initialization sequence
    // structure, so that it will persist if we fail.
    OverloadCandidateSet &CandidateSet = Sequence.getFailedCandidateSet();
    CandidateSet.clear(OverloadCandidateSet::CSK_InitByUserDefinedConversion);
  
    // Determine whether we are allowed to call explicit conversion operators.
    // Note that none of [over.match.copy], [over.match.conv], nor
    // [over.match.ref] permit an explicit constructor to be chosen when
    // initializing a reference, not even for direct-initialization.
    bool AllowExplicitCtors = false;
    bool AllowExplicitConvs = Kind.allowExplicitConversionFunctionsInRefBinding();
  
    const RecordType *T1RecordType = nullptr;
    if (AllowRValues && (T1RecordType = T1->getAs<RecordType>()) &&
        S.isCompleteType(Kind.getLocation(), T1)) {
      // The type we're converting to is a class type. Enumerate its constructors
      // to see if there is a suitable conversion.
      CXXRecordDecl *T1RecordDecl = cast<CXXRecordDecl>(T1RecordType->getDecl());
  
      for (NamedDecl *D : S.LookupConstructors(T1RecordDecl)) {
        auto Info = getConstructorInfo(D);
        if (!Info.Constructor)
          continue;
  
        if (!Info.Constructor->isInvalidDecl() &&
            Info.Constructor->isConvertingConstructor(/*AllowExplicit*/true)) {
          if (Info.ConstructorTmpl)
            S.AddTemplateOverloadCandidate(
                Info.ConstructorTmpl, Info.FoundDecl,
                /*ExplicitArgs*/ nullptr, Initializer, CandidateSet,
                /*SuppressUserConversions=*/true,
                /*PartialOverloading*/ false, AllowExplicitCtors);
          else
            S.AddOverloadCandidate(
                Info.Constructor, Info.FoundDecl, Initializer, CandidateSet,
                /*SuppressUserConversions=*/true,
                /*PartialOverloading*/ false, AllowExplicitCtors);
        }
      }
    }
    if (T1RecordType && T1RecordType->getDecl()->isInvalidDecl())
      return OR_No_Viable_Function;
  
    const RecordType *T2RecordType = nullptr;
    if ((T2RecordType = T2->getAs<RecordType>()) &&
        S.isCompleteType(Kind.getLocation(), T2)) {
      // The type we're converting from is a class type, enumerate its conversion
      // functions.
      CXXRecordDecl *T2RecordDecl = cast<CXXRecordDecl>(T2RecordType->getDecl());
  
      const auto &Conversions = T2RecordDecl->getVisibleConversionFunctions();
      for (auto I = Conversions.begin(), E = Conversions.end(); I != E; ++I) {
        NamedDecl *D = *I;
        CXXRecordDecl *ActingDC = cast<CXXRecordDecl>(D->getDeclContext());
        if (isa<UsingShadowDecl>(D))
          D = cast<UsingShadowDecl>(D)->getTargetDecl();
  
        FunctionTemplateDecl *ConvTemplate = dyn_cast<FunctionTemplateDecl>(D);
        CXXConversionDecl *Conv;
        if (ConvTemplate)
          Conv = cast<CXXConversionDecl>(ConvTemplate->getTemplatedDecl());
        else
          Conv = cast<CXXConversionDecl>(D);
  
        // If the conversion function doesn't return a reference type,
        // it can't be considered for this conversion unless we're allowed to
        // consider rvalues.
        // FIXME: Do we need to make sure that we only consider conversion
        // candidates with reference-compatible results? That might be needed to
        // break recursion.
        if ((AllowRValues ||
             Conv->getConversionType()->isLValueReferenceType())) {
          if (ConvTemplate)
            S.AddTemplateConversionCandidate(
                ConvTemplate, I.getPair(), ActingDC, Initializer, DestType,
                CandidateSet,
                /*AllowObjCConversionOnExplicit=*/false, AllowExplicitConvs);
          else
            S.AddConversionCandidate(
                Conv, I.getPair(), ActingDC, Initializer, DestType, CandidateSet,
                /*AllowObjCConversionOnExplicit=*/false, AllowExplicitConvs);
        }
      }
    }
    if (T2RecordType && T2RecordType->getDecl()->isInvalidDecl())
      return OR_No_Viable_Function;
  
    SourceLocation DeclLoc = Initializer->getBeginLoc();
  
    // Perform overload resolution. If it fails, return the failed result.
    OverloadCandidateSet::iterator Best;
    if (OverloadingResult Result
          = CandidateSet.BestViableFunction(S, DeclLoc, Best))
      return Result;
  
    FunctionDecl *Function = Best->Function;
    // This is the overload that will be used for this initialization step if we
    // use this initialization. Mark it as referenced.
    Function->setReferenced();
  
    // Compute the returned type and value kind of the conversion.
    QualType cv3T3;
    if (isa<CXXConversionDecl>(Function))
      cv3T3 = Function->getReturnType();
    else
      cv3T3 = T1;
  
    ExprValueKind VK = VK_RValue;
    if (cv3T3->isLValueReferenceType())
      VK = VK_LValue;
    else if (const auto *RRef = cv3T3->getAs<RValueReferenceType>())
      VK = RRef->getPointeeType()->isFunctionType() ? VK_LValue : VK_XValue;
    cv3T3 = cv3T3.getNonLValueExprType(S.Context);
  
    // Add the user-defined conversion step.
    bool HadMultipleCandidates = (CandidateSet.size() > 1);
    Sequence.AddUserConversionStep(Function, Best->FoundDecl, cv3T3,
                                   HadMultipleCandidates);
  
    // Determine whether we'll need to perform derived-to-base adjustments or
    // other conversions.
    Sema::ReferenceConversions RefConv;
    Sema::ReferenceCompareResult NewRefRelationship =
        S.CompareReferenceRelationship(DeclLoc, T1, cv3T3, &RefConv);
  
    // Add the final conversion sequence, if necessary.
    if (NewRefRelationship == Sema::Ref_Incompatible) {
      assert(!isa<CXXConstructorDecl>(Function) &&
             "should not have conversion after constructor");
  
      ImplicitConversionSequence ICS;
      ICS.setStandard();
      ICS.Standard = Best->FinalConversion;
      Sequence.AddConversionSequenceStep(ICS, ICS.Standard.getToType(2));
  
      // Every implicit conversion results in a prvalue, except for a glvalue
      // derived-to-base conversion, which we handle below.
      cv3T3 = ICS.Standard.getToType(2);
      VK = VK_RValue;
    }
  
    //   If the converted initializer is a prvalue, its type T4 is adjusted to
    //   type "cv1 T4" and the temporary materialization conversion is applied.
    //
    // We adjust the cv-qualifications to match the reference regardless of
    // whether we have a prvalue so that the AST records the change. In this
    // case, T4 is "cv3 T3".
    QualType cv1T4 = S.Context.getQualifiedType(cv3T3, cv1T1.getQualifiers());
    if (cv1T4.getQualifiers() != cv3T3.getQualifiers())
      Sequence.AddQualificationConversionStep(cv1T4, VK);
    Sequence.AddReferenceBindingStep(cv1T4, VK == VK_RValue);
    VK = IsLValueRef ? VK_LValue : VK_XValue;
  
    if (RefConv & Sema::ReferenceConversions::DerivedToBase)
      Sequence.AddDerivedToBaseCastStep(cv1T1, VK);
    else if (RefConv & Sema::ReferenceConversions::ObjC)
      Sequence.AddObjCObjectConversionStep(cv1T1);
    else if (RefConv & Sema::ReferenceConversions::Function)
      Sequence.AddQualificationConversionStep(cv1T1, VK);
    else if (RefConv & Sema::ReferenceConversions::Qualification) {
      if (!S.Context.hasSameType(cv1T4, cv1T1))
        Sequence.AddQualificationConversionStep(cv1T1, VK);
    }
  
    return OR_Success;
  }
  
  static void CheckCXX98CompatAccessibleCopy(Sema &S,
                                             const InitializedEntity &Entity,
                                             Expr *CurInitExpr);
  
  /// Attempt reference initialization (C++0x [dcl.init.ref])
  static void TryReferenceInitialization(Sema &S,
                                         const InitializedEntity &Entity,
                                         const InitializationKind &Kind,
                                         Expr *Initializer,
                                         InitializationSequence &Sequence) {
    QualType DestType = Entity.getType();
    QualType cv1T1 = DestType->castAs<ReferenceType>()->getPointeeType();
    Qualifiers T1Quals;
    QualType T1 = S.Context.getUnqualifiedArrayType(cv1T1, T1Quals);
    QualType cv2T2 = Initializer->getType();
    Qualifiers T2Quals;
    QualType T2 = S.Context.getUnqualifiedArrayType(cv2T2, T2Quals);
  
    // If the initializer is the address of an overloaded function, try
    // to resolve the overloaded function. If all goes well, T2 is the
    // type of the resulting function.
    if (ResolveOverloadedFunctionForReferenceBinding(S, Initializer, cv2T2, T2,
                                                     T1, Sequence))
      return;
  
    // Delegate everything else to a subfunction.
    TryReferenceInitializationCore(S, Entity, Kind, Initializer, cv1T1, T1,
                                   T1Quals, cv2T2, T2, T2Quals, Sequence);
  }
  
  /// Determine whether an expression is a non-referenceable glvalue (one to
  /// which a reference can never bind). Attempting to bind a reference to
  /// such a glvalue will always create a temporary.
  static bool isNonReferenceableGLValue(Expr *E) {
    return E->refersToBitField() || E->refersToVectorElement() ||
           E->refersToMatrixElement();
  }
  
  /// Reference initialization without resolving overloaded functions.
  static void TryReferenceInitializationCore(Sema &S,
                                             const InitializedEntity &Entity,
                                             const InitializationKind &Kind,
                                             Expr *Initializer,
                                             QualType cv1T1, QualType T1,
                                             Qualifiers T1Quals,
                                             QualType cv2T2, QualType T2,
                                             Qualifiers T2Quals,
                                             InitializationSequence &Sequence) {
    QualType DestType = Entity.getType();
    SourceLocation DeclLoc = Initializer->getBeginLoc();
  
    // Compute some basic properties of the types and the initializer.
    bool isLValueRef = DestType->isLValueReferenceType();
    bool isRValueRef = !isLValueRef;
    Expr::Classification InitCategory = Initializer->Classify(S.Context);
  
    Sema::ReferenceConversions RefConv;
    Sema::ReferenceCompareResult RefRelationship =
        S.CompareReferenceRelationship(DeclLoc, cv1T1, cv2T2, &RefConv);
  
    // C++0x [dcl.init.ref]p5:
    //   A reference to type "cv1 T1" is initialized by an expression of type
    //   "cv2 T2" as follows:
    //
    //     - If the reference is an lvalue reference and the initializer
    //       expression
    // Note the analogous bullet points for rvalue refs to functions. Because
    // there are no function rvalues in C++, rvalue refs to functions are treated
    // like lvalue refs.
    OverloadingResult ConvOvlResult = OR_Success;
    bool T1Function = T1->isFunctionType();
    if (isLValueRef || T1Function) {
      if (InitCategory.isLValue() && !isNonReferenceableGLValue(Initializer) &&
          (RefRelationship == Sema::Ref_Compatible ||
           (Kind.isCStyleOrFunctionalCast() &&
            RefRelationship == Sema::Ref_Related))) {
        //   - is an lvalue (but is not a bit-field), and "cv1 T1" is
        //     reference-compatible with "cv2 T2," or
        if (RefConv & (Sema::ReferenceConversions::DerivedToBase |
                       Sema::ReferenceConversions::ObjC)) {
          // If we're converting the pointee, add any qualifiers first;
          // these qualifiers must all be top-level, so just convert to "cv1 T2".
          if (RefConv & (Sema::ReferenceConversions::Qualification))
            Sequence.AddQualificationConversionStep(
                S.Context.getQualifiedType(T2, T1Quals),
                Initializer->getValueKind());
          if (RefConv & Sema::ReferenceConversions::DerivedToBase)
            Sequence.AddDerivedToBaseCastStep(cv1T1, VK_LValue);
          else
            Sequence.AddObjCObjectConversionStep(cv1T1);
        } else if (RefConv & (Sema::ReferenceConversions::Qualification |
                              Sema::ReferenceConversions::Function)) {
          // Perform a (possibly multi-level) qualification conversion.
          // FIXME: Should we use a different step kind for function conversions?
          Sequence.AddQualificationConversionStep(cv1T1,
                                                  Initializer->getValueKind());
        }
  
        // We only create a temporary here when binding a reference to a
        // bit-field or vector element. Those cases are't supposed to be
        // handled by this bullet, but the outcome is the same either way.
        Sequence.AddReferenceBindingStep(cv1T1, false);
        return;
      }
  
      //     - has a class type (i.e., T2 is a class type), where T1 is not
      //       reference-related to T2, and can be implicitly converted to an
      //       lvalue of type "cv3 T3," where "cv1 T1" is reference-compatible
      //       with "cv3 T3" (this conversion is selected by enumerating the
      //       applicable conversion functions (13.3.1.6) and choosing the best
      //       one through overload resolution (13.3)),
      // If we have an rvalue ref to function type here, the rhs must be
      // an rvalue. DR1287 removed the "implicitly" here.
      if (RefRelationship == Sema::Ref_Incompatible && T2->isRecordType() &&
          (isLValueRef || InitCategory.isRValue())) {
        ConvOvlResult = TryRefInitWithConversionFunction(
            S, Entity, Kind, Initializer, /*AllowRValues*/ isRValueRef,
            /*IsLValueRef*/ isLValueRef, Sequence);
        if (ConvOvlResult == OR_Success)
          return;
        if (ConvOvlResult != OR_No_Viable_Function)
          Sequence.SetOverloadFailure(
              InitializationSequence::FK_ReferenceInitOverloadFailed,
              ConvOvlResult);
      }
    }
  
    //     - Otherwise, the reference shall be an lvalue reference to a
    //       non-volatile const type (i.e., cv1 shall be const), or the reference
    //       shall be an rvalue reference.
    //       For address spaces, we interpret this to mean that an addr space
    //       of a reference "cv1 T1" is a superset of addr space of "cv2 T2".
    if (isLValueRef && !(T1Quals.hasConst() && !T1Quals.hasVolatile() &&
                         T1Quals.isAddressSpaceSupersetOf(T2Quals))) {
      if (S.Context.getCanonicalType(T2) == S.Context.OverloadTy)
        Sequence.SetFailed(InitializationSequence::FK_AddressOfOverloadFailed);
      else if (ConvOvlResult && !Sequence.getFailedCandidateSet().empty())
        Sequence.SetOverloadFailure(
                          InitializationSequence::FK_ReferenceInitOverloadFailed,
                                    ConvOvlResult);
      else if (!InitCategory.isLValue())
        Sequence.SetFailed(
            T1Quals.isAddressSpaceSupersetOf(T2Quals)
                ? InitializationSequence::
                      FK_NonConstLValueReferenceBindingToTemporary
                : InitializationSequence::FK_ReferenceInitDropsQualifiers);
      else {
        InitializationSequence::FailureKind FK;
        switch (RefRelationship) {
        case Sema::Ref_Compatible:
          if (Initializer->refersToBitField())
            FK = InitializationSequence::
                FK_NonConstLValueReferenceBindingToBitfield;
          else if (Initializer->refersToVectorElement())
            FK = InitializationSequence::
                FK_NonConstLValueReferenceBindingToVectorElement;
          else if (Initializer->refersToMatrixElement())
            FK = InitializationSequence::
                FK_NonConstLValueReferenceBindingToMatrixElement;
          else
            llvm_unreachable("unexpected kind of compatible initializer");
          break;
        case Sema::Ref_Related:
          FK = InitializationSequence::FK_ReferenceInitDropsQualifiers;
          break;
        case Sema::Ref_Incompatible:
          FK = InitializationSequence::
              FK_NonConstLValueReferenceBindingToUnrelated;
          break;
        }
        Sequence.SetFailed(FK);
      }
      return;
    }
  
    //    - If the initializer expression
    //      - is an
    // [<=14] xvalue (but not a bit-field), class prvalue, array prvalue, or
    // [1z]   rvalue (but not a bit-field) or
    //        function lvalue and "cv1 T1" is reference-compatible with "cv2 T2"
    //
    // Note: functions are handled above and below rather than here...
    if (!T1Function &&
        (RefRelationship == Sema::Ref_Compatible ||
         (Kind.isCStyleOrFunctionalCast() &&
          RefRelationship == Sema::Ref_Related)) &&
        ((InitCategory.isXValue() && !isNonReferenceableGLValue(Initializer)) ||
         (InitCategory.isPRValue() &&
          (S.getLangOpts().CPlusPlus17 || T2->isRecordType() ||
           T2->isArrayType())))) {
      ExprValueKind ValueKind = InitCategory.isXValue() ? VK_XValue : VK_RValue;
      if (InitCategory.isPRValue() && T2->isRecordType()) {
        // The corresponding bullet in C++03 [dcl.init.ref]p5 gives the
        // compiler the freedom to perform a copy here or bind to the
        // object, while C++0x requires that we bind directly to the
        // object. Hence, we always bind to the object without making an
        // extra copy. However, in C++03 requires that we check for the
        // presence of a suitable copy constructor:
        //
        //   The constructor that would be used to make the copy shall
        //   be callable whether or not the copy is actually done.
        if (!S.getLangOpts().CPlusPlus11 && !S.getLangOpts().MicrosoftExt)
          Sequence.AddExtraneousCopyToTemporary(cv2T2);
        else if (S.getLangOpts().CPlusPlus11)
          CheckCXX98CompatAccessibleCopy(S, Entity, Initializer);
      }
  
      // C++1z [dcl.init.ref]/5.2.1.2:
      //   If the converted initializer is a prvalue, its type T4 is adjusted
      //   to type "cv1 T4" and the temporary materialization conversion is
      //   applied.
      // Postpone address space conversions to after the temporary materialization
      // conversion to allow creating temporaries in the alloca address space.
      auto T1QualsIgnoreAS = T1Quals;
      auto T2QualsIgnoreAS = T2Quals;
      if (T1Quals.getAddressSpace() != T2Quals.getAddressSpace()) {
        T1QualsIgnoreAS.removeAddressSpace();
        T2QualsIgnoreAS.removeAddressSpace();
      }
      QualType cv1T4 = S.Context.getQualifiedType(cv2T2, T1QualsIgnoreAS);
      if (T1QualsIgnoreAS != T2QualsIgnoreAS)
        Sequence.AddQualificationConversionStep(cv1T4, ValueKind);
      Sequence.AddReferenceBindingStep(cv1T4, ValueKind == VK_RValue);
      ValueKind = isLValueRef ? VK_LValue : VK_XValue;
      // Add addr space conversion if required.
      if (T1Quals.getAddressSpace() != T2Quals.getAddressSpace()) {
        auto T4Quals = cv1T4.getQualifiers();
        T4Quals.addAddressSpace(T1Quals.getAddressSpace());
        QualType cv1T4WithAS = S.Context.getQualifiedType(T2, T4Quals);
        Sequence.AddQualificationConversionStep(cv1T4WithAS, ValueKind);
        cv1T4 = cv1T4WithAS;
      }
  
      //   In any case, the reference is bound to the resulting glvalue (or to
      //   an appropriate base class subobject).
      if (RefConv & Sema::ReferenceConversions::DerivedToBase)
        Sequence.AddDerivedToBaseCastStep(cv1T1, ValueKind);
      else if (RefConv & Sema::ReferenceConversions::ObjC)
        Sequence.AddObjCObjectConversionStep(cv1T1);
      else if (RefConv & Sema::ReferenceConversions::Qualification) {
        if (!S.Context.hasSameType(cv1T4, cv1T1))
          Sequence.AddQualificationConversionStep(cv1T1, ValueKind);
      }
      return;
    }
  
    //       - has a class type (i.e., T2 is a class type), where T1 is not
    //         reference-related to T2, and can be implicitly converted to an
    //         xvalue, class prvalue, or function lvalue of type "cv3 T3",
    //         where "cv1 T1" is reference-compatible with "cv3 T3",
    //
    // DR1287 removes the "implicitly" here.
    if (T2->isRecordType()) {
      if (RefRelationship == Sema::Ref_Incompatible) {
        ConvOvlResult = TryRefInitWithConversionFunction(
            S, Entity, Kind, Initializer, /*AllowRValues*/ true,
            /*IsLValueRef*/ isLValueRef, Sequence);
        if (ConvOvlResult)
          Sequence.SetOverloadFailure(
              InitializationSequence::FK_ReferenceInitOverloadFailed,
              ConvOvlResult);
  
        return;
      }
  
      if (RefRelationship == Sema::Ref_Compatible &&
          isRValueRef && InitCategory.isLValue()) {
        Sequence.SetFailed(
          InitializationSequence::FK_RValueReferenceBindingToLValue);
        return;
      }
  
      Sequence.SetFailed(InitializationSequence::FK_ReferenceInitDropsQualifiers);
      return;
    }
  
    //      - Otherwise, a temporary of type "cv1 T1" is created and initialized
    //        from the initializer expression using the rules for a non-reference
    //        copy-initialization (8.5). The reference is then bound to the
    //        temporary. [...]
  
    // Ignore address space of reference type at this point and perform address
    // space conversion after the reference binding step.
    QualType cv1T1IgnoreAS =
        T1Quals.hasAddressSpace()
            ? S.Context.getQualifiedType(T1, T1Quals.withoutAddressSpace())
            : cv1T1;
  
    InitializedEntity TempEntity =
        InitializedEntity::InitializeTemporary(cv1T1IgnoreAS);
  
    // FIXME: Why do we use an implicit conversion here rather than trying
    // copy-initialization?
    ImplicitConversionSequence ICS
      = S.TryImplicitConversion(Initializer, TempEntity.getType(),
                                /*SuppressUserConversions=*/false,
                                Sema::AllowedExplicit::None,
                                /*FIXME:InOverloadResolution=*/false,
                                /*CStyle=*/Kind.isCStyleOrFunctionalCast(),
                                /*AllowObjCWritebackConversion=*/false);
  
    if (ICS.isBad()) {
      // FIXME: Use the conversion function set stored in ICS to turn
      // this into an overloading ambiguity diagnostic. However, we need
      // to keep that set as an OverloadCandidateSet rather than as some
      // other kind of set.
      if (ConvOvlResult && !Sequence.getFailedCandidateSet().empty())
        Sequence.SetOverloadFailure(
                          InitializationSequence::FK_ReferenceInitOverloadFailed,
                                    ConvOvlResult);
      else if (S.Context.getCanonicalType(T2) == S.Context.OverloadTy)
        Sequence.SetFailed(InitializationSequence::FK_AddressOfOverloadFailed);
      else
        Sequence.SetFailed(InitializationSequence::FK_ReferenceInitFailed);
      return;
    } else {
      Sequence.AddConversionSequenceStep(ICS, TempEntity.getType());
    }
  
    //        [...] If T1 is reference-related to T2, cv1 must be the
    //        same cv-qualification as, or greater cv-qualification
    //        than, cv2; otherwise, the program is ill-formed.
    unsigned T1CVRQuals = T1Quals.getCVRQualifiers();
    unsigned T2CVRQuals = T2Quals.getCVRQualifiers();
    if ((RefRelationship == Sema::Ref_Related &&
         (T1CVRQuals | T2CVRQuals) != T1CVRQuals) ||
        !T1Quals.isAddressSpaceSupersetOf(T2Quals)) {
      Sequence.SetFailed(InitializationSequence::FK_ReferenceInitDropsQualifiers);
      return;
    }
  
    //   [...] If T1 is reference-related to T2 and the reference is an rvalue
    //   reference, the initializer expression shall not be an lvalue.
    if (RefRelationship >= Sema::Ref_Related && !isLValueRef &&
        InitCategory.isLValue()) {
      Sequence.SetFailed(
                      InitializationSequence::FK_RValueReferenceBindingToLValue);
      return;
    }
  
    Sequence.AddReferenceBindingStep(cv1T1IgnoreAS, /*BindingTemporary=*/true);
  
    if (T1Quals.hasAddressSpace()) {
      if (!Qualifiers::isAddressSpaceSupersetOf(T1Quals.getAddressSpace(),
                                                LangAS::Default)) {
        Sequence.SetFailed(
            InitializationSequence::FK_ReferenceAddrspaceMismatchTemporary);
        return;
      }
      Sequence.AddQualificationConversionStep(cv1T1, isLValueRef ? VK_LValue
                                                                 : VK_XValue);
    }
  }
  
  /// Attempt character array initialization from a string literal
  /// (C++ [dcl.init.string], C99 6.7.8).
  static void TryStringLiteralInitialization(Sema &S,
                                             const InitializedEntity &Entity,
                                             const InitializationKind &Kind,
                                             Expr *Initializer,
                                         InitializationSequence &Sequence) {
    Sequence.AddStringInitStep(Entity.getType());
  }
  
  /// Attempt value initialization (C++ [dcl.init]p7).
  static void TryValueInitialization(Sema &S,
                                     const InitializedEntity &Entity,
                                     const InitializationKind &Kind,
                                     InitializationSequence &Sequence,
                                     InitListExpr *InitList) {
    assert((!InitList || InitList->getNumInits() == 0) &&
           "Shouldn't use value-init for non-empty init lists");
  
    // C++98 [dcl.init]p5, C++11 [dcl.init]p7:
    //
    //   To value-initialize an object of type T means:
    QualType T = Entity.getType();
  
    //     -- if T is an array type, then each element is value-initialized;
    T = S.Context.getBaseElementType(T);
  
    if (const RecordType *RT = T->getAs<RecordType>()) {
      if (CXXRecordDecl *ClassDecl = dyn_cast<CXXRecordDecl>(RT->getDecl())) {
        bool NeedZeroInitialization = true;
        // C++98:
        // -- if T is a class type (clause 9) with a user-declared constructor
        //    (12.1), then the default constructor for T is called (and the
        //    initialization is ill-formed if T has no accessible default
        //    constructor);
        // C++11:
        // -- if T is a class type (clause 9) with either no default constructor
        //    (12.1 [class.ctor]) or a default constructor that is user-provided
        //    or deleted, then the object is default-initialized;
        //
        // Note that the C++11 rule is the same as the C++98 rule if there are no
        // defaulted or deleted constructors, so we just use it unconditionally.
        CXXConstructorDecl *CD = S.LookupDefaultConstructor(ClassDecl);
        if (!CD || !CD->getCanonicalDecl()->isDefaulted() || CD->isDeleted())
          NeedZeroInitialization = false;
  
        // -- if T is a (possibly cv-qualified) non-union class type without a
        //    user-provided or deleted default constructor, then the object is
        //    zero-initialized and, if T has a non-trivial default constructor,
        //    default-initialized;
        // The 'non-union' here was removed by DR1502. The 'non-trivial default
        // constructor' part was removed by DR1507.
        if (NeedZeroInitialization)
          Sequence.AddZeroInitializationStep(Entity.getType());
  
        // C++03:
        // -- if T is a non-union class type without a user-declared constructor,
        //    then every non-static data member and base class component of T is
        //    value-initialized;
        // [...] A program that calls for [...] value-initialization of an
        // entity of reference type is ill-formed.
        //
        // C++11 doesn't need this handling, because value-initialization does not
        // occur recursively there, and the implicit default constructor is
        // defined as deleted in the problematic cases.
        if (!S.getLangOpts().CPlusPlus11 &&
            ClassDecl->hasUninitializedReferenceMember()) {
          Sequence.SetFailed(InitializationSequence::FK_TooManyInitsForReference);
          return;
        }
  
        // If this is list-value-initialization, pass the empty init list on when
        // building the constructor call. This affects the semantics of a few
        // things (such as whether an explicit default constructor can be called).
        Expr *InitListAsExpr = InitList;
        MultiExprArg Args(&InitListAsExpr, InitList ? 1 : 0);
        bool InitListSyntax = InitList;
  
        // FIXME: Instead of creating a CXXConstructExpr of array type here,
        // wrap a class-typed CXXConstructExpr in an ArrayInitLoopExpr.
        return TryConstructorInitialization(
            S, Entity, Kind, Args, T, Entity.getType(), Sequence, InitListSyntax);
      }
    }
  
    Sequence.AddZeroInitializationStep(Entity.getType());
  }
  
  /// Attempt default initialization (C++ [dcl.init]p6).
  static void TryDefaultInitialization(Sema &S,
                                       const InitializedEntity &Entity,
                                       const InitializationKind &Kind,
                                       InitializationSequence &Sequence) {
    assert(Kind.getKind() == InitializationKind::IK_Default);
  
    // C++ [dcl.init]p6:
    //   To default-initialize an object of type T means:
    //     - if T is an array type, each element is default-initialized;
    QualType DestType = S.Context.getBaseElementType(Entity.getType());
  
    //     - if T is a (possibly cv-qualified) class type (Clause 9), the default
    //       constructor for T is called (and the initialization is ill-formed if
    //       T has no accessible default constructor);
    if (DestType->isRecordType() && S.getLangOpts().CPlusPlus) {
      TryConstructorInitialization(S, Entity, Kind, None, DestType,
                                   Entity.getType(), Sequence);
      return;
    }
  
    //     - otherwise, no initialization is performed.
  
