lib/Sema/SemaInit.cpp

   1 //===--- SemaInit.cpp - Semantic Analysis for Initializers ----------------===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // License. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9 //
  10 // This file implements semantic analysis for initializers.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "clang/AST/ASTContext.h"
  15 #include "clang/AST/DeclObjC.h"
  16 #include "clang/AST/ExprCXX.h"
  17 #include "clang/AST/ExprObjC.h"
  18 #include "clang/AST/ExprOpenMP.h"
  19 #include "clang/AST/TypeLoc.h"
  20 #include "clang/Basic/TargetInfo.h"
  21 #include "clang/Sema/Designator.h"
  22 #include "clang/Sema/Initialization.h"
  23 #include "clang/Sema/Lookup.h"
  24 #include "clang/Sema/SemaInternal.h"
  25 #include "llvm/ADT/APInt.h"
  26 #include "llvm/ADT/SmallString.h"
  27 #include "llvm/Support/ErrorHandling.h"
  28 #include "llvm/Support/raw_ostream.h"
  29
  30 using namespace clang;
  31
  32 //===----------------------------------------------------------------------===//
  33 // Sema Initialization Checking
  34 //===----------------------------------------------------------------------===//
  35
  36 /// Check whether T is compatible with a wide character type (wchar_t,
  37 /// char16_t or char32_t).
  38 static bool IsWideCharCompatible(QualType T, ASTContext &Context) {
  39   if (Context.typesAreCompatible(Context.getWideCharType(), T))
  40     return true;
  41   if (Context.getLangOpts().CPlusPlus || Context.getLangOpts().C11) {
  42     return Context.typesAreCompatible(Context.Char16Ty, T) ||
  43            Context.typesAreCompatible(Context.Char32Ty, T);
  44   }
  45   return false;
  46 }
  47
  48 enum StringInitFailureKind {
  49   SIF_None,
  50   SIF_NarrowStringIntoWideChar,
  51   SIF_WideStringIntoChar,
  52   SIF_IncompatWideStringIntoWideChar,
  53   SIF_UTF8StringIntoPlainChar,
  54   SIF_PlainStringIntoUTF8Char,
  55   SIF_Other
  56 };
  57
  58 /// Check whether the array of type AT can be initialized by the Init
  59 /// expression by means of string initialization. Returns SIF_None if so,
  60 /// otherwise returns a StringInitFailureKind that describes why the
  61 /// initialization would not work.
  62 static StringInitFailureKind IsStringInit(Expr *Init, const ArrayType *AT,
  63                                           ASTContext &Context) {
  64   if (!isa<ConstantArrayType>(AT) && !isa<IncompleteArrayType>(AT))
  65     return SIF_Other;
  66
  67   // See if this is a string literal or @encode.
  68   Init = Init->IgnoreParens();
  69
  70   // Handle @encode, which is a narrow string.
  71   if (isa<ObjCEncodeExpr>(Init) && AT->getElementType()->isCharType())
  72     return SIF_None;
  73
  74   // Otherwise we can only handle string literals.
  75   StringLiteral *SL = dyn_cast<StringLiteral>(Init);
  76   if (!SL)
  77     return SIF_Other;
  78
  79   const QualType ElemTy =
  80       Context.getCanonicalType(AT->getElementType()).getUnqualifiedType();
  81
  82   switch (SL->getKind()) {
  83   case StringLiteral::UTF8:
  84     // char8_t array can be initialized with a UTF-8 string.
  85     if (ElemTy->isChar8Type())
  86       return SIF_None;
  87     LLVM_FALLTHROUGH;
  88   case StringLiteral::Ascii:
  89     // char array can be initialized with a narrow string.
  90     // Only allow char x[] = "foo";  not char x[] = L"foo";
  91     if (ElemTy->isCharType())
  92       return (SL->getKind() == StringLiteral::UTF8 &&
  93               Context.getLangOpts().Char8)
  94                  ? SIF_UTF8StringIntoPlainChar
  95                  : SIF_None;
  96     if (ElemTy->isChar8Type())
  97       return SIF_PlainStringIntoUTF8Char;
  98     if (IsWideCharCompatible(ElemTy, Context))
  99       return SIF_NarrowStringIntoWideChar;
 100     return SIF_Other;
 101   // C99 6.7.8p15 (with correction from DR343), or C11 6.7.9p15:
 102   // "An array with element type compatible with a qualified or unqualified
 103   // version of wchar_t, char16_t, or char32_t may be initialized by a wide
 104   // string literal with the corresponding encoding prefix (L, u, or U,
 105   // respectively), optionally enclosed in braces.
 106   case StringLiteral::UTF16:
 107     if (Context.typesAreCompatible(Context.Char16Ty, ElemTy))
 108       return SIF_None;
 109     if (ElemTy->isCharType() || ElemTy->isChar8Type())
 110       return SIF_WideStringIntoChar;
 111     if (IsWideCharCompatible(ElemTy, Context))
 112       return SIF_IncompatWideStringIntoWideChar;
 113     return SIF_Other;
 114   case StringLiteral::UTF32:
 115     if (Context.typesAreCompatible(Context.Char32Ty, ElemTy))
 116       return SIF_None;
 117     if (ElemTy->isCharType() || ElemTy->isChar8Type())
 118       return SIF_WideStringIntoChar;
 119     if (IsWideCharCompatible(ElemTy, Context))
 120       return SIF_IncompatWideStringIntoWideChar;
 121     return SIF_Other;
 122   case StringLiteral::Wide:
 123     if (Context.typesAreCompatible(Context.getWideCharType(), ElemTy))
 124       return SIF_None;
 125     if (ElemTy->isCharType() || ElemTy->isChar8Type())
 126       return SIF_WideStringIntoChar;
 127     if (IsWideCharCompatible(ElemTy, Context))
 128       return SIF_IncompatWideStringIntoWideChar;
 129     return SIF_Other;
 130   }
 131
 132   llvm_unreachable("missed a StringLiteral kind?");
 133 }
 134
 135 static StringInitFailureKind IsStringInit(Expr *init, QualType declType,
 136                                           ASTContext &Context) {
 137   const ArrayType *arrayType = Context.getAsArrayType(declType);
 138   if (!arrayType)
 139     return SIF_Other;
 140   return IsStringInit(init, arrayType, Context);
 141 }
 142
 143 /// Update the type of a string literal, including any surrounding parentheses,
 144 /// to match the type of the object which it is initializing.
 145 static void updateStringLiteralType(Expr *E, QualType Ty) {
 146   while (true) {
 147     E->setType(Ty);
 148     if (isa<StringLiteral>(E) || isa<ObjCEncodeExpr>(E))
 149       break;
 150     else if (ParenExpr *PE = dyn_cast<ParenExpr>(E))
 151       E = PE->getSubExpr();
 152     else if (UnaryOperator *UO = dyn_cast<UnaryOperator>(E))
 153       E = UO->getSubExpr();
 154     else if (GenericSelectionExpr *GSE = dyn_cast<GenericSelectionExpr>(E))
 155       E = GSE->getResultExpr();
 156     else
 157       llvm_unreachable("unexpected expr in string literal init");
 158   }
 159 }
 160
 161 static void CheckStringInit(Expr *Str, QualType &DeclT, const ArrayType *AT,
 162                             Sema &S) {
 163   // Get the length of the string as parsed.
 164   auto *ConstantArrayTy =
 165       cast<ConstantArrayType>(Str->getType()->getAsArrayTypeUnsafe());
 166   uint64_t StrLength = ConstantArrayTy->getSize().getZExtValue();
 167
 168   if (const IncompleteArrayType *IAT = dyn_cast<IncompleteArrayType>(AT)) {
 169     // C99 6.7.8p14. We have an array of character type with unknown size
 170     // being initialized to a string literal.
 171     llvm::APInt ConstVal(32, StrLength);
 172     // Return a new array type (C99 6.7.8p22).
 173     DeclT = S.Context.getConstantArrayType(IAT->getElementType(),
 174                                            ConstVal,
 175                                            ArrayType::Normal, 0);
 176     updateStringLiteralType(Str, DeclT);
 177     return;
 178   }
 179
 180   const ConstantArrayType *CAT = cast<ConstantArrayType>(AT);
 181
 182   // We have an array of character type with known size.  However,
 183   // the size may be smaller or larger than the string we are initializing.
 184   // FIXME: Avoid truncation for 64-bit length strings.
 185   if (S.getLangOpts().CPlusPlus) {
 186     if (StringLiteral *SL = dyn_cast<StringLiteral>(Str->IgnoreParens())) {
 187       // For Pascal strings it's OK to strip off the terminating null character,
 188       // so the example below is valid:
 189       //
 190       // unsigned char a[2] = "\pa";
 191       if (SL->isPascal())
 192         StrLength--;
 193     }
 194
 195     // [dcl.init.string]p2
 196     if (StrLength > CAT->getSize().getZExtValue())
 197       S.Diag(Str->getLocStart(),
 198              diag::err_initializer_string_for_char_array_too_long)
 199         << Str->getSourceRange();
 200   } else {
 201     // C99 6.7.8p14.
 202     if (StrLength-1 > CAT->getSize().getZExtValue())
 203       S.Diag(Str->getLocStart(),
 204              diag::ext_initializer_string_for_char_array_too_long)
 205         << Str->getSourceRange();
 206   }
 207
 208   // Set the type to the actual size that we are initializing.  If we have
 209   // something like:
 210   //   char x[1] = "foo";
 211   // then this will set the string literal's type to char[1].
 212   updateStringLiteralType(Str, DeclT);
 213 }
 214
 215 //===----------------------------------------------------------------------===//
 216 // Semantic checking for initializer lists.
 217 //===----------------------------------------------------------------------===//
 218
 219 namespace {
 220
 221 /// Semantic checking for initializer lists.
 222 ///
 223 /// The InitListChecker class contains a set of routines that each
 224 /// handle the initialization of a certain kind of entity, e.g.,
 225 /// arrays, vectors, struct/union types, scalars, etc. The
 226 /// InitListChecker itself performs a recursive walk of the subobject
 227 /// structure of the type to be initialized, while stepping through
 228 /// the initializer list one element at a time. The IList and Index
 229 /// parameters to each of the Check* routines contain the active
 230 /// (syntactic) initializer list and the index into that initializer
 231 /// list that represents the current initializer. Each routine is
 232 /// responsible for moving that Index forward as it consumes elements.
 233 ///
 234 /// Each Check* routine also has a StructuredList/StructuredIndex
 235 /// arguments, which contains the current "structured" (semantic)
 236 /// initializer list and the index into that initializer list where we
 237 /// are copying initializers as we map them over to the semantic
 238 /// list. Once we have completed our recursive walk of the subobject
 239 /// structure, we will have constructed a full semantic initializer
 240 /// list.
 241 ///
 242 /// C99 designators cause changes in the initializer list traversal,
 243 /// because they make the initialization "jump" into a specific
 244 /// subobject and then continue the initialization from that
 245 /// point. CheckDesignatedInitializer() recursively steps into the
 246 /// designated subobject and manages backing out the recursion to
 247 /// initialize the subobjects after the one designated.
 248 class InitListChecker {
 249   Sema &SemaRef;
 250   bool hadError;
 251   bool VerifyOnly; // no diagnostics, no structure building
 252   bool TreatUnavailableAsInvalid; // Used only in VerifyOnly mode.
 253   llvm::DenseMap<InitListExpr *, InitListExpr *> SyntacticToSemantic;
 254   InitListExpr *FullyStructuredList;
 255
 256   void CheckImplicitInitList(const InitializedEntity &Entity,
 257                              InitListExpr *ParentIList, QualType T,
 258                              unsigned &Index, InitListExpr *StructuredList,
 259                              unsigned &StructuredIndex);
 260   void CheckExplicitInitList(const InitializedEntity &Entity,
 261                              InitListExpr *IList, QualType &T,
 262                              InitListExpr *StructuredList,
 263                              bool TopLevelObject = false);
 264   void CheckListElementTypes(const InitializedEntity &Entity,
 265                              InitListExpr *IList, QualType &DeclType,
 266                              bool SubobjectIsDesignatorContext,
 267                              unsigned &Index,
 268                              InitListExpr *StructuredList,
 269                              unsigned &StructuredIndex,
 270                              bool TopLevelObject = false);
 271   void CheckSubElementType(const InitializedEntity &Entity,
 272                            InitListExpr *IList, QualType ElemType,
 273                            unsigned &Index,
 274                            InitListExpr *StructuredList,
 275                            unsigned &StructuredIndex);
 276   void CheckComplexType(const InitializedEntity &Entity,
 277                         InitListExpr *IList, QualType DeclType,
 278                         unsigned &Index,
 279                         InitListExpr *StructuredList,
 280                         unsigned &StructuredIndex);
 281   void CheckScalarType(const InitializedEntity &Entity,
 282                        InitListExpr *IList, QualType DeclType,
 283                        unsigned &Index,
 284                        InitListExpr *StructuredList,
 285                        unsigned &StructuredIndex);
 286   void CheckReferenceType(const InitializedEntity &Entity,
 287                           InitListExpr *IList, QualType DeclType,
 288                           unsigned &Index,
 289                           InitListExpr *StructuredList,
 290                           unsigned &StructuredIndex);
 291   void CheckVectorType(const InitializedEntity &Entity,
 292                        InitListExpr *IList, QualType DeclType, unsigned &Index,
 293                        InitListExpr *StructuredList,
 294                        unsigned &StructuredIndex);
 295   void CheckStructUnionTypes(const InitializedEntity &Entity,
 296                              InitListExpr *IList, QualType DeclType,
 297                              CXXRecordDecl::base_class_range Bases,
 298                              RecordDecl::field_iterator Field,
 299                              bool SubobjectIsDesignatorContext, unsigned &Index,
 300                              InitListExpr *StructuredList,
 301                              unsigned &StructuredIndex,
 302                              bool TopLevelObject = false);
 303   void CheckArrayType(const InitializedEntity &Entity,
 304                       InitListExpr *IList, QualType &DeclType,
 305                       llvm::APSInt elementIndex,
 306                       bool SubobjectIsDesignatorContext, unsigned &Index,
 307                       InitListExpr *StructuredList,
 308                       unsigned &StructuredIndex);
 309   bool CheckDesignatedInitializer(const InitializedEntity &Entity,
 310                                   InitListExpr *IList, DesignatedInitExpr *DIE,
 311                                   unsigned DesigIdx,
 312                                   QualType &CurrentObjectType,
 313                                   RecordDecl::field_iterator *NextField,
 314                                   llvm::APSInt *NextElementIndex,
 315                                   unsigned &Index,
 316                                   InitListExpr *StructuredList,
 317                                   unsigned &StructuredIndex,
 318                                   bool FinishSubobjectInit,
 319                                   bool TopLevelObject);
 320   InitListExpr *getStructuredSubobjectInit(InitListExpr *IList, unsigned Index,
 321                                            QualType CurrentObjectType,
 322                                            InitListExpr *StructuredList,
 323                                            unsigned StructuredIndex,
 324                                            SourceRange InitRange,
 325                                            bool IsFullyOverwritten = false);
 326   void UpdateStructuredListElement(InitListExpr *StructuredList,
 327                                    unsigned &StructuredIndex,
 328                                    Expr *expr);
 329   int numArrayElements(QualType DeclType);
 330   int numStructUnionElements(QualType DeclType);
 331
 332   static ExprResult PerformEmptyInit(Sema &SemaRef,
 333                                      SourceLocation Loc,
 334                                      const InitializedEntity &Entity,
 335                                      bool VerifyOnly,
 336                                      bool TreatUnavailableAsInvalid);
 337
 338   // Explanation on the "FillWithNoInit" mode:
 339   //
 340   // Assume we have the following definitions (Case#1):
 341   // struct P { char x[6][6]; } xp = { .x[1] = "bar" };
 342   // struct PP { struct P lp; } l = { .lp = xp, .lp.x[1][2] = 'f' };
 343   //
 344   // l.lp.x[1][0..1] should not be filled with implicit initializers because the
 345   // "base" initializer "xp" will provide values for them; l.lp.x[1] will be "baf".
 346   //
 347   // But if we have (Case#2):
 348   // struct PP l = { .lp = xp, .lp.x[1] = { [2] = 'f' } };
 349   //
 350   // l.lp.x[1][0..1] are implicitly initialized and do not use values from the
 351   // "base" initializer; l.lp.x[1] will be "\0\0f\0\0\0".
 352   //
 353   // To distinguish Case#1 from Case#2, and also to avoid leaving many "holes"
 354   // in the InitListExpr, the "holes" in Case#1 are filled not with empty
 355   // initializers but with special "NoInitExpr" place holders, which tells the
 356   // CodeGen not to generate any initializers for these parts.
 357   void FillInEmptyInitForBase(unsigned Init, const CXXBaseSpecifier &Base,
 358                               const InitializedEntity &ParentEntity,
 359                               InitListExpr *ILE, bool &RequiresSecondPass,
 360                               bool FillWithNoInit);
 361   void FillInEmptyInitForField(unsigned Init, FieldDecl *Field,
 362                                const InitializedEntity &ParentEntity,
 363                                InitListExpr *ILE, bool &RequiresSecondPass,
 364                                bool FillWithNoInit = false);
 365   void FillInEmptyInitializations(const InitializedEntity &Entity,
 366                                   InitListExpr *ILE, bool &RequiresSecondPass,
 367                                   InitListExpr *OuterILE, unsigned OuterIndex,
 368                                   bool FillWithNoInit = false);
 369   bool CheckFlexibleArrayInit(const InitializedEntity &Entity,
 370                               Expr *InitExpr, FieldDecl *Field,
 371                               bool TopLevelObject);
 372   void CheckEmptyInitializable(const InitializedEntity &Entity,
 373                                SourceLocation Loc);
 374
 375 public:
 376   InitListChecker(Sema &S, const InitializedEntity &Entity,
 377                   InitListExpr *IL, QualType &T, bool VerifyOnly,
 378                   bool TreatUnavailableAsInvalid);
 379   bool HadError() { return hadError; }
 380
 381   // Retrieves the fully-structured initializer list used for
 382   // semantic analysis and code generation.
 383   InitListExpr *getFullyStructuredList() const { return FullyStructuredList; }
 384 };
 385
 386 } // end anonymous namespace
 387
 388 ExprResult InitListChecker::PerformEmptyInit(Sema &SemaRef,
 389                                              SourceLocation Loc,
 390                                              const InitializedEntity &Entity,
 391                                              bool VerifyOnly,
 392                                              bool TreatUnavailableAsInvalid) {
 393   InitializationKind Kind = InitializationKind::CreateValue(Loc, Loc, Loc,
 394                                                             true);
 395   MultiExprArg SubInit;
 396   Expr *InitExpr;
 397   InitListExpr DummyInitList(SemaRef.Context, Loc, None, Loc);
 398
 399   // C++ [dcl.init.aggr]p7:
 400   //   If there are fewer initializer-clauses in the list than there are
 401   //   members in the aggregate, then each member not explicitly initialized
 402   //   ...
 403   bool EmptyInitList = SemaRef.getLangOpts().CPlusPlus11 &&
 404       Entity.getType()->getBaseElementTypeUnsafe()->isRecordType();
 405   if (EmptyInitList) {
 406     // C++1y / DR1070:
 407     //   shall be initialized [...] from an empty initializer list.
 408     //
 409     // We apply the resolution of this DR to C++11 but not C++98, since C++98
 410     // does not have useful semantics for initialization from an init list.
 411     // We treat this as copy-initialization, because aggregate initialization
 412     // always performs copy-initialization on its elements.
 413     //
 414     // Only do this if we're initializing a class type, to avoid filling in
 415     // the initializer list where possible.
 416     InitExpr = VerifyOnly ? &DummyInitList : new (SemaRef.Context)
 417                    InitListExpr(SemaRef.Context, Loc, None, Loc);
 418     InitExpr->setType(SemaRef.Context.VoidTy);
 419     SubInit = InitExpr;
 420     Kind = InitializationKind::CreateCopy(Loc, Loc);
 421   } else {
 422     // C++03:
 423     //   shall be value-initialized.
 424   }
 425
 426   InitializationSequence InitSeq(SemaRef, Entity, Kind, SubInit);
 427   // libstdc++4.6 marks the vector default constructor as explicit in
 428   // _GLIBCXX_DEBUG mode, so recover using the C++03 logic in that case.
 429   // stlport does so too. Look for std::__debug for libstdc++, and for
 430   // std:: for stlport.  This is effectively a compiler-side implementation of
 431   // LWG2193.
 432   if (!InitSeq && EmptyInitList && InitSeq.getFailureKind() ==
 433           InitializationSequence::FK_ExplicitConstructor) {
 434     OverloadCandidateSet::iterator Best;
 435     OverloadingResult O =
 436         InitSeq.getFailedCandidateSet()
 437             .BestViableFunction(SemaRef, Kind.getLocation(), Best);
 438     (void)O;
 439     assert(O == OR_Success && "Inconsistent overload resolution");
 440     CXXConstructorDecl *CtorDecl = cast<CXXConstructorDecl>(Best->Function);
 441     CXXRecordDecl *R = CtorDecl->getParent();
 442
 443     if (CtorDecl->getMinRequiredArguments() == 0 &&
 444         CtorDecl->isExplicit() && R->getDeclName() &&
 445         SemaRef.SourceMgr.isInSystemHeader(CtorDecl->getLocation())) {
 446       bool IsInStd = false;
 447       for (NamespaceDecl *ND = dyn_cast<NamespaceDecl>(R->getDeclContext());
 448            ND && !IsInStd; ND = dyn_cast<NamespaceDecl>(ND->getParent())) {
 449         if (SemaRef.getStdNamespace()->InEnclosingNamespaceSetOf(ND))
 450           IsInStd = true;
 451       }
 452
 453       if (IsInStd && llvm::StringSwitch<bool>(R->getName())
 454               .Cases("basic_string", "deque", "forward_list", true)
 455               .Cases("list", "map", "multimap", "multiset", true)
 456               .Cases("priority_queue", "queue", "set", "stack", true)
 457               .Cases("unordered_map", "unordered_set", "vector", true)
 458               .Default(false)) {
 459         InitSeq.InitializeFrom(
 460             SemaRef, Entity,
 461             InitializationKind::CreateValue(Loc, Loc, Loc, true),
 462             MultiExprArg(), /*TopLevelOfInitList=*/false,
 463             TreatUnavailableAsInvalid);
 464         // Emit a warning for this.  System header warnings aren't shown
 465         // by default, but people working on system headers should see it.
 466         if (!VerifyOnly) {
 467           SemaRef.Diag(CtorDecl->getLocation(),
 468                        diag::warn_invalid_initializer_from_system_header);
 469           if (Entity.getKind() == InitializedEntity::EK_Member)
 470             SemaRef.Diag(Entity.getDecl()->getLocation(),
 471                          diag::note_used_in_initialization_here);
 472           else if (Entity.getKind() == InitializedEntity::EK_ArrayElement)
 473             SemaRef.Diag(Loc, diag::note_used_in_initialization_here);
 474         }
 475       }
 476     }
 477   }
 478   if (!InitSeq) {
 479     if (!VerifyOnly) {
 480       InitSeq.Diagnose(SemaRef, Entity, Kind, SubInit);
 481       if (Entity.getKind() == InitializedEntity::EK_Member)
 482         SemaRef.Diag(Entity.getDecl()->getLocation(),
 483                      diag::note_in_omitted_aggregate_initializer)
 484           << /*field*/1 << Entity.getDecl();
 485       else if (Entity.getKind() == InitializedEntity::EK_ArrayElement) {
 486         bool IsTrailingArrayNewMember =
 487             Entity.getParent() &&
 488             Entity.getParent()->isVariableLengthArrayNew();
 489         SemaRef.Diag(Loc, diag::note_in_omitted_aggregate_initializer)
 490           << (IsTrailingArrayNewMember ? 2 : /*array element*/0)
 491           << Entity.getElementIndex();
 492       }
 493     }
 494     return ExprError();
 495   }
 496
 497   return VerifyOnly ? ExprResult(static_cast<Expr *>(nullptr))
 498                     : InitSeq.Perform(SemaRef, Entity, Kind, SubInit);
 499 }
 500
 501 void InitListChecker::CheckEmptyInitializable(const InitializedEntity &Entity,
 502                                               SourceLocation Loc) {
 503   assert(VerifyOnly &&
 504          "CheckEmptyInitializable is only inteded for verification mode.");
 505   if (PerformEmptyInit(SemaRef, Loc, Entity, /*VerifyOnly*/true,
 506                        TreatUnavailableAsInvalid).isInvalid())
 507     hadError = true;
 508 }
 509
 510 void InitListChecker::FillInEmptyInitForBase(
 511     unsigned Init, const CXXBaseSpecifier &Base,
 512     const InitializedEntity &ParentEntity, InitListExpr *ILE,
 513     bool &RequiresSecondPass, bool FillWithNoInit) {
 514   assert(Init < ILE->getNumInits() && "should have been expanded");
 515
 516   InitializedEntity BaseEntity = InitializedEntity::InitializeBase(
 517       SemaRef.Context, &Base, false, &ParentEntity);
 518
 519   if (!ILE->getInit(Init)) {
 520     ExprResult BaseInit =
 521         FillWithNoInit ? new (SemaRef.Context) NoInitExpr(Base.getType())
 522                        : PerformEmptyInit(SemaRef, ILE->getLocEnd(), BaseEntity,
 523                                           /*VerifyOnly*/ false,
 524                                           TreatUnavailableAsInvalid);
 525     if (BaseInit.isInvalid()) {
 526       hadError = true;
 527       return;
 528     }
 529
 530     ILE->setInit(Init, BaseInit.getAs<Expr>());
 531   } else if (InitListExpr *InnerILE =
 532                  dyn_cast<InitListExpr>(ILE->getInit(Init))) {
 533     FillInEmptyInitializations(BaseEntity, InnerILE, RequiresSecondPass,
 534                                ILE, Init, FillWithNoInit);
 535   } else if (DesignatedInitUpdateExpr *InnerDIUE =
 536                dyn_cast<DesignatedInitUpdateExpr>(ILE->getInit(Init))) {
 537     FillInEmptyInitializations(BaseEntity, InnerDIUE->getUpdater(),
 538                                RequiresSecondPass, ILE, Init,
 539                                /*FillWithNoInit =*/true);
 540   }
 541 }
 542
 543 void InitListChecker::FillInEmptyInitForField(unsigned Init, FieldDecl *Field,
 544                                         const InitializedEntity &ParentEntity,
 545                                               InitListExpr *ILE,
 546                                               bool &RequiresSecondPass,
 547                                               bool FillWithNoInit) {
 548   SourceLocation Loc = ILE->getLocEnd();
 549   unsigned NumInits = ILE->getNumInits();
 550   InitializedEntity MemberEntity
 551     = InitializedEntity::InitializeMember(Field, &ParentEntity);
 552
 553   if (const RecordType *RType = ILE->getType()->getAs<RecordType>())
 554     if (!RType->getDecl()->isUnion())
 555       assert(Init < NumInits && "This ILE should have been expanded");
 556
 557   if (Init >= NumInits || !ILE->getInit(Init)) {
 558     if (FillWithNoInit) {
 559       Expr *Filler = new (SemaRef.Context) NoInitExpr(Field->getType());
 560       if (Init < NumInits)
 561         ILE->setInit(Init, Filler);
 562       else
 563         ILE->updateInit(SemaRef.Context, Init, Filler);
 564       return;
 565     }
 566     // C++1y [dcl.init.aggr]p7:
 567     //   If there are fewer initializer-clauses in the list than there are
 568     //   members in the aggregate, then each member not explicitly initialized
 569     //   shall be initialized from its brace-or-equal-initializer [...]
 570     if (Field->hasInClassInitializer()) {
 571       ExprResult DIE = SemaRef.BuildCXXDefaultInitExpr(Loc, Field);
 572       if (DIE.isInvalid()) {
 573         hadError = true;
 574         return;
 575       }
 576       SemaRef.checkInitializerLifetime(MemberEntity, DIE.get());
 577       if (Init < NumInits)
 578         ILE->setInit(Init, DIE.get());
 579       else {
 580         ILE->updateInit(SemaRef.Context, Init, DIE.get());
 581         RequiresSecondPass = true;
 582       }
 583       return;
 584     }
 585
 586     if (Field->getType()->isReferenceType()) {
 587       // C++ [dcl.init.aggr]p9:
 588       //   If an incomplete or empty initializer-list leaves a
 589       //   member of reference type uninitialized, the program is
 590       //   ill-formed.
 591       SemaRef.Diag(Loc, diag::err_init_reference_member_uninitialized)
 592         << Field->getType()
 593         << ILE->getSyntacticForm()->getSourceRange();
 594       SemaRef.Diag(Field->getLocation(),
 595                    diag::note_uninit_reference_member);
 596       hadError = true;
 597       return;
 598     }
 599
 600     ExprResult MemberInit = PerformEmptyInit(SemaRef, Loc, MemberEntity,
 601                                              /*VerifyOnly*/false,
 602                                              TreatUnavailableAsInvalid);
 603     if (MemberInit.isInvalid()) {
 604       hadError = true;
 605       return;
 606     }
 607
 608     if (hadError) {
 609       // Do nothing
 610     } else if (Init < NumInits) {
 611       ILE->setInit(Init, MemberInit.getAs<Expr>());
 612     } else if (!isa<ImplicitValueInitExpr>(MemberInit.get())) {
 613       // Empty initialization requires a constructor call, so
 614       // extend the initializer list to include the constructor
 615       // call and make a note that we'll need to take another pass
 616       // through the initializer list.
 617       ILE->updateInit(SemaRef.Context, Init, MemberInit.getAs<Expr>());
 618       RequiresSecondPass = true;
 619     }
 620   } else if (InitListExpr *InnerILE
 621                = dyn_cast<InitListExpr>(ILE->getInit(Init)))
 622     FillInEmptyInitializations(MemberEntity, InnerILE,
 623                                RequiresSecondPass, ILE, Init, FillWithNoInit);
 624   else if (DesignatedInitUpdateExpr *InnerDIUE
 625                = dyn_cast<DesignatedInitUpdateExpr>(ILE->getInit(Init)))
 626     FillInEmptyInitializations(MemberEntity, InnerDIUE->getUpdater(),
 627                                RequiresSecondPass, ILE, Init,
 628                                /*FillWithNoInit =*/true);
 629 }
 630
 631 /// Recursively replaces NULL values within the given initializer list
 632 /// with expressions that perform value-initialization of the
 633 /// appropriate type, and finish off the InitListExpr formation.
 634 void
 635 InitListChecker::FillInEmptyInitializations(const InitializedEntity &Entity,
 636                                             InitListExpr *ILE,
 637                                             bool &RequiresSecondPass,
 638                                             InitListExpr *OuterILE,
 639                                             unsigned OuterIndex,
 640                                             bool FillWithNoInit) {
 641   assert((ILE->getType() != SemaRef.Context.VoidTy) &&
 642          "Should not have void type");
 643
 644   // If this is a nested initializer list, we might have changed its contents
 645   // (and therefore some of its properties, such as instantiation-dependence)
 646   // while filling it in. Inform the outer initializer list so that its state
 647   // can be updated to match.
 648   // FIXME: We should fully build the inner initializers before constructing
 649   // the outer InitListExpr instead of mutating AST nodes after they have
 650   // been used as subexpressions of other nodes.
 651   struct UpdateOuterILEWithUpdatedInit {
 652     InitListExpr *Outer;
 653     unsigned OuterIndex;
 654     ~UpdateOuterILEWithUpdatedInit() {
 655       if (Outer)
 656         Outer->setInit(OuterIndex, Outer->getInit(OuterIndex));
 657     }
 658   } UpdateOuterRAII = {OuterILE, OuterIndex};
 659
 660   // A transparent ILE is not performing aggregate initialization and should
 661   // not be filled in.
 662   if (ILE->isTransparent())
 663     return;
 664
 665   if (const RecordType *RType = ILE->getType()->getAs<RecordType>()) {
 666     const RecordDecl *RDecl = RType->getDecl();
 667     if (RDecl->isUnion() && ILE->getInitializedFieldInUnion())
 668       FillInEmptyInitForField(0, ILE->getInitializedFieldInUnion(),
 669                               Entity, ILE, RequiresSecondPass, FillWithNoInit);
 670     else if (RDecl->isUnion() && isa<CXXRecordDecl>(RDecl) &&
 671              cast<CXXRecordDecl>(RDecl)->hasInClassInitializer()) {
 672       for (auto *Field : RDecl->fields()) {
 673         if (Field->hasInClassInitializer()) {
 674           FillInEmptyInitForField(0, Field, Entity, ILE, RequiresSecondPass,
 675                                   FillWithNoInit);
 676           break;
 677         }
 678       }
 679     } else {
 680       // The fields beyond ILE->getNumInits() are default initialized, so in
 681       // order to leave them uninitialized, the ILE is expanded and the extra
 682       // fields are then filled with NoInitExpr.
 683       unsigned NumElems = numStructUnionElements(ILE->getType());
 684       if (RDecl->hasFlexibleArrayMember())
 685         ++NumElems;
 686       if (ILE->getNumInits() < NumElems)
 687         ILE->resizeInits(SemaRef.Context, NumElems);
 688
 689       unsigned Init = 0;
 690
 691       if (auto *CXXRD = dyn_cast<CXXRecordDecl>(RDecl)) {
 692         for (auto &Base : CXXRD->bases()) {
 693           if (hadError)
 694             return;
 695
 696           FillInEmptyInitForBase(Init, Base, Entity, ILE, RequiresSecondPass,
 697                                  FillWithNoInit);
 698           ++Init;
 699         }
 700       }
 701
 702       for (auto *Field : RDecl->fields()) {
 703         if (Field->isUnnamedBitfield())
 704           continue;
 705
 706         if (hadError)
 707           return;
 708
 709         FillInEmptyInitForField(Init, Field, Entity, ILE, RequiresSecondPass,
 710                                 FillWithNoInit);
 711         if (hadError)
 712           return;
 713
 714         ++Init;
 715
 716         // Only look at the first initialization of a union.
 717         if (RDecl->isUnion())
 718           break;
 719       }
 720     }
 721
 722     return;
 723   }
 724
 725   QualType ElementType;
 726
 727   InitializedEntity ElementEntity = Entity;
 728   unsigned NumInits = ILE->getNumInits();
 729   unsigned NumElements = NumInits;
 730   if (const ArrayType *AType = SemaRef.Context.getAsArrayType(ILE->getType())) {
 731     ElementType = AType->getElementType();
 732     if (const auto *CAType = dyn_cast<ConstantArrayType>(AType))
 733       NumElements = CAType->getSize().getZExtValue();
 734     // For an array new with an unknown bound, ask for one additional element
 735     // in order to populate the array filler.
 736     if (Entity.isVariableLengthArrayNew())
 737       ++NumElements;
 738     ElementEntity = InitializedEntity::InitializeElement(SemaRef.Context,
 739                                                          0, Entity);
 740   } else if (const VectorType *VType = ILE->getType()->getAs<VectorType>()) {
 741     ElementType = VType->getElementType();
 742     NumElements = VType->getNumElements();
 743     ElementEntity = InitializedEntity::InitializeElement(SemaRef.Context,
 744                                                          0, Entity);
 745   } else
 746     ElementType = ILE->getType();
 747
 748   for (unsigned Init = 0; Init != NumElements; ++Init) {
 749     if (hadError)
 750       return;
 751
 752     if (ElementEntity.getKind() == InitializedEntity::EK_ArrayElement ||
 753         ElementEntity.getKind() == InitializedEntity::EK_VectorElement)
 754       ElementEntity.setElementIndex(Init);
 755
 756     if (Init >= NumInits && ILE->hasArrayFiller())
 757       return;
 758
 759     Expr *InitExpr = (Init < NumInits ? ILE->getInit(Init) : nullptr);
 760     if (!InitExpr && Init < NumInits && ILE->hasArrayFiller())
 761       ILE->setInit(Init, ILE->getArrayFiller());
 762     else if (!InitExpr && !ILE->hasArrayFiller()) {
 763       Expr *Filler = nullptr;
 764
 765       if (FillWithNoInit)
 766         Filler = new (SemaRef.Context) NoInitExpr(ElementType);
 767       else {
 768         ExprResult ElementInit = PerformEmptyInit(SemaRef, ILE->getLocEnd(),
 769                                                   ElementEntity,
 770                                                   /*VerifyOnly*/false,
 771                                                   TreatUnavailableAsInvalid);
 772         if (ElementInit.isInvalid()) {
 773           hadError = true;
 774           return;
 775         }
 776
 777         Filler = ElementInit.getAs<Expr>();
 778       }
 779
 780       if (hadError) {
 781         // Do nothing
 782       } else if (Init < NumInits) {
 783         // For arrays, just set the expression used for value-initialization
 784         // of the "holes" in the array.
 785         if (ElementEntity.getKind() == InitializedEntity::EK_ArrayElement)
 786           ILE->setArrayFiller(Filler);
 787         else
 788           ILE->setInit(Init, Filler);
 789       } else {
 790         // For arrays, just set the expression used for value-initialization
 791         // of the rest of elements and exit.
 792         if (ElementEntity.getKind() == InitializedEntity::EK_ArrayElement) {
 793           ILE->setArrayFiller(Filler);
 794           return;
 795         }
 796
 797         if (!isa<ImplicitValueInitExpr>(Filler) && !isa<NoInitExpr>(Filler)) {
 798           // Empty initialization requires a constructor call, so
 799           // extend the initializer list to include the constructor
 800           // call and make a note that we'll need to take another pass
 801           // through the initializer list.
 802           ILE->updateInit(SemaRef.Context, Init, Filler);
 803           RequiresSecondPass = true;
 804         }
 805       }
 806     } else if (InitListExpr *InnerILE
 807                  = dyn_cast_or_null<InitListExpr>(InitExpr))
 808       FillInEmptyInitializations(ElementEntity, InnerILE, RequiresSecondPass,
 809                                  ILE, Init, FillWithNoInit);
 810     else if (DesignatedInitUpdateExpr *InnerDIUE
 811                  = dyn_cast_or_null<DesignatedInitUpdateExpr>(InitExpr))
 812       FillInEmptyInitializations(ElementEntity, InnerDIUE->getUpdater(),
 813                                  RequiresSecondPass, ILE, Init,
 814                                  /*FillWithNoInit =*/true);
 815   }
 816 }
 817
 818 InitListChecker::InitListChecker(Sema &S, const InitializedEntity &Entity,
 819                                  InitListExpr *IL, QualType &T,
 820                                  bool VerifyOnly,
 821                                  bool TreatUnavailableAsInvalid)
 822   : SemaRef(S), VerifyOnly(VerifyOnly),
 823     TreatUnavailableAsInvalid(TreatUnavailableAsInvalid) {
 824   // FIXME: Check that IL isn't already the semantic form of some other
 825   // InitListExpr. If it is, we'd create a broken AST.
 826
 827   hadError = false;
 828
 829   FullyStructuredList =
 830       getStructuredSubobjectInit(IL, 0, T, nullptr, 0, IL->getSourceRange());
 831   CheckExplicitInitList(Entity, IL, T, FullyStructuredList,
 832                         /*TopLevelObject=*/true);
 833
 834   if (!hadError && !VerifyOnly) {
 835     bool RequiresSecondPass = false;
 836     FillInEmptyInitializations(Entity, FullyStructuredList, RequiresSecondPass,
 837                                /*OuterILE=*/nullptr, /*OuterIndex=*/0);
 838     if (RequiresSecondPass && !hadError)
 839       FillInEmptyInitializations(Entity, FullyStructuredList,
 840                                  RequiresSecondPass, nullptr, 0);
 841   }
 842 }
 843
 844 int InitListChecker::numArrayElements(QualType DeclType) {
 845   // FIXME: use a proper constant
 846   int maxElements = 0x7FFFFFFF;
 847   if (const ConstantArrayType *CAT =
 848         SemaRef.Context.getAsConstantArrayType(DeclType)) {
 849     maxElements = static_cast<int>(CAT->getSize().getZExtValue());
 850   }
 851   return maxElements;
 852 }
 853
 854 int InitListChecker::numStructUnionElements(QualType DeclType) {
 855   RecordDecl *structDecl = DeclType->getAs<RecordType>()->getDecl();
 856   int InitializableMembers = 0;
 857   if (auto *CXXRD = dyn_cast<CXXRecordDecl>(structDecl))
 858     InitializableMembers += CXXRD->getNumBases();
 859   for (const auto *Field : structDecl->fields())
 860     if (!Field->isUnnamedBitfield())
 861       ++InitializableMembers;
 862
 863   if (structDecl->isUnion())
 864     return std::min(InitializableMembers, 1);
 865   return InitializableMembers - structDecl->hasFlexibleArrayMember();
 866 }
 867
 868 /// Determine whether Entity is an entity for which it is idiomatic to elide
 869 /// the braces in aggregate initialization.
 870 static bool isIdiomaticBraceElisionEntity(const InitializedEntity &Entity) {
 871   // Recursive initialization of the one and only field within an aggregate
 872   // class is considered idiomatic. This case arises in particular for
 873   // initialization of std::array, where the C++ standard suggests the idiom of
 874   //
 875   //   std::array<T, N> arr = {1, 2, 3};
 876   //
 877   // (where std::array is an aggregate struct containing a single array field.
 878
 879   // FIXME: Should aggregate initialization of a struct with a single
 880   // base class and no members also suppress the warning?
 881   if (Entity.getKind() != InitializedEntity::EK_Member || !Entity.getParent())
 882     return false;
 883
 884   auto *ParentRD =
 885       Entity.getParent()->getType()->castAs<RecordType>()->getDecl();
 886   if (CXXRecordDecl *CXXRD = dyn_cast<CXXRecordDecl>(ParentRD))
 887     if (CXXRD->getNumBases())
 888       return false;
 889
 890   auto FieldIt = ParentRD->field_begin();
 891   assert(FieldIt != ParentRD->field_end() &&
 892          "no fields but have initializer for member?");
 893   return ++FieldIt == ParentRD->field_end();
 894 }
 895
 896 /// Check whether the range of the initializer \p ParentIList from element
 897 /// \p Index onwards can be used to initialize an object of type \p T. Update
 898 /// \p Index to indicate how many elements of the list were consumed.
 899 ///
 900 /// This also fills in \p StructuredList, from element \p StructuredIndex
 901 /// onwards, with the fully-braced, desugared form of the initialization.
 902 void InitListChecker::CheckImplicitInitList(const InitializedEntity &Entity,
 903                                             InitListExpr *ParentIList,
 904                                             QualType T, unsigned &Index,
 905                                             InitListExpr *StructuredList,
 906                                             unsigned &StructuredIndex) {
 907   int maxElements = 0;
 908
 909   if (T->isArrayType())
 910     maxElements = numArrayElements(T);
 911   else if (T->isRecordType())
 912     maxElements = numStructUnionElements(T);
 913   else if (T->isVectorType())
 914     maxElements = T->getAs<VectorType>()->getNumElements();
 915   else
 916     llvm_unreachable("CheckImplicitInitList(): Illegal type");
 917
 918   if (maxElements == 0) {
 919     if (!VerifyOnly)
 920       SemaRef.Diag(ParentIList->getInit(Index)->getLocStart(),
 921                    diag::err_implicit_empty_initializer);
 922     ++Index;
 923     hadError = true;
 924     return;
 925   }
 926
 927   // Build a structured initializer list corresponding to this subobject.
 928   InitListExpr *StructuredSubobjectInitList
 929     = getStructuredSubobjectInit(ParentIList, Index, T, StructuredList,
 930                                  StructuredIndex,
 931           SourceRange(ParentIList->getInit(Index)->getLocStart(),
 932                       ParentIList->getSourceRange().getEnd()));
 933   unsigned StructuredSubobjectInitIndex = 0;
 934
 935   // Check the element types and build the structural subobject.
 936   unsigned StartIndex = Index;
 937   CheckListElementTypes(Entity, ParentIList, T,
 938                         /*SubobjectIsDesignatorContext=*/false, Index,
 939                         StructuredSubobjectInitList,
 940                         StructuredSubobjectInitIndex);
 941
 942   if (!VerifyOnly) {
 943     StructuredSubobjectInitList->setType(T);
 944
 945     unsigned EndIndex = (Index == StartIndex? StartIndex : Index - 1);
 946     // Update the structured sub-object initializer so that it's ending
 947     // range corresponds with the end of the last initializer it used.
 948     if (EndIndex < ParentIList->getNumInits() &&
 949         ParentIList->getInit(EndIndex)) {
 950       SourceLocation EndLoc
 951         = ParentIList->getInit(EndIndex)->getSourceRange().getEnd();
 952       StructuredSubobjectInitList->setRBraceLoc(EndLoc);
 953     }
 954
 955     // Complain about missing braces.
 956     if ((T->isArrayType() || T->isRecordType()) &&
 957         !ParentIList->isIdiomaticZeroInitializer(SemaRef.getLangOpts()) &&
 958         !isIdiomaticBraceElisionEntity(Entity)) {
 959       SemaRef.Diag(StructuredSubobjectInitList->getLocStart(),
 960                    diag::warn_missing_braces)
 961           << StructuredSubobjectInitList->getSourceRange()
 962           << FixItHint::CreateInsertion(
 963                  StructuredSubobjectInitList->getLocStart(), "{")
 964           << FixItHint::CreateInsertion(
 965                  SemaRef.getLocForEndOfToken(
 966                      StructuredSubobjectInitList->getLocEnd()),
 967                  "}");
 968     }
 969   }
 970 }
 971
 972 /// Warn that \p Entity was of scalar type and was initialized by a
 973 /// single-element braced initializer list.
 974 static void warnBracedScalarInit(Sema &S, const InitializedEntity &Entity,
 975                                  SourceRange Braces) {
 976   // Don't warn during template instantiation. If the initialization was
 977   // non-dependent, we warned during the initial parse; otherwise, the
 978   // type might not be scalar in some uses of the template.
 979   if (S.inTemplateInstantiation())
 980     return;
 981
 982   unsigned DiagID = 0;
 983
 984   switch (Entity.getKind()) {
 985   case InitializedEntity::EK_VectorElement:
 986   case InitializedEntity::EK_ComplexElement:
 987   case InitializedEntity::EK_ArrayElement:
 988   case InitializedEntity::EK_Parameter:
 989   case InitializedEntity::EK_Parameter_CF_Audited:
 990   case InitializedEntity::EK_Result:
 991     // Extra braces here are suspicious.
