SemaInit.cpp

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//===--- 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 "CheckExprLifetime.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/DeclObjC.h"
#include "clang/AST/Expr.h"
#include "clang/AST/ExprCXX.h"
#include "clang/AST/ExprObjC.h"
#include "clang/AST/ExprOpenMP.h"
#include "clang/AST/IgnoreExpr.h"
#include "clang/AST/TypeLoc.h"
#include "clang/Basic/CharInfo.h"
#include "clang/Basic/SourceManager.h"
#include "clang/Basic/Specifiers.h"
#include "clang/Basic/TargetInfo.h"
#include "clang/Sema/Designator.h"
#include "clang/Sema/EnterExpressionEvaluationContext.h"
#include "clang/Sema/Initialization.h"
#include "clang/Sema/Lookup.h"
#include "clang/Sema/Ownership.h"
#include "clang/Sema/SemaInternal.h"
#include "clang/Sema/SemaObjC.h"
#include "llvm/ADT/APInt.h"
#include "llvm/ADT/FoldingSet.h"
#include "llvm/ADT/PointerIntPair.h"
#include "llvm/ADT/STLForwardCompat.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringExtras.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();
 
  auto IsCharOrUnsignedChar = [](const QualType &T) {
    const BuiltinType *BT = dyn_cast<BuiltinType>(T.getTypePtr());
    return BT && BT->isCharType() && BT->getKind() != BuiltinType::SChar;
  };
 
  switch (SL->getKind()) {
  case StringLiteralKind::UTF8:
    // char8_t array can be initialized with a UTF-8 string.
    // - C++20 [dcl.init.string] (DR)
    //   Additionally, an array of char or unsigned char may be initialized
    //   by a UTF-8 string literal.
    if (ElemTy->isChar8Type() ||
        (Context.getLangOpts().Char8 &&
         IsCharOrUnsignedChar(ElemTy.getCanonicalType())))
      return SIF_None;
    [[fallthrough]];
  case StringLiteralKind::Ordinary:
    // 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() == StringLiteralKind::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 StringLiteralKind::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 StringLiteralKind::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 StringLiteralKind::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;
  case StringLiteralKind::Unevaluated:
    assert(false && "Unevaluated string literal in initialization");
    break;
  }
 
  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);
}
 
bool Sema::IsStringInit(Expr *Init, const ArrayType *AT) {
  return ::IsStringInit(Init, AT, Context) == SIF_None;
}
 
/// 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_PRValue);
    if (isa<StringLiteral>(E) || isa<ObjCEncodeExpr>(E))
      break;
    E = IgnoreParensSingleStep(E);
  }
}
 
/// 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_PRValue);
    if (isa<CompoundLiteralExpr>(E))
      break;
    E = IgnoreParensSingleStep(E);
  }
}
 
static bool initializingConstexprVariable(const InitializedEntity &Entity) {
  Decl *D = Entity.getDecl();
  const InitializedEntity *Parent = &Entity;
 
  while (Parent) {
    D = Parent->getDecl();
    Parent = Parent->getParent();
  }
 
  if (const auto *VD = dyn_cast_if_present<VarDecl>(D); VD && VD->isConstexpr())
    return true;
 
  return false;
}
 
static void CheckC23ConstexprInitStringLiteral(const StringLiteral *SE,
                                               Sema &SemaRef, QualType &TT);
 
static void CheckStringInit(Expr *Str, QualType &DeclT, const ArrayType *AT,
                            Sema &S, bool CheckC23ConstexprInit = false) {
  // Get the length of the string as parsed.
  auto *ConstantArrayTy =
      cast<ConstantArrayType>(Str->getType()->getAsArrayTypeUnsafe());
  uint64_t StrLength = ConstantArrayTy->getZExtSize();
 
  if (CheckC23ConstexprInit)
    if (const StringLiteral *SL = dyn_cast<StringLiteral>(Str->IgnoreParens()))
      CheckC23ConstexprInitStringLiteral(SL, S, DeclT);
 
  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, ArraySizeModifier::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->getZExtSize())
      S.Diag(Str->getBeginLoc(),
             diag::err_initializer_string_for_char_array_too_long)
          << CAT->getZExtSize() << StrLength << Str->getSourceRange();
  } else {
    // C99 6.7.8p14.
    if (StrLength - 1 > CAT->getZExtSize())
      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;
  SmallVectorImpl<QualType> *AggrDeductionCandidateParamTypes = nullptr;
  EmbedExpr *CurEmbed = nullptr; // Save current embed we're processing.
  unsigned CurEmbedIndex = 0;
 
  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,
                           bool DirectlyDesignated = false);
  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_const_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);
  static RecordDecl *getRecordDecl(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 UnionOverride = false,
                            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
            ? (UnionOverride ? diag::ext_initializer_union_overrides
                             : 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);
 