    //   If a program calls for the default initialization of an object of
    //   a const-qualified type T, T shall be a class type with a user-provided
    //   default constructor.
    if (DestType.isConstQualified() && S.getLangOpts().CPlusPlus) {
      if (!maybeRecoverWithZeroInitialization(S, Sequence, Entity))
        Sequence.SetFailed(InitializationSequence::FK_DefaultInitOfConst);
      return;
    }
  
    // If the destination type has a lifetime property, zero-initialize it.
    if (DestType.getQualifiers().hasObjCLifetime()) {
      Sequence.AddZeroInitializationStep(Entity.getType());
      return;
    }
  }
  
  /// Attempt a user-defined conversion between two types (C++ [dcl.init]),
  /// which enumerates all conversion functions and performs overload resolution
  /// to select the best.
  static void TryUserDefinedConversion(Sema &S,
                                       QualType DestType,
                                       const InitializationKind &Kind,
                                       Expr *Initializer,
                                       InitializationSequence &Sequence,
                                       bool TopLevelOfInitList) {
    assert(!DestType->isReferenceType() && "References are handled elsewhere");
    QualType SourceType = Initializer->getType();
    assert((DestType->isRecordType() || SourceType->isRecordType()) &&
           "Must have a class type to perform a user-defined conversion");
  
    // Build the candidate set directly in the initialization sequence
    // structure, so that it will persist if we fail.
    OverloadCandidateSet &CandidateSet = Sequence.getFailedCandidateSet();
    CandidateSet.clear(OverloadCandidateSet::CSK_InitByUserDefinedConversion);
    CandidateSet.setDestAS(DestType.getQualifiers().getAddressSpace());
  
    // Determine whether we are allowed to call explicit constructors or
    // explicit conversion operators.
    bool AllowExplicit = Kind.AllowExplicit();
  
    if (const RecordType *DestRecordType = DestType->getAs<RecordType>()) {
      // The type we're converting to is a class type. Enumerate its constructors
      // to see if there is a suitable conversion.
      CXXRecordDecl *DestRecordDecl
        = cast<CXXRecordDecl>(DestRecordType->getDecl());
  
      // Try to complete the type we're converting to.
      if (S.isCompleteType(Kind.getLocation(), DestType)) {
        for (NamedDecl *D : S.LookupConstructors(DestRecordDecl)) {
          auto Info = getConstructorInfo(D);
          if (!Info.Constructor)
            continue;
  
          if (!Info.Constructor->isInvalidDecl() &&
              Info.Constructor->isConvertingConstructor(/*AllowExplicit*/true)) {
            if (Info.ConstructorTmpl)
              S.AddTemplateOverloadCandidate(
                  Info.ConstructorTmpl, Info.FoundDecl,
                  /*ExplicitArgs*/ nullptr, Initializer, CandidateSet,
                  /*SuppressUserConversions=*/true,
                  /*PartialOverloading*/ false, AllowExplicit);
            else
              S.AddOverloadCandidate(Info.Constructor, Info.FoundDecl,
                                     Initializer, CandidateSet,
                                     /*SuppressUserConversions=*/true,
                                     /*PartialOverloading*/ false, AllowExplicit);
          }
        }
      }
    }
  
    SourceLocation DeclLoc = Initializer->getBeginLoc();
  
    if (const RecordType *SourceRecordType = SourceType->getAs<RecordType>()) {
      // The type we're converting from is a class type, enumerate its conversion
      // functions.
  
      // We can only enumerate the conversion functions for a complete type; if
      // the type isn't complete, simply skip this step.
      if (S.isCompleteType(DeclLoc, SourceType)) {
        CXXRecordDecl *SourceRecordDecl
          = cast<CXXRecordDecl>(SourceRecordType->getDecl());
  
        const auto &Conversions =
            SourceRecordDecl->getVisibleConversionFunctions();
        for (auto I = Conversions.begin(), E = Conversions.end(); I != E; ++I) {
          NamedDecl *D = *I;
          CXXRecordDecl *ActingDC = cast<CXXRecordDecl>(D->getDeclContext());
          if (isa<UsingShadowDecl>(D))
            D = cast<UsingShadowDecl>(D)->getTargetDecl();
  
          FunctionTemplateDecl *ConvTemplate = dyn_cast<FunctionTemplateDecl>(D);
          CXXConversionDecl *Conv;
          if (ConvTemplate)
            Conv = cast<CXXConversionDecl>(ConvTemplate->getTemplatedDecl());
          else
            Conv = cast<CXXConversionDecl>(D);
  
          if (ConvTemplate)
            S.AddTemplateConversionCandidate(
                ConvTemplate, I.getPair(), ActingDC, Initializer, DestType,
                CandidateSet, AllowExplicit, AllowExplicit);
          else
            S.AddConversionCandidate(Conv, I.getPair(), ActingDC, Initializer,
                                     DestType, CandidateSet, AllowExplicit,
                                     AllowExplicit);
        }
      }
    }
  
    // Perform overload resolution. If it fails, return the failed result.
    OverloadCandidateSet::iterator Best;
    if (OverloadingResult Result
          = CandidateSet.BestViableFunction(S, DeclLoc, Best)) {
      Sequence.SetOverloadFailure(
                          InitializationSequence::FK_UserConversionOverloadFailed,
                                  Result);
      return;
    }
  
    FunctionDecl *Function = Best->Function;
    Function->setReferenced();
    bool HadMultipleCandidates = (CandidateSet.size() > 1);
  
    if (isa<CXXConstructorDecl>(Function)) {
      // Add the user-defined conversion step. Any cv-qualification conversion is
      // subsumed by the initialization. Per DR5, the created temporary is of the
      // cv-unqualified type of the destination.
      Sequence.AddUserConversionStep(Function, Best->FoundDecl,
                                     DestType.getUnqualifiedType(),
                                     HadMultipleCandidates);
  
      // C++14 and before:
      //   - if the function is a constructor, the call initializes a temporary
      //     of the cv-unqualified version of the destination type. The [...]
      //     temporary [...] is then used to direct-initialize, according to the
      //     rules above, the object that is the destination of the
      //     copy-initialization.
      // Note that this just performs a simple object copy from the temporary.
      //
      // C++17:
      //   - if the function is a constructor, the call is a prvalue of the
      //     cv-unqualified version of the destination type whose return object
      //     is initialized by the constructor. The call is used to
      //     direct-initialize, according to the rules above, the object that
      //     is the destination of the copy-initialization.
      // Therefore we need to do nothing further.
      //
      // FIXME: Mark this copy as extraneous.
      if (!S.getLangOpts().CPlusPlus17)
        Sequence.AddFinalCopy(DestType);
      else if (DestType.hasQualifiers())
        Sequence.AddQualificationConversionStep(DestType, VK_RValue);
      return;
    }
  
    // Add the user-defined conversion step that calls the conversion function.
    QualType ConvType = Function->getCallResultType();
    Sequence.AddUserConversionStep(Function, Best->FoundDecl, ConvType,
                                   HadMultipleCandidates);
  
    if (ConvType->getAs<RecordType>()) {
      //   The call is used to direct-initialize [...] the object that is the
      //   destination of the copy-initialization.
      //
      // In C++17, this does not call a constructor if we enter /17.6.1:
      //   - If the initializer expression is a prvalue and the cv-unqualified
      //     version of the source type is the same as the class of the
      //     destination [... do not make an extra copy]
      //
      // FIXME: Mark this copy as extraneous.
      if (!S.getLangOpts().CPlusPlus17 ||
          Function->getReturnType()->isReferenceType() ||
          !S.Context.hasSameUnqualifiedType(ConvType, DestType))
        Sequence.AddFinalCopy(DestType);
      else if (!S.Context.hasSameType(ConvType, DestType))
        Sequence.AddQualificationConversionStep(DestType, VK_RValue);
      return;
    }
  
    // If the conversion following the call to the conversion function
    // is interesting, add it as a separate step.
    if (Best->FinalConversion.First || Best->FinalConversion.Second ||
        Best->FinalConversion.Third) {
      ImplicitConversionSequence ICS;
      ICS.setStandard();
      ICS.Standard = Best->FinalConversion;
      Sequence.AddConversionSequenceStep(ICS, DestType, TopLevelOfInitList);
    }
  }
  
  /// An egregious hack for compatibility with libstdc++-4.2: in <tr1/hashtable>,
  /// a function with a pointer return type contains a 'return false;' statement.
  /// In C++11, 'false' is not a null pointer, so this breaks the build of any
  /// code using that header.
  ///
  /// Work around this by treating 'return false;' as zero-initializing the result
  /// if it's used in a pointer-returning function in a system header.
  static bool isLibstdcxxPointerReturnFalseHack(Sema &S,
                                                const InitializedEntity &Entity,
                                                const Expr *Init) {
    return S.getLangOpts().CPlusPlus11 &&
           Entity.getKind() == InitializedEntity::EK_Result &&
           Entity.getType()->isPointerType() &&
           isa<CXXBoolLiteralExpr>(Init) &&
           !cast<CXXBoolLiteralExpr>(Init)->getValue() &&
           S.getSourceManager().isInSystemHeader(Init->getExprLoc());
  }
  
  /// The non-zero enum values here are indexes into diagnostic alternatives.
  enum InvalidICRKind { IIK_okay, IIK_nonlocal, IIK_nonscalar };
  
  /// Determines whether this expression is an acceptable ICR source.
  static InvalidICRKind isInvalidICRSource(ASTContext &C, Expr *e,
                                           bool isAddressOf, bool &isWeakAccess) {
    // Skip parens.
    e = e->IgnoreParens();
  
    // Skip address-of nodes.
    if (UnaryOperator *op = dyn_cast<UnaryOperator>(e)) {
      if (op->getOpcode() == UO_AddrOf)
        return isInvalidICRSource(C, op->getSubExpr(), /*addressof*/ true,
                                  isWeakAccess);
  
    // Skip certain casts.
    } else if (CastExpr *ce = dyn_cast<CastExpr>(e)) {
      switch (ce->getCastKind()) {
      case CK_Dependent:
      case CK_BitCast:
      case CK_LValueBitCast:
      case CK_NoOp:
        return isInvalidICRSource(C, ce->getSubExpr(), isAddressOf, isWeakAccess);
  
      case CK_ArrayToPointerDecay:
        return IIK_nonscalar;
  
      case CK_NullToPointer:
        return IIK_okay;
  
      default:
        break;
      }
  
    // If we have a declaration reference, it had better be a local variable.
    } else if (isa<DeclRefExpr>(e)) {
      // set isWeakAccess to true, to mean that there will be an implicit
      // load which requires a cleanup.
      if (e->getType().getObjCLifetime() == Qualifiers::OCL_Weak)
        isWeakAccess = true;
  
      if (!isAddressOf) return IIK_nonlocal;
  
      VarDecl *var = dyn_cast<VarDecl>(cast<DeclRefExpr>(e)->getDecl());
      if (!var) return IIK_nonlocal;
  
      return (var->hasLocalStorage() ? IIK_okay : IIK_nonlocal);
  
    // If we have a conditional operator, check both sides.
    } else if (ConditionalOperator *cond = dyn_cast<ConditionalOperator>(e)) {
      if (InvalidICRKind iik = isInvalidICRSource(C, cond->getLHS(), isAddressOf,
                                                  isWeakAccess))
        return iik;
  
      return isInvalidICRSource(C, cond->getRHS(), isAddressOf, isWeakAccess);
  
    // These are never scalar.
    } else if (isa<ArraySubscriptExpr>(e)) {
      return IIK_nonscalar;
  
    // Otherwise, it needs to be a null pointer constant.
    } else {
      return (e->isNullPointerConstant(C, Expr::NPC_ValueDependentIsNull)
              ? IIK_okay : IIK_nonlocal);
    }
  
    return IIK_nonlocal;
  }
  
  /// Check whether the given expression is a valid operand for an
  /// indirect copy/restore.
  static void checkIndirectCopyRestoreSource(Sema &S, Expr *src) {
    assert(src->isRValue());
    bool isWeakAccess = false;
    InvalidICRKind iik = isInvalidICRSource(S.Context, src, false, isWeakAccess);
    // If isWeakAccess to true, there will be an implicit
    // load which requires a cleanup.
    if (S.getLangOpts().ObjCAutoRefCount && isWeakAccess)
      S.Cleanup.setExprNeedsCleanups(true);
  
    if (iik == IIK_okay) return;
  
    S.Diag(src->getExprLoc(), diag::err_arc_nonlocal_writeback)
      << ((unsigned) iik - 1)  // shift index into diagnostic explanations
      << src->getSourceRange();
  }
  
  /// Determine whether we have compatible array types for the
  /// purposes of GNU by-copy array initialization.
  static bool hasCompatibleArrayTypes(ASTContext &Context, const ArrayType *Dest,
                                      const ArrayType *Source) {
    // If the source and destination array types are equivalent, we're
    // done.
    if (Context.hasSameType(QualType(Dest, 0), QualType(Source, 0)))
      return true;
  
    // Make sure that the element types are the same.
    if (!Context.hasSameType(Dest->getElementType(), Source->getElementType()))
      return false;
  
    // The only mismatch we allow is when the destination is an
    // incomplete array type and the source is a constant array type.
    return Source->isConstantArrayType() && Dest->isIncompleteArrayType();
  }
  
  static bool tryObjCWritebackConversion(Sema &S,
                                         InitializationSequence &Sequence,
                                         const InitializedEntity &Entity,
                                         Expr *Initializer) {
    bool ArrayDecay = false;
    QualType ArgType = Initializer->getType();
    QualType ArgPointee;
    if (const ArrayType *ArgArrayType = S.Context.getAsArrayType(ArgType)) {
      ArrayDecay = true;
      ArgPointee = ArgArrayType->getElementType();
      ArgType = S.Context.getPointerType(ArgPointee);
    }
  
    // Handle write-back conversion.
    QualType ConvertedArgType;
    if (!S.isObjCWritebackConversion(ArgType, Entity.getType(),
                                     ConvertedArgType))
      return false;
  
    // We should copy unless we're passing to an argument explicitly
    // marked 'out'.
    bool ShouldCopy = true;
    if (ParmVarDecl *param = cast_or_null<ParmVarDecl>(Entity.getDecl()))
      ShouldCopy = (param->getObjCDeclQualifier() != ParmVarDecl::OBJC_TQ_Out);
  
    // Do we need an lvalue conversion?
    if (ArrayDecay || Initializer->isGLValue()) {
      ImplicitConversionSequence ICS;
      ICS.setStandard();
      ICS.Standard.setAsIdentityConversion();
  
      QualType ResultType;
      if (ArrayDecay) {
        ICS.Standard.First = ICK_Array_To_Pointer;
        ResultType = S.Context.getPointerType(ArgPointee);
      } else {
        ICS.Standard.First = ICK_Lvalue_To_Rvalue;
        ResultType = Initializer->getType().getNonLValueExprType(S.Context);
      }
  
      Sequence.AddConversionSequenceStep(ICS, ResultType);
    }
  
    Sequence.AddPassByIndirectCopyRestoreStep(Entity.getType(), ShouldCopy);
    return true;
  }
  
  static bool TryOCLSamplerInitialization(Sema &S,
                                          InitializationSequence &Sequence,
                                          QualType DestType,
                                          Expr *Initializer) {
    if (!S.getLangOpts().OpenCL || !DestType->isSamplerT() ||
        (!Initializer->isIntegerConstantExpr(S.Context) &&
        !Initializer->getType()->isSamplerT()))
      return false;
  
    Sequence.AddOCLSamplerInitStep(DestType);
    return true;
  }
  
  static bool IsZeroInitializer(Expr *Initializer, Sema &S) {
    return Initializer->isIntegerConstantExpr(S.getASTContext()) &&
      (Initializer->EvaluateKnownConstInt(S.getASTContext()) == 0);
  }
  
  static bool TryOCLZeroOpaqueTypeInitialization(Sema &S,
                                                 InitializationSequence &Sequence,
                                                 QualType DestType,
                                                 Expr *Initializer) {
    if (!S.getLangOpts().OpenCL)
      return false;
  
    //
    // OpenCL 1.2 spec, s6.12.10
    //
    // The event argument can also be used to associate the
    // async_work_group_copy with a previous async copy allowing
    // an event to be shared by multiple async copies; otherwise
    // event should be zero.
    //
    if (DestType->isEventT() || DestType->isQueueT()) {
      if (!IsZeroInitializer(Initializer, S))
        return false;
  
      Sequence.AddOCLZeroOpaqueTypeStep(DestType);
      return true;
    }
  
    // We should allow zero initialization for all types defined in the
    // cl_intel_device_side_avc_motion_estimation extension, except
    // intel_sub_group_avc_mce_payload_t and intel_sub_group_avc_mce_result_t.
    if (S.getOpenCLOptions().isEnabled(
            "cl_intel_device_side_avc_motion_estimation") &&
        DestType->isOCLIntelSubgroupAVCType()) {
      if (DestType->isOCLIntelSubgroupAVCMcePayloadType() ||
          DestType->isOCLIntelSubgroupAVCMceResultType())
        return false;
      if (!IsZeroInitializer(Initializer, S))
        return false;
  
      Sequence.AddOCLZeroOpaqueTypeStep(DestType);
      return true;
    }
  
    return false;
  }
  
  InitializationSequence::InitializationSequence(Sema &S,
                                                 const InitializedEntity &Entity,
                                                 const InitializationKind &Kind,
                                                 MultiExprArg Args,
                                                 bool TopLevelOfInitList,
                                                 bool TreatUnavailableAsInvalid)
      : FailedCandidateSet(Kind.getLocation(), OverloadCandidateSet::CSK_Normal) {
    InitializeFrom(S, Entity, Kind, Args, TopLevelOfInitList,
                   TreatUnavailableAsInvalid);
  }
  
  /// Tries to get a FunctionDecl out of `E`. If it succeeds and we can take the
  /// address of that function, this returns true. Otherwise, it returns false.
  static bool isExprAnUnaddressableFunction(Sema &S, const Expr *E) {
    auto *DRE = dyn_cast<DeclRefExpr>(E);
    if (!DRE || !isa<FunctionDecl>(DRE->getDecl()))
      return false;
  
    return !S.checkAddressOfFunctionIsAvailable(
        cast<FunctionDecl>(DRE->getDecl()));
  }
  
  /// Determine whether we can perform an elementwise array copy for this kind
  /// of entity.
  static bool canPerformArrayCopy(const InitializedEntity &Entity) {
    switch (Entity.getKind()) {
    case InitializedEntity::EK_LambdaCapture:
      // C++ [expr.prim.lambda]p24:
      //   For array members, the array elements are direct-initialized in
      //   increasing subscript order.
      return true;
  
    case InitializedEntity::EK_Variable:
      // C++ [dcl.decomp]p1:
      //   [...] each element is copy-initialized or direct-initialized from the
      //   corresponding element of the assignment-expression [...]
      return isa<DecompositionDecl>(Entity.getDecl());
  
    case InitializedEntity::EK_Member:
      // C++ [class.copy.ctor]p14:
      //   - if the member is an array, each element is direct-initialized with
      //     the corresponding subobject of x
      return Entity.isImplicitMemberInitializer();
  
    case InitializedEntity::EK_ArrayElement:
      // All the above cases are intended to apply recursively, even though none
      // of them actually say that.
      if (auto *E = Entity.getParent())
        return canPerformArrayCopy(*E);
      break;
  
    default:
      break;
    }
  
    return false;
  }
  
  void InitializationSequence::InitializeFrom(Sema &S,
                                              const InitializedEntity &Entity,
                                              const InitializationKind &Kind,
                                              MultiExprArg Args,
                                              bool TopLevelOfInitList,
                                              bool TreatUnavailableAsInvalid) {
    ASTContext &Context = S.Context;
  
    // Eliminate non-overload placeholder types in the arguments.  We
    // need to do this before checking whether types are dependent
    // because lowering a pseudo-object expression might well give us
    // something of dependent type.
    for (unsigned I = 0, E = Args.size(); I != E; ++I)
      if (Args[I]->getType()->isNonOverloadPlaceholderType()) {
        // FIXME: should we be doing this here?
        ExprResult result = S.CheckPlaceholderExpr(Args[I]);
        if (result.isInvalid()) {
          SetFailed(FK_PlaceholderType);
          return;
        }
        Args[I] = result.get();
      }
  
    // C++0x [dcl.init]p16:
    //   The semantics of initializers are as follows. The destination type is
    //   the type of the object or reference being initialized and the source
    //   type is the type of the initializer expression. The source type is not
    //   defined when the initializer is a braced-init-list or when it is a
    //   parenthesized list of expressions.
    QualType DestType = Entity.getType();
  
    if (DestType->isDependentType() ||
        Expr::hasAnyTypeDependentArguments(Args)) {
      SequenceKind = DependentSequence;
      return;
    }
  
    // Almost everything is a normal sequence.
    setSequenceKind(NormalSequence);
  
    QualType SourceType;
    Expr *Initializer = nullptr;
    if (Args.size() == 1) {
      Initializer = Args[0];
      if (S.getLangOpts().ObjC) {
        if (S.CheckObjCBridgeRelatedConversions(Initializer->getBeginLoc(),
                                                DestType, Initializer->getType(),
                                                Initializer) ||
            S.CheckConversionToObjCLiteral(DestType, Initializer))
          Args[0] = Initializer;
      }
      if (!isa<InitListExpr>(Initializer))
        SourceType = Initializer->getType();
    }
  
    //     - If the initializer is a (non-parenthesized) braced-init-list, the
    //       object is list-initialized (8.5.4).
    if (Kind.getKind() != InitializationKind::IK_Direct) {
      if (InitListExpr *InitList = dyn_cast_or_null<InitListExpr>(Initializer)) {
        TryListInitialization(S, Entity, Kind, InitList, *this,
                              TreatUnavailableAsInvalid);
        return;
      }
    }
  
    //     - If the destination type is a reference type, see 8.5.3.
    if (DestType->isReferenceType()) {
      // C++0x [dcl.init.ref]p1:
      //   A variable declared to be a T& or T&&, that is, "reference to type T"
      //   (8.3.2), shall be initialized by an object, or function, of type T or
      //   by an object that can be converted into a T.
      // (Therefore, multiple arguments are not permitted.)
      if (Args.size() != 1)
        SetFailed(FK_TooManyInitsForReference);
      // C++17 [dcl.init.ref]p5:
      //   A reference [...] is initialized by an expression [...] as follows:
      // If the initializer is not an expression, presumably we should reject,
      // but the standard fails to actually say so.
      else if (isa<InitListExpr>(Args[0]))
        SetFailed(FK_ParenthesizedListInitForReference);
      else
        TryReferenceInitialization(S, Entity, Kind, Args[0], *this);
      return;
    }
  
    //     - If the initializer is (), the object is value-initialized.
    if (Kind.getKind() == InitializationKind::IK_Value ||
        (Kind.getKind() == InitializationKind::IK_Direct && Args.empty())) {
      TryValueInitialization(S, Entity, Kind, *this);
      return;
    }
  
    // Handle default initialization.
    if (Kind.getKind() == InitializationKind::IK_Default) {
      TryDefaultInitialization(S, Entity, Kind, *this);
      return;
    }
  
    //     - If the destination type is an array of characters, an array of
    //       char16_t, an array of char32_t, or an array of wchar_t, and the
    //       initializer is a string literal, see 8.5.2.
    //     - Otherwise, if the destination type is an array, the program is
    //       ill-formed.
    if (const ArrayType *DestAT = Context.getAsArrayType(DestType)) {
      if (Initializer && isa<VariableArrayType>(DestAT)) {
        SetFailed(FK_VariableLengthArrayHasInitializer);
        return;
      }
  
      if (Initializer) {
        switch (IsStringInit(Initializer, DestAT, Context)) {
        case SIF_None:
          TryStringLiteralInitialization(S, Entity, Kind, Initializer, *this);
          return;
        case SIF_NarrowStringIntoWideChar:
          SetFailed(FK_NarrowStringIntoWideCharArray);
          return;
        case SIF_WideStringIntoChar:
          SetFailed(FK_WideStringIntoCharArray);
          return;
        case SIF_IncompatWideStringIntoWideChar:
          SetFailed(FK_IncompatWideStringIntoWideChar);
          return;
        case SIF_PlainStringIntoUTF8Char:
          SetFailed(FK_PlainStringIntoUTF8Char);
          return;
        case SIF_UTF8StringIntoPlainChar:
          SetFailed(FK_UTF8StringIntoPlainChar);
          return;
        case SIF_Other:
          break;
        }
      }
  
      // Some kinds of initialization permit an array to be initialized from
      // another array of the same type, and perform elementwise initialization.
      if (Initializer && isa<ConstantArrayType>(DestAT) &&
          S.Context.hasSameUnqualifiedType(Initializer->getType(),
                                           Entity.getType()) &&
          canPerformArrayCopy(Entity)) {
        // If source is a prvalue, use it directly.
        if (Initializer->getValueKind() == VK_RValue) {
          AddArrayInitStep(DestType, /*IsGNUExtension*/false);
          return;
        }
  
        // Emit element-at-a-time copy loop.
        InitializedEntity Element =
            InitializedEntity::InitializeElement(S.Context, 0, Entity);
        QualType InitEltT =
            Context.getAsArrayType(Initializer->getType())->getElementType();
        OpaqueValueExpr OVE(Initializer->getExprLoc(), InitEltT,
                            Initializer->getValueKind(),
                            Initializer->getObjectKind());
        Expr *OVEAsExpr = &OVE;
        InitializeFrom(S, Element, Kind, OVEAsExpr, TopLevelOfInitList,
                       TreatUnavailableAsInvalid);
        if (!Failed())
          AddArrayInitLoopStep(Entity.getType(), InitEltT);
        return;
      }
  
      // Note: as an GNU C extension, we allow initialization of an
      // array from a compound literal that creates an array of the same
      // type, so long as the initializer has no side effects.
      if (!S.getLangOpts().CPlusPlus && Initializer &&
          isa<CompoundLiteralExpr>(Initializer->IgnoreParens()) &&
          Initializer->getType()->isArrayType()) {
        const ArrayType *SourceAT
          = Context.getAsArrayType(Initializer->getType());
        if (!hasCompatibleArrayTypes(S.Context, DestAT, SourceAT))
          SetFailed(FK_ArrayTypeMismatch);
        else if (Initializer->HasSideEffects(S.Context))
          SetFailed(FK_NonConstantArrayInit);
        else {
          AddArrayInitStep(DestType, /*IsGNUExtension*/true);
        }
      }
      // Note: as a GNU C++ extension, we allow list-initialization of a
      // class member of array type from a parenthesized initializer list.
      else if (S.getLangOpts().CPlusPlus &&
               Entity.getKind() == InitializedEntity::EK_Member &&
               Initializer && isa<InitListExpr>(Initializer)) {
        TryListInitialization(S, Entity, Kind, cast<InitListExpr>(Initializer),
                              *this, TreatUnavailableAsInvalid);
        AddParenthesizedArrayInitStep(DestType);
      } else if (DestAT->getElementType()->isCharType())
        SetFailed(FK_ArrayNeedsInitListOrStringLiteral);
      else if (IsWideCharCompatible(DestAT->getElementType(), Context))
        SetFailed(FK_ArrayNeedsInitListOrWideStringLiteral);
      else
        SetFailed(FK_ArrayNeedsInitList);
  
      return;
    }
  
    // Determine whether we should consider writeback conversions for
    // Objective-C ARC.
    bool allowObjCWritebackConversion = S.getLangOpts().ObjCAutoRefCount &&
           Entity.isParameterKind();
  
    if (TryOCLSamplerInitialization(S, *this, DestType, Initializer))
      return;
  