 992     DiagID = diag::warn_braces_around_scalar_init;
 993     break;
 994
 995   case InitializedEntity::EK_Member:
 996     // Warn on aggregate initialization but not on ctor init list or
 997     // default member initializer.
 998     if (Entity.getParent())
 999       DiagID = diag::warn_braces_around_scalar_init;
1000     break;
1001
1002   case InitializedEntity::EK_Variable:
1003   case InitializedEntity::EK_LambdaCapture:
1004     // No warning, might be direct-list-initialization.
1005     // FIXME: Should we warn for copy-list-initialization in these cases?
1006     break;
1007
1008   case InitializedEntity::EK_New:
1009   case InitializedEntity::EK_Temporary:
1010   case InitializedEntity::EK_CompoundLiteralInit:
1011     // No warning, braces are part of the syntax of the underlying construct.
1012     break;
1013
1014   case InitializedEntity::EK_RelatedResult:
1015     // No warning, we already warned when initializing the result.
1016     break;
1017
1018   case InitializedEntity::EK_Exception:
1019   case InitializedEntity::EK_Base:
1020   case InitializedEntity::EK_Delegating:
1021   case InitializedEntity::EK_BlockElement:
1022   case InitializedEntity::EK_LambdaToBlockConversionBlockElement:
1023   case InitializedEntity::EK_Binding:
1024   case InitializedEntity::EK_StmtExprResult:
1025     llvm_unreachable("unexpected braced scalar init");
1026   }
1027
1028   if (DiagID) {
1029     S.Diag(Braces.getBegin(), DiagID)
1030       << Braces
1031       << FixItHint::CreateRemoval(Braces.getBegin())
1032       << FixItHint::CreateRemoval(Braces.getEnd());
1033   }
1034 }
1035
1036 /// Check whether the initializer \p IList (that was written with explicit
1037 /// braces) can be used to initialize an object of type \p T.
1038 ///
1039 /// This also fills in \p StructuredList with the fully-braced, desugared
1040 /// form of the initialization.
1041 void InitListChecker::CheckExplicitInitList(const InitializedEntity &Entity,
1042                                             InitListExpr *IList, QualType &T,
1043                                             InitListExpr *StructuredList,
1044                                             bool TopLevelObject) {
1045   if (!VerifyOnly) {
1046     SyntacticToSemantic[IList] = StructuredList;
1047     StructuredList->setSyntacticForm(IList);
1048   }
1049
1050   unsigned Index = 0, StructuredIndex = 0;
1051   CheckListElementTypes(Entity, IList, T, /*SubobjectIsDesignatorContext=*/true,
1052                         Index, StructuredList, StructuredIndex, TopLevelObject);
1053   if (!VerifyOnly) {
1054     QualType ExprTy = T;
1055     if (!ExprTy->isArrayType())
1056       ExprTy = ExprTy.getNonLValueExprType(SemaRef.Context);
1057     IList->setType(ExprTy);
1058     StructuredList->setType(ExprTy);
1059   }
1060   if (hadError)
1061     return;
1062
1063   if (Index < IList->getNumInits()) {
1064     // We have leftover initializers
1065     if (VerifyOnly) {
1066       if (SemaRef.getLangOpts().CPlusPlus ||
1067           (SemaRef.getLangOpts().OpenCL &&
1068            IList->getType()->isVectorType())) {
1069         hadError = true;
1070       }
1071       return;
1072     }
1073
1074     if (StructuredIndex == 1 &&
1075         IsStringInit(StructuredList->getInit(0), T, SemaRef.Context) ==
1076             SIF_None) {
1077       unsigned DK = diag::ext_excess_initializers_in_char_array_initializer;
1078       if (SemaRef.getLangOpts().CPlusPlus) {
1079         DK = diag::err_excess_initializers_in_char_array_initializer;
1080         hadError = true;
1081       }
1082       // Special-case
1083       SemaRef.Diag(IList->getInit(Index)->getLocStart(), DK)
1084         << IList->getInit(Index)->getSourceRange();
1085     } else if (!T->isIncompleteType()) {
1086       // Don't complain for incomplete types, since we'll get an error
1087       // elsewhere
1088       QualType CurrentObjectType = StructuredList->getType();
1089       int initKind =
1090         CurrentObjectType->isArrayType()? 0 :
1091         CurrentObjectType->isVectorType()? 1 :
1092         CurrentObjectType->isScalarType()? 2 :
1093         CurrentObjectType->isUnionType()? 3 :
1094         4;
1095
1096       unsigned DK = diag::ext_excess_initializers;
1097       if (SemaRef.getLangOpts().CPlusPlus) {
1098         DK = diag::err_excess_initializers;
1099         hadError = true;
1100       }
1101       if (SemaRef.getLangOpts().OpenCL && initKind == 1) {
1102         DK = diag::err_excess_initializers;
1103         hadError = true;
1104       }
1105
1106       SemaRef.Diag(IList->getInit(Index)->getLocStart(), DK)
1107         << initKind << IList->getInit(Index)->getSourceRange();
1108     }
1109   }
1110
1111   if (!VerifyOnly && T->isScalarType() &&
1112       IList->getNumInits() == 1 && !isa<InitListExpr>(IList->getInit(0)))
1113     warnBracedScalarInit(SemaRef, Entity, IList->getSourceRange());
1114 }
1115
1116 void InitListChecker::CheckListElementTypes(const InitializedEntity &Entity,
1117                                             InitListExpr *IList,
1118                                             QualType &DeclType,
1119                                             bool SubobjectIsDesignatorContext,
1120                                             unsigned &Index,
1121                                             InitListExpr *StructuredList,
1122                                             unsigned &StructuredIndex,
1123                                             bool TopLevelObject) {
1124   if (DeclType->isAnyComplexType() && SubobjectIsDesignatorContext) {
1125     // Explicitly braced initializer for complex type can be real+imaginary
1126     // parts.
1127     CheckComplexType(Entity, IList, DeclType, Index,
1128                      StructuredList, StructuredIndex);
1129   } else if (DeclType->isScalarType()) {
1130     CheckScalarType(Entity, IList, DeclType, Index,
1131                     StructuredList, StructuredIndex);
1132   } else if (DeclType->isVectorType()) {
1133     CheckVectorType(Entity, IList, DeclType, Index,
1134                     StructuredList, StructuredIndex);
1135   } else if (DeclType->isRecordType()) {
1136     assert(DeclType->isAggregateType() &&
1137            "non-aggregate records should be handed in CheckSubElementType");
1138     RecordDecl *RD = DeclType->getAs<RecordType>()->getDecl();
1139     auto Bases =
1140         CXXRecordDecl::base_class_range(CXXRecordDecl::base_class_iterator(),
1141                                         CXXRecordDecl::base_class_iterator());
1142     if (auto *CXXRD = dyn_cast<CXXRecordDecl>(RD))
1143       Bases = CXXRD->bases();
1144     CheckStructUnionTypes(Entity, IList, DeclType, Bases, RD->field_begin(),
1145                           SubobjectIsDesignatorContext, Index, StructuredList,
1146                           StructuredIndex, TopLevelObject);
1147   } else if (DeclType->isArrayType()) {
1148     llvm::APSInt Zero(
1149                     SemaRef.Context.getTypeSize(SemaRef.Context.getSizeType()),
1150                     false);
1151     CheckArrayType(Entity, IList, DeclType, Zero,
1152                    SubobjectIsDesignatorContext, Index,
1153                    StructuredList, StructuredIndex);
1154   } else if (DeclType->isVoidType() || DeclType->isFunctionType()) {
1155     // This type is invalid, issue a diagnostic.
1156     ++Index;
1157     if (!VerifyOnly)
1158       SemaRef.Diag(IList->getLocStart(), diag::err_illegal_initializer_type)
1159         << DeclType;
1160     hadError = true;
1161   } else if (DeclType->isReferenceType()) {
1162     CheckReferenceType(Entity, IList, DeclType, Index,
1163                        StructuredList, StructuredIndex);
1164   } else if (DeclType->isObjCObjectType()) {
1165     if (!VerifyOnly)
1166       SemaRef.Diag(IList->getLocStart(), diag::err_init_objc_class)
1167         << DeclType;
1168     hadError = true;
1169   } else {
1170     if (!VerifyOnly)
1171       SemaRef.Diag(IList->getLocStart(), diag::err_illegal_initializer_type)
1172         << DeclType;
1173     hadError = true;
1174   }
1175 }
1176
1177 void InitListChecker::CheckSubElementType(const InitializedEntity &Entity,
1178                                           InitListExpr *IList,
1179                                           QualType ElemType,
1180                                           unsigned &Index,
1181                                           InitListExpr *StructuredList,
1182                                           unsigned &StructuredIndex) {
1183   Expr *expr = IList->getInit(Index);
1184
1185   if (ElemType->isReferenceType())
1186     return CheckReferenceType(Entity, IList, ElemType, Index,
1187                               StructuredList, StructuredIndex);
1188
1189   if (InitListExpr *SubInitList = dyn_cast<InitListExpr>(expr)) {
1190     if (SubInitList->getNumInits() == 1 &&
1191         IsStringInit(SubInitList->getInit(0), ElemType, SemaRef.Context) ==
1192         SIF_None) {
1193       expr = SubInitList->getInit(0);
1194     } else if (!SemaRef.getLangOpts().CPlusPlus) {
1195       InitListExpr *InnerStructuredList
1196         = getStructuredSubobjectInit(IList, Index, ElemType,
1197                                      StructuredList, StructuredIndex,
1198                                      SubInitList->getSourceRange(), true);
1199       CheckExplicitInitList(Entity, SubInitList, ElemType,
1200                             InnerStructuredList);
1201
1202       if (!hadError && !VerifyOnly) {
1203         bool RequiresSecondPass = false;
1204         FillInEmptyInitializations(Entity, InnerStructuredList,
1205                                    RequiresSecondPass, StructuredList,
1206                                    StructuredIndex);
1207         if (RequiresSecondPass && !hadError)
1208           FillInEmptyInitializations(Entity, InnerStructuredList,
1209                                      RequiresSecondPass, StructuredList,
1210                                      StructuredIndex);
1211       }
1212       ++StructuredIndex;
1213       ++Index;
1214       return;
1215     }
1216     // C++ initialization is handled later.
1217   } else if (isa<ImplicitValueInitExpr>(expr)) {
1218     // This happens during template instantiation when we see an InitListExpr
1219     // that we've already checked once.
1220     assert(SemaRef.Context.hasSameType(expr->getType(), ElemType) &&
1221            "found implicit initialization for the wrong type");
1222     if (!VerifyOnly)
1223       UpdateStructuredListElement(StructuredList, StructuredIndex, expr);
1224     ++Index;
1225     return;
1226   }
1227
1228   if (SemaRef.getLangOpts().CPlusPlus) {
1229     // C++ [dcl.init.aggr]p2:
1230     //   Each member is copy-initialized from the corresponding
1231     //   initializer-clause.
1232
1233     // FIXME: Better EqualLoc?
1234     InitializationKind Kind =
1235       InitializationKind::CreateCopy(expr->getLocStart(), SourceLocation());
1236     InitializationSequence Seq(SemaRef, Entity, Kind, expr,
1237                                /*TopLevelOfInitList*/ true);
1238
1239     // C++14 [dcl.init.aggr]p13:
1240     //   If the assignment-expression can initialize a member, the member is
1241     //   initialized. Otherwise [...] brace elision is assumed
1242     //
1243     // Brace elision is never performed if the element is not an
1244     // assignment-expression.
1245     if (Seq || isa<InitListExpr>(expr)) {
1246       if (!VerifyOnly) {
1247         ExprResult Result =
1248           Seq.Perform(SemaRef, Entity, Kind, expr);
1249         if (Result.isInvalid())
1250           hadError = true;
1251
1252         UpdateStructuredListElement(StructuredList, StructuredIndex,
1253                                     Result.getAs<Expr>());
1254       } else if (!Seq)
1255         hadError = true;
1256       ++Index;
1257       return;
1258     }
1259
1260     // Fall through for subaggregate initialization
1261   } else if (ElemType->isScalarType() || ElemType->isAtomicType()) {
1262     // FIXME: Need to handle atomic aggregate types with implicit init lists.
1263     return CheckScalarType(Entity, IList, ElemType, Index,
1264                            StructuredList, StructuredIndex);
1265   } else if (const ArrayType *arrayType =
1266                  SemaRef.Context.getAsArrayType(ElemType)) {
1267     // arrayType can be incomplete if we're initializing a flexible
1268     // array member.  There's nothing we can do with the completed
1269     // type here, though.
1270
1271     if (IsStringInit(expr, arrayType, SemaRef.Context) == SIF_None) {
1272       if (!VerifyOnly) {
1273         CheckStringInit(expr, ElemType, arrayType, SemaRef);
1274         UpdateStructuredListElement(StructuredList, StructuredIndex, expr);
1275       }
1276       ++Index;
1277       return;
1278     }
1279
1280     // Fall through for subaggregate initialization.
1281
1282   } else {
1283     assert((ElemType->isRecordType() || ElemType->isVectorType() ||
1284             ElemType->isOpenCLSpecificType()) && "Unexpected type");
1285
1286     // C99 6.7.8p13:
1287     //
1288     //   The initializer for a structure or union object that has
1289     //   automatic storage duration shall be either an initializer
1290     //   list as described below, or a single expression that has
1291     //   compatible structure or union type. In the latter case, the
1292     //   initial value of the object, including unnamed members, is
1293     //   that of the expression.
1294     ExprResult ExprRes = expr;
1295     if (SemaRef.CheckSingleAssignmentConstraints(
1296             ElemType, ExprRes, !VerifyOnly) != Sema::Incompatible) {
1297       if (ExprRes.isInvalid())
1298         hadError = true;
1299       else {
1300         ExprRes = SemaRef.DefaultFunctionArrayLvalueConversion(ExprRes.get());
1301           if (ExprRes.isInvalid())
1302             hadError = true;
1303       }
1304       UpdateStructuredListElement(StructuredList, StructuredIndex,
1305                                   ExprRes.getAs<Expr>());
1306       ++Index;
1307       return;
1308     }
1309     ExprRes.get();
1310     // Fall through for subaggregate initialization
1311   }
1312
1313   // C++ [dcl.init.aggr]p12:
1314   //
1315   //   [...] Otherwise, if the member is itself a non-empty
1316   //   subaggregate, brace elision is assumed and the initializer is
1317   //   considered for the initialization of the first member of
1318   //   the subaggregate.
1319   // OpenCL vector initializer is handled elsewhere.
1320   if ((!SemaRef.getLangOpts().OpenCL && ElemType->isVectorType()) ||
1321       ElemType->isAggregateType()) {
1322     CheckImplicitInitList(Entity, IList, ElemType, Index, StructuredList,
1323                           StructuredIndex);
1324     ++StructuredIndex;
1325   } else {
1326     if (!VerifyOnly) {
1327       // We cannot initialize this element, so let
1328       // PerformCopyInitialization produce the appropriate diagnostic.
1329       SemaRef.PerformCopyInitialization(Entity, SourceLocation(), expr,
1330                                         /*TopLevelOfInitList=*/true);
1331     }
1332     hadError = true;
1333     ++Index;
1334     ++StructuredIndex;
1335   }
1336 }
1337
1338 void InitListChecker::CheckComplexType(const InitializedEntity &Entity,
1339                                        InitListExpr *IList, QualType DeclType,
1340                                        unsigned &Index,
1341                                        InitListExpr *StructuredList,
1342                                        unsigned &StructuredIndex) {
1343   assert(Index == 0 && "Index in explicit init list must be zero");
1344
1345   // As an extension, clang supports complex initializers, which initialize
1346   // a complex number component-wise.  When an explicit initializer list for
1347   // a complex number contains two two initializers, this extension kicks in:
1348   // it exepcts the initializer list to contain two elements convertible to
1349   // the element type of the complex type. The first element initializes
1350   // the real part, and the second element intitializes the imaginary part.
1351
1352   if (IList->getNumInits() != 2)
1353     return CheckScalarType(Entity, IList, DeclType, Index, StructuredList,
1354                            StructuredIndex);
1355
1356   // This is an extension in C.  (The builtin _Complex type does not exist
1357   // in the C++ standard.)
1358   if (!SemaRef.getLangOpts().CPlusPlus && !VerifyOnly)
1359     SemaRef.Diag(IList->getLocStart(), diag::ext_complex_component_init)
1360       << IList->getSourceRange();
1361
1362   // Initialize the complex number.
1363   QualType elementType = DeclType->getAs<ComplexType>()->getElementType();
1364   InitializedEntity ElementEntity =
1365     InitializedEntity::InitializeElement(SemaRef.Context, 0, Entity);
1366
1367   for (unsigned i = 0; i < 2; ++i) {
1368     ElementEntity.setElementIndex(Index);
1369     CheckSubElementType(ElementEntity, IList, elementType, Index,
1370                         StructuredList, StructuredIndex);
1371   }
1372 }
1373
1374 void InitListChecker::CheckScalarType(const InitializedEntity &Entity,
1375                                       InitListExpr *IList, QualType DeclType,
1376                                       unsigned &Index,
1377                                       InitListExpr *StructuredList,
1378                                       unsigned &StructuredIndex) {
1379   if (Index >= IList->getNumInits()) {
1380     if (!VerifyOnly)
1381       SemaRef.Diag(IList->getLocStart(),
1382                    SemaRef.getLangOpts().CPlusPlus11 ?
1383                      diag::warn_cxx98_compat_empty_scalar_initializer :
1384                      diag::err_empty_scalar_initializer)
1385         << IList->getSourceRange();
1386     hadError = !SemaRef.getLangOpts().CPlusPlus11;
1387     ++Index;
1388     ++StructuredIndex;
1389     return;
1390   }
1391
1392   Expr *expr = IList->getInit(Index);
1393   if (InitListExpr *SubIList = dyn_cast<InitListExpr>(expr)) {
1394     // FIXME: This is invalid, and accepting it causes overload resolution
1395     // to pick the wrong overload in some corner cases.
1396     if (!VerifyOnly)
1397       SemaRef.Diag(SubIList->getLocStart(),
1398                    diag::ext_many_braces_around_scalar_init)
1399         << SubIList->getSourceRange();
1400
1401     CheckScalarType(Entity, SubIList, DeclType, Index, StructuredList,
1402                     StructuredIndex);
1403     return;
1404   } else if (isa<DesignatedInitExpr>(expr)) {
1405     if (!VerifyOnly)
1406       SemaRef.Diag(expr->getLocStart(),
1407                    diag::err_designator_for_scalar_init)
1408         << DeclType << expr->getSourceRange();
1409     hadError = true;
1410     ++Index;
1411     ++StructuredIndex;
1412     return;
1413   }
1414
1415   if (VerifyOnly) {
1416     if (!SemaRef.CanPerformCopyInitialization(Entity,expr))
1417       hadError = true;
1418     ++Index;
1419     return;
1420   }
1421
1422   ExprResult Result =
1423     SemaRef.PerformCopyInitialization(Entity, expr->getLocStart(), expr,
1424                                       /*TopLevelOfInitList=*/true);
1425
1426   Expr *ResultExpr = nullptr;
1427
1428   if (Result.isInvalid())
1429     hadError = true; // types weren't compatible.
1430   else {
1431     ResultExpr = Result.getAs<Expr>();
1432
1433     if (ResultExpr != expr) {
1434       // The type was promoted, update initializer list.
1435       IList->setInit(Index, ResultExpr);
1436     }
1437   }
1438   if (hadError)
1439     ++StructuredIndex;
1440   else
1441     UpdateStructuredListElement(StructuredList, StructuredIndex, ResultExpr);
1442   ++Index;
1443 }
1444
1445 void InitListChecker::CheckReferenceType(const InitializedEntity &Entity,
1446                                          InitListExpr *IList, QualType DeclType,
1447                                          unsigned &Index,
1448                                          InitListExpr *StructuredList,
1449                                          unsigned &StructuredIndex) {
1450   if (Index >= IList->getNumInits()) {
1451     // FIXME: It would be wonderful if we could point at the actual member. In
1452     // general, it would be useful to pass location information down the stack,
1453     // so that we know the location (or decl) of the "current object" being
1454     // initialized.
1455     if (!VerifyOnly)
1456       SemaRef.Diag(IList->getLocStart(),
1457                     diag::err_init_reference_member_uninitialized)
1458         << DeclType
1459         << IList->getSourceRange();
1460     hadError = true;
1461     ++Index;
1462     ++StructuredIndex;
1463     return;
1464   }
1465
1466   Expr *expr = IList->getInit(Index);
1467   if (isa<InitListExpr>(expr) && !SemaRef.getLangOpts().CPlusPlus11) {
1468     if (!VerifyOnly)
1469       SemaRef.Diag(IList->getLocStart(), diag::err_init_non_aggr_init_list)
1470         << DeclType << IList->getSourceRange();
1471     hadError = true;
1472     ++Index;
1473     ++StructuredIndex;
1474     return;
1475   }
1476
1477   if (VerifyOnly) {
1478     if (!SemaRef.CanPerformCopyInitialization(Entity,expr))
1479       hadError = true;
1480     ++Index;
1481     return;
1482   }
1483
1484   ExprResult Result =
1485       SemaRef.PerformCopyInitialization(Entity, expr->getLocStart(), expr,
1486                                         /*TopLevelOfInitList=*/true);
1487
1488   if (Result.isInvalid())
1489     hadError = true;
1490
1491   expr = Result.getAs<Expr>();
1492   IList->setInit(Index, expr);
1493
1494   if (hadError)
1495     ++StructuredIndex;
1496   else
1497     UpdateStructuredListElement(StructuredList, StructuredIndex, expr);
1498   ++Index;
1499 }
1500
1501 void InitListChecker::CheckVectorType(const InitializedEntity &Entity,
1502                                       InitListExpr *IList, QualType DeclType,
1503                                       unsigned &Index,
1504                                       InitListExpr *StructuredList,
1505                                       unsigned &StructuredIndex) {
1506   const VectorType *VT = DeclType->getAs<VectorType>();
1507   unsigned maxElements = VT->getNumElements();
1508   unsigned numEltsInit = 0;
1509   QualType elementType = VT->getElementType();
1510
1511   if (Index >= IList->getNumInits()) {
1512     // Make sure the element type can be value-initialized.
1513     if (VerifyOnly)
1514       CheckEmptyInitializable(
1515           InitializedEntity::InitializeElement(SemaRef.Context, 0, Entity),
1516           IList->getLocEnd());
1517     return;
1518   }
1519
1520   if (!SemaRef.getLangOpts().OpenCL) {
1521     // If the initializing element is a vector, try to copy-initialize
1522     // instead of breaking it apart (which is doomed to failure anyway).
1523     Expr *Init = IList->getInit(Index);
1524     if (!isa<InitListExpr>(Init) && Init->getType()->isVectorType()) {
1525       if (VerifyOnly) {
1526         if (!SemaRef.CanPerformCopyInitialization(Entity, Init))
1527           hadError = true;
1528         ++Index;
1529         return;
1530       }
1531
1532   ExprResult Result =
1533       SemaRef.PerformCopyInitialization(Entity, Init->getLocStart(), Init,
1534                                         /*TopLevelOfInitList=*/true);
1535
1536       Expr *ResultExpr = nullptr;
1537       if (Result.isInvalid())
1538         hadError = true; // types weren't compatible.
1539       else {
1540         ResultExpr = Result.getAs<Expr>();
1541
1542         if (ResultExpr != Init) {
1543           // The type was promoted, update initializer list.
1544           IList->setInit(Index, ResultExpr);
1545         }
1546       }
1547       if (hadError)
1548         ++StructuredIndex;
1549       else
1550         UpdateStructuredListElement(StructuredList, StructuredIndex,
1551                                     ResultExpr);
1552       ++Index;
1553       return;
1554     }
1555
1556     InitializedEntity ElementEntity =
1557       InitializedEntity::InitializeElement(SemaRef.Context, 0, Entity);
1558
1559     for (unsigned i = 0; i < maxElements; ++i, ++numEltsInit) {
1560       // Don't attempt to go past the end of the init list
1561       if (Index >= IList->getNumInits()) {
1562         if (VerifyOnly)
1563           CheckEmptyInitializable(ElementEntity, IList->getLocEnd());
1564         break;
1565       }
1566
1567       ElementEntity.setElementIndex(Index);
1568       CheckSubElementType(ElementEntity, IList, elementType, Index,
1569                           StructuredList, StructuredIndex);
1570     }
1571
1572     if (VerifyOnly)
1573       return;
1574
1575     bool isBigEndian = SemaRef.Context.getTargetInfo().isBigEndian();
1576     const VectorType *T = Entity.getType()->getAs<VectorType>();
1577     if (isBigEndian && (T->getVectorKind() == VectorType::NeonVector ||
1578                         T->getVectorKind() == VectorType::NeonPolyVector)) {
1579       // The ability to use vector initializer lists is a GNU vector extension
1580       // and is unrelated to the NEON intrinsics in arm_neon.h. On little
1581       // endian machines it works fine, however on big endian machines it
1582       // exhibits surprising behaviour:
1583       //
1584       //   uint32x2_t x = {42, 64};
1585       //   return vget_lane_u32(x, 0); // Will return 64.
1586       //
1587       // Because of this, explicitly call out that it is non-portable.
1588       //
1589       SemaRef.Diag(IList->getLocStart(),
1590                    diag::warn_neon_vector_initializer_non_portable);
1591
1592       const char *typeCode;
1593       unsigned typeSize = SemaRef.Context.getTypeSize(elementType);
1594
1595       if (elementType->isFloatingType())
1596         typeCode = "f";
1597       else if (elementType->isSignedIntegerType())
1598         typeCode = "s";
1599       else if (elementType->isUnsignedIntegerType())
1600         typeCode = "u";
1601       else
1602         llvm_unreachable("Invalid element type!");
1603
1604       SemaRef.Diag(IList->getLocStart(),
1605                    SemaRef.Context.getTypeSize(VT) > 64 ?
1606                    diag::note_neon_vector_initializer_non_portable_q :
1607                    diag::note_neon_vector_initializer_non_portable)
1608         << typeCode << typeSize;
1609     }
1610
1611     return;
1612   }
1613
1614   InitializedEntity ElementEntity =
1615     InitializedEntity::InitializeElement(SemaRef.Context, 0, Entity);
1616
1617   // OpenCL initializers allows vectors to be constructed from vectors.
1618   for (unsigned i = 0; i < maxElements; ++i) {
1619     // Don't attempt to go past the end of the init list
1620     if (Index >= IList->getNumInits())
1621       break;
1622
1623     ElementEntity.setElementIndex(Index);
1624
1625     QualType IType = IList->getInit(Index)->getType();
1626     if (!IType->isVectorType()) {
1627       CheckSubElementType(ElementEntity, IList, elementType, Index,
1628                           StructuredList, StructuredIndex);
1629       ++numEltsInit;
1630     } else {
1631       QualType VecType;
1632       const VectorType *IVT = IType->getAs<VectorType>();
1633       unsigned numIElts = IVT->getNumElements();
1634
1635       if (IType->isExtVectorType())
1636         VecType = SemaRef.Context.getExtVectorType(elementType, numIElts);
1637       else
1638         VecType = SemaRef.Context.getVectorType(elementType, numIElts,
1639                                                 IVT->getVectorKind());
1640       CheckSubElementType(ElementEntity, IList, VecType, Index,
1641                           StructuredList, StructuredIndex);
1642       numEltsInit += numIElts;
1643     }
1644   }
1645
1646   // OpenCL requires all elements to be initialized.
1647   if (numEltsInit != maxElements) {
1648     if (!VerifyOnly)
1649       SemaRef.Diag(IList->getLocStart(),
1650                    diag::err_vector_incorrect_num_initializers)
1651         << (numEltsInit < maxElements) << maxElements << numEltsInit;
1652     hadError = true;
1653   }
1654 }
1655
1656 void InitListChecker::CheckArrayType(const InitializedEntity &Entity,
1657                                      InitListExpr *IList, QualType &DeclType,
1658                                      llvm::APSInt elementIndex,
1659                                      bool SubobjectIsDesignatorContext,
1660                                      unsigned &Index,
1661                                      InitListExpr *StructuredList,
1662                                      unsigned &StructuredIndex) {
1663   const ArrayType *arrayType = SemaRef.Context.getAsArrayType(DeclType);
1664
1665   // Check for the special-case of initializing an array with a string.
1666   if (Index < IList->getNumInits()) {
1667     if (IsStringInit(IList->getInit(Index), arrayType, SemaRef.Context) ==
1668         SIF_None) {
1669       // We place the string literal directly into the resulting
1670       // initializer list. This is the only place where the structure
1671       // of the structured initializer list doesn't match exactly,
1672       // because doing so would involve allocating one character
1673       // constant for each string.
1674       if (!VerifyOnly) {
1675         CheckStringInit(IList->getInit(Index), DeclType, arrayType, SemaRef);
1676         UpdateStructuredListElement(StructuredList, StructuredIndex,
1677                                     IList->getInit(Index));
1678         StructuredList->resizeInits(SemaRef.Context, StructuredIndex);
1679       }
1680       ++Index;
1681       return;
1682     }
1683   }
1684   if (const VariableArrayType *VAT = dyn_cast<VariableArrayType>(arrayType)) {
1685     // Check for VLAs; in standard C it would be possible to check this
1686     // earlier, but I don't know where clang accepts VLAs (gcc accepts
1687     // them in all sorts of strange places).
1688     if (!VerifyOnly)
1689       SemaRef.Diag(VAT->getSizeExpr()->getLocStart(),
1690                     diag::err_variable_object_no_init)
1691         << VAT->getSizeExpr()->getSourceRange();
1692     hadError = true;
1693     ++Index;
1694     ++StructuredIndex;
1695     return;
1696   }
1697
1698   // We might know the maximum number of elements in advance.
1699   llvm::APSInt maxElements(elementIndex.getBitWidth(),
1700                            elementIndex.isUnsigned());
1701   bool maxElementsKnown = false;
1702   if (const ConstantArrayType *CAT = dyn_cast<ConstantArrayType>(arrayType)) {
1703     maxElements = CAT->getSize();
1704     elementIndex = elementIndex.extOrTrunc(maxElements.getBitWidth());
1705     elementIndex.setIsUnsigned(maxElements.isUnsigned());
1706     maxElementsKnown = true;
1707   }
1708
1709   QualType elementType = arrayType->getElementType();
1710   while (Index < IList->getNumInits()) {
1711     Expr *Init = IList->getInit(Index);
1712     if (DesignatedInitExpr *DIE = dyn_cast<DesignatedInitExpr>(Init)) {
1713       // If we're not the subobject that matches up with the '{' for
1714       // the designator, we shouldn't be handling the
1715       // designator. Return immediately.
1716       if (!SubobjectIsDesignatorContext)
1717         return;
1718
1719       // Handle this designated initializer. elementIndex will be
1720       // updated to be the next array element we'll initialize.
1721       if (CheckDesignatedInitializer(Entity, IList, DIE, 0,
1722                                      DeclType, nullptr, &elementIndex, Index,
1723                                      StructuredList, StructuredIndex, true,
1724                                      false)) {
1725         hadError = true;
1726         continue;
1727       }
1728
1729       if (elementIndex.getBitWidth() > maxElements.getBitWidth())
1730         maxElements = maxElements.extend(elementIndex.getBitWidth());
1731       else if (elementIndex.getBitWidth() < maxElements.getBitWidth())
1732         elementIndex = elementIndex.extend(maxElements.getBitWidth());
1733       elementIndex.setIsUnsigned(maxElements.isUnsigned());
1734
1735       // If the array is of incomplete type, keep track of the number of
1736       // elements in the initializer.
1737       if (!maxElementsKnown && elementIndex > maxElements)
1738         maxElements = elementIndex;
1739
1740       continue;
1741     }
1742
1743     // If we know the maximum number of elements, and we've already
1744     // hit it, stop consuming elements in the initializer list.
1745     if (maxElementsKnown && elementIndex == maxElements)
1746       break;
1747
1748     InitializedEntity ElementEntity =
1749       InitializedEntity::InitializeElement(SemaRef.Context, StructuredIndex,
1750                                            Entity);
1751     // Check this element.
1752     CheckSubElementType(ElementEntity, IList, elementType, Index,
1753                         StructuredList, StructuredIndex);
1754     ++elementIndex;
1755
1756     // If the array is of incomplete type, keep track of the number of
1757     // elements in the initializer.
1758     if (!maxElementsKnown && elementIndex > maxElements)
1759       maxElements = elementIndex;
1760   }
1761   if (!hadError && DeclType->isIncompleteArrayType() && !VerifyOnly) {
1762     // If this is an incomplete array type, the actual type needs to
1763     // be calculated here.
1764     llvm::APSInt Zero(maxElements.getBitWidth(), maxElements.isUnsigned());
1765     if (maxElements == Zero && !Entity.isVariableLengthArrayNew()) {
1766       // Sizing an array implicitly to zero is not allowed by ISO C,
1767       // but is supported by GNU.
1768       SemaRef.Diag(IList->getLocStart(),
1769                     diag::ext_typecheck_zero_array_size);
1770     }
1771
1772     DeclType = SemaRef.Context.getConstantArrayType(elementType, maxElements,
1773                                                      ArrayType::Normal, 0);
1774   }
1775   if (!hadError && VerifyOnly) {
1776     // If there are any members of the array that get value-initialized, check
1777     // that is possible. That happens if we know the bound and don't have
1778     // enough elements, or if we're performing an array new with an unknown
1779     // bound.
1780     // FIXME: This needs to detect holes left by designated initializers too.
1781     if ((maxElementsKnown && elementIndex < maxElements) ||
1782         Entity.isVariableLengthArrayNew())
1783       CheckEmptyInitializable(InitializedEntity::InitializeElement(
1784                                                   SemaRef.Context, 0, Entity),
1785                               IList->getLocEnd());
1786   }
1787 }
1788
1789 bool InitListChecker::CheckFlexibleArrayInit(const InitializedEntity &Entity,
1790                                              Expr *InitExpr,
1791                                              FieldDecl *Field,
1792                                              bool TopLevelObject) {
1793   // Handle GNU flexible array initializers.
1794   unsigned FlexArrayDiag;
1795   if (isa<InitListExpr>(InitExpr) &&
1796       cast<InitListExpr>(InitExpr)->getNumInits() == 0) {
1797     // Empty flexible array init always allowed as an extension
1798     FlexArrayDiag = diag::ext_flexible_array_init;
1799   } else if (SemaRef.getLangOpts().CPlusPlus) {
1800     // Disallow flexible array init in C++; it is not required for gcc
1801     // compatibility, and it needs work to IRGen correctly in general.
1802     FlexArrayDiag = diag::err_flexible_array_init;
1803   } else if (!TopLevelObject) {
1804     // Disallow flexible array init on non-top-level object
1805     FlexArrayDiag = diag::err_flexible_array_init;
1806   } else if (Entity.getKind() != InitializedEntity::EK_Variable) {
1807     // Disallow flexible array init on anything which is not a variable.
1808     FlexArrayDiag = diag::err_flexible_array_init;
1809   } else if (cast<VarDecl>(Entity.getDecl())->hasLocalStorage()) {
1810     // Disallow flexible array init on local variables.
1811     FlexArrayDiag = diag::err_flexible_array_init;
1812   } else {
1813     // Allow other cases.
1814     FlexArrayDiag = diag::ext_flexible_array_init;
1815   }
1816
1817   if (!VerifyOnly) {
1818     SemaRef.Diag(InitExpr->getLocStart(),
1819                  FlexArrayDiag)
1820       << InitExpr->getLocStart();
1821     SemaRef.Diag(Field->getLocation(), diag::note_flexible_array_member)
1822       << Field;
1823   }
1824
1825   return FlexArrayDiag != diag::ext_flexible_array_init;
1826 }
1827
1828 void InitListChecker::CheckStructUnionTypes(
1829     const InitializedEntity &Entity, InitListExpr *IList, QualType DeclType,
1830     CXXRecordDecl::base_class_range Bases, RecordDecl::field_iterator Field,
1831     bool SubobjectIsDesignatorContext, unsigned &Index,
1832     InitListExpr *StructuredList, unsigned &StructuredIndex,
1833     bool TopLevelObject) {
1834   RecordDecl *structDecl = DeclType->getAs<RecordType>()->getDecl();
1835
1836   // If the record is invalid, some of it's members are invalid. To avoid
1837   // confusion, we forgo checking the intializer for the entire record.
1838   if (structDecl->isInvalidDecl()) {
1839     // Assume it was supposed to consume a single initializer.
1840     ++Index;
1841     hadError = true;
1842     return;
1843   }
1844
1845   if (DeclType->isUnionType() && IList->getNumInits() == 0) {
1846     RecordDecl *RD = DeclType->getAs<RecordType>()->getDecl();
1847
1848     // If there's a default initializer, use it.
1849     if (isa<CXXRecordDecl>(RD) && cast<CXXRecordDecl>(RD)->hasInClassInitializer()) {
1850       if (VerifyOnly)
1851         return;
1852       for (RecordDecl::field_iterator FieldEnd = RD->field_end();
1853            Field != FieldEnd; ++Field) {
1854         if (Field->hasInClassInitializer()) {
1855           StructuredList->setInitializedFieldInUnion(*Field);
1856           // FIXME: Actually build a CXXDefaultInitExpr?
1857           return;
1858         }
1859       }
1860     }
1861
1862     // Value-initialize the first member of the union that isn't an unnamed
1863     // bitfield.
1864     for (RecordDecl::field_iterator FieldEnd = RD->field_end();
1865          Field != FieldEnd; ++Field) {
1866       if (!Field->isUnnamedBitfield()) {
1867         if (VerifyOnly)
1868           CheckEmptyInitializable(
1869               InitializedEntity::InitializeMember(*Field, &Entity),
1870               IList->getLocEnd());
1871         else
1872           StructuredList->setInitializedFieldInUnion(*Field);
1873         break;
1874       }
1875     }
1876     return;
1877   }
1878
1879   bool InitializedSomething = false;
1880
1881   // If we have any base classes, they are initialized prior to the fields.
1882   for (auto &Base : Bases) {
1883     Expr *Init = Index < IList->getNumInits() ? IList->getInit(Index) : nullptr;
1884     SourceLocation InitLoc = Init ? Init->getLocStart() : IList->getLocEnd();
1885
1886     // Designated inits always initialize fields, so if we see one, all
1887     // remaining base classes have no explicit initializer.
1888     if (Init && isa<DesignatedInitExpr>(Init))
1889       Init = nullptr;
1890
1891     InitializedEntity BaseEntity = InitializedEntity::InitializeBase(
1892         SemaRef.Context, &Base, false, &Entity);
1893     if (Init) {
1894       CheckSubElementType(BaseEntity, IList, Base.getType(), Index,
1895                           StructuredList, StructuredIndex);
1896       InitializedSomething = true;
1897     } else if (VerifyOnly) {
1898       CheckEmptyInitializable(BaseEntity, InitLoc);
1899     }
1900   }
1901
1902   // If structDecl is a forward declaration, this loop won't do
1903   // anything except look at designated initializers; That's okay,
1904   // because an error should get printed out elsewhere. It might be
1905   // worthwhile to skip over the rest of the initializer, though.
1906   RecordDecl *RD = DeclType->getAs<RecordType>()->getDecl();
1907   RecordDecl::field_iterator FieldEnd = RD->field_end();
1908   bool CheckForMissingFields =
1909     !IList->isIdiomaticZeroInitializer(SemaRef.getLangOpts());
1910
1911   while (Index < IList->getNumInits()) {
1912     Expr *Init = IList->getInit(Index);
1913
1914     if (DesignatedInitExpr *DIE = dyn_cast<DesignatedInitExpr>(Init)) {
1915       // If we're not the subobject that matches up with the '{' for
1916       // the designator, we shouldn't be handling the
1917       // designator. Return immediately.
1918       if (!SubobjectIsDesignatorContext)
1919         return;
1920
1921       // Handle this designated initializer. Field will be updated to
1922       // the next field that we'll be initializing.
1923       if (CheckDesignatedInitializer(Entity, IList, DIE, 0,
1924                                      DeclType, &Field, nullptr, Index,
1925                                      StructuredList, StructuredIndex,
1926                                      true, TopLevelObject))
1927         hadError = true;
1928
1929       InitializedSomething = true;
1930
1931       // Disable check for missing fields when designators are used.
1932       // This matches gcc behaviour.
1933       CheckForMissingFields = false;
1934       continue;
1935     }
1936
1937     if (Field == FieldEnd) {
1938       // We've run out of fields. We're done.
1939       break;
1940     }
1941
1942     // We've already initialized a member of a union. We're done.
1943     if (InitializedSomething && DeclType->isUnionType())
1944       break;
1945
1946     // If we've hit the flexible array member at the end, we're done.
1947     if (Field->getType()->isIncompleteArrayType())
1948       break;
1949
1950     if (Field->isUnnamedBitfield()) {
1951       // Don't initialize unnamed bitfields, e.g. "int : 20;"
1952       ++Field;
1953       continue;
1954     }
1955
1956     // Make sure we can use this declaration.
1957     bool InvalidUse;
1958     if (VerifyOnly)
1959       InvalidUse = !SemaRef.CanUseDecl(*Field, TreatUnavailableAsInvalid);
1960     else
1961       InvalidUse = SemaRef.DiagnoseUseOfDecl(*Field,
1962                                           IList->getInit(Index)->getLocStart());
1963     if (InvalidUse) {
1964       ++Index;
1965       ++Field;
1966       hadError = true;
1967       continue;
1968     }
1969
1970     InitializedEntity MemberEntity =
1971       InitializedEntity::InitializeMember(*Field, &Entity);
1972     CheckSubElementType(MemberEntity, IList, Field->getType(), Index,
1973                         StructuredList, StructuredIndex);
1974     InitializedSomething = true;
1975
1976     if (DeclType->isUnionType() && !VerifyOnly) {
1977       // Initialize the first field within the union.
1978       StructuredList->setInitializedFieldInUnion(*Field);
1979     }
1980
1981     ++Field;
1982   }
1983
1984   // Emit warnings for missing struct field initializers.
1985   if (!VerifyOnly && InitializedSomething && CheckForMissingFields &&
1986       Field != FieldEnd && !Field->getType()->isIncompleteArrayType() &&
1987       !DeclType->isUnionType()) {
1988     // It is possible we have one or more unnamed bitfields remaining.
1989     // Find first (if any) named field and emit warning.
1990     for (RecordDecl::field_iterator it = Field, end = RD->field_end();
1991          it != end; ++it) {
1992       if (!it->isUnnamedBitfield() && !it->hasInClassInitializer()) {
1993         SemaRef.Diag(IList->getSourceRange().getEnd(),
1994                      diag::warn_missing_field_initializers) << *it;
1995         break;
1996       }
1997     }
1998   }
1999
2000   // Check that any remaining fields can be value-initialized.
2001   if (VerifyOnly && Field != FieldEnd && !DeclType->isUnionType() &&
2002       !Field->getType()->isIncompleteArrayType()) {
2003     // FIXME: Should check for holes left by designated initializers too.
2004     for (; Field != FieldEnd && !hadError; ++Field) {
2005       if (!Field->isUnnamedBitfield() && !Field->hasInClassInitializer())
2006         CheckEmptyInitializable(
2007             InitializedEntity::InitializeMember(*Field, &Entity),
2008             IList->getLocEnd());
2009     }
2010   }
2011
2012   if (Field == FieldEnd || !Field->getType()->isIncompleteArrayType() ||
2013       Index >= IList->getNumInits())
2014     return;
2015
2016   if (CheckFlexibleArrayInit(Entity, IList->getInit(Index), *Field,
2017                              TopLevelObject)) {
2018     hadError = true;
2019     ++Index;
2020     return;
2021   }
2022
2023   InitializedEntity MemberEntity =
2024     InitializedEntity::InitializeMember(*Field, &Entity);
2025
2026   if (isa<InitListExpr>(IList->getInit(Index)))
2027     CheckSubElementType(MemberEntity, IList, Field->getType(), Index,
2028                         StructuredList, StructuredIndex);
2029   else
2030     CheckImplicitInitList(MemberEntity, IList, Field->getType(), Index,
2031                           StructuredList, StructuredIndex);
2032 }
2033
2034 /// Expand a field designator that refers to a member of an
2035 /// anonymous struct or union into a series of field designators that
2036 /// refers to the field within the appropriate subobject.
2037 ///
2038 static void ExpandAnonymousFieldDesignator(Sema &SemaRef,
2039                                            DesignatedInitExpr *DIE,
2040                                            unsigned DesigIdx,
2041                                            IndirectFieldDecl *IndirectField) {
2042   typedef DesignatedInitExpr::Designator Designator;
2043
2044   // Build the replacement designators.
2045   SmallVector<Designator, 4> Replacements;
2046   for (IndirectFieldDecl::chain_iterator PI = IndirectField->chain_begin(),
2047        PE = IndirectField->chain_end(); PI != PE; ++PI) {
2048     if (PI + 1 == PE)
2049       Replacements.push_back(Designator((IdentifierInfo *)nullptr,
2050                                     DIE->getDesignator(DesigIdx)->getDotLoc(),
2051                                 DIE->getDesignator(DesigIdx)->getFieldLoc()));
2052     else
2053       Replacements.push_back(Designator((IdentifierInfo *)nullptr,
2054                                         SourceLocation(), SourceLocation()));
2055     assert(isa<FieldDecl>(*PI));
2056     Replacements.back().setField(cast<FieldDecl>(*PI));
2057   }
2058
2059   // Expand the current designator into the set of replacement
2060   // designators, so we have a full subobject path down to where the
2061   // member of the anonymous struct/union is actually stored.
2062   DIE->ExpandDesignator(SemaRef.Context, DesigIdx, &Replacements[0],
2063                         &Replacements[0] + Replacements.size());
2064 }
2065
2066 static DesignatedInitExpr *CloneDesignatedInitExpr(Sema &SemaRef,
2067                                                    DesignatedInitExpr *DIE) {
2068   unsigned NumIndexExprs = DIE->getNumSubExprs() - 1;
2069   SmallVector<Expr*, 4> IndexExprs(NumIndexExprs);
2070   for (unsigned I = 0; I < NumIndexExprs; ++I)
2071     IndexExprs[I] = DIE->getSubExpr(I + 1);
2072   return DesignatedInitExpr::Create(SemaRef.Context, DIE->designators(),
2073                                     IndexExprs,
2074                                     DIE->getEqualOrColonLoc(),
2075                                     DIE->usesGNUSyntax(), DIE->getInit());
2076 }
2077
2078 namespace {
2079
2080 // Callback to only accept typo corrections that are for field members of
2081 // the given struct or union.