  Expr *HandleEmbed(EmbedExpr *Embed, const InitializedEntity &Entity) {
    Expr *Result = nullptr;
    // Undrestand which part of embed we'd like to reference.
    if (!CurEmbed) {
      CurEmbed = Embed;
      CurEmbedIndex = 0;
    }
    // Reference just one if we're initializing a single scalar.
    uint64_t ElsCount = 1;
    // Otherwise try to fill whole array with embed data.
    if (Entity.getKind() == InitializedEntity::EK_ArrayElement) {
      auto *AType =
          SemaRef.Context.getAsArrayType(Entity.getParent()->getType());
      assert(AType && "expected array type when initializing array");
      ElsCount = Embed->getDataElementCount();
      if (const auto *CAType = dyn_cast<ConstantArrayType>(AType))
        ElsCount = std::min(CAType->getSize().getZExtValue(),
                            ElsCount - CurEmbedIndex);
      if (ElsCount == Embed->getDataElementCount()) {
        CurEmbed = nullptr;
        CurEmbedIndex = 0;
        return Embed;
      }
    }
 
    Result = new (SemaRef.Context)
        EmbedExpr(SemaRef.Context, Embed->getLocation(), Embed->getData(),
                  CurEmbedIndex, ElsCount);
    CurEmbedIndex += ElsCount;
    if (CurEmbedIndex >= Embed->getDataElementCount()) {
      CurEmbed = nullptr;
      CurEmbedIndex = 0;
    }
    return Result;
  }
 
public:
  InitListChecker(
      Sema &S, const InitializedEntity &Entity, InitListExpr *IL, QualType &T,
      bool VerifyOnly, bool TreatUnavailableAsInvalid,
      bool InOverloadResolution = false,
      SmallVectorImpl<QualType> *AggrDeductionCandidateParamTypes = nullptr);
  InitListChecker(Sema &S, const InitializedEntity &Entity, InitListExpr *IL,
                  QualType &T,
                  SmallVectorImpl<QualType> &AggrDeductionCandidateParamTypes)
      : InitListChecker(S, Entity, IL, T, /*VerifyOnly=*/true,
                        /*TreatUnavailableAsInvalid=*/false,
                        /*InOverloadResolution=*/false,
                        &AggrDeductionCandidateParamTypes) {}
 
  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, std::nullopt, 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, std::nullopt, 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->isSyntacticForm() ? ILE : 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 {
      assert((!RDecl->isUnion() || !isa<CXXRecordDecl>(RDecl) ||
              !cast<CXXRecordDecl>(RDecl)->hasInClassInitializer()) &&
             "We should have computed initialized fields already");
      // 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->isUnion() && 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();
  uint64_t NumElements = NumInits;
  if (const ArrayType *AType = SemaRef.Context.getAsArrayType(ILE->getType())) {
    ElementType = AType->getElementType();
    if (const auto *CAType = dyn_cast<ConstantArrayType>(AType))
      NumElements = CAType->getZExtSize();
    // 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 (uint64_t 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 (isa_and_nonnull<DesignatedInitExpr>(Init))
      return true;
  return false;
}
 
InitListChecker::InitListChecker(
    Sema &S, const InitializedEntity &Entity, InitListExpr *IL, QualType &T,
    bool VerifyOnly, bool TreatUnavailableAsInvalid, bool InOverloadResolution,
    SmallVectorImpl<QualType> *AggrDeductionCandidateParamTypes)
    : SemaRef(S), VerifyOnly(VerifyOnly),
      TreatUnavailableAsInvalid(TreatUnavailableAsInvalid),
      InOverloadResolution(InOverloadResolution),
      AggrDeductionCandidateParamTypes(AggrDeductionCandidateParamTypes) {
  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 && !AggrDeductionCandidateParamTypes && FullyStructuredList) {
    bool RequiresSecondPass = false;
    FillInEmptyInitializations(Entity, FullyStructuredList, RequiresSecondPass,
                               /*OuterILE=*/nullptr, /*OuterIndex=*/0);
    if (RequiresSecondPass && !hadError)
      FillInEmptyInitializations(Entity, FullyStructuredList,
                                 RequiresSecondPass, nullptr, 0);
  }
  if (hadError && FullyStructuredList)
    FullyStructuredList->markError();
}
 
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->getZExtSize());
  }
  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();
}
 
RecordDecl *InitListChecker::getRecordDecl(QualType DeclType) {
  if (const auto *RT = DeclType->getAs<RecordType>())
    return RT->getDecl();
  if (const auto *Inject = DeclType->getAs<InjectedClassNameType>())
    return Inject->getDecl();
  return nullptr;
}
 
/// 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.
 
  if (!Entity.getParent())
    return false;
 
  // Allows elide brace initialization for aggregates with empty base.
  if (Entity.getKind() == InitializedEntity::EK_Base) {
    auto *ParentRD =
        Entity.getParent()->getType()->castAs<RecordType>()->getDecl();
    CXXRecordDecl *CXXRD = cast<CXXRecordDecl>(ParentRD);
    return CXXRD->getNumBases() == 1 && CXXRD->field_empty();
  }
 