    // We're at the end of the line for C: it's either a write-back conversion
    // or it's a C assignment. There's no need to check anything else.
    if (!S.getLangOpts().CPlusPlus) {
      // If allowed, check whether this is an Objective-C writeback conversion.
      if (allowObjCWritebackConversion &&
          tryObjCWritebackConversion(S, *this, Entity, Initializer)) {
        return;
      }
  
      if (TryOCLZeroOpaqueTypeInitialization(S, *this, DestType, Initializer))
        return;
  
      // Handle initialization in C
      AddCAssignmentStep(DestType);
      MaybeProduceObjCObject(S, *this, Entity);
      return;
    }
  
    assert(S.getLangOpts().CPlusPlus);
  
    //     - If the destination type is a (possibly cv-qualified) class type:
    if (DestType->isRecordType()) {
      //     - If the initialization is direct-initialization, or if it is
      //       copy-initialization where the cv-unqualified version of the
      //       source type is the same class as, or a derived class of, the
      //       class of the destination, constructors are considered. [...]
      if (Kind.getKind() == InitializationKind::IK_Direct ||
          (Kind.getKind() == InitializationKind::IK_Copy &&
           (Context.hasSameUnqualifiedType(SourceType, DestType) ||
            S.IsDerivedFrom(Initializer->getBeginLoc(), SourceType, DestType))))
        TryConstructorInitialization(S, Entity, Kind, Args,
                                     DestType, DestType, *this);
      //     - Otherwise (i.e., for the remaining copy-initialization cases),
      //       user-defined conversion sequences that can convert from the source
      //       type to the destination type or (when a conversion function is
      //       used) to a derived class thereof are enumerated as described in
      //       13.3.1.4, and the best one is chosen through overload resolution
      //       (13.3).
      else
        TryUserDefinedConversion(S, DestType, Kind, Initializer, *this,
                                 TopLevelOfInitList);
      return;
    }
  
    assert(Args.size() >= 1 && "Zero-argument case handled above");
  
    // The remaining cases all need a source type.
    if (Args.size() > 1) {
      SetFailed(FK_TooManyInitsForScalar);
      return;
    } else if (isa<InitListExpr>(Args[0])) {
      SetFailed(FK_ParenthesizedListInitForScalar);
      return;
    }
  
    //    - Otherwise, if the source type is a (possibly cv-qualified) class
    //      type, conversion functions are considered.
    if (!SourceType.isNull() && SourceType->isRecordType()) {
      // For a conversion to _Atomic(T) from either T or a class type derived
      // from T, initialize the T object then convert to _Atomic type.
      bool NeedAtomicConversion = false;
      if (const AtomicType *Atomic = DestType->getAs<AtomicType>()) {
        if (Context.hasSameUnqualifiedType(SourceType, Atomic->getValueType()) ||
            S.IsDerivedFrom(Initializer->getBeginLoc(), SourceType,
                            Atomic->getValueType())) {
          DestType = Atomic->getValueType();
          NeedAtomicConversion = true;
        }
      }
  
      TryUserDefinedConversion(S, DestType, Kind, Initializer, *this,
                               TopLevelOfInitList);
      MaybeProduceObjCObject(S, *this, Entity);
      if (!Failed() && NeedAtomicConversion)
        AddAtomicConversionStep(Entity.getType());
      return;
    }
  
    //    - Otherwise, if the initialization is direct-initialization, the source
    //    type is std::nullptr_t, and the destination type is bool, the initial
    //    value of the object being initialized is false.
    if (!SourceType.isNull() && SourceType->isNullPtrType() &&
        DestType->isBooleanType() &&
        Kind.getKind() == InitializationKind::IK_Direct) {
      AddConversionSequenceStep(
          ImplicitConversionSequence::getNullptrToBool(SourceType, DestType,
                                                       Initializer->isGLValue()),
          DestType);
      return;
    }
  
    //    - Otherwise, the initial value of the object being initialized is the
    //      (possibly converted) value of the initializer expression. Standard
    //      conversions (Clause 4) will be used, if necessary, to convert the
    //      initializer expression to the cv-unqualified version of the
    //      destination type; no user-defined conversions are considered.
  
    ImplicitConversionSequence ICS
      = S.TryImplicitConversion(Initializer, DestType,
                                /*SuppressUserConversions*/true,
                                Sema::AllowedExplicit::None,
                                /*InOverloadResolution*/ false,
                                /*CStyle=*/Kind.isCStyleOrFunctionalCast(),
                                allowObjCWritebackConversion);
  
    if (ICS.isStandard() &&
        ICS.Standard.Second == ICK_Writeback_Conversion) {
      // Objective-C ARC writeback conversion.
  
      // We should copy unless we're passing to an argument explicitly
      // marked 'out'.
      bool ShouldCopy = true;
      if (ParmVarDecl *Param = cast_or_null<ParmVarDecl>(Entity.getDecl()))
        ShouldCopy = (Param->getObjCDeclQualifier() != ParmVarDecl::OBJC_TQ_Out);
  
      // If there was an lvalue adjustment, add it as a separate conversion.
      if (ICS.Standard.First == ICK_Array_To_Pointer ||
          ICS.Standard.First == ICK_Lvalue_To_Rvalue) {
        ImplicitConversionSequence LvalueICS;
        LvalueICS.setStandard();
        LvalueICS.Standard.setAsIdentityConversion();
        LvalueICS.Standard.setAllToTypes(ICS.Standard.getToType(0));
        LvalueICS.Standard.First = ICS.Standard.First;
        AddConversionSequenceStep(LvalueICS, ICS.Standard.getToType(0));
      }
  
      AddPassByIndirectCopyRestoreStep(DestType, ShouldCopy);
    } else if (ICS.isBad()) {
      DeclAccessPair dap;
      if (isLibstdcxxPointerReturnFalseHack(S, Entity, Initializer)) {
        AddZeroInitializationStep(Entity.getType());
      } else if (Initializer->getType() == Context.OverloadTy &&
                 !S.ResolveAddressOfOverloadedFunction(Initializer, DestType,
                                                       false, dap))
        SetFailed(InitializationSequence::FK_AddressOfOverloadFailed);
      else if (Initializer->getType()->isFunctionType() &&
               isExprAnUnaddressableFunction(S, Initializer))
        SetFailed(InitializationSequence::FK_AddressOfUnaddressableFunction);
      else
        SetFailed(InitializationSequence::FK_ConversionFailed);
    } else {
      AddConversionSequenceStep(ICS, DestType, TopLevelOfInitList);
  
      MaybeProduceObjCObject(S, *this, Entity);
    }
  }
  
  InitializationSequence::~InitializationSequence() {
    for (auto &S : Steps)
      S.Destroy();
  }
  
  //===----------------------------------------------------------------------===//
  // Perform initialization
  //===----------------------------------------------------------------------===//
  static Sema::AssignmentAction
  getAssignmentAction(const InitializedEntity &Entity, bool Diagnose = false) {
    switch(Entity.getKind()) {
    case InitializedEntity::EK_Variable:
    case InitializedEntity::EK_New:
    case InitializedEntity::EK_Exception:
    case InitializedEntity::EK_Base:
    case InitializedEntity::EK_Delegating:
      return Sema::AA_Initializing;
  
    case InitializedEntity::EK_Parameter:
      if (Entity.getDecl() &&
          isa<ObjCMethodDecl>(Entity.getDecl()->getDeclContext()))
        return Sema::AA_Sending;
  
      return Sema::AA_Passing;
  
    case InitializedEntity::EK_Parameter_CF_Audited:
      if (Entity.getDecl() &&
        isa<ObjCMethodDecl>(Entity.getDecl()->getDeclContext()))
        return Sema::AA_Sending;
  
      return !Diagnose ? Sema::AA_Passing : Sema::AA_Passing_CFAudited;
  
    case InitializedEntity::EK_Result:
    case InitializedEntity::EK_StmtExprResult: // FIXME: Not quite right.
      return Sema::AA_Returning;
  
    case InitializedEntity::EK_Temporary:
    case InitializedEntity::EK_RelatedResult:
      // FIXME: Can we tell apart casting vs. converting?
      return Sema::AA_Casting;
  
    case InitializedEntity::EK_Member:
    case InitializedEntity::EK_Binding:
    case InitializedEntity::EK_ArrayElement:
    case InitializedEntity::EK_VectorElement:
    case InitializedEntity::EK_ComplexElement:
    case InitializedEntity::EK_BlockElement:
    case InitializedEntity::EK_LambdaToBlockConversionBlockElement:
    case InitializedEntity::EK_LambdaCapture:
    case InitializedEntity::EK_CompoundLiteralInit:
      return Sema::AA_Initializing;
    }
  
    llvm_unreachable("Invalid EntityKind!");
  }
  
  /// Whether we should bind a created object as a temporary when
  /// initializing the given entity.
  static bool shouldBindAsTemporary(const InitializedEntity &Entity) {
    switch (Entity.getKind()) {
    case InitializedEntity::EK_ArrayElement:
    case InitializedEntity::EK_Member:
    case InitializedEntity::EK_Result:
    case InitializedEntity::EK_StmtExprResult:
    case InitializedEntity::EK_New:
    case InitializedEntity::EK_Variable:
    case InitializedEntity::EK_Base:
    case InitializedEntity::EK_Delegating:
    case InitializedEntity::EK_VectorElement:
    case InitializedEntity::EK_ComplexElement:
    case InitializedEntity::EK_Exception:
    case InitializedEntity::EK_BlockElement:
    case InitializedEntity::EK_LambdaToBlockConversionBlockElement:
    case InitializedEntity::EK_LambdaCapture:
    case InitializedEntity::EK_CompoundLiteralInit:
      return false;
  
    case InitializedEntity::EK_Parameter:
    case InitializedEntity::EK_Parameter_CF_Audited:
    case InitializedEntity::EK_Temporary:
    case InitializedEntity::EK_RelatedResult:
    case InitializedEntity::EK_Binding:
      return true;
    }
  
    llvm_unreachable("missed an InitializedEntity kind?");
  }
  
  /// Whether the given entity, when initialized with an object
  /// created for that initialization, requires destruction.
  static bool shouldDestroyEntity(const InitializedEntity &Entity) {
    switch (Entity.getKind()) {
      case InitializedEntity::EK_Result:
      case InitializedEntity::EK_StmtExprResult:
      case InitializedEntity::EK_New:
      case InitializedEntity::EK_Base:
      case InitializedEntity::EK_Delegating:
      case InitializedEntity::EK_VectorElement:
      case InitializedEntity::EK_ComplexElement:
      case InitializedEntity::EK_BlockElement:
      case InitializedEntity::EK_LambdaToBlockConversionBlockElement:
      case InitializedEntity::EK_LambdaCapture:
        return false;
  
      case InitializedEntity::EK_Member:
      case InitializedEntity::EK_Binding:
      case InitializedEntity::EK_Variable:
      case InitializedEntity::EK_Parameter:
      case InitializedEntity::EK_Parameter_CF_Audited:
      case InitializedEntity::EK_Temporary:
      case InitializedEntity::EK_ArrayElement:
      case InitializedEntity::EK_Exception:
      case InitializedEntity::EK_CompoundLiteralInit:
      case InitializedEntity::EK_RelatedResult:
        return true;
    }
  
    llvm_unreachable("missed an InitializedEntity kind?");
  }
  
  /// Get the location at which initialization diagnostics should appear.
  static SourceLocation getInitializationLoc(const InitializedEntity &Entity,
                                             Expr *Initializer) {
    switch (Entity.getKind()) {
    case InitializedEntity::EK_Result:
    case InitializedEntity::EK_StmtExprResult:
      return Entity.getReturnLoc();
  
    case InitializedEntity::EK_Exception:
      return Entity.getThrowLoc();
  
    case InitializedEntity::EK_Variable:
    case InitializedEntity::EK_Binding:
      return Entity.getDecl()->getLocation();
  
    case InitializedEntity::EK_LambdaCapture:
      return Entity.getCaptureLoc();
  
    case InitializedEntity::EK_ArrayElement:
    case InitializedEntity::EK_Member:
    case InitializedEntity::EK_Parameter:
    case InitializedEntity::EK_Parameter_CF_Audited:
    case InitializedEntity::EK_Temporary:
    case InitializedEntity::EK_New:
    case InitializedEntity::EK_Base:
    case InitializedEntity::EK_Delegating:
    case InitializedEntity::EK_VectorElement:
    case InitializedEntity::EK_ComplexElement:
    case InitializedEntity::EK_BlockElement:
    case InitializedEntity::EK_LambdaToBlockConversionBlockElement:
    case InitializedEntity::EK_CompoundLiteralInit:
    case InitializedEntity::EK_RelatedResult:
      return Initializer->getBeginLoc();
    }
    llvm_unreachable("missed an InitializedEntity kind?");
  }
  
  /// Make a (potentially elidable) temporary copy of the object
  /// provided by the given initializer by calling the appropriate copy
  /// constructor.
  ///
  /// \param S The Sema object used for type-checking.
  ///
  /// \param T The type of the temporary object, which must either be
  /// the type of the initializer expression or a superclass thereof.
  ///
  /// \param Entity The entity being initialized.
  ///
  /// \param CurInit The initializer expression.
  ///
  /// \param IsExtraneousCopy Whether this is an "extraneous" copy that
  /// is permitted in C++03 (but not C++0x) when binding a reference to
  /// an rvalue.
  ///
  /// \returns An expression that copies the initializer expression into
  /// a temporary object, or an error expression if a copy could not be
  /// created.
  static ExprResult CopyObject(Sema &S,
                               QualType T,
                               const InitializedEntity &Entity,
                               ExprResult CurInit,
                               bool IsExtraneousCopy) {
    if (CurInit.isInvalid())
      return CurInit;
    // Determine which class type we're copying to.
    Expr *CurInitExpr = (Expr *)CurInit.get();
    CXXRecordDecl *Class = nullptr;
    if (const RecordType *Record = T->getAs<RecordType>())
      Class = cast<CXXRecordDecl>(Record->getDecl());
    if (!Class)
      return CurInit;
  
    SourceLocation Loc = getInitializationLoc(Entity, CurInit.get());
  
    // Make sure that the type we are copying is complete.
    if (S.RequireCompleteType(Loc, T, diag::err_temp_copy_incomplete))
      return CurInit;
  
    // Perform overload resolution using the class's constructors. Per
    // C++11 [dcl.init]p16, second bullet for class types, this initialization
    // is direct-initialization.
    OverloadCandidateSet CandidateSet(Loc, OverloadCandidateSet::CSK_Normal);
    DeclContext::lookup_result Ctors = S.LookupConstructors(Class);
  
    OverloadCandidateSet::iterator Best;
    switch (ResolveConstructorOverload(
        S, Loc, CurInitExpr, CandidateSet, T, Ctors, Best,
        /*CopyInitializing=*/false, /*AllowExplicit=*/true,
        /*OnlyListConstructors=*/false, /*IsListInit=*/false,
        /*SecondStepOfCopyInit=*/true)) {
    case OR_Success:
      break;
  
    case OR_No_Viable_Function:
      CandidateSet.NoteCandidates(
          PartialDiagnosticAt(
              Loc, S.PDiag(IsExtraneousCopy && !S.isSFINAEContext()
                               ? diag::ext_rvalue_to_reference_temp_copy_no_viable
                               : diag::err_temp_copy_no_viable)
                       << (int)Entity.getKind() << CurInitExpr->getType()
                       << CurInitExpr->getSourceRange()),
          S, OCD_AllCandidates, CurInitExpr);
      if (!IsExtraneousCopy || S.isSFINAEContext())
        return ExprError();
      return CurInit;
  
    case OR_Ambiguous:
      CandidateSet.NoteCandidates(
          PartialDiagnosticAt(Loc, S.PDiag(diag::err_temp_copy_ambiguous)
                                       << (int)Entity.getKind()
                                       << CurInitExpr->getType()
                                       << CurInitExpr->getSourceRange()),
          S, OCD_AmbiguousCandidates, CurInitExpr);
      return ExprError();
  
    case OR_Deleted:
      S.Diag(Loc, diag::err_temp_copy_deleted)
        << (int)Entity.getKind() << CurInitExpr->getType()
        << CurInitExpr->getSourceRange();
      S.NoteDeletedFunction(Best->Function);
      return ExprError();
    }
  
    bool HadMultipleCandidates = CandidateSet.size() > 1;
  
    CXXConstructorDecl *Constructor = cast<CXXConstructorDecl>(Best->Function);
    SmallVector<Expr*, 8> ConstructorArgs;
    CurInit.get(); // Ownership transferred into MultiExprArg, below.
  
    S.CheckConstructorAccess(Loc, Constructor, Best->FoundDecl, Entity,
                             IsExtraneousCopy);
  
    if (IsExtraneousCopy) {
      // If this is a totally extraneous copy for C++03 reference
      // binding purposes, just return the original initialization
      // expression. We don't generate an (elided) copy operation here
      // because doing so would require us to pass down a flag to avoid
      // infinite recursion, where each step adds another extraneous,
      // elidable copy.
  
      // Instantiate the default arguments of any extra parameters in
      // the selected copy constructor, as if we were going to create a
      // proper call to the copy constructor.
      for (unsigned I = 1, N = Constructor->getNumParams(); I != N; ++I) {
        ParmVarDecl *Parm = Constructor->getParamDecl(I);
        if (S.RequireCompleteType(Loc, Parm->getType(),
                                  diag::err_call_incomplete_argument))
          break;
  
        // Build the default argument expression; we don't actually care
        // if this succeeds or not, because this routine will complain
        // if there was a problem.
        S.BuildCXXDefaultArgExpr(Loc, Constructor, Parm);
      }
  
      return CurInitExpr;
    }
  
    // Determine the arguments required to actually perform the
    // constructor call (we might have derived-to-base conversions, or
    // the copy constructor may have default arguments).
    if (S.CompleteConstructorCall(Constructor, CurInitExpr, Loc, ConstructorArgs))
      return ExprError();
  
    // C++0x [class.copy]p32:
    //   When certain criteria are met, an implementation is allowed to
    //   omit the copy/move construction of a class object, even if the
    //   copy/move constructor and/or destructor for the object have
    //   side effects. [...]
    //     - when a temporary class object that has not been bound to a
    //       reference (12.2) would be copied/moved to a class object
    //       with the same cv-unqualified type, the copy/move operation
    //       can be omitted by constructing the temporary object
    //       directly into the target of the omitted copy/move
    //
    // Note that the other three bullets are handled elsewhere. Copy
    // elision for return statements and throw expressions are handled as part
    // of constructor initialization, while copy elision for exception handlers
    // is handled by the run-time.
    //
    // FIXME: If the function parameter is not the same type as the temporary, we
    // should still be able to elide the copy, but we don't have a way to
    // represent in the AST how much should be elided in this case.
    bool Elidable =
        CurInitExpr->isTemporaryObject(S.Context, Class) &&
        S.Context.hasSameUnqualifiedType(
            Best->Function->getParamDecl(0)->getType().getNonReferenceType(),
            CurInitExpr->getType());
  
    // Actually perform the constructor call.
    CurInit = S.BuildCXXConstructExpr(Loc, T, Best->FoundDecl, Constructor,
                                      Elidable,
                                      ConstructorArgs,
                                      HadMultipleCandidates,
                                      /*ListInit*/ false,
                                      /*StdInitListInit*/ false,
                                      /*ZeroInit*/ false,
                                      CXXConstructExpr::CK_Complete,
                                      SourceRange());
  
    // If we're supposed to bind temporaries, do so.
    if (!CurInit.isInvalid() && shouldBindAsTemporary(Entity))
      CurInit = S.MaybeBindToTemporary(CurInit.getAs<Expr>());
    return CurInit;
  }
  
  /// Check whether elidable copy construction for binding a reference to
  /// a temporary would have succeeded if we were building in C++98 mode, for
  /// -Wc++98-compat.
  static void CheckCXX98CompatAccessibleCopy(Sema &S,
                                             const InitializedEntity &Entity,
                                             Expr *CurInitExpr) {
    assert(S.getLangOpts().CPlusPlus11);
  
    const RecordType *Record = CurInitExpr->getType()->getAs<RecordType>();
    if (!Record)
      return;
  
    SourceLocation Loc = getInitializationLoc(Entity, CurInitExpr);
    if (S.Diags.isIgnored(diag::warn_cxx98_compat_temp_copy, Loc))
      return;
  
    // Find constructors which would have been considered.
    OverloadCandidateSet CandidateSet(Loc, OverloadCandidateSet::CSK_Normal);
    DeclContext::lookup_result Ctors =
        S.LookupConstructors(cast<CXXRecordDecl>(Record->getDecl()));
  
    // Perform overload resolution.
    OverloadCandidateSet::iterator Best;
    OverloadingResult OR = ResolveConstructorOverload(
        S, Loc, CurInitExpr, CandidateSet, CurInitExpr->getType(), Ctors, Best,
        /*CopyInitializing=*/false, /*AllowExplicit=*/true,
        /*OnlyListConstructors=*/false, /*IsListInit=*/false,
        /*SecondStepOfCopyInit=*/true);
  
    PartialDiagnostic Diag = S.PDiag(diag::warn_cxx98_compat_temp_copy)
      << OR << (int)Entity.getKind() << CurInitExpr->getType()
      << CurInitExpr->getSourceRange();
  
    switch (OR) {
    case OR_Success:
      S.CheckConstructorAccess(Loc, cast<CXXConstructorDecl>(Best->Function),
                               Best->FoundDecl, Entity, Diag);
      // FIXME: Check default arguments as far as that's possible.
      break;
  
    case OR_No_Viable_Function:
      CandidateSet.NoteCandidates(PartialDiagnosticAt(Loc, Diag), S,
                                  OCD_AllCandidates, CurInitExpr);
      break;
  
    case OR_Ambiguous:
      CandidateSet.NoteCandidates(PartialDiagnosticAt(Loc, Diag), S,
                                  OCD_AmbiguousCandidates, CurInitExpr);
      break;
  
    case OR_Deleted:
      S.Diag(Loc, Diag);
      S.NoteDeletedFunction(Best->Function);
      break;
    }
  }
  
  void InitializationSequence::PrintInitLocationNote(Sema &S,
                                                const InitializedEntity &Entity) {
    if (Entity.isParameterKind() && Entity.getDecl()) {
      if (Entity.getDecl()->getLocation().isInvalid())
        return;
  
      if (Entity.getDecl()->getDeclName())
        S.Diag(Entity.getDecl()->getLocation(), diag::note_parameter_named_here)
          << Entity.getDecl()->getDeclName();
      else
        S.Diag(Entity.getDecl()->getLocation(), diag::note_parameter_here);
    }
    else if (Entity.getKind() == InitializedEntity::EK_RelatedResult &&
             Entity.getMethodDecl())
      S.Diag(Entity.getMethodDecl()->getLocation(),
             diag::note_method_return_type_change)
        << Entity.getMethodDecl()->getDeclName();
  }
  
  /// Returns true if the parameters describe a constructor initialization of
  /// an explicit temporary object, e.g. "Point(x, y)".
  static bool isExplicitTemporary(const InitializedEntity &Entity,
                                  const InitializationKind &Kind,
                                  unsigned NumArgs) {
    switch (Entity.getKind()) {
    case InitializedEntity::EK_Temporary:
    case InitializedEntity::EK_CompoundLiteralInit:
    case InitializedEntity::EK_RelatedResult:
      break;
    default:
      return false;
    }
  
    switch (Kind.getKind()) {
    case InitializationKind::IK_DirectList:
      return true;
    // FIXME: Hack to work around cast weirdness.
    case InitializationKind::IK_Direct:
    case InitializationKind::IK_Value:
      return NumArgs != 1;
    default:
      return false;
    }
  }
  
  static ExprResult
  PerformConstructorInitialization(Sema &S,
                                   const InitializedEntity &Entity,
                                   const InitializationKind &Kind,
                                   MultiExprArg Args,
                                   const InitializationSequence::Step& Step,
                                   bool &ConstructorInitRequiresZeroInit,
                                   bool IsListInitialization,
                                   bool IsStdInitListInitialization,
                                   SourceLocation LBraceLoc,
                                   SourceLocation RBraceLoc) {
    unsigned NumArgs = Args.size();
    CXXConstructorDecl *Constructor
      = cast<CXXConstructorDecl>(Step.Function.Function);
    bool HadMultipleCandidates = Step.Function.HadMultipleCandidates;
  
    // Build a call to the selected constructor.
    SmallVector<Expr*, 8> ConstructorArgs;
    SourceLocation Loc = (Kind.isCopyInit() && Kind.getEqualLoc().isValid())
                           ? Kind.getEqualLoc()
                           : Kind.getLocation();
  
    if (Kind.getKind() == InitializationKind::IK_Default) {
      // Force even a trivial, implicit default constructor to be
      // semantically checked. We do this explicitly because we don't build
      // the definition for completely trivial constructors.
      assert(Constructor->getParent() && "No parent class for constructor.");
      if (Constructor->isDefaulted() && Constructor->isDefaultConstructor() &&
          Constructor->isTrivial() && !Constructor->isUsed(false)) {
        S.runWithSufficientStackSpace(Loc, [&] {
          S.DefineImplicitDefaultConstructor(Loc, Constructor);
        });
      }
    }
  
    ExprResult CurInit((Expr *)nullptr);
  
    // C++ [over.match.copy]p1:
    //   - When initializing a temporary to be bound to the first parameter
    //     of a constructor that takes a reference to possibly cv-qualified
    //     T as its first argument, called with a single argument in the
    //     context of direct-initialization, explicit conversion functions
    //     are also considered.
    bool AllowExplicitConv =
        Kind.AllowExplicit() && !Kind.isCopyInit() && Args.size() == 1 &&
        hasCopyOrMoveCtorParam(S.Context,
                               getConstructorInfo(Step.Function.FoundDecl));
  
    // Determine the arguments required to actually perform the constructor
    // call.
    if (S.CompleteConstructorCall(Constructor, Args,
                                  Loc, ConstructorArgs,
                                  AllowExplicitConv,
                                  IsListInitialization))
      return ExprError();
  
  
    if (isExplicitTemporary(Entity, Kind, NumArgs)) {
      // An explicitly-constructed temporary, e.g., X(1, 2).
      if (S.DiagnoseUseOfDecl(Constructor, Loc))
        return ExprError();
  
      TypeSourceInfo *TSInfo = Entity.getTypeSourceInfo();
      if (!TSInfo)
        TSInfo = S.Context.getTrivialTypeSourceInfo(Entity.getType(), Loc);
      SourceRange ParenOrBraceRange =
          (Kind.getKind() == InitializationKind::IK_DirectList)
          ? SourceRange(LBraceLoc, RBraceLoc)
          : Kind.getParenOrBraceRange();
  
      if (auto *Shadow = dyn_cast<ConstructorUsingShadowDecl>(
              Step.Function.FoundDecl.getDecl())) {
        Constructor = S.findInheritingConstructor(Loc, Constructor, Shadow);
        if (S.DiagnoseUseOfDecl(Constructor, Loc))
          return ExprError();
      }
      S.MarkFunctionReferenced(Loc, Constructor);
  