2082 class FieldInitializerValidatorCCC : public CorrectionCandidateCallback {
2083  public:
2084   explicit FieldInitializerValidatorCCC(RecordDecl *RD)
2085       : Record(RD) {}
2086
2087   bool ValidateCandidate(const TypoCorrection &candidate) override {
2088     FieldDecl *FD = candidate.getCorrectionDeclAs<FieldDecl>();
2089     return FD && FD->getDeclContext()->getRedeclContext()->Equals(Record);
2090   }
2091
2092  private:
2093   RecordDecl *Record;
2094 };
2095
2096 } // end anonymous namespace
2097
2098 /// Check the well-formedness of a C99 designated initializer.
2099 ///
2100 /// Determines whether the designated initializer @p DIE, which
2101 /// resides at the given @p Index within the initializer list @p
2102 /// IList, is well-formed for a current object of type @p DeclType
2103 /// (C99 6.7.8). The actual subobject that this designator refers to
2104 /// within the current subobject is returned in either
2105 /// @p NextField or @p NextElementIndex (whichever is appropriate).
2106 ///
2107 /// @param IList  The initializer list in which this designated
2108 /// initializer occurs.
2109 ///
2110 /// @param DIE The designated initializer expression.
2111 ///
2112 /// @param DesigIdx  The index of the current designator.
2113 ///
2114 /// @param CurrentObjectType The type of the "current object" (C99 6.7.8p17),
2115 /// into which the designation in @p DIE should refer.
2116 ///
2117 /// @param NextField  If non-NULL and the first designator in @p DIE is
2118 /// a field, this will be set to the field declaration corresponding
2119 /// to the field named by the designator.
2120 ///
2121 /// @param NextElementIndex  If non-NULL and the first designator in @p
2122 /// DIE is an array designator or GNU array-range designator, this
2123 /// will be set to the last index initialized by this designator.
2124 ///
2125 /// @param Index  Index into @p IList where the designated initializer
2126 /// @p DIE occurs.
2127 ///
2128 /// @param StructuredList  The initializer list expression that
2129 /// describes all of the subobject initializers in the order they'll
2130 /// actually be initialized.
2131 ///
2132 /// @returns true if there was an error, false otherwise.
2133 bool
2134 InitListChecker::CheckDesignatedInitializer(const InitializedEntity &Entity,
2135                                             InitListExpr *IList,
2136                                             DesignatedInitExpr *DIE,
2137                                             unsigned DesigIdx,
2138                                             QualType &CurrentObjectType,
2139                                           RecordDecl::field_iterator *NextField,
2140                                             llvm::APSInt *NextElementIndex,
2141                                             unsigned &Index,
2142                                             InitListExpr *StructuredList,
2143                                             unsigned &StructuredIndex,
2144                                             bool FinishSubobjectInit,
2145                                             bool TopLevelObject) {
2146   if (DesigIdx == DIE->size()) {
2147     // Check the actual initialization for the designated object type.
2148     bool prevHadError = hadError;
2149
2150     // Temporarily remove the designator expression from the
2151     // initializer list that the child calls see, so that we don't try
2152     // to re-process the designator.
2153     unsigned OldIndex = Index;
2154     IList->setInit(OldIndex, DIE->getInit());
2155
2156     CheckSubElementType(Entity, IList, CurrentObjectType, Index,
2157                         StructuredList, StructuredIndex);
2158
2159     // Restore the designated initializer expression in the syntactic
2160     // form of the initializer list.
2161     if (IList->getInit(OldIndex) != DIE->getInit())
2162       DIE->setInit(IList->getInit(OldIndex));
2163     IList->setInit(OldIndex, DIE);
2164
2165     return hadError && !prevHadError;
2166   }
2167
2168   DesignatedInitExpr::Designator *D = DIE->getDesignator(DesigIdx);
2169   bool IsFirstDesignator = (DesigIdx == 0);
2170   if (!VerifyOnly) {
2171     assert((IsFirstDesignator || StructuredList) &&
2172            "Need a non-designated initializer list to start from");
2173
2174     // Determine the structural initializer list that corresponds to the
2175     // current subobject.
2176     if (IsFirstDesignator)
2177       StructuredList = SyntacticToSemantic.lookup(IList);
2178     else {
2179       Expr *ExistingInit = StructuredIndex < StructuredList->getNumInits() ?
2180           StructuredList->getInit(StructuredIndex) : nullptr;
2181       if (!ExistingInit && StructuredList->hasArrayFiller())
2182         ExistingInit = StructuredList->getArrayFiller();
2183
2184       if (!ExistingInit)
2185         StructuredList =
2186           getStructuredSubobjectInit(IList, Index, CurrentObjectType,
2187                                      StructuredList, StructuredIndex,
2188                                      SourceRange(D->getLocStart(),
2189                                                  DIE->getLocEnd()));
2190       else if (InitListExpr *Result = dyn_cast<InitListExpr>(ExistingInit))
2191         StructuredList = Result;
2192       else {
2193         if (DesignatedInitUpdateExpr *E =
2194                 dyn_cast<DesignatedInitUpdateExpr>(ExistingInit))
2195           StructuredList = E->getUpdater();
2196         else {
2197           DesignatedInitUpdateExpr *DIUE =
2198               new (SemaRef.Context) DesignatedInitUpdateExpr(SemaRef.Context,
2199                                         D->getLocStart(), ExistingInit,
2200                                         DIE->getLocEnd());
2201           StructuredList->updateInit(SemaRef.Context, StructuredIndex, DIUE);
2202           StructuredList = DIUE->getUpdater();
2203         }
2204
2205         // We need to check on source range validity because the previous
2206         // initializer does not have to be an explicit initializer. e.g.,
2207         //
2208         // struct P { int a, b; };
2209         // struct PP { struct P p } l = { { .a = 2 }, .p.b = 3 };
2210         //
2211         // There is an overwrite taking place because the first braced initializer
2212         // list "{ .a = 2 }" already provides value for .p.b (which is zero).
2213         if (ExistingInit->getSourceRange().isValid()) {
2214           // We are creating an initializer list that initializes the
2215           // subobjects of the current object, but there was already an
2216           // initialization that completely initialized the current
2217           // subobject, e.g., by a compound literal:
2218           //
2219           // struct X { int a, b; };
2220           // struct X xs[] = { [0] = (struct X) { 1, 2 }, [0].b = 3 };
2221           //
2222           // Here, xs[0].a == 0 and xs[0].b == 3, since the second,
2223           // designated initializer re-initializes the whole
2224           // subobject [0], overwriting previous initializers.
2225           SemaRef.Diag(D->getLocStart(),
2226                        diag::warn_subobject_initializer_overrides)
2227             << SourceRange(D->getLocStart(), DIE->getLocEnd());
2228
2229           SemaRef.Diag(ExistingInit->getLocStart(),
2230                        diag::note_previous_initializer)
2231             << /*FIXME:has side effects=*/0
2232             << ExistingInit->getSourceRange();
2233         }
2234       }
2235     }
2236     assert(StructuredList && "Expected a structured initializer list");
2237   }
2238
2239   if (D->isFieldDesignator()) {
2240     // C99 6.7.8p7:
2241     //
2242     //   If a designator has the form
2243     //
2244     //      . identifier
2245     //
2246     //   then the current object (defined below) shall have
2247     //   structure or union type and the identifier shall be the
2248     //   name of a member of that type.
2249     const RecordType *RT = CurrentObjectType->getAs<RecordType>();
2250     if (!RT) {
2251       SourceLocation Loc = D->getDotLoc();
2252       if (Loc.isInvalid())
2253         Loc = D->getFieldLoc();
2254       if (!VerifyOnly)
2255         SemaRef.Diag(Loc, diag::err_field_designator_non_aggr)
2256           << SemaRef.getLangOpts().CPlusPlus << CurrentObjectType;
2257       ++Index;
2258       return true;
2259     }
2260
2261     FieldDecl *KnownField = D->getField();
2262     if (!KnownField) {
2263       IdentifierInfo *FieldName = D->getFieldName();
2264       DeclContext::lookup_result Lookup = RT->getDecl()->lookup(FieldName);
2265       for (NamedDecl *ND : Lookup) {
2266         if (auto *FD = dyn_cast<FieldDecl>(ND)) {
2267           KnownField = FD;
2268           break;
2269         }
2270         if (auto *IFD = dyn_cast<IndirectFieldDecl>(ND)) {
2271           // In verify mode, don't modify the original.
2272           if (VerifyOnly)
2273             DIE = CloneDesignatedInitExpr(SemaRef, DIE);
2274           ExpandAnonymousFieldDesignator(SemaRef, DIE, DesigIdx, IFD);
2275           D = DIE->getDesignator(DesigIdx);
2276           KnownField = cast<FieldDecl>(*IFD->chain_begin());
2277           break;
2278         }
2279       }
2280       if (!KnownField) {
2281         if (VerifyOnly) {
2282           ++Index;
2283           return true;  // No typo correction when just trying this out.
2284         }
2285
2286         // Name lookup found something, but it wasn't a field.
2287         if (!Lookup.empty()) {
2288           SemaRef.Diag(D->getFieldLoc(), diag::err_field_designator_nonfield)
2289             << FieldName;
2290           SemaRef.Diag(Lookup.front()->getLocation(),
2291                        diag::note_field_designator_found);
2292           ++Index;
2293           return true;
2294         }
2295
2296         // Name lookup didn't find anything.
2297         // Determine whether this was a typo for another field name.
2298         if (TypoCorrection Corrected = SemaRef.CorrectTypo(
2299                 DeclarationNameInfo(FieldName, D->getFieldLoc()),
2300                 Sema::LookupMemberName, /*Scope=*/nullptr, /*SS=*/nullptr,
2301                 llvm::make_unique<FieldInitializerValidatorCCC>(RT->getDecl()),
2302                 Sema::CTK_ErrorRecovery, RT->getDecl())) {
2303           SemaRef.diagnoseTypo(
2304               Corrected,
2305               SemaRef.PDiag(diag::err_field_designator_unknown_suggest)
2306                 << FieldName << CurrentObjectType);
2307           KnownField = Corrected.getCorrectionDeclAs<FieldDecl>();
2308           hadError = true;
2309         } else {
2310           // Typo correction didn't find anything.
2311           SemaRef.Diag(D->getFieldLoc(), diag::err_field_designator_unknown)
2312             << FieldName << CurrentObjectType;
2313           ++Index;
2314           return true;
2315         }
2316       }
2317     }
2318
2319     unsigned FieldIndex = 0;
2320
2321     if (auto *CXXRD = dyn_cast<CXXRecordDecl>(RT->getDecl()))
2322       FieldIndex = CXXRD->getNumBases();
2323
2324     for (auto *FI : RT->getDecl()->fields()) {
2325       if (FI->isUnnamedBitfield())
2326         continue;
2327       if (declaresSameEntity(KnownField, FI)) {
2328         KnownField = FI;
2329         break;
2330       }
2331       ++FieldIndex;
2332     }
2333
2334     RecordDecl::field_iterator Field =
2335         RecordDecl::field_iterator(DeclContext::decl_iterator(KnownField));
2336
2337     // All of the fields of a union are located at the same place in
2338     // the initializer list.
2339     if (RT->getDecl()->isUnion()) {
2340       FieldIndex = 0;
2341       if (!VerifyOnly) {
2342         FieldDecl *CurrentField = StructuredList->getInitializedFieldInUnion();
2343         if (CurrentField && !declaresSameEntity(CurrentField, *Field)) {
2344           assert(StructuredList->getNumInits() == 1
2345                  && "A union should never have more than one initializer!");
2346
2347           Expr *ExistingInit = StructuredList->getInit(0);
2348           if (ExistingInit) {
2349             // We're about to throw away an initializer, emit warning.
2350             SemaRef.Diag(D->getFieldLoc(),
2351                          diag::warn_initializer_overrides)
2352               << D->getSourceRange();
2353             SemaRef.Diag(ExistingInit->getLocStart(),
2354                          diag::note_previous_initializer)
2355               << /*FIXME:has side effects=*/0
2356               << ExistingInit->getSourceRange();
2357           }
2358
2359           // remove existing initializer
2360           StructuredList->resizeInits(SemaRef.Context, 0);
2361           StructuredList->setInitializedFieldInUnion(nullptr);
2362         }
2363
2364         StructuredList->setInitializedFieldInUnion(*Field);
2365       }
2366     }
2367
2368     // Make sure we can use this declaration.
2369     bool InvalidUse;
2370     if (VerifyOnly)
2371       InvalidUse = !SemaRef.CanUseDecl(*Field, TreatUnavailableAsInvalid);
2372     else
2373       InvalidUse = SemaRef.DiagnoseUseOfDecl(*Field, D->getFieldLoc());
2374     if (InvalidUse) {
2375       ++Index;
2376       return true;
2377     }
2378
2379     if (!VerifyOnly) {
2380       // Update the designator with the field declaration.
2381       D->setField(*Field);
2382
2383       // Make sure that our non-designated initializer list has space
2384       // for a subobject corresponding to this field.
2385       if (FieldIndex >= StructuredList->getNumInits())
2386         StructuredList->resizeInits(SemaRef.Context, FieldIndex + 1);
2387     }
2388
2389     // This designator names a flexible array member.
2390     if (Field->getType()->isIncompleteArrayType()) {
2391       bool Invalid = false;
2392       if ((DesigIdx + 1) != DIE->size()) {
2393         // We can't designate an object within the flexible array
2394         // member (because GCC doesn't allow it).
2395         if (!VerifyOnly) {
2396           DesignatedInitExpr::Designator *NextD
2397             = DIE->getDesignator(DesigIdx + 1);
2398           SemaRef.Diag(NextD->getLocStart(),
2399                         diag::err_designator_into_flexible_array_member)
2400             << SourceRange(NextD->getLocStart(),
2401                            DIE->getLocEnd());
2402           SemaRef.Diag(Field->getLocation(), diag::note_flexible_array_member)
2403             << *Field;
2404         }
2405         Invalid = true;
2406       }
2407
2408       if (!hadError && !isa<InitListExpr>(DIE->getInit()) &&
2409           !isa<StringLiteral>(DIE->getInit())) {
2410         // The initializer is not an initializer list.
2411         if (!VerifyOnly) {
2412           SemaRef.Diag(DIE->getInit()->getLocStart(),
2413                         diag::err_flexible_array_init_needs_braces)
2414             << DIE->getInit()->getSourceRange();
2415           SemaRef.Diag(Field->getLocation(), diag::note_flexible_array_member)
2416             << *Field;
2417         }
2418         Invalid = true;
2419       }
2420
2421       // Check GNU flexible array initializer.
2422       if (!Invalid && CheckFlexibleArrayInit(Entity, DIE->getInit(), *Field,
2423                                              TopLevelObject))
2424         Invalid = true;
2425
2426       if (Invalid) {
2427         ++Index;
2428         return true;
2429       }
2430
2431       // Initialize the array.
2432       bool prevHadError = hadError;
2433       unsigned newStructuredIndex = FieldIndex;
2434       unsigned OldIndex = Index;
2435       IList->setInit(Index, DIE->getInit());
2436
2437       InitializedEntity MemberEntity =
2438         InitializedEntity::InitializeMember(*Field, &Entity);
2439       CheckSubElementType(MemberEntity, IList, Field->getType(), Index,
2440                           StructuredList, newStructuredIndex);
2441
2442       IList->setInit(OldIndex, DIE);
2443       if (hadError && !prevHadError) {
2444         ++Field;
2445         ++FieldIndex;
2446         if (NextField)
2447           *NextField = Field;
2448         StructuredIndex = FieldIndex;
2449         return true;
2450       }
2451     } else {
2452       // Recurse to check later designated subobjects.
2453       QualType FieldType = Field->getType();
2454       unsigned newStructuredIndex = FieldIndex;
2455
2456       InitializedEntity MemberEntity =
2457         InitializedEntity::InitializeMember(*Field, &Entity);
2458       if (CheckDesignatedInitializer(MemberEntity, IList, DIE, DesigIdx + 1,
2459                                      FieldType, nullptr, nullptr, Index,
2460                                      StructuredList, newStructuredIndex,
2461                                      FinishSubobjectInit, false))
2462         return true;
2463     }
2464
2465     // Find the position of the next field to be initialized in this
2466     // subobject.
2467     ++Field;
2468     ++FieldIndex;
2469
2470     // If this the first designator, our caller will continue checking
2471     // the rest of this struct/class/union subobject.
2472     if (IsFirstDesignator) {
2473       if (NextField)
2474         *NextField = Field;
2475       StructuredIndex = FieldIndex;
2476       return false;
2477     }
2478
2479     if (!FinishSubobjectInit)
2480       return false;
2481
2482     // We've already initialized something in the union; we're done.
2483     if (RT->getDecl()->isUnion())
2484       return hadError;
2485
2486     // Check the remaining fields within this class/struct/union subobject.
2487     bool prevHadError = hadError;
2488
2489     auto NoBases =
2490         CXXRecordDecl::base_class_range(CXXRecordDecl::base_class_iterator(),
2491                                         CXXRecordDecl::base_class_iterator());
2492     CheckStructUnionTypes(Entity, IList, CurrentObjectType, NoBases, Field,
2493                           false, Index, StructuredList, FieldIndex);
2494     return hadError && !prevHadError;
2495   }
2496
2497   // C99 6.7.8p6:
2498   //
2499   //   If a designator has the form
2500   //
2501   //      [ constant-expression ]
2502   //
2503   //   then the current object (defined below) shall have array
2504   //   type and the expression shall be an integer constant
2505   //   expression. If the array is of unknown size, any
2506   //   nonnegative value is valid.
2507   //
2508   // Additionally, cope with the GNU extension that permits
2509   // designators of the form
2510   //
2511   //      [ constant-expression ... constant-expression ]
2512   const ArrayType *AT = SemaRef.Context.getAsArrayType(CurrentObjectType);
2513   if (!AT) {
2514     if (!VerifyOnly)
2515       SemaRef.Diag(D->getLBracketLoc(), diag::err_array_designator_non_array)
2516         << CurrentObjectType;
2517     ++Index;
2518     return true;
2519   }
2520
2521   Expr *IndexExpr = nullptr;
2522   llvm::APSInt DesignatedStartIndex, DesignatedEndIndex;
2523   if (D->isArrayDesignator()) {
2524     IndexExpr = DIE->getArrayIndex(*D);
2525     DesignatedStartIndex = IndexExpr->EvaluateKnownConstInt(SemaRef.Context);
2526     DesignatedEndIndex = DesignatedStartIndex;
2527   } else {
2528     assert(D->isArrayRangeDesignator() && "Need array-range designator");
2529
2530     DesignatedStartIndex =
2531       DIE->getArrayRangeStart(*D)->EvaluateKnownConstInt(SemaRef.Context);
2532     DesignatedEndIndex =
2533       DIE->getArrayRangeEnd(*D)->EvaluateKnownConstInt(SemaRef.Context);
2534     IndexExpr = DIE->getArrayRangeEnd(*D);
2535
2536     // Codegen can't handle evaluating array range designators that have side
2537     // effects, because we replicate the AST value for each initialized element.
2538     // As such, set the sawArrayRangeDesignator() bit if we initialize multiple
2539     // elements with something that has a side effect, so codegen can emit an
2540     // "error unsupported" error instead of miscompiling the app.
2541     if (DesignatedStartIndex.getZExtValue()!=DesignatedEndIndex.getZExtValue()&&
2542         DIE->getInit()->HasSideEffects(SemaRef.Context) && !VerifyOnly)
2543       FullyStructuredList->sawArrayRangeDesignator();
2544   }
2545
2546   if (isa<ConstantArrayType>(AT)) {
2547     llvm::APSInt MaxElements(cast<ConstantArrayType>(AT)->getSize(), false);
2548     DesignatedStartIndex
2549       = DesignatedStartIndex.extOrTrunc(MaxElements.getBitWidth());
2550     DesignatedStartIndex.setIsUnsigned(MaxElements.isUnsigned());
2551     DesignatedEndIndex
2552       = DesignatedEndIndex.extOrTrunc(MaxElements.getBitWidth());
2553     DesignatedEndIndex.setIsUnsigned(MaxElements.isUnsigned());
2554     if (DesignatedEndIndex >= MaxElements) {
2555       if (!VerifyOnly)
2556         SemaRef.Diag(IndexExpr->getLocStart(),
2557                       diag::err_array_designator_too_large)
2558           << DesignatedEndIndex.toString(10) << MaxElements.toString(10)
2559           << IndexExpr->getSourceRange();
2560       ++Index;
2561       return true;
2562     }
2563   } else {
2564     unsigned DesignatedIndexBitWidth =
2565       ConstantArrayType::getMaxSizeBits(SemaRef.Context);
2566     DesignatedStartIndex =
2567       DesignatedStartIndex.extOrTrunc(DesignatedIndexBitWidth);
2568     DesignatedEndIndex =
2569       DesignatedEndIndex.extOrTrunc(DesignatedIndexBitWidth);
2570     DesignatedStartIndex.setIsUnsigned(true);
2571     DesignatedEndIndex.setIsUnsigned(true);
2572   }
2573
2574   if (!VerifyOnly && StructuredList->isStringLiteralInit()) {
2575     // We're modifying a string literal init; we have to decompose the string
2576     // so we can modify the individual characters.
2577     ASTContext &Context = SemaRef.Context;
2578     Expr *SubExpr = StructuredList->getInit(0)->IgnoreParens();
2579
2580     // Compute the character type
2581     QualType CharTy = AT->getElementType();
2582
2583     // Compute the type of the integer literals.
2584     QualType PromotedCharTy = CharTy;
2585     if (CharTy->isPromotableIntegerType())
2586       PromotedCharTy = Context.getPromotedIntegerType(CharTy);
2587     unsigned PromotedCharTyWidth = Context.getTypeSize(PromotedCharTy);
2588
2589     if (StringLiteral *SL = dyn_cast<StringLiteral>(SubExpr)) {
2590       // Get the length of the string.
2591       uint64_t StrLen = SL->getLength();
2592       if (cast<ConstantArrayType>(AT)->getSize().ult(StrLen))
2593         StrLen = cast<ConstantArrayType>(AT)->getSize().getZExtValue();
2594       StructuredList->resizeInits(Context, StrLen);
2595
2596       // Build a literal for each character in the string, and put them into
2597       // the init list.
2598       for (unsigned i = 0, e = StrLen; i != e; ++i) {
2599         llvm::APInt CodeUnit(PromotedCharTyWidth, SL->getCodeUnit(i));
2600         Expr *Init = new (Context) IntegerLiteral(
2601             Context, CodeUnit, PromotedCharTy, SubExpr->getExprLoc());
2602         if (CharTy != PromotedCharTy)
2603           Init = ImplicitCastExpr::Create(Context, CharTy, CK_IntegralCast,
2604                                           Init, nullptr, VK_RValue);
2605         StructuredList->updateInit(Context, i, Init);
2606       }
2607     } else {
2608       ObjCEncodeExpr *E = cast<ObjCEncodeExpr>(SubExpr);
2609       std::string Str;
2610       Context.getObjCEncodingForType(E->getEncodedType(), Str);
2611
2612       // Get the length of the string.
2613       uint64_t StrLen = Str.size();
2614       if (cast<ConstantArrayType>(AT)->getSize().ult(StrLen))
2615         StrLen = cast<ConstantArrayType>(AT)->getSize().getZExtValue();
2616       StructuredList->resizeInits(Context, StrLen);
2617
2618       // Build a literal for each character in the string, and put them into
2619       // the init list.
2620       for (unsigned i = 0, e = StrLen; i != e; ++i) {
2621         llvm::APInt CodeUnit(PromotedCharTyWidth, Str[i]);
2622         Expr *Init = new (Context) IntegerLiteral(
2623             Context, CodeUnit, PromotedCharTy, SubExpr->getExprLoc());
2624         if (CharTy != PromotedCharTy)
2625           Init = ImplicitCastExpr::Create(Context, CharTy, CK_IntegralCast,
2626                                           Init, nullptr, VK_RValue);
2627         StructuredList->updateInit(Context, i, Init);
2628       }
2629     }
2630   }
2631
2632   // Make sure that our non-designated initializer list has space
2633   // for a subobject corresponding to this array element.
2634   if (!VerifyOnly &&
2635       DesignatedEndIndex.getZExtValue() >= StructuredList->getNumInits())
2636     StructuredList->resizeInits(SemaRef.Context,
2637                                 DesignatedEndIndex.getZExtValue() + 1);
2638
2639   // Repeatedly perform subobject initializations in the range
2640   // [DesignatedStartIndex, DesignatedEndIndex].
2641
2642   // Move to the next designator
2643   unsigned ElementIndex = DesignatedStartIndex.getZExtValue();
2644   unsigned OldIndex = Index;
2645
2646   InitializedEntity ElementEntity =
2647     InitializedEntity::InitializeElement(SemaRef.Context, 0, Entity);
2648
2649   while (DesignatedStartIndex <= DesignatedEndIndex) {
2650     // Recurse to check later designated subobjects.
2651     QualType ElementType = AT->getElementType();
2652     Index = OldIndex;
2653
2654     ElementEntity.setElementIndex(ElementIndex);
2655     if (CheckDesignatedInitializer(
2656             ElementEntity, IList, DIE, DesigIdx + 1, ElementType, nullptr,
2657             nullptr, Index, StructuredList, ElementIndex,
2658             FinishSubobjectInit && (DesignatedStartIndex == DesignatedEndIndex),
2659             false))
2660       return true;
2661
2662     // Move to the next index in the array that we'll be initializing.
2663     ++DesignatedStartIndex;
2664     ElementIndex = DesignatedStartIndex.getZExtValue();
2665   }
2666
2667   // If this the first designator, our caller will continue checking
2668   // the rest of this array subobject.
2669   if (IsFirstDesignator) {
2670     if (NextElementIndex)
2671       *NextElementIndex = DesignatedStartIndex;
2672     StructuredIndex = ElementIndex;
2673     return false;
2674   }
2675
2676   if (!FinishSubobjectInit)
2677     return false;
2678
2679   // Check the remaining elements within this array subobject.
2680   bool prevHadError = hadError;
2681   CheckArrayType(Entity, IList, CurrentObjectType, DesignatedStartIndex,
2682                  /*SubobjectIsDesignatorContext=*/false, Index,
2683                  StructuredList, ElementIndex);
2684   return hadError && !prevHadError;
2685 }
2686
2687 // Get the structured initializer list for a subobject of type
2688 // @p CurrentObjectType.
2689 InitListExpr *
2690 InitListChecker::getStructuredSubobjectInit(InitListExpr *IList, unsigned Index,
2691                                             QualType CurrentObjectType,
2692                                             InitListExpr *StructuredList,
2693                                             unsigned StructuredIndex,
2694                                             SourceRange InitRange,
2695                                             bool IsFullyOverwritten) {
2696   if (VerifyOnly)
2697     return nullptr; // No structured list in verification-only mode.
2698   Expr *ExistingInit = nullptr;
2699   if (!StructuredList)
2700     ExistingInit = SyntacticToSemantic.lookup(IList);
2701   else if (StructuredIndex < StructuredList->getNumInits())
2702     ExistingInit = StructuredList->getInit(StructuredIndex);
2703
2704   if (InitListExpr *Result = dyn_cast_or_null<InitListExpr>(ExistingInit))
2705     // There might have already been initializers for subobjects of the current
2706     // object, but a subsequent initializer list will overwrite the entirety
2707     // of the current object. (See DR 253 and C99 6.7.8p21). e.g.,
2708     //
2709     // struct P { char x[6]; };
2710     // struct P l = { .x[2] = 'x', .x = { [0] = 'f' } };
2711     //
2712     // The first designated initializer is ignored, and l.x is just "f".
2713     if (!IsFullyOverwritten)
2714       return Result;
2715
2716   if (ExistingInit) {
2717     // We are creating an initializer list that initializes the
2718     // subobjects of the current object, but there was already an
2719     // initialization that completely initialized the current
2720     // subobject, e.g., by a compound literal:
2721     //
2722     // struct X { int a, b; };
2723     // struct X xs[] = { [0] = (struct X) { 1, 2 }, [0].b = 3 };
2724     //
2725     // Here, xs[0].a == 0 and xs[0].b == 3, since the second,
2726     // designated initializer re-initializes the whole
2727     // subobject [0], overwriting previous initializers.
2728     SemaRef.Diag(InitRange.getBegin(),
2729                  diag::warn_subobject_initializer_overrides)
2730       << InitRange;
2731     SemaRef.Diag(ExistingInit->getLocStart(),
2732                   diag::note_previous_initializer)
2733       << /*FIXME:has side effects=*/0
2734       << ExistingInit->getSourceRange();
2735   }
2736
2737   InitListExpr *Result
2738     = new (SemaRef.Context) InitListExpr(SemaRef.Context,
2739                                          InitRange.getBegin(), None,
2740                                          InitRange.getEnd());
2741
2742   QualType ResultType = CurrentObjectType;
2743   if (!ResultType->isArrayType())
2744     ResultType = ResultType.getNonLValueExprType(SemaRef.Context);
2745   Result->setType(ResultType);
2746
2747   // Pre-allocate storage for the structured initializer list.
2748   unsigned NumElements = 0;
2749   unsigned NumInits = 0;
2750   bool GotNumInits = false;
2751   if (!StructuredList) {
2752     NumInits = IList->getNumInits();
2753     GotNumInits = true;
2754   } else if (Index < IList->getNumInits()) {
2755     if (InitListExpr *SubList = dyn_cast<InitListExpr>(IList->getInit(Index))) {
2756       NumInits = SubList->getNumInits();
2757       GotNumInits = true;
2758     }
2759   }
2760
2761   if (const ArrayType *AType
2762       = SemaRef.Context.getAsArrayType(CurrentObjectType)) {
2763     if (const ConstantArrayType *CAType = dyn_cast<ConstantArrayType>(AType)) {
2764       NumElements = CAType->getSize().getZExtValue();
2765       // Simple heuristic so that we don't allocate a very large
2766       // initializer with many empty entries at the end.
2767       if (GotNumInits && NumElements > NumInits)
2768         NumElements = 0;
2769     }
2770   } else if (const VectorType *VType = CurrentObjectType->getAs<VectorType>())
2771     NumElements = VType->getNumElements();
2772   else if (const RecordType *RType = CurrentObjectType->getAs<RecordType>()) {
2773     RecordDecl *RDecl = RType->getDecl();
2774     if (RDecl->isUnion())
2775       NumElements = 1;
2776     else
2777       NumElements = std::distance(RDecl->field_begin(), RDecl->field_end());
2778   }
2779
2780   Result->reserveInits(SemaRef.Context, NumElements);
2781
2782   // Link this new initializer list into the structured initializer
2783   // lists.
2784   if (StructuredList)
2785     StructuredList->updateInit(SemaRef.Context, StructuredIndex, Result);
2786   else {
2787     Result->setSyntacticForm(IList);
2788     SyntacticToSemantic[IList] = Result;
2789   }
2790
2791   return Result;
2792 }
2793
2794 /// Update the initializer at index @p StructuredIndex within the
2795 /// structured initializer list to the value @p expr.
2796 void InitListChecker::UpdateStructuredListElement(InitListExpr *StructuredList,
2797                                                   unsigned &StructuredIndex,
2798                                                   Expr *expr) {
2799   // No structured initializer list to update
2800   if (!StructuredList)
2801     return;
2802
2803   if (Expr *PrevInit = StructuredList->updateInit(SemaRef.Context,
2804                                                   StructuredIndex, expr)) {
2805     // This initializer overwrites a previous initializer. Warn.
2806     // We need to check on source range validity because the previous
2807     // initializer does not have to be an explicit initializer.
2808     // struct P { int a, b; };
2809     // struct PP { struct P p } l = { { .a = 2 }, .p.b = 3 };
2810     // There is an overwrite taking place because the first braced initializer
2811     // list "{ .a = 2 }' already provides value for .p.b (which is zero).
2812     if (PrevInit->getSourceRange().isValid()) {
2813       SemaRef.Diag(expr->getLocStart(),
2814                    diag::warn_initializer_overrides)
2815         << expr->getSourceRange();
2816
2817       SemaRef.Diag(PrevInit->getLocStart(),
2818                    diag::note_previous_initializer)
2819         << /*FIXME:has side effects=*/0
2820         << PrevInit->getSourceRange();
2821     }
2822   }
2823
2824   ++StructuredIndex;
2825 }
2826
2827 /// Check that the given Index expression is a valid array designator
2828 /// value. This is essentially just a wrapper around
2829 /// VerifyIntegerConstantExpression that also checks for negative values
2830 /// and produces a reasonable diagnostic if there is a
2831 /// failure. Returns the index expression, possibly with an implicit cast
2832 /// added, on success.  If everything went okay, Value will receive the
2833 /// value of the constant expression.
2834 static ExprResult
2835 CheckArrayDesignatorExpr(Sema &S, Expr *Index, llvm::APSInt &Value) {
2836   SourceLocation Loc = Index->getLocStart();
2837
2838   // Make sure this is an integer constant expression.
2839   ExprResult Result = S.VerifyIntegerConstantExpression(Index, &Value);
2840   if (Result.isInvalid())
2841     return Result;
2842
2843   if (Value.isSigned() && Value.isNegative())
2844     return S.Diag(Loc, diag::err_array_designator_negative)
2845       << Value.toString(10) << Index->getSourceRange();
2846
2847   Value.setIsUnsigned(true);
2848   return Result;
2849 }
2850
2851 ExprResult Sema::ActOnDesignatedInitializer(Designation &Desig,
2852                                             SourceLocation Loc,
2853                                             bool GNUSyntax,
2854                                             ExprResult Init) {
2855   typedef DesignatedInitExpr::Designator ASTDesignator;
2856
2857   bool Invalid = false;
2858   SmallVector<ASTDesignator, 32> Designators;
2859   SmallVector<Expr *, 32> InitExpressions;
2860
2861   // Build designators and check array designator expressions.
2862   for (unsigned Idx = 0; Idx < Desig.getNumDesignators(); ++Idx) {
2863     const Designator &D = Desig.getDesignator(Idx);
2864     switch (D.getKind()) {
2865     case Designator::FieldDesignator:
2866       Designators.push_back(ASTDesignator(D.getField(), D.getDotLoc(),
2867                                           D.getFieldLoc()));
2868       break;
2869
2870     case Designator::ArrayDesignator: {
2871       Expr *Index = static_cast<Expr *>(D.getArrayIndex());
2872       llvm::APSInt IndexValue;
2873       if (!Index->isTypeDependent() && !Index->isValueDependent())
2874         Index = CheckArrayDesignatorExpr(*this, Index, IndexValue).get();
2875       if (!Index)
2876         Invalid = true;
2877       else {
2878         Designators.push_back(ASTDesignator(InitExpressions.size(),
2879                                             D.getLBracketLoc(),
2880                                             D.getRBracketLoc()));
2881         InitExpressions.push_back(Index);
2882       }
2883       break;
2884     }
2885
2886     case Designator::ArrayRangeDesignator: {
2887       Expr *StartIndex = static_cast<Expr *>(D.getArrayRangeStart());
2888       Expr *EndIndex = static_cast<Expr *>(D.getArrayRangeEnd());
2889       llvm::APSInt StartValue;
2890       llvm::APSInt EndValue;
2891       bool StartDependent = StartIndex->isTypeDependent() ||
2892                             StartIndex->isValueDependent();
2893       bool EndDependent = EndIndex->isTypeDependent() ||
2894                           EndIndex->isValueDependent();
2895       if (!StartDependent)
2896         StartIndex =
2897             CheckArrayDesignatorExpr(*this, StartIndex, StartValue).get();
2898       if (!EndDependent)
2899         EndIndex = CheckArrayDesignatorExpr(*this, EndIndex, EndValue).get();
2900
2901       if (!StartIndex || !EndIndex)
2902         Invalid = true;
2903       else {
2904         // Make sure we're comparing values with the same bit width.
2905         if (StartDependent || EndDependent) {
2906           // Nothing to compute.
2907         } else if (StartValue.getBitWidth() > EndValue.getBitWidth())
2908           EndValue = EndValue.extend(StartValue.getBitWidth());
2909         else if (StartValue.getBitWidth() < EndValue.getBitWidth())
2910           StartValue = StartValue.extend(EndValue.getBitWidth());
2911
2912         if (!StartDependent && !EndDependent && EndValue < StartValue) {
2913           Diag(D.getEllipsisLoc(), diag::err_array_designator_empty_range)
2914             << StartValue.toString(10) << EndValue.toString(10)
2915             << StartIndex->getSourceRange() << EndIndex->getSourceRange();
2916           Invalid = true;
2917         } else {
2918           Designators.push_back(ASTDesignator(InitExpressions.size(),
2919                                               D.getLBracketLoc(),
2920                                               D.getEllipsisLoc(),
2921                                               D.getRBracketLoc()));
2922           InitExpressions.push_back(StartIndex);
2923           InitExpressions.push_back(EndIndex);
2924         }
2925       }
2926       break;
2927     }
2928     }
2929   }
2930
2931   if (Invalid || Init.isInvalid())
2932     return ExprError();
2933
2934   // Clear out the expressions within the designation.
2935   Desig.ClearExprs(*this);
2936
2937   DesignatedInitExpr *DIE
2938     = DesignatedInitExpr::Create(Context,
2939                                  Designators,
2940                                  InitExpressions, Loc, GNUSyntax,
2941                                  Init.getAs<Expr>());
2942
2943   if (!getLangOpts().C99)
2944     Diag(DIE->getLocStart(), diag::ext_designated_init)
2945       << DIE->getSourceRange();
2946
2947   return DIE;
2948 }
2949
2950 //===----------------------------------------------------------------------===//
2951 // Initialization entity
2952 //===----------------------------------------------------------------------===//
2953
2954 InitializedEntity::InitializedEntity(ASTContext &Context, unsigned Index,
2955                                      const InitializedEntity &Parent)
2956   : Parent(&Parent), Index(Index)
2957 {
2958   if (const ArrayType *AT = Context.getAsArrayType(Parent.getType())) {
2959     Kind = EK_ArrayElement;
2960     Type = AT->getElementType();
2961   } else if (const VectorType *VT = Parent.getType()->getAs<VectorType>()) {
2962     Kind = EK_VectorElement;
2963     Type = VT->getElementType();
2964   } else {
2965     const ComplexType *CT = Parent.getType()->getAs<ComplexType>();
2966     assert(CT && "Unexpected type");
2967     Kind = EK_ComplexElement;
2968     Type = CT->getElementType();
2969   }
2970 }
2971
2972 InitializedEntity
2973 InitializedEntity::InitializeBase(ASTContext &Context,
2974                                   const CXXBaseSpecifier *Base,
2975                                   bool IsInheritedVirtualBase,
2976                                   const InitializedEntity *Parent) {
2977   InitializedEntity Result;
2978   Result.Kind = EK_Base;
2979   Result.Parent = Parent;
2980   Result.Base = reinterpret_cast<uintptr_t>(Base);
2981   if (IsInheritedVirtualBase)
2982     Result.Base |= 0x01;
2983
2984   Result.Type = Base->getType();
2985   return Result;
2986 }
2987
2988 DeclarationName InitializedEntity::getName() const {
2989   switch (getKind()) {
2990   case EK_Parameter:
2991   case EK_Parameter_CF_Audited: {
2992     ParmVarDecl *D = reinterpret_cast<ParmVarDecl*>(Parameter & ~0x1);
2993     return (D ? D->getDeclName() : DeclarationName());
2994   }
2995
2996   case EK_Variable:
2997   case EK_Member:
2998   case EK_Binding:
2999     return Variable.VariableOrMember->getDeclName();
3000
3001   case EK_LambdaCapture:
3002     return DeclarationName(Capture.VarID);
3003
3004   case EK_Result:
3005   case EK_StmtExprResult:
3006   case EK_Exception:
3007   case EK_New:
3008   case EK_Temporary:
3009   case EK_Base:
3010   case EK_Delegating:
3011   case EK_ArrayElement:
3012   case EK_VectorElement:
3013   case EK_ComplexElement:
3014   case EK_BlockElement:
3015   case EK_LambdaToBlockConversionBlockElement:
3016   case EK_CompoundLiteralInit:
3017   case EK_RelatedResult:
3018     return DeclarationName();
3019   }
3020
3021   llvm_unreachable("Invalid EntityKind!");
3022 }
3023
3024 ValueDecl *InitializedEntity::getDecl() const {
3025   switch (getKind()) {
3026   case EK_Variable:
3027   case EK_Member:
3028   case EK_Binding:
3029     return Variable.VariableOrMember;
3030
3031   case EK_Parameter:
3032   case EK_Parameter_CF_Audited:
3033     return reinterpret_cast<ParmVarDecl*>(Parameter & ~0x1);
3034
3035   case EK_Result:
3036   case EK_StmtExprResult:
3037   case EK_Exception:
3038   case EK_New:
3039   case EK_Temporary:
3040   case EK_Base:
3041   case EK_Delegating:
3042   case EK_ArrayElement:
3043   case EK_VectorElement:
3044   case EK_ComplexElement:
3045   case EK_BlockElement:
3046   case EK_LambdaToBlockConversionBlockElement:
3047   case EK_LambdaCapture:
3048   case EK_CompoundLiteralInit:
3049   case EK_RelatedResult:
3050     return nullptr;
3051   }
3052
3053   llvm_unreachable("Invalid EntityKind!");
3054 }
3055
3056 bool InitializedEntity::allowsNRVO() const {
3057   switch (getKind()) {
3058   case EK_Result:
3059   case EK_Exception:
3060     return LocAndNRVO.NRVO;
3061
3062   case EK_StmtExprResult:
3063   case EK_Variable:
3064   case EK_Parameter:
3065   case EK_Parameter_CF_Audited:
3066   case EK_Member:
3067   case EK_Binding:
3068   case EK_New:
3069   case EK_Temporary:
3070   case EK_CompoundLiteralInit:
3071   case EK_Base:
3072   case EK_Delegating:
3073   case EK_ArrayElement:
3074   case EK_VectorElement:
3075   case EK_ComplexElement:
3076   case EK_BlockElement:
3077   case EK_LambdaToBlockConversionBlockElement:
3078   case EK_LambdaCapture:
3079   case EK_RelatedResult:
3080     break;
3081   }
3082
3083   return false;
3084 }
3085
3086 unsigned InitializedEntity::dumpImpl(raw_ostream &OS) const {
3087   assert(getParent() != this);
3088   unsigned Depth = getParent() ? getParent()->dumpImpl(OS) : 0;
3089   for (unsigned I = 0; I != Depth; ++I)
3090     OS << "`-";
3091
3092   switch (getKind()) {
3093   case EK_Variable: OS << "Variable"; break;
3094   case EK_Parameter: OS << "Parameter"; break;
3095   case EK_Parameter_CF_Audited: OS << "CF audited function Parameter";
3096     break;
3097   case EK_Result: OS << "Result"; break;
3098   case EK_StmtExprResult: OS << "StmtExprResult"; break;
3099   case EK_Exception: OS << "Exception"; break;
3100   case EK_Member: OS << "Member"; break;
3101   case EK_Binding: OS << "Binding"; break;
3102   case EK_New: OS << "New"; break;
3103   case EK_Temporary: OS << "Temporary"; break;
3104   case EK_CompoundLiteralInit: OS << "CompoundLiteral";break;
3105   case EK_RelatedResult: OS << "RelatedResult"; break;
3106   case EK_Base: OS << "Base"; break;
3107   case EK_Delegating: OS << "Delegating"; break;
3108   case EK_ArrayElement: OS << "ArrayElement " << Index; break;
3109   case EK_VectorElement: OS << "VectorElement " << Index; break;
3110   case EK_ComplexElement: OS << "ComplexElement " << Index; break;
3111   case EK_BlockElement: OS << "Block"; break;
3112   case EK_LambdaToBlockConversionBlockElement:
3113     OS << "Block (lambda)";
3114     break;
3115   case EK_LambdaCapture:
3116     OS << "LambdaCapture ";
3117     OS << DeclarationName(Capture.VarID);
3118     break;
3119   }
3120
3121   if (auto *D = getDecl()) {
3122     OS << " ";
3123     D->printQualifiedName(OS);
3124   }
3125
3126   OS << " '" << getType().getAsString() << "'\n";
3127
3128   return Depth + 1;
3129 }
3130
3131 LLVM_DUMP_METHOD void InitializedEntity::dump() const {
3132   dumpImpl(llvm::errs());
3133 }
3134
3135 //===----------------------------------------------------------------------===//
3136 // Initialization sequence
3137 //===----------------------------------------------------------------------===//
3138
3139 void InitializationSequence::Step::Destroy() {
3140   switch (Kind) {
3141   case SK_ResolveAddressOfOverloadedFunction:
3142   case SK_CastDerivedToBaseRValue:
3143   case SK_CastDerivedToBaseXValue:
3144   case SK_CastDerivedToBaseLValue:
3145   case SK_BindReference:
3146   case SK_BindReferenceToTemporary:
3147   case SK_FinalCopy:
3148   case SK_ExtraneousCopyToTemporary:
3149   case SK_UserConversion:
3150   case SK_QualificationConversionRValue:
3151   case SK_QualificationConversionXValue:
3152   case SK_QualificationConversionLValue:
3153   case SK_AtomicConversion:
3154   case SK_LValueToRValue:
3155   case SK_ListInitialization:
3156   case SK_UnwrapInitList:
3157   case SK_RewrapInitList:
3158   case SK_ConstructorInitialization:
3159   case SK_ConstructorInitializationFromList:
3160   case SK_ZeroInitialization:
3161   case SK_CAssignment:
3162   case SK_StringInit:
3163   case SK_ObjCObjectConversion:
3164   case SK_ArrayLoopIndex:
3165   case SK_ArrayLoopInit:
3166   case SK_ArrayInit:
3167   case SK_GNUArrayInit:
3168   case SK_ParenthesizedArrayInit:
3169   case SK_PassByIndirectCopyRestore:
3170   case SK_PassByIndirectRestore:
3171   case SK_ProduceObjCObject:
3172   case SK_StdInitializerList:
3173   case SK_StdInitializerListConstructorCall:
3174   case SK_OCLSamplerInit:
3175   case SK_OCLZeroEvent:
3176   case SK_OCLZeroQueue:
3177     break;
3178
3179   case SK_ConversionSequence:
3180   case SK_ConversionSequenceNoNarrowing:
3181     delete ICS;
3182   }
3183 }
3184
3185 bool InitializationSequence::isDirectReferenceBinding() const {
3186   // There can be some lvalue adjustments after the SK_BindReference step.