  // Allow brace elision if the only subobject is a field.
  if (Entity.getKind() == InitializedEntity::EK_Member) {
    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();
  }
 
  return false;
}
 
/// 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_TemplateParameter:
  case InitializedEntity::EK_Result:
  case InitializedEntity::EK_ParenAggInitMember:
    // 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 (const RecordDecl *RD = getRecordDecl(DeclType)) {
    auto Bases =
        CXXRecordDecl::base_class_const_range(CXXRecordDecl::base_class_const_iterator(),
                                        CXXRecordDecl::base_class_const_iterator());
    if (DeclType->isRecordType()) {
      assert(DeclType->isAggregateType() &&
             "non-aggregate records should be handed in CheckSubElementType");
      if (auto *CXXRD = dyn_cast<CXXRecordDecl>(RD))
        Bases = CXXRD->bases();
    } else {
      Bases = cast<CXXRecordDecl>(RD)->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 (DeclType->isDependentType()) {
    // C++ [over.match.class.deduct]p1.5:
    //   brace elision is not considered for any aggregate element that has a
    //   dependent non-array type or an array type with a value-dependent bound
    ++Index;
    assert(AggrDeductionCandidateParamTypes);
    AggrDeductionCandidateParamTypes->push_back(DeclType);
  } 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,
                                          bool DirectlyDesignated) {
  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;
 
    if (TmpEntity.getType()->isDependentType()) {
      // C++ [over.match.class.deduct]p1.5:
      //   brace elision is not considered for any aggregate element that has a
      //   dependent non-array type or an array type with a value-dependent
      //   bound
      assert(AggrDeductionCandidateParamTypes);
 
      // In the presence of a braced-init-list within the initializer, we should
      // not perform brace-elision, even if brace elision would otherwise be
      // applicable. For example, given:
      //
      // template <class T> struct Foo {
      //   T t[2];
      // };
      //
      // Foo t = {{1, 2}};
      //
      // we don't want the (T, T) but rather (T [2]) in terms of the initializer
      // {{1, 2}}.
      if (isa<InitListExpr, DesignatedInitExpr>(expr) ||
          !isa_and_present<ConstantArrayType>(
              SemaRef.Context.getAsArrayType(ElemType))) {
        ++Index;
        AggrDeductionCandidateParamTypes->push_back(ElemType);
        return;
      }
    } else {
      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 (auto *Embed = dyn_cast<EmbedExpr>(expr)) {
          expr = HandleEmbed(Embed, Entity);
        }
        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());
        }
        if (!CurEmbed)
          ++Index;
        if (AggrDeductionCandidateParamTypes)
          AggrDeductionCandidateParamTypes->push_back(ElemType);
        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,
                        SemaRef.getLangOpts().C23 &&
                            initializingConstexprVariable(Entity));
      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;
 
    // In C++20, brace elision is not permitted for a designated initializer.
    if (DirectlyDesignated && SemaRef.getLangOpts().CPlusPlus && !hadError) {
      if (InOverloadResolution)
        hadError = true;
      if (!VerifyOnly) {
        SemaRef.Diag(expr->getBeginLoc(),
                     diag::ext_designated_init_brace_elision)
            << expr->getSourceRange()
            << FixItHint::CreateInsertion(expr->getBeginLoc(), "{")
            << FixItHint::CreateInsertion(
                   SemaRef.getLocForEndOfToken(expr->getEndLoc()), "}");
      }
    }
  } 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 initializers, this extension kicks in:
  // it expects 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 (SemaRef.getLangOpts().CPlusPlus) {
        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().CPlusPlus && !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;
  } else if (auto *Embed = dyn_cast<EmbedExpr>(expr)) {
    expr = HandleEmbed(Embed, Entity);
  }
 
  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 && !CurEmbed) {
      // The type was promoted, update initializer list.
      // FIXME: Why are we updating the syntactic init list?
      IList->setInit(Index, ResultExpr);
    }
  }
 
  UpdateStructuredListElement(StructuredList, StructuredIndex, ResultExpr);
  if (!CurEmbed)
    ++Index;
  if (AggrDeductionCandidateParamTypes)
    AggrDeductionCandidateParamTypes->push_back(DeclType);
}
 
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);
 
  UpdateStructuredListElement(StructuredList, StructuredIndex, expr);
  ++Index;
  if (AggrDeductionCandidateParamTypes)
    AggrDeductionCandidateParamTypes->push_back(DeclType);
}
 
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 && !SemaRef.getLangOpts().HLSL ) {
    // 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);
        }
      }
      UpdateStructuredListElement(StructuredList, StructuredIndex, ResultExpr);
      ++Index;
      if (AggrDeductionCandidateParamTypes)
        AggrDeductionCandidateParamTypes->push_back(elementType);
      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() == VectorKind::Neon ||
                        T->getVectorKind() == VectorKind::NeonPoly)) {
      // 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 and HLSL initializers allow 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 and HLSL require 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);
  if (!Destructor)
    return false;
 
  SemaRef.CheckDestructorAccess(Loc, Destructor,
                                SemaRef.PDiag(diag::err_access_dtor_temp)
                                << ElementType);
  SemaRef.MarkFunctionReferenced(Loc, Destructor);
  return SemaRef.DiagnoseUseOfDecl(Destructor, Loc);
}
 
static bool
canInitializeArrayWithEmbedDataString(ArrayRef<Expr *> ExprList,
                                      const InitializedEntity &Entity,
                                      ASTContext &Context) {
  QualType InitType = Entity.getType();
  const InitializedEntity *Parent = &Entity;
 
  while (Parent) {
    InitType = Parent->getType();
    Parent = Parent->getParent();
  }
 