      CurInit = S.CheckForImmediateInvocation(
          CXXTemporaryObjectExpr::Create(
              S.Context, Constructor,
              Entity.getType().getNonLValueExprType(S.Context), TSInfo,
              ConstructorArgs, ParenOrBraceRange, HadMultipleCandidates,
              IsListInitialization, IsStdInitListInitialization,
              ConstructorInitRequiresZeroInit),
          Constructor);
    } else {
      CXXConstructExpr::ConstructionKind ConstructKind =
        CXXConstructExpr::CK_Complete;
  
      if (Entity.getKind() == InitializedEntity::EK_Base) {
        ConstructKind = Entity.getBaseSpecifier()->isVirtual() ?
          CXXConstructExpr::CK_VirtualBase :
          CXXConstructExpr::CK_NonVirtualBase;
      } else if (Entity.getKind() == InitializedEntity::EK_Delegating) {
        ConstructKind = CXXConstructExpr::CK_Delegating;
      }
  
      // Only get the parenthesis or brace range if it is a list initialization or
      // direct construction.
      SourceRange ParenOrBraceRange;
      if (IsListInitialization)
        ParenOrBraceRange = SourceRange(LBraceLoc, RBraceLoc);
      else if (Kind.getKind() == InitializationKind::IK_Direct)
        ParenOrBraceRange = Kind.getParenOrBraceRange();
  
      // If the entity allows NRVO, mark the construction as elidable
      // unconditionally.
      if (Entity.allowsNRVO())
        CurInit = S.BuildCXXConstructExpr(Loc, Step.Type,
                                          Step.Function.FoundDecl,
                                          Constructor, /*Elidable=*/true,
                                          ConstructorArgs,
                                          HadMultipleCandidates,
                                          IsListInitialization,
                                          IsStdInitListInitialization,
                                          ConstructorInitRequiresZeroInit,
                                          ConstructKind,
                                          ParenOrBraceRange);
      else
        CurInit = S.BuildCXXConstructExpr(Loc, Step.Type,
                                          Step.Function.FoundDecl,
                                          Constructor,
                                          ConstructorArgs,
                                          HadMultipleCandidates,
                                          IsListInitialization,
                                          IsStdInitListInitialization,
                                          ConstructorInitRequiresZeroInit,
                                          ConstructKind,
                                          ParenOrBraceRange);
    }
    if (CurInit.isInvalid())
      return ExprError();
  
    // Only check access if all of that succeeded.
    S.CheckConstructorAccess(Loc, Constructor, Step.Function.FoundDecl, Entity);
    if (S.DiagnoseUseOfDecl(Step.Function.FoundDecl, Loc))
      return ExprError();
  
    if (const ArrayType *AT = S.Context.getAsArrayType(Entity.getType()))
      if (checkDestructorReference(S.Context.getBaseElementType(AT), Loc, S))
        return ExprError();
  
    if (shouldBindAsTemporary(Entity))
      CurInit = S.MaybeBindToTemporary(CurInit.get());
  
    return CurInit;
  }
  
  namespace {
  enum LifetimeKind {
    /// The lifetime of a temporary bound to this entity ends at the end of the
    /// full-expression, and that's (probably) fine.
    LK_FullExpression,
  
    /// The lifetime of a temporary bound to this entity is extended to the
    /// lifeitme of the entity itself.
    LK_Extended,
  
    /// The lifetime of a temporary bound to this entity probably ends too soon,
    /// because the entity is allocated in a new-expression.
    LK_New,
  
    /// The lifetime of a temporary bound to this entity ends too soon, because
    /// the entity is a return object.
    LK_Return,
  
    /// The lifetime of a temporary bound to this entity ends too soon, because
    /// the entity is the result of a statement expression.
    LK_StmtExprResult,
  
    /// This is a mem-initializer: if it would extend a temporary (other than via
    /// a default member initializer), the program is ill-formed.
    LK_MemInitializer,
  };
  using LifetimeResult =
      llvm::PointerIntPair<const InitializedEntity *, 3, LifetimeKind>;
  }
  
  /// Determine the declaration which an initialized entity ultimately refers to,
  /// for the purpose of lifetime-extending a temporary bound to a reference in
  /// the initialization of \p Entity.
  static LifetimeResult getEntityLifetime(
      const InitializedEntity *Entity,
      const InitializedEntity *InitField = nullptr) {
    // C++11 [class.temporary]p5:
    switch (Entity->getKind()) {
    case InitializedEntity::EK_Variable:
      //   The temporary [...] persists for the lifetime of the reference
      return {Entity, LK_Extended};
  
    case InitializedEntity::EK_Member:
      // For subobjects, we look at the complete object.
      if (Entity->getParent())
        return getEntityLifetime(Entity->getParent(), Entity);
  
      //   except:
      // C++17 [class.base.init]p8:
      //   A temporary expression bound to a reference member in a
      //   mem-initializer is ill-formed.
      // C++17 [class.base.init]p11:
      //   A temporary expression bound to a reference member from a
      //   default member initializer is ill-formed.
      //
      // The context of p11 and its example suggest that it's only the use of a
      // default member initializer from a constructor that makes the program
      // ill-formed, not its mere existence, and that it can even be used by
      // aggregate initialization.
      return {Entity, Entity->isDefaultMemberInitializer() ? LK_Extended
                                                           : LK_MemInitializer};
  
    case InitializedEntity::EK_Binding:
      // Per [dcl.decomp]p3, the binding is treated as a variable of reference
      // type.
      return {Entity, LK_Extended};
  
    case InitializedEntity::EK_Parameter:
    case InitializedEntity::EK_Parameter_CF_Audited:
      //   -- A temporary bound to a reference parameter in a function call
      //      persists until the completion of the full-expression containing
      //      the call.
      return {nullptr, LK_FullExpression};
  
    case InitializedEntity::EK_Result:
      //   -- The lifetime of a temporary bound to the returned value in a
      //      function return statement is not extended; the temporary is
      //      destroyed at the end of the full-expression in the return statement.
      return {nullptr, LK_Return};
  
    case InitializedEntity::EK_StmtExprResult:
      // FIXME: Should we lifetime-extend through the result of a statement
      // expression?
      return {nullptr, LK_StmtExprResult};
  
    case InitializedEntity::EK_New:
      //   -- A temporary bound to a reference in a new-initializer persists
      //      until the completion of the full-expression containing the
      //      new-initializer.
      return {nullptr, LK_New};
  
    case InitializedEntity::EK_Temporary:
    case InitializedEntity::EK_CompoundLiteralInit:
    case InitializedEntity::EK_RelatedResult:
      // We don't yet know the storage duration of the surrounding temporary.
      // Assume it's got full-expression duration for now, it will patch up our
      // storage duration if that's not correct.
      return {nullptr, LK_FullExpression};
  
    case InitializedEntity::EK_ArrayElement:
      // For subobjects, we look at the complete object.
      return getEntityLifetime(Entity->getParent(), InitField);
  
    case InitializedEntity::EK_Base:
      // For subobjects, we look at the complete object.
      if (Entity->getParent())
        return getEntityLifetime(Entity->getParent(), InitField);
      return {InitField, LK_MemInitializer};
  
    case InitializedEntity::EK_Delegating:
      // We can reach this case for aggregate initialization in a constructor:
      //   struct A { int &&r; };
      //   struct B : A { B() : A{0} {} };
      // In this case, use the outermost field decl as the context.
      return {InitField, LK_MemInitializer};
  
    case InitializedEntity::EK_BlockElement:
    case InitializedEntity::EK_LambdaToBlockConversionBlockElement:
    case InitializedEntity::EK_LambdaCapture:
    case InitializedEntity::EK_VectorElement:
    case InitializedEntity::EK_ComplexElement:
      return {nullptr, LK_FullExpression};
  
    case InitializedEntity::EK_Exception:
      // FIXME: Can we diagnose lifetime problems with exceptions?
      return {nullptr, LK_FullExpression};
    }
    llvm_unreachable("unknown entity kind");
  }
  
  namespace {
  enum ReferenceKind {
    /// Lifetime would be extended by a reference binding to a temporary.
    RK_ReferenceBinding,
    /// Lifetime would be extended by a std::initializer_list object binding to
    /// its backing array.
    RK_StdInitializerList,
  };
  
  /// A temporary or local variable. This will be one of:
  ///  * A MaterializeTemporaryExpr.
  ///  * A DeclRefExpr whose declaration is a local.
  ///  * An AddrLabelExpr.
  ///  * A BlockExpr for a block with captures.
  using Local = Expr*;
  
  /// Expressions we stepped over when looking for the local state. Any steps
  /// that would inhibit lifetime extension or take us out of subexpressions of
  /// the initializer are included.
  struct IndirectLocalPathEntry {
    enum EntryKind {
      DefaultInit,
      AddressOf,
      VarInit,
      LValToRVal,
      LifetimeBoundCall,
      GslReferenceInit,
      GslPointerInit
    } Kind;
    Expr *E;
    const Decl *D = nullptr;
    IndirectLocalPathEntry() {}
    IndirectLocalPathEntry(EntryKind K, Expr *E) : Kind(K), E(E) {}
    IndirectLocalPathEntry(EntryKind K, Expr *E, const Decl *D)
        : Kind(K), E(E), D(D) {}
  };
  
  using IndirectLocalPath = llvm::SmallVectorImpl<IndirectLocalPathEntry>;
  
  struct RevertToOldSizeRAII {
    IndirectLocalPath &Path;
    unsigned OldSize = Path.size();
    RevertToOldSizeRAII(IndirectLocalPath &Path) : Path(Path) {}
    ~RevertToOldSizeRAII() { Path.resize(OldSize); }
  };
  
  using LocalVisitor = llvm::function_ref<bool(IndirectLocalPath &Path, Local L,
                                               ReferenceKind RK)>;
  }
  
  static bool isVarOnPath(IndirectLocalPath &Path, VarDecl *VD) {
    for (auto E : Path)
      if (E.Kind == IndirectLocalPathEntry::VarInit && E.D == VD)
        return true;
    return false;
  }
  
  static bool pathContainsInit(IndirectLocalPath &Path) {
    return llvm::any_of(Path, [=](IndirectLocalPathEntry E) {
      return E.Kind == IndirectLocalPathEntry::DefaultInit ||
             E.Kind == IndirectLocalPathEntry::VarInit;
    });
  }
  
  static void visitLocalsRetainedByInitializer(IndirectLocalPath &Path,
                                               Expr *Init, LocalVisitor Visit,
                                               bool RevisitSubinits,
                                               bool EnableLifetimeWarnings);
  
  static void visitLocalsRetainedByReferenceBinding(IndirectLocalPath &Path,
                                                    Expr *Init, ReferenceKind RK,
                                                    LocalVisitor Visit,
                                                    bool EnableLifetimeWarnings);
  
  template <typename T> static bool isRecordWithAttr(QualType Type) {
    if (auto *RD = Type->getAsCXXRecordDecl())
      return RD->hasAttr<T>();
    return false;
  }
  
  // Decl::isInStdNamespace will return false for iterators in some STL
  // implementations due to them being defined in a namespace outside of the std
  // namespace.
  static bool isInStlNamespace(const Decl *D) {
    const DeclContext *DC = D->getDeclContext();
    if (!DC)
      return false;
    if (const auto *ND = dyn_cast<NamespaceDecl>(DC))
      if (const IdentifierInfo *II = ND->getIdentifier()) {
        StringRef Name = II->getName();
        if (Name.size() >= 2 && Name.front() == '_' &&
            (Name[1] == '_' || isUppercase(Name[1])))
          return true;
      }
  
    return DC->isStdNamespace();
  }
  
  static bool shouldTrackImplicitObjectArg(const CXXMethodDecl *Callee) {
    if (auto *Conv = dyn_cast_or_null<CXXConversionDecl>(Callee))
      if (isRecordWithAttr<PointerAttr>(Conv->getConversionType()))
        return true;
    if (!isInStlNamespace(Callee->getParent()))
      return false;
    if (!isRecordWithAttr<PointerAttr>(Callee->getThisObjectType()) &&
        !isRecordWithAttr<OwnerAttr>(Callee->getThisObjectType()))
      return false;
    if (Callee->getReturnType()->isPointerType() ||
        isRecordWithAttr<PointerAttr>(Callee->getReturnType())) {
      if (!Callee->getIdentifier())
        return false;
      return llvm::StringSwitch<bool>(Callee->getName())
          .Cases("begin", "rbegin", "cbegin", "crbegin", true)
          .Cases("end", "rend", "cend", "crend", true)
          .Cases("c_str", "data", "get", true)
          // Map and set types.
          .Cases("find", "equal_range", "lower_bound", "upper_bound", true)
          .Default(false);
    } else if (Callee->getReturnType()->isReferenceType()) {
      if (!Callee->getIdentifier()) {
        auto OO = Callee->getOverloadedOperator();
        return OO == OverloadedOperatorKind::OO_Subscript ||
               OO == OverloadedOperatorKind::OO_Star;
      }
      return llvm::StringSwitch<bool>(Callee->getName())
          .Cases("front", "back", "at", "top", "value", true)
          .Default(false);
    }
    return false;
  }
  
  static bool shouldTrackFirstArgument(const FunctionDecl *FD) {
    if (!FD->getIdentifier() || FD->getNumParams() != 1)
      return false;
    const auto *RD = FD->getParamDecl(0)->getType()->getPointeeCXXRecordDecl();
    if (!FD->isInStdNamespace() || !RD || !RD->isInStdNamespace())
      return false;
    if (!isRecordWithAttr<PointerAttr>(QualType(RD->getTypeForDecl(), 0)) &&
        !isRecordWithAttr<OwnerAttr>(QualType(RD->getTypeForDecl(), 0)))
      return false;
    if (FD->getReturnType()->isPointerType() ||
        isRecordWithAttr<PointerAttr>(FD->getReturnType())) {
      return llvm::StringSwitch<bool>(FD->getName())
          .Cases("begin", "rbegin", "cbegin", "crbegin", true)
          .Cases("end", "rend", "cend", "crend", true)
          .Case("data", true)
          .Default(false);
    } else if (FD->getReturnType()->isReferenceType()) {
      return llvm::StringSwitch<bool>(FD->getName())
          .Cases("get", "any_cast", true)
          .Default(false);
    }
    return false;
  }
  
  static void handleGslAnnotatedTypes(IndirectLocalPath &Path, Expr *Call,
                                      LocalVisitor Visit) {
    auto VisitPointerArg = [&](const Decl *D, Expr *Arg, bool Value) {
      // We are not interested in the temporary base objects of gsl Pointers:
      //   Temp().ptr; // Here ptr might not dangle.
      if (isa<MemberExpr>(Arg->IgnoreImpCasts()))
        return;
      // Once we initialized a value with a reference, it can no longer dangle.
      if (!Value) {
        for (auto It = Path.rbegin(), End = Path.rend(); It != End; ++It) {
          if (It->Kind == IndirectLocalPathEntry::GslReferenceInit)
            continue;
          if (It->Kind == IndirectLocalPathEntry::GslPointerInit)
            return;
          break;
        }
      }
      Path.push_back({Value ? IndirectLocalPathEntry::GslPointerInit
                            : IndirectLocalPathEntry::GslReferenceInit,
                      Arg, D});
      if (Arg->isGLValue())
        visitLocalsRetainedByReferenceBinding(Path, Arg, RK_ReferenceBinding,
                                              Visit,
                                              /*EnableLifetimeWarnings=*/true);
      else
        visitLocalsRetainedByInitializer(Path, Arg, Visit, true,
                                         /*EnableLifetimeWarnings=*/true);
      Path.pop_back();
    };
  
    if (auto *MCE = dyn_cast<CXXMemberCallExpr>(Call)) {
      const auto *MD = cast_or_null<CXXMethodDecl>(MCE->getDirectCallee());
      if (MD && shouldTrackImplicitObjectArg(MD))
        VisitPointerArg(MD, MCE->getImplicitObjectArgument(),
                        !MD->getReturnType()->isReferenceType());
      return;
    } else if (auto *OCE = dyn_cast<CXXOperatorCallExpr>(Call)) {
      FunctionDecl *Callee = OCE->getDirectCallee();
      if (Callee && Callee->isCXXInstanceMember() &&
          shouldTrackImplicitObjectArg(cast<CXXMethodDecl>(Callee)))
        VisitPointerArg(Callee, OCE->getArg(0),
                        !Callee->getReturnType()->isReferenceType());
      return;
    } else if (auto *CE = dyn_cast<CallExpr>(Call)) {
      FunctionDecl *Callee = CE->getDirectCallee();
      if (Callee && shouldTrackFirstArgument(Callee))
        VisitPointerArg(Callee, CE->getArg(0),
                        !Callee->getReturnType()->isReferenceType());
      return;
    }
  
    if (auto *CCE = dyn_cast<CXXConstructExpr>(Call)) {
      const auto *Ctor = CCE->getConstructor();
      const CXXRecordDecl *RD = Ctor->getParent();
      if (CCE->getNumArgs() > 0 && RD->hasAttr<PointerAttr>())
        VisitPointerArg(Ctor->getParamDecl(0), CCE->getArgs()[0], true);
    }
  }
  
  static bool implicitObjectParamIsLifetimeBound(const FunctionDecl *FD) {
    const TypeSourceInfo *TSI = FD->getTypeSourceInfo();
    if (!TSI)
      return false;
    // Don't declare this variable in the second operand of the for-statement;
    // GCC miscompiles that by ending its lifetime before evaluating the
    // third operand. See gcc.gnu.org/PR86769.
    AttributedTypeLoc ATL;
    for (TypeLoc TL = TSI->getTypeLoc();
         (ATL = TL.getAsAdjusted<AttributedTypeLoc>());
         TL = ATL.getModifiedLoc()) {
      if (ATL.getAttrAs<LifetimeBoundAttr>())
        return true;
    }
    return false;
  }
  
  static void visitLifetimeBoundArguments(IndirectLocalPath &Path, Expr *Call,
                                          LocalVisitor Visit) {
    const FunctionDecl *Callee;
    ArrayRef<Expr*> Args;
  
    if (auto *CE = dyn_cast<CallExpr>(Call)) {
      Callee = CE->getDirectCallee();
      Args = llvm::makeArrayRef(CE->getArgs(), CE->getNumArgs());
    } else {
      auto *CCE = cast<CXXConstructExpr>(Call);
      Callee = CCE->getConstructor();
      Args = llvm::makeArrayRef(CCE->getArgs(), CCE->getNumArgs());
    }
    if (!Callee)
      return;
  
    Expr *ObjectArg = nullptr;
    if (isa<CXXOperatorCallExpr>(Call) && Callee->isCXXInstanceMember()) {
      ObjectArg = Args[0];
      Args = Args.slice(1);
    } else if (auto *MCE = dyn_cast<CXXMemberCallExpr>(Call)) {
      ObjectArg = MCE->getImplicitObjectArgument();
    }
  
    auto VisitLifetimeBoundArg = [&](const Decl *D, Expr *Arg) {
      Path.push_back({IndirectLocalPathEntry::LifetimeBoundCall, Arg, D});
      if (Arg->isGLValue())
        visitLocalsRetainedByReferenceBinding(Path, Arg, RK_ReferenceBinding,
                                              Visit,
                                              /*EnableLifetimeWarnings=*/false);
      else
        visitLocalsRetainedByInitializer(Path, Arg, Visit, true,
                                         /*EnableLifetimeWarnings=*/false);
      Path.pop_back();
    };
  
    if (ObjectArg && implicitObjectParamIsLifetimeBound(Callee))
      VisitLifetimeBoundArg(Callee, ObjectArg);
  
    for (unsigned I = 0,
                  N = std::min<unsigned>(Callee->getNumParams(), Args.size());
         I != N; ++I) {
      if (Callee->getParamDecl(I)->hasAttr<LifetimeBoundAttr>())
        VisitLifetimeBoundArg(Callee->getParamDecl(I), Args[I]);
    }
  }
  
  /// Visit the locals that would be reachable through a reference bound to the
  /// glvalue expression \c Init.
  static void visitLocalsRetainedByReferenceBinding(IndirectLocalPath &Path,
                                                    Expr *Init, ReferenceKind RK,
                                                    LocalVisitor Visit,
                                                    bool EnableLifetimeWarnings) {
    RevertToOldSizeRAII RAII(Path);
  
    // Walk past any constructs which we can lifetime-extend across.
    Expr *Old;
    do {
      Old = Init;
  
      if (auto *FE = dyn_cast<FullExpr>(Init))
        Init = FE->getSubExpr();
  
      if (InitListExpr *ILE = dyn_cast<InitListExpr>(Init)) {
        // If this is just redundant braces around an initializer, step over it.
        if (ILE->isTransparent())
          Init = ILE->getInit(0);
      }
  
      // Step over any subobject adjustments; we may have a materialized
      // temporary inside them.
      Init = const_cast<Expr *>(Init->skipRValueSubobjectAdjustments());
  
      // Per current approach for DR1376, look through casts to reference type
      // when performing lifetime extension.
      if (CastExpr *CE = dyn_cast<CastExpr>(Init))
        if (CE->getSubExpr()->isGLValue())
          Init = CE->getSubExpr();
  
      // Per the current approach for DR1299, look through array element access
      // on array glvalues when performing lifetime extension.
      if (auto *ASE = dyn_cast<ArraySubscriptExpr>(Init)) {
        Init = ASE->getBase();
        auto *ICE = dyn_cast<ImplicitCastExpr>(Init);
        if (ICE && ICE->getCastKind() == CK_ArrayToPointerDecay)
          Init = ICE->getSubExpr();
        else
          // We can't lifetime extend through this but we might still find some
          // retained temporaries.
          return visitLocalsRetainedByInitializer(Path, Init, Visit, true,
                                                  EnableLifetimeWarnings);
      }
  
      // Step into CXXDefaultInitExprs so we can diagnose cases where a
      // constructor inherits one as an implicit mem-initializer.
      if (auto *DIE = dyn_cast<CXXDefaultInitExpr>(Init)) {
        Path.push_back(
            {IndirectLocalPathEntry::DefaultInit, DIE, DIE->getField()});
        Init = DIE->getExpr();
      }
    } while (Init != Old);
  
    if (auto *MTE = dyn_cast<MaterializeTemporaryExpr>(Init)) {
      if (Visit(Path, Local(MTE), RK))
        visitLocalsRetainedByInitializer(Path, MTE->getSubExpr(), Visit, true,
                                         EnableLifetimeWarnings);
    }
  
    if (isa<CallExpr>(Init)) {
      if (EnableLifetimeWarnings)
        handleGslAnnotatedTypes(Path, Init, Visit);
      return visitLifetimeBoundArguments(Path, Init, Visit);
    }
  
    switch (Init->getStmtClass()) {
    case Stmt::DeclRefExprClass: {
      // If we find the name of a local non-reference parameter, we could have a
      // lifetime problem.
      auto *DRE = cast<DeclRefExpr>(Init);
      auto *VD = dyn_cast<VarDecl>(DRE->getDecl());
      if (VD && VD->hasLocalStorage() &&
          !DRE->refersToEnclosingVariableOrCapture()) {
        if (!VD->getType()->isReferenceType()) {
          Visit(Path, Local(DRE), RK);
        } else if (isa<ParmVarDecl>(DRE->getDecl())) {
          // The lifetime of a reference parameter is unknown; assume it's OK
          // for now.
          break;
        } else if (VD->getInit() && !isVarOnPath(Path, VD)) {
          Path.push_back({IndirectLocalPathEntry::VarInit, DRE, VD});
          visitLocalsRetainedByReferenceBinding(Path, VD->getInit(),
                                                RK_ReferenceBinding, Visit,
                                                EnableLifetimeWarnings);
        }
      }
      break;
    }
  
    case Stmt::UnaryOperatorClass: {
      // The only unary operator that make sense to handle here
      // is Deref.  All others don't resolve to a "name."  This includes
      // handling all sorts of rvalues passed to a unary operator.
      const UnaryOperator *U = cast<UnaryOperator>(Init);
      if (U->getOpcode() == UO_Deref)
        visitLocalsRetainedByInitializer(Path, U->getSubExpr(), Visit, true,
                                         EnableLifetimeWarnings);
      break;
    }
  
    case Stmt::OMPArraySectionExprClass: {
      visitLocalsRetainedByInitializer(Path,
                                       cast<OMPArraySectionExpr>(Init)->getBase(),
                                       Visit, true, EnableLifetimeWarnings);
      break;
    }
  
    case Stmt::ConditionalOperatorClass:
    case Stmt::BinaryConditionalOperatorClass: {
      auto *C = cast<AbstractConditionalOperator>(Init);
      if (!C->getTrueExpr()->getType()->isVoidType())
        visitLocalsRetainedByReferenceBinding(Path, C->getTrueExpr(), RK, Visit,
                                              EnableLifetimeWarnings);
      if (!C->getFalseExpr()->getType()->isVoidType())
        visitLocalsRetainedByReferenceBinding(Path, C->getFalseExpr(), RK, Visit,
                                              EnableLifetimeWarnings);
      break;
    }
  
    // FIXME: Visit the left-hand side of an -> or ->*.
  
    default:
      break;
    }
  }
  
  /// Visit the locals that would be reachable through an object initialized by
  /// the prvalue expression \c Init.
  static void visitLocalsRetainedByInitializer(IndirectLocalPath &Path,
                                               Expr *Init, LocalVisitor Visit,
                                               bool RevisitSubinits,
                                               bool EnableLifetimeWarnings) {
    RevertToOldSizeRAII RAII(Path);
  
    Expr *Old;
    do {
      Old = Init;
  
      // Step into CXXDefaultInitExprs so we can diagnose cases where a
      // constructor inherits one as an implicit mem-initializer.
      if (auto *DIE = dyn_cast<CXXDefaultInitExpr>(Init)) {
        Path.push_back({IndirectLocalPathEntry::DefaultInit, DIE, DIE->getField()});
        Init = DIE->getExpr();
      }
  
      if (auto *FE = dyn_cast<FullExpr>(Init))
        Init = FE->getSubExpr();
  
      // Dig out the expression which constructs the extended temporary.
      Init = const_cast<Expr *>(Init->skipRValueSubobjectAdjustments());
  
      if (CXXBindTemporaryExpr *BTE = dyn_cast<CXXBindTemporaryExpr>(Init))
        Init = BTE->getSubExpr();
  
      Init = Init->IgnoreParens();
  
      // Step over value-preserving rvalue casts.
      if (auto *CE = dyn_cast<CastExpr>(Init)) {
        switch (CE->getCastKind()) {
        case CK_LValueToRValue:
          // If we can match the lvalue to a const object, we can look at its
          // initializer.
          Path.push_back({IndirectLocalPathEntry::LValToRVal, CE});
          return visitLocalsRetainedByReferenceBinding(
              Path, Init, RK_ReferenceBinding,
              [&](IndirectLocalPath &Path, Local L, ReferenceKind RK) -> bool {
            if (auto *DRE = dyn_cast<DeclRefExpr>(L)) {
              auto *VD = dyn_cast<VarDecl>(DRE->getDecl());
              if (VD && VD->getType().isConstQualified() && VD->getInit() &&
                  !isVarOnPath(Path, VD)) {
                Path.push_back({IndirectLocalPathEntry::VarInit, DRE, VD});
                visitLocalsRetainedByInitializer(Path, VD->getInit(), Visit, true,
                                                 EnableLifetimeWarnings);
              }
            } else if (auto *MTE = dyn_cast<MaterializeTemporaryExpr>(L)) {
              if (MTE->getType().isConstQualified())
                visitLocalsRetainedByInitializer(Path, MTE->getSubExpr(), Visit,
                                                 true, EnableLifetimeWarnings);
            }
            return false;
          }, EnableLifetimeWarnings);
  