3187   for (auto I = Steps.rbegin(); I != Steps.rend(); ++I) {
3188     if (I->Kind == SK_BindReference)
3189       return true;
3190     if (I->Kind == SK_BindReferenceToTemporary)
3191       return false;
3192   }
3193   return false;
3194 }
3195
3196 bool InitializationSequence::isAmbiguous() const {
3197   if (!Failed())
3198     return false;
3199
3200   switch (getFailureKind()) {
3201   case FK_TooManyInitsForReference:
3202   case FK_ParenthesizedListInitForReference:
3203   case FK_ArrayNeedsInitList:
3204   case FK_ArrayNeedsInitListOrStringLiteral:
3205   case FK_ArrayNeedsInitListOrWideStringLiteral:
3206   case FK_NarrowStringIntoWideCharArray:
3207   case FK_WideStringIntoCharArray:
3208   case FK_IncompatWideStringIntoWideChar:
3209   case FK_PlainStringIntoUTF8Char:
3210   case FK_UTF8StringIntoPlainChar:
3211   case FK_AddressOfOverloadFailed: // FIXME: Could do better
3212   case FK_NonConstLValueReferenceBindingToTemporary:
3213   case FK_NonConstLValueReferenceBindingToBitfield:
3214   case FK_NonConstLValueReferenceBindingToVectorElement:
3215   case FK_NonConstLValueReferenceBindingToUnrelated:
3216   case FK_RValueReferenceBindingToLValue:
3217   case FK_ReferenceInitDropsQualifiers:
3218   case FK_ReferenceInitFailed:
3219   case FK_ConversionFailed:
3220   case FK_ConversionFromPropertyFailed:
3221   case FK_TooManyInitsForScalar:
3222   case FK_ParenthesizedListInitForScalar:
3223   case FK_ReferenceBindingToInitList:
3224   case FK_InitListBadDestinationType:
3225   case FK_DefaultInitOfConst:
3226   case FK_Incomplete:
3227   case FK_ArrayTypeMismatch:
3228   case FK_NonConstantArrayInit:
3229   case FK_ListInitializationFailed:
3230   case FK_VariableLengthArrayHasInitializer:
3231   case FK_PlaceholderType:
3232   case FK_ExplicitConstructor:
3233   case FK_AddressOfUnaddressableFunction:
3234     return false;
3235
3236   case FK_ReferenceInitOverloadFailed:
3237   case FK_UserConversionOverloadFailed:
3238   case FK_ConstructorOverloadFailed:
3239   case FK_ListConstructorOverloadFailed:
3240     return FailedOverloadResult == OR_Ambiguous;
3241   }
3242
3243   llvm_unreachable("Invalid EntityKind!");
3244 }
3245
3246 bool InitializationSequence::isConstructorInitialization() const {
3247   return !Steps.empty() && Steps.back().Kind == SK_ConstructorInitialization;
3248 }
3249
3250 void
3251 InitializationSequence
3252 ::AddAddressOverloadResolutionStep(FunctionDecl *Function,
3253                                    DeclAccessPair Found,
3254                                    bool HadMultipleCandidates) {
3255   Step S;
3256   S.Kind = SK_ResolveAddressOfOverloadedFunction;
3257   S.Type = Function->getType();
3258   S.Function.HadMultipleCandidates = HadMultipleCandidates;
3259   S.Function.Function = Function;
3260   S.Function.FoundDecl = Found;
3261   Steps.push_back(S);
3262 }
3263
3264 void InitializationSequence::AddDerivedToBaseCastStep(QualType BaseType,
3265                                                       ExprValueKind VK) {
3266   Step S;
3267   switch (VK) {
3268   case VK_RValue: S.Kind = SK_CastDerivedToBaseRValue; break;
3269   case VK_XValue: S.Kind = SK_CastDerivedToBaseXValue; break;
3270   case VK_LValue: S.Kind = SK_CastDerivedToBaseLValue; break;
3271   }
3272   S.Type = BaseType;
3273   Steps.push_back(S);
3274 }
3275
3276 void InitializationSequence::AddReferenceBindingStep(QualType T,
3277                                                      bool BindingTemporary) {
3278   Step S;
3279   S.Kind = BindingTemporary? SK_BindReferenceToTemporary : SK_BindReference;
3280   S.Type = T;
3281   Steps.push_back(S);
3282 }
3283
3284 void InitializationSequence::AddFinalCopy(QualType T) {
3285   Step S;
3286   S.Kind = SK_FinalCopy;
3287   S.Type = T;
3288   Steps.push_back(S);
3289 }
3290
3291 void InitializationSequence::AddExtraneousCopyToTemporary(QualType T) {
3292   Step S;
3293   S.Kind = SK_ExtraneousCopyToTemporary;
3294   S.Type = T;
3295   Steps.push_back(S);
3296 }
3297
3298 void
3299 InitializationSequence::AddUserConversionStep(FunctionDecl *Function,
3300                                               DeclAccessPair FoundDecl,
3301                                               QualType T,
3302                                               bool HadMultipleCandidates) {
3303   Step S;
3304   S.Kind = SK_UserConversion;
3305   S.Type = T;
3306   S.Function.HadMultipleCandidates = HadMultipleCandidates;
3307   S.Function.Function = Function;
3308   S.Function.FoundDecl = FoundDecl;
3309   Steps.push_back(S);
3310 }
3311
3312 void InitializationSequence::AddQualificationConversionStep(QualType Ty,
3313                                                             ExprValueKind VK) {
3314   Step S;
3315   S.Kind = SK_QualificationConversionRValue; // work around a gcc warning
3316   switch (VK) {
3317   case VK_RValue:
3318     S.Kind = SK_QualificationConversionRValue;
3319     break;
3320   case VK_XValue:
3321     S.Kind = SK_QualificationConversionXValue;
3322     break;
3323   case VK_LValue:
3324     S.Kind = SK_QualificationConversionLValue;
3325     break;
3326   }
3327   S.Type = Ty;
3328   Steps.push_back(S);
3329 }
3330
3331 void InitializationSequence::AddAtomicConversionStep(QualType Ty) {
3332   Step S;
3333   S.Kind = SK_AtomicConversion;
3334   S.Type = Ty;
3335   Steps.push_back(S);
3336 }
3337
3338 void InitializationSequence::AddLValueToRValueStep(QualType Ty) {
3339   assert(!Ty.hasQualifiers() && "rvalues may not have qualifiers");
3340
3341   Step S;
3342   S.Kind = SK_LValueToRValue;
3343   S.Type = Ty;
3344   Steps.push_back(S);
3345 }
3346
3347 void InitializationSequence::AddConversionSequenceStep(
3348     const ImplicitConversionSequence &ICS, QualType T,
3349     bool TopLevelOfInitList) {
3350   Step S;
3351   S.Kind = TopLevelOfInitList ? SK_ConversionSequenceNoNarrowing
3352                               : SK_ConversionSequence;
3353   S.Type = T;
3354   S.ICS = new ImplicitConversionSequence(ICS);
3355   Steps.push_back(S);
3356 }
3357
3358 void InitializationSequence::AddListInitializationStep(QualType T) {
3359   Step S;
3360   S.Kind = SK_ListInitialization;
3361   S.Type = T;
3362   Steps.push_back(S);
3363 }
3364
3365 void InitializationSequence::AddConstructorInitializationStep(
3366     DeclAccessPair FoundDecl, CXXConstructorDecl *Constructor, QualType T,
3367     bool HadMultipleCandidates, bool FromInitList, bool AsInitList) {
3368   Step S;
3369   S.Kind = FromInitList ? AsInitList ? SK_StdInitializerListConstructorCall
3370                                      : SK_ConstructorInitializationFromList
3371                         : SK_ConstructorInitialization;
3372   S.Type = T;
3373   S.Function.HadMultipleCandidates = HadMultipleCandidates;
3374   S.Function.Function = Constructor;
3375   S.Function.FoundDecl = FoundDecl;
3376   Steps.push_back(S);
3377 }
3378
3379 void InitializationSequence::AddZeroInitializationStep(QualType T) {
3380   Step S;
3381   S.Kind = SK_ZeroInitialization;
3382   S.Type = T;
3383   Steps.push_back(S);
3384 }
3385
3386 void InitializationSequence::AddCAssignmentStep(QualType T) {
3387   Step S;
3388   S.Kind = SK_CAssignment;
3389   S.Type = T;
3390   Steps.push_back(S);
3391 }
3392
3393 void InitializationSequence::AddStringInitStep(QualType T) {
3394   Step S;
3395   S.Kind = SK_StringInit;
3396   S.Type = T;
3397   Steps.push_back(S);
3398 }
3399
3400 void InitializationSequence::AddObjCObjectConversionStep(QualType T) {
3401   Step S;
3402   S.Kind = SK_ObjCObjectConversion;
3403   S.Type = T;
3404   Steps.push_back(S);
3405 }
3406
3407 void InitializationSequence::AddArrayInitStep(QualType T, bool IsGNUExtension) {
3408   Step S;
3409   S.Kind = IsGNUExtension ? SK_GNUArrayInit : SK_ArrayInit;
3410   S.Type = T;
3411   Steps.push_back(S);
3412 }
3413
3414 void InitializationSequence::AddArrayInitLoopStep(QualType T, QualType EltT) {
3415   Step S;
3416   S.Kind = SK_ArrayLoopIndex;
3417   S.Type = EltT;
3418   Steps.insert(Steps.begin(), S);
3419
3420   S.Kind = SK_ArrayLoopInit;
3421   S.Type = T;
3422   Steps.push_back(S);
3423 }
3424
3425 void InitializationSequence::AddParenthesizedArrayInitStep(QualType T) {
3426   Step S;
3427   S.Kind = SK_ParenthesizedArrayInit;
3428   S.Type = T;
3429   Steps.push_back(S);
3430 }
3431
3432 void InitializationSequence::AddPassByIndirectCopyRestoreStep(QualType type,
3433                                                               bool shouldCopy) {
3434   Step s;
3435   s.Kind = (shouldCopy ? SK_PassByIndirectCopyRestore
3436                        : SK_PassByIndirectRestore);
3437   s.Type = type;
3438   Steps.push_back(s);
3439 }
3440
3441 void InitializationSequence::AddProduceObjCObjectStep(QualType T) {
3442   Step S;
3443   S.Kind = SK_ProduceObjCObject;
3444   S.Type = T;
3445   Steps.push_back(S);
3446 }
3447
3448 void InitializationSequence::AddStdInitializerListConstructionStep(QualType T) {
3449   Step S;
3450   S.Kind = SK_StdInitializerList;
3451   S.Type = T;
3452   Steps.push_back(S);
3453 }
3454
3455 void InitializationSequence::AddOCLSamplerInitStep(QualType T) {
3456   Step S;
3457   S.Kind = SK_OCLSamplerInit;
3458   S.Type = T;
3459   Steps.push_back(S);
3460 }
3461
3462 void InitializationSequence::AddOCLZeroEventStep(QualType T) {
3463   Step S;
3464   S.Kind = SK_OCLZeroEvent;
3465   S.Type = T;
3466   Steps.push_back(S);
3467 }
3468
3469 void InitializationSequence::AddOCLZeroQueueStep(QualType T) {
3470   Step S;
3471   S.Kind = SK_OCLZeroQueue;
3472   S.Type = T;
3473   Steps.push_back(S);
3474 }
3475
3476 void InitializationSequence::RewrapReferenceInitList(QualType T,
3477                                                      InitListExpr *Syntactic) {
3478   assert(Syntactic->getNumInits() == 1 &&
3479          "Can only rewrap trivial init lists.");
3480   Step S;
3481   S.Kind = SK_UnwrapInitList;
3482   S.Type = Syntactic->getInit(0)->getType();
3483   Steps.insert(Steps.begin(), S);
3484
3485   S.Kind = SK_RewrapInitList;
3486   S.Type = T;
3487   S.WrappingSyntacticList = Syntactic;
3488   Steps.push_back(S);
3489 }
3490
3491 void InitializationSequence::SetOverloadFailure(FailureKind Failure,
3492                                                 OverloadingResult Result) {
3493   setSequenceKind(FailedSequence);
3494   this->Failure = Failure;
3495   this->FailedOverloadResult = Result;
3496 }
3497
3498 //===----------------------------------------------------------------------===//
3499 // Attempt initialization
3500 //===----------------------------------------------------------------------===//
3501
3502 /// Tries to add a zero initializer. Returns true if that worked.
3503 static bool
3504 maybeRecoverWithZeroInitialization(Sema &S, InitializationSequence &Sequence,
3505                                    const InitializedEntity &Entity) {
3506   if (Entity.getKind() != InitializedEntity::EK_Variable)
3507     return false;
3508
3509   VarDecl *VD = cast<VarDecl>(Entity.getDecl());
3510   if (VD->getInit() || VD->getLocEnd().isMacroID())
3511     return false;
3512
3513   QualType VariableTy = VD->getType().getCanonicalType();
3514   SourceLocation Loc = S.getLocForEndOfToken(VD->getLocEnd());
3515   std::string Init = S.getFixItZeroInitializerForType(VariableTy, Loc);
3516   if (!Init.empty()) {
3517     Sequence.AddZeroInitializationStep(Entity.getType());
3518     Sequence.SetZeroInitializationFixit(Init, Loc);
3519     return true;
3520   }
3521   return false;
3522 }
3523
3524 static void MaybeProduceObjCObject(Sema &S,
3525                                    InitializationSequence &Sequence,
3526                                    const InitializedEntity &Entity) {
3527   if (!S.getLangOpts().ObjCAutoRefCount) return;
3528
3529   /// When initializing a parameter, produce the value if it's marked
3530   /// __attribute__((ns_consumed)).
3531   if (Entity.isParameterKind()) {
3532     if (!Entity.isParameterConsumed())
3533       return;
3534
3535     assert(Entity.getType()->isObjCRetainableType() &&
3536            "consuming an object of unretainable type?");
3537     Sequence.AddProduceObjCObjectStep(Entity.getType());
3538
3539   /// When initializing a return value, if the return type is a
3540   /// retainable type, then returns need to immediately retain the
3541   /// object.  If an autorelease is required, it will be done at the
3542   /// last instant.
3543   } else if (Entity.getKind() == InitializedEntity::EK_Result ||
3544              Entity.getKind() == InitializedEntity::EK_StmtExprResult) {
3545     if (!Entity.getType()->isObjCRetainableType())
3546       return;
3547
3548     Sequence.AddProduceObjCObjectStep(Entity.getType());
3549   }
3550 }
3551
3552 static void TryListInitialization(Sema &S,
3553                                   const InitializedEntity &Entity,
3554                                   const InitializationKind &Kind,
3555                                   InitListExpr *InitList,
3556                                   InitializationSequence &Sequence,
3557                                   bool TreatUnavailableAsInvalid);
3558
3559 /// When initializing from init list via constructor, handle
3560 /// initialization of an object of type std::initializer_list<T>.
3561 ///
3562 /// \return true if we have handled initialization of an object of type
3563 /// std::initializer_list<T>, false otherwise.
3564 static bool TryInitializerListConstruction(Sema &S,
3565                                            InitListExpr *List,
3566                                            QualType DestType,
3567                                            InitializationSequence &Sequence,
3568                                            bool TreatUnavailableAsInvalid) {
3569   QualType E;
3570   if (!S.isStdInitializerList(DestType, &E))
3571     return false;
3572
3573   if (!S.isCompleteType(List->getExprLoc(), E)) {
3574     Sequence.setIncompleteTypeFailure(E);
3575     return true;
3576   }
3577
3578   // Try initializing a temporary array from the init list.
3579   QualType ArrayType = S.Context.getConstantArrayType(
3580       E.withConst(), llvm::APInt(S.Context.getTypeSize(S.Context.getSizeType()),
3581                                  List->getNumInits()),
3582       clang::ArrayType::Normal, 0);
3583   InitializedEntity HiddenArray =
3584       InitializedEntity::InitializeTemporary(ArrayType);
3585   InitializationKind Kind = InitializationKind::CreateDirectList(
3586       List->getExprLoc(), List->getLocStart(), List->getLocEnd());
3587   TryListInitialization(S, HiddenArray, Kind, List, Sequence,
3588                         TreatUnavailableAsInvalid);
3589   if (Sequence)
3590     Sequence.AddStdInitializerListConstructionStep(DestType);
3591   return true;
3592 }
3593
3594 /// Determine if the constructor has the signature of a copy or move
3595 /// constructor for the type T of the class in which it was found. That is,
3596 /// determine if its first parameter is of type T or reference to (possibly
3597 /// cv-qualified) T.
3598 static bool hasCopyOrMoveCtorParam(ASTContext &Ctx,
3599                                    const ConstructorInfo &Info) {
3600   if (Info.Constructor->getNumParams() == 0)
3601     return false;
3602
3603   QualType ParmT =
3604       Info.Constructor->getParamDecl(0)->getType().getNonReferenceType();
3605   QualType ClassT =
3606       Ctx.getRecordType(cast<CXXRecordDecl>(Info.FoundDecl->getDeclContext()));
3607
3608   return Ctx.hasSameUnqualifiedType(ParmT, ClassT);
3609 }
3610
3611 static OverloadingResult
3612 ResolveConstructorOverload(Sema &S, SourceLocation DeclLoc,
3613                            MultiExprArg Args,
3614                            OverloadCandidateSet &CandidateSet,
3615                            QualType DestType,
3616                            DeclContext::lookup_result Ctors,
3617                            OverloadCandidateSet::iterator &Best,
3618                            bool CopyInitializing, bool AllowExplicit,
3619                            bool OnlyListConstructors, bool IsListInit,
3620                            bool SecondStepOfCopyInit = false) {
3621   CandidateSet.clear(OverloadCandidateSet::CSK_InitByConstructor);
3622
3623   for (NamedDecl *D : Ctors) {
3624     auto Info = getConstructorInfo(D);
3625     if (!Info.Constructor || Info.Constructor->isInvalidDecl())
3626       continue;
3627
3628     if (!AllowExplicit && Info.Constructor->isExplicit())
3629       continue;
3630
3631     if (OnlyListConstructors && !S.isInitListConstructor(Info.Constructor))
3632       continue;
3633
3634     // C++11 [over.best.ics]p4:
3635     //   ... and the constructor or user-defined conversion function is a
3636     //   candidate by
3637     //   - 13.3.1.3, when the argument is the temporary in the second step
3638     //     of a class copy-initialization, or
3639     //   - 13.3.1.4, 13.3.1.5, or 13.3.1.6 (in all cases), [not handled here]
3640     //   - the second phase of 13.3.1.7 when the initializer list has exactly
3641     //     one element that is itself an initializer list, and the target is
3642     //     the first parameter of a constructor of class X, and the conversion
3643     //     is to X or reference to (possibly cv-qualified X),
3644     //   user-defined conversion sequences are not considered.
3645     bool SuppressUserConversions =
3646         SecondStepOfCopyInit ||
3647         (IsListInit && Args.size() == 1 && isa<InitListExpr>(Args[0]) &&
3648          hasCopyOrMoveCtorParam(S.Context, Info));
3649
3650     if (Info.ConstructorTmpl)
3651       S.AddTemplateOverloadCandidate(Info.ConstructorTmpl, Info.FoundDecl,
3652                                      /*ExplicitArgs*/ nullptr, Args,
3653                                      CandidateSet, SuppressUserConversions);
3654     else {
3655       // C++ [over.match.copy]p1:
3656       //   - When initializing a temporary to be bound to the first parameter
3657       //     of a constructor [for type T] that takes a reference to possibly
3658       //     cv-qualified T as its first argument, called with a single
3659       //     argument in the context of direct-initialization, explicit
3660       //     conversion functions are also considered.
3661       // FIXME: What if a constructor template instantiates to such a signature?
3662       bool AllowExplicitConv = AllowExplicit && !CopyInitializing &&
3663                                Args.size() == 1 &&
3664                                hasCopyOrMoveCtorParam(S.Context, Info);
3665       S.AddOverloadCandidate(Info.Constructor, Info.FoundDecl, Args,
3666                              CandidateSet, SuppressUserConversions,
3667                              /*PartialOverloading=*/false,
3668                              /*AllowExplicit=*/AllowExplicitConv);
3669     }
3670   }
3671
3672   // FIXME: Work around a bug in C++17 guaranteed copy elision.
3673   //
3674   // When initializing an object of class type T by constructor
3675   // ([over.match.ctor]) or by list-initialization ([over.match.list])
3676   // from a single expression of class type U, conversion functions of
3677   // U that convert to the non-reference type cv T are candidates.
3678   // Explicit conversion functions are only candidates during
3679   // direct-initialization.
3680   //
3681   // Note: SecondStepOfCopyInit is only ever true in this case when
3682   // evaluating whether to produce a C++98 compatibility warning.
3683   if (S.getLangOpts().CPlusPlus17 && Args.size() == 1 &&
3684       !SecondStepOfCopyInit) {
3685     Expr *Initializer = Args[0];
3686     auto *SourceRD = Initializer->getType()->getAsCXXRecordDecl();
3687     if (SourceRD && S.isCompleteType(DeclLoc, Initializer->getType())) {
3688       const auto &Conversions = SourceRD->getVisibleConversionFunctions();
3689       for (auto I = Conversions.begin(), E = Conversions.end(); I != E; ++I) {
3690         NamedDecl *D = *I;
3691         CXXRecordDecl *ActingDC = cast<CXXRecordDecl>(D->getDeclContext());
3692         D = D->getUnderlyingDecl();
3693
3694         FunctionTemplateDecl *ConvTemplate = dyn_cast<FunctionTemplateDecl>(D);
3695         CXXConversionDecl *Conv;
3696         if (ConvTemplate)
3697           Conv = cast<CXXConversionDecl>(ConvTemplate->getTemplatedDecl());
3698         else
3699           Conv = cast<CXXConversionDecl>(D);
3700
3701         if ((AllowExplicit && !CopyInitializing) || !Conv->isExplicit()) {
3702           if (ConvTemplate)
3703             S.AddTemplateConversionCandidate(ConvTemplate, I.getPair(),
3704                                              ActingDC, Initializer, DestType,
3705                                              CandidateSet, AllowExplicit,
3706                                              /*AllowResultConversion*/false);
3707           else
3708             S.AddConversionCandidate(Conv, I.getPair(), ActingDC, Initializer,
3709                                      DestType, CandidateSet, AllowExplicit,
3710                                      /*AllowResultConversion*/false);
3711         }
3712       }
3713     }
3714   }
3715
3716   // Perform overload resolution and return the result.
3717   return CandidateSet.BestViableFunction(S, DeclLoc, Best);
3718 }
3719
3720 /// Attempt initialization by constructor (C++ [dcl.init]), which
3721 /// enumerates the constructors of the initialized entity and performs overload
3722 /// resolution to select the best.
3723 /// \param DestType       The destination class type.
3724 /// \param DestArrayType  The destination type, which is either DestType or
3725 ///                       a (possibly multidimensional) array of DestType.
3726 /// \param IsListInit     Is this list-initialization?
3727 /// \param IsInitListCopy Is this non-list-initialization resulting from a
3728 ///                       list-initialization from {x} where x is the same
3729 ///                       type as the entity?
3730 static void TryConstructorInitialization(Sema &S,
3731                                          const InitializedEntity &Entity,
3732                                          const InitializationKind &Kind,
3733                                          MultiExprArg Args, QualType DestType,
3734                                          QualType DestArrayType,
3735                                          InitializationSequence &Sequence,
3736                                          bool IsListInit = false,
3737                                          bool IsInitListCopy = false) {
3738   assert(((!IsListInit && !IsInitListCopy) ||
3739           (Args.size() == 1 && isa<InitListExpr>(Args[0]))) &&
3740          "IsListInit/IsInitListCopy must come with a single initializer list "
3741          "argument.");
3742   InitListExpr *ILE =
3743       (IsListInit || IsInitListCopy) ? cast<InitListExpr>(Args[0]) : nullptr;
3744   MultiExprArg UnwrappedArgs =
3745       ILE ? MultiExprArg(ILE->getInits(), ILE->getNumInits()) : Args;
3746
3747   // The type we're constructing needs to be complete.
3748   if (!S.isCompleteType(Kind.getLocation(), DestType)) {
3749     Sequence.setIncompleteTypeFailure(DestType);
3750     return;
3751   }
3752
3753   // C++17 [dcl.init]p17:
3754   //     - If the initializer expression is a prvalue and the cv-unqualified
3755   //       version of the source type is the same class as the class of the
3756   //       destination, the initializer expression is used to initialize the
3757   //       destination object.
3758   // Per DR (no number yet), this does not apply when initializing a base
3759   // class or delegating to another constructor from a mem-initializer.
3760   // ObjC++: Lambda captured by the block in the lambda to block conversion
3761   // should avoid copy elision.
3762   if (S.getLangOpts().CPlusPlus17 &&
3763       Entity.getKind() != InitializedEntity::EK_Base &&
3764       Entity.getKind() != InitializedEntity::EK_Delegating &&
3765       Entity.getKind() !=
3766           InitializedEntity::EK_LambdaToBlockConversionBlockElement &&
3767       UnwrappedArgs.size() == 1 && UnwrappedArgs[0]->isRValue() &&
3768       S.Context.hasSameUnqualifiedType(UnwrappedArgs[0]->getType(), DestType)) {
3769     // Convert qualifications if necessary.
3770     Sequence.AddQualificationConversionStep(DestType, VK_RValue);
3771     if (ILE)
3772       Sequence.RewrapReferenceInitList(DestType, ILE);
3773     return;
3774   }
3775
3776   const RecordType *DestRecordType = DestType->getAs<RecordType>();
3777   assert(DestRecordType && "Constructor initialization requires record type");
3778   CXXRecordDecl *DestRecordDecl
3779     = cast<CXXRecordDecl>(DestRecordType->getDecl());
3780
3781   // Build the candidate set directly in the initialization sequence
3782   // structure, so that it will persist if we fail.
3783   OverloadCandidateSet &CandidateSet = Sequence.getFailedCandidateSet();
3784
3785   // Determine whether we are allowed to call explicit constructors or
3786   // explicit conversion operators.
3787   bool AllowExplicit = Kind.AllowExplicit() || IsListInit;
3788   bool CopyInitialization = Kind.getKind() == InitializationKind::IK_Copy;
3789
3790   //   - Otherwise, if T is a class type, constructors are considered. The
3791   //     applicable constructors are enumerated, and the best one is chosen
3792   //     through overload resolution.
3793   DeclContext::lookup_result Ctors = S.LookupConstructors(DestRecordDecl);
3794
3795   OverloadingResult Result = OR_No_Viable_Function;
3796   OverloadCandidateSet::iterator Best;
3797   bool AsInitializerList = false;
3798
3799   // C++11 [over.match.list]p1, per DR1467:
3800   //   When objects of non-aggregate type T are list-initialized, such that
3801   //   8.5.4 [dcl.init.list] specifies that overload resolution is performed
3802   //   according to the rules in this section, overload resolution selects
3803   //   the constructor in two phases:
3804   //
3805   //   - Initially, the candidate functions are the initializer-list
3806   //     constructors of the class T and the argument list consists of the
3807   //     initializer list as a single argument.
3808   if (IsListInit) {
3809     AsInitializerList = true;
3810
3811     // If the initializer list has no elements and T has a default constructor,
3812     // the first phase is omitted.
3813     if (!(UnwrappedArgs.empty() && DestRecordDecl->hasDefaultConstructor()))
3814       Result = ResolveConstructorOverload(S, Kind.getLocation(), Args,
3815                                           CandidateSet, DestType, Ctors, Best,
3816                                           CopyInitialization, AllowExplicit,
3817                                           /*OnlyListConstructor=*/true,
3818                                           IsListInit);
3819   }
3820
3821   // C++11 [over.match.list]p1:
3822   //   - If no viable initializer-list constructor is found, overload resolution
3823   //     is performed again, where the candidate functions are all the
3824   //     constructors of the class T and the argument list consists of the
3825   //     elements of the initializer list.
3826   if (Result == OR_No_Viable_Function) {
3827     AsInitializerList = false;
3828     Result = ResolveConstructorOverload(S, Kind.getLocation(), UnwrappedArgs,
3829                                         CandidateSet, DestType, Ctors, Best,
3830                                         CopyInitialization, AllowExplicit,
3831                                         /*OnlyListConstructors=*/false,
3832                                         IsListInit);
3833   }
3834   if (Result) {
3835     Sequence.SetOverloadFailure(IsListInit ?
3836                       InitializationSequence::FK_ListConstructorOverloadFailed :
3837                       InitializationSequence::FK_ConstructorOverloadFailed,
3838                                 Result);
3839     return;
3840   }
3841
3842   bool HadMultipleCandidates = (CandidateSet.size() > 1);
3843
3844   // In C++17, ResolveConstructorOverload can select a conversion function
3845   // instead of a constructor.
3846   if (auto *CD = dyn_cast<CXXConversionDecl>(Best->Function)) {
3847     // Add the user-defined conversion step that calls the conversion function.
3848     QualType ConvType = CD->getConversionType();
3849     assert(S.Context.hasSameUnqualifiedType(ConvType, DestType) &&
3850            "should not have selected this conversion function");
3851     Sequence.AddUserConversionStep(CD, Best->FoundDecl, ConvType,
3852                                    HadMultipleCandidates);
3853     if (!S.Context.hasSameType(ConvType, DestType))
3854       Sequence.AddQualificationConversionStep(DestType, VK_RValue);
3855     if (IsListInit)
3856       Sequence.RewrapReferenceInitList(Entity.getType(), ILE);
3857     return;
3858   }
3859
3860   // C++11 [dcl.init]p6:
3861   //   If a program calls for the default initialization of an object
3862   //   of a const-qualified type T, T shall be a class type with a
3863   //   user-provided default constructor.
3864   // C++ core issue 253 proposal:
3865   //   If the implicit default constructor initializes all subobjects, no
3866   //   initializer should be required.
3867   // The 253 proposal is for example needed to process libstdc++ headers in 5.x.
3868   CXXConstructorDecl *CtorDecl = cast<CXXConstructorDecl>(Best->Function);
3869   if (Kind.getKind() == InitializationKind::IK_Default &&
3870       Entity.getType().isConstQualified()) {
3871     if (!CtorDecl->getParent()->allowConstDefaultInit()) {
3872       if (!maybeRecoverWithZeroInitialization(S, Sequence, Entity))
3873         Sequence.SetFailed(InitializationSequence::FK_DefaultInitOfConst);
3874       return;
3875     }
3876   }
3877
3878   // C++11 [over.match.list]p1:
3879   //   In copy-list-initialization, if an explicit constructor is chosen, the
3880   //   initializer is ill-formed.
3881   if (IsListInit && !Kind.AllowExplicit() && CtorDecl->isExplicit()) {
3882     Sequence.SetFailed(InitializationSequence::FK_ExplicitConstructor);
3883     return;
3884   }
3885
3886   // Add the constructor initialization step. Any cv-qualification conversion is
3887   // subsumed by the initialization.
3888   Sequence.AddConstructorInitializationStep(
3889       Best->FoundDecl, CtorDecl, DestArrayType, HadMultipleCandidates,
3890       IsListInit | IsInitListCopy, AsInitializerList);
3891 }
3892
3893 static bool
3894 ResolveOverloadedFunctionForReferenceBinding(Sema &S,
3895                                              Expr *Initializer,
3896                                              QualType &SourceType,
3897                                              QualType &UnqualifiedSourceType,
3898                                              QualType UnqualifiedTargetType,
3899                                              InitializationSequence &Sequence) {
3900   if (S.Context.getCanonicalType(UnqualifiedSourceType) ==
3901         S.Context.OverloadTy) {
3902     DeclAccessPair Found;
3903     bool HadMultipleCandidates = false;
3904     if (FunctionDecl *Fn
3905         = S.ResolveAddressOfOverloadedFunction(Initializer,
3906                                                UnqualifiedTargetType,
3907                                                false, Found,
3908                                                &HadMultipleCandidates)) {
3909       Sequence.AddAddressOverloadResolutionStep(Fn, Found,
3910                                                 HadMultipleCandidates);
3911       SourceType = Fn->getType();
3912       UnqualifiedSourceType = SourceType.getUnqualifiedType();
3913     } else if (!UnqualifiedTargetType->isRecordType()) {
3914       Sequence.SetFailed(InitializationSequence::FK_AddressOfOverloadFailed);
3915       return true;
3916     }
3917   }
3918   return false;
3919 }
3920
3921 static void TryReferenceInitializationCore(Sema &S,
3922                                            const InitializedEntity &Entity,
3923                                            const InitializationKind &Kind,
3924                                            Expr *Initializer,
3925                                            QualType cv1T1, QualType T1,
3926                                            Qualifiers T1Quals,
3927                                            QualType cv2T2, QualType T2,
3928                                            Qualifiers T2Quals,
3929                                            InitializationSequence &Sequence);
3930
3931 static void TryValueInitialization(Sema &S,
3932                                    const InitializedEntity &Entity,
3933                                    const InitializationKind &Kind,
3934                                    InitializationSequence &Sequence,
3935                                    InitListExpr *InitList = nullptr);
3936
3937 /// Attempt list initialization of a reference.
3938 static void TryReferenceListInitialization(Sema &S,
3939                                            const InitializedEntity &Entity,
3940                                            const InitializationKind &Kind,
3941                                            InitListExpr *InitList,
3942                                            InitializationSequence &Sequence,
3943                                            bool TreatUnavailableAsInvalid) {
3944   // First, catch C++03 where this isn't possible.
3945   if (!S.getLangOpts().CPlusPlus11) {
3946     Sequence.SetFailed(InitializationSequence::FK_ReferenceBindingToInitList);
3947     return;
3948   }
3949   // Can't reference initialize a compound literal.
3950   if (Entity.getKind() == InitializedEntity::EK_CompoundLiteralInit) {
3951     Sequence.SetFailed(InitializationSequence::FK_ReferenceBindingToInitList);
3952     return;
3953   }
3954
3955   QualType DestType = Entity.getType();
3956   QualType cv1T1 = DestType->getAs<ReferenceType>()->getPointeeType();
3957   Qualifiers T1Quals;
3958   QualType T1 = S.Context.getUnqualifiedArrayType(cv1T1, T1Quals);
3959
3960   // Reference initialization via an initializer list works thus:
3961   // If the initializer list consists of a single element that is
3962   // reference-related to the referenced type, bind directly to that element
3963   // (possibly creating temporaries).
3964   // Otherwise, initialize a temporary with the initializer list and
3965   // bind to that.
3966   if (InitList->getNumInits() == 1) {
3967     Expr *Initializer = InitList->getInit(0);
3968     QualType cv2T2 = Initializer->getType();
3969     Qualifiers T2Quals;
3970     QualType T2 = S.Context.getUnqualifiedArrayType(cv2T2, T2Quals);
3971
3972     // If this fails, creating a temporary wouldn't work either.
3973     if (ResolveOverloadedFunctionForReferenceBinding(S, Initializer, cv2T2, T2,
3974                                                      T1, Sequence))
3975       return;
3976
3977     SourceLocation DeclLoc = Initializer->getLocStart();
3978     bool dummy1, dummy2, dummy3;
3979     Sema::ReferenceCompareResult RefRelationship
3980       = S.CompareReferenceRelationship(DeclLoc, cv1T1, cv2T2, dummy1,
3981                                        dummy2, dummy3);
3982     if (RefRelationship >= Sema::Ref_Related) {
3983       // Try to bind the reference here.
3984       TryReferenceInitializationCore(S, Entity, Kind, Initializer, cv1T1, T1,
3985                                      T1Quals, cv2T2, T2, T2Quals, Sequence);
3986       if (Sequence)
3987         Sequence.RewrapReferenceInitList(cv1T1, InitList);
3988       return;
3989     }
3990
3991     // Update the initializer if we've resolved an overloaded function.
3992     if (Sequence.step_begin() != Sequence.step_end())
3993       Sequence.RewrapReferenceInitList(cv1T1, InitList);
3994   }
3995
3996   // Not reference-related. Create a temporary and bind to that.
3997   InitializedEntity TempEntity = InitializedEntity::InitializeTemporary(cv1T1);
3998
3999   TryListInitialization(S, TempEntity, Kind, InitList, Sequence,
4000                         TreatUnavailableAsInvalid);
4001   if (Sequence) {
4002     if (DestType->isRValueReferenceType() ||
4003         (T1Quals.hasConst() && !T1Quals.hasVolatile()))
4004       Sequence.AddReferenceBindingStep(cv1T1, /*bindingTemporary=*/true);
4005     else
4006       Sequence.SetFailed(
4007           InitializationSequence::FK_NonConstLValueReferenceBindingToTemporary);
4008   }
4009 }
4010
4011 /// Attempt list initialization (C++0x [dcl.init.list])
4012 static void TryListInitialization(Sema &S,
4013                                   const InitializedEntity &Entity,
4014                                   const InitializationKind &Kind,
4015                                   InitListExpr *InitList,
4016                                   InitializationSequence &Sequence,
4017                                   bool TreatUnavailableAsInvalid) {
4018   QualType DestType = Entity.getType();
4019
4020   // C++ doesn't allow scalar initialization with more than one argument.
4021   // But C99 complex numbers are scalars and it makes sense there.
4022   if (S.getLangOpts().CPlusPlus && DestType->isScalarType() &&
4023       !DestType->isAnyComplexType() && InitList->getNumInits() > 1) {
4024     Sequence.SetFailed(InitializationSequence::FK_TooManyInitsForScalar);
4025     return;
4026   }
4027   if (DestType->isReferenceType()) {
4028     TryReferenceListInitialization(S, Entity, Kind, InitList, Sequence,
4029                                    TreatUnavailableAsInvalid);
4030     return;
4031   }
4032
4033   if (DestType->isRecordType() &&
4034       !S.isCompleteType(InitList->getLocStart(), DestType)) {
4035     Sequence.setIncompleteTypeFailure(DestType);
4036     return;
4037   }
4038
4039   // C++11 [dcl.init.list]p3, per DR1467:
4040   // - If T is a class type and the initializer list has a single element of
4041   //   type cv U, where U is T or a class derived from T, the object is
4042   //   initialized from that element (by copy-initialization for
4043   //   copy-list-initialization, or by direct-initialization for
4044   //   direct-list-initialization).
4045   // - Otherwise, if T is a character array and the initializer list has a
4046   //   single element that is an appropriately-typed string literal
4047   //   (8.5.2 [dcl.init.string]), initialization is performed as described
4048   //   in that section.
4049   // - Otherwise, if T is an aggregate, [...] (continue below).
4050   if (S.getLangOpts().CPlusPlus11 && InitList->getNumInits() == 1) {
4051     if (DestType->isRecordType()) {
4052       QualType InitType = InitList->getInit(0)->getType();
4053       if (S.Context.hasSameUnqualifiedType(InitType, DestType) ||
4054           S.IsDerivedFrom(InitList->getLocStart(), InitType, DestType)) {
4055         Expr *InitListAsExpr = InitList;
4056         TryConstructorInitialization(S, Entity, Kind, InitListAsExpr, DestType,
4057                                      DestType, Sequence,
4058                                      /*InitListSyntax*/false,
4059                                      /*IsInitListCopy*/true);
4060         return;
4061       }
4062     }
4063     if (const ArrayType *DestAT = S.Context.getAsArrayType(DestType)) {
4064       Expr *SubInit[1] = {InitList->getInit(0)};
4065       if (!isa<VariableArrayType>(DestAT) &&
4066           IsStringInit(SubInit[0], DestAT, S.Context) == SIF_None) {
4067         InitializationKind SubKind =
4068             Kind.getKind() == InitializationKind::IK_DirectList
4069                 ? InitializationKind::CreateDirect(Kind.getLocation(),
4070                                                    InitList->getLBraceLoc(),
4071                                                    InitList->getRBraceLoc())
4072                 : Kind;
4073         Sequence.InitializeFrom(S, Entity, SubKind, SubInit,
4074                                 /*TopLevelOfInitList*/ true,
4075                                 TreatUnavailableAsInvalid);
4076
4077         // TryStringLiteralInitialization() (in InitializeFrom()) will fail if
4078         // the element is not an appropriately-typed string literal, in which
4079         // case we should proceed as in C++11 (below).
4080         if (Sequence) {
4081           Sequence.RewrapReferenceInitList(Entity.getType(), InitList);
4082           return;
4083         }
4084       }
4085     }
4086   }
4087
4088   // C++11 [dcl.init.list]p3:
4089   //   - If T is an aggregate, aggregate initialization is performed.
4090   if ((DestType->isRecordType() && !DestType->isAggregateType()) ||
4091       (S.getLangOpts().CPlusPlus11 &&
4092        S.isStdInitializerList(DestType, nullptr))) {
4093     if (S.getLangOpts().CPlusPlus11) {
4094       //   - Otherwise, if the initializer list has no elements and T is a
4095       //     class type with a default constructor, the object is
4096       //     value-initialized.
4097       if (InitList->getNumInits() == 0) {
4098         CXXRecordDecl *RD = DestType->getAsCXXRecordDecl();
4099         if (RD->hasDefaultConstructor()) {
4100           TryValueInitialization(S, Entity, Kind, Sequence, InitList);
4101           return;
4102         }
4103       }
4104
4105       //   - Otherwise, if T is a specialization of std::initializer_list<E>,
4106       //     an initializer_list object constructed [...]
4107       if (TryInitializerListConstruction(S, InitList, DestType, Sequence,
4108                                          TreatUnavailableAsInvalid))
4109         return;
4110
4111       //   - Otherwise, if T is a class type, constructors are considered.
4112       Expr *InitListAsExpr = InitList;
4113       TryConstructorInitialization(S, Entity, Kind, InitListAsExpr, DestType,
4114                                    DestType, Sequence, /*InitListSyntax*/true);
4115     } else
4116       Sequence.SetFailed(InitializationSequence::FK_InitListBadDestinationType);
4117     return;
4118   }
4119
4120   if (S.getLangOpts().CPlusPlus && !DestType->isAggregateType() &&
4121       InitList->getNumInits() == 1) {
4122     Expr *E = InitList->getInit(0);
4123
4124     //   - Otherwise, if T is an enumeration with a fixed underlying type,
4125     //     the initializer-list has a single element v, and the initialization
4126     //     is direct-list-initialization, the object is initialized with the
4127     //     value T(v); if a narrowing conversion is required to convert v to
4128     //     the underlying type of T, the program is ill-formed.
4129     auto *ET = DestType->getAs<EnumType>();
4130     if (S.getLangOpts().CPlusPlus17 &&
4131         Kind.getKind() == InitializationKind::IK_DirectList &&
4132         ET && ET->getDecl()->isFixed() &&
4133         !S.Context.hasSameUnqualifiedType(E->getType(), DestType) &&
4134         (E->getType()->isIntegralOrEnumerationType() ||
4135          E->getType()->isFloatingType())) {
4136       // There are two ways that T(v) can work when T is an enumeration type.
4137       // If there is either an implicit conversion sequence from v to T or
4138       // a conversion function that can convert from v to T, then we use that.
4139       // Otherwise, if v is of integral, enumeration, or floating-point type,
4140       // it is converted to the enumeration type via its underlying type.
4141       // There is no overlap possible between these two cases (except when the
4142       // source value is already of the destination type), and the first
4143       // case is handled by the general case for single-element lists below.
4144       ImplicitConversionSequence ICS;
4145       ICS.setStandard();
4146       ICS.Standard.setAsIdentityConversion();
4147       if (!E->isRValue())
4148         ICS.Standard.First = ICK_Lvalue_To_Rvalue;
4149       // If E is of a floating-point type, then the conversion is ill-formed
4150       // due to narrowing, but go through the motions in order to produce the
4151       // right diagnostic.
4152       ICS.Standard.Second = E->getType()->isFloatingType()
4153                                 ? ICK_Floating_Integral
4154                                 : ICK_Integral_Conversion;
4155       ICS.Standard.setFromType(E->getType());
4156       ICS.Standard.setToType(0, E->getType());
4157       ICS.Standard.setToType(1, DestType);
4158       ICS.Standard.setToType(2, DestType);
4159       Sequence.AddConversionSequenceStep(ICS, ICS.Standard.getToType(2),
4160                                          /*TopLevelOfInitList*/true);
4161       Sequence.RewrapReferenceInitList(Entity.getType(), InitList);
4162       return;
4163     }
4164
4165     //   - Otherwise, if the initializer list has a single element of type E
4166     //     [...references are handled above...], the object or reference is
4167     //     initialized from that element (by copy-initialization for
4168     //     copy-list-initialization, or by direct-initialization for
4169     //     direct-list-initialization); if a narrowing conversion is required
4170     //     to convert the element to T, the program is ill-formed.
4171     //
4172     // Per core-24034, this is direct-initialization if we were performing
4173     // direct-list-initialization and copy-initialization otherwise.
4174     // We can't use InitListChecker for this, because it always performs
4175     // copy-initialization. This only matters if we might use an 'explicit'
4176     // conversion operator, so we only need to handle the cases where the source
4177     // is of record type.
4178     if (InitList->getInit(0)->getType()->isRecordType()) {
4179       InitializationKind SubKind =
4180           Kind.getKind() == InitializationKind::IK_DirectList
4181               ? InitializationKind::CreateDirect(Kind.getLocation(),
4182                                                  InitList->getLBraceLoc(),
4183                                                  InitList->getRBraceLoc())
4184               : Kind;
4185       Expr *SubInit[1] = { InitList->getInit(0) };
4186       Sequence.InitializeFrom(S, Entity, SubKind, SubInit,
4187                               /*TopLevelOfInitList*/true,
4188                               TreatUnavailableAsInvalid);
4189       if (Sequence)
4190         Sequence.RewrapReferenceInitList(Entity.getType(), InitList);
4191       return;
4192     }
4193   }
4194
4195   InitListChecker CheckInitList(S, Entity, InitList,
4196           DestType, /*VerifyOnly=*/true, TreatUnavailableAsInvalid);
4197   if (CheckInitList.HadError()) {
4198     Sequence.SetFailed(InitializationSequence::FK_ListInitializationFailed);
4199     return;
4200   }
4201
4202   // Add the list initialization step with the built init list.
4203   Sequence.AddListInitializationStep(DestType);
4204 }
4205
4206 /// Try a reference initialization that involves calling a conversion
4207 /// function.