  // Only one initializer, it's an embed and the types match;
  EmbedExpr *EE =
      ExprList.size() == 1
          ? dyn_cast_if_present<EmbedExpr>(ExprList[0]->IgnoreParens())
          : nullptr;
  if (!EE)
    return false;
 
  if (InitType->isArrayType()) {
    const ArrayType *InitArrayType = InitType->getAsArrayTypeUnsafe();
    QualType InitElementTy = InitArrayType->getElementType();
    QualType EmbedExprElementTy = EE->getDataStringLiteral()->getType();
    const bool TypesMatch =
        Context.typesAreCompatible(InitElementTy, EmbedExprElementTy) ||
        (InitElementTy->isCharType() && EmbedExprElementTy->isCharType());
    if (TypesMatch)
      return true;
  }
  return false;
}
 
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;
    }
  }
 
  if (canInitializeArrayWithEmbedDataString(IList->inits(), Entity,
                                            SemaRef.Context)) {
    EmbedExpr *Embed = cast<EmbedExpr>(IList->inits()[0]);
    IList->setInit(0, Embed->getDataStringLiteral());
  }
 
  // 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,
                        SemaRef.getLangOpts().C23 &&
                            initializingConstexprVariable(Entity));
      if (StructuredList) {
        UpdateStructuredListElement(StructuredList, StructuredIndex,
                                    IList->getInit(Index));
        StructuredList->resizeInits(SemaRef.Context, StructuredIndex);
      }
      ++Index;
      if (AggrDeductionCandidateParamTypes)
        AggrDeductionCandidateParamTypes->push_back(DeclType);
      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).
    bool HasErr = IList->getNumInits() != 0 || SemaRef.getLangOpts().CPlusPlus;
    if (!VerifyOnly) {
      // C23 6.7.10p4: An entity of variable length array type shall not be
      // initialized except by an empty initializer.
      //
      // The C extension warnings are issued from ParseBraceInitializer() and
      // do not need to be issued here. However, we continue to issue an error
      // in the case there are initializers or we are compiling C++. We allow
      // use of VLAs in C++, but it's not clear we want to allow {} to zero
      // init a VLA in C++ in all cases (such as with non-trivial constructors).
      // FIXME: should we allow this construct in C++ when it makes sense to do
      // so?
      if (HasErr)
        SemaRef.Diag(VAT->getSizeExpr()->getBeginLoc(),
                     diag::err_variable_object_no_init)
            << VAT->getSizeExpr()->getSourceRange();
    }
    hadError = HasErr;
    ++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);
 
    unsigned EmbedElementIndexBeforeInit = CurEmbedIndex;
    // Check this element.
    CheckSubElementType(ElementEntity, IList, elementType, Index,
                        StructuredList, StructuredIndex);
    ++elementIndex;
    if ((CurEmbed || isa<EmbedExpr>(Init)) && elementType->isScalarType()) {
      if (CurEmbed) {
        elementIndex =
            elementIndex + CurEmbedIndex - EmbedElementIndexBeforeInit - 1;
      } else {
        auto Embed = cast<EmbedExpr>(Init);
        elementIndex = elementIndex + Embed->getDataElementCount() -
                       EmbedElementIndexBeforeInit - 1;
      }
    }
 
    // 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, ArraySizeModifier::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 (!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_const_range Bases, RecordDecl::field_iterator Field,
    bool SubobjectIsDesignatorContext, unsigned &Index,
    InitListExpr *StructuredList, unsigned &StructuredIndex,
    bool TopLevelObject) {
  const RecordDecl *RD = getRecordDecl(DeclType);
 
  // If the record is invalid, some of it's members are invalid. To avoid
  // confusion, we forgo checking the initializer for the entire record.
  if (RD->isInvalidDecl()) {
    // Assume it was supposed to consume a single initializer.
    ++Index;
    hadError = true;
    return;
  }
 
  if (RD->isUnion() && IList->getNumInits() == 0) {
    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() ||
            (Field->isAnonymousStructOrUnion() &&
             Field->getType()->getAsCXXRecordDecl()->hasInClassInitializer())) {
          StructuredList->setInitializedFieldInUnion(*Field);
          // FIXME: Actually build a CXXDefaultInitExpr?
          return;
        }
      }
      llvm_unreachable("Couldn't find in-class initializer");
    }
 
    // 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 I = Bases.begin(), E = Bases.end(); I != E; ++I) {
    auto &Base = *I;
    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 (isa_and_nonnull<DesignatedInitExpr>(Init))
      Init = nullptr;
 
    // C++ [over.match.class.deduct]p1.6:
    //   each non-trailing aggregate element that is a pack expansion is assumed
    //   to correspond to no elements of the initializer list, and (1.7) a
    //   trailing aggregate element that is a pack expansion is assumed to
    //   correspond to all remaining elements of the initializer list (if any).
 