          // We assume that objects can be retained by pointers cast to integers,
          // but not if the integer is cast to floating-point type or to _Complex.
          // We assume that casts to 'bool' do not preserve enough information to
          // retain a local object.
        case CK_NoOp:
        case CK_BitCast:
        case CK_BaseToDerived:
        case CK_DerivedToBase:
        case CK_UncheckedDerivedToBase:
        case CK_Dynamic:
        case CK_ToUnion:
        case CK_UserDefinedConversion:
        case CK_ConstructorConversion:
        case CK_IntegralToPointer:
        case CK_PointerToIntegral:
        case CK_VectorSplat:
        case CK_IntegralCast:
        case CK_CPointerToObjCPointerCast:
        case CK_BlockPointerToObjCPointerCast:
        case CK_AnyPointerToBlockPointerCast:
        case CK_AddressSpaceConversion:
          break;
  
        case CK_ArrayToPointerDecay:
          // Model array-to-pointer decay as taking the address of the array
          // lvalue.
          Path.push_back({IndirectLocalPathEntry::AddressOf, CE});
          return visitLocalsRetainedByReferenceBinding(Path, CE->getSubExpr(),
                                                       RK_ReferenceBinding, Visit,
                                                       EnableLifetimeWarnings);
  
        default:
          return;
        }
  
        Init = CE->getSubExpr();
      }
    } while (Old != Init);
  
    // C++17 [dcl.init.list]p6:
    //   initializing an initializer_list object from the array extends the
    //   lifetime of the array exactly like binding a reference to a temporary.
    if (auto *ILE = dyn_cast<CXXStdInitializerListExpr>(Init))
      return visitLocalsRetainedByReferenceBinding(Path, ILE->getSubExpr(),
                                                   RK_StdInitializerList, Visit,
                                                   EnableLifetimeWarnings);
  
    if (InitListExpr *ILE = dyn_cast<InitListExpr>(Init)) {
      // We already visited the elements of this initializer list while
      // performing the initialization. Don't visit them again unless we've
      // changed the lifetime of the initialized entity.
      if (!RevisitSubinits)
        return;
  
      if (ILE->isTransparent())
        return visitLocalsRetainedByInitializer(Path, ILE->getInit(0), Visit,
                                                RevisitSubinits,
                                                EnableLifetimeWarnings);
  
      if (ILE->getType()->isArrayType()) {
        for (unsigned I = 0, N = ILE->getNumInits(); I != N; ++I)
          visitLocalsRetainedByInitializer(Path, ILE->getInit(I), Visit,
                                           RevisitSubinits,
                                           EnableLifetimeWarnings);
        return;
      }
  
      if (CXXRecordDecl *RD = ILE->getType()->getAsCXXRecordDecl()) {
        assert(RD->isAggregate() && "aggregate init on non-aggregate");
  
        // If we lifetime-extend a braced initializer which is initializing an
        // aggregate, and that aggregate contains reference members which are
        // bound to temporaries, those temporaries are also lifetime-extended.
        if (RD->isUnion() && ILE->getInitializedFieldInUnion() &&
            ILE->getInitializedFieldInUnion()->getType()->isReferenceType())
          visitLocalsRetainedByReferenceBinding(Path, ILE->getInit(0),
                                                RK_ReferenceBinding, Visit,
                                                EnableLifetimeWarnings);
        else {
          unsigned Index = 0;
          for (; Index < RD->getNumBases() && Index < ILE->getNumInits(); ++Index)
            visitLocalsRetainedByInitializer(Path, ILE->getInit(Index), Visit,
                                             RevisitSubinits,
                                             EnableLifetimeWarnings);
          for (const auto *I : RD->fields()) {
            if (Index >= ILE->getNumInits())
              break;
            if (I->isUnnamedBitfield())
              continue;
            Expr *SubInit = ILE->getInit(Index);
            if (I->getType()->isReferenceType())
              visitLocalsRetainedByReferenceBinding(Path, SubInit,
                                                    RK_ReferenceBinding, Visit,
                                                    EnableLifetimeWarnings);
            else
              // This might be either aggregate-initialization of a member or
              // initialization of a std::initializer_list object. Regardless,
              // we should recursively lifetime-extend that initializer.
              visitLocalsRetainedByInitializer(Path, SubInit, Visit,
                                               RevisitSubinits,
                                               EnableLifetimeWarnings);
            ++Index;
          }
        }
      }
      return;
    }
  
    // The lifetime of an init-capture is that of the closure object constructed
    // by a lambda-expression.
    if (auto *LE = dyn_cast<LambdaExpr>(Init)) {
      for (Expr *E : LE->capture_inits()) {
        if (!E)
          continue;
        if (E->isGLValue())
          visitLocalsRetainedByReferenceBinding(Path, E, RK_ReferenceBinding,
                                                Visit, EnableLifetimeWarnings);
        else
          visitLocalsRetainedByInitializer(Path, E, Visit, true,
                                           EnableLifetimeWarnings);
      }
    }
  
    if (isa<CallExpr>(Init) || isa<CXXConstructExpr>(Init)) {
      if (EnableLifetimeWarnings)
        handleGslAnnotatedTypes(Path, Init, Visit);
      return visitLifetimeBoundArguments(Path, Init, Visit);
    }
  
    switch (Init->getStmtClass()) {
    case Stmt::UnaryOperatorClass: {
      auto *UO = cast<UnaryOperator>(Init);
      // If the initializer is the address of a local, we could have a lifetime
      // problem.
      if (UO->getOpcode() == UO_AddrOf) {
        // If this is &rvalue, then it's ill-formed and we have already diagnosed
        // it. Don't produce a redundant warning about the lifetime of the
        // temporary.
        if (isa<MaterializeTemporaryExpr>(UO->getSubExpr()))
          return;
  
        Path.push_back({IndirectLocalPathEntry::AddressOf, UO});
        visitLocalsRetainedByReferenceBinding(Path, UO->getSubExpr(),
                                              RK_ReferenceBinding, Visit,
                                              EnableLifetimeWarnings);
      }
      break;
    }
  
    case Stmt::BinaryOperatorClass: {
      // Handle pointer arithmetic.
      auto *BO = cast<BinaryOperator>(Init);
      BinaryOperatorKind BOK = BO->getOpcode();
      if (!BO->getType()->isPointerType() || (BOK != BO_Add && BOK != BO_Sub))
        break;
  
      if (BO->getLHS()->getType()->isPointerType())
        visitLocalsRetainedByInitializer(Path, BO->getLHS(), Visit, true,
                                         EnableLifetimeWarnings);
      else if (BO->getRHS()->getType()->isPointerType())
        visitLocalsRetainedByInitializer(Path, BO->getRHS(), Visit, true,
                                         EnableLifetimeWarnings);
      break;
    }
  
    case Stmt::ConditionalOperatorClass:
    case Stmt::BinaryConditionalOperatorClass: {
      auto *C = cast<AbstractConditionalOperator>(Init);
      // In C++, we can have a throw-expression operand, which has 'void' type
      // and isn't interesting from a lifetime perspective.
      if (!C->getTrueExpr()->getType()->isVoidType())
        visitLocalsRetainedByInitializer(Path, C->getTrueExpr(), Visit, true,
                                         EnableLifetimeWarnings);
      if (!C->getFalseExpr()->getType()->isVoidType())
        visitLocalsRetainedByInitializer(Path, C->getFalseExpr(), Visit, true,
                                         EnableLifetimeWarnings);
      break;
    }
  
    case Stmt::BlockExprClass:
      if (cast<BlockExpr>(Init)->getBlockDecl()->hasCaptures()) {
        // This is a local block, whose lifetime is that of the function.
        Visit(Path, Local(cast<BlockExpr>(Init)), RK_ReferenceBinding);
      }
      break;
  
    case Stmt::AddrLabelExprClass:
      // We want to warn if the address of a label would escape the function.
      Visit(Path, Local(cast<AddrLabelExpr>(Init)), RK_ReferenceBinding);
      break;
  
    default:
      break;
    }
  }
  
  /// Determine whether this is an indirect path to a temporary that we are
  /// supposed to lifetime-extend along (but don't).
  static bool shouldLifetimeExtendThroughPath(const IndirectLocalPath &Path) {
    for (auto Elem : Path) {
      if (Elem.Kind != IndirectLocalPathEntry::DefaultInit)
        return false;
    }
    return true;
  }
  
  /// Find the range for the first interesting entry in the path at or after I.
  static SourceRange nextPathEntryRange(const IndirectLocalPath &Path, unsigned I,
                                        Expr *E) {
    for (unsigned N = Path.size(); I != N; ++I) {
      switch (Path[I].Kind) {
      case IndirectLocalPathEntry::AddressOf:
      case IndirectLocalPathEntry::LValToRVal:
      case IndirectLocalPathEntry::LifetimeBoundCall:
      case IndirectLocalPathEntry::GslReferenceInit:
      case IndirectLocalPathEntry::GslPointerInit:
        // These exist primarily to mark the path as not permitting or
        // supporting lifetime extension.
        break;
  
      case IndirectLocalPathEntry::VarInit:
        if (cast<VarDecl>(Path[I].D)->isImplicit())
          return SourceRange();
        LLVM_FALLTHROUGH;
      case IndirectLocalPathEntry::DefaultInit:
        return Path[I].E->getSourceRange();
      }
    }
    return E->getSourceRange();
  }
  
  static bool pathOnlyInitializesGslPointer(IndirectLocalPath &Path) {
    for (auto It = Path.rbegin(), End = Path.rend(); It != End; ++It) {
      if (It->Kind == IndirectLocalPathEntry::VarInit)
        continue;
      if (It->Kind == IndirectLocalPathEntry::AddressOf)
        continue;
      return It->Kind == IndirectLocalPathEntry::GslPointerInit ||
             It->Kind == IndirectLocalPathEntry::GslReferenceInit;
    }
    return false;
  }
  
  void Sema::checkInitializerLifetime(const InitializedEntity &Entity,
                                      Expr *Init) {
    LifetimeResult LR = getEntityLifetime(&Entity);
    LifetimeKind LK = LR.getInt();
    const InitializedEntity *ExtendingEntity = LR.getPointer();
  
    // If this entity doesn't have an interesting lifetime, don't bother looking
    // for temporaries within its initializer.
    if (LK == LK_FullExpression)
      return;
  
    auto TemporaryVisitor = [&](IndirectLocalPath &Path, Local L,
                                ReferenceKind RK) -> bool {
      SourceRange DiagRange = nextPathEntryRange(Path, 0, L);
      SourceLocation DiagLoc = DiagRange.getBegin();
  
      auto *MTE = dyn_cast<MaterializeTemporaryExpr>(L);
  
      bool IsGslPtrInitWithGslTempOwner = false;
      bool IsLocalGslOwner = false;
      if (pathOnlyInitializesGslPointer(Path)) {
        if (isa<DeclRefExpr>(L)) {
          // We do not want to follow the references when returning a pointer originating
          // from a local owner to avoid the following false positive:
          //   int &p = *localUniquePtr;
          //   someContainer.add(std::move(localUniquePtr));
          //   return p;
          IsLocalGslOwner = isRecordWithAttr<OwnerAttr>(L->getType());
          if (pathContainsInit(Path) || !IsLocalGslOwner)
            return false;
        } else {
          IsGslPtrInitWithGslTempOwner = MTE && !MTE->getExtendingDecl() &&
                              isRecordWithAttr<OwnerAttr>(MTE->getType());
          // Skipping a chain of initializing gsl::Pointer annotated objects.
          // We are looking only for the final source to find out if it was
          // a local or temporary owner or the address of a local variable/param.
          if (!IsGslPtrInitWithGslTempOwner)
            return true;
        }
      }
  
      switch (LK) {
      case LK_FullExpression:
        llvm_unreachable("already handled this");
  
      case LK_Extended: {
        if (!MTE) {
          // The initialized entity has lifetime beyond the full-expression,
          // and the local entity does too, so don't warn.
          //
          // FIXME: We should consider warning if a static / thread storage
          // duration variable retains an automatic storage duration local.
          return false;
        }
  
        if (IsGslPtrInitWithGslTempOwner && DiagLoc.isValid()) {
          Diag(DiagLoc, diag::warn_dangling_lifetime_pointer) << DiagRange;
          return false;
        }
  
        // Lifetime-extend the temporary.
        if (Path.empty()) {
          // Update the storage duration of the materialized temporary.
          // FIXME: Rebuild the expression instead of mutating it.
          MTE->setExtendingDecl(ExtendingEntity->getDecl(),
                                ExtendingEntity->allocateManglingNumber());
          // Also visit the temporaries lifetime-extended by this initializer.
          return true;
        }
  
        if (shouldLifetimeExtendThroughPath(Path)) {
          // We're supposed to lifetime-extend the temporary along this path (per
          // the resolution of DR1815), but we don't support that yet.
          //
          // FIXME: Properly handle this situation. Perhaps the easiest approach
          // would be to clone the initializer expression on each use that would
          // lifetime extend its temporaries.
          Diag(DiagLoc, diag::warn_unsupported_lifetime_extension)
              << RK << DiagRange;
        } else {
          // If the path goes through the initialization of a variable or field,
          // it can't possibly reach a temporary created in this full-expression.
          // We will have already diagnosed any problems with the initializer.
          if (pathContainsInit(Path))
            return false;
  
          Diag(DiagLoc, diag::warn_dangling_variable)
              << RK << !Entity.getParent()
              << ExtendingEntity->getDecl()->isImplicit()
              << ExtendingEntity->getDecl() << Init->isGLValue() << DiagRange;
        }
        break;
      }
  
      case LK_MemInitializer: {
        if (isa<MaterializeTemporaryExpr>(L)) {
          // Under C++ DR1696, if a mem-initializer (or a default member
          // initializer used by the absence of one) would lifetime-extend a
          // temporary, the program is ill-formed.
          if (auto *ExtendingDecl =
                  ExtendingEntity ? ExtendingEntity->getDecl() : nullptr) {
            if (IsGslPtrInitWithGslTempOwner) {
              Diag(DiagLoc, diag::warn_dangling_lifetime_pointer_member)
                  << ExtendingDecl << DiagRange;
              Diag(ExtendingDecl->getLocation(),
                   diag::note_ref_or_ptr_member_declared_here)
                  << true;
              return false;
            }
            bool IsSubobjectMember = ExtendingEntity != &Entity;
            Diag(DiagLoc, shouldLifetimeExtendThroughPath(Path)
                              ? diag::err_dangling_member
                              : diag::warn_dangling_member)
                << ExtendingDecl << IsSubobjectMember << RK << DiagRange;
            // Don't bother adding a note pointing to the field if we're inside
            // its default member initializer; our primary diagnostic points to
            // the same place in that case.
            if (Path.empty() ||
                Path.back().Kind != IndirectLocalPathEntry::DefaultInit) {
              Diag(ExtendingDecl->getLocation(),
                   diag::note_lifetime_extending_member_declared_here)
                  << RK << IsSubobjectMember;
            }
          } else {
            // We have a mem-initializer but no particular field within it; this
            // is either a base class or a delegating initializer directly
            // initializing the base-class from something that doesn't live long
            // enough.
            //
            // FIXME: Warn on this.
            return false;
          }
        } else {
          // Paths via a default initializer can only occur during error recovery
          // (there's no other way that a default initializer can refer to a
          // local). Don't produce a bogus warning on those cases.
          if (pathContainsInit(Path))
            return false;
  
          // Suppress false positives for code like the one below:
          //   Ctor(unique_ptr<T> up) : member(*up), member2(move(up)) {}
          if (IsLocalGslOwner && pathOnlyInitializesGslPointer(Path))
            return false;
  
          auto *DRE = dyn_cast<DeclRefExpr>(L);
          auto *VD = DRE ? dyn_cast<VarDecl>(DRE->getDecl()) : nullptr;
          if (!VD) {
            // A member was initialized to a local block.
            // FIXME: Warn on this.
            return false;
          }
  
          if (auto *Member =
                  ExtendingEntity ? ExtendingEntity->getDecl() : nullptr) {
            bool IsPointer = !Member->getType()->isReferenceType();
            Diag(DiagLoc, IsPointer ? diag::warn_init_ptr_member_to_parameter_addr
                                    : diag::warn_bind_ref_member_to_parameter)
                << Member << VD << isa<ParmVarDecl>(VD) << DiagRange;
            Diag(Member->getLocation(),
                 diag::note_ref_or_ptr_member_declared_here)
                << (unsigned)IsPointer;
          }
        }
        break;
      }
  
      case LK_New:
        if (isa<MaterializeTemporaryExpr>(L)) {
          if (IsGslPtrInitWithGslTempOwner)
            Diag(DiagLoc, diag::warn_dangling_lifetime_pointer) << DiagRange;
          else
            Diag(DiagLoc, RK == RK_ReferenceBinding
                              ? diag::warn_new_dangling_reference
                              : diag::warn_new_dangling_initializer_list)
                << !Entity.getParent() << DiagRange;
        } else {
          // We can't determine if the allocation outlives the local declaration.
          return false;
        }
        break;
  
      case LK_Return:
      case LK_StmtExprResult:
        if (auto *DRE = dyn_cast<DeclRefExpr>(L)) {
          // We can't determine if the local variable outlives the statement
          // expression.
          if (LK == LK_StmtExprResult)
            return false;
          Diag(DiagLoc, diag::warn_ret_stack_addr_ref)
              << Entity.getType()->isReferenceType() << DRE->getDecl()
              << isa<ParmVarDecl>(DRE->getDecl()) << DiagRange;
        } else if (isa<BlockExpr>(L)) {
          Diag(DiagLoc, diag::err_ret_local_block) << DiagRange;
        } else if (isa<AddrLabelExpr>(L)) {
          // Don't warn when returning a label from a statement expression.
          // Leaving the scope doesn't end its lifetime.
          if (LK == LK_StmtExprResult)
            return false;
          Diag(DiagLoc, diag::warn_ret_addr_label) << DiagRange;
        } else {
          Diag(DiagLoc, diag::warn_ret_local_temp_addr_ref)
           << Entity.getType()->isReferenceType() << DiagRange;
        }
        break;
      }
  
      for (unsigned I = 0; I != Path.size(); ++I) {
        auto Elem = Path[I];
  
        switch (Elem.Kind) {
        case IndirectLocalPathEntry::AddressOf:
        case IndirectLocalPathEntry::LValToRVal:
          // These exist primarily to mark the path as not permitting or
          // supporting lifetime extension.
          break;
  
        case IndirectLocalPathEntry::LifetimeBoundCall:
        case IndirectLocalPathEntry::GslPointerInit:
        case IndirectLocalPathEntry::GslReferenceInit:
          // FIXME: Consider adding a note for these.
          break;
  
        case IndirectLocalPathEntry::DefaultInit: {
          auto *FD = cast<FieldDecl>(Elem.D);
          Diag(FD->getLocation(), diag::note_init_with_default_member_initalizer)
              << FD << nextPathEntryRange(Path, I + 1, L);
          break;
        }
  
        case IndirectLocalPathEntry::VarInit:
          const VarDecl *VD = cast<VarDecl>(Elem.D);
          Diag(VD->getLocation(), diag::note_local_var_initializer)
              << VD->getType()->isReferenceType()
              << VD->isImplicit() << VD->getDeclName()
              << nextPathEntryRange(Path, I + 1, L);
          break;
        }
      }
  
      // We didn't lifetime-extend, so don't go any further; we don't need more
      // warnings or errors on inner temporaries within this one's initializer.
      return false;
    };
  
    bool EnableLifetimeWarnings = !getDiagnostics().isIgnored(
        diag::warn_dangling_lifetime_pointer, SourceLocation());
    llvm::SmallVector<IndirectLocalPathEntry, 8> Path;
    if (Init->isGLValue())
      visitLocalsRetainedByReferenceBinding(Path, Init, RK_ReferenceBinding,
                                            TemporaryVisitor,
                                            EnableLifetimeWarnings);
    else
      visitLocalsRetainedByInitializer(Path, Init, TemporaryVisitor, false,
                                       EnableLifetimeWarnings);
  }
  
  static void DiagnoseNarrowingInInitList(Sema &S,
                                          const ImplicitConversionSequence &ICS,
                                          QualType PreNarrowingType,
                                          QualType EntityType,
                                          const Expr *PostInit);
  
  /// Provide warnings when std::move is used on construction.
  static void CheckMoveOnConstruction(Sema &S, const Expr *InitExpr,
                                      bool IsReturnStmt) {
    if (!InitExpr)
      return;
  
    if (S.inTemplateInstantiation())
      return;
  
    QualType DestType = InitExpr->getType();
    if (!DestType->isRecordType())
      return;
  
    unsigned DiagID = 0;
    if (IsReturnStmt) {
      const CXXConstructExpr *CCE =
          dyn_cast<CXXConstructExpr>(InitExpr->IgnoreParens());
      if (!CCE || CCE->getNumArgs() != 1)
        return;
  
      if (!CCE->getConstructor()->isCopyOrMoveConstructor())
        return;
  
      InitExpr = CCE->getArg(0)->IgnoreImpCasts();
    }
  
    // Find the std::move call and get the argument.
    const CallExpr *CE = dyn_cast<CallExpr>(InitExpr->IgnoreParens());
    if (!CE || !CE->isCallToStdMove())
      return;
  
    const Expr *Arg = CE->getArg(0)->IgnoreImplicit();
  
    if (IsReturnStmt) {
      const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(Arg->IgnoreParenImpCasts());
      if (!DRE || DRE->refersToEnclosingVariableOrCapture())
        return;
  
      const VarDecl *VD = dyn_cast<VarDecl>(DRE->getDecl());
      if (!VD || !VD->hasLocalStorage())
        return;
  
      // __block variables are not moved implicitly.
      if (VD->hasAttr<BlocksAttr>())
        return;
  
      QualType SourceType = VD->getType();
      if (!SourceType->isRecordType())
        return;
  
      if (!S.Context.hasSameUnqualifiedType(DestType, SourceType)) {
        return;
      }
  
      // If we're returning a function parameter, copy elision
      // is not possible.
      if (isa<ParmVarDecl>(VD))
        DiagID = diag::warn_redundant_move_on_return;
      else
        DiagID = diag::warn_pessimizing_move_on_return;
    } else {
      DiagID = diag::warn_pessimizing_move_on_initialization;
      const Expr *ArgStripped = Arg->IgnoreImplicit()->IgnoreParens();
      if (!ArgStripped->isRValue() || !ArgStripped->getType()->isRecordType())
        return;
    }
  
    S.Diag(CE->getBeginLoc(), DiagID);
  
    // Get all the locations for a fix-it.  Don't emit the fix-it if any location
    // is within a macro.
    SourceLocation CallBegin = CE->getCallee()->getBeginLoc();
    if (CallBegin.isMacroID())
      return;
    SourceLocation RParen = CE->getRParenLoc();
    if (RParen.isMacroID())
      return;
    SourceLocation LParen;
    SourceLocation ArgLoc = Arg->getBeginLoc();
  
    // Special testing for the argument location.  Since the fix-it needs the
    // location right before the argument, the argument location can be in a
    // macro only if it is at the beginning of the macro.
    while (ArgLoc.isMacroID() &&
           S.getSourceManager().isAtStartOfImmediateMacroExpansion(ArgLoc)) {
      ArgLoc = S.getSourceManager().getImmediateExpansionRange(ArgLoc).getBegin();
    }
  
    if (LParen.isMacroID())
      return;
  
    LParen = ArgLoc.getLocWithOffset(-1);
  
    S.Diag(CE->getBeginLoc(), diag::note_remove_move)
        << FixItHint::CreateRemoval(SourceRange(CallBegin, LParen))
        << FixItHint::CreateRemoval(SourceRange(RParen, RParen));
  }
  
  static void CheckForNullPointerDereference(Sema &S, const Expr *E) {
    // Check to see if we are dereferencing a null pointer.  If so, this is
    // undefined behavior, so warn about it.  This only handles the pattern
    // "*null", which is a very syntactic check.
    if (const UnaryOperator *UO = dyn_cast<UnaryOperator>(E->IgnoreParenCasts()))
      if (UO->getOpcode() == UO_Deref &&
          UO->getSubExpr()->IgnoreParenCasts()->
          isNullPointerConstant(S.Context, Expr::NPC_ValueDependentIsNotNull)) {
      S.DiagRuntimeBehavior(UO->getOperatorLoc(), UO,
                            S.PDiag(diag::warn_binding_null_to_reference)
                              << UO->getSubExpr()->getSourceRange());
    }
  }
  
  MaterializeTemporaryExpr *
  Sema::CreateMaterializeTemporaryExpr(QualType T, Expr *Temporary,
                                       bool BoundToLvalueReference) {
    auto MTE = new (Context)
        MaterializeTemporaryExpr(T, Temporary, BoundToLvalueReference);
  
    // Order an ExprWithCleanups for lifetime marks.
    //
    // TODO: It'll be good to have a single place to check the access of the
    // destructor and generate ExprWithCleanups for various uses. Currently these
    // are done in both CreateMaterializeTemporaryExpr and MaybeBindToTemporary,
    // but there may be a chance to merge them.
    Cleanup.setExprNeedsCleanups(false);
    return MTE;
  }
  
  ExprResult Sema::TemporaryMaterializationConversion(Expr *E) {
    // In C++98, we don't want to implicitly create an xvalue.
    // FIXME: This means that AST consumers need to deal with "prvalues" that
    // denote materialized temporaries. Maybe we should add another ValueKind
    // for "xvalue pretending to be a prvalue" for C++98 support.
    if (!E->isRValue() || !getLangOpts().CPlusPlus11)
      return E;
  
    // C++1z [conv.rval]/1: T shall be a complete type.
    // FIXME: Does this ever matter (can we form a prvalue of incomplete type)?
    // If so, we should check for a non-abstract class type here too.
    QualType T = E->getType();
    if (RequireCompleteType(E->getExprLoc(), T, diag::err_incomplete_type))
      return ExprError();
  
    return CreateMaterializeTemporaryExpr(E->getType(), E, false);
  }
  
  ExprResult Sema::PerformQualificationConversion(Expr *E, QualType Ty,
                                                  ExprValueKind VK,
                                                  CheckedConversionKind CCK) {
  
    CastKind CK = CK_NoOp;
  
    if (VK == VK_RValue) {
      auto PointeeTy = Ty->getPointeeType();
      auto ExprPointeeTy = E->getType()->getPointeeType();
      if (!PointeeTy.isNull() &&
          PointeeTy.getAddressSpace() != ExprPointeeTy.getAddressSpace())
        CK = CK_AddressSpaceConversion;
    } else if (Ty.getAddressSpace() != E->getType().getAddressSpace()) {
      CK = CK_AddressSpaceConversion;
    }
  
    return ImpCastExprToType(E, Ty, CK, VK, /*BasePath=*/nullptr, CCK);
  }
  
  ExprResult InitializationSequence::Perform(Sema &S,
                                             const InitializedEntity &Entity,
                                             const InitializationKind &Kind,
                                             MultiExprArg Args,
                                             QualType *ResultType) {
    if (Failed()) {
      Diagnose(S, Entity, Kind, Args);
      return ExprError();
    }
    if (!ZeroInitializationFixit.empty()) {
      unsigned DiagID = diag::err_default_init_const;
      if (Decl *D = Entity.getDecl())
        if (S.getLangOpts().MSVCCompat && D->hasAttr<SelectAnyAttr>())
          DiagID = diag::ext_default_init_const;
  
      // The initialization would have succeeded with this fixit. Since the fixit
      // is on the error, we need to build a valid AST in this case, so this isn't
      // handled in the Failed() branch above.
      QualType DestType = Entity.getType();
      S.Diag(Kind.getLocation(), DiagID)
          << DestType << (bool)DestType->getAs<RecordType>()
          << FixItHint::CreateInsertion(ZeroInitializationFixitLoc,
                                        ZeroInitializationFixit);
    }
  
    if (getKind() == DependentSequence) {
      // If the declaration is a non-dependent, incomplete array type
      // that has an initializer, then its type will be completed once
      // the initializer is instantiated.
      if (ResultType && !Entity.getType()->isDependentType() &&
          Args.size() == 1) {
        QualType DeclType = Entity.getType();
        if (const IncompleteArrayType *ArrayT
                             = S.Context.getAsIncompleteArrayType(DeclType)) {
          // FIXME: We don't currently have the ability to accurately
          // compute the length of an initializer list without
          // performing full type-checking of the initializer list
          // (since we have to determine where braces are implicitly
          // introduced and such).  So, we fall back to making the array
          // type a dependently-sized array type with no specified
          // bound.
          if (isa<InitListExpr>((Expr *)Args[0])) {
            SourceRange Brackets;
  