4208 static OverloadingResult TryRefInitWithConversionFunction(
4209     Sema &S, const InitializedEntity &Entity, const InitializationKind &Kind,
4210     Expr *Initializer, bool AllowRValues, bool IsLValueRef,
4211     InitializationSequence &Sequence) {
4212   QualType DestType = Entity.getType();
4213   QualType cv1T1 = DestType->getAs<ReferenceType>()->getPointeeType();
4214   QualType T1 = cv1T1.getUnqualifiedType();
4215   QualType cv2T2 = Initializer->getType();
4216   QualType T2 = cv2T2.getUnqualifiedType();
4217
4218   bool DerivedToBase;
4219   bool ObjCConversion;
4220   bool ObjCLifetimeConversion;
4221   assert(!S.CompareReferenceRelationship(Initializer->getLocStart(),
4222                                          T1, T2, DerivedToBase,
4223                                          ObjCConversion,
4224                                          ObjCLifetimeConversion) &&
4225          "Must have incompatible references when binding via conversion");
4226   (void)DerivedToBase;
4227   (void)ObjCConversion;
4228   (void)ObjCLifetimeConversion;
4229
4230   // Build the candidate set directly in the initialization sequence
4231   // structure, so that it will persist if we fail.
4232   OverloadCandidateSet &CandidateSet = Sequence.getFailedCandidateSet();
4233   CandidateSet.clear(OverloadCandidateSet::CSK_InitByUserDefinedConversion);
4234
4235   // Determine whether we are allowed to call explicit conversion operators.
4236   // Note that none of [over.match.copy], [over.match.conv], nor
4237   // [over.match.ref] permit an explicit constructor to be chosen when
4238   // initializing a reference, not even for direct-initialization.
4239   bool AllowExplicitCtors = false;
4240   bool AllowExplicitConvs = Kind.allowExplicitConversionFunctionsInRefBinding();
4241
4242   const RecordType *T1RecordType = nullptr;
4243   if (AllowRValues && (T1RecordType = T1->getAs<RecordType>()) &&
4244       S.isCompleteType(Kind.getLocation(), T1)) {
4245     // The type we're converting to is a class type. Enumerate its constructors
4246     // to see if there is a suitable conversion.
4247     CXXRecordDecl *T1RecordDecl = cast<CXXRecordDecl>(T1RecordType->getDecl());
4248
4249     for (NamedDecl *D : S.LookupConstructors(T1RecordDecl)) {
4250       auto Info = getConstructorInfo(D);
4251       if (!Info.Constructor)
4252         continue;
4253
4254       if (!Info.Constructor->isInvalidDecl() &&
4255           Info.Constructor->isConvertingConstructor(AllowExplicitCtors)) {
4256         if (Info.ConstructorTmpl)
4257           S.AddTemplateOverloadCandidate(Info.ConstructorTmpl, Info.FoundDecl,
4258                                          /*ExplicitArgs*/ nullptr,
4259                                          Initializer, CandidateSet,
4260                                          /*SuppressUserConversions=*/true);
4261         else
4262           S.AddOverloadCandidate(Info.Constructor, Info.FoundDecl,
4263                                  Initializer, CandidateSet,
4264                                  /*SuppressUserConversions=*/true);
4265       }
4266     }
4267   }
4268   if (T1RecordType && T1RecordType->getDecl()->isInvalidDecl())
4269     return OR_No_Viable_Function;
4270
4271   const RecordType *T2RecordType = nullptr;
4272   if ((T2RecordType = T2->getAs<RecordType>()) &&
4273       S.isCompleteType(Kind.getLocation(), T2)) {
4274     // The type we're converting from is a class type, enumerate its conversion
4275     // functions.
4276     CXXRecordDecl *T2RecordDecl = cast<CXXRecordDecl>(T2RecordType->getDecl());
4277
4278     const auto &Conversions = T2RecordDecl->getVisibleConversionFunctions();
4279     for (auto I = Conversions.begin(), E = Conversions.end(); I != E; ++I) {
4280       NamedDecl *D = *I;
4281       CXXRecordDecl *ActingDC = cast<CXXRecordDecl>(D->getDeclContext());
4282       if (isa<UsingShadowDecl>(D))
4283         D = cast<UsingShadowDecl>(D)->getTargetDecl();
4284
4285       FunctionTemplateDecl *ConvTemplate = dyn_cast<FunctionTemplateDecl>(D);
4286       CXXConversionDecl *Conv;
4287       if (ConvTemplate)
4288         Conv = cast<CXXConversionDecl>(ConvTemplate->getTemplatedDecl());
4289       else
4290         Conv = cast<CXXConversionDecl>(D);
4291
4292       // If the conversion function doesn't return a reference type,
4293       // it can't be considered for this conversion unless we're allowed to
4294       // consider rvalues.
4295       // FIXME: Do we need to make sure that we only consider conversion
4296       // candidates with reference-compatible results? That might be needed to
4297       // break recursion.
4298       if ((AllowExplicitConvs || !Conv->isExplicit()) &&
4299           (AllowRValues || Conv->getConversionType()->isLValueReferenceType())){
4300         if (ConvTemplate)
4301           S.AddTemplateConversionCandidate(ConvTemplate, I.getPair(),
4302                                            ActingDC, Initializer,
4303                                            DestType, CandidateSet,
4304                                            /*AllowObjCConversionOnExplicit=*/
4305                                              false);
4306         else
4307           S.AddConversionCandidate(Conv, I.getPair(), ActingDC,
4308                                    Initializer, DestType, CandidateSet,
4309                                    /*AllowObjCConversionOnExplicit=*/false);
4310       }
4311     }
4312   }
4313   if (T2RecordType && T2RecordType->getDecl()->isInvalidDecl())
4314     return OR_No_Viable_Function;
4315
4316   SourceLocation DeclLoc = Initializer->getLocStart();
4317
4318   // Perform overload resolution. If it fails, return the failed result.
4319   OverloadCandidateSet::iterator Best;
4320   if (OverloadingResult Result
4321         = CandidateSet.BestViableFunction(S, DeclLoc, Best))
4322     return Result;
4323
4324   FunctionDecl *Function = Best->Function;
4325   // This is the overload that will be used for this initialization step if we
4326   // use this initialization. Mark it as referenced.
4327   Function->setReferenced();
4328
4329   // Compute the returned type and value kind of the conversion.
4330   QualType cv3T3;
4331   if (isa<CXXConversionDecl>(Function))
4332     cv3T3 = Function->getReturnType();
4333   else
4334     cv3T3 = T1;
4335
4336   ExprValueKind VK = VK_RValue;
4337   if (cv3T3->isLValueReferenceType())
4338     VK = VK_LValue;
4339   else if (const auto *RRef = cv3T3->getAs<RValueReferenceType>())
4340     VK = RRef->getPointeeType()->isFunctionType() ? VK_LValue : VK_XValue;
4341   cv3T3 = cv3T3.getNonLValueExprType(S.Context);
4342
4343   // Add the user-defined conversion step.
4344   bool HadMultipleCandidates = (CandidateSet.size() > 1);
4345   Sequence.AddUserConversionStep(Function, Best->FoundDecl, cv3T3,
4346                                  HadMultipleCandidates);
4347
4348   // Determine whether we'll need to perform derived-to-base adjustments or
4349   // other conversions.
4350   bool NewDerivedToBase = false;
4351   bool NewObjCConversion = false;
4352   bool NewObjCLifetimeConversion = false;
4353   Sema::ReferenceCompareResult NewRefRelationship
4354     = S.CompareReferenceRelationship(DeclLoc, T1, cv3T3,
4355                                      NewDerivedToBase, NewObjCConversion,
4356                                      NewObjCLifetimeConversion);
4357
4358   // Add the final conversion sequence, if necessary.
4359   if (NewRefRelationship == Sema::Ref_Incompatible) {
4360     assert(!isa<CXXConstructorDecl>(Function) &&
4361            "should not have conversion after constructor");
4362
4363     ImplicitConversionSequence ICS;
4364     ICS.setStandard();
4365     ICS.Standard = Best->FinalConversion;
4366     Sequence.AddConversionSequenceStep(ICS, ICS.Standard.getToType(2));
4367
4368     // Every implicit conversion results in a prvalue, except for a glvalue
4369     // derived-to-base conversion, which we handle below.
4370     cv3T3 = ICS.Standard.getToType(2);
4371     VK = VK_RValue;
4372   }
4373
4374   //   If the converted initializer is a prvalue, its type T4 is adjusted to
4375   //   type "cv1 T4" and the temporary materialization conversion is applied.
4376   //
4377   // We adjust the cv-qualifications to match the reference regardless of
4378   // whether we have a prvalue so that the AST records the change. In this
4379   // case, T4 is "cv3 T3".
4380   QualType cv1T4 = S.Context.getQualifiedType(cv3T3, cv1T1.getQualifiers());
4381   if (cv1T4.getQualifiers() != cv3T3.getQualifiers())
4382     Sequence.AddQualificationConversionStep(cv1T4, VK);
4383   Sequence.AddReferenceBindingStep(cv1T4, VK == VK_RValue);
4384   VK = IsLValueRef ? VK_LValue : VK_XValue;
4385
4386   if (NewDerivedToBase)
4387     Sequence.AddDerivedToBaseCastStep(cv1T1, VK);
4388   else if (NewObjCConversion)
4389     Sequence.AddObjCObjectConversionStep(cv1T1);
4390
4391   return OR_Success;
4392 }
4393
4394 static void CheckCXX98CompatAccessibleCopy(Sema &S,
4395                                            const InitializedEntity &Entity,
4396                                            Expr *CurInitExpr);
4397
4398 /// Attempt reference initialization (C++0x [dcl.init.ref])
4399 static void TryReferenceInitialization(Sema &S,
4400                                        const InitializedEntity &Entity,
4401                                        const InitializationKind &Kind,
4402                                        Expr *Initializer,
4403                                        InitializationSequence &Sequence) {
4404   QualType DestType = Entity.getType();
4405   QualType cv1T1 = DestType->getAs<ReferenceType>()->getPointeeType();
4406   Qualifiers T1Quals;
4407   QualType T1 = S.Context.getUnqualifiedArrayType(cv1T1, T1Quals);
4408   QualType cv2T2 = Initializer->getType();
4409   Qualifiers T2Quals;
4410   QualType T2 = S.Context.getUnqualifiedArrayType(cv2T2, T2Quals);
4411
4412   // If the initializer is the address of an overloaded function, try
4413   // to resolve the overloaded function. If all goes well, T2 is the
4414   // type of the resulting function.
4415   if (ResolveOverloadedFunctionForReferenceBinding(S, Initializer, cv2T2, T2,
4416                                                    T1, Sequence))
4417     return;
4418
4419   // Delegate everything else to a subfunction.
4420   TryReferenceInitializationCore(S, Entity, Kind, Initializer, cv1T1, T1,
4421                                  T1Quals, cv2T2, T2, T2Quals, Sequence);
4422 }
4423
4424 /// Determine whether an expression is a non-referenceable glvalue (one to
4425 /// which a reference can never bind). Attempting to bind a reference to
4426 /// such a glvalue will always create a temporary.
4427 static bool isNonReferenceableGLValue(Expr *E) {
4428   return E->refersToBitField() || E->refersToVectorElement();
4429 }
4430
4431 /// Reference initialization without resolving overloaded functions.
4432 static void TryReferenceInitializationCore(Sema &S,
4433                                            const InitializedEntity &Entity,
4434                                            const InitializationKind &Kind,
4435                                            Expr *Initializer,
4436                                            QualType cv1T1, QualType T1,
4437                                            Qualifiers T1Quals,
4438                                            QualType cv2T2, QualType T2,
4439                                            Qualifiers T2Quals,
4440                                            InitializationSequence &Sequence) {
4441   QualType DestType = Entity.getType();
4442   SourceLocation DeclLoc = Initializer->getLocStart();
4443   // Compute some basic properties of the types and the initializer.
4444   bool isLValueRef = DestType->isLValueReferenceType();
4445   bool isRValueRef = !isLValueRef;
4446   bool DerivedToBase = false;
4447   bool ObjCConversion = false;
4448   bool ObjCLifetimeConversion = false;
4449   Expr::Classification InitCategory = Initializer->Classify(S.Context);
4450   Sema::ReferenceCompareResult RefRelationship
4451     = S.CompareReferenceRelationship(DeclLoc, cv1T1, cv2T2, DerivedToBase,
4452                                      ObjCConversion, ObjCLifetimeConversion);
4453
4454   // C++0x [dcl.init.ref]p5:
4455   //   A reference to type "cv1 T1" is initialized by an expression of type
4456   //   "cv2 T2" as follows:
4457   //
4458   //     - If the reference is an lvalue reference and the initializer
4459   //       expression
4460   // Note the analogous bullet points for rvalue refs to functions. Because
4461   // there are no function rvalues in C++, rvalue refs to functions are treated
4462   // like lvalue refs.
4463   OverloadingResult ConvOvlResult = OR_Success;
4464   bool T1Function = T1->isFunctionType();
4465   if (isLValueRef || T1Function) {
4466     if (InitCategory.isLValue() && !isNonReferenceableGLValue(Initializer) &&
4467         (RefRelationship == Sema::Ref_Compatible ||
4468          (Kind.isCStyleOrFunctionalCast() &&
4469           RefRelationship == Sema::Ref_Related))) {
4470       //   - is an lvalue (but is not a bit-field), and "cv1 T1" is
4471       //     reference-compatible with "cv2 T2," or
4472       if (T1Quals != T2Quals)
4473         // Convert to cv1 T2. This should only add qualifiers unless this is a
4474         // c-style cast. The removal of qualifiers in that case notionally
4475         // happens after the reference binding, but that doesn't matter.
4476         Sequence.AddQualificationConversionStep(
4477             S.Context.getQualifiedType(T2, T1Quals),
4478             Initializer->getValueKind());
4479       if (DerivedToBase)
4480         Sequence.AddDerivedToBaseCastStep(cv1T1, VK_LValue);
4481       else if (ObjCConversion)
4482         Sequence.AddObjCObjectConversionStep(cv1T1);
4483
4484       // We only create a temporary here when binding a reference to a
4485       // bit-field or vector element. Those cases are't supposed to be
4486       // handled by this bullet, but the outcome is the same either way.
4487       Sequence.AddReferenceBindingStep(cv1T1, false);
4488       return;
4489     }
4490
4491     //     - has a class type (i.e., T2 is a class type), where T1 is not
4492     //       reference-related to T2, and can be implicitly converted to an
4493     //       lvalue of type "cv3 T3," where "cv1 T1" is reference-compatible
4494     //       with "cv3 T3" (this conversion is selected by enumerating the
4495     //       applicable conversion functions (13.3.1.6) and choosing the best
4496     //       one through overload resolution (13.3)),
4497     // If we have an rvalue ref to function type here, the rhs must be
4498     // an rvalue. DR1287 removed the "implicitly" here.
4499     if (RefRelationship == Sema::Ref_Incompatible && T2->isRecordType() &&
4500         (isLValueRef || InitCategory.isRValue())) {
4501       ConvOvlResult = TryRefInitWithConversionFunction(
4502           S, Entity, Kind, Initializer, /*AllowRValues*/ isRValueRef,
4503           /*IsLValueRef*/ isLValueRef, Sequence);
4504       if (ConvOvlResult == OR_Success)
4505         return;
4506       if (ConvOvlResult != OR_No_Viable_Function)
4507         Sequence.SetOverloadFailure(
4508             InitializationSequence::FK_ReferenceInitOverloadFailed,
4509             ConvOvlResult);
4510     }
4511   }
4512
4513   //     - Otherwise, the reference shall be an lvalue reference to a
4514   //       non-volatile const type (i.e., cv1 shall be const), or the reference
4515   //       shall be an rvalue reference.
4516   if (isLValueRef && !(T1Quals.hasConst() && !T1Quals.hasVolatile())) {
4517     if (S.Context.getCanonicalType(T2) == S.Context.OverloadTy)
4518       Sequence.SetFailed(InitializationSequence::FK_AddressOfOverloadFailed);
4519     else if (ConvOvlResult && !Sequence.getFailedCandidateSet().empty())
4520       Sequence.SetOverloadFailure(
4521                         InitializationSequence::FK_ReferenceInitOverloadFailed,
4522                                   ConvOvlResult);
4523     else if (!InitCategory.isLValue())
4524       Sequence.SetFailed(
4525           InitializationSequence::FK_NonConstLValueReferenceBindingToTemporary);
4526     else {
4527       InitializationSequence::FailureKind FK;
4528       switch (RefRelationship) {
4529       case Sema::Ref_Compatible:
4530         if (Initializer->refersToBitField())
4531           FK = InitializationSequence::
4532               FK_NonConstLValueReferenceBindingToBitfield;
4533         else if (Initializer->refersToVectorElement())
4534           FK = InitializationSequence::
4535               FK_NonConstLValueReferenceBindingToVectorElement;
4536         else
4537           llvm_unreachable("unexpected kind of compatible initializer");
4538         break;
4539       case Sema::Ref_Related:
4540         FK = InitializationSequence::FK_ReferenceInitDropsQualifiers;
4541         break;
4542       case Sema::Ref_Incompatible:
4543         FK = InitializationSequence::
4544             FK_NonConstLValueReferenceBindingToUnrelated;
4545         break;
4546       }
4547       Sequence.SetFailed(FK);
4548     }
4549     return;
4550   }
4551
4552   //    - If the initializer expression
4553   //      - is an
4554   // [<=14] xvalue (but not a bit-field), class prvalue, array prvalue, or
4555   // [1z]   rvalue (but not a bit-field) or
4556   //        function lvalue and "cv1 T1" is reference-compatible with "cv2 T2"
4557   //
4558   // Note: functions are handled above and below rather than here...
4559   if (!T1Function &&
4560       (RefRelationship == Sema::Ref_Compatible ||
4561        (Kind.isCStyleOrFunctionalCast() &&
4562         RefRelationship == Sema::Ref_Related)) &&
4563       ((InitCategory.isXValue() && !isNonReferenceableGLValue(Initializer)) ||
4564        (InitCategory.isPRValue() &&
4565         (S.getLangOpts().CPlusPlus17 || T2->isRecordType() ||
4566          T2->isArrayType())))) {
4567     ExprValueKind ValueKind = InitCategory.isXValue() ? VK_XValue : VK_RValue;
4568     if (InitCategory.isPRValue() && T2->isRecordType()) {
4569       // The corresponding bullet in C++03 [dcl.init.ref]p5 gives the
4570       // compiler the freedom to perform a copy here or bind to the
4571       // object, while C++0x requires that we bind directly to the
4572       // object. Hence, we always bind to the object without making an
4573       // extra copy. However, in C++03 requires that we check for the
4574       // presence of a suitable copy constructor:
4575       //
4576       //   The constructor that would be used to make the copy shall
4577       //   be callable whether or not the copy is actually done.
4578       if (!S.getLangOpts().CPlusPlus11 && !S.getLangOpts().MicrosoftExt)
4579         Sequence.AddExtraneousCopyToTemporary(cv2T2);
4580       else if (S.getLangOpts().CPlusPlus11)
4581         CheckCXX98CompatAccessibleCopy(S, Entity, Initializer);
4582     }
4583
4584     // C++1z [dcl.init.ref]/5.2.1.2:
4585     //   If the converted initializer is a prvalue, its type T4 is adjusted
4586     //   to type "cv1 T4" and the temporary materialization conversion is
4587     //   applied.
4588     QualType cv1T4 = S.Context.getQualifiedType(cv2T2, T1Quals);
4589     if (T1Quals != T2Quals)
4590       Sequence.AddQualificationConversionStep(cv1T4, ValueKind);
4591     Sequence.AddReferenceBindingStep(cv1T4, ValueKind == VK_RValue);
4592     ValueKind = isLValueRef ? VK_LValue : VK_XValue;
4593
4594     //   In any case, the reference is bound to the resulting glvalue (or to
4595     //   an appropriate base class subobject).
4596     if (DerivedToBase)
4597       Sequence.AddDerivedToBaseCastStep(cv1T1, ValueKind);
4598     else if (ObjCConversion)
4599       Sequence.AddObjCObjectConversionStep(cv1T1);
4600     return;
4601   }
4602
4603   //       - has a class type (i.e., T2 is a class type), where T1 is not
4604   //         reference-related to T2, and can be implicitly converted to an
4605   //         xvalue, class prvalue, or function lvalue of type "cv3 T3",
4606   //         where "cv1 T1" is reference-compatible with "cv3 T3",
4607   //
4608   // DR1287 removes the "implicitly" here.
4609   if (T2->isRecordType()) {
4610     if (RefRelationship == Sema::Ref_Incompatible) {
4611       ConvOvlResult = TryRefInitWithConversionFunction(
4612           S, Entity, Kind, Initializer, /*AllowRValues*/ true,
4613           /*IsLValueRef*/ isLValueRef, Sequence);
4614       if (ConvOvlResult)
4615         Sequence.SetOverloadFailure(
4616             InitializationSequence::FK_ReferenceInitOverloadFailed,
4617             ConvOvlResult);
4618
4619       return;
4620     }
4621
4622     if (RefRelationship == Sema::Ref_Compatible &&
4623         isRValueRef && InitCategory.isLValue()) {
4624       Sequence.SetFailed(
4625         InitializationSequence::FK_RValueReferenceBindingToLValue);
4626       return;
4627     }
4628
4629     Sequence.SetFailed(InitializationSequence::FK_ReferenceInitDropsQualifiers);
4630     return;
4631   }
4632
4633   //      - Otherwise, a temporary of type "cv1 T1" is created and initialized
4634   //        from the initializer expression using the rules for a non-reference
4635   //        copy-initialization (8.5). The reference is then bound to the
4636   //        temporary. [...]
4637
4638   InitializedEntity TempEntity = InitializedEntity::InitializeTemporary(cv1T1);
4639
4640   // FIXME: Why do we use an implicit conversion here rather than trying
4641   // copy-initialization?
4642   ImplicitConversionSequence ICS
4643     = S.TryImplicitConversion(Initializer, TempEntity.getType(),
4644                               /*SuppressUserConversions=*/false,
4645                               /*AllowExplicit=*/false,
4646                               /*FIXME:InOverloadResolution=*/false,
4647                               /*CStyle=*/Kind.isCStyleOrFunctionalCast(),
4648                               /*AllowObjCWritebackConversion=*/false);
4649
4650   if (ICS.isBad()) {
4651     // FIXME: Use the conversion function set stored in ICS to turn
4652     // this into an overloading ambiguity diagnostic. However, we need
4653     // to keep that set as an OverloadCandidateSet rather than as some
4654     // other kind of set.
4655     if (ConvOvlResult && !Sequence.getFailedCandidateSet().empty())
4656       Sequence.SetOverloadFailure(
4657                         InitializationSequence::FK_ReferenceInitOverloadFailed,
4658                                   ConvOvlResult);
4659     else if (S.Context.getCanonicalType(T2) == S.Context.OverloadTy)
4660       Sequence.SetFailed(InitializationSequence::FK_AddressOfOverloadFailed);
4661     else
4662       Sequence.SetFailed(InitializationSequence::FK_ReferenceInitFailed);
4663     return;
4664   } else {
4665     Sequence.AddConversionSequenceStep(ICS, TempEntity.getType());
4666   }
4667
4668   //        [...] If T1 is reference-related to T2, cv1 must be the
4669   //        same cv-qualification as, or greater cv-qualification
4670   //        than, cv2; otherwise, the program is ill-formed.
4671   unsigned T1CVRQuals = T1Quals.getCVRQualifiers();
4672   unsigned T2CVRQuals = T2Quals.getCVRQualifiers();
4673   if (RefRelationship == Sema::Ref_Related &&
4674       (T1CVRQuals | T2CVRQuals) != T1CVRQuals) {
4675     Sequence.SetFailed(InitializationSequence::FK_ReferenceInitDropsQualifiers);
4676     return;
4677   }
4678
4679   //   [...] If T1 is reference-related to T2 and the reference is an rvalue
4680   //   reference, the initializer expression shall not be an lvalue.
4681   if (RefRelationship >= Sema::Ref_Related && !isLValueRef &&
4682       InitCategory.isLValue()) {
4683     Sequence.SetFailed(
4684                     InitializationSequence::FK_RValueReferenceBindingToLValue);
4685     return;
4686   }
4687
4688   Sequence.AddReferenceBindingStep(cv1T1, /*bindingTemporary=*/true);
4689 }
4690
4691 /// Attempt character array initialization from a string literal
4692 /// (C++ [dcl.init.string], C99 6.7.8).
4693 static void TryStringLiteralInitialization(Sema &S,
4694                                            const InitializedEntity &Entity,
4695                                            const InitializationKind &Kind,
4696                                            Expr *Initializer,
4697                                        InitializationSequence &Sequence) {
4698   Sequence.AddStringInitStep(Entity.getType());
4699 }
4700
4701 /// Attempt value initialization (C++ [dcl.init]p7).
4702 static void TryValueInitialization(Sema &S,
4703                                    const InitializedEntity &Entity,
4704                                    const InitializationKind &Kind,
4705                                    InitializationSequence &Sequence,
4706                                    InitListExpr *InitList) {
4707   assert((!InitList || InitList->getNumInits() == 0) &&
4708          "Shouldn't use value-init for non-empty init lists");
4709
4710   // C++98 [dcl.init]p5, C++11 [dcl.init]p7:
4711   //
4712   //   To value-initialize an object of type T means:
4713   QualType T = Entity.getType();
4714
4715   //     -- if T is an array type, then each element is value-initialized;
4716   T = S.Context.getBaseElementType(T);
4717
4718   if (const RecordType *RT = T->getAs<RecordType>()) {
4719     if (CXXRecordDecl *ClassDecl = dyn_cast<CXXRecordDecl>(RT->getDecl())) {
4720       bool NeedZeroInitialization = true;
4721       // C++98:
4722       // -- if T is a class type (clause 9) with a user-declared constructor
4723       //    (12.1), then the default constructor for T is called (and the
4724       //    initialization is ill-formed if T has no accessible default
4725       //    constructor);
4726       // C++11:
4727       // -- if T is a class type (clause 9) with either no default constructor
4728       //    (12.1 [class.ctor]) or a default constructor that is user-provided
4729       //    or deleted, then the object is default-initialized;
4730       //
4731       // Note that the C++11 rule is the same as the C++98 rule if there are no
4732       // defaulted or deleted constructors, so we just use it unconditionally.
4733       CXXConstructorDecl *CD = S.LookupDefaultConstructor(ClassDecl);
4734       if (!CD || !CD->getCanonicalDecl()->isDefaulted() || CD->isDeleted())
4735         NeedZeroInitialization = false;
4736
4737       // -- if T is a (possibly cv-qualified) non-union class type without a
4738       //    user-provided or deleted default constructor, then the object is
4739       //    zero-initialized and, if T has a non-trivial default constructor,
4740       //    default-initialized;
4741       // The 'non-union' here was removed by DR1502. The 'non-trivial default
4742       // constructor' part was removed by DR1507.
4743       if (NeedZeroInitialization)
4744         Sequence.AddZeroInitializationStep(Entity.getType());
4745
4746       // C++03:
4747       // -- if T is a non-union class type without a user-declared constructor,
4748       //    then every non-static data member and base class component of T is
4749       //    value-initialized;
4750       // [...] A program that calls for [...] value-initialization of an
4751       // entity of reference type is ill-formed.
4752       //
4753       // C++11 doesn't need this handling, because value-initialization does not
4754       // occur recursively there, and the implicit default constructor is
4755       // defined as deleted in the problematic cases.
4756       if (!S.getLangOpts().CPlusPlus11 &&
4757           ClassDecl->hasUninitializedReferenceMember()) {
4758         Sequence.SetFailed(InitializationSequence::FK_TooManyInitsForReference);
4759         return;
4760       }
4761
4762       // If this is list-value-initialization, pass the empty init list on when
4763       // building the constructor call. This affects the semantics of a few
4764       // things (such as whether an explicit default constructor can be called).
4765       Expr *InitListAsExpr = InitList;
4766       MultiExprArg Args(&InitListAsExpr, InitList ? 1 : 0);
4767       bool InitListSyntax = InitList;
4768
4769       // FIXME: Instead of creating a CXXConstructExpr of array type here,
4770       // wrap a class-typed CXXConstructExpr in an ArrayInitLoopExpr.
4771       return TryConstructorInitialization(
4772           S, Entity, Kind, Args, T, Entity.getType(), Sequence, InitListSyntax);
4773     }
4774   }
4775
4776   Sequence.AddZeroInitializationStep(Entity.getType());
4777 }
4778
4779 /// Attempt default initialization (C++ [dcl.init]p6).
4780 static void TryDefaultInitialization(Sema &S,
4781                                      const InitializedEntity &Entity,
4782                                      const InitializationKind &Kind,
4783                                      InitializationSequence &Sequence) {
4784   assert(Kind.getKind() == InitializationKind::IK_Default);
4785
4786   // C++ [dcl.init]p6:
4787   //   To default-initialize an object of type T means:
4788   //     - if T is an array type, each element is default-initialized;
4789   QualType DestType = S.Context.getBaseElementType(Entity.getType());
4790
4791   //     - if T is a (possibly cv-qualified) class type (Clause 9), the default
4792   //       constructor for T is called (and the initialization is ill-formed if
4793   //       T has no accessible default constructor);
4794   if (DestType->isRecordType() && S.getLangOpts().CPlusPlus) {
4795     TryConstructorInitialization(S, Entity, Kind, None, DestType,
4796                                  Entity.getType(), Sequence);
4797     return;
4798   }
4799
4800   //     - otherwise, no initialization is performed.
4801
4802   //   If a program calls for the default initialization of an object of
4803   //   a const-qualified type T, T shall be a class type with a user-provided
4804   //   default constructor.
4805   if (DestType.isConstQualified() && S.getLangOpts().CPlusPlus) {
4806     if (!maybeRecoverWithZeroInitialization(S, Sequence, Entity))
4807       Sequence.SetFailed(InitializationSequence::FK_DefaultInitOfConst);
4808     return;
4809   }
4810
4811   // If the destination type has a lifetime property, zero-initialize it.
4812   if (DestType.getQualifiers().hasObjCLifetime()) {
4813     Sequence.AddZeroInitializationStep(Entity.getType());
4814     return;
4815   }
4816 }
4817
4818 /// Attempt a user-defined conversion between two types (C++ [dcl.init]),
4819 /// which enumerates all conversion functions and performs overload resolution
4820 /// to select the best.
4821 static void TryUserDefinedConversion(Sema &S,
4822                                      QualType DestType,
4823                                      const InitializationKind &Kind,
4824                                      Expr *Initializer,
4825                                      InitializationSequence &Sequence,
4826                                      bool TopLevelOfInitList) {
4827   assert(!DestType->isReferenceType() && "References are handled elsewhere");
4828   QualType SourceType = Initializer->getType();
4829   assert((DestType->isRecordType() || SourceType->isRecordType()) &&
4830          "Must have a class type to perform a user-defined conversion");
4831
4832   // Build the candidate set directly in the initialization sequence
4833   // structure, so that it will persist if we fail.
4834   OverloadCandidateSet &CandidateSet = Sequence.getFailedCandidateSet();
4835   CandidateSet.clear(OverloadCandidateSet::CSK_InitByUserDefinedConversion);
4836
4837   // Determine whether we are allowed to call explicit constructors or
4838   // explicit conversion operators.
4839   bool AllowExplicit = Kind.AllowExplicit();
4840
4841   if (const RecordType *DestRecordType = DestType->getAs<RecordType>()) {
4842     // The type we're converting to is a class type. Enumerate its constructors
4843     // to see if there is a suitable conversion.
4844     CXXRecordDecl *DestRecordDecl
4845       = cast<CXXRecordDecl>(DestRecordType->getDecl());
4846
4847     // Try to complete the type we're converting to.
4848     if (S.isCompleteType(Kind.getLocation(), DestType)) {
4849       for (NamedDecl *D : S.LookupConstructors(DestRecordDecl)) {
4850         auto Info = getConstructorInfo(D);
4851         if (!Info.Constructor)
4852           continue;
4853
4854         if (!Info.Constructor->isInvalidDecl() &&
4855             Info.Constructor->isConvertingConstructor(AllowExplicit)) {
4856           if (Info.ConstructorTmpl)
4857             S.AddTemplateOverloadCandidate(Info.ConstructorTmpl, Info.FoundDecl,
4858                                            /*ExplicitArgs*/ nullptr,
4859                                            Initializer, CandidateSet,
4860                                            /*SuppressUserConversions=*/true);
4861           else
4862             S.AddOverloadCandidate(Info.Constructor, Info.FoundDecl,
4863                                    Initializer, CandidateSet,
4864                                    /*SuppressUserConversions=*/true);
4865         }
4866       }
4867     }
4868   }
4869
4870   SourceLocation DeclLoc = Initializer->getLocStart();
4871
4872   if (const RecordType *SourceRecordType = SourceType->getAs<RecordType>()) {
4873     // The type we're converting from is a class type, enumerate its conversion
4874     // functions.
4875
4876     // We can only enumerate the conversion functions for a complete type; if
4877     // the type isn't complete, simply skip this step.
4878     if (S.isCompleteType(DeclLoc, SourceType)) {
4879       CXXRecordDecl *SourceRecordDecl
4880         = cast<CXXRecordDecl>(SourceRecordType->getDecl());
4881
4882       const auto &Conversions =
4883           SourceRecordDecl->getVisibleConversionFunctions();
4884       for (auto I = Conversions.begin(), E = Conversions.end(); I != E; ++I) {
4885         NamedDecl *D = *I;
4886         CXXRecordDecl *ActingDC = cast<CXXRecordDecl>(D->getDeclContext());
4887         if (isa<UsingShadowDecl>(D))
4888           D = cast<UsingShadowDecl>(D)->getTargetDecl();
4889
4890         FunctionTemplateDecl *ConvTemplate = dyn_cast<FunctionTemplateDecl>(D);
4891         CXXConversionDecl *Conv;
4892         if (ConvTemplate)
4893           Conv = cast<CXXConversionDecl>(ConvTemplate->getTemplatedDecl());
4894         else
4895           Conv = cast<CXXConversionDecl>(D);
4896
4897         if (AllowExplicit || !Conv->isExplicit()) {
4898           if (ConvTemplate)
4899             S.AddTemplateConversionCandidate(ConvTemplate, I.getPair(),
4900                                              ActingDC, Initializer, DestType,
4901                                              CandidateSet, AllowExplicit);
4902           else
4903             S.AddConversionCandidate(Conv, I.getPair(), ActingDC,
4904                                      Initializer, DestType, CandidateSet,
4905                                      AllowExplicit);
4906         }
4907       }
4908     }
4909   }
4910
4911   // Perform overload resolution. If it fails, return the failed result.
4912   OverloadCandidateSet::iterator Best;
4913   if (OverloadingResult Result
4914         = CandidateSet.BestViableFunction(S, DeclLoc, Best)) {
4915     Sequence.SetOverloadFailure(
4916                         InitializationSequence::FK_UserConversionOverloadFailed,
4917                                 Result);
4918     return;
4919   }
4920
4921   FunctionDecl *Function = Best->Function;
4922   Function->setReferenced();
4923   bool HadMultipleCandidates = (CandidateSet.size() > 1);
4924
4925   if (isa<CXXConstructorDecl>(Function)) {
4926     // Add the user-defined conversion step. Any cv-qualification conversion is
4927     // subsumed by the initialization. Per DR5, the created temporary is of the
4928     // cv-unqualified type of the destination.
4929     Sequence.AddUserConversionStep(Function, Best->FoundDecl,
4930                                    DestType.getUnqualifiedType(),
4931                                    HadMultipleCandidates);
4932
4933     // C++14 and before:
4934     //   - if the function is a constructor, the call initializes a temporary
4935     //     of the cv-unqualified version of the destination type. The [...]
4936     //     temporary [...] is then used to direct-initialize, according to the
4937     //     rules above, the object that is the destination of the
4938     //     copy-initialization.
4939     // Note that this just performs a simple object copy from the temporary.
4940     //
4941     // C++17:
4942     //   - if the function is a constructor, the call is a prvalue of the
4943     //     cv-unqualified version of the destination type whose return object
4944     //     is initialized by the constructor. The call is used to
4945     //     direct-initialize, according to the rules above, the object that
4946     //     is the destination of the copy-initialization.
4947     // Therefore we need to do nothing further.
4948     //
4949     // FIXME: Mark this copy as extraneous.
4950     if (!S.getLangOpts().CPlusPlus17)
4951       Sequence.AddFinalCopy(DestType);
4952     else if (DestType.hasQualifiers())
4953       Sequence.AddQualificationConversionStep(DestType, VK_RValue);
4954     return;
4955   }
4956
4957   // Add the user-defined conversion step that calls the conversion function.
4958   QualType ConvType = Function->getCallResultType();
4959   Sequence.AddUserConversionStep(Function, Best->FoundDecl, ConvType,
4960                                  HadMultipleCandidates);
4961
4962   if (ConvType->getAs<RecordType>()) {
4963     //   The call is used to direct-initialize [...] the object that is the
4964     //   destination of the copy-initialization.
4965     //
4966     // In C++17, this does not call a constructor if we enter /17.6.1:
4967     //   - If the initializer expression is a prvalue and the cv-unqualified
4968     //     version of the source type is the same as the class of the
4969     //     destination [... do not make an extra copy]
4970     //
4971     // FIXME: Mark this copy as extraneous.
4972     if (!S.getLangOpts().CPlusPlus17 ||
4973         Function->getReturnType()->isReferenceType() ||
4974         !S.Context.hasSameUnqualifiedType(ConvType, DestType))
4975       Sequence.AddFinalCopy(DestType);
4976     else if (!S.Context.hasSameType(ConvType, DestType))
4977       Sequence.AddQualificationConversionStep(DestType, VK_RValue);
4978     return;
4979   }
4980
4981   // If the conversion following the call to the conversion function
4982   // is interesting, add it as a separate step.
4983   if (Best->FinalConversion.First || Best->FinalConversion.Second ||
4984       Best->FinalConversion.Third) {
4985     ImplicitConversionSequence ICS;
4986     ICS.setStandard();
4987     ICS.Standard = Best->FinalConversion;
4988     Sequence.AddConversionSequenceStep(ICS, DestType, TopLevelOfInitList);
4989   }
4990 }
4991
4992 /// An egregious hack for compatibility with libstdc++-4.2: in <tr1/hashtable>,
4993 /// a function with a pointer return type contains a 'return false;' statement.
4994 /// In C++11, 'false' is not a null pointer, so this breaks the build of any
4995 /// code using that header.
4996 ///
4997 /// Work around this by treating 'return false;' as zero-initializing the result
4998 /// if it's used in a pointer-returning function in a system header.
4999 static bool isLibstdcxxPointerReturnFalseHack(Sema &S,
5000                                               const InitializedEntity &Entity,
5001                                               const Expr *Init) {
5002   return S.getLangOpts().CPlusPlus11 &&
5003          Entity.getKind() == InitializedEntity::EK_Result &&
5004          Entity.getType()->isPointerType() &&
5005          isa<CXXBoolLiteralExpr>(Init) &&
5006          !cast<CXXBoolLiteralExpr>(Init)->getValue() &&
5007          S.getSourceManager().isInSystemHeader(Init->getExprLoc());
5008 }
5009
5010 /// The non-zero enum values here are indexes into diagnostic alternatives.
5011 enum InvalidICRKind { IIK_okay, IIK_nonlocal, IIK_nonscalar };
5012
5013 /// Determines whether this expression is an acceptable ICR source.
5014 static InvalidICRKind isInvalidICRSource(ASTContext &C, Expr *e,
5015                                          bool isAddressOf, bool &isWeakAccess) {
5016   // Skip parens.
5017   e = e->IgnoreParens();
5018
5019   // Skip address-of nodes.
5020   if (UnaryOperator *op = dyn_cast<UnaryOperator>(e)) {
5021     if (op->getOpcode() == UO_AddrOf)
5022       return isInvalidICRSource(C, op->getSubExpr(), /*addressof*/ true,
5023                                 isWeakAccess);
5024
5025   // Skip certain casts.
5026   } else if (CastExpr *ce = dyn_cast<CastExpr>(e)) {
5027     switch (ce->getCastKind()) {
5028     case CK_Dependent:
5029     case CK_BitCast:
5030     case CK_LValueBitCast:
5031     case CK_NoOp:
5032       return isInvalidICRSource(C, ce->getSubExpr(), isAddressOf, isWeakAccess);
5033
5034     case CK_ArrayToPointerDecay:
5035       return IIK_nonscalar;
5036
5037     case CK_NullToPointer:
5038       return IIK_okay;
5039
5040     default:
5041       break;
5042     }
5043
5044   // If we have a declaration reference, it had better be a local variable.
5045   } else if (isa<DeclRefExpr>(e)) {
5046     // set isWeakAccess to true, to mean that there will be an implicit
5047     // load which requires a cleanup.
5048     if (e->getType().getObjCLifetime() == Qualifiers::OCL_Weak)
5049       isWeakAccess = true;
5050
5051     if (!isAddressOf) return IIK_nonlocal;
5052
5053     VarDecl *var = dyn_cast<VarDecl>(cast<DeclRefExpr>(e)->getDecl());
5054     if (!var) return IIK_nonlocal;
5055
5056     return (var->hasLocalStorage() ? IIK_okay : IIK_nonlocal);
5057
5058   // If we have a conditional operator, check both sides.
5059   } else if (ConditionalOperator *cond = dyn_cast<ConditionalOperator>(e)) {
5060     if (InvalidICRKind iik = isInvalidICRSource(C, cond->getLHS(), isAddressOf,
5061                                                 isWeakAccess))
5062       return iik;
5063
5064     return isInvalidICRSource(C, cond->getRHS(), isAddressOf, isWeakAccess);
5065
5066   // These are never scalar.
5067   } else if (isa<ArraySubscriptExpr>(e)) {
5068     return IIK_nonscalar;
5069
5070   // Otherwise, it needs to be a null pointer constant.
5071   } else {
5072     return (e->isNullPointerConstant(C, Expr::NPC_ValueDependentIsNull)
5073             ? IIK_okay : IIK_nonlocal);
5074   }
5075
5076   return IIK_nonlocal;
5077 }
5078
5079 /// Check whether the given expression is a valid operand for an
5080 /// indirect copy/restore.
5081 static void checkIndirectCopyRestoreSource(Sema &S, Expr *src) {
5082   assert(src->isRValue());
5083   bool isWeakAccess = false;
5084   InvalidICRKind iik = isInvalidICRSource(S.Context, src, false, isWeakAccess);
5085   // If isWeakAccess to true, there will be an implicit
5086   // load which requires a cleanup.
5087   if (S.getLangOpts().ObjCAutoRefCount && isWeakAccess)
5088     S.Cleanup.setExprNeedsCleanups(true);
5089
5090   if (iik == IIK_okay) return;
5091
5092   S.Diag(src->getExprLoc(), diag::err_arc_nonlocal_writeback)
5093     << ((unsigned) iik - 1)  // shift index into diagnostic explanations
5094     << src->getSourceRange();
5095 }
5096
5097 /// Determine whether we have compatible array types for the
5098 /// purposes of GNU by-copy array initialization.
5099 static bool hasCompatibleArrayTypes(ASTContext &Context, const ArrayType *Dest,
5100                                     const ArrayType *Source) {
5101   // If the source and destination array types are equivalent, we're
5102   // done.
5103   if (Context.hasSameType(QualType(Dest, 0), QualType(Source, 0)))
5104     return true;
5105
5106   // Make sure that the element types are the same.
5107   if (!Context.hasSameType(Dest->getElementType(), Source->getElementType()))
5108     return false;
5109
5110   // The only mismatch we allow is when the destination is an
5111   // incomplete array type and the source is a constant array type.
5112   return Source->isConstantArrayType() && Dest->isIncompleteArrayType();
5113 }
5114
5115 static bool tryObjCWritebackConversion(Sema &S,
5116                                        InitializationSequence &Sequence,
5117                                        const InitializedEntity &Entity,
5118                                        Expr *Initializer) {
5119   bool ArrayDecay = false;
5120   QualType ArgType = Initializer->getType();
5121   QualType ArgPointee;
5122   if (const ArrayType *ArgArrayType = S.Context.getAsArrayType(ArgType)) {
5123     ArrayDecay = true;
5124     ArgPointee = ArgArrayType->getElementType();
5125     ArgType = S.Context.getPointerType(ArgPointee);
5126   }
5127
5128   // Handle write-back conversion.
5129   QualType ConvertedArgType;
5130   if (!S.isObjCWritebackConversion(ArgType, Entity.getType(),
5131                                    ConvertedArgType))
5132     return false;
5133
5134   // We should copy unless we're passing to an argument explicitly
5135   // marked 'out'.
5136   bool ShouldCopy = true;
5137   if (ParmVarDecl *param = cast_or_null<ParmVarDecl>(Entity.getDecl()))
5138     ShouldCopy = (param->getObjCDeclQualifier() != ParmVarDecl::OBJC_TQ_Out);
5139
5140   // Do we need an lvalue conversion?
5141   if (ArrayDecay || Initializer->isGLValue()) {
5142     ImplicitConversionSequence ICS;
5143     ICS.setStandard();
5144     ICS.Standard.setAsIdentityConversion();
5145
5146     QualType ResultType;
5147     if (ArrayDecay) {
5148       ICS.Standard.First = ICK_Array_To_Pointer;
5149       ResultType = S.Context.getPointerType(ArgPointee);
5150     } else {
5151       ICS.Standard.First = ICK_Lvalue_To_Rvalue;
5152       ResultType = Initializer->getType().getNonLValueExprType(S.Context);
5153     }
5154
5155     Sequence.AddConversionSequenceStep(ICS, ResultType);
5156   }
5157
5158   Sequence.AddPassByIndirectCopyRestoreStep(Entity.getType(), ShouldCopy);
5159   return true;
5160 }
5161
5162 static bool TryOCLSamplerInitialization(Sema &S,
5163                                         InitializationSequence &Sequence,
5164                                         QualType DestType,
5165                                         Expr *Initializer) {
5166   if (!S.getLangOpts().OpenCL || !DestType->isSamplerT() ||
5167       (!Initializer->isIntegerConstantExpr(S.Context) &&
5168       !Initializer->getType()->isSamplerT()))
5169     return false;
5170
5171   Sequence.AddOCLSamplerInitStep(DestType);
5172   return true;
5173 }
5174
5175 //
5176 // OpenCL 1.2 spec, s6.12.10
5177 //
5178 // The event argument can also be used to associate the
5179 // async_work_group_copy with a previous async copy allowing
5180 // an event to be shared by multiple async copies; otherwise
5181 // event should be zero.