    // C++ [over.match.class.deduct]p1.9:
    //   ... except that additional parameter packs of the form P_j... are
    //   inserted into the parameter list in their original aggregate element
    //   position corresponding to each non-trailing aggregate element of
    //   type P_j that was skipped because it was a parameter pack, and the
    //   trailing sequence of parameters corresponding to a trailing
    //   aggregate element that is a pack expansion (if any) is replaced
    //   by a single parameter of the form T_n....
    if (AggrDeductionCandidateParamTypes && Base.isPackExpansion()) {
      AggrDeductionCandidateParamTypes->push_back(
          SemaRef.Context.getPackExpansionType(Base.getType(), std::nullopt));
 
      // Trailing pack expansion
      if (I + 1 == E && RD->field_empty()) {
        if (Index < IList->getNumInits())
          Index = IList->getNumInits();
        return;
      }
 
      continue;
    }
 
    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::field_iterator FieldEnd = RD->field_end();
  size_t NumRecordDecls = llvm::count_if(RD->decls(), [&](const Decl *D) {
    return isa<FieldDecl>(D) || isa<RecordDecl>(D);
  });
  bool HasDesignatedInit = false;
 
  llvm::SmallPtrSet<FieldDecl *, 4> InitializedFields;
 
  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.
      bool DesignatedInitFailed = CheckDesignatedInitializer(
          Entity, IList, DIE, 0, DeclType, &Field, nullptr, Index,
          StructuredList, StructuredIndex, true, TopLevelObject);
      if (DesignatedInitFailed)
        hadError = true;
 
      // Find the field named by the designated initializer.
      DesignatedInitExpr::Designator *D = DIE->getDesignator(0);
      if (!VerifyOnly && D->isFieldDesignator()) {
        FieldDecl *F = D->getFieldDecl();
        InitializedFields.insert(F);
        if (!DesignatedInitFailed) {
          QualType ET = SemaRef.Context.getBaseElementType(F->getType());
          if (checkDestructorReference(ET, InitLoc, SemaRef)) {
            hadError = true;
            return;
          }
        }
      }
 
      InitializedSomething = true;
      continue;
    }
 
    // Check if this is an initializer of forms:
    //
    //   struct foo f = {};
    //   struct foo g = {0};
    //
    // These are okay for randomized structures. [C99 6.7.8p19]
    //
    // Also, if there is only one element in the structure, we allow something
    // like this, because it's really not randomized in the traditional sense.
    //
    //   struct foo h = {bar};
    auto IsZeroInitializer = [&](const Expr *I) {
      if (IList->getNumInits() == 1) {
        if (NumRecordDecls == 1)
          return true;
        if (const auto *IL = dyn_cast<IntegerLiteral>(I))
          return IL->getValue().isZero();
      }
      return false;
    };
 
    // Don't allow non-designated initializers on randomized structures.
    if (RD->isRandomized() && !IsZeroInitializer(Init)) {
      if (!VerifyOnly)
        SemaRef.Diag(InitLoc, diag::err_non_designated_init_used);
      hadError = true;
      break;
    }
 
    if (Field == FieldEnd) {
      // We've run out of fields. We're done.
      break;
    }
 
    // We've already initialized a member of a union. We can stop entirely.
    if (InitializedSomething && RD->isUnion())
      return;
 
    // Stop if we've hit a flexible array member.
    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;
    InitializedFields.insert(*Field);
 
    if (RD->isUnion() && StructuredList) {
      // Initialize the first field within the union.
      StructuredList->setInitializedFieldInUnion(*Field);
    }
 
    ++Field;
  }
 
  // Emit warnings for missing struct field initializers.
  // This check is disabled for designated initializers in C.
  // This matches gcc behaviour.
  bool IsCDesignatedInitializer =
      HasDesignatedInit && !SemaRef.getLangOpts().CPlusPlus;
  if (!VerifyOnly && InitializedSomething && !RD->isUnion() &&
      !IList->isIdiomaticZeroInitializer(SemaRef.getLangOpts()) &&
      !IsCDesignatedInitializer) {
    // 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 = HasDesignatedInit ? RD->field_begin()
                                                           : Field,
                                    end = RD->field_end();
         it != end; ++it) {
      if (HasDesignatedInit && InitializedFields.count(*it))
        continue;
 
      if (!it->isUnnamedBitField() && !it->hasInClassInitializer() &&
          !it->getType()->isIncompleteArrayType()) {
        auto Diag = HasDesignatedInit
                        ? diag::warn_missing_designated_field_initializers
                        : diag::warn_missing_field_initializers;
        SemaRef.Diag(IList->getSourceRange().getEnd(), Diag) << *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 && !RD->isUnion() &&
      !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)) ||
      AggrDeductionCandidateParamTypes)
    CheckSubElementType(MemberEntity, IList, Field->getType(), Index,
                        StructuredList, StructuredIndex);
  else
    CheckImplicitInitList(MemberEntity, IList, Field->getType(), Index,
                          StructuredList, StructuredIndex);
 
  if (RD->isUnion() && StructuredList) {
    // Initialize the first field within the union.
    StructuredList->setInitializedFieldInUnion(*Field);
  }
}
 