            // Scavange the location of the brackets from the entity, if we can.
            if (auto *DD = dyn_cast_or_null<DeclaratorDecl>(Entity.getDecl())) {
              if (TypeSourceInfo *TInfo = DD->getTypeSourceInfo()) {
                TypeLoc TL = TInfo->getTypeLoc();
                if (IncompleteArrayTypeLoc ArrayLoc =
                        TL.getAs<IncompleteArrayTypeLoc>())
                  Brackets = ArrayLoc.getBracketsRange();
              }
            }
  
            *ResultType
              = S.Context.getDependentSizedArrayType(ArrayT->getElementType(),
                                                     /*NumElts=*/nullptr,
                                                     ArrayT->getSizeModifier(),
                                         ArrayT->getIndexTypeCVRQualifiers(),
                                                     Brackets);
          }
  
        }
      }
      if (Kind.getKind() == InitializationKind::IK_Direct &&
          !Kind.isExplicitCast()) {
        // Rebuild the ParenListExpr.
        SourceRange ParenRange = Kind.getParenOrBraceRange();
        return S.ActOnParenListExpr(ParenRange.getBegin(), ParenRange.getEnd(),
                                    Args);
      }
      assert(Kind.getKind() == InitializationKind::IK_Copy ||
             Kind.isExplicitCast() ||
             Kind.getKind() == InitializationKind::IK_DirectList);
      return ExprResult(Args[0]);
    }
  
    // No steps means no initialization.
    if (Steps.empty())
      return ExprResult((Expr *)nullptr);
  
    if (S.getLangOpts().CPlusPlus11 && Entity.getType()->isReferenceType() &&
        Args.size() == 1 && isa<InitListExpr>(Args[0]) &&
        !Entity.isParameterKind()) {
      // Produce a C++98 compatibility warning if we are initializing a reference
      // from an initializer list. For parameters, we produce a better warning
      // elsewhere.
      Expr *Init = Args[0];
      S.Diag(Init->getBeginLoc(), diag::warn_cxx98_compat_reference_list_init)
          << Init->getSourceRange();
    }
  
    // OpenCL v2.0 s6.13.11.1. atomic variables can be initialized in global scope
    QualType ETy = Entity.getType();
    bool HasGlobalAS = ETy.hasAddressSpace() &&
                       ETy.getAddressSpace() == LangAS::opencl_global;
  
    if (S.getLangOpts().OpenCLVersion >= 200 &&
        ETy->isAtomicType() && !HasGlobalAS &&
        Entity.getKind() == InitializedEntity::EK_Variable && Args.size() > 0) {
      S.Diag(Args[0]->getBeginLoc(), diag::err_opencl_atomic_init)
          << 1
          << SourceRange(Entity.getDecl()->getBeginLoc(), Args[0]->getEndLoc());
      return ExprError();
    }
  
    QualType DestType = Entity.getType().getNonReferenceType();
    // FIXME: Ugly hack around the fact that Entity.getType() is not
    // the same as Entity.getDecl()->getType() in cases involving type merging,
    //  and we want latter when it makes sense.
    if (ResultType)
      *ResultType = Entity.getDecl() ? Entity.getDecl()->getType() :
                                       Entity.getType();
  
    ExprResult CurInit((Expr *)nullptr);
    SmallVector<Expr*, 4> ArrayLoopCommonExprs;
  
    // For initialization steps that start with a single initializer,
    // grab the only argument out the Args and place it into the "current"
    // initializer.
    switch (Steps.front().Kind) {
    case SK_ResolveAddressOfOverloadedFunction:
    case SK_CastDerivedToBaseRValue:
    case SK_CastDerivedToBaseXValue:
    case SK_CastDerivedToBaseLValue:
    case SK_BindReference:
    case SK_BindReferenceToTemporary:
    case SK_FinalCopy:
    case SK_ExtraneousCopyToTemporary:
    case SK_UserConversion:
    case SK_QualificationConversionLValue:
    case SK_QualificationConversionXValue:
    case SK_QualificationConversionRValue:
    case SK_AtomicConversion:
    case SK_ConversionSequence:
    case SK_ConversionSequenceNoNarrowing:
    case SK_ListInitialization:
    case SK_UnwrapInitList:
    case SK_RewrapInitList:
    case SK_CAssignment:
    case SK_StringInit:
    case SK_ObjCObjectConversion:
    case SK_ArrayLoopIndex:
    case SK_ArrayLoopInit:
    case SK_ArrayInit:
    case SK_GNUArrayInit:
    case SK_ParenthesizedArrayInit:
    case SK_PassByIndirectCopyRestore:
    case SK_PassByIndirectRestore:
    case SK_ProduceObjCObject:
    case SK_StdInitializerList:
    case SK_OCLSamplerInit:
    case SK_OCLZeroOpaqueType: {
      assert(Args.size() == 1);
      CurInit = Args[0];
      if (!CurInit.get()) return ExprError();
      break;
    }
  
    case SK_ConstructorInitialization:
    case SK_ConstructorInitializationFromList:
    case SK_StdInitializerListConstructorCall:
    case SK_ZeroInitialization:
      break;
    }
  
    // Promote from an unevaluated context to an unevaluated list context in
    // C++11 list-initialization; we need to instantiate entities usable in
    // constant expressions here in order to perform narrowing checks =(
    EnterExpressionEvaluationContext Evaluated(
        S, EnterExpressionEvaluationContext::InitList,
        CurInit.get() && isa<InitListExpr>(CurInit.get()));
  
    // C++ [class.abstract]p2:
    //   no objects of an abstract class can be created except as subobjects
    //   of a class derived from it
    auto checkAbstractType = [&](QualType T) -> bool {
      if (Entity.getKind() == InitializedEntity::EK_Base ||
          Entity.getKind() == InitializedEntity::EK_Delegating)
        return false;
      return S.RequireNonAbstractType(Kind.getLocation(), T,
                                      diag::err_allocation_of_abstract_type);
    };
  
    // Walk through the computed steps for the initialization sequence,
    // performing the specified conversions along the way.
    bool ConstructorInitRequiresZeroInit = false;
    for (step_iterator Step = step_begin(), StepEnd = step_end();
         Step != StepEnd; ++Step) {
      if (CurInit.isInvalid())
        return ExprError();
  
      QualType SourceType = CurInit.get() ? CurInit.get()->getType() : QualType();
  
      switch (Step->Kind) {
      case SK_ResolveAddressOfOverloadedFunction:
        // Overload resolution determined which function invoke; update the
        // initializer to reflect that choice.
        S.CheckAddressOfMemberAccess(CurInit.get(), Step->Function.FoundDecl);
        if (S.DiagnoseUseOfDecl(Step->Function.FoundDecl, Kind.getLocation()))
          return ExprError();
        CurInit = S.FixOverloadedFunctionReference(CurInit,
                                                   Step->Function.FoundDecl,
                                                   Step->Function.Function);
        break;
  
      case SK_CastDerivedToBaseRValue:
      case SK_CastDerivedToBaseXValue:
      case SK_CastDerivedToBaseLValue: {
        // We have a derived-to-base cast that produces either an rvalue or an
        // lvalue. Perform that cast.
  
        CXXCastPath BasePath;
  
        // Casts to inaccessible base classes are allowed with C-style casts.
        bool IgnoreBaseAccess = Kind.isCStyleOrFunctionalCast();
        if (S.CheckDerivedToBaseConversion(
                SourceType, Step->Type, CurInit.get()->getBeginLoc(),
                CurInit.get()->getSourceRange(), &BasePath, IgnoreBaseAccess))
          return ExprError();
  
        ExprValueKind VK =
            Step->Kind == SK_CastDerivedToBaseLValue ?
                VK_LValue :
                (Step->Kind == SK_CastDerivedToBaseXValue ?
                     VK_XValue :
                     VK_RValue);
        CurInit =
            ImplicitCastExpr::Create(S.Context, Step->Type, CK_DerivedToBase,
                                     CurInit.get(), &BasePath, VK);
        break;
      }
  
      case SK_BindReference:
        // Reference binding does not have any corresponding ASTs.
  
        // Check exception specifications
        if (S.CheckExceptionSpecCompatibility(CurInit.get(), DestType))
          return ExprError();
  
        // We don't check for e.g. function pointers here, since address
        // availability checks should only occur when the function first decays
        // into a pointer or reference.
        if (CurInit.get()->getType()->isFunctionProtoType()) {
          if (auto *DRE = dyn_cast<DeclRefExpr>(CurInit.get()->IgnoreParens())) {
            if (auto *FD = dyn_cast<FunctionDecl>(DRE->getDecl())) {
              if (!S.checkAddressOfFunctionIsAvailable(FD, /*Complain=*/true,
                                                       DRE->getBeginLoc()))
                return ExprError();
            }
          }
        }
  
        CheckForNullPointerDereference(S, CurInit.get());
        break;
  
      case SK_BindReferenceToTemporary: {
        // Make sure the "temporary" is actually an rvalue.
        assert(CurInit.get()->isRValue() && "not a temporary");
  
        // Check exception specifications
        if (S.CheckExceptionSpecCompatibility(CurInit.get(), DestType))
          return ExprError();
  
        // Materialize the temporary into memory.
        MaterializeTemporaryExpr *MTE = S.CreateMaterializeTemporaryExpr(
            Step->Type, CurInit.get(), Entity.getType()->isLValueReferenceType());
        CurInit = MTE;
  
        // If we're extending this temporary to automatic storage duration -- we
        // need to register its cleanup during the full-expression's cleanups.
        if (MTE->getStorageDuration() == SD_Automatic &&
            MTE->getType().isDestructedType())
          S.Cleanup.setExprNeedsCleanups(true);
        break;
      }
  
      case SK_FinalCopy:
        if (checkAbstractType(Step->Type))
          return ExprError();
  
        // If the overall initialization is initializing a temporary, we already
        // bound our argument if it was necessary to do so. If not (if we're
        // ultimately initializing a non-temporary), our argument needs to be
        // bound since it's initializing a function parameter.
        // FIXME: This is a mess. Rationalize temporary destruction.
        if (!shouldBindAsTemporary(Entity))
          CurInit = S.MaybeBindToTemporary(CurInit.get());
        CurInit = CopyObject(S, Step->Type, Entity, CurInit,
                             /*IsExtraneousCopy=*/false);
        break;
  
      case SK_ExtraneousCopyToTemporary:
        CurInit = CopyObject(S, Step->Type, Entity, CurInit,
                             /*IsExtraneousCopy=*/true);
        break;
  
      case SK_UserConversion: {
        // We have a user-defined conversion that invokes either a constructor
        // or a conversion function.
        CastKind CastKind;
        FunctionDecl *Fn = Step->Function.Function;
        DeclAccessPair FoundFn = Step->Function.FoundDecl;
        bool HadMultipleCandidates = Step->Function.HadMultipleCandidates;
        bool CreatedObject = false;
        if (CXXConstructorDecl *Constructor = dyn_cast<CXXConstructorDecl>(Fn)) {
          // Build a call to the selected constructor.
          SmallVector<Expr*, 8> ConstructorArgs;
          SourceLocation Loc = CurInit.get()->getBeginLoc();
  
          // Determine the arguments required to actually perform the constructor
          // call.
          Expr *Arg = CurInit.get();
          if (S.CompleteConstructorCall(Constructor,
                                        MultiExprArg(&Arg, 1),
                                        Loc, ConstructorArgs))
            return ExprError();
  
          // Build an expression that constructs a temporary.
          CurInit = S.BuildCXXConstructExpr(Loc, Step->Type,
                                            FoundFn, Constructor,
                                            ConstructorArgs,
                                            HadMultipleCandidates,
                                            /*ListInit*/ false,
                                            /*StdInitListInit*/ false,
                                            /*ZeroInit*/ false,
                                            CXXConstructExpr::CK_Complete,
                                            SourceRange());
          if (CurInit.isInvalid())
            return ExprError();
  
          S.CheckConstructorAccess(Kind.getLocation(), Constructor, FoundFn,
                                   Entity);
          if (S.DiagnoseUseOfDecl(FoundFn, Kind.getLocation()))
            return ExprError();
  
          CastKind = CK_ConstructorConversion;
          CreatedObject = true;
        } else {
          // Build a call to the conversion function.
          CXXConversionDecl *Conversion = cast<CXXConversionDecl>(Fn);
          S.CheckMemberOperatorAccess(Kind.getLocation(), CurInit.get(), nullptr,
                                      FoundFn);
          if (S.DiagnoseUseOfDecl(FoundFn, Kind.getLocation()))
            return ExprError();
  
          CurInit = S.BuildCXXMemberCallExpr(CurInit.get(), FoundFn, Conversion,
                                             HadMultipleCandidates);
          if (CurInit.isInvalid())
            return ExprError();
  
          CastKind = CK_UserDefinedConversion;
          CreatedObject = Conversion->getReturnType()->isRecordType();
        }
  
        if (CreatedObject && checkAbstractType(CurInit.get()->getType()))
          return ExprError();
  
        CurInit = ImplicitCastExpr::Create(S.Context, CurInit.get()->getType(),
                                           CastKind, CurInit.get(), nullptr,
                                           CurInit.get()->getValueKind());
  
        if (shouldBindAsTemporary(Entity))
          // The overall entity is temporary, so this expression should be
          // destroyed at the end of its full-expression.
          CurInit = S.MaybeBindToTemporary(CurInit.getAs<Expr>());
        else if (CreatedObject && shouldDestroyEntity(Entity)) {
          // The object outlasts the full-expression, but we need to prepare for
          // a destructor being run on it.
          // FIXME: It makes no sense to do this here. This should happen
          // regardless of how we initialized the entity.
          QualType T = CurInit.get()->getType();
          if (const RecordType *Record = T->getAs<RecordType>()) {
            CXXDestructorDecl *Destructor
              = S.LookupDestructor(cast<CXXRecordDecl>(Record->getDecl()));
            S.CheckDestructorAccess(CurInit.get()->getBeginLoc(), Destructor,
                                    S.PDiag(diag::err_access_dtor_temp) << T);
            S.MarkFunctionReferenced(CurInit.get()->getBeginLoc(), Destructor);
            if (S.DiagnoseUseOfDecl(Destructor, CurInit.get()->getBeginLoc()))
              return ExprError();
          }
        }
        break;
      }
  
      case SK_QualificationConversionLValue:
      case SK_QualificationConversionXValue:
      case SK_QualificationConversionRValue: {
        // Perform a qualification conversion; these can never go wrong.
        ExprValueKind VK =
            Step->Kind == SK_QualificationConversionLValue
                ? VK_LValue
                : (Step->Kind == SK_QualificationConversionXValue ? VK_XValue
                                                                  : VK_RValue);
        CurInit = S.PerformQualificationConversion(CurInit.get(), Step->Type, VK);
        break;
      }
  
      case SK_AtomicConversion: {
        assert(CurInit.get()->isRValue() && "cannot convert glvalue to atomic");
        CurInit = S.ImpCastExprToType(CurInit.get(), Step->Type,
                                      CK_NonAtomicToAtomic, VK_RValue);
        break;
      }
  
      case SK_ConversionSequence:
      case SK_ConversionSequenceNoNarrowing: {
        if (const auto *FromPtrType =
                CurInit.get()->getType()->getAs<PointerType>()) {
          if (const auto *ToPtrType = Step->Type->getAs<PointerType>()) {
            if (FromPtrType->getPointeeType()->hasAttr(attr::NoDeref) &&
                !ToPtrType->getPointeeType()->hasAttr(attr::NoDeref)) {
              // Do not check static casts here because they are checked earlier
              // in Sema::ActOnCXXNamedCast()
              if (!Kind.isStaticCast()) {
                S.Diag(CurInit.get()->getExprLoc(),
                       diag::warn_noderef_to_dereferenceable_pointer)
                    << CurInit.get()->getSourceRange();
              }
            }
          }
        }
  
        Sema::CheckedConversionKind CCK
          = Kind.isCStyleCast()? Sema::CCK_CStyleCast
          : Kind.isFunctionalCast()? Sema::CCK_FunctionalCast
          : Kind.isExplicitCast()? Sema::CCK_OtherCast
          : Sema::CCK_ImplicitConversion;
        ExprResult CurInitExprRes =
          S.PerformImplicitConversion(CurInit.get(), Step->Type, *Step->ICS,
                                      getAssignmentAction(Entity), CCK);
        if (CurInitExprRes.isInvalid())
          return ExprError();
  
        S.DiscardMisalignedMemberAddress(Step->Type.getTypePtr(), CurInit.get());
  
        CurInit = CurInitExprRes;
  
        if (Step->Kind == SK_ConversionSequenceNoNarrowing &&
            S.getLangOpts().CPlusPlus)
          DiagnoseNarrowingInInitList(S, *Step->ICS, SourceType, Entity.getType(),
                                      CurInit.get());
  
        break;
      }
  
      case SK_ListInitialization: {
        if (checkAbstractType(Step->Type))
          return ExprError();
  
        InitListExpr *InitList = cast<InitListExpr>(CurInit.get());
        // If we're not initializing the top-level entity, we need to create an
        // InitializeTemporary entity for our target type.
        QualType Ty = Step->Type;
        bool IsTemporary = !S.Context.hasSameType(Entity.getType(), Ty);
        InitializedEntity TempEntity = InitializedEntity::InitializeTemporary(Ty);
        InitializedEntity InitEntity = IsTemporary ? TempEntity : Entity;
        InitListChecker PerformInitList(S, InitEntity,
            InitList, Ty, /*VerifyOnly=*/false,
            /*TreatUnavailableAsInvalid=*/false);
        if (PerformInitList.HadError())
          return ExprError();
  
        // Hack: We must update *ResultType if available in order to set the
        // bounds of arrays, e.g. in 'int ar[] = {1, 2, 3};'.
        // Worst case: 'const int (&arref)[] = {1, 2, 3};'.
        if (ResultType &&
            ResultType->getNonReferenceType()->isIncompleteArrayType()) {
          if ((*ResultType)->isRValueReferenceType())
            Ty = S.Context.getRValueReferenceType(Ty);
          else if ((*ResultType)->isLValueReferenceType())
            Ty = S.Context.getLValueReferenceType(Ty,
              (*ResultType)->castAs<LValueReferenceType>()->isSpelledAsLValue());
          *ResultType = Ty;
        }
  
        InitListExpr *StructuredInitList =
            PerformInitList.getFullyStructuredList();
        CurInit.get();
        CurInit = shouldBindAsTemporary(InitEntity)
            ? S.MaybeBindToTemporary(StructuredInitList)
            : StructuredInitList;
        break;
      }
  
      case SK_ConstructorInitializationFromList: {
        if (checkAbstractType(Step->Type))
          return ExprError();
  
        // When an initializer list is passed for a parameter of type "reference
        // to object", we don't get an EK_Temporary entity, but instead an
        // EK_Parameter entity with reference type.
        // FIXME: This is a hack. What we really should do is create a user
        // conversion step for this case, but this makes it considerably more
        // complicated. For now, this will do.
        InitializedEntity TempEntity = InitializedEntity::InitializeTemporary(
                                          Entity.getType().getNonReferenceType());
        bool UseTemporary = Entity.getType()->isReferenceType();
        assert(Args.size() == 1 && "expected a single argument for list init");
        InitListExpr *InitList = cast<InitListExpr>(Args[0]);
        S.Diag(InitList->getExprLoc(), diag::warn_cxx98_compat_ctor_list_init)
          << InitList->getSourceRange();
        MultiExprArg Arg(InitList->getInits(), InitList->getNumInits());
        CurInit = PerformConstructorInitialization(S, UseTemporary ? TempEntity :
                                                                     Entity,
                                                   Kind, Arg, *Step,
                                                 ConstructorInitRequiresZeroInit,
                                                 /*IsListInitialization*/true,
                                                 /*IsStdInitListInit*/false,
                                                 InitList->getLBraceLoc(),
                                                 InitList->getRBraceLoc());
        break;
      }
  
      case SK_UnwrapInitList:
        CurInit = cast<InitListExpr>(CurInit.get())->getInit(0);
        break;
  
      case SK_RewrapInitList: {
        Expr *E = CurInit.get();
        InitListExpr *Syntactic = Step->WrappingSyntacticList;
        InitListExpr *ILE = new (S.Context) InitListExpr(S.Context,
            Syntactic->getLBraceLoc(), E, Syntactic->getRBraceLoc());
        ILE->setSyntacticForm(Syntactic);
        ILE->setType(E->getType());
        ILE->setValueKind(E->getValueKind());
        CurInit = ILE;
        break;
      }
  
      case SK_ConstructorInitialization:
      case SK_StdInitializerListConstructorCall: {
        if (checkAbstractType(Step->Type))
          return ExprError();
  
        // When an initializer list is passed for a parameter of type "reference
        // to object", we don't get an EK_Temporary entity, but instead an
        // EK_Parameter entity with reference type.
        // FIXME: This is a hack. What we really should do is create a user
        // conversion step for this case, but this makes it considerably more
        // complicated. For now, this will do.
        InitializedEntity TempEntity = InitializedEntity::InitializeTemporary(
                                          Entity.getType().getNonReferenceType());
        bool UseTemporary = Entity.getType()->isReferenceType();
        bool IsStdInitListInit =
            Step->Kind == SK_StdInitializerListConstructorCall;
        Expr *Source = CurInit.get();
        SourceRange Range = Kind.hasParenOrBraceRange()
                                ? Kind.getParenOrBraceRange()
                                : SourceRange();
        CurInit = PerformConstructorInitialization(
            S, UseTemporary ? TempEntity : Entity, Kind,
            Source ? MultiExprArg(Source) : Args, *Step,
            ConstructorInitRequiresZeroInit,
            /*IsListInitialization*/ IsStdInitListInit,
            /*IsStdInitListInitialization*/ IsStdInitListInit,
            /*LBraceLoc*/ Range.getBegin(),
            /*RBraceLoc*/ Range.getEnd());
        break;
      }
  
      case SK_ZeroInitialization: {
        step_iterator NextStep = Step;
        ++NextStep;
        if (NextStep != StepEnd &&
            (NextStep->Kind == SK_ConstructorInitialization ||
             NextStep->Kind == SK_ConstructorInitializationFromList)) {
          // The need for zero-initialization is recorded directly into
          // the call to the object's constructor within the next step.
          ConstructorInitRequiresZeroInit = true;
        } else if (Kind.getKind() == InitializationKind::IK_Value &&
                   S.getLangOpts().CPlusPlus &&
                   !Kind.isImplicitValueInit()) {
          TypeSourceInfo *TSInfo = Entity.getTypeSourceInfo();
          if (!TSInfo)
            TSInfo = S.Context.getTrivialTypeSourceInfo(Step->Type,
                                                      Kind.getRange().getBegin());
  
          CurInit = new (S.Context) CXXScalarValueInitExpr(
              Entity.getType().getNonLValueExprType(S.Context), TSInfo,
              Kind.getRange().getEnd());
        } else {
          CurInit = new (S.Context) ImplicitValueInitExpr(Step->Type);
        }
        break;
      }
  
      case SK_CAssignment: {
        QualType SourceType = CurInit.get()->getType();
  
        // Save off the initial CurInit in case we need to emit a diagnostic
        ExprResult InitialCurInit = CurInit;
        ExprResult Result = CurInit;
        Sema::AssignConvertType ConvTy =
          S.CheckSingleAssignmentConstraints(Step->Type, Result, true,
              Entity.getKind() == InitializedEntity::EK_Parameter_CF_Audited);
        if (Result.isInvalid())
          return ExprError();
        CurInit = Result;
  
        // If this is a call, allow conversion to a transparent union.
        ExprResult CurInitExprRes = CurInit;
        if (ConvTy != Sema::Compatible &&
            Entity.isParameterKind() &&
            S.CheckTransparentUnionArgumentConstraints(Step->Type, CurInitExprRes)
              == Sema::Compatible)
          ConvTy = Sema::Compatible;
        if (CurInitExprRes.isInvalid())
          return ExprError();
        CurInit = CurInitExprRes;
  
        bool Complained;
        if (S.DiagnoseAssignmentResult(ConvTy, Kind.getLocation(),
                                       Step->Type, SourceType,
                                       InitialCurInit.get(),
                                       getAssignmentAction(Entity, true),
                                       &Complained)) {
          PrintInitLocationNote(S, Entity);
          return ExprError();
        } else if (Complained)
          PrintInitLocationNote(S, Entity);
        break;
      }
  
      case SK_StringInit: {
        QualType Ty = Step->Type;
        CheckStringInit(CurInit.get(), ResultType ? *ResultType : Ty,
                        S.Context.getAsArrayType(Ty), S);
        break;
      }
  
      case SK_ObjCObjectConversion:
        CurInit = S.ImpCastExprToType(CurInit.get(), Step->Type,
                            CK_ObjCObjectLValueCast,
                            CurInit.get()->getValueKind());
        break;
  
      case SK_ArrayLoopIndex: {
        Expr *Cur = CurInit.get();
        Expr *BaseExpr = new (S.Context)
            OpaqueValueExpr(Cur->getExprLoc(), Cur->getType(),
                            Cur->getValueKind(), Cur->getObjectKind(), Cur);
        Expr *IndexExpr =
            new (S.Context) ArrayInitIndexExpr(S.Context.getSizeType());
        CurInit = S.CreateBuiltinArraySubscriptExpr(
            BaseExpr, Kind.getLocation(), IndexExpr, Kind.getLocation());
        ArrayLoopCommonExprs.push_back(BaseExpr);
        break;
      }
  
      case SK_ArrayLoopInit: {
        assert(!ArrayLoopCommonExprs.empty() &&
               "mismatched SK_ArrayLoopIndex and SK_ArrayLoopInit");
        Expr *Common = ArrayLoopCommonExprs.pop_back_val();
        CurInit = new (S.Context) ArrayInitLoopExpr(Step->Type, Common,
                                                    CurInit.get());
        break;
      }
  
      case SK_GNUArrayInit:
        // Okay: we checked everything before creating this step. Note that
        // this is a GNU extension.
        S.Diag(Kind.getLocation(), diag::ext_array_init_copy)
          << Step->Type << CurInit.get()->getType()
          << CurInit.get()->getSourceRange();
        updateGNUCompoundLiteralRValue(CurInit.get());
        LLVM_FALLTHROUGH;
      case SK_ArrayInit:
        // If the destination type is an incomplete array type, update the
        // type accordingly.
        if (ResultType) {
          if (const IncompleteArrayType *IncompleteDest
                             = S.Context.getAsIncompleteArrayType(Step->Type)) {
            if (const ConstantArrayType *ConstantSource
                   = S.Context.getAsConstantArrayType(CurInit.get()->getType())) {
              *ResultType = S.Context.getConstantArrayType(
                                               IncompleteDest->getElementType(),
                                               ConstantSource->getSize(),
                                               ConstantSource->getSizeExpr(),
                                               ArrayType::Normal, 0);
            }
          }
        }
        break;
  
      case SK_ParenthesizedArrayInit:
        // Okay: we checked everything before creating this step. Note that
        // this is a GNU extension.
        S.Diag(Kind.getLocation(), diag::ext_array_init_parens)
          << CurInit.get()->getSourceRange();
        break;
  
      case SK_PassByIndirectCopyRestore:
      case SK_PassByIndirectRestore:
        checkIndirectCopyRestoreSource(S, CurInit.get());
        CurInit = new (S.Context) ObjCIndirectCopyRestoreExpr(
            CurInit.get(), Step->Type,
            Step->Kind == SK_PassByIndirectCopyRestore);
        break;
  
      case SK_ProduceObjCObject:
        CurInit =
            ImplicitCastExpr::Create(S.Context, Step->Type, CK_ARCProduceObject,
                                     CurInit.get(), nullptr, VK_RValue);
        break;
  
      case SK_StdInitializerList: {
        S.Diag(CurInit.get()->getExprLoc(),
               diag::warn_cxx98_compat_initializer_list_init)
          << CurInit.get()->getSourceRange();
  