5182 //
5183 static bool TryOCLZeroEventInitialization(Sema &S,
5184                                           InitializationSequence &Sequence,
5185                                           QualType DestType,
5186                                           Expr *Initializer) {
5187   if (!S.getLangOpts().OpenCL || !DestType->isEventT() ||
5188       !Initializer->isIntegerConstantExpr(S.getASTContext()) ||
5189       (Initializer->EvaluateKnownConstInt(S.getASTContext()) != 0))
5190     return false;
5191
5192   Sequence.AddOCLZeroEventStep(DestType);
5193   return true;
5194 }
5195
5196 static bool TryOCLZeroQueueInitialization(Sema &S,
5197                                           InitializationSequence &Sequence,
5198                                           QualType DestType,
5199                                           Expr *Initializer) {
5200   if (!S.getLangOpts().OpenCL || S.getLangOpts().OpenCLVersion < 200 ||
5201       !DestType->isQueueT() ||
5202       !Initializer->isIntegerConstantExpr(S.getASTContext()) ||
5203       (Initializer->EvaluateKnownConstInt(S.getASTContext()) != 0))
5204     return false;
5205
5206   Sequence.AddOCLZeroQueueStep(DestType);
5207   return true;
5208 }
5209
5210 InitializationSequence::InitializationSequence(Sema &S,
5211                                                const InitializedEntity &Entity,
5212                                                const InitializationKind &Kind,
5213                                                MultiExprArg Args,
5214                                                bool TopLevelOfInitList,
5215                                                bool TreatUnavailableAsInvalid)
5216     : FailedCandidateSet(Kind.getLocation(), OverloadCandidateSet::CSK_Normal) {
5217   InitializeFrom(S, Entity, Kind, Args, TopLevelOfInitList,
5218                  TreatUnavailableAsInvalid);
5219 }
5220
5221 /// Tries to get a FunctionDecl out of `E`. If it succeeds and we can take the
5222 /// address of that function, this returns true. Otherwise, it returns false.
5223 static bool isExprAnUnaddressableFunction(Sema &S, const Expr *E) {
5224   auto *DRE = dyn_cast<DeclRefExpr>(E);
5225   if (!DRE || !isa<FunctionDecl>(DRE->getDecl()))
5226     return false;
5227
5228   return !S.checkAddressOfFunctionIsAvailable(
5229       cast<FunctionDecl>(DRE->getDecl()));
5230 }
5231
5232 /// Determine whether we can perform an elementwise array copy for this kind
5233 /// of entity.
5234 static bool canPerformArrayCopy(const InitializedEntity &Entity) {
5235   switch (Entity.getKind()) {
5236   case InitializedEntity::EK_LambdaCapture:
5237     // C++ [expr.prim.lambda]p24:
5238     //   For array members, the array elements are direct-initialized in
5239     //   increasing subscript order.
5240     return true;
5241
5242   case InitializedEntity::EK_Variable:
5243     // C++ [dcl.decomp]p1:
5244     //   [...] each element is copy-initialized or direct-initialized from the
5245     //   corresponding element of the assignment-expression [...]
5246     return isa<DecompositionDecl>(Entity.getDecl());
5247
5248   case InitializedEntity::EK_Member:
5249     // C++ [class.copy.ctor]p14:
5250     //   - if the member is an array, each element is direct-initialized with
5251     //     the corresponding subobject of x
5252     return Entity.isImplicitMemberInitializer();
5253
5254   case InitializedEntity::EK_ArrayElement:
5255     // All the above cases are intended to apply recursively, even though none
5256     // of them actually say that.
5257     if (auto *E = Entity.getParent())
5258       return canPerformArrayCopy(*E);
5259     break;
5260
5261   default:
5262     break;
5263   }
5264
5265   return false;
5266 }
5267
5268 void InitializationSequence::InitializeFrom(Sema &S,
5269                                             const InitializedEntity &Entity,
5270                                             const InitializationKind &Kind,
5271                                             MultiExprArg Args,
5272                                             bool TopLevelOfInitList,
5273                                             bool TreatUnavailableAsInvalid) {
5274   ASTContext &Context = S.Context;
5275
5276   // Eliminate non-overload placeholder types in the arguments.  We
5277   // need to do this before checking whether types are dependent
5278   // because lowering a pseudo-object expression might well give us
5279   // something of dependent type.
5280   for (unsigned I = 0, E = Args.size(); I != E; ++I)
5281     if (Args[I]->getType()->isNonOverloadPlaceholderType()) {
5282       // FIXME: should we be doing this here?
5283       ExprResult result = S.CheckPlaceholderExpr(Args[I]);
5284       if (result.isInvalid()) {
5285         SetFailed(FK_PlaceholderType);
5286         return;
5287       }
5288       Args[I] = result.get();
5289     }
5290
5291   // C++0x [dcl.init]p16:
5292   //   The semantics of initializers are as follows. The destination type is
5293   //   the type of the object or reference being initialized and the source
5294   //   type is the type of the initializer expression. The source type is not
5295   //   defined when the initializer is a braced-init-list or when it is a
5296   //   parenthesized list of expressions.
5297   QualType DestType = Entity.getType();
5298
5299   if (DestType->isDependentType() ||
5300       Expr::hasAnyTypeDependentArguments(Args)) {
5301     SequenceKind = DependentSequence;
5302     return;
5303   }
5304
5305   // Almost everything is a normal sequence.
5306   setSequenceKind(NormalSequence);
5307
5308   QualType SourceType;
5309   Expr *Initializer = nullptr;
5310   if (Args.size() == 1) {
5311     Initializer = Args[0];
5312     if (S.getLangOpts().ObjC1) {
5313       if (S.CheckObjCBridgeRelatedConversions(Initializer->getLocStart(),
5314                                               DestType, Initializer->getType(),
5315                                               Initializer) ||
5316           S.ConversionToObjCStringLiteralCheck(DestType, Initializer))
5317         Args[0] = Initializer;
5318     }
5319     if (!isa<InitListExpr>(Initializer))
5320       SourceType = Initializer->getType();
5321   }
5322
5323   //     - If the initializer is a (non-parenthesized) braced-init-list, the
5324   //       object is list-initialized (8.5.4).
5325   if (Kind.getKind() != InitializationKind::IK_Direct) {
5326     if (InitListExpr *InitList = dyn_cast_or_null<InitListExpr>(Initializer)) {
5327       TryListInitialization(S, Entity, Kind, InitList, *this,
5328                             TreatUnavailableAsInvalid);
5329       return;
5330     }
5331   }
5332
5333   //     - If the destination type is a reference type, see 8.5.3.
5334   if (DestType->isReferenceType()) {
5335     // C++0x [dcl.init.ref]p1:
5336     //   A variable declared to be a T& or T&&, that is, "reference to type T"
5337     //   (8.3.2), shall be initialized by an object, or function, of type T or
5338     //   by an object that can be converted into a T.
5339     // (Therefore, multiple arguments are not permitted.)
5340     if (Args.size() != 1)
5341       SetFailed(FK_TooManyInitsForReference);
5342     // C++17 [dcl.init.ref]p5:
5343     //   A reference [...] is initialized by an expression [...] as follows:
5344     // If the initializer is not an expression, presumably we should reject,
5345     // but the standard fails to actually say so.
5346     else if (isa<InitListExpr>(Args[0]))
5347       SetFailed(FK_ParenthesizedListInitForReference);
5348     else
5349       TryReferenceInitialization(S, Entity, Kind, Args[0], *this);
5350     return;
5351   }
5352
5353   //     - If the initializer is (), the object is value-initialized.
5354   if (Kind.getKind() == InitializationKind::IK_Value ||
5355       (Kind.getKind() == InitializationKind::IK_Direct && Args.empty())) {
5356     TryValueInitialization(S, Entity, Kind, *this);
5357     return;
5358   }
5359
5360   // Handle default initialization.
5361   if (Kind.getKind() == InitializationKind::IK_Default) {
5362     TryDefaultInitialization(S, Entity, Kind, *this);
5363     return;
5364   }
5365
5366   //     - If the destination type is an array of characters, an array of
5367   //       char16_t, an array of char32_t, or an array of wchar_t, and the
5368   //       initializer is a string literal, see 8.5.2.
5369   //     - Otherwise, if the destination type is an array, the program is
5370   //       ill-formed.
5371   if (const ArrayType *DestAT = Context.getAsArrayType(DestType)) {
5372     if (Initializer && isa<VariableArrayType>(DestAT)) {
5373       SetFailed(FK_VariableLengthArrayHasInitializer);
5374       return;
5375     }
5376
5377     if (Initializer) {
5378       switch (IsStringInit(Initializer, DestAT, Context)) {
5379       case SIF_None:
5380         TryStringLiteralInitialization(S, Entity, Kind, Initializer, *this);
5381         return;
5382       case SIF_NarrowStringIntoWideChar:
5383         SetFailed(FK_NarrowStringIntoWideCharArray);
5384         return;
5385       case SIF_WideStringIntoChar:
5386         SetFailed(FK_WideStringIntoCharArray);
5387         return;
5388       case SIF_IncompatWideStringIntoWideChar:
5389         SetFailed(FK_IncompatWideStringIntoWideChar);
5390         return;
5391       case SIF_PlainStringIntoUTF8Char:
5392         SetFailed(FK_PlainStringIntoUTF8Char);
5393         return;
5394       case SIF_UTF8StringIntoPlainChar:
5395         SetFailed(FK_UTF8StringIntoPlainChar);
5396         return;
5397       case SIF_Other:
5398         break;
5399       }
5400     }
5401
5402     // Some kinds of initialization permit an array to be initialized from
5403     // another array of the same type, and perform elementwise initialization.
5404     if (Initializer && isa<ConstantArrayType>(DestAT) &&
5405         S.Context.hasSameUnqualifiedType(Initializer->getType(),
5406                                          Entity.getType()) &&
5407         canPerformArrayCopy(Entity)) {
5408       // If source is a prvalue, use it directly.
5409       if (Initializer->getValueKind() == VK_RValue) {
5410         AddArrayInitStep(DestType, /*IsGNUExtension*/false);
5411         return;
5412       }
5413
5414       // Emit element-at-a-time copy loop.
5415       InitializedEntity Element =
5416           InitializedEntity::InitializeElement(S.Context, 0, Entity);
5417       QualType InitEltT =
5418           Context.getAsArrayType(Initializer->getType())->getElementType();
5419       OpaqueValueExpr OVE(Initializer->getExprLoc(), InitEltT,
5420                           Initializer->getValueKind(),
5421                           Initializer->getObjectKind());
5422       Expr *OVEAsExpr = &OVE;
5423       InitializeFrom(S, Element, Kind, OVEAsExpr, TopLevelOfInitList,
5424                      TreatUnavailableAsInvalid);
5425       if (!Failed())
5426         AddArrayInitLoopStep(Entity.getType(), InitEltT);
5427       return;
5428     }
5429
5430     // Note: as an GNU C extension, we allow initialization of an
5431     // array from a compound literal that creates an array of the same
5432     // type, so long as the initializer has no side effects.
5433     if (!S.getLangOpts().CPlusPlus && Initializer &&
5434         isa<CompoundLiteralExpr>(Initializer->IgnoreParens()) &&
5435         Initializer->getType()->isArrayType()) {
5436       const ArrayType *SourceAT
5437         = Context.getAsArrayType(Initializer->getType());
5438       if (!hasCompatibleArrayTypes(S.Context, DestAT, SourceAT))
5439         SetFailed(FK_ArrayTypeMismatch);
5440       else if (Initializer->HasSideEffects(S.Context))
5441         SetFailed(FK_NonConstantArrayInit);
5442       else {
5443         AddArrayInitStep(DestType, /*IsGNUExtension*/true);
5444       }
5445     }
5446     // Note: as a GNU C++ extension, we allow list-initialization of a
5447     // class member of array type from a parenthesized initializer list.
5448     else if (S.getLangOpts().CPlusPlus &&
5449              Entity.getKind() == InitializedEntity::EK_Member &&
5450              Initializer && isa<InitListExpr>(Initializer)) {
5451       TryListInitialization(S, Entity, Kind, cast<InitListExpr>(Initializer),
5452                             *this, TreatUnavailableAsInvalid);
5453       AddParenthesizedArrayInitStep(DestType);
5454     } else if (DestAT->getElementType()->isCharType())
5455       SetFailed(FK_ArrayNeedsInitListOrStringLiteral);
5456     else if (IsWideCharCompatible(DestAT->getElementType(), Context))
5457       SetFailed(FK_ArrayNeedsInitListOrWideStringLiteral);
5458     else
5459       SetFailed(FK_ArrayNeedsInitList);
5460
5461     return;
5462   }
5463
5464   // Determine whether we should consider writeback conversions for
5465   // Objective-C ARC.
5466   bool allowObjCWritebackConversion = S.getLangOpts().ObjCAutoRefCount &&
5467          Entity.isParameterKind();
5468
5469   // We're at the end of the line for C: it's either a write-back conversion
5470   // or it's a C assignment. There's no need to check anything else.
5471   if (!S.getLangOpts().CPlusPlus) {
5472     // If allowed, check whether this is an Objective-C writeback conversion.
5473     if (allowObjCWritebackConversion &&
5474         tryObjCWritebackConversion(S, *this, Entity, Initializer)) {
5475       return;
5476     }
5477
5478     if (TryOCLSamplerInitialization(S, *this, DestType, Initializer))
5479       return;
5480
5481     if (TryOCLZeroEventInitialization(S, *this, DestType, Initializer))
5482       return;
5483
5484     if (TryOCLZeroQueueInitialization(S, *this, DestType, Initializer))
5485        return;
5486
5487     // Handle initialization in C
5488     AddCAssignmentStep(DestType);
5489     MaybeProduceObjCObject(S, *this, Entity);
5490     return;
5491   }
5492
5493   assert(S.getLangOpts().CPlusPlus);
5494
5495   //     - If the destination type is a (possibly cv-qualified) class type:
5496   if (DestType->isRecordType()) {
5497     //     - If the initialization is direct-initialization, or if it is
5498     //       copy-initialization where the cv-unqualified version of the
5499     //       source type is the same class as, or a derived class of, the
5500     //       class of the destination, constructors are considered. [...]
5501     if (Kind.getKind() == InitializationKind::IK_Direct ||
5502         (Kind.getKind() == InitializationKind::IK_Copy &&
5503          (Context.hasSameUnqualifiedType(SourceType, DestType) ||
5504           S.IsDerivedFrom(Initializer->getLocStart(), SourceType, DestType))))
5505       TryConstructorInitialization(S, Entity, Kind, Args,
5506                                    DestType, DestType, *this);
5507     //     - Otherwise (i.e., for the remaining copy-initialization cases),
5508     //       user-defined conversion sequences that can convert from the source
5509     //       type to the destination type or (when a conversion function is
5510     //       used) to a derived class thereof are enumerated as described in
5511     //       13.3.1.4, and the best one is chosen through overload resolution
5512     //       (13.3).
5513     else
5514       TryUserDefinedConversion(S, DestType, Kind, Initializer, *this,
5515                                TopLevelOfInitList);
5516     return;
5517   }
5518
5519   assert(Args.size() >= 1 && "Zero-argument case handled above");
5520
5521   // The remaining cases all need a source type.
5522   if (Args.size() > 1) {
5523     SetFailed(FK_TooManyInitsForScalar);
5524     return;
5525   } else if (isa<InitListExpr>(Args[0])) {
5526     SetFailed(FK_ParenthesizedListInitForScalar);
5527     return;
5528   }
5529
5530   //    - Otherwise, if the source type is a (possibly cv-qualified) class
5531   //      type, conversion functions are considered.
5532   if (!SourceType.isNull() && SourceType->isRecordType()) {
5533     // For a conversion to _Atomic(T) from either T or a class type derived
5534     // from T, initialize the T object then convert to _Atomic type.
5535     bool NeedAtomicConversion = false;
5536     if (const AtomicType *Atomic = DestType->getAs<AtomicType>()) {
5537       if (Context.hasSameUnqualifiedType(SourceType, Atomic->getValueType()) ||
5538           S.IsDerivedFrom(Initializer->getLocStart(), SourceType,
5539                           Atomic->getValueType())) {
5540         DestType = Atomic->getValueType();
5541         NeedAtomicConversion = true;
5542       }
5543     }
5544
5545     TryUserDefinedConversion(S, DestType, Kind, Initializer, *this,
5546                              TopLevelOfInitList);
5547     MaybeProduceObjCObject(S, *this, Entity);
5548     if (!Failed() && NeedAtomicConversion)
5549       AddAtomicConversionStep(Entity.getType());
5550     return;
5551   }
5552
5553   //    - Otherwise, the initial value of the object being initialized is the
5554   //      (possibly converted) value of the initializer expression. Standard
5555   //      conversions (Clause 4) will be used, if necessary, to convert the
5556   //      initializer expression to the cv-unqualified version of the
5557   //      destination type; no user-defined conversions are considered.
5558
5559   ImplicitConversionSequence ICS
5560     = S.TryImplicitConversion(Initializer, DestType,
5561                               /*SuppressUserConversions*/true,
5562                               /*AllowExplicitConversions*/ false,
5563                               /*InOverloadResolution*/ false,
5564                               /*CStyle=*/Kind.isCStyleOrFunctionalCast(),
5565                               allowObjCWritebackConversion);
5566
5567   if (ICS.isStandard() &&
5568       ICS.Standard.Second == ICK_Writeback_Conversion) {
5569     // Objective-C ARC writeback conversion.
5570
5571     // We should copy unless we're passing to an argument explicitly
5572     // marked 'out'.
5573     bool ShouldCopy = true;
5574     if (ParmVarDecl *Param = cast_or_null<ParmVarDecl>(Entity.getDecl()))
5575       ShouldCopy = (Param->getObjCDeclQualifier() != ParmVarDecl::OBJC_TQ_Out);
5576
5577     // If there was an lvalue adjustment, add it as a separate conversion.
5578     if (ICS.Standard.First == ICK_Array_To_Pointer ||
5579         ICS.Standard.First == ICK_Lvalue_To_Rvalue) {
5580       ImplicitConversionSequence LvalueICS;
5581       LvalueICS.setStandard();
5582       LvalueICS.Standard.setAsIdentityConversion();
5583       LvalueICS.Standard.setAllToTypes(ICS.Standard.getToType(0));
5584       LvalueICS.Standard.First = ICS.Standard.First;
5585       AddConversionSequenceStep(LvalueICS, ICS.Standard.getToType(0));
5586     }
5587
5588     AddPassByIndirectCopyRestoreStep(DestType, ShouldCopy);
5589   } else if (ICS.isBad()) {
5590     DeclAccessPair dap;
5591     if (isLibstdcxxPointerReturnFalseHack(S, Entity, Initializer)) {
5592       AddZeroInitializationStep(Entity.getType());
5593     } else if (Initializer->getType() == Context.OverloadTy &&
5594                !S.ResolveAddressOfOverloadedFunction(Initializer, DestType,
5595                                                      false, dap))
5596       SetFailed(InitializationSequence::FK_AddressOfOverloadFailed);
5597     else if (Initializer->getType()->isFunctionType() &&
5598              isExprAnUnaddressableFunction(S, Initializer))
5599       SetFailed(InitializationSequence::FK_AddressOfUnaddressableFunction);
5600     else
5601       SetFailed(InitializationSequence::FK_ConversionFailed);
5602   } else {
5603     AddConversionSequenceStep(ICS, DestType, TopLevelOfInitList);
5604
5605     MaybeProduceObjCObject(S, *this, Entity);
5606   }
5607 }
5608
5609 InitializationSequence::~InitializationSequence() {
5610   for (auto &S : Steps)
5611     S.Destroy();
5612 }
5613
5614 //===----------------------------------------------------------------------===//
5615 // Perform initialization
5616 //===----------------------------------------------------------------------===//
5617 static Sema::AssignmentAction
5618 getAssignmentAction(const InitializedEntity &Entity, bool Diagnose = false) {
5619   switch(Entity.getKind()) {
5620   case InitializedEntity::EK_Variable:
5621   case InitializedEntity::EK_New:
5622   case InitializedEntity::EK_Exception:
5623   case InitializedEntity::EK_Base:
5624   case InitializedEntity::EK_Delegating:
5625     return Sema::AA_Initializing;
5626
5627   case InitializedEntity::EK_Parameter:
5628     if (Entity.getDecl() &&
5629         isa<ObjCMethodDecl>(Entity.getDecl()->getDeclContext()))
5630       return Sema::AA_Sending;
5631
5632     return Sema::AA_Passing;
5633
5634   case InitializedEntity::EK_Parameter_CF_Audited:
5635     if (Entity.getDecl() &&
5636       isa<ObjCMethodDecl>(Entity.getDecl()->getDeclContext()))
5637       return Sema::AA_Sending;
5638
5639     return !Diagnose ? Sema::AA_Passing : Sema::AA_Passing_CFAudited;
5640
5641   case InitializedEntity::EK_Result:
5642   case InitializedEntity::EK_StmtExprResult: // FIXME: Not quite right.
5643     return Sema::AA_Returning;
5644
5645   case InitializedEntity::EK_Temporary:
5646   case InitializedEntity::EK_RelatedResult:
5647     // FIXME: Can we tell apart casting vs. converting?
5648     return Sema::AA_Casting;
5649
5650   case InitializedEntity::EK_Member:
5651   case InitializedEntity::EK_Binding:
5652   case InitializedEntity::EK_ArrayElement:
5653   case InitializedEntity::EK_VectorElement:
5654   case InitializedEntity::EK_ComplexElement:
5655   case InitializedEntity::EK_BlockElement:
5656   case InitializedEntity::EK_LambdaToBlockConversionBlockElement:
5657   case InitializedEntity::EK_LambdaCapture:
5658   case InitializedEntity::EK_CompoundLiteralInit:
5659     return Sema::AA_Initializing;
5660   }
5661
5662   llvm_unreachable("Invalid EntityKind!");
5663 }
5664
5665 /// Whether we should bind a created object as a temporary when
5666 /// initializing the given entity.
5667 static bool shouldBindAsTemporary(const InitializedEntity &Entity) {
5668   switch (Entity.getKind()) {
5669   case InitializedEntity::EK_ArrayElement:
5670   case InitializedEntity::EK_Member:
5671   case InitializedEntity::EK_Result:
5672   case InitializedEntity::EK_StmtExprResult:
5673   case InitializedEntity::EK_New:
5674   case InitializedEntity::EK_Variable:
5675   case InitializedEntity::EK_Base:
5676   case InitializedEntity::EK_Delegating:
5677   case InitializedEntity::EK_VectorElement:
5678   case InitializedEntity::EK_ComplexElement:
5679   case InitializedEntity::EK_Exception:
5680   case InitializedEntity::EK_BlockElement:
5681   case InitializedEntity::EK_LambdaToBlockConversionBlockElement:
5682   case InitializedEntity::EK_LambdaCapture:
5683   case InitializedEntity::EK_CompoundLiteralInit:
5684     return false;
5685
5686   case InitializedEntity::EK_Parameter:
5687   case InitializedEntity::EK_Parameter_CF_Audited:
5688   case InitializedEntity::EK_Temporary:
5689   case InitializedEntity::EK_RelatedResult:
5690   case InitializedEntity::EK_Binding:
5691     return true;
5692   }
5693
5694   llvm_unreachable("missed an InitializedEntity kind?");
5695 }
5696
5697 /// Whether the given entity, when initialized with an object
5698 /// created for that initialization, requires destruction.
5699 static bool shouldDestroyEntity(const InitializedEntity &Entity) {
5700   switch (Entity.getKind()) {
5701     case InitializedEntity::EK_Result:
5702     case InitializedEntity::EK_StmtExprResult:
5703     case InitializedEntity::EK_New:
5704     case InitializedEntity::EK_Base:
5705     case InitializedEntity::EK_Delegating:
5706     case InitializedEntity::EK_VectorElement:
5707     case InitializedEntity::EK_ComplexElement:
5708     case InitializedEntity::EK_BlockElement:
5709     case InitializedEntity::EK_LambdaToBlockConversionBlockElement:
5710     case InitializedEntity::EK_LambdaCapture:
5711       return false;
5712
5713     case InitializedEntity::EK_Member:
5714     case InitializedEntity::EK_Binding:
5715     case InitializedEntity::EK_Variable:
5716     case InitializedEntity::EK_Parameter:
5717     case InitializedEntity::EK_Parameter_CF_Audited:
5718     case InitializedEntity::EK_Temporary:
5719     case InitializedEntity::EK_ArrayElement:
5720     case InitializedEntity::EK_Exception:
5721     case InitializedEntity::EK_CompoundLiteralInit:
5722     case InitializedEntity::EK_RelatedResult:
5723       return true;
5724   }
5725
5726   llvm_unreachable("missed an InitializedEntity kind?");
5727 }
5728
5729 /// Get the location at which initialization diagnostics should appear.
5730 static SourceLocation getInitializationLoc(const InitializedEntity &Entity,
5731                                            Expr *Initializer) {
5732   switch (Entity.getKind()) {
5733   case InitializedEntity::EK_Result:
5734   case InitializedEntity::EK_StmtExprResult:
5735     return Entity.getReturnLoc();
5736
5737   case InitializedEntity::EK_Exception:
5738     return Entity.getThrowLoc();
5739
5740   case InitializedEntity::EK_Variable:
5741   case InitializedEntity::EK_Binding:
5742     return Entity.getDecl()->getLocation();
5743
5744   case InitializedEntity::EK_LambdaCapture:
5745     return Entity.getCaptureLoc();
5746
5747   case InitializedEntity::EK_ArrayElement:
5748   case InitializedEntity::EK_Member:
5749   case InitializedEntity::EK_Parameter:
5750   case InitializedEntity::EK_Parameter_CF_Audited:
5751   case InitializedEntity::EK_Temporary:
5752   case InitializedEntity::EK_New:
5753   case InitializedEntity::EK_Base:
5754   case InitializedEntity::EK_Delegating:
5755   case InitializedEntity::EK_VectorElement:
5756   case InitializedEntity::EK_ComplexElement:
5757   case InitializedEntity::EK_BlockElement:
5758   case InitializedEntity::EK_LambdaToBlockConversionBlockElement:
5759   case InitializedEntity::EK_CompoundLiteralInit:
5760   case InitializedEntity::EK_RelatedResult:
5761     return Initializer->getLocStart();
5762   }
5763   llvm_unreachable("missed an InitializedEntity kind?");
5764 }
5765
5766 /// Make a (potentially elidable) temporary copy of the object
5767 /// provided by the given initializer by calling the appropriate copy
5768 /// constructor.
5769 ///
5770 /// \param S The Sema object used for type-checking.
5771 ///
5772 /// \param T The type of the temporary object, which must either be
5773 /// the type of the initializer expression or a superclass thereof.
5774 ///
5775 /// \param Entity The entity being initialized.
5776 ///
5777 /// \param CurInit The initializer expression.
5778 ///
5779 /// \param IsExtraneousCopy Whether this is an "extraneous" copy that
5780 /// is permitted in C++03 (but not C++0x) when binding a reference to
5781 /// an rvalue.
5782 ///
5783 /// \returns An expression that copies the initializer expression into
5784 /// a temporary object, or an error expression if a copy could not be
5785 /// created.
5786 static ExprResult CopyObject(Sema &S,
5787                              QualType T,
5788                              const InitializedEntity &Entity,
5789                              ExprResult CurInit,
5790                              bool IsExtraneousCopy) {
5791   if (CurInit.isInvalid())
5792     return CurInit;
5793   // Determine which class type we're copying to.
5794   Expr *CurInitExpr = (Expr *)CurInit.get();
5795   CXXRecordDecl *Class = nullptr;
5796   if (const RecordType *Record = T->getAs<RecordType>())
5797     Class = cast<CXXRecordDecl>(Record->getDecl());
5798   if (!Class)
5799     return CurInit;
5800
5801   SourceLocation Loc = getInitializationLoc(Entity, CurInit.get());
5802
5803   // Make sure that the type we are copying is complete.
5804   if (S.RequireCompleteType(Loc, T, diag::err_temp_copy_incomplete))
5805     return CurInit;
5806
5807   // Perform overload resolution using the class's constructors. Per
5808   // C++11 [dcl.init]p16, second bullet for class types, this initialization
5809   // is direct-initialization.
5810   OverloadCandidateSet CandidateSet(Loc, OverloadCandidateSet::CSK_Normal);
5811   DeclContext::lookup_result Ctors = S.LookupConstructors(Class);
5812
5813   OverloadCandidateSet::iterator Best;
5814   switch (ResolveConstructorOverload(
5815       S, Loc, CurInitExpr, CandidateSet, T, Ctors, Best,
5816       /*CopyInitializing=*/false, /*AllowExplicit=*/true,
5817       /*OnlyListConstructors=*/false, /*IsListInit=*/false,
5818       /*SecondStepOfCopyInit=*/true)) {
5819   case OR_Success:
5820     break;
5821
5822   case OR_No_Viable_Function:
5823     S.Diag(Loc, IsExtraneousCopy && !S.isSFINAEContext()
5824            ? diag::ext_rvalue_to_reference_temp_copy_no_viable
5825            : diag::err_temp_copy_no_viable)
5826       << (int)Entity.getKind() << CurInitExpr->getType()
5827       << CurInitExpr->getSourceRange();
5828     CandidateSet.NoteCandidates(S, OCD_AllCandidates, CurInitExpr);
5829     if (!IsExtraneousCopy || S.isSFINAEContext())
5830       return ExprError();
5831     return CurInit;
5832
5833   case OR_Ambiguous:
5834     S.Diag(Loc, diag::err_temp_copy_ambiguous)
5835       << (int)Entity.getKind() << CurInitExpr->getType()
5836       << CurInitExpr->getSourceRange();
5837     CandidateSet.NoteCandidates(S, OCD_ViableCandidates, CurInitExpr);
5838     return ExprError();
5839
5840   case OR_Deleted:
5841     S.Diag(Loc, diag::err_temp_copy_deleted)
5842       << (int)Entity.getKind() << CurInitExpr->getType()
5843       << CurInitExpr->getSourceRange();
5844     S.NoteDeletedFunction(Best->Function);
5845     return ExprError();
5846   }
5847
5848   bool HadMultipleCandidates = CandidateSet.size() > 1;
5849
5850   CXXConstructorDecl *Constructor = cast<CXXConstructorDecl>(Best->Function);
5851   SmallVector<Expr*, 8> ConstructorArgs;
5852   CurInit.get(); // Ownership transferred into MultiExprArg, below.
5853
5854   S.CheckConstructorAccess(Loc, Constructor, Best->FoundDecl, Entity,
5855                            IsExtraneousCopy);
5856
5857   if (IsExtraneousCopy) {
5858     // If this is a totally extraneous copy for C++03 reference
5859     // binding purposes, just return the original initialization
5860     // expression. We don't generate an (elided) copy operation here
5861     // because doing so would require us to pass down a flag to avoid
5862     // infinite recursion, where each step adds another extraneous,
5863     // elidable copy.
5864
5865     // Instantiate the default arguments of any extra parameters in
5866     // the selected copy constructor, as if we were going to create a
5867     // proper call to the copy constructor.
5868     for (unsigned I = 1, N = Constructor->getNumParams(); I != N; ++I) {
5869       ParmVarDecl *Parm = Constructor->getParamDecl(I);
5870       if (S.RequireCompleteType(Loc, Parm->getType(),
5871                                 diag::err_call_incomplete_argument))
5872         break;
5873
5874       // Build the default argument expression; we don't actually care
5875       // if this succeeds or not, because this routine will complain
5876       // if there was a problem.
5877       S.BuildCXXDefaultArgExpr(Loc, Constructor, Parm);
5878     }
5879
5880     return CurInitExpr;
5881   }
5882
5883   // Determine the arguments required to actually perform the
5884   // constructor call (we might have derived-to-base conversions, or
5885   // the copy constructor may have default arguments).
5886   if (S.CompleteConstructorCall(Constructor, CurInitExpr, Loc, ConstructorArgs))
5887     return ExprError();
5888
5889   // C++0x [class.copy]p32:
5890   //   When certain criteria are met, an implementation is allowed to
5891   //   omit the copy/move construction of a class object, even if the
5892   //   copy/move constructor and/or destructor for the object have
5893   //   side effects. [...]
5894   //     - when a temporary class object that has not been bound to a
5895   //       reference (12.2) would be copied/moved to a class object
5896   //       with the same cv-unqualified type, the copy/move operation
5897   //       can be omitted by constructing the temporary object
5898   //       directly into the target of the omitted copy/move
5899   //
5900   // Note that the other three bullets are handled elsewhere. Copy
5901   // elision for return statements and throw expressions are handled as part
5902   // of constructor initialization, while copy elision for exception handlers
5903   // is handled by the run-time.
5904   //
5905   // FIXME: If the function parameter is not the same type as the temporary, we
5906   // should still be able to elide the copy, but we don't have a way to
5907   // represent in the AST how much should be elided in this case.
5908   bool Elidable =
5909       CurInitExpr->isTemporaryObject(S.Context, Class) &&
5910       S.Context.hasSameUnqualifiedType(
5911           Best->Function->getParamDecl(0)->getType().getNonReferenceType(),
5912           CurInitExpr->getType());
5913
5914   // Actually perform the constructor call.
5915   CurInit = S.BuildCXXConstructExpr(Loc, T, Best->FoundDecl, Constructor,
5916                                     Elidable,
5917                                     ConstructorArgs,
5918                                     HadMultipleCandidates,
5919                                     /*ListInit*/ false,
5920                                     /*StdInitListInit*/ false,
5921                                     /*ZeroInit*/ false,
5922                                     CXXConstructExpr::CK_Complete,
5923                                     SourceRange());
5924
5925   // If we're supposed to bind temporaries, do so.
5926   if (!CurInit.isInvalid() && shouldBindAsTemporary(Entity))
5927     CurInit = S.MaybeBindToTemporary(CurInit.getAs<Expr>());
5928   return CurInit;
5929 }
5930
5931 /// Check whether elidable copy construction for binding a reference to
5932 /// a temporary would have succeeded if we were building in C++98 mode, for
5933 /// -Wc++98-compat.
5934 static void CheckCXX98CompatAccessibleCopy(Sema &S,
5935                                            const InitializedEntity &Entity,
5936                                            Expr *CurInitExpr) {
5937   assert(S.getLangOpts().CPlusPlus11);
5938
5939   const RecordType *Record = CurInitExpr->getType()->getAs<RecordType>();
5940   if (!Record)
5941     return;
5942
5943   SourceLocation Loc = getInitializationLoc(Entity, CurInitExpr);
5944   if (S.Diags.isIgnored(diag::warn_cxx98_compat_temp_copy, Loc))
5945     return;
5946
5947   // Find constructors which would have been considered.
5948   OverloadCandidateSet CandidateSet(Loc, OverloadCandidateSet::CSK_Normal);
5949   DeclContext::lookup_result Ctors =
5950       S.LookupConstructors(cast<CXXRecordDecl>(Record->getDecl()));
5951
5952   // Perform overload resolution.
5953   OverloadCandidateSet::iterator Best;
5954   OverloadingResult OR = ResolveConstructorOverload(
5955       S, Loc, CurInitExpr, CandidateSet, CurInitExpr->getType(), Ctors, Best,
5956       /*CopyInitializing=*/false, /*AllowExplicit=*/true,
5957       /*OnlyListConstructors=*/false, /*IsListInit=*/false,
5958       /*SecondStepOfCopyInit=*/true);
5959
5960   PartialDiagnostic Diag = S.PDiag(diag::warn_cxx98_compat_temp_copy)
5961     << OR << (int)Entity.getKind() << CurInitExpr->getType()
5962     << CurInitExpr->getSourceRange();
5963
5964   switch (OR) {
5965   case OR_Success:
5966     S.CheckConstructorAccess(Loc, cast<CXXConstructorDecl>(Best->Function),
5967                              Best->FoundDecl, Entity, Diag);
5968     // FIXME: Check default arguments as far as that's possible.
5969     break;
5970
5971   case OR_No_Viable_Function:
5972     S.Diag(Loc, Diag);
5973     CandidateSet.NoteCandidates(S, OCD_AllCandidates, CurInitExpr);
5974     break;
5975
5976   case OR_Ambiguous:
5977     S.Diag(Loc, Diag);
5978     CandidateSet.NoteCandidates(S, OCD_ViableCandidates, CurInitExpr);
5979     break;
5980
5981   case OR_Deleted:
5982     S.Diag(Loc, Diag);
5983     S.NoteDeletedFunction(Best->Function);
5984     break;
5985   }
5986 }
5987
5988 void InitializationSequence::PrintInitLocationNote(Sema &S,
5989                                               const InitializedEntity &Entity) {
5990   if (Entity.isParameterKind() && Entity.getDecl()) {
5991     if (Entity.getDecl()->getLocation().isInvalid())
5992       return;
5993
5994     if (Entity.getDecl()->getDeclName())
5995       S.Diag(Entity.getDecl()->getLocation(), diag::note_parameter_named_here)
5996         << Entity.getDecl()->getDeclName();
5997     else
5998       S.Diag(Entity.getDecl()->getLocation(), diag::note_parameter_here);
5999   }
6000   else if (Entity.getKind() == InitializedEntity::EK_RelatedResult &&
6001            Entity.getMethodDecl())
6002     S.Diag(Entity.getMethodDecl()->getLocation(),
6003            diag::note_method_return_type_change)
6004       << Entity.getMethodDecl()->getDeclName();
6005 }
6006
6007 /// Returns true if the parameters describe a constructor initialization of
6008 /// an explicit temporary object, e.g. "Point(x, y)".
6009 static bool isExplicitTemporary(const InitializedEntity &Entity,
6010                                 const InitializationKind &Kind,
6011                                 unsigned NumArgs) {
6012   switch (Entity.getKind()) {
6013   case InitializedEntity::EK_Temporary:
6014   case InitializedEntity::EK_CompoundLiteralInit:
6015   case InitializedEntity::EK_RelatedResult:
6016     break;
6017   default:
6018     return false;
6019   }
6020
6021   switch (Kind.getKind()) {
6022   case InitializationKind::IK_DirectList:
6023     return true;
6024   // FIXME: Hack to work around cast weirdness.
6025   case InitializationKind::IK_Direct:
6026   case InitializationKind::IK_Value:
6027     return NumArgs != 1;
6028   default:
6029     return false;
6030   }
6031 }
6032
6033 static ExprResult
6034 PerformConstructorInitialization(Sema &S,
6035                                  const InitializedEntity &Entity,
6036                                  const InitializationKind &Kind,
6037                                  MultiExprArg Args,
6038                                  const InitializationSequence::Step& Step,
6039                                  bool &ConstructorInitRequiresZeroInit,
6040                                  bool IsListInitialization,
6041                                  bool IsStdInitListInitialization,
6042                                  SourceLocation LBraceLoc,
6043                                  SourceLocation RBraceLoc) {
6044   unsigned NumArgs = Args.size();
6045   CXXConstructorDecl *Constructor
6046     = cast<CXXConstructorDecl>(Step.Function.Function);
6047   bool HadMultipleCandidates = Step.Function.HadMultipleCandidates;
6048
6049   // Build a call to the selected constructor.
6050   SmallVector<Expr*, 8> ConstructorArgs;
6051   SourceLocation Loc = (Kind.isCopyInit() && Kind.getEqualLoc().isValid())
6052                          ? Kind.getEqualLoc()
6053                          : Kind.getLocation();
6054
6055   if (Kind.getKind() == InitializationKind::IK_Default) {
6056     // Force even a trivial, implicit default constructor to be
6057     // semantically checked. We do this explicitly because we don't build
6058     // the definition for completely trivial constructors.
6059     assert(Constructor->getParent() && "No parent class for constructor.");
6060     if (Constructor->isDefaulted() && Constructor->isDefaultConstructor() &&
6061         Constructor->isTrivial() && !Constructor->isUsed(false))
6062       S.DefineImplicitDefaultConstructor(Loc, Constructor);
6063   }
6064
6065   ExprResult CurInit((Expr *)nullptr);
6066
6067   // C++ [over.match.copy]p1:
6068   //   - When initializing a temporary to be bound to the first parameter
6069   //     of a constructor that takes a reference to possibly cv-qualified
6070   //     T as its first argument, called with a single argument in the
6071   //     context of direct-initialization, explicit conversion functions
6072   //     are also considered.
6073   bool AllowExplicitConv =
6074       Kind.AllowExplicit() && !Kind.isCopyInit() && Args.size() == 1 &&
6075       hasCopyOrMoveCtorParam(S.Context,
6076                              getConstructorInfo(Step.Function.FoundDecl));
6077
6078   // Determine the arguments required to actually perform the constructor
6079   // call.
6080   if (S.CompleteConstructorCall(Constructor, Args,
6081                                 Loc, ConstructorArgs,
6082                                 AllowExplicitConv,
6083                                 IsListInitialization))
6084     return ExprError();
6085
6086
6087   if (isExplicitTemporary(Entity, Kind, NumArgs)) {
6088     // An explicitly-constructed temporary, e.g., X(1, 2).
6089     if (S.DiagnoseUseOfDecl(Constructor, Loc))
6090       return ExprError();
6091
6092     TypeSourceInfo *TSInfo = Entity.getTypeSourceInfo();
6093     if (!TSInfo)
6094       TSInfo = S.Context.getTrivialTypeSourceInfo(Entity.getType(), Loc);
6095     SourceRange ParenOrBraceRange = Kind.getParenOrBraceRange();
6096
6097     if (auto *Shadow = dyn_cast<ConstructorUsingShadowDecl>(
6098             Step.Function.FoundDecl.getDecl())) {
6099       Constructor = S.findInheritingConstructor(Loc, Constructor, Shadow);
6100       if (S.DiagnoseUseOfDecl(Constructor, Loc))
6101         return ExprError();
6102     }
6103     S.MarkFunctionReferenced(Loc, Constructor);
6104
6105     CurInit = new (S.Context) CXXTemporaryObjectExpr(
6106         S.Context, Constructor,
6107         Entity.getType().getNonLValueExprType(S.Context), TSInfo,
6108         ConstructorArgs, ParenOrBraceRange, HadMultipleCandidates,
6109         IsListInitialization, IsStdInitListInitialization,
6110         ConstructorInitRequiresZeroInit);
6111   } else {
6112     CXXConstructExpr::ConstructionKind ConstructKind =
6113       CXXConstructExpr::CK_Complete;
6114
6115     if (Entity.getKind() == InitializedEntity::EK_Base) {
6116       ConstructKind = Entity.getBaseSpecifier()->isVirtual() ?
6117         CXXConstructExpr::CK_VirtualBase :
6118         CXXConstructExpr::CK_NonVirtualBase;
6119     } else if (Entity.getKind() == InitializedEntity::EK_Delegating) {
6120       ConstructKind = CXXConstructExpr::CK_Delegating;
6121     }
6122
6123     // Only get the parenthesis or brace range if it is a list initialization or
6124     // direct construction.
6125     SourceRange ParenOrBraceRange;
6126     if (IsListInitialization)
6127       ParenOrBraceRange = SourceRange(LBraceLoc, RBraceLoc);
6128     else if (Kind.getKind() == InitializationKind::IK_Direct)
6129       ParenOrBraceRange = Kind.getParenOrBraceRange();
6130
6131     // If the entity allows NRVO, mark the construction as elidable
6132     // unconditionally.
6133     if (Entity.allowsNRVO())
6134       CurInit = S.BuildCXXConstructExpr(Loc, Step.Type,
6135                                         Step.Function.FoundDecl,
6136                                         Constructor, /*Elidable=*/true,
6137                                         ConstructorArgs,
6138                                         HadMultipleCandidates,
6139                                         IsListInitialization,
6140                                         IsStdInitListInitialization,
6141                                         ConstructorInitRequiresZeroInit,
6142                                         ConstructKind,
6143                                         ParenOrBraceRange);
6144     else
6145       CurInit = S.BuildCXXConstructExpr(Loc, Step.Type,
6146                                         Step.Function.FoundDecl,
6147                                         Constructor,
6148                                         ConstructorArgs,
6149                                         HadMultipleCandidates,
6150                                         IsListInitialization,
6151                                         IsStdInitListInitialization,
6152                                         ConstructorInitRequiresZeroInit,
6153                                         ConstructKind,
6154                                         ParenOrBraceRange);
6155   }
6156   if (CurInit.isInvalid())
6157     return ExprError();
6158
6159   // Only check access if all of that succeeded.
6160   S.CheckConstructorAccess(Loc, Constructor, Step.Function.FoundDecl, Entity);
6161   if (S.DiagnoseUseOfDecl(Step.Function.FoundDecl, Loc))
6162     return ExprError();
6163
6164   if (shouldBindAsTemporary(Entity))
6165     CurInit = S.MaybeBindToTemporary(CurInit.get());
6166
6167   return CurInit;
6168 }
6169
6170 namespace {
6171 enum LifetimeKind {
6172   /// The lifetime of a temporary bound to this entity ends at the end of the
6173   /// full-expression, and that's (probably) fine.
6174   LK_FullExpression,
6175
6176   /// The lifetime of a temporary bound to this entity is extended to the
6177   /// lifeitme of the entity itself.
6178   LK_Extended,
6179
6180   /// The lifetime of a temporary bound to this entity probably ends too soon,
6181   /// because the entity is allocated in a new-expression.
6182   LK_New,
6183
6184   /// The lifetime of a temporary bound to this entity ends too soon, because
6185   /// the entity is a return object.
6186   LK_Return,
6187
6188   /// The lifetime of a temporary bound to this entity ends too soon, because
6189   /// the entity is the result of a statement expression.
6190   LK_StmtExprResult,
6191
6192   /// This is a mem-initializer: if it would extend a temporary (other than via
6193   /// a default member initializer), the program is ill-formed.
6194   LK_MemInitializer,
6195 };
6196 using LifetimeResult =
6197     llvm::PointerIntPair<const InitializedEntity *, 3, LifetimeKind>;
6198 }
6199
6200 /// Determine the declaration which an initialized entity ultimately refers to,
6201 /// for the purpose of lifetime-extending a temporary bound to a reference in
6202 /// the initialization of \p Entity.
6203 static LifetimeResult getEntityLifetime(
6204     const InitializedEntity *Entity,
6205     const InitializedEntity *InitField = nullptr) {
6206   // C++11 [class.temporary]p5:
6207   switch (Entity->getKind()) {
6208   case InitializedEntity::EK_Variable:
6209     //   The temporary [...] persists for the lifetime of the reference
6210     return {Entity, LK_Extended};
6211
6212   case InitializedEntity::EK_Member:
6213     // For subobjects, we look at the complete object.