/// 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::CreateFieldDesignator(
          (IdentifierInfo *)nullptr, DIE->getDesignator(DesigIdx)->getDotLoc(),
          DIE->getDesignator(DesigIdx)->getFieldLoc()));
    else
      Replacements.push_back(Designator::CreateFieldDesignator(
          (IdentifierInfo *)nullptr, SourceLocation(), SourceLocation()));
    assert(isa<FieldDecl>(*PI));
    Replacements.back().setFieldDecl(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(const 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:
  const 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;
      if (AggrDeductionCandidateParamTypes)
        AggrDeductionCandidateParamTypes->push_back(CurrentObjectType);
      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, /*DirectlyDesignated=*/true);
 
    // 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()),
                             /*UnionOverride=*/false,
                             /*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.
    RecordDecl *RD = getRecordDecl(CurrentObjectType);
    if (!RD) {
      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->getFieldDecl();
    if (!KnownField) {
      const IdentifierInfo *FieldName = D->getFieldName();
      ValueDecl *VD = SemaRef.tryLookupUnambiguousFieldDecl(RD, FieldName);
      if (auto *FD = dyn_cast_if_present<FieldDecl>(VD)) {
        KnownField = FD;
      } else if (auto *IFD = dyn_cast_if_present<IndirectFieldDecl>(VD)) {
        // 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());
      }
      if (!KnownField) {
        if (VerifyOnly) {
          ++Index;
          return true;  // No typo correction when just trying this out.
        }
 
        // We found a placeholder variable
        if (SemaRef.DiagRedefinedPlaceholderFieldDecl(DIE->getBeginLoc(), RD,
                                                      FieldName)) {
          ++Index;
          return true;
        }
        // Name lookup found something, but it wasn't a field.
        if (DeclContextLookupResult Lookup = RD->lookup(FieldName);
            !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(RD);
        if (TypoCorrection Corrected = SemaRef.CorrectTypo(
                DeclarationNameInfo(FieldName, D->getFieldLoc()),
                Sema::LookupMemberName, /*Scope=*/nullptr, /*SS=*/nullptr, CCC,
                Sema::CTK_ErrorRecovery, RD)) {
          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.
          SourceLocation Loc = D->getFieldLoc();
 
          // The loc can be invalid with a "null" designator (i.e. an anonymous
          // union/struct). Do our best to approximate the location.
          if (Loc.isInvalid())
            Loc = IList->getBeginLoc();
 
          SemaRef.Diag(Loc, diag::err_field_designator_unknown)
            << FieldName << CurrentObjectType << DIE->getSourceRange();
          ++Index;
          return true;
        }
      }
    }
 
    unsigned NumBases = 0;
    if (auto *CXXRD = dyn_cast<CXXRecordDecl>(RD))
      NumBases = CXXRD->getNumBases();
 
    unsigned FieldIndex = NumBases;
 
    for (auto *FI : RD->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 (RD->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()),
                /*UnionOverride=*/true,
                /*FullyOverwritten=*/SemaRef.getLangOpts().CPlusPlus ? false
                                                                     : true);
          }
 
          // 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 == RD->field_end() ||
         (*NextField)->getFieldIndex() > Field->getFieldIndex() + 1)) {
      // Find the field that we just initialized.
      FieldDecl *PrevField = nullptr;
      for (auto FI = RD->field_begin(); FI != RD->field_end(); ++FI) {
        if (FI->isUnnamedBitField())
          continue;
        if (*NextField != RD->field_end() &&
            declaresSameEntity(*FI, **NextField))
          break;
        PrevField = *FI;
      }
 
      if (PrevField &&
          PrevField->getFieldIndex() > KnownField->getFieldIndex()) {
        SemaRef.Diag(DIE->getInit()->getBeginLoc(),
                     diag::ext_designated_init_reordered)
            << KnownField << PrevField << DIE->getSourceRange();
 
        unsigned OldIndex = StructuredIndex - 1;
        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->setFieldDecl(*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 (Field != RD->field_end() && Field->isUnnamedBitField())
        ++Field;
 
      if (NextField)
        *NextField = Field;
 
      StructuredIndex = FieldIndex;
      return false;
    }
 
    if (!FinishSubobjectInit)
      return false;
 
    // We've already initialized something in the union; we're done.
    if (RD->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)
            << toString(DesignatedEndIndex, 10) << toString(MaxElements, 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)->IgnoreParenImpCasts();
 
    // Compute the character type
    QualType CharTy = AT->getElementType();
 
    // Compute the type of the integer literals.
    QualType PromotedCharTy = CharTy;
    if (Context.isPromotableIntegerType(CharTy))
      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)->getZExtSize();
      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_PRValue,
                                          FPOptionsOverride());
        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)->getZExtSize();
      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_PRValue,
                                          FPOptionsOverride());
        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(), std::nullopt, 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->getZExtSize();
      // 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);
  } else if (CurrentObjectType->isDependentType()) {
    NumElements = 1;
  }
 
  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.
    // No need to diagnose when `expr` is nullptr because a more relevant
    // diagnostic has already been issued and this diagnostic is potentially
    // noise.
    if (expr)
      diagnoseInitOverride(PrevInit, expr->getSourceRange());
  }
 