        // Materialize the temporary into memory.
        MaterializeTemporaryExpr *MTE = S.CreateMaterializeTemporaryExpr(
            CurInit.get()->getType(), CurInit.get(),
            /*BoundToLvalueReference=*/false);
  
        // Wrap it in a construction of a std::initializer_list<T>.
        CurInit = new (S.Context) CXXStdInitializerListExpr(Step->Type, MTE);
  
        // Bind the result, in case the library has given initializer_list a
        // non-trivial destructor.
        if (shouldBindAsTemporary(Entity))
          CurInit = S.MaybeBindToTemporary(CurInit.get());
        break;
      }
  
      case SK_OCLSamplerInit: {
        // Sampler initialization have 5 cases:
        //   1. function argument passing
        //      1a. argument is a file-scope variable
        //      1b. argument is a function-scope variable
        //      1c. argument is one of caller function's parameters
        //   2. variable initialization
        //      2a. initializing a file-scope variable
        //      2b. initializing a function-scope variable
        //
        // For file-scope variables, since they cannot be initialized by function
        // call of __translate_sampler_initializer in LLVM IR, their references
        // need to be replaced by a cast from their literal initializers to
        // sampler type. Since sampler variables can only be used in function
        // calls as arguments, we only need to replace them when handling the
        // argument passing.
        assert(Step->Type->isSamplerT() &&
               "Sampler initialization on non-sampler type.");
        Expr *Init = CurInit.get()->IgnoreParens();
        QualType SourceType = Init->getType();
        // Case 1
        if (Entity.isParameterKind()) {
          if (!SourceType->isSamplerT() && !SourceType->isIntegerType()) {
            S.Diag(Kind.getLocation(), diag::err_sampler_argument_required)
              << SourceType;
            break;
          } else if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(Init)) {
            auto Var = cast<VarDecl>(DRE->getDecl());
            // Case 1b and 1c
            // No cast from integer to sampler is needed.
            if (!Var->hasGlobalStorage()) {
              CurInit = ImplicitCastExpr::Create(S.Context, Step->Type,
                                                 CK_LValueToRValue, Init,
                                                 /*BasePath=*/nullptr, VK_RValue);
              break;
            }
            // Case 1a
            // For function call with a file-scope sampler variable as argument,
            // get the integer literal.
            // Do not diagnose if the file-scope variable does not have initializer
            // since this has already been diagnosed when parsing the variable
            // declaration.
            if (!Var->getInit() || !isa<ImplicitCastExpr>(Var->getInit()))
              break;
            Init = cast<ImplicitCastExpr>(const_cast<Expr*>(
              Var->getInit()))->getSubExpr();
            SourceType = Init->getType();
          }
        } else {
          // Case 2
          // Check initializer is 32 bit integer constant.
          // If the initializer is taken from global variable, do not diagnose since
          // this has already been done when parsing the variable declaration.
          if (!Init->isConstantInitializer(S.Context, false))
            break;
  
          if (!SourceType->isIntegerType() ||
              32 != S.Context.getIntWidth(SourceType)) {
            S.Diag(Kind.getLocation(), diag::err_sampler_initializer_not_integer)
              << SourceType;
            break;
          }
  
          Expr::EvalResult EVResult;
          Init->EvaluateAsInt(EVResult, S.Context);
          llvm::APSInt Result = EVResult.Val.getInt();
          const uint64_t SamplerValue = Result.getLimitedValue();
          // 32-bit value of sampler's initializer is interpreted as
          // bit-field with the following structure:
          // |unspecified|Filter|Addressing Mode| Normalized Coords|
          // |31        6|5    4|3             1|                 0|
          // This structure corresponds to enum values of sampler properties
          // defined in SPIR spec v1.2 and also opencl-c.h
          unsigned AddressingMode  = (0x0E & SamplerValue) >> 1;
          unsigned FilterMode      = (0x30 & SamplerValue) >> 4;
          if (FilterMode != 1 && FilterMode != 2 &&
              !S.getOpenCLOptions().isEnabled(
                  "cl_intel_device_side_avc_motion_estimation"))
            S.Diag(Kind.getLocation(),
                   diag::warn_sampler_initializer_invalid_bits)
                   << "Filter Mode";
          if (AddressingMode > 4)
            S.Diag(Kind.getLocation(),
                   diag::warn_sampler_initializer_invalid_bits)
                   << "Addressing Mode";
        }
  
        // Cases 1a, 2a and 2b
        // Insert cast from integer to sampler.
        CurInit = S.ImpCastExprToType(Init, S.Context.OCLSamplerTy,
                                        CK_IntToOCLSampler);
        break;
      }
      case SK_OCLZeroOpaqueType: {
        assert((Step->Type->isEventT() || Step->Type->isQueueT() ||
                Step->Type->isOCLIntelSubgroupAVCType()) &&
               "Wrong type for initialization of OpenCL opaque type.");
  
        CurInit = S.ImpCastExprToType(CurInit.get(), Step->Type,
                                      CK_ZeroToOCLOpaqueType,
                                      CurInit.get()->getValueKind());
        break;
      }
      }
    }
  
    // Check whether the initializer has a shorter lifetime than the initialized
    // entity, and if not, either lifetime-extend or warn as appropriate.
    if (auto *Init = CurInit.get())
      S.checkInitializerLifetime(Entity, Init);
  
    // Diagnose non-fatal problems with the completed initialization.
    if (Entity.getKind() == InitializedEntity::EK_Member &&
        cast<FieldDecl>(Entity.getDecl())->isBitField())
      S.CheckBitFieldInitialization(Kind.getLocation(),
                                    cast<FieldDecl>(Entity.getDecl()),
                                    CurInit.get());
  
    // Check for std::move on construction.
    if (const Expr *E = CurInit.get()) {
      CheckMoveOnConstruction(S, E,
                              Entity.getKind() == InitializedEntity::EK_Result);
    }
  
    return CurInit;
  }
  
  /// Somewhere within T there is an uninitialized reference subobject.
  /// Dig it out and diagnose it.
  static bool DiagnoseUninitializedReference(Sema &S, SourceLocation Loc,
                                             QualType T) {
    if (T->isReferenceType()) {
      S.Diag(Loc, diag::err_reference_without_init)
        << T.getNonReferenceType();
      return true;
    }
  
    CXXRecordDecl *RD = T->getBaseElementTypeUnsafe()->getAsCXXRecordDecl();
    if (!RD || !RD->hasUninitializedReferenceMember())
      return false;
  
    for (const auto *FI : RD->fields()) {
      if (FI->isUnnamedBitfield())
        continue;
  
      if (DiagnoseUninitializedReference(S, FI->getLocation(), FI->getType())) {
        S.Diag(Loc, diag::note_value_initialization_here) << RD;
        return true;
      }
    }
  
    for (const auto &BI : RD->bases()) {
      if (DiagnoseUninitializedReference(S, BI.getBeginLoc(), BI.getType())) {
        S.Diag(Loc, diag::note_value_initialization_here) << RD;
        return true;
      }
    }
  
    return false;
  }
  
  
  //===----------------------------------------------------------------------===//
  // Diagnose initialization failures
  //===----------------------------------------------------------------------===//
  
  /// Emit notes associated with an initialization that failed due to a
  /// "simple" conversion failure.
  static void emitBadConversionNotes(Sema &S, const InitializedEntity &entity,
                                     Expr *op) {
    QualType destType = entity.getType();
    if (destType.getNonReferenceType()->isObjCObjectPointerType() &&
        op->getType()->isObjCObjectPointerType()) {
  
      // Emit a possible note about the conversion failing because the
      // operand is a message send with a related result type.
      S.EmitRelatedResultTypeNote(op);
  
      // Emit a possible note about a return failing because we're
      // expecting a related result type.
      if (entity.getKind() == InitializedEntity::EK_Result)
        S.EmitRelatedResultTypeNoteForReturn(destType);
    }
  }
  
  static void diagnoseListInit(Sema &S, const InitializedEntity &Entity,
                               InitListExpr *InitList) {
    QualType DestType = Entity.getType();
  
    QualType E;
    if (S.getLangOpts().CPlusPlus11 && S.isStdInitializerList(DestType, &E)) {
      QualType ArrayType = S.Context.getConstantArrayType(
          E.withConst(),
          llvm::APInt(S.Context.getTypeSize(S.Context.getSizeType()),
                      InitList->getNumInits()),
          nullptr, clang::ArrayType::Normal, 0);
      InitializedEntity HiddenArray =
          InitializedEntity::InitializeTemporary(ArrayType);
      return diagnoseListInit(S, HiddenArray, InitList);
    }
  
    if (DestType->isReferenceType()) {
      // A list-initialization failure for a reference means that we tried to
      // create a temporary of the inner type (per [dcl.init.list]p3.6) and the
      // inner initialization failed.
      QualType T = DestType->castAs<ReferenceType>()->getPointeeType();
      diagnoseListInit(S, InitializedEntity::InitializeTemporary(T), InitList);
      SourceLocation Loc = InitList->getBeginLoc();
      if (auto *D = Entity.getDecl())
        Loc = D->getLocation();
      S.Diag(Loc, diag::note_in_reference_temporary_list_initializer) << T;
      return;
    }
  
    InitListChecker DiagnoseInitList(S, Entity, InitList, DestType,
                                     /*VerifyOnly=*/false,
                                     /*TreatUnavailableAsInvalid=*/false);
    assert(DiagnoseInitList.HadError() &&
           "Inconsistent init list check result.");
  }
  
  bool InitializationSequence::Diagnose(Sema &S,
                                        const InitializedEntity &Entity,
                                        const InitializationKind &Kind,
                                        ArrayRef<Expr *> Args) {
    if (!Failed())
      return false;
  
    // When we want to diagnose only one element of a braced-init-list,
    // we need to factor it out.
    Expr *OnlyArg;
    if (Args.size() == 1) {
      auto *List = dyn_cast<InitListExpr>(Args[0]);
      if (List && List->getNumInits() == 1)
        OnlyArg = List->getInit(0);
      else
        OnlyArg = Args[0];
    }
    else
      OnlyArg = nullptr;
  
    QualType DestType = Entity.getType();
    switch (Failure) {
    case FK_TooManyInitsForReference:
      // FIXME: Customize for the initialized entity?
      if (Args.empty()) {
        // Dig out the reference subobject which is uninitialized and diagnose it.
        // If this is value-initialization, this could be nested some way within
        // the target type.
        assert(Kind.getKind() == InitializationKind::IK_Value ||
               DestType->isReferenceType());
        bool Diagnosed =
          DiagnoseUninitializedReference(S, Kind.getLocation(), DestType);
        assert(Diagnosed && "couldn't find uninitialized reference to diagnose");
        (void)Diagnosed;
      } else  // FIXME: diagnostic below could be better!
        S.Diag(Kind.getLocation(), diag::err_reference_has_multiple_inits)
            << SourceRange(Args.front()->getBeginLoc(), Args.back()->getEndLoc());
      break;
    case FK_ParenthesizedListInitForReference:
      S.Diag(Kind.getLocation(), diag::err_list_init_in_parens)
        << 1 << Entity.getType() << Args[0]->getSourceRange();
      break;
  
    case FK_ArrayNeedsInitList:
      S.Diag(Kind.getLocation(), diag::err_array_init_not_init_list) << 0;
      break;
    case FK_ArrayNeedsInitListOrStringLiteral:
      S.Diag(Kind.getLocation(), diag::err_array_init_not_init_list) << 1;
      break;
    case FK_ArrayNeedsInitListOrWideStringLiteral:
      S.Diag(Kind.getLocation(), diag::err_array_init_not_init_list) << 2;
      break;
    case FK_NarrowStringIntoWideCharArray:
      S.Diag(Kind.getLocation(), diag::err_array_init_narrow_string_into_wchar);
      break;
    case FK_WideStringIntoCharArray:
      S.Diag(Kind.getLocation(), diag::err_array_init_wide_string_into_char);
      break;
    case FK_IncompatWideStringIntoWideChar:
      S.Diag(Kind.getLocation(),
             diag::err_array_init_incompat_wide_string_into_wchar);
      break;
    case FK_PlainStringIntoUTF8Char:
      S.Diag(Kind.getLocation(),
             diag::err_array_init_plain_string_into_char8_t);
      S.Diag(Args.front()->getBeginLoc(),
             diag::note_array_init_plain_string_into_char8_t)
          << FixItHint::CreateInsertion(Args.front()->getBeginLoc(), "u8");
      break;
    case FK_UTF8StringIntoPlainChar:
      S.Diag(Kind.getLocation(),
             diag::err_array_init_utf8_string_into_char)
        << S.getLangOpts().CPlusPlus20;
      break;
    case FK_ArrayTypeMismatch:
    case FK_NonConstantArrayInit:
      S.Diag(Kind.getLocation(),
             (Failure == FK_ArrayTypeMismatch
                ? diag::err_array_init_different_type
                : diag::err_array_init_non_constant_array))
        << DestType.getNonReferenceType()
        << OnlyArg->getType()
        << Args[0]->getSourceRange();
      break;
  
    case FK_VariableLengthArrayHasInitializer:
      S.Diag(Kind.getLocation(), diag::err_variable_object_no_init)
        << Args[0]->getSourceRange();
      break;
  
    case FK_AddressOfOverloadFailed: {
      DeclAccessPair Found;
      S.ResolveAddressOfOverloadedFunction(OnlyArg,
                                           DestType.getNonReferenceType(),
                                           true,
                                           Found);
      break;
    }
  
    case FK_AddressOfUnaddressableFunction: {
      auto *FD = cast<FunctionDecl>(cast<DeclRefExpr>(OnlyArg)->getDecl());
      S.checkAddressOfFunctionIsAvailable(FD, /*Complain=*/true,
                                          OnlyArg->getBeginLoc());
      break;
    }
  
    case FK_ReferenceInitOverloadFailed:
    case FK_UserConversionOverloadFailed:
      switch (FailedOverloadResult) {
      case OR_Ambiguous:
  
        FailedCandidateSet.NoteCandidates(
            PartialDiagnosticAt(
                Kind.getLocation(),
                Failure == FK_UserConversionOverloadFailed
                    ? (S.PDiag(diag::err_typecheck_ambiguous_condition)
                       << OnlyArg->getType() << DestType
                       << Args[0]->getSourceRange())
                    : (S.PDiag(diag::err_ref_init_ambiguous)
                       << DestType << OnlyArg->getType()
                       << Args[0]->getSourceRange())),
            S, OCD_AmbiguousCandidates, Args);
        break;
  
      case OR_No_Viable_Function: {
        auto Cands = FailedCandidateSet.CompleteCandidates(S, OCD_AllCandidates, Args);
        if (!S.RequireCompleteType(Kind.getLocation(),
                                   DestType.getNonReferenceType(),
                            diag::err_typecheck_nonviable_condition_incomplete,
                                 OnlyArg->getType(), Args[0]->getSourceRange()))
          S.Diag(Kind.getLocation(), diag::err_typecheck_nonviable_condition)
            << (Entity.getKind() == InitializedEntity::EK_Result)
            << OnlyArg->getType() << Args[0]->getSourceRange()
            << DestType.getNonReferenceType();
  
        FailedCandidateSet.NoteCandidates(S, Args, Cands);
        break;
      }
      case OR_Deleted: {
        S.Diag(Kind.getLocation(), diag::err_typecheck_deleted_function)
          << OnlyArg->getType() << DestType.getNonReferenceType()
          << Args[0]->getSourceRange();
        OverloadCandidateSet::iterator Best;
        OverloadingResult Ovl
          = FailedCandidateSet.BestViableFunction(S, Kind.getLocation(), Best);
        if (Ovl == OR_Deleted) {
          S.NoteDeletedFunction(Best->Function);
        } else {
          llvm_unreachable("Inconsistent overload resolution?");
        }
        break;
      }
  
      case OR_Success:
        llvm_unreachable("Conversion did not fail!");
      }
      break;
  
    case FK_NonConstLValueReferenceBindingToTemporary:
      if (isa<InitListExpr>(Args[0])) {
        S.Diag(Kind.getLocation(),
               diag::err_lvalue_reference_bind_to_initlist)
        << DestType.getNonReferenceType().isVolatileQualified()
        << DestType.getNonReferenceType()
        << Args[0]->getSourceRange();
        break;
      }
      LLVM_FALLTHROUGH;
  
    case FK_NonConstLValueReferenceBindingToUnrelated:
      S.Diag(Kind.getLocation(),
             Failure == FK_NonConstLValueReferenceBindingToTemporary
               ? diag::err_lvalue_reference_bind_to_temporary
               : diag::err_lvalue_reference_bind_to_unrelated)
        << DestType.getNonReferenceType().isVolatileQualified()
        << DestType.getNonReferenceType()
        << OnlyArg->getType()
        << Args[0]->getSourceRange();
      break;
  
    case FK_NonConstLValueReferenceBindingToBitfield: {
      // We don't necessarily have an unambiguous source bit-field.
      FieldDecl *BitField = Args[0]->getSourceBitField();
      S.Diag(Kind.getLocation(), diag::err_reference_bind_to_bitfield)
        << DestType.isVolatileQualified()
        << (BitField ? BitField->getDeclName() : DeclarationName())
        << (BitField != nullptr)
        << Args[0]->getSourceRange();
      if (BitField)
        S.Diag(BitField->getLocation(), diag::note_bitfield_decl);
      break;
    }
  
    case FK_NonConstLValueReferenceBindingToVectorElement:
      S.Diag(Kind.getLocation(), diag::err_reference_bind_to_vector_element)
        << DestType.isVolatileQualified()
        << Args[0]->getSourceRange();
      break;
  
    case FK_NonConstLValueReferenceBindingToMatrixElement:
      S.Diag(Kind.getLocation(), diag::err_reference_bind_to_matrix_element)
          << DestType.isVolatileQualified() << Args[0]->getSourceRange();
      break;
  
    case FK_RValueReferenceBindingToLValue:
      S.Diag(Kind.getLocation(), diag::err_lvalue_to_rvalue_ref)
        << DestType.getNonReferenceType() << OnlyArg->getType()
        << Args[0]->getSourceRange();
      break;
  
    case FK_ReferenceAddrspaceMismatchTemporary:
      S.Diag(Kind.getLocation(), diag::err_reference_bind_temporary_addrspace)
          << DestType << Args[0]->getSourceRange();
      break;
  
    case FK_ReferenceInitDropsQualifiers: {
      QualType SourceType = OnlyArg->getType();
      QualType NonRefType = DestType.getNonReferenceType();
      Qualifiers DroppedQualifiers =
          SourceType.getQualifiers() - NonRefType.getQualifiers();
  
      if (!NonRefType.getQualifiers().isAddressSpaceSupersetOf(
              SourceType.getQualifiers()))
        S.Diag(Kind.getLocation(), diag::err_reference_bind_drops_quals)
            << NonRefType << SourceType << 1 /*addr space*/
            << Args[0]->getSourceRange();
      else if (DroppedQualifiers.hasQualifiers())
        S.Diag(Kind.getLocation(), diag::err_reference_bind_drops_quals)
            << NonRefType << SourceType << 0 /*cv quals*/
            << Qualifiers::fromCVRMask(DroppedQualifiers.getCVRQualifiers())
            << DroppedQualifiers.getCVRQualifiers() << Args[0]->getSourceRange();
      else
        // FIXME: Consider decomposing the type and explaining which qualifiers
        // were dropped where, or on which level a 'const' is missing, etc.
        S.Diag(Kind.getLocation(), diag::err_reference_bind_drops_quals)
            << NonRefType << SourceType << 2 /*incompatible quals*/
            << Args[0]->getSourceRange();
      break;
    }
  
    case FK_ReferenceInitFailed:
      S.Diag(Kind.getLocation(), diag::err_reference_bind_failed)
        << DestType.getNonReferenceType()
        << DestType.getNonReferenceType()->isIncompleteType()
        << OnlyArg->isLValue()
        << OnlyArg->getType()
        << Args[0]->getSourceRange();
      emitBadConversionNotes(S, Entity, Args[0]);
      break;
  
    case FK_ConversionFailed: {
      QualType FromType = OnlyArg->getType();
      PartialDiagnostic PDiag = S.PDiag(diag::err_init_conversion_failed)
        << (int)Entity.getKind()
        << DestType
        << OnlyArg->isLValue()
        << FromType
        << Args[0]->getSourceRange();
      S.HandleFunctionTypeMismatch(PDiag, FromType, DestType);
      S.Diag(Kind.getLocation(), PDiag);
      emitBadConversionNotes(S, Entity, Args[0]);
      break;
    }
  
    case FK_ConversionFromPropertyFailed:
      // No-op. This error has already been reported.
      break;
  
    case FK_TooManyInitsForScalar: {
      SourceRange R;
  
      auto *InitList = dyn_cast<InitListExpr>(Args[0]);
      if (InitList && InitList->getNumInits() >= 1) {
        R = SourceRange(InitList->getInit(0)->getEndLoc(), InitList->getEndLoc());
      } else {
        assert(Args.size() > 1 && "Expected multiple initializers!");
        R = SourceRange(Args.front()->getEndLoc(), Args.back()->getEndLoc());
      }
  
      R.setBegin(S.getLocForEndOfToken(R.getBegin()));
      if (Kind.isCStyleOrFunctionalCast())
        S.Diag(Kind.getLocation(), diag::err_builtin_func_cast_more_than_one_arg)
          << R;
      else
        S.Diag(Kind.getLocation(), diag::err_excess_initializers)
          << /*scalar=*/2 << R;
      break;
    }
  
    case FK_ParenthesizedListInitForScalar:
      S.Diag(Kind.getLocation(), diag::err_list_init_in_parens)
        << 0 << Entity.getType() << Args[0]->getSourceRange();
      break;
  
    case FK_ReferenceBindingToInitList:
      S.Diag(Kind.getLocation(), diag::err_reference_bind_init_list)
        << DestType.getNonReferenceType() << Args[0]->getSourceRange();
      break;
  
    case FK_InitListBadDestinationType:
      S.Diag(Kind.getLocation(), diag::err_init_list_bad_dest_type)
        << (DestType->isRecordType()) << DestType << Args[0]->getSourceRange();
      break;
  
    case FK_ListConstructorOverloadFailed:
    case FK_ConstructorOverloadFailed: {
      SourceRange ArgsRange;
      if (Args.size())
        ArgsRange =
            SourceRange(Args.front()->getBeginLoc(), Args.back()->getEndLoc());
  
      if (Failure == FK_ListConstructorOverloadFailed) {
        assert(Args.size() == 1 &&
               "List construction from other than 1 argument.");
        InitListExpr *InitList = cast<InitListExpr>(Args[0]);
        Args = MultiExprArg(InitList->getInits(), InitList->getNumInits());
      }
  
      // FIXME: Using "DestType" for the entity we're printing is probably
      // bad.
      switch (FailedOverloadResult) {
        case OR_Ambiguous:
          FailedCandidateSet.NoteCandidates(
              PartialDiagnosticAt(Kind.getLocation(),
                                  S.PDiag(diag::err_ovl_ambiguous_init)
                                      << DestType << ArgsRange),
              S, OCD_AmbiguousCandidates, Args);
          break;
  
        case OR_No_Viable_Function:
          if (Kind.getKind() == InitializationKind::IK_Default &&
              (Entity.getKind() == InitializedEntity::EK_Base ||
               Entity.getKind() == InitializedEntity::EK_Member) &&
              isa<CXXConstructorDecl>(S.CurContext)) {
            // This is implicit default initialization of a member or
            // base within a constructor. If no viable function was
            // found, notify the user that they need to explicitly
            // initialize this base/member.
            CXXConstructorDecl *Constructor
              = cast<CXXConstructorDecl>(S.CurContext);
            const CXXRecordDecl *InheritedFrom = nullptr;
            if (auto Inherited = Constructor->getInheritedConstructor())
              InheritedFrom = Inherited.getShadowDecl()->getNominatedBaseClass();
            if (Entity.getKind() == InitializedEntity::EK_Base) {
              S.Diag(Kind.getLocation(), diag::err_missing_default_ctor)
                << (InheritedFrom ? 2 : Constructor->isImplicit() ? 1 : 0)
                << S.Context.getTypeDeclType(Constructor->getParent())
                << /*base=*/0
                << Entity.getType()
                << InheritedFrom;
  
              RecordDecl *BaseDecl
                = Entity.getBaseSpecifier()->getType()->castAs<RecordType>()
                                                                    ->getDecl();
              S.Diag(BaseDecl->getLocation(), diag::note_previous_decl)
                << S.Context.getTagDeclType(BaseDecl);
            } else {
              S.Diag(Kind.getLocation(), diag::err_missing_default_ctor)
                << (InheritedFrom ? 2 : Constructor->isImplicit() ? 1 : 0)
                << S.Context.getTypeDeclType(Constructor->getParent())
                << /*member=*/1
                << Entity.getName()
                << InheritedFrom;
              S.Diag(Entity.getDecl()->getLocation(),
                     diag::note_member_declared_at);
  
              if (const RecordType *Record
                                   = Entity.getType()->getAs<RecordType>())
                S.Diag(Record->getDecl()->getLocation(),
                       diag::note_previous_decl)
                  << S.Context.getTagDeclType(Record->getDecl());
            }
            break;
          }
  
          FailedCandidateSet.NoteCandidates(
              PartialDiagnosticAt(
                  Kind.getLocation(),
                  S.PDiag(diag::err_ovl_no_viable_function_in_init)
                      << DestType << ArgsRange),
              S, OCD_AllCandidates, Args);
          break;
  
        case OR_Deleted: {
          OverloadCandidateSet::iterator Best;
          OverloadingResult Ovl
            = FailedCandidateSet.BestViableFunction(S, Kind.getLocation(), Best);
          if (Ovl != OR_Deleted) {
            S.Diag(Kind.getLocation(), diag::err_ovl_deleted_init)
                << DestType << ArgsRange;
            llvm_unreachable("Inconsistent overload resolution?");
            break;
          }
  
          // If this is a defaulted or implicitly-declared function, then
          // it was implicitly deleted. Make it clear that the deletion was
          // implicit.
          if (S.isImplicitlyDeleted(Best->Function))
            S.Diag(Kind.getLocation(), diag::err_ovl_deleted_special_init)
              << S.getSpecialMember(cast<CXXMethodDecl>(Best->Function))
              << DestType << ArgsRange;
          else
            S.Diag(Kind.getLocation(), diag::err_ovl_deleted_init)
                << DestType << ArgsRange;
  
          S.NoteDeletedFunction(Best->Function);
          break;
        }
  
        case OR_Success:
          llvm_unreachable("Conversion did not fail!");
      }
    }
    break;
  
    case FK_DefaultInitOfConst:
      if (Entity.getKind() == InitializedEntity::EK_Member &&
          isa<CXXConstructorDecl>(S.CurContext)) {
        // This is implicit default-initialization of a const member in
        // a constructor. Complain that it needs to be explicitly
        // initialized.
        CXXConstructorDecl *Constructor = cast<CXXConstructorDecl>(S.CurContext);
        S.Diag(Kind.getLocation(), diag::err_uninitialized_member_in_ctor)
          << (Constructor->getInheritedConstructor() ? 2 :
              Constructor->isImplicit() ? 1 : 0)
          << S.Context.getTypeDeclType(Constructor->getParent())
          << /*const=*/1
          << Entity.getName();
        S.Diag(Entity.getDecl()->getLocation(), diag::note_previous_decl)
          << Entity.getName();
      } else {
        S.Diag(Kind.getLocation(), diag::err_default_init_const)
            << DestType << (bool)DestType->getAs<RecordType>();
      }
      break;
  
    case FK_Incomplete:
      S.RequireCompleteType(Kind.getLocation(), FailedIncompleteType,
                            diag::err_init_incomplete_type);
      break;
  
    case FK_ListInitializationFailed: {
      // Run the init list checker again to emit diagnostics.
      InitListExpr *InitList = cast<InitListExpr>(Args[0]);
      diagnoseListInit(S, Entity, InitList);
      break;
    }
  
    case FK_PlaceholderType: {
      // FIXME: Already diagnosed!
      break;
    }
  
    case FK_ExplicitConstructor: {
      S.Diag(Kind.getLocation(), diag::err_selected_explicit_constructor)
        << Args[0]->getSourceRange();
      OverloadCandidateSet::iterator Best;
      OverloadingResult Ovl
        = FailedCandidateSet.BestViableFunction(S, Kind.getLocation(), Best);
      (void)Ovl;
      assert(Ovl == OR_Success && "Inconsistent overload resolution");
      CXXConstructorDecl *CtorDecl = cast<CXXConstructorDecl>(Best->Function);
      S.Diag(CtorDecl->getLocation(),
             diag::note_explicit_ctor_deduction_guide_here) << false;
      break;
    }
    }
  