6214     if (Entity->getParent())
6215       return getEntityLifetime(Entity->getParent(), Entity);
6216
6217     //   except:
6218     // C++17 [class.base.init]p8:
6219     //   A temporary expression bound to a reference member in a
6220     //   mem-initializer is ill-formed.
6221     // C++17 [class.base.init]p11:
6222     //   A temporary expression bound to a reference member from a
6223     //   default member initializer is ill-formed.
6224     //
6225     // The context of p11 and its example suggest that it's only the use of a
6226     // default member initializer from a constructor that makes the program
6227     // ill-formed, not its mere existence, and that it can even be used by
6228     // aggregate initialization.
6229     return {Entity, Entity->isDefaultMemberInitializer() ? LK_Extended
6230                                                          : LK_MemInitializer};
6231
6232   case InitializedEntity::EK_Binding:
6233     // Per [dcl.decomp]p3, the binding is treated as a variable of reference
6234     // type.
6235     return {Entity, LK_Extended};
6236
6237   case InitializedEntity::EK_Parameter:
6238   case InitializedEntity::EK_Parameter_CF_Audited:
6239     //   -- A temporary bound to a reference parameter in a function call
6240     //      persists until the completion of the full-expression containing
6241     //      the call.
6242     return {nullptr, LK_FullExpression};
6243
6244   case InitializedEntity::EK_Result:
6245     //   -- The lifetime of a temporary bound to the returned value in a
6246     //      function return statement is not extended; the temporary is
6247     //      destroyed at the end of the full-expression in the return statement.
6248     return {nullptr, LK_Return};
6249
6250   case InitializedEntity::EK_StmtExprResult:
6251     // FIXME: Should we lifetime-extend through the result of a statement
6252     // expression?
6253     return {nullptr, LK_StmtExprResult};
6254
6255   case InitializedEntity::EK_New:
6256     //   -- A temporary bound to a reference in a new-initializer persists
6257     //      until the completion of the full-expression containing the
6258     //      new-initializer.
6259     return {nullptr, LK_New};
6260
6261   case InitializedEntity::EK_Temporary:
6262   case InitializedEntity::EK_CompoundLiteralInit:
6263   case InitializedEntity::EK_RelatedResult:
6264     // We don't yet know the storage duration of the surrounding temporary.
6265     // Assume it's got full-expression duration for now, it will patch up our
6266     // storage duration if that's not correct.
6267     return {nullptr, LK_FullExpression};
6268
6269   case InitializedEntity::EK_ArrayElement:
6270     // For subobjects, we look at the complete object.
6271     return getEntityLifetime(Entity->getParent(), InitField);
6272
6273   case InitializedEntity::EK_Base:
6274     // For subobjects, we look at the complete object.
6275     if (Entity->getParent())
6276       return getEntityLifetime(Entity->getParent(), InitField);
6277     return {InitField, LK_MemInitializer};
6278
6279   case InitializedEntity::EK_Delegating:
6280     // We can reach this case for aggregate initialization in a constructor:
6281     //   struct A { int &&r; };
6282     //   struct B : A { B() : A{0} {} };
6283     // In this case, use the outermost field decl as the context.
6284     return {InitField, LK_MemInitializer};
6285
6286   case InitializedEntity::EK_BlockElement:
6287   case InitializedEntity::EK_LambdaToBlockConversionBlockElement:
6288   case InitializedEntity::EK_LambdaCapture:
6289   case InitializedEntity::EK_VectorElement:
6290   case InitializedEntity::EK_ComplexElement:
6291     return {nullptr, LK_FullExpression};
6292
6293   case InitializedEntity::EK_Exception:
6294     // FIXME: Can we diagnose lifetime problems with exceptions?
6295     return {nullptr, LK_FullExpression};
6296   }
6297   llvm_unreachable("unknown entity kind");
6298 }
6299
6300 namespace {
6301 enum ReferenceKind {
6302   /// Lifetime would be extended by a reference binding to a temporary.
6303   RK_ReferenceBinding,
6304   /// Lifetime would be extended by a std::initializer_list object binding to
6305   /// its backing array.
6306   RK_StdInitializerList,
6307 };
6308
6309 /// A temporary or local variable. This will be one of:
6310 ///  * A MaterializeTemporaryExpr.
6311 ///  * A DeclRefExpr whose declaration is a local.
6312 ///  * An AddrLabelExpr.
6313 ///  * A BlockExpr for a block with captures.
6314 using Local = Expr*;
6315
6316 /// Expressions we stepped over when looking for the local state. Any steps
6317 /// that would inhibit lifetime extension or take us out of subexpressions of
6318 /// the initializer are included.
6319 struct IndirectLocalPathEntry {
6320   enum EntryKind {
6321     DefaultInit,
6322     AddressOf,
6323     VarInit,
6324     LValToRVal,
6325   } Kind;
6326   Expr *E;
6327   Decl *D = nullptr;
6328   IndirectLocalPathEntry() {}
6329   IndirectLocalPathEntry(EntryKind K, Expr *E) : Kind(K), E(E) {}
6330   IndirectLocalPathEntry(EntryKind K, Expr *E, Decl *D) : Kind(K), E(E), D(D) {}
6331 };
6332
6333 using IndirectLocalPath = llvm::SmallVectorImpl<IndirectLocalPathEntry>;
6334
6335 struct RevertToOldSizeRAII {
6336   IndirectLocalPath &Path;
6337   unsigned OldSize = Path.size();
6338   RevertToOldSizeRAII(IndirectLocalPath &Path) : Path(Path) {}
6339   ~RevertToOldSizeRAII() { Path.resize(OldSize); }
6340 };
6341
6342 using LocalVisitor = llvm::function_ref<bool(IndirectLocalPath &Path, Local L,
6343                                              ReferenceKind RK)>;
6344 }
6345
6346 static bool isVarOnPath(IndirectLocalPath &Path, VarDecl *VD) {
6347   for (auto E : Path)
6348     if (E.Kind == IndirectLocalPathEntry::VarInit && E.D == VD)
6349       return true;
6350   return false;
6351 }
6352
6353 static bool pathContainsInit(IndirectLocalPath &Path) {
6354   return std::any_of(Path.begin(), Path.end(), [=](IndirectLocalPathEntry E) {
6355     return E.Kind == IndirectLocalPathEntry::DefaultInit ||
6356            E.Kind == IndirectLocalPathEntry::VarInit;
6357   });
6358 }
6359
6360 static void visitLocalsRetainedByInitializer(IndirectLocalPath &Path,
6361                                              Expr *Init, LocalVisitor Visit,
6362                                              bool RevisitSubinits);
6363
6364 /// Visit the locals that would be reachable through a reference bound to the
6365 /// glvalue expression \c Init.
6366 static void visitLocalsRetainedByReferenceBinding(IndirectLocalPath &Path,
6367                                                   Expr *Init, ReferenceKind RK,
6368                                                   LocalVisitor Visit) {
6369   RevertToOldSizeRAII RAII(Path);
6370
6371   // Walk past any constructs which we can lifetime-extend across.
6372   Expr *Old;
6373   do {
6374     Old = Init;
6375
6376     if (auto *EWC = dyn_cast<ExprWithCleanups>(Init))
6377       Init = EWC->getSubExpr();
6378
6379     if (InitListExpr *ILE = dyn_cast<InitListExpr>(Init)) {
6380       // If this is just redundant braces around an initializer, step over it.
6381       if (ILE->isTransparent())
6382         Init = ILE->getInit(0);
6383     }
6384
6385     // Step over any subobject adjustments; we may have a materialized
6386     // temporary inside them.
6387     Init = const_cast<Expr *>(Init->skipRValueSubobjectAdjustments());
6388
6389     // Per current approach for DR1376, look through casts to reference type
6390     // when performing lifetime extension.
6391     if (CastExpr *CE = dyn_cast<CastExpr>(Init))
6392       if (CE->getSubExpr()->isGLValue())
6393         Init = CE->getSubExpr();
6394
6395     // Per the current approach for DR1299, look through array element access
6396     // on array glvalues when performing lifetime extension.
6397     if (auto *ASE = dyn_cast<ArraySubscriptExpr>(Init)) {
6398       Init = ASE->getBase();
6399       auto *ICE = dyn_cast<ImplicitCastExpr>(Init);
6400       if (ICE && ICE->getCastKind() == CK_ArrayToPointerDecay)
6401         Init = ICE->getSubExpr();
6402       else
6403         // We can't lifetime extend through this but we might still find some
6404         // retained temporaries.
6405         return visitLocalsRetainedByInitializer(Path, Init, Visit, true);
6406     }
6407
6408     // Step into CXXDefaultInitExprs so we can diagnose cases where a
6409     // constructor inherits one as an implicit mem-initializer.
6410     if (auto *DIE = dyn_cast<CXXDefaultInitExpr>(Init)) {
6411       Path.push_back(
6412           {IndirectLocalPathEntry::DefaultInit, DIE, DIE->getField()});
6413       Init = DIE->getExpr();
6414     }
6415   } while (Init != Old);
6416
6417   if (auto *MTE = dyn_cast<MaterializeTemporaryExpr>(Init)) {
6418     if (Visit(Path, Local(MTE), RK))
6419       visitLocalsRetainedByInitializer(Path, MTE->GetTemporaryExpr(), Visit,
6420                                        true);
6421   }
6422
6423   switch (Init->getStmtClass()) {
6424   case Stmt::DeclRefExprClass: {
6425     // If we find the name of a local non-reference parameter, we could have a
6426     // lifetime problem.
6427     auto *DRE = cast<DeclRefExpr>(Init);
6428     auto *VD = dyn_cast<VarDecl>(DRE->getDecl());
6429     if (VD && VD->hasLocalStorage() &&
6430         !DRE->refersToEnclosingVariableOrCapture()) {
6431       if (!VD->getType()->isReferenceType()) {
6432         Visit(Path, Local(DRE), RK);
6433       } else if (isa<ParmVarDecl>(DRE->getDecl())) {
6434         // The lifetime of a reference parameter is unknown; assume it's OK
6435         // for now.
6436         break;
6437       } else if (VD->getInit() && !isVarOnPath(Path, VD)) {
6438         Path.push_back({IndirectLocalPathEntry::VarInit, DRE, VD});
6439         visitLocalsRetainedByReferenceBinding(Path, VD->getInit(),
6440                                               RK_ReferenceBinding, Visit);
6441       }
6442     }
6443     break;
6444   }
6445
6446   case Stmt::UnaryOperatorClass: {
6447     // The only unary operator that make sense to handle here
6448     // is Deref.  All others don't resolve to a "name."  This includes
6449     // handling all sorts of rvalues passed to a unary operator.
6450     const UnaryOperator *U = cast<UnaryOperator>(Init);
6451     if (U->getOpcode() == UO_Deref)
6452       visitLocalsRetainedByInitializer(Path, U->getSubExpr(), Visit, true);
6453     break;
6454   }
6455
6456   case Stmt::OMPArraySectionExprClass: {
6457     visitLocalsRetainedByInitializer(
6458         Path, cast<OMPArraySectionExpr>(Init)->getBase(), Visit, true);
6459     break;
6460   }
6461
6462   case Stmt::ConditionalOperatorClass:
6463   case Stmt::BinaryConditionalOperatorClass: {
6464     auto *C = cast<AbstractConditionalOperator>(Init);
6465     if (!C->getTrueExpr()->getType()->isVoidType())
6466       visitLocalsRetainedByReferenceBinding(Path, C->getTrueExpr(), RK, Visit);
6467     if (!C->getFalseExpr()->getType()->isVoidType())
6468       visitLocalsRetainedByReferenceBinding(Path, C->getFalseExpr(), RK, Visit);
6469     break;
6470   }
6471
6472   // FIXME: Visit the left-hand side of an -> or ->*.
6473
6474   default:
6475     break;
6476   }
6477 }
6478
6479 /// Visit the locals that would be reachable through an object initialized by
6480 /// the prvalue expression \c Init.
6481 static void visitLocalsRetainedByInitializer(IndirectLocalPath &Path,
6482                                              Expr *Init, LocalVisitor Visit,
6483                                              bool RevisitSubinits) {
6484   RevertToOldSizeRAII RAII(Path);
6485
6486   // Step into CXXDefaultInitExprs so we can diagnose cases where a
6487   // constructor inherits one as an implicit mem-initializer.
6488   if (auto *DIE = dyn_cast<CXXDefaultInitExpr>(Init)) {
6489     Path.push_back({IndirectLocalPathEntry::DefaultInit, DIE, DIE->getField()});
6490     Init = DIE->getExpr();
6491   }
6492
6493   if (auto *EWC = dyn_cast<ExprWithCleanups>(Init))
6494     Init = EWC->getSubExpr();
6495
6496   // Dig out the expression which constructs the extended temporary.
6497   Init = const_cast<Expr *>(Init->skipRValueSubobjectAdjustments());
6498
6499   if (CXXBindTemporaryExpr *BTE = dyn_cast<CXXBindTemporaryExpr>(Init))
6500     Init = BTE->getSubExpr();
6501
6502   // C++17 [dcl.init.list]p6:
6503   //   initializing an initializer_list object from the array extends the
6504   //   lifetime of the array exactly like binding a reference to a temporary.
6505   if (auto *ILE = dyn_cast<CXXStdInitializerListExpr>(Init))
6506     return visitLocalsRetainedByReferenceBinding(Path, ILE->getSubExpr(),
6507                                                  RK_StdInitializerList, Visit);
6508
6509   if (InitListExpr *ILE = dyn_cast<InitListExpr>(Init)) {
6510     // We already visited the elements of this initializer list while
6511     // performing the initialization. Don't visit them again unless we've
6512     // changed the lifetime of the initialized entity.
6513     if (!RevisitSubinits)
6514       return;
6515
6516     if (ILE->isTransparent())
6517       return visitLocalsRetainedByInitializer(Path, ILE->getInit(0), Visit,
6518                                               RevisitSubinits);
6519
6520     if (ILE->getType()->isArrayType()) {
6521       for (unsigned I = 0, N = ILE->getNumInits(); I != N; ++I)
6522         visitLocalsRetainedByInitializer(Path, ILE->getInit(I), Visit,
6523                                          RevisitSubinits);
6524       return;
6525     }
6526
6527     if (CXXRecordDecl *RD = ILE->getType()->getAsCXXRecordDecl()) {
6528       assert(RD->isAggregate() && "aggregate init on non-aggregate");
6529
6530       // If we lifetime-extend a braced initializer which is initializing an
6531       // aggregate, and that aggregate contains reference members which are
6532       // bound to temporaries, those temporaries are also lifetime-extended.
6533       if (RD->isUnion() && ILE->getInitializedFieldInUnion() &&
6534           ILE->getInitializedFieldInUnion()->getType()->isReferenceType())
6535         visitLocalsRetainedByReferenceBinding(Path, ILE->getInit(0),
6536                                               RK_ReferenceBinding, Visit);
6537       else {
6538         unsigned Index = 0;
6539         for (const auto *I : RD->fields()) {
6540           if (Index >= ILE->getNumInits())
6541             break;
6542           if (I->isUnnamedBitfield())
6543             continue;
6544           Expr *SubInit = ILE->getInit(Index);
6545           if (I->getType()->isReferenceType())
6546             visitLocalsRetainedByReferenceBinding(Path, SubInit,
6547                                                   RK_ReferenceBinding, Visit);
6548           else
6549             // This might be either aggregate-initialization of a member or
6550             // initialization of a std::initializer_list object. Regardless,
6551             // we should recursively lifetime-extend that initializer.
6552             visitLocalsRetainedByInitializer(Path, SubInit, Visit,
6553                                              RevisitSubinits);
6554           ++Index;
6555         }
6556       }
6557     }
6558     return;
6559   }
6560
6561   // Step over value-preserving rvalue casts.
6562   while (auto *CE = dyn_cast<CastExpr>(Init)) {
6563     switch (CE->getCastKind()) {
6564     case CK_LValueToRValue:
6565       // If we can match the lvalue to a const object, we can look at its
6566       // initializer.
6567       Path.push_back({IndirectLocalPathEntry::LValToRVal, CE});
6568       return visitLocalsRetainedByReferenceBinding(
6569           Path, Init, RK_ReferenceBinding,
6570           [&](IndirectLocalPath &Path, Local L, ReferenceKind RK) -> bool {
6571         if (auto *DRE = dyn_cast<DeclRefExpr>(L)) {
6572           auto *VD = dyn_cast<VarDecl>(DRE->getDecl());
6573           if (VD && VD->getType().isConstQualified() && VD->getInit()) {
6574             Path.push_back({IndirectLocalPathEntry::VarInit, DRE, VD});
6575             visitLocalsRetainedByInitializer(Path, VD->getInit(), Visit, true);
6576           }
6577         } else if (auto *MTE = dyn_cast<MaterializeTemporaryExpr>(L)) {
6578           if (MTE->getType().isConstQualified())
6579             visitLocalsRetainedByInitializer(Path, MTE->GetTemporaryExpr(),
6580                                              Visit, true);
6581         }
6582         return false;
6583       });
6584
6585       // We assume that objects can be retained by pointers cast to integers,
6586       // but not if the integer is cast to floating-point type or to _Complex.
6587       // We assume that casts to 'bool' do not preserve enough information to
6588       // retain a local object.
6589     case CK_NoOp:
6590     case CK_BitCast:
6591     case CK_BaseToDerived:
6592     case CK_DerivedToBase:
6593     case CK_UncheckedDerivedToBase:
6594     case CK_Dynamic:
6595     case CK_ToUnion:
6596     case CK_IntegralToPointer:
6597     case CK_PointerToIntegral:
6598     case CK_VectorSplat:
6599     case CK_IntegralCast:
6600     case CK_CPointerToObjCPointerCast:
6601     case CK_BlockPointerToObjCPointerCast:
6602     case CK_AnyPointerToBlockPointerCast:
6603     case CK_AddressSpaceConversion:
6604       break;
6605
6606     case CK_ArrayToPointerDecay:
6607       // Model array-to-pointer decay as taking the address of the array
6608       // lvalue.
6609       Path.push_back({IndirectLocalPathEntry::AddressOf, CE});
6610       return visitLocalsRetainedByReferenceBinding(Path, CE->getSubExpr(),
6611                                                    RK_ReferenceBinding, Visit);
6612
6613     default:
6614       return;
6615     }
6616
6617     Init = CE->getSubExpr();
6618   }
6619
6620   Init = Init->IgnoreParens();
6621   switch (Init->getStmtClass()) {
6622   case Stmt::UnaryOperatorClass: {
6623     auto *UO = cast<UnaryOperator>(Init);
6624     // If the initializer is the address of a local, we could have a lifetime
6625     // problem.
6626     if (UO->getOpcode() == UO_AddrOf) {
6627       // If this is &rvalue, then it's ill-formed and we have already diagnosed
6628       // it. Don't produce a redundant warning about the lifetime of the
6629       // temporary.
6630       if (isa<MaterializeTemporaryExpr>(UO->getSubExpr()))
6631         return;
6632
6633       Path.push_back({IndirectLocalPathEntry::AddressOf, UO});
6634       visitLocalsRetainedByReferenceBinding(Path, UO->getSubExpr(),
6635                                             RK_ReferenceBinding, Visit);
6636     }
6637     break;
6638   }
6639
6640   case Stmt::BinaryOperatorClass: {
6641     // Handle pointer arithmetic.
6642     auto *BO = cast<BinaryOperator>(Init);
6643     BinaryOperatorKind BOK = BO->getOpcode();
6644     if (!BO->getType()->isPointerType() || (BOK != BO_Add && BOK != BO_Sub))
6645       break;
6646
6647     if (BO->getLHS()->getType()->isPointerType())
6648       visitLocalsRetainedByInitializer(Path, BO->getLHS(), Visit, true);
6649     else if (BO->getRHS()->getType()->isPointerType())
6650       visitLocalsRetainedByInitializer(Path, BO->getRHS(), Visit, true);
6651     break;
6652   }
6653
6654   case Stmt::ConditionalOperatorClass:
6655   case Stmt::BinaryConditionalOperatorClass: {
6656     auto *C = cast<AbstractConditionalOperator>(Init);
6657     // In C++, we can have a throw-expression operand, which has 'void' type
6658     // and isn't interesting from a lifetime perspective.
6659     if (!C->getTrueExpr()->getType()->isVoidType())
6660       visitLocalsRetainedByInitializer(Path, C->getTrueExpr(), Visit, true);
6661     if (!C->getFalseExpr()->getType()->isVoidType())
6662       visitLocalsRetainedByInitializer(Path, C->getFalseExpr(), Visit, true);
6663     break;
6664   }
6665
6666   case Stmt::BlockExprClass:
6667     if (cast<BlockExpr>(Init)->getBlockDecl()->hasCaptures()) {
6668       // This is a local block, whose lifetime is that of the function.
6669       Visit(Path, Local(cast<BlockExpr>(Init)), RK_ReferenceBinding);
6670     }
6671     break;
6672
6673   case Stmt::AddrLabelExprClass:
6674     // We want to warn if the address of a label would escape the function.
6675     Visit(Path, Local(cast<AddrLabelExpr>(Init)), RK_ReferenceBinding);
6676     break;
6677
6678   default:
6679     break;
6680   }
6681 }
6682
6683 /// Determine whether this is an indirect path to a temporary that we are
6684 /// supposed to lifetime-extend along (but don't).
6685 static bool shouldLifetimeExtendThroughPath(const IndirectLocalPath &Path) {
6686   for (auto Elem : Path) {
6687     if (Elem.Kind != IndirectLocalPathEntry::DefaultInit)
6688       return false;
6689   }
6690   return true;
6691 }
6692
6693 /// Find the range for the first interesting entry in the path at or after I.
6694 static SourceRange nextPathEntryRange(const IndirectLocalPath &Path, unsigned I,
6695                                       Expr *E) {
6696   for (unsigned N = Path.size(); I != N; ++I) {
6697     switch (Path[I].Kind) {
6698     case IndirectLocalPathEntry::AddressOf:
6699     case IndirectLocalPathEntry::LValToRVal:
6700       // These exist primarily to mark the path as not permitting or
6701       // supporting lifetime extension.
6702       break;
6703
6704     case IndirectLocalPathEntry::DefaultInit:
6705     case IndirectLocalPathEntry::VarInit:
6706       return Path[I].E->getSourceRange();
6707     }
6708   }
6709   return E->getSourceRange();
6710 }
6711
6712 void Sema::checkInitializerLifetime(const InitializedEntity &Entity,
6713                                     Expr *Init) {
6714   LifetimeResult LR = getEntityLifetime(&Entity);
6715   LifetimeKind LK = LR.getInt();
6716   const InitializedEntity *ExtendingEntity = LR.getPointer();
6717
6718   // If this entity doesn't have an interesting lifetime, don't bother looking
6719   // for temporaries within its initializer.
6720   if (LK == LK_FullExpression)
6721     return;
6722
6723   auto TemporaryVisitor = [&](IndirectLocalPath &Path, Local L,
6724                               ReferenceKind RK) -> bool {
6725     SourceRange DiagRange = nextPathEntryRange(Path, 0, L);
6726     SourceLocation DiagLoc = DiagRange.getBegin();
6727
6728     switch (LK) {
6729     case LK_FullExpression:
6730       llvm_unreachable("already handled this");
6731
6732     case LK_Extended: {
6733       auto *MTE = dyn_cast<MaterializeTemporaryExpr>(L);
6734       if (!MTE) {
6735         // The initialized entity has lifetime beyond the full-expression,
6736         // and the local entity does too, so don't warn.
6737         //
6738         // FIXME: We should consider warning if a static / thread storage
6739         // duration variable retains an automatic storage duration local.
6740         return false;
6741       }
6742
6743       // Lifetime-extend the temporary.
6744       if (Path.empty()) {
6745         // Update the storage duration of the materialized temporary.
6746         // FIXME: Rebuild the expression instead of mutating it.
6747         MTE->setExtendingDecl(ExtendingEntity->getDecl(),
6748                               ExtendingEntity->allocateManglingNumber());
6749         // Also visit the temporaries lifetime-extended by this initializer.
6750         return true;
6751       }
6752
6753       if (shouldLifetimeExtendThroughPath(Path)) {
6754         // We're supposed to lifetime-extend the temporary along this path (per
6755         // the resolution of DR1815), but we don't support that yet.
6756         //
6757         // FIXME: Properly handle this situation. Perhaps the easiest approach
6758         // would be to clone the initializer expression on each use that would
6759         // lifetime extend its temporaries.
6760         Diag(DiagLoc, diag::warn_unsupported_lifetime_extension)
6761             << RK << DiagRange;
6762       } else {
6763         // If the path goes through the initialization of a variable or field,
6764         // it can't possibly reach a temporary created in this full-expression.
6765         // We will have already diagnosed any problems with the initializer.
6766         if (pathContainsInit(Path))
6767           return false;
6768
6769         Diag(DiagLoc, diag::warn_dangling_variable)
6770             << RK << !Entity.getParent() << ExtendingEntity->getDecl()
6771             << Init->isGLValue() << DiagRange;
6772       }
6773       break;
6774     }
6775
6776     case LK_MemInitializer: {
6777       if (isa<MaterializeTemporaryExpr>(L)) {
6778         // Under C++ DR1696, if a mem-initializer (or a default member
6779         // initializer used by the absence of one) would lifetime-extend a
6780         // temporary, the program is ill-formed.
6781         if (auto *ExtendingDecl =
6782                 ExtendingEntity ? ExtendingEntity->getDecl() : nullptr) {
6783           bool IsSubobjectMember = ExtendingEntity != &Entity;
6784           Diag(DiagLoc, shouldLifetimeExtendThroughPath(Path)
6785                             ? diag::err_dangling_member
6786                             : diag::warn_dangling_member)
6787               << ExtendingDecl << IsSubobjectMember << RK << DiagRange;
6788           // Don't bother adding a note pointing to the field if we're inside
6789           // its default member initializer; our primary diagnostic points to
6790           // the same place in that case.
6791           if (Path.empty() ||
6792               Path.back().Kind != IndirectLocalPathEntry::DefaultInit) {
6793             Diag(ExtendingDecl->getLocation(),
6794                  diag::note_lifetime_extending_member_declared_here)
6795                 << RK << IsSubobjectMember;
6796           }
6797         } else {
6798           // We have a mem-initializer but no particular field within it; this
6799           // is either a base class or a delegating initializer directly
6800           // initializing the base-class from something that doesn't live long
6801           // enough.
6802           //
6803           // FIXME: Warn on this.
6804           return false;
6805         }
6806       } else {
6807         // Paths via a default initializer can only occur during error recovery
6808         // (there's no other way that a default initializer can refer to a
6809         // local). Don't produce a bogus warning on those cases.
6810         if (pathContainsInit(Path))
6811           return false;
6812
6813         auto *DRE = dyn_cast<DeclRefExpr>(L);
6814         auto *VD = DRE ? dyn_cast<VarDecl>(DRE->getDecl()) : nullptr;
6815         if (!VD) {
6816           // A member was initialized to a local block.
6817           // FIXME: Warn on this.
6818           return false;
6819         }
6820
6821         if (auto *Member =
6822                 ExtendingEntity ? ExtendingEntity->getDecl() : nullptr) {
6823           bool IsPointer = Member->getType()->isAnyPointerType();
6824           Diag(DiagLoc, IsPointer ? diag::warn_init_ptr_member_to_parameter_addr
6825                                   : diag::warn_bind_ref_member_to_parameter)
6826               << Member << VD << isa<ParmVarDecl>(VD) << DiagRange;
6827           Diag(Member->getLocation(),
6828                diag::note_ref_or_ptr_member_declared_here)
6829               << (unsigned)IsPointer;
6830         }
6831       }
6832       break;
6833     }
6834
6835     case LK_New:
6836       if (isa<MaterializeTemporaryExpr>(L)) {
6837         Diag(DiagLoc, RK == RK_ReferenceBinding
6838                           ? diag::warn_new_dangling_reference
6839                           : diag::warn_new_dangling_initializer_list)
6840             << !Entity.getParent() << DiagRange;
6841       } else {
6842         // We can't determine if the allocation outlives the local declaration.
6843         return false;
6844       }
6845       break;
6846
6847     case LK_Return:
6848     case LK_StmtExprResult:
6849       if (auto *DRE = dyn_cast<DeclRefExpr>(L)) {
6850         // We can't determine if the local variable outlives the statement
6851         // expression.
6852         if (LK == LK_StmtExprResult)
6853           return false;
6854         Diag(DiagLoc, diag::warn_ret_stack_addr_ref)
6855             << Entity.getType()->isReferenceType() << DRE->getDecl()
6856             << isa<ParmVarDecl>(DRE->getDecl()) << DiagRange;
6857       } else if (isa<BlockExpr>(L)) {
6858         Diag(DiagLoc, diag::err_ret_local_block) << DiagRange;
6859       } else if (isa<AddrLabelExpr>(L)) {
6860         Diag(DiagLoc, diag::warn_ret_addr_label) << DiagRange;
6861       } else {
6862         Diag(DiagLoc, diag::warn_ret_local_temp_addr_ref)
6863          << Entity.getType()->isReferenceType() << DiagRange;
6864       }
6865       break;
6866     }
6867
6868     for (unsigned I = 0; I != Path.size(); ++I) {
6869       auto Elem = Path[I];
6870
6871       switch (Elem.Kind) {
6872       case IndirectLocalPathEntry::AddressOf:
6873       case IndirectLocalPathEntry::LValToRVal:
6874         // These exist primarily to mark the path as not permitting or
6875         // supporting lifetime extension.
6876         break;
6877
6878       case IndirectLocalPathEntry::DefaultInit: {
6879         auto *FD = cast<FieldDecl>(Elem.D);
6880         Diag(FD->getLocation(), diag::note_init_with_default_member_initalizer)
6881             << FD << nextPathEntryRange(Path, I + 1, L);
6882         break;
6883       }
6884
6885       case IndirectLocalPathEntry::VarInit:
6886         const VarDecl *VD = cast<VarDecl>(Elem.D);
6887         Diag(VD->getLocation(), diag::note_local_var_initializer)
6888             << VD->getType()->isReferenceType() << VD->getDeclName()
6889             << nextPathEntryRange(Path, I + 1, L);
6890         break;
6891       }
6892     }
6893
6894     // We didn't lifetime-extend, so don't go any further; we don't need more
6895     // warnings or errors on inner temporaries within this one's initializer.
6896     return false;
6897   };
6898
6899   llvm::SmallVector<IndirectLocalPathEntry, 8> Path;
6900   if (Init->isGLValue())
6901     visitLocalsRetainedByReferenceBinding(Path, Init, RK_ReferenceBinding,
6902                                           TemporaryVisitor);
6903   else
6904     visitLocalsRetainedByInitializer(Path, Init, TemporaryVisitor, false);
6905 }
6906
6907 static void DiagnoseNarrowingInInitList(Sema &S,
6908                                         const ImplicitConversionSequence &ICS,
6909                                         QualType PreNarrowingType,
6910                                         QualType EntityType,
6911                                         const Expr *PostInit);
6912
6913 /// Provide warnings when std::move is used on construction.
6914 static void CheckMoveOnConstruction(Sema &S, const Expr *InitExpr,
6915                                     bool IsReturnStmt) {
6916   if (!InitExpr)
6917     return;
6918
6919   if (S.inTemplateInstantiation())
6920     return;
6921
6922   QualType DestType = InitExpr->getType();
6923   if (!DestType->isRecordType())
6924     return;
6925
6926   unsigned DiagID = 0;
6927   if (IsReturnStmt) {
6928     const CXXConstructExpr *CCE =
6929         dyn_cast<CXXConstructExpr>(InitExpr->IgnoreParens());
6930     if (!CCE || CCE->getNumArgs() != 1)
6931       return;
6932
6933     if (!CCE->getConstructor()->isCopyOrMoveConstructor())
6934       return;
6935
6936     InitExpr = CCE->getArg(0)->IgnoreImpCasts();
6937   }
6938
6939   // Find the std::move call and get the argument.
6940   const CallExpr *CE = dyn_cast<CallExpr>(InitExpr->IgnoreParens());
6941   if (!CE || !CE->isCallToStdMove())
6942     return;
6943
6944   const Expr *Arg = CE->getArg(0)->IgnoreImplicit();
6945
6946   if (IsReturnStmt) {
6947     const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(Arg->IgnoreParenImpCasts());
6948     if (!DRE || DRE->refersToEnclosingVariableOrCapture())
6949       return;
6950
6951     const VarDecl *VD = dyn_cast<VarDecl>(DRE->getDecl());
6952     if (!VD || !VD->hasLocalStorage())
6953       return;
6954
6955     // __block variables are not moved implicitly.
6956     if (VD->hasAttr<BlocksAttr>())
6957       return;
6958
6959     QualType SourceType = VD->getType();
6960     if (!SourceType->isRecordType())
6961       return;
6962
6963     if (!S.Context.hasSameUnqualifiedType(DestType, SourceType)) {
6964       return;
6965     }
6966
6967     // If we're returning a function parameter, copy elision
6968     // is not possible.
6969     if (isa<ParmVarDecl>(VD))
6970       DiagID = diag::warn_redundant_move_on_return;
6971     else
6972       DiagID = diag::warn_pessimizing_move_on_return;
6973   } else {
6974     DiagID = diag::warn_pessimizing_move_on_initialization;
6975     const Expr *ArgStripped = Arg->IgnoreImplicit()->IgnoreParens();
6976     if (!ArgStripped->isRValue() || !ArgStripped->getType()->isRecordType())
6977       return;
6978   }
6979
6980   S.Diag(CE->getLocStart(), DiagID);
6981
6982   // Get all the locations for a fix-it.  Don't emit the fix-it if any location
6983   // is within a macro.
6984   SourceLocation CallBegin = CE->getCallee()->getLocStart();
6985   if (CallBegin.isMacroID())
6986     return;
6987   SourceLocation RParen = CE->getRParenLoc();
6988   if (RParen.isMacroID())
6989     return;
6990   SourceLocation LParen;
6991   SourceLocation ArgLoc = Arg->getLocStart();
6992
6993   // Special testing for the argument location.  Since the fix-it needs the
6994   // location right before the argument, the argument location can be in a
6995   // macro only if it is at the beginning of the macro.
6996   while (ArgLoc.isMacroID() &&
6997          S.getSourceManager().isAtStartOfImmediateMacroExpansion(ArgLoc)) {
6998     ArgLoc = S.getSourceManager().getImmediateExpansionRange(ArgLoc).getBegin();
6999   }
7000
7001   if (LParen.isMacroID())
7002     return;
7003
7004   LParen = ArgLoc.getLocWithOffset(-1);
7005
7006   S.Diag(CE->getLocStart(), diag::note_remove_move)
7007       << FixItHint::CreateRemoval(SourceRange(CallBegin, LParen))
7008       << FixItHint::CreateRemoval(SourceRange(RParen, RParen));
7009 }
7010
7011 static void CheckForNullPointerDereference(Sema &S, const Expr *E) {
7012   // Check to see if we are dereferencing a null pointer.  If so, this is
7013   // undefined behavior, so warn about it.  This only handles the pattern
7014   // "*null", which is a very syntactic check.
7015   if (const UnaryOperator *UO = dyn_cast<UnaryOperator>(E->IgnoreParenCasts()))
7016     if (UO->getOpcode() == UO_Deref &&
7017         UO->getSubExpr()->IgnoreParenCasts()->
7018         isNullPointerConstant(S.Context, Expr::NPC_ValueDependentIsNotNull)) {
7019     S.DiagRuntimeBehavior(UO->getOperatorLoc(), UO,
7020                           S.PDiag(diag::warn_binding_null_to_reference)
7021                             << UO->getSubExpr()->getSourceRange());
7022   }
7023 }
7024
7025 MaterializeTemporaryExpr *
7026 Sema::CreateMaterializeTemporaryExpr(QualType T, Expr *Temporary,
7027                                      bool BoundToLvalueReference) {
7028   auto MTE = new (Context)
7029       MaterializeTemporaryExpr(T, Temporary, BoundToLvalueReference);
7030
7031   // Order an ExprWithCleanups for lifetime marks.
7032   //
7033   // TODO: It'll be good to have a single place to check the access of the
7034   // destructor and generate ExprWithCleanups for various uses. Currently these
7035   // are done in both CreateMaterializeTemporaryExpr and MaybeBindToTemporary,
7036   // but there may be a chance to merge them.
7037   Cleanup.setExprNeedsCleanups(false);
7038   return MTE;
7039 }
7040
7041 ExprResult Sema::TemporaryMaterializationConversion(Expr *E) {
7042   // In C++98, we don't want to implicitly create an xvalue.
7043   // FIXME: This means that AST consumers need to deal with "prvalues" that
7044   // denote materialized temporaries. Maybe we should add another ValueKind
7045   // for "xvalue pretending to be a prvalue" for C++98 support.
7046   if (!E->isRValue() || !getLangOpts().CPlusPlus11)
7047     return E;
7048
7049   // C++1z [conv.rval]/1: T shall be a complete type.
7050   // FIXME: Does this ever matter (can we form a prvalue of incomplete type)?
7051   // If so, we should check for a non-abstract class type here too.
7052   QualType T = E->getType();
7053   if (RequireCompleteType(E->getExprLoc(), T, diag::err_incomplete_type))
7054     return ExprError();
7055
7056   return CreateMaterializeTemporaryExpr(E->getType(), E, false);
7057 }
7058
7059 ExprResult
7060 InitializationSequence::Perform(Sema &S,
7061                                 const InitializedEntity &Entity,
7062                                 const InitializationKind &Kind,
7063                                 MultiExprArg Args,
7064                                 QualType *ResultType) {
7065   if (Failed()) {
7066     Diagnose(S, Entity, Kind, Args);
7067     return ExprError();
7068   }
7069   if (!ZeroInitializationFixit.empty()) {
7070     unsigned DiagID = diag::err_default_init_const;
7071     if (Decl *D = Entity.getDecl())
7072       if (S.getLangOpts().MSVCCompat && D->hasAttr<SelectAnyAttr>())
7073         DiagID = diag::ext_default_init_const;
7074
7075     // The initialization would have succeeded with this fixit. Since the fixit
7076     // is on the error, we need to build a valid AST in this case, so this isn't
7077     // handled in the Failed() branch above.
7078     QualType DestType = Entity.getType();
7079     S.Diag(Kind.getLocation(), DiagID)
7080         << DestType << (bool)DestType->getAs<RecordType>()
7081         << FixItHint::CreateInsertion(ZeroInitializationFixitLoc,
7082                                       ZeroInitializationFixit);
7083   }
7084
7085   if (getKind() == DependentSequence) {
7086     // If the declaration is a non-dependent, incomplete array type
7087     // that has an initializer, then its type will be completed once
7088     // the initializer is instantiated.
7089     if (ResultType && !Entity.getType()->isDependentType() &&
7090         Args.size() == 1) {
7091       QualType DeclType = Entity.getType();
7092       if (const IncompleteArrayType *ArrayT
7093                            = S.Context.getAsIncompleteArrayType(DeclType)) {
7094         // FIXME: We don't currently have the ability to accurately
7095         // compute the length of an initializer list without
7096         // performing full type-checking of the initializer list
7097         // (since we have to determine where braces are implicitly
7098         // introduced and such).  So, we fall back to making the array
7099         // type a dependently-sized array type with no specified
7100         // bound.
7101         if (isa<InitListExpr>((Expr *)Args[0])) {
7102           SourceRange Brackets;
7103
7104           // Scavange the location of the brackets from the entity, if we can.
7105           if (auto *DD = dyn_cast_or_null<DeclaratorDecl>(Entity.getDecl())) {
7106             if (TypeSourceInfo *TInfo = DD->getTypeSourceInfo()) {
7107               TypeLoc TL = TInfo->getTypeLoc();
7108               if (IncompleteArrayTypeLoc ArrayLoc =
7109                       TL.getAs<IncompleteArrayTypeLoc>())
7110                 Brackets = ArrayLoc.getBracketsRange();
7111             }
7112           }
7113
7114           *ResultType
7115             = S.Context.getDependentSizedArrayType(ArrayT->getElementType(),
7116                                                    /*NumElts=*/nullptr,
7117                                                    ArrayT->getSizeModifier(),
7118                                        ArrayT->getIndexTypeCVRQualifiers(),
7119                                                    Brackets);
7120         }
7121
7122       }
7123     }
7124     if (Kind.getKind() == InitializationKind::IK_Direct &&
7125         !Kind.isExplicitCast()) {
7126       // Rebuild the ParenListExpr.
7127       SourceRange ParenRange = Kind.getParenOrBraceRange();
7128       return S.ActOnParenListExpr(ParenRange.getBegin(), ParenRange.getEnd(),
7129                                   Args);
7130     }
7131     assert(Kind.getKind() == InitializationKind::IK_Copy ||
7132            Kind.isExplicitCast() ||
7133            Kind.getKind() == InitializationKind::IK_DirectList);
7134     return ExprResult(Args[0]);
7135   }
7136
7137   // No steps means no initialization.
7138   if (Steps.empty())
7139     return ExprResult((Expr *)nullptr);
7140
7141   if (S.getLangOpts().CPlusPlus11 && Entity.getType()->isReferenceType() &&
7142       Args.size() == 1 && isa<InitListExpr>(Args[0]) &&
7143       !Entity.isParameterKind()) {
7144     // Produce a C++98 compatibility warning if we are initializing a reference
7145     // from an initializer list. For parameters, we produce a better warning
7146     // elsewhere.
7147     Expr *Init = Args[0];
7148     S.Diag(Init->getLocStart(), diag::warn_cxx98_compat_reference_list_init)
7149       << Init->getSourceRange();
7150   }
7151
7152   // OpenCL v2.0 s6.13.11.1. atomic variables can be initialized in global scope
7153   QualType ETy = Entity.getType();
7154   Qualifiers TyQualifiers = ETy.getQualifiers();
7155   bool HasGlobalAS = TyQualifiers.hasAddressSpace() &&
7156                      TyQualifiers.getAddressSpace() == LangAS::opencl_global;
7157
7158   if (S.getLangOpts().OpenCLVersion >= 200 &&
7159       ETy->isAtomicType() && !HasGlobalAS &&
7160       Entity.getKind() == InitializedEntity::EK_Variable && Args.size() > 0) {
7161     S.Diag(Args[0]->getLocStart(), diag::err_opencl_atomic_init) << 1 <<
7162     SourceRange(Entity.getDecl()->getLocStart(), Args[0]->getLocEnd());
7163     return ExprError();
7164   }
7165
7166   QualType DestType = Entity.getType().getNonReferenceType();
7167   // FIXME: Ugly hack around the fact that Entity.getType() is not
7168   // the same as Entity.getDecl()->getType() in cases involving type merging,
7169   //  and we want latter when it makes sense.
7170   if (ResultType)
7171     *ResultType = Entity.getDecl() ? Entity.getDecl()->getType() :
7172                                      Entity.getType();
7173
7174   ExprResult CurInit((Expr *)nullptr);
7175   SmallVector<Expr*, 4> ArrayLoopCommonExprs;
7176
7177   // For initialization steps that start with a single initializer,
7178   // grab the only argument out the Args and place it into the "current"
7179   // initializer.
7180   switch (Steps.front().Kind) {
7181   case SK_ResolveAddressOfOverloadedFunction:
7182   case SK_CastDerivedToBaseRValue:
7183   case SK_CastDerivedToBaseXValue:
7184   case SK_CastDerivedToBaseLValue:
7185   case SK_BindReference:
7186   case SK_BindReferenceToTemporary:
7187   case SK_FinalCopy:
7188   case SK_ExtraneousCopyToTemporary:
7189   case SK_UserConversion:
7190   case SK_QualificationConversionLValue:
7191   case SK_QualificationConversionXValue:
7192   case SK_QualificationConversionRValue:
7193   case SK_AtomicConversion:
7194   case SK_LValueToRValue:
7195   case SK_ConversionSequence:
7196   case SK_ConversionSequenceNoNarrowing:
7197   case SK_ListInitialization:
7198   case SK_UnwrapInitList:
7199   case SK_RewrapInitList:
7200   case SK_CAssignment:
7201   case SK_StringInit:
7202   case SK_ObjCObjectConversion:
7203   case SK_ArrayLoopIndex:
7204   case SK_ArrayLoopInit:
7205   case SK_ArrayInit:
7206   case SK_GNUArrayInit:
7207   case SK_ParenthesizedArrayInit:
7208   case SK_PassByIndirectCopyRestore:
7209   case SK_PassByIndirectRestore:
7210   case SK_ProduceObjCObject:
7211   case SK_StdInitializerList:
7212   case SK_OCLSamplerInit:
7213   case SK_OCLZeroEvent:
7214   case SK_OCLZeroQueue: {
7215     assert(Args.size() == 1);
7216     CurInit = Args[0];
7217     if (!CurInit.get()) return ExprError();
7218     break;
7219   }
7220
7221   case SK_ConstructorInitialization:
7222   case SK_ConstructorInitializationFromList:
7223   case SK_StdInitializerListConstructorCall:
7224   case SK_ZeroInitialization:
7225     break;
7226   }
7227
7228   // Promote from an unevaluated context to an unevaluated list context in
7229   // C++11 list-initialization; we need to instantiate entities usable in
7230   // constant expressions here in order to perform narrowing checks =(
7231   EnterExpressionEvaluationContext Evaluated(
7232       S, EnterExpressionEvaluationContext::InitList,
7233       CurInit.get() && isa<InitListExpr>(CurInit.get()));
7234
7235   // C++ [class.abstract]p2:
7236   //   no objects of an abstract class can be created except as subobjects
7237   //   of a class derived from it
7238   auto checkAbstractType = [&](QualType T) -> bool {
7239     if (Entity.getKind() == InitializedEntity::EK_Base ||
7240         Entity.getKind() == InitializedEntity::EK_Delegating)
7241       return false;
7242     return S.RequireNonAbstractType(Kind.getLocation(), T,
7243                                     diag::err_allocation_of_abstract_type);
7244   };
7245
7246   // Walk through the computed steps for the initialization sequence,
7247   // performing the specified conversions along the way.
7248   bool ConstructorInitRequiresZeroInit = false;
7249   for (step_iterator Step = step_begin(), StepEnd = step_end();
7250        Step != StepEnd; ++Step) {
7251     if (CurInit.isInvalid())
7252       return ExprError();
7253
7254     QualType SourceType = CurInit.get() ? CurInit.get()->getType() : QualType();
7255
7256     switch (Step->Kind) {
7257     case SK_ResolveAddressOfOverloadedFunction:
7258       // Overload resolution determined which function invoke; update the
7259       // initializer to reflect that choice.