  ++StructuredIndex;
}
 
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, Sema::AllowFold);
  if (Result.isInvalid())
    return Result;
 
  if (Value.isSigned() && Value.isNegative())
    return S.Diag(Loc, diag::err_array_designator_negative)
           << toString(Value, 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);
 
    if (D.isFieldDesignator()) {
      Designators.push_back(ASTDesignator::CreateFieldDesignator(
          D.getFieldDecl(), D.getDotLoc(), D.getFieldLoc()));
    } else if (D.isArrayDesignator()) {
      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::CreateArrayDesignator(
            InitExpressions.size(), D.getLBracketLoc(), D.getRBracketLoc()));
        InitExpressions.push_back(Index);
      }
    } else if (D.isArrayRangeDesignator()) {
      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)
            << toString(StartValue, 10) << toString(EndValue, 10)
            << StartIndex->getSourceRange() << EndIndex->getSourceRange();
          Invalid = true;
        } else {
          Designators.push_back(ASTDesignator::CreateArrayRangeDesignator(
              InitExpressions.size(), D.getLBracketLoc(), D.getEllipsisLoc(),
              D.getRBracketLoc()));
          InitExpressions.push_back(StartIndex);
          InitExpressions.push_back(EndIndex);
        }
      }
    }
  }
 
  if (Invalid || Init.isInvalid())
    return ExprError();
 
  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 = {Base, IsInheritedVirtualBase};
  Result.Type = Base->getType();
  return Result;
}
 
DeclarationName InitializedEntity::getName() const {
  switch (getKind()) {
  case EK_Parameter:
  case EK_Parameter_CF_Audited: {
    ParmVarDecl *D = Parameter.getPointer();
    return (D ? D->getDeclName() : DeclarationName());
  }
 
  case EK_Variable:
  case EK_Member:
  case EK_ParenAggInitMember:
  case EK_Binding:
  case EK_TemplateParameter:
    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_ParenAggInitMember:
  case EK_Binding:
  case EK_TemplateParameter:
    return Variable.VariableOrMember;
 
  case EK_Parameter:
  case EK_Parameter_CF_Audited:
    return Parameter.getPointer();
 
  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_TemplateParameter:
  case EK_Member:
  case EK_ParenAggInitMember:
  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_TemplateParameter: OS << "TemplateParameter"; break;
  case EK_Result: OS << "Result"; break;
  case EK_StmtExprResult: OS << "StmtExprResult"; break;
  case EK_Exception: OS << "Exception"; break;
  case EK_Member:
  case EK_ParenAggInitMember:
    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() << "'\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_CastDerivedToBasePRValue:
  case SK_CastDerivedToBaseXValue:
  case SK_CastDerivedToBaseLValue:
  case SK_BindReference:
  case SK_BindReferenceToTemporary:
  case SK_FinalCopy:
  case SK_ExtraneousCopyToTemporary:
  case SK_UserConversion:
  case SK_QualificationConversionPRValue:
  case SK_QualificationConversionXValue:
  case SK_QualificationConversionLValue:
  case SK_FunctionReferenceConversion:
  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:
  case SK_ParenthesizedListInit:
    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 (const Step &S : llvm::reverse(Steps)) {
    if (S.Kind == SK_BindReference)
      return true;
    if (S.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:
  case FK_ParenthesizedListInitFailed:
  case FK_DesignatedInitForNonAggregate:
    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_PRValue:
    S.Kind = SK_CastDerivedToBasePRValue;
    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_QualificationConversionPRValue; // work around a gcc warning
  switch (VK) {
  case VK_PRValue:
    S.Kind = SK_QualificationConversionPRValue;
    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::AddFunctionReferenceConversionStep(QualType Ty) {
  Step S;
  S.Kind = SK_FunctionReferenceConversion;
  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::AddParenthesizedListInitStep(QualType T) {
  Step S;
  S.Kind = SK_ParenthesizedListInit;
  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::ArraySizeModifier::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 RequireActualConstructor,
    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 &&
      !RequireActualConstructor && !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
///                       aggregate 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;
  }
 
  bool RequireActualConstructor =
      !(Entity.getKind() != InitializedEntity::EK_Base &&
        Entity.getKind() != InitializedEntity::EK_Delegating &&
        Entity.getKind() !=
            InitializedEntity::EK_LambdaToBlockConversionBlockElement);
 
  bool CopyElisionPossible = false;
  auto ElideConstructor = [&] {
    // Convert qualifications if necessary.
    Sequence.AddQualificationConversionStep(DestType, VK_PRValue);
    if (ILE)
      Sequence.RewrapReferenceInitList(DestType, ILE);
  };
 
  // 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 && !RequireActualConstructor &&
      UnwrappedArgs.size() == 1 && UnwrappedArgs[0]->isPRValue() &&
      S.Context.hasSameUnqualifiedType(UnwrappedArgs[0]->getType(), DestType)) {
    if (ILE && !DestType->isAggregateType()) {
      // CWG2311: T{ prvalue_of_type_T } is not eligible for copy elision
      // Make this an elision if this won't call an initializer-list
      // constructor. (Always on an aggregate type or check constructors first.)
 