    PrintInitLocationNote(S, Entity);
    return true;
  }
  
  void InitializationSequence::dump(raw_ostream &OS) const {
    switch (SequenceKind) {
    case FailedSequence: {
      OS << "Failed sequence: ";
      switch (Failure) {
      case FK_TooManyInitsForReference:
        OS << "too many initializers for reference";
        break;
  
      case FK_ParenthesizedListInitForReference:
        OS << "parenthesized list init for reference";
        break;
  
      case FK_ArrayNeedsInitList:
        OS << "array requires initializer list";
        break;
  
      case FK_AddressOfUnaddressableFunction:
        OS << "address of unaddressable function was taken";
        break;
  
      case FK_ArrayNeedsInitListOrStringLiteral:
        OS << "array requires initializer list or string literal";
        break;
  
      case FK_ArrayNeedsInitListOrWideStringLiteral:
        OS << "array requires initializer list or wide string literal";
        break;
  
      case FK_NarrowStringIntoWideCharArray:
        OS << "narrow string into wide char array";
        break;
  
      case FK_WideStringIntoCharArray:
        OS << "wide string into char array";
        break;
  
      case FK_IncompatWideStringIntoWideChar:
        OS << "incompatible wide string into wide char array";
        break;
  
      case FK_PlainStringIntoUTF8Char:
        OS << "plain string literal into char8_t array";
        break;
  
      case FK_UTF8StringIntoPlainChar:
        OS << "u8 string literal into char array";
        break;
  
      case FK_ArrayTypeMismatch:
        OS << "array type mismatch";
        break;
  
      case FK_NonConstantArrayInit:
        OS << "non-constant array initializer";
        break;
  
      case FK_AddressOfOverloadFailed:
        OS << "address of overloaded function failed";
        break;
  
      case FK_ReferenceInitOverloadFailed:
        OS << "overload resolution for reference initialization failed";
        break;
  
      case FK_NonConstLValueReferenceBindingToTemporary:
        OS << "non-const lvalue reference bound to temporary";
        break;
  
      case FK_NonConstLValueReferenceBindingToBitfield:
        OS << "non-const lvalue reference bound to bit-field";
        break;
  
      case FK_NonConstLValueReferenceBindingToVectorElement:
        OS << "non-const lvalue reference bound to vector element";
        break;
  
      case FK_NonConstLValueReferenceBindingToMatrixElement:
        OS << "non-const lvalue reference bound to matrix element";
        break;
  
      case FK_NonConstLValueReferenceBindingToUnrelated:
        OS << "non-const lvalue reference bound to unrelated type";
        break;
  
      case FK_RValueReferenceBindingToLValue:
        OS << "rvalue reference bound to an lvalue";
        break;
  
      case FK_ReferenceInitDropsQualifiers:
        OS << "reference initialization drops qualifiers";
        break;
  
      case FK_ReferenceAddrspaceMismatchTemporary:
        OS << "reference with mismatching address space bound to temporary";
        break;
  
      case FK_ReferenceInitFailed:
        OS << "reference initialization failed";
        break;
  
      case FK_ConversionFailed:
        OS << "conversion failed";
        break;
  
      case FK_ConversionFromPropertyFailed:
        OS << "conversion from property failed";
        break;
  
      case FK_TooManyInitsForScalar:
        OS << "too many initializers for scalar";
        break;
  
      case FK_ParenthesizedListInitForScalar:
        OS << "parenthesized list init for reference";
        break;
  
      case FK_ReferenceBindingToInitList:
        OS << "referencing binding to initializer list";
        break;
  
      case FK_InitListBadDestinationType:
        OS << "initializer list for non-aggregate, non-scalar type";
        break;
  
      case FK_UserConversionOverloadFailed:
        OS << "overloading failed for user-defined conversion";
        break;
  
      case FK_ConstructorOverloadFailed:
        OS << "constructor overloading failed";
        break;
  
      case FK_DefaultInitOfConst:
        OS << "default initialization of a const variable";
        break;
  
      case FK_Incomplete:
        OS << "initialization of incomplete type";
        break;
  
      case FK_ListInitializationFailed:
        OS << "list initialization checker failure";
        break;
  
      case FK_VariableLengthArrayHasInitializer:
        OS << "variable length array has an initializer";
        break;
  
      case FK_PlaceholderType:
        OS << "initializer expression isn't contextually valid";
        break;
  
      case FK_ListConstructorOverloadFailed:
        OS << "list constructor overloading failed";
        break;
  
      case FK_ExplicitConstructor:
        OS << "list copy initialization chose explicit constructor";
        break;
      }
      OS << '\n';
      return;
    }
  
    case DependentSequence:
      OS << "Dependent sequence\n";
      return;
  
    case NormalSequence:
      OS << "Normal sequence: ";
      break;
    }
  
    for (step_iterator S = step_begin(), SEnd = step_end(); S != SEnd; ++S) {
      if (S != step_begin()) {
        OS << " -> ";
      }
  
      switch (S->Kind) {
      case SK_ResolveAddressOfOverloadedFunction:
        OS << "resolve address of overloaded function";
        break;
  
      case SK_CastDerivedToBaseRValue:
        OS << "derived-to-base (rvalue)";
        break;
  
      case SK_CastDerivedToBaseXValue:
        OS << "derived-to-base (xvalue)";
        break;
  
      case SK_CastDerivedToBaseLValue:
        OS << "derived-to-base (lvalue)";
        break;
  
      case SK_BindReference:
        OS << "bind reference to lvalue";
        break;
  
      case SK_BindReferenceToTemporary:
        OS << "bind reference to a temporary";
        break;
  
      case SK_FinalCopy:
        OS << "final copy in class direct-initialization";
        break;
  
      case SK_ExtraneousCopyToTemporary:
        OS << "extraneous C++03 copy to temporary";
        break;
  
      case SK_UserConversion:
        OS << "user-defined conversion via " << *S->Function.Function;
        break;
  
      case SK_QualificationConversionRValue:
        OS << "qualification conversion (rvalue)";
        break;
  
      case SK_QualificationConversionXValue:
        OS << "qualification conversion (xvalue)";
        break;
  
      case SK_QualificationConversionLValue:
        OS << "qualification conversion (lvalue)";
        break;
  
      case SK_AtomicConversion:
        OS << "non-atomic-to-atomic conversion";
        break;
  
      case SK_ConversionSequence:
        OS << "implicit conversion sequence (";
        S->ICS->dump(); // FIXME: use OS
        OS << ")";
        break;
  
      case SK_ConversionSequenceNoNarrowing:
        OS << "implicit conversion sequence with narrowing prohibited (";
        S->ICS->dump(); // FIXME: use OS
        OS << ")";
        break;
  
      case SK_ListInitialization:
        OS << "list aggregate initialization";
        break;
  
      case SK_UnwrapInitList:
        OS << "unwrap reference initializer list";
        break;
  
      case SK_RewrapInitList:
        OS << "rewrap reference initializer list";
        break;
  
      case SK_ConstructorInitialization:
        OS << "constructor initialization";
        break;
  
      case SK_ConstructorInitializationFromList:
        OS << "list initialization via constructor";
        break;
  
      case SK_ZeroInitialization:
        OS << "zero initialization";
        break;
  
      case SK_CAssignment:
        OS << "C assignment";
        break;
  
      case SK_StringInit:
        OS << "string initialization";
        break;
  
      case SK_ObjCObjectConversion:
        OS << "Objective-C object conversion";
        break;
  
      case SK_ArrayLoopIndex:
        OS << "indexing for array initialization loop";
        break;
  
      case SK_ArrayLoopInit:
        OS << "array initialization loop";
        break;
  
      case SK_ArrayInit:
        OS << "array initialization";
        break;
  
      case SK_GNUArrayInit:
        OS << "array initialization (GNU extension)";
        break;
  
      case SK_ParenthesizedArrayInit:
        OS << "parenthesized array initialization";
        break;
  
      case SK_PassByIndirectCopyRestore:
        OS << "pass by indirect copy and restore";
        break;
  
      case SK_PassByIndirectRestore:
        OS << "pass by indirect restore";
        break;
  
      case SK_ProduceObjCObject:
        OS << "Objective-C object retension";
        break;
  
      case SK_StdInitializerList:
        OS << "std::initializer_list from initializer list";
        break;
  
      case SK_StdInitializerListConstructorCall:
        OS << "list initialization from std::initializer_list";
        break;
  
      case SK_OCLSamplerInit:
        OS << "OpenCL sampler_t from integer constant";
        break;
  
      case SK_OCLZeroOpaqueType:
        OS << "OpenCL opaque type from zero";
        break;
      }
  
      OS << " [" << S->Type.getAsString() << ']';
    }
  
    OS << '\n';
  }
  
  void InitializationSequence::dump() const {
    dump(llvm::errs());
  }
  
  static bool NarrowingErrs(const LangOptions &L) {
    return L.CPlusPlus11 &&
           (!L.MicrosoftExt || L.isCompatibleWithMSVC(LangOptions::MSVC2015));
  }
  
  static void DiagnoseNarrowingInInitList(Sema &S,
                                          const ImplicitConversionSequence &ICS,
                                          QualType PreNarrowingType,
                                          QualType EntityType,
                                          const Expr *PostInit) {
    const StandardConversionSequence *SCS = nullptr;
    switch (ICS.getKind()) {
    case ImplicitConversionSequence::StandardConversion:
      SCS = &ICS.Standard;
      break;
    case ImplicitConversionSequence::UserDefinedConversion:
      SCS = &ICS.UserDefined.After;
      break;
    case ImplicitConversionSequence::AmbiguousConversion:
    case ImplicitConversionSequence::EllipsisConversion:
    case ImplicitConversionSequence::BadConversion:
      return;
    }
  
    // C++11 [dcl.init.list]p7: Check whether this is a narrowing conversion.
    APValue ConstantValue;
    QualType ConstantType;
    switch (SCS->getNarrowingKind(S.Context, PostInit, ConstantValue,
                                  ConstantType)) {
    case NK_Not_Narrowing:
    case NK_Dependent_Narrowing:
      // No narrowing occurred.
      return;
  
    case NK_Type_Narrowing:
      // This was a floating-to-integer conversion, which is always considered a
      // narrowing conversion even if the value is a constant and can be
      // represented exactly as an integer.
      S.Diag(PostInit->getBeginLoc(), NarrowingErrs(S.getLangOpts())
                                          ? diag::ext_init_list_type_narrowing
                                          : diag::warn_init_list_type_narrowing)
          << PostInit->getSourceRange()
          << PreNarrowingType.getLocalUnqualifiedType()
          << EntityType.getLocalUnqualifiedType();
      break;
  
    case NK_Constant_Narrowing:
      // A constant value was narrowed.
      S.Diag(PostInit->getBeginLoc(),
             NarrowingErrs(S.getLangOpts())
                 ? diag::ext_init_list_constant_narrowing
                 : diag::warn_init_list_constant_narrowing)
          << PostInit->getSourceRange()
          << ConstantValue.getAsString(S.getASTContext(), ConstantType)
          << EntityType.getLocalUnqualifiedType();
      break;
  
    case NK_Variable_Narrowing:
      // A variable's value may have been narrowed.
      S.Diag(PostInit->getBeginLoc(),
             NarrowingErrs(S.getLangOpts())
                 ? diag::ext_init_list_variable_narrowing
                 : diag::warn_init_list_variable_narrowing)
          << PostInit->getSourceRange()
          << PreNarrowingType.getLocalUnqualifiedType()
          << EntityType.getLocalUnqualifiedType();
      break;
    }
  
    SmallString<128> StaticCast;
    llvm::raw_svector_ostream OS(StaticCast);
    OS << "static_cast<";
    if (const TypedefType *TT = EntityType->getAs<TypedefType>()) {
      // It's important to use the typedef's name if there is one so that the
      // fixit doesn't break code using types like int64_t.
      //
      // FIXME: This will break if the typedef requires qualification.  But
      // getQualifiedNameAsString() includes non-machine-parsable components.
      OS << *TT->getDecl();
    } else if (const BuiltinType *BT = EntityType->getAs<BuiltinType>())
      OS << BT->getName(S.getLangOpts());
    else {
      // Oops, we didn't find the actual type of the variable.  Don't emit a fixit
      // with a broken cast.
      return;
    }
    OS << ">(";
    S.Diag(PostInit->getBeginLoc(), diag::note_init_list_narrowing_silence)
        << PostInit->getSourceRange()
        << FixItHint::CreateInsertion(PostInit->getBeginLoc(), OS.str())
        << FixItHint::CreateInsertion(
               S.getLocForEndOfToken(PostInit->getEndLoc()), ")");
  }
  
  //===----------------------------------------------------------------------===//
  // Initialization helper functions
  //===----------------------------------------------------------------------===//
  bool
  Sema::CanPerformCopyInitialization(const InitializedEntity &Entity,
                                     ExprResult Init) {
    if (Init.isInvalid())
      return false;
  
    Expr *InitE = Init.get();
    assert(InitE && "No initialization expression");
  
    InitializationKind Kind =
        InitializationKind::CreateCopy(InitE->getBeginLoc(), SourceLocation());
    InitializationSequence Seq(*this, Entity, Kind, InitE);
    return !Seq.Failed();
  }
  
  ExprResult
  Sema::PerformCopyInitialization(const InitializedEntity &Entity,
                                  SourceLocation EqualLoc,
                                  ExprResult Init,
                                  bool TopLevelOfInitList,
                                  bool AllowExplicit) {
    if (Init.isInvalid())
      return ExprError();
  
    Expr *InitE = Init.get();
    assert(InitE && "No initialization expression?");
  
    if (EqualLoc.isInvalid())
      EqualLoc = InitE->getBeginLoc();
  
    InitializationKind Kind = InitializationKind::CreateCopy(
        InitE->getBeginLoc(), EqualLoc, AllowExplicit);
    InitializationSequence Seq(*this, Entity, Kind, InitE, TopLevelOfInitList);
  
    // Prevent infinite recursion when performing parameter copy-initialization.
    const bool ShouldTrackCopy =
        Entity.isParameterKind() && Seq.isConstructorInitialization();
    if (ShouldTrackCopy) {
      if (llvm::find(CurrentParameterCopyTypes, Entity.getType()) !=
          CurrentParameterCopyTypes.end()) {
        Seq.SetOverloadFailure(
            InitializationSequence::FK_ConstructorOverloadFailed,
            OR_No_Viable_Function);
  
        // Try to give a meaningful diagnostic note for the problematic
        // constructor.
        const auto LastStep = Seq.step_end() - 1;
        assert(LastStep->Kind ==
               InitializationSequence::SK_ConstructorInitialization);
        const FunctionDecl *Function = LastStep->Function.Function;
        auto Candidate =
            llvm::find_if(Seq.getFailedCandidateSet(),
                          [Function](const OverloadCandidate &Candidate) -> bool {
                            return Candidate.Viable &&
                                   Candidate.Function == Function &&
                                   Candidate.Conversions.size() > 0;
                          });
        if (Candidate != Seq.getFailedCandidateSet().end() &&
            Function->getNumParams() > 0) {
          Candidate->Viable = false;
          Candidate->FailureKind = ovl_fail_bad_conversion;
          Candidate->Conversions[0].setBad(BadConversionSequence::no_conversion,
                                           InitE,
                                           Function->getParamDecl(0)->getType());
        }
      }
      CurrentParameterCopyTypes.push_back(Entity.getType());
    }
  
    ExprResult Result = Seq.Perform(*this, Entity, Kind, InitE);
  
    if (ShouldTrackCopy)
      CurrentParameterCopyTypes.pop_back();
  
    return Result;
  }
  
  /// Determine whether RD is, or is derived from, a specialization of CTD.
  static bool isOrIsDerivedFromSpecializationOf(CXXRecordDecl *RD,
                                                ClassTemplateDecl *CTD) {
    auto NotSpecialization = [&] (const CXXRecordDecl *Candidate) {
      auto *CTSD = dyn_cast<ClassTemplateSpecializationDecl>(Candidate);
      return !CTSD || !declaresSameEntity(CTSD->getSpecializedTemplate(), CTD);
    };
    return !(NotSpecialization(RD) && RD->forallBases(NotSpecialization));
  }
  
  QualType Sema::DeduceTemplateSpecializationFromInitializer(
      TypeSourceInfo *TSInfo, const InitializedEntity &Entity,
      const InitializationKind &Kind, MultiExprArg Inits) {
    auto *DeducedTST = dyn_cast<DeducedTemplateSpecializationType>(
        TSInfo->getType()->getContainedDeducedType());
    assert(DeducedTST && "not a deduced template specialization type");
  
    auto TemplateName = DeducedTST->getTemplateName();
    if (TemplateName.isDependent())
      return Context.DependentTy;
  
    // We can only perform deduction for class templates.
    auto *Template =
        dyn_cast_or_null<ClassTemplateDecl>(TemplateName.getAsTemplateDecl());
    if (!Template) {
      Diag(Kind.getLocation(),
           diag::err_deduced_non_class_template_specialization_type)
        << (int)getTemplateNameKindForDiagnostics(TemplateName) << TemplateName;
      if (auto *TD = TemplateName.getAsTemplateDecl())
        Diag(TD->getLocation(), diag::note_template_decl_here);
      return QualType();
    }
  
    // Can't deduce from dependent arguments.
    if (Expr::hasAnyTypeDependentArguments(Inits)) {
      Diag(TSInfo->getTypeLoc().getBeginLoc(),
           diag::warn_cxx14_compat_class_template_argument_deduction)
          << TSInfo->getTypeLoc().getSourceRange() << 0;
      return Context.DependentTy;
    }
  
    // FIXME: Perform "exact type" matching first, per CWG discussion?
    //        Or implement this via an implied 'T(T) -> T' deduction guide?
  
    // FIXME: Do we need/want a std::initializer_list<T> special case?
  
    // Look up deduction guides, including those synthesized from constructors.
    //
    // C++1z [over.match.class.deduct]p1:
    //   A set of functions and function templates is formed comprising:
    //   - For each constructor of the class template designated by the
    //     template-name, a function template [...]
    //  - For each deduction-guide, a function or function template [...]
    DeclarationNameInfo NameInfo(
        Context.DeclarationNames.getCXXDeductionGuideName(Template),
        TSInfo->getTypeLoc().getEndLoc());
    LookupResult Guides(*this, NameInfo, LookupOrdinaryName);
    LookupQualifiedName(Guides, Template->getDeclContext());
  
    // FIXME: Do not diagnose inaccessible deduction guides. The standard isn't
    // clear on this, but they're not found by name so access does not apply.
    Guides.suppressDiagnostics();
  
    // Figure out if this is list-initialization.
    InitListExpr *ListInit =
        (Inits.size() == 1 && Kind.getKind() != InitializationKind::IK_Direct)
            ? dyn_cast<InitListExpr>(Inits[0])
            : nullptr;
  
    // C++1z [over.match.class.deduct]p1:
    //   Initialization and overload resolution are performed as described in
    //   [dcl.init] and [over.match.ctor], [over.match.copy], or [over.match.list]
    //   (as appropriate for the type of initialization performed) for an object
    //   of a hypothetical class type, where the selected functions and function
    //   templates are considered to be the constructors of that class type
    //
    // Since we know we're initializing a class type of a type unrelated to that
    // of the initializer, this reduces to something fairly reasonable.
    OverloadCandidateSet Candidates(Kind.getLocation(),
                                    OverloadCandidateSet::CSK_Normal);
    OverloadCandidateSet::iterator Best;
  
    bool HasAnyDeductionGuide = false;
    bool AllowExplicit = !Kind.isCopyInit() || ListInit;
  
    auto tryToResolveOverload =
        [&](bool OnlyListConstructors) -> OverloadingResult {
      Candidates.clear(OverloadCandidateSet::CSK_Normal);
      HasAnyDeductionGuide = false;
  
      for (auto I = Guides.begin(), E = Guides.end(); I != E; ++I) {
        NamedDecl *D = (*I)->getUnderlyingDecl();
        if (D->isInvalidDecl())
          continue;
  
        auto *TD = dyn_cast<FunctionTemplateDecl>(D);
        auto *GD = dyn_cast_or_null<CXXDeductionGuideDecl>(
            TD ? TD->getTemplatedDecl() : dyn_cast<FunctionDecl>(D));
        if (!GD)
          continue;
  
        if (!GD->isImplicit())
          HasAnyDeductionGuide = true;
  
        // C++ [over.match.ctor]p1: (non-list copy-initialization from non-class)
        //   For copy-initialization, the candidate functions are all the
        //   converting constructors (12.3.1) of that class.
        // C++ [over.match.copy]p1: (non-list copy-initialization from class)
        //   The converting constructors of T are candidate functions.
        if (!AllowExplicit) {
          // Overload resolution checks whether the deduction guide is declared
          // explicit for us.
  
          // When looking for a converting constructor, deduction guides that
          // could never be called with one argument are not interesting to
          // check or note.
          if (GD->getMinRequiredArguments() > 1 ||
              (GD->getNumParams() == 0 && !GD->isVariadic()))
            continue;
        }
  
        // C++ [over.match.list]p1.1: (first phase list initialization)
        //   Initially, the candidate functions are the initializer-list
        //   constructors of the class T
        if (OnlyListConstructors && !isInitListConstructor(GD))
          continue;
  
        // C++ [over.match.list]p1.2: (second phase list initialization)
        //   the candidate functions are all the constructors of the class T
        // C++ [over.match.ctor]p1: (all other cases)
        //   the candidate functions are all the constructors of the class of
        //   the object being initialized
  
        // C++ [over.best.ics]p4:
        //   When [...] the constructor [...] is a candidate by
        //    - [over.match.copy] (in all cases)
        // FIXME: The "second phase of [over.match.list] case can also
        // theoretically happen here, but it's not clear whether we can
        // ever have a parameter of the right type.
        bool SuppressUserConversions = Kind.isCopyInit();
  
        if (TD)
          AddTemplateOverloadCandidate(TD, I.getPair(), /*ExplicitArgs*/ nullptr,
                                       Inits, Candidates, SuppressUserConversions,
                                       /*PartialOverloading*/ false,
                                       AllowExplicit);
        else
          AddOverloadCandidate(GD, I.getPair(), Inits, Candidates,
                               SuppressUserConversions,
                               /*PartialOverloading*/ false, AllowExplicit);
      }
      return Candidates.BestViableFunction(*this, Kind.getLocation(), Best);
    };
  
    OverloadingResult Result = OR_No_Viable_Function;
  
    // C++11 [over.match.list]p1, per DR1467: for list-initialization, first
    // try initializer-list constructors.
    if (ListInit) {
      bool TryListConstructors = true;
  
      // Try list constructors unless the list is empty and the class has one or
      // more default constructors, in which case those constructors win.
      if (!ListInit->getNumInits()) {
        for (NamedDecl *D : Guides) {
          auto *FD = dyn_cast<FunctionDecl>(D->getUnderlyingDecl());
          if (FD && FD->getMinRequiredArguments() == 0) {
            TryListConstructors = false;
            break;
          }
        }
      } else if (ListInit->getNumInits() == 1) {
        // C++ [over.match.class.deduct]:
        //   As an exception, the first phase in [over.match.list] (considering
        //   initializer-list constructors) is omitted if the initializer list
        //   consists of a single expression of type cv U, where U is a
        //   specialization of C or a class derived from a specialization of C.
        Expr *E = ListInit->getInit(0);
        auto *RD = E->getType()->getAsCXXRecordDecl();
        if (!isa<InitListExpr>(E) && RD &&
            isCompleteType(Kind.getLocation(), E->getType()) &&
            isOrIsDerivedFromSpecializationOf(RD, Template))
          TryListConstructors = false;
      }
  
      if (TryListConstructors)
        Result = tryToResolveOverload(/*OnlyListConstructor*/true);
      // Then unwrap the initializer list and try again considering all
      // constructors.
      Inits = MultiExprArg(ListInit->getInits(), ListInit->getNumInits());
    }
  
    // If list-initialization fails, or if we're doing any other kind of
    // initialization, we (eventually) consider constructors.
    if (Result == OR_No_Viable_Function)
      Result = tryToResolveOverload(/*OnlyListConstructor*/false);
  
    switch (Result) {
    case OR_Ambiguous:
      // FIXME: For list-initialization candidates, it'd usually be better to
      // list why they were not viable when given the initializer list itself as
      // an argument.
      Candidates.NoteCandidates(
          PartialDiagnosticAt(
              Kind.getLocation(),
              PDiag(diag::err_deduced_class_template_ctor_ambiguous)
                  << TemplateName),
          *this, OCD_AmbiguousCandidates, Inits);
      return QualType();
  
    case OR_No_Viable_Function: {
      CXXRecordDecl *Primary =
          cast<ClassTemplateDecl>(Template)->getTemplatedDecl();
      bool Complete =
          isCompleteType(Kind.getLocation(), Context.getTypeDeclType(Primary));
      Candidates.NoteCandidates(
          PartialDiagnosticAt(
              Kind.getLocation(),
              PDiag(Complete ? diag::err_deduced_class_template_ctor_no_viable
                             : diag::err_deduced_class_template_incomplete)
                  << TemplateName << !Guides.empty()),
          *this, OCD_AllCandidates, Inits);
      return QualType();
    }
  
    case OR_Deleted: {
      Diag(Kind.getLocation(), diag::err_deduced_class_template_deleted)
        << TemplateName;
      NoteDeletedFunction(Best->Function);
      return QualType();
    }
  
    case OR_Success:
      // C++ [over.match.list]p1:
      //   In copy-list-initialization, if an explicit constructor is chosen, the
      //   initialization is ill-formed.
      if (Kind.isCopyInit() && ListInit &&
          cast<CXXDeductionGuideDecl>(Best->Function)->isExplicit()) {
        bool IsDeductionGuide = !Best->Function->isImplicit();
        Diag(Kind.getLocation(), diag::err_deduced_class_template_explicit)
            << TemplateName << IsDeductionGuide;
        Diag(Best->Function->getLocation(),
             diag::note_explicit_ctor_deduction_guide_here)
            << IsDeductionGuide;
        return QualType();
      }
  
      // Make sure we didn't select an unusable deduction guide, and mark it
      // as referenced.
      DiagnoseUseOfDecl(Best->Function, Kind.getLocation());
      MarkFunctionReferenced(Kind.getLocation(), Best->Function);
      break;
    }
  
    // C++ [dcl.type.class.deduct]p1:
    //  The placeholder is replaced by the return type of the function selected
    //  by overload resolution for class template deduction.
    QualType DeducedType =
        SubstAutoType(TSInfo->getType(), Best->Function->getReturnType());
    Diag(TSInfo->getTypeLoc().getBeginLoc(),
         diag::warn_cxx14_compat_class_template_argument_deduction)
        << TSInfo->getTypeLoc().getSourceRange() << 1 << DeducedType;
  
    // Warn if CTAD was used on a type that does not have any user-defined
    // deduction guides.
    if (!HasAnyDeductionGuide) {
      Diag(TSInfo->getTypeLoc().getBeginLoc(),
           diag::warn_ctad_maybe_unsupported)
          << TemplateName;
      Diag(Template->getLocation(), diag::note_suppress_ctad_maybe_unsupported);
    }
  
    return DeducedType;
  }
  