7260       S.CheckAddressOfMemberAccess(CurInit.get(), Step->Function.FoundDecl);
7261       if (S.DiagnoseUseOfDecl(Step->Function.FoundDecl, Kind.getLocation()))
7262         return ExprError();
7263       CurInit = S.FixOverloadedFunctionReference(CurInit,
7264                                                  Step->Function.FoundDecl,
7265                                                  Step->Function.Function);
7266       break;
7267
7268     case SK_CastDerivedToBaseRValue:
7269     case SK_CastDerivedToBaseXValue:
7270     case SK_CastDerivedToBaseLValue: {
7271       // We have a derived-to-base cast that produces either an rvalue or an
7272       // lvalue. Perform that cast.
7273
7274       CXXCastPath BasePath;
7275
7276       // Casts to inaccessible base classes are allowed with C-style casts.
7277       bool IgnoreBaseAccess = Kind.isCStyleOrFunctionalCast();
7278       if (S.CheckDerivedToBaseConversion(SourceType, Step->Type,
7279                                          CurInit.get()->getLocStart(),
7280                                          CurInit.get()->getSourceRange(),
7281                                          &BasePath, IgnoreBaseAccess))
7282         return ExprError();
7283
7284       ExprValueKind VK =
7285           Step->Kind == SK_CastDerivedToBaseLValue ?
7286               VK_LValue :
7287               (Step->Kind == SK_CastDerivedToBaseXValue ?
7288                    VK_XValue :
7289                    VK_RValue);
7290       CurInit =
7291           ImplicitCastExpr::Create(S.Context, Step->Type, CK_DerivedToBase,
7292                                    CurInit.get(), &BasePath, VK);
7293       break;
7294     }
7295
7296     case SK_BindReference:
7297       // Reference binding does not have any corresponding ASTs.
7298
7299       // Check exception specifications
7300       if (S.CheckExceptionSpecCompatibility(CurInit.get(), DestType))
7301         return ExprError();
7302
7303       // We don't check for e.g. function pointers here, since address
7304       // availability checks should only occur when the function first decays
7305       // into a pointer or reference.
7306       if (CurInit.get()->getType()->isFunctionProtoType()) {
7307         if (auto *DRE = dyn_cast<DeclRefExpr>(CurInit.get()->IgnoreParens())) {
7308           if (auto *FD = dyn_cast<FunctionDecl>(DRE->getDecl())) {
7309             if (!S.checkAddressOfFunctionIsAvailable(FD, /*Complain=*/true,
7310                                                      DRE->getLocStart()))
7311               return ExprError();
7312           }
7313         }
7314       }
7315
7316       CheckForNullPointerDereference(S, CurInit.get());
7317       break;
7318
7319     case SK_BindReferenceToTemporary: {
7320       // Make sure the "temporary" is actually an rvalue.
7321       assert(CurInit.get()->isRValue() && "not a temporary");
7322
7323       // Check exception specifications
7324       if (S.CheckExceptionSpecCompatibility(CurInit.get(), DestType))
7325         return ExprError();
7326
7327       // Materialize the temporary into memory.
7328       MaterializeTemporaryExpr *MTE = S.CreateMaterializeTemporaryExpr(
7329           Step->Type, CurInit.get(), Entity.getType()->isLValueReferenceType());
7330       CurInit = MTE;
7331
7332       // If we're extending this temporary to automatic storage duration -- we
7333       // need to register its cleanup during the full-expression's cleanups.
7334       if (MTE->getStorageDuration() == SD_Automatic &&
7335           MTE->getType().isDestructedType())
7336         S.Cleanup.setExprNeedsCleanups(true);
7337       break;
7338     }
7339
7340     case SK_FinalCopy:
7341       if (checkAbstractType(Step->Type))
7342         return ExprError();
7343
7344       // If the overall initialization is initializing a temporary, we already
7345       // bound our argument if it was necessary to do so. If not (if we're
7346       // ultimately initializing a non-temporary), our argument needs to be
7347       // bound since it's initializing a function parameter.
7348       // FIXME: This is a mess. Rationalize temporary destruction.
7349       if (!shouldBindAsTemporary(Entity))
7350         CurInit = S.MaybeBindToTemporary(CurInit.get());
7351       CurInit = CopyObject(S, Step->Type, Entity, CurInit,
7352                            /*IsExtraneousCopy=*/false);
7353       break;
7354
7355     case SK_ExtraneousCopyToTemporary:
7356       CurInit = CopyObject(S, Step->Type, Entity, CurInit,
7357                            /*IsExtraneousCopy=*/true);
7358       break;
7359
7360     case SK_UserConversion: {
7361       // We have a user-defined conversion that invokes either a constructor
7362       // or a conversion function.
7363       CastKind CastKind;
7364       FunctionDecl *Fn = Step->Function.Function;
7365       DeclAccessPair FoundFn = Step->Function.FoundDecl;
7366       bool HadMultipleCandidates = Step->Function.HadMultipleCandidates;
7367       bool CreatedObject = false;
7368       if (CXXConstructorDecl *Constructor = dyn_cast<CXXConstructorDecl>(Fn)) {
7369         // Build a call to the selected constructor.
7370         SmallVector<Expr*, 8> ConstructorArgs;
7371         SourceLocation Loc = CurInit.get()->getLocStart();
7372
7373         // Determine the arguments required to actually perform the constructor
7374         // call.
7375         Expr *Arg = CurInit.get();
7376         if (S.CompleteConstructorCall(Constructor,
7377                                       MultiExprArg(&Arg, 1),
7378                                       Loc, ConstructorArgs))
7379           return ExprError();
7380
7381         // Build an expression that constructs a temporary.
7382         CurInit = S.BuildCXXConstructExpr(Loc, Step->Type,
7383                                           FoundFn, Constructor,
7384                                           ConstructorArgs,
7385                                           HadMultipleCandidates,
7386                                           /*ListInit*/ false,
7387                                           /*StdInitListInit*/ false,
7388                                           /*ZeroInit*/ false,
7389                                           CXXConstructExpr::CK_Complete,
7390                                           SourceRange());
7391         if (CurInit.isInvalid())
7392           return ExprError();
7393
7394         S.CheckConstructorAccess(Kind.getLocation(), Constructor, FoundFn,
7395                                  Entity);
7396         if (S.DiagnoseUseOfDecl(FoundFn, Kind.getLocation()))
7397           return ExprError();
7398
7399         CastKind = CK_ConstructorConversion;
7400         CreatedObject = true;
7401       } else {
7402         // Build a call to the conversion function.
7403         CXXConversionDecl *Conversion = cast<CXXConversionDecl>(Fn);
7404         S.CheckMemberOperatorAccess(Kind.getLocation(), CurInit.get(), nullptr,
7405                                     FoundFn);
7406         if (S.DiagnoseUseOfDecl(FoundFn, Kind.getLocation()))
7407           return ExprError();
7408
7409         CurInit = S.BuildCXXMemberCallExpr(CurInit.get(), FoundFn, Conversion,
7410                                            HadMultipleCandidates);
7411         if (CurInit.isInvalid())
7412           return ExprError();
7413
7414         CastKind = CK_UserDefinedConversion;
7415         CreatedObject = Conversion->getReturnType()->isRecordType();
7416       }
7417
7418       if (CreatedObject && checkAbstractType(CurInit.get()->getType()))
7419         return ExprError();
7420
7421       CurInit = ImplicitCastExpr::Create(S.Context, CurInit.get()->getType(),
7422                                          CastKind, CurInit.get(), nullptr,
7423                                          CurInit.get()->getValueKind());
7424
7425       if (shouldBindAsTemporary(Entity))
7426         // The overall entity is temporary, so this expression should be
7427         // destroyed at the end of its full-expression.
7428         CurInit = S.MaybeBindToTemporary(CurInit.getAs<Expr>());
7429       else if (CreatedObject && shouldDestroyEntity(Entity)) {
7430         // The object outlasts the full-expression, but we need to prepare for
7431         // a destructor being run on it.
7432         // FIXME: It makes no sense to do this here. This should happen
7433         // regardless of how we initialized the entity.
7434         QualType T = CurInit.get()->getType();
7435         if (const RecordType *Record = T->getAs<RecordType>()) {
7436           CXXDestructorDecl *Destructor
7437             = S.LookupDestructor(cast<CXXRecordDecl>(Record->getDecl()));
7438           S.CheckDestructorAccess(CurInit.get()->getLocStart(), Destructor,
7439                                   S.PDiag(diag::err_access_dtor_temp) << T);
7440           S.MarkFunctionReferenced(CurInit.get()->getLocStart(), Destructor);
7441           if (S.DiagnoseUseOfDecl(Destructor, CurInit.get()->getLocStart()))
7442             return ExprError();
7443         }
7444       }
7445       break;
7446     }
7447
7448     case SK_QualificationConversionLValue:
7449     case SK_QualificationConversionXValue:
7450     case SK_QualificationConversionRValue: {
7451       // Perform a qualification conversion; these can never go wrong.
7452       ExprValueKind VK =
7453           Step->Kind == SK_QualificationConversionLValue ?
7454               VK_LValue :
7455               (Step->Kind == SK_QualificationConversionXValue ?
7456                    VK_XValue :
7457                    VK_RValue);
7458       CurInit = S.ImpCastExprToType(CurInit.get(), Step->Type, CK_NoOp, VK);
7459       break;
7460     }
7461
7462     case SK_AtomicConversion: {
7463       assert(CurInit.get()->isRValue() && "cannot convert glvalue to atomic");
7464       CurInit = S.ImpCastExprToType(CurInit.get(), Step->Type,
7465                                     CK_NonAtomicToAtomic, VK_RValue);
7466       break;
7467     }
7468
7469     case SK_LValueToRValue: {
7470       assert(CurInit.get()->isGLValue() && "cannot load from a prvalue");
7471       CurInit = ImplicitCastExpr::Create(S.Context, Step->Type,
7472                                          CK_LValueToRValue, CurInit.get(),
7473                                          /*BasePath=*/nullptr, VK_RValue);
7474       break;
7475     }
7476
7477     case SK_ConversionSequence:
7478     case SK_ConversionSequenceNoNarrowing: {
7479       Sema::CheckedConversionKind CCK
7480         = Kind.isCStyleCast()? Sema::CCK_CStyleCast
7481         : Kind.isFunctionalCast()? Sema::CCK_FunctionalCast
7482         : Kind.isExplicitCast()? Sema::CCK_OtherCast
7483         : Sema::CCK_ImplicitConversion;
7484       ExprResult CurInitExprRes =
7485         S.PerformImplicitConversion(CurInit.get(), Step->Type, *Step->ICS,
7486                                     getAssignmentAction(Entity), CCK);
7487       if (CurInitExprRes.isInvalid())
7488         return ExprError();
7489
7490       S.DiscardMisalignedMemberAddress(Step->Type.getTypePtr(), CurInit.get());
7491
7492       CurInit = CurInitExprRes;
7493
7494       if (Step->Kind == SK_ConversionSequenceNoNarrowing &&
7495           S.getLangOpts().CPlusPlus)
7496         DiagnoseNarrowingInInitList(S, *Step->ICS, SourceType, Entity.getType(),
7497                                     CurInit.get());
7498
7499       break;
7500     }
7501
7502     case SK_ListInitialization: {
7503       if (checkAbstractType(Step->Type))
7504         return ExprError();
7505
7506       InitListExpr *InitList = cast<InitListExpr>(CurInit.get());
7507       // If we're not initializing the top-level entity, we need to create an
7508       // InitializeTemporary entity for our target type.
7509       QualType Ty = Step->Type;
7510       bool IsTemporary = !S.Context.hasSameType(Entity.getType(), Ty);
7511       InitializedEntity TempEntity = InitializedEntity::InitializeTemporary(Ty);
7512       InitializedEntity InitEntity = IsTemporary ? TempEntity : Entity;
7513       InitListChecker PerformInitList(S, InitEntity,
7514           InitList, Ty, /*VerifyOnly=*/false,
7515           /*TreatUnavailableAsInvalid=*/false);
7516       if (PerformInitList.HadError())
7517         return ExprError();
7518
7519       // Hack: We must update *ResultType if available in order to set the
7520       // bounds of arrays, e.g. in 'int ar[] = {1, 2, 3};'.
7521       // Worst case: 'const int (&arref)[] = {1, 2, 3};'.
7522       if (ResultType &&
7523           ResultType->getNonReferenceType()->isIncompleteArrayType()) {
7524         if ((*ResultType)->isRValueReferenceType())
7525           Ty = S.Context.getRValueReferenceType(Ty);
7526         else if ((*ResultType)->isLValueReferenceType())
7527           Ty = S.Context.getLValueReferenceType(Ty,
7528             (*ResultType)->getAs<LValueReferenceType>()->isSpelledAsLValue());
7529         *ResultType = Ty;
7530       }
7531
7532       InitListExpr *StructuredInitList =
7533           PerformInitList.getFullyStructuredList();
7534       CurInit.get();
7535       CurInit = shouldBindAsTemporary(InitEntity)
7536           ? S.MaybeBindToTemporary(StructuredInitList)
7537           : StructuredInitList;
7538       break;
7539     }
7540
7541     case SK_ConstructorInitializationFromList: {
7542       if (checkAbstractType(Step->Type))
7543         return ExprError();
7544
7545       // When an initializer list is passed for a parameter of type "reference
7546       // to object", we don't get an EK_Temporary entity, but instead an
7547       // EK_Parameter entity with reference type.
7548       // FIXME: This is a hack. What we really should do is create a user
7549       // conversion step for this case, but this makes it considerably more
7550       // complicated. For now, this will do.
7551       InitializedEntity TempEntity = InitializedEntity::InitializeTemporary(
7552                                         Entity.getType().getNonReferenceType());
7553       bool UseTemporary = Entity.getType()->isReferenceType();
7554       assert(Args.size() == 1 && "expected a single argument for list init");
7555       InitListExpr *InitList = cast<InitListExpr>(Args[0]);
7556       S.Diag(InitList->getExprLoc(), diag::warn_cxx98_compat_ctor_list_init)
7557         << InitList->getSourceRange();
7558       MultiExprArg Arg(InitList->getInits(), InitList->getNumInits());
7559       CurInit = PerformConstructorInitialization(S, UseTemporary ? TempEntity :
7560                                                                    Entity,
7561                                                  Kind, Arg, *Step,
7562                                                ConstructorInitRequiresZeroInit,
7563                                                /*IsListInitialization*/true,
7564                                                /*IsStdInitListInit*/false,
7565                                                InitList->getLBraceLoc(),
7566                                                InitList->getRBraceLoc());
7567       break;
7568     }
7569
7570     case SK_UnwrapInitList:
7571       CurInit = cast<InitListExpr>(CurInit.get())->getInit(0);
7572       break;
7573
7574     case SK_RewrapInitList: {
7575       Expr *E = CurInit.get();
7576       InitListExpr *Syntactic = Step->WrappingSyntacticList;
7577       InitListExpr *ILE = new (S.Context) InitListExpr(S.Context,
7578           Syntactic->getLBraceLoc(), E, Syntactic->getRBraceLoc());
7579       ILE->setSyntacticForm(Syntactic);
7580       ILE->setType(E->getType());
7581       ILE->setValueKind(E->getValueKind());
7582       CurInit = ILE;
7583       break;
7584     }
7585
7586     case SK_ConstructorInitialization:
7587     case SK_StdInitializerListConstructorCall: {
7588       if (checkAbstractType(Step->Type))
7589         return ExprError();
7590
7591       // When an initializer list is passed for a parameter of type "reference
7592       // to object", we don't get an EK_Temporary entity, but instead an
7593       // EK_Parameter entity with reference type.
7594       // FIXME: This is a hack. What we really should do is create a user
7595       // conversion step for this case, but this makes it considerably more
7596       // complicated. For now, this will do.
7597       InitializedEntity TempEntity = InitializedEntity::InitializeTemporary(
7598                                         Entity.getType().getNonReferenceType());
7599       bool UseTemporary = Entity.getType()->isReferenceType();
7600       bool IsStdInitListInit =
7601           Step->Kind == SK_StdInitializerListConstructorCall;
7602       Expr *Source = CurInit.get();
7603       SourceRange Range = Kind.hasParenOrBraceRange()
7604                               ? Kind.getParenOrBraceRange()
7605                               : SourceRange();
7606       CurInit = PerformConstructorInitialization(
7607           S, UseTemporary ? TempEntity : Entity, Kind,
7608           Source ? MultiExprArg(Source) : Args, *Step,
7609           ConstructorInitRequiresZeroInit,
7610           /*IsListInitialization*/ IsStdInitListInit,
7611           /*IsStdInitListInitialization*/ IsStdInitListInit,
7612           /*LBraceLoc*/ Range.getBegin(),
7613           /*RBraceLoc*/ Range.getEnd());
7614       break;
7615     }
7616
7617     case SK_ZeroInitialization: {
7618       step_iterator NextStep = Step;
7619       ++NextStep;
7620       if (NextStep != StepEnd &&
7621           (NextStep->Kind == SK_ConstructorInitialization ||
7622            NextStep->Kind == SK_ConstructorInitializationFromList)) {
7623         // The need for zero-initialization is recorded directly into
7624         // the call to the object's constructor within the next step.
7625         ConstructorInitRequiresZeroInit = true;
7626       } else if (Kind.getKind() == InitializationKind::IK_Value &&
7627                  S.getLangOpts().CPlusPlus &&
7628                  !Kind.isImplicitValueInit()) {
7629         TypeSourceInfo *TSInfo = Entity.getTypeSourceInfo();
7630         if (!TSInfo)
7631           TSInfo = S.Context.getTrivialTypeSourceInfo(Step->Type,
7632                                                     Kind.getRange().getBegin());
7633
7634         CurInit = new (S.Context) CXXScalarValueInitExpr(
7635             Entity.getType().getNonLValueExprType(S.Context), TSInfo,
7636             Kind.getRange().getEnd());
7637       } else {
7638         CurInit = new (S.Context) ImplicitValueInitExpr(Step->Type);
7639       }
7640       break;
7641     }
7642
7643     case SK_CAssignment: {
7644       QualType SourceType = CurInit.get()->getType();
7645       // Save off the initial CurInit in case we need to emit a diagnostic
7646       ExprResult InitialCurInit = CurInit;
7647       ExprResult Result = CurInit;
7648       Sema::AssignConvertType ConvTy =
7649         S.CheckSingleAssignmentConstraints(Step->Type, Result, true,
7650             Entity.getKind() == InitializedEntity::EK_Parameter_CF_Audited);
7651       if (Result.isInvalid())
7652         return ExprError();
7653       CurInit = Result;
7654
7655       // If this is a call, allow conversion to a transparent union.
7656       ExprResult CurInitExprRes = CurInit;
7657       if (ConvTy != Sema::Compatible &&
7658           Entity.isParameterKind() &&
7659           S.CheckTransparentUnionArgumentConstraints(Step->Type, CurInitExprRes)
7660             == Sema::Compatible)
7661         ConvTy = Sema::Compatible;
7662       if (CurInitExprRes.isInvalid())
7663         return ExprError();
7664       CurInit = CurInitExprRes;
7665
7666       bool Complained;
7667       if (S.DiagnoseAssignmentResult(ConvTy, Kind.getLocation(),
7668                                      Step->Type, SourceType,
7669                                      InitialCurInit.get(),
7670                                      getAssignmentAction(Entity, true),
7671                                      &Complained)) {
7672         PrintInitLocationNote(S, Entity);
7673         return ExprError();
7674       } else if (Complained)
7675         PrintInitLocationNote(S, Entity);
7676       break;
7677     }
7678
7679     case SK_StringInit: {
7680       QualType Ty = Step->Type;
7681       CheckStringInit(CurInit.get(), ResultType ? *ResultType : Ty,
7682                       S.Context.getAsArrayType(Ty), S);
7683       break;
7684     }
7685
7686     case SK_ObjCObjectConversion:
7687       CurInit = S.ImpCastExprToType(CurInit.get(), Step->Type,
7688                           CK_ObjCObjectLValueCast,
7689                           CurInit.get()->getValueKind());
7690       break;
7691
7692     case SK_ArrayLoopIndex: {
7693       Expr *Cur = CurInit.get();
7694       Expr *BaseExpr = new (S.Context)
7695           OpaqueValueExpr(Cur->getExprLoc(), Cur->getType(),
7696                           Cur->getValueKind(), Cur->getObjectKind(), Cur);
7697       Expr *IndexExpr =
7698           new (S.Context) ArrayInitIndexExpr(S.Context.getSizeType());
7699       CurInit = S.CreateBuiltinArraySubscriptExpr(
7700           BaseExpr, Kind.getLocation(), IndexExpr, Kind.getLocation());
7701       ArrayLoopCommonExprs.push_back(BaseExpr);
7702       break;
7703     }
7704
7705     case SK_ArrayLoopInit: {
7706       assert(!ArrayLoopCommonExprs.empty() &&
7707              "mismatched SK_ArrayLoopIndex and SK_ArrayLoopInit");
7708       Expr *Common = ArrayLoopCommonExprs.pop_back_val();
7709       CurInit = new (S.Context) ArrayInitLoopExpr(Step->Type, Common,
7710                                                   CurInit.get());
7711       break;
7712     }
7713
7714     case SK_GNUArrayInit:
7715       // Okay: we checked everything before creating this step. Note that
7716       // this is a GNU extension.
7717       S.Diag(Kind.getLocation(), diag::ext_array_init_copy)
7718         << Step->Type << CurInit.get()->getType()
7719         << CurInit.get()->getSourceRange();
7720       LLVM_FALLTHROUGH;
7721     case SK_ArrayInit:
7722       // If the destination type is an incomplete array type, update the
7723       // type accordingly.
7724       if (ResultType) {
7725         if (const IncompleteArrayType *IncompleteDest
7726                            = S.Context.getAsIncompleteArrayType(Step->Type)) {
7727           if (const ConstantArrayType *ConstantSource
7728                  = S.Context.getAsConstantArrayType(CurInit.get()->getType())) {
7729             *ResultType = S.Context.getConstantArrayType(
7730                                              IncompleteDest->getElementType(),
7731                                              ConstantSource->getSize(),
7732                                              ArrayType::Normal, 0);
7733           }
7734         }
7735       }
7736       break;
7737
7738     case SK_ParenthesizedArrayInit:
7739       // Okay: we checked everything before creating this step. Note that
7740       // this is a GNU extension.
7741       S.Diag(Kind.getLocation(), diag::ext_array_init_parens)
7742         << CurInit.get()->getSourceRange();
7743       break;
7744
7745     case SK_PassByIndirectCopyRestore:
7746     case SK_PassByIndirectRestore:
7747       checkIndirectCopyRestoreSource(S, CurInit.get());
7748       CurInit = new (S.Context) ObjCIndirectCopyRestoreExpr(
7749           CurInit.get(), Step->Type,
7750           Step->Kind == SK_PassByIndirectCopyRestore);
7751       break;
7752
7753     case SK_ProduceObjCObject:
7754       CurInit =
7755           ImplicitCastExpr::Create(S.Context, Step->Type, CK_ARCProduceObject,
7756                                    CurInit.get(), nullptr, VK_RValue);
7757       break;
7758
7759     case SK_StdInitializerList: {
7760       S.Diag(CurInit.get()->getExprLoc(),
7761              diag::warn_cxx98_compat_initializer_list_init)
7762         << CurInit.get()->getSourceRange();
7763
7764       // Materialize the temporary into memory.
7765       MaterializeTemporaryExpr *MTE = S.CreateMaterializeTemporaryExpr(
7766           CurInit.get()->getType(), CurInit.get(),
7767           /*BoundToLvalueReference=*/false);
7768
7769       // Wrap it in a construction of a std::initializer_list<T>.
7770       CurInit = new (S.Context) CXXStdInitializerListExpr(Step->Type, MTE);
7771
7772       // Bind the result, in case the library has given initializer_list a
7773       // non-trivial destructor.
7774       if (shouldBindAsTemporary(Entity))
7775         CurInit = S.MaybeBindToTemporary(CurInit.get());
7776       break;
7777     }
7778
7779     case SK_OCLSamplerInit: {
7780       // Sampler initialzation have 5 cases:
7781       //   1. function argument passing
7782       //      1a. argument is a file-scope variable
7783       //      1b. argument is a function-scope variable
7784       //      1c. argument is one of caller function's parameters
7785       //   2. variable initialization
7786       //      2a. initializing a file-scope variable
7787       //      2b. initializing a function-scope variable
7788       //
7789       // For file-scope variables, since they cannot be initialized by function
7790       // call of __translate_sampler_initializer in LLVM IR, their references
7791       // need to be replaced by a cast from their literal initializers to
7792       // sampler type. Since sampler variables can only be used in function
7793       // calls as arguments, we only need to replace them when handling the
7794       // argument passing.
7795       assert(Step->Type->isSamplerT() &&
7796              "Sampler initialization on non-sampler type.");
7797       Expr *Init = CurInit.get();
7798       QualType SourceType = Init->getType();
7799       // Case 1
7800       if (Entity.isParameterKind()) {
7801         if (!SourceType->isSamplerT() && !SourceType->isIntegerType()) {
7802           S.Diag(Kind.getLocation(), diag::err_sampler_argument_required)
7803             << SourceType;
7804           break;
7805         } else if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(Init)) {
7806           auto Var = cast<VarDecl>(DRE->getDecl());
7807           // Case 1b and 1c
7808           // No cast from integer to sampler is needed.
7809           if (!Var->hasGlobalStorage()) {
7810             CurInit = ImplicitCastExpr::Create(S.Context, Step->Type,
7811                                                CK_LValueToRValue, Init,
7812                                                /*BasePath=*/nullptr, VK_RValue);
7813             break;
7814           }
7815           // Case 1a
7816           // For function call with a file-scope sampler variable as argument,
7817           // get the integer literal.
7818           // Do not diagnose if the file-scope variable does not have initializer
7819           // since this has already been diagnosed when parsing the variable
7820           // declaration.
7821           if (!Var->getInit() || !isa<ImplicitCastExpr>(Var->getInit()))
7822             break;
7823           Init = cast<ImplicitCastExpr>(const_cast<Expr*>(
7824             Var->getInit()))->getSubExpr();
7825           SourceType = Init->getType();
7826         }
7827       } else {
7828         // Case 2
7829         // Check initializer is 32 bit integer constant.
7830         // If the initializer is taken from global variable, do not diagnose since
7831         // this has already been done when parsing the variable declaration.
7832         if (!Init->isConstantInitializer(S.Context, false))
7833           break;
7834
7835         if (!SourceType->isIntegerType() ||
7836             32 != S.Context.getIntWidth(SourceType)) {
7837           S.Diag(Kind.getLocation(), diag::err_sampler_initializer_not_integer)
7838             << SourceType;
7839           break;
7840         }
7841
7842         llvm::APSInt Result;
7843         Init->EvaluateAsInt(Result, S.Context);
7844         const uint64_t SamplerValue = Result.getLimitedValue();
7845         // 32-bit value of sampler's initializer is interpreted as
7846         // bit-field with the following structure:
7847         // |unspecified|Filter|Addressing Mode| Normalized Coords|
7848         // |31        6|5    4|3             1|                 0|
7849         // This structure corresponds to enum values of sampler properties
7850         // defined in SPIR spec v1.2 and also opencl-c.h
7851         unsigned AddressingMode  = (0x0E & SamplerValue) >> 1;
7852         unsigned FilterMode      = (0x30 & SamplerValue) >> 4;
7853         if (FilterMode != 1 && FilterMode != 2)
7854           S.Diag(Kind.getLocation(),
7855                  diag::warn_sampler_initializer_invalid_bits)
7856                  << "Filter Mode";
7857         if (AddressingMode > 4)
7858           S.Diag(Kind.getLocation(),
7859                  diag::warn_sampler_initializer_invalid_bits)
7860                  << "Addressing Mode";
7861       }
7862
7863       // Cases 1a, 2a and 2b
7864       // Insert cast from integer to sampler.
7865       CurInit = S.ImpCastExprToType(Init, S.Context.OCLSamplerTy,
7866                                       CK_IntToOCLSampler);
7867       break;
7868     }
7869     case SK_OCLZeroEvent: {
7870       assert(Step->Type->isEventT() &&
7871              "Event initialization on non-event type.");
7872
7873       CurInit = S.ImpCastExprToType(CurInit.get(), Step->Type,
7874                                     CK_ZeroToOCLEvent,
7875                                     CurInit.get()->getValueKind());
7876       break;
7877     }
7878     case SK_OCLZeroQueue: {
7879       assert(Step->Type->isQueueT() &&
7880              "Event initialization on non queue type.");
7881
7882       CurInit = S.ImpCastExprToType(CurInit.get(), Step->Type,
7883                                     CK_ZeroToOCLQueue,
7884                                     CurInit.get()->getValueKind());
7885       break;
7886     }
7887     }
7888   }
7889
7890   // Check whether the initializer has a shorter lifetime than the initialized
7891   // entity, and if not, either lifetime-extend or warn as appropriate.
7892   if (auto *Init = CurInit.get())
7893     S.checkInitializerLifetime(Entity, Init);
7894
7895   // Diagnose non-fatal problems with the completed initialization.
7896   if (Entity.getKind() == InitializedEntity::EK_Member &&
7897       cast<FieldDecl>(Entity.getDecl())->isBitField())
7898     S.CheckBitFieldInitialization(Kind.getLocation(),
7899                                   cast<FieldDecl>(Entity.getDecl()),
7900                                   CurInit.get());
7901
7902   // Check for std::move on construction.
7903   if (const Expr *E = CurInit.get()) {
7904     CheckMoveOnConstruction(S, E,
7905                             Entity.getKind() == InitializedEntity::EK_Result);
7906   }
7907
7908   return CurInit;
7909 }
7910
7911 /// Somewhere within T there is an uninitialized reference subobject.
7912 /// Dig it out and diagnose it.
7913 static bool DiagnoseUninitializedReference(Sema &S, SourceLocation Loc,
7914                                            QualType T) {
7915   if (T->isReferenceType()) {
7916     S.Diag(Loc, diag::err_reference_without_init)
7917       << T.getNonReferenceType();
7918     return true;
7919   }
7920
7921   CXXRecordDecl *RD = T->getBaseElementTypeUnsafe()->getAsCXXRecordDecl();
7922   if (!RD || !RD->hasUninitializedReferenceMember())
7923     return false;
7924
7925   for (const auto *FI : RD->fields()) {
7926     if (FI->isUnnamedBitfield())
7927       continue;
7928
7929     if (DiagnoseUninitializedReference(S, FI->getLocation(), FI->getType())) {
7930       S.Diag(Loc, diag::note_value_initialization_here) << RD;
7931       return true;
7932     }
7933   }
7934
7935   for (const auto &BI : RD->bases()) {
7936     if (DiagnoseUninitializedReference(S, BI.getLocStart(), BI.getType())) {
7937       S.Diag(Loc, diag::note_value_initialization_here) << RD;
7938       return true;
7939     }
7940   }
7941
7942   return false;
7943 }
7944
7945
7946 //===----------------------------------------------------------------------===//
7947 // Diagnose initialization failures
7948 //===----------------------------------------------------------------------===//
7949
7950 /// Emit notes associated with an initialization that failed due to a
7951 /// "simple" conversion failure.
7952 static void emitBadConversionNotes(Sema &S, const InitializedEntity &entity,
7953                                    Expr *op) {
7954   QualType destType = entity.getType();
7955   if (destType.getNonReferenceType()->isObjCObjectPointerType() &&
7956       op->getType()->isObjCObjectPointerType()) {
7957
7958     // Emit a possible note about the conversion failing because the
7959     // operand is a message send with a related result type.
7960     S.EmitRelatedResultTypeNote(op);
7961
7962     // Emit a possible note about a return failing because we're
7963     // expecting a related result type.
7964     if (entity.getKind() == InitializedEntity::EK_Result)
7965       S.EmitRelatedResultTypeNoteForReturn(destType);
7966   }
7967 }
7968
7969 static void diagnoseListInit(Sema &S, const InitializedEntity &Entity,
7970                              InitListExpr *InitList) {
7971   QualType DestType = Entity.getType();
7972
7973   QualType E;
7974   if (S.getLangOpts().CPlusPlus11 && S.isStdInitializerList(DestType, &E)) {
7975     QualType ArrayType = S.Context.getConstantArrayType(
7976         E.withConst(),
7977         llvm::APInt(S.Context.getTypeSize(S.Context.getSizeType()),
7978                     InitList->getNumInits()),
7979         clang::ArrayType::Normal, 0);
7980     InitializedEntity HiddenArray =
7981         InitializedEntity::InitializeTemporary(ArrayType);
7982     return diagnoseListInit(S, HiddenArray, InitList);
7983   }
7984
7985   if (DestType->isReferenceType()) {
7986     // A list-initialization failure for a reference means that we tried to
7987     // create a temporary of the inner type (per [dcl.init.list]p3.6) and the
7988     // inner initialization failed.
7989     QualType T = DestType->getAs<ReferenceType>()->getPointeeType();
7990     diagnoseListInit(S, InitializedEntity::InitializeTemporary(T), InitList);
7991     SourceLocation Loc = InitList->getLocStart();
7992     if (auto *D = Entity.getDecl())
7993       Loc = D->getLocation();
7994     S.Diag(Loc, diag::note_in_reference_temporary_list_initializer) << T;
7995     return;
7996   }
7997
7998   InitListChecker DiagnoseInitList(S, Entity, InitList, DestType,
7999                                    /*VerifyOnly=*/false,
8000                                    /*TreatUnavailableAsInvalid=*/false);
8001   assert(DiagnoseInitList.HadError() &&
8002          "Inconsistent init list check result.");
8003 }
8004
8005 bool InitializationSequence::Diagnose(Sema &S,
8006                                       const InitializedEntity &Entity,
8007                                       const InitializationKind &Kind,
8008                                       ArrayRef<Expr *> Args) {
8009   if (!Failed())
8010     return false;
8011
8012   // When we want to diagnose only one element of a braced-init-list,
8013   // we need to factor it out.
8014   Expr *OnlyArg;
8015   if (Args.size() == 1) {
8016     auto *List = dyn_cast<InitListExpr>(Args[0]);
8017     if (List && List->getNumInits() == 1)
8018       OnlyArg = List->getInit(0);
8019     else
8020       OnlyArg = Args[0];
8021   }
8022   else
8023     OnlyArg = nullptr;
8024
8025   QualType DestType = Entity.getType();
8026   switch (Failure) {
8027   case FK_TooManyInitsForReference:
8028     // FIXME: Customize for the initialized entity?
8029     if (Args.empty()) {
8030       // Dig out the reference subobject which is uninitialized and diagnose it.
8031       // If this is value-initialization, this could be nested some way within
8032       // the target type.
8033       assert(Kind.getKind() == InitializationKind::IK_Value ||
8034              DestType->isReferenceType());
8035       bool Diagnosed =
8036         DiagnoseUninitializedReference(S, Kind.getLocation(), DestType);
8037       assert(Diagnosed && "couldn't find uninitialized reference to diagnose");
8038       (void)Diagnosed;
8039     } else  // FIXME: diagnostic below could be better!
8040       S.Diag(Kind.getLocation(), diag::err_reference_has_multiple_inits)
8041         << SourceRange(Args.front()->getLocStart(), Args.back()->getLocEnd());
8042     break;
8043   case FK_ParenthesizedListInitForReference:
8044     S.Diag(Kind.getLocation(), diag::err_list_init_in_parens)
8045       << 1 << Entity.getType() << Args[0]->getSourceRange();
8046     break;
8047
8048   case FK_ArrayNeedsInitList:
8049     S.Diag(Kind.getLocation(), diag::err_array_init_not_init_list) << 0;
8050     break;
8051   case FK_ArrayNeedsInitListOrStringLiteral:
8052     S.Diag(Kind.getLocation(), diag::err_array_init_not_init_list) << 1;
8053     break;
8054   case FK_ArrayNeedsInitListOrWideStringLiteral:
8055     S.Diag(Kind.getLocation(), diag::err_array_init_not_init_list) << 2;
8056     break;
8057   case FK_NarrowStringIntoWideCharArray:
8058     S.Diag(Kind.getLocation(), diag::err_array_init_narrow_string_into_wchar);
8059     break;
8060   case FK_WideStringIntoCharArray:
8061     S.Diag(Kind.getLocation(), diag::err_array_init_wide_string_into_char);
8062     break;
8063   case FK_IncompatWideStringIntoWideChar:
8064     S.Diag(Kind.getLocation(),
8065            diag::err_array_init_incompat_wide_string_into_wchar);
8066     break;
8067   case FK_PlainStringIntoUTF8Char:
8068     S.Diag(Kind.getLocation(),
8069            diag::err_array_init_plain_string_into_char8_t);
8070     S.Diag(Args.front()->getLocStart(),
8071            diag::note_array_init_plain_string_into_char8_t)
8072       << FixItHint::CreateInsertion(Args.front()->getLocStart(), "u8");
8073     break;
8074   case FK_UTF8StringIntoPlainChar:
8075     S.Diag(Kind.getLocation(),
8076            diag::err_array_init_utf8_string_into_char);
8077     break;
8078   case FK_ArrayTypeMismatch:
8079   case FK_NonConstantArrayInit:
8080     S.Diag(Kind.getLocation(),
8081            (Failure == FK_ArrayTypeMismatch
8082               ? diag::err_array_init_different_type
8083               : diag::err_array_init_non_constant_array))
8084       << DestType.getNonReferenceType()
8085       << OnlyArg->getType()
8086       << Args[0]->getSourceRange();
8087     break;
8088
8089   case FK_VariableLengthArrayHasInitializer:
8090     S.Diag(Kind.getLocation(), diag::err_variable_object_no_init)
8091       << Args[0]->getSourceRange();
8092     break;
8093
8094   case FK_AddressOfOverloadFailed: {
8095     DeclAccessPair Found;
8096     S.ResolveAddressOfOverloadedFunction(OnlyArg,
8097                                          DestType.getNonReferenceType(),
8098                                          true,
8099                                          Found);
8100     break;
8101   }
8102
8103   case FK_AddressOfUnaddressableFunction: {
8104     auto *FD = cast<FunctionDecl>(cast<DeclRefExpr>(OnlyArg)->getDecl());
8105     S.checkAddressOfFunctionIsAvailable(FD, /*Complain=*/true,
8106                                         OnlyArg->getLocStart());
8107     break;
8108   }
8109
8110   case FK_ReferenceInitOverloadFailed:
8111   case FK_UserConversionOverloadFailed:
8112     switch (FailedOverloadResult) {
8113     case OR_Ambiguous:
8114       if (Failure == FK_UserConversionOverloadFailed)
8115         S.Diag(Kind.getLocation(), diag::err_typecheck_ambiguous_condition)
8116           << OnlyArg->getType() << DestType
8117           << Args[0]->getSourceRange();
8118       else
8119         S.Diag(Kind.getLocation(), diag::err_ref_init_ambiguous)
8120           << DestType << OnlyArg->getType()
8121           << Args[0]->getSourceRange();
8122
8123       FailedCandidateSet.NoteCandidates(S, OCD_ViableCandidates, Args);
8124       break;
8125
8126     case OR_No_Viable_Function:
8127       if (!S.RequireCompleteType(Kind.getLocation(),
8128                                  DestType.getNonReferenceType(),
8129                           diag::err_typecheck_nonviable_condition_incomplete,
8130                                OnlyArg->getType(), Args[0]->getSourceRange()))
8131         S.Diag(Kind.getLocation(), diag::err_typecheck_nonviable_condition)
8132           << (Entity.getKind() == InitializedEntity::EK_Result)
8133           << OnlyArg->getType() << Args[0]->getSourceRange()
8134           << DestType.getNonReferenceType();
8135
8136       FailedCandidateSet.NoteCandidates(S, OCD_AllCandidates, Args);
8137       break;
8138
8139     case OR_Deleted: {
8140       S.Diag(Kind.getLocation(), diag::err_typecheck_deleted_function)
8141         << OnlyArg->getType() << DestType.getNonReferenceType()
8142         << Args[0]->getSourceRange();
8143       OverloadCandidateSet::iterator Best;
8144       OverloadingResult Ovl
8145         = FailedCandidateSet.BestViableFunction(S, Kind.getLocation(), Best);
8146       if (Ovl == OR_Deleted) {
8147         S.NoteDeletedFunction(Best->Function);
8148       } else {
8149         llvm_unreachable("Inconsistent overload resolution?");
8150       }
8151       break;
8152     }
8153
8154     case OR_Success:
8155       llvm_unreachable("Conversion did not fail!");
8156     }
8157     break;
8158
8159   case FK_NonConstLValueReferenceBindingToTemporary:
8160     if (isa<InitListExpr>(Args[0])) {
8161       S.Diag(Kind.getLocation(),
8162              diag::err_lvalue_reference_bind_to_initlist)
8163       << DestType.getNonReferenceType().isVolatileQualified()
8164       << DestType.getNonReferenceType()
8165       << Args[0]->getSourceRange();
8166       break;
8167     }
8168     LLVM_FALLTHROUGH;
8169
8170   case FK_NonConstLValueReferenceBindingToUnrelated:
8171     S.Diag(Kind.getLocation(),
8172            Failure == FK_NonConstLValueReferenceBindingToTemporary
8173              ? diag::err_lvalue_reference_bind_to_temporary
8174              : diag::err_lvalue_reference_bind_to_unrelated)
8175       << DestType.getNonReferenceType().isVolatileQualified()
8176       << DestType.getNonReferenceType()
8177       << OnlyArg->getType()
8178       << Args[0]->getSourceRange();
8179     break;
8180
8181   case FK_NonConstLValueReferenceBindingToBitfield: {
8182     // We don't necessarily have an unambiguous source bit-field.
8183     FieldDecl *BitField = Args[0]->getSourceBitField();
8184     S.Diag(Kind.getLocation(), diag::err_reference_bind_to_bitfield)
8185       << DestType.isVolatileQualified()
8186       << (BitField ? BitField->getDeclName() : DeclarationName())
8187       << (BitField != nullptr)
8188       << Args[0]->getSourceRange();
8189     if (BitField)
8190       S.Diag(BitField->getLocation(), diag::note_bitfield_decl);
8191     break;
8192   }
8193
8194   case FK_NonConstLValueReferenceBindingToVectorElement:
8195     S.Diag(Kind.getLocation(), diag::err_reference_bind_to_vector_element)
8196       << DestType.isVolatileQualified()
8197       << Args[0]->getSourceRange();
8198     break;
8199
8200   case FK_RValueReferenceBindingToLValue:
8201     S.Diag(Kind.getLocation(), diag::err_lvalue_to_rvalue_ref)
8202       << DestType.getNonReferenceType() << OnlyArg->getType()
8203       << Args[0]->getSourceRange();
8204     break;
8205
8206   case FK_ReferenceInitDropsQualifiers: {
8207     QualType SourceType = OnlyArg->getType();
8208     QualType NonRefType = DestType.getNonReferenceType();
8209     Qualifiers DroppedQualifiers =
8210         SourceType.getQualifiers() - NonRefType.getQualifiers();
8211
8212     S.Diag(Kind.getLocation(), diag::err_reference_bind_drops_quals)
8213       << SourceType
8214       << NonRefType
8215       << DroppedQualifiers.getCVRQualifiers()
8216       << Args[0]->getSourceRange();
8217     break;
8218   }
8219
8220   case FK_ReferenceInitFailed:
8221     S.Diag(Kind.getLocation(), diag::err_reference_bind_failed)
8222       << DestType.getNonReferenceType()
8223       << OnlyArg->isLValue()
8224       << OnlyArg->getType()
8225       << Args[0]->getSourceRange();
8226     emitBadConversionNotes(S, Entity, Args[0]);
8227     break;
8228
8229   case FK_ConversionFailed: {
8230     QualType FromType = OnlyArg->getType();
8231     PartialDiagnostic PDiag = S.PDiag(diag::err_init_conversion_failed)
8232       << (int)Entity.getKind()
8233       << DestType
8234       << OnlyArg->isLValue()
8235       << FromType
8236       << Args[0]->getSourceRange();
8237     S.HandleFunctionTypeMismatch(PDiag, FromType, DestType);
8238     S.Diag(Kind.getLocation(), PDiag);
8239     emitBadConversionNotes(S, Entity, Args[0]);
8240     break;
8241   }
8242
8243   case FK_ConversionFromPropertyFailed:
8244     // No-op. This error has already been reported.
8245     break;
8246
8247   case FK_TooManyInitsForScalar: {
8248     SourceRange R;
8249
8250     auto *InitList = dyn_cast<InitListExpr>(Args[0]);
8251     if (InitList && InitList->getNumInits() >= 1) {
8252       R = SourceRange(InitList->getInit(0)->getLocEnd(), InitList->getLocEnd());
8253     } else {
8254       assert(Args.size() > 1 && "Expected multiple initializers!");
8255       R = SourceRange(Args.front()->getLocEnd(), Args.back()->getLocEnd());
8256     }
8257
8258     R.setBegin(S.getLocForEndOfToken(R.getBegin()));
8259     if (Kind.isCStyleOrFunctionalCast())
8260       S.Diag(Kind.getLocation(), diag::err_builtin_func_cast_more_than_one_arg)
8261         << R;
8262     else
8263       S.Diag(Kind.getLocation(), diag::err_excess_initializers)
8264         << /*scalar=*/2 << R;
8265     break;
8266   }
8267
8268   case FK_ParenthesizedListInitForScalar:
8269     S.Diag(Kind.getLocation(), diag::err_list_init_in_parens)
8270       << 0 << Entity.getType() << Args[0]->getSourceRange();
8271     break;
8272
8273   case FK_ReferenceBindingToInitList:
8274     S.Diag(Kind.getLocation(), diag::err_reference_bind_init_list)
8275       << DestType.getNonReferenceType() << Args[0]->getSourceRange();
8276     break;
8277
8278   case FK_InitListBadDestinationType:
8279     S.Diag(Kind.getLocation(), diag::err_init_list_bad_dest_type)
8280       << (DestType->isRecordType()) << DestType << Args[0]->getSourceRange();
8281     break;
8282
8283   case FK_ListConstructorOverloadFailed:
8284   case FK_ConstructorOverloadFailed: {
8285     SourceRange ArgsRange;
8286     if (Args.size())
8287       ArgsRange