      // This effectively makes our resolution as follows. The parts in angle
      // brackets are additions.
      // C++17 [over.match.list]p(1.2):
      //   - If no viable initializer-list constructor is found <and the
      //     initializer list does not consist of exactly a single element with
      //     the same cv-unqualified class type as T>, [...]
      // C++17 [dcl.init.list]p(3.6):
      //   - Otherwise, if T is a class type, constructors are considered. The
      //     applicable constructors are enumerated and the best one is chosen
      //     through overload resolution. <If no constructor is found and the
      //     initializer list consists of exactly a single element with the same
      //     cv-unqualified class type as 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 a narrowing conversion [...]
      assert(!IsInitListCopy &&
             "IsInitListCopy only possible with aggregate types");
      CopyElisionPossible = true;
    } else {
      ElideConstructor();
      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, RequireActualConstructor);
 
    if (CopyElisionPossible && Result == OR_No_Viable_Function) {
      // No initializer list candidate
      ElideConstructor();
      return;
    }
  }
 
  // 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, RequireActualConstructor);
  }
  if (Result) {
    Sequence.SetOverloadFailure(
        IsListInit ? InitializationSequence::FK_ListConstructorOverloadFailed
                   : InitializationSequence::FK_ConstructorOverloadFailed,
        Result);
 
    if (Result != OR_Deleted)
      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_PRValue);
    if (IsListInit)
      Sequence.RewrapReferenceInitList(Entity.getType(), ILE);
    return;
  }
 
  CXXConstructorDecl *CtorDecl = cast<CXXConstructorDecl>(Best->Function);
  if (Result != OR_Deleted) {
    // 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.
    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;
    }
  }
 
  // [class.copy.elision]p3:
  // In some copy-initialization contexts, a two-stage overload resolution
  // is performed.
  // If the first overload resolution selects a deleted function, we also
  // need the initialization sequence to decide whether to perform the second
  // overload resolution.
  // For deleted functions in other contexts, there is no need to get the
  // initialization sequence.
  if (Result == OR_Deleted && Kind.getKind() != InitializationKind::IK_Copy)
    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,
                                           bool TopLevelOfInitList);
 
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 = S.getCompletedType(Initializer);
    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,
                                     /*TopLevelOfInitList=*/true);
      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);
  }
  // Perform address space compatibility check.
  QualType cv1T1IgnoreAS = cv1T1;
  if (T1Quals.hasAddressSpace()) {
    Qualifiers T2Quals;
    (void)S.Context.getUnqualifiedArrayType(InitList->getType(), T2Quals);
    if (!T1Quals.isAddressSpaceSupersetOf(T2Quals)) {
      Sequence.SetFailed(
          InitializationSequence::FK_ReferenceInitDropsQualifiers);
      return;
    }
    // Ignore address space of reference type at this point and perform address
    // space conversion after the reference binding step.
    cv1T1IgnoreAS =
        S.Context.getQualifiedType(T1, T1Quals.withoutAddressSpace());
  }
  // Not reference-related. Create a temporary and bind to that.
  InitializedEntity TempEntity =
      InitializedEntity::InitializeTemporary(cv1T1IgnoreAS);
 
  TryListInitialization(S, TempEntity, Kind, InitList, Sequence,
                        TreatUnavailableAsInvalid);
  if (Sequence) {
    if (DestType->isRValueReferenceType() ||
        (T1Quals.hasConst() && !T1Quals.hasVolatile())) {
      if (S.getLangOpts().CPlusPlus20 &&
          isa<IncompleteArrayType>(T1->getUnqualifiedDesugaredType()) &&
          DestType->isRValueReferenceType()) {
        // C++20 [dcl.init.list]p3.10:
        // List-initialization of an object or reference of type T is defined as
        // follows:
        // ..., unless T is “reference to array of unknown bound of U”, in which
        // case the type of the prvalue is the type of x in the declaration U
        // x[] H, where H is the initializer list.
        Sequence.AddQualificationConversionStep(cv1T1, clang::VK_PRValue);
      }
      Sequence.AddReferenceBindingStep(cv1T1IgnoreAS,
                                       /*BindingTemporary=*/true);
      if (T1Quals.hasAddressSpace())
        Sequence.AddQualificationConversionStep(
            cv1T1, DestType->isRValueReferenceType() ? VK_XValue : VK_LValue);
    } 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++20 [dcl.init.list]p3:
  // - If the braced-init-list contains a designated-initializer-list, T shall
  //   be an aggregate class. [...] Aggregate initialization is performed.
  //
  // We allow arrays here too in order to support array designators.
  //
  // FIXME: This check should precede the handling of reference initialization.
  // We follow other compilers in allowing things like 'Aggr &&a = {.x = 1};'
  // as a tentative DR resolution.
  bool IsDesignatedInit = InitList->hasDesignatedInit();
  if (!DestType->isAggregateType() && IsDesignatedInit) {
    Sequence.SetFailed(
        InitializationSequence::FK_DesignatedInitForNonAggregate);
    return;
  }
 
  // C++11 [dcl.init.list]p3, per DR1467 and DR2137:
  // - If T is an aggregate class 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 &&
      !IsDesignatedInit) {
    if (DestType->isRecordType() && DestType->isAggregateType()) {
      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) && !IsDesignatedInit)) {
    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()->isIntegralOrUnscopedEnumerationType() ||
         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, unscoped 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->isPRValue())
        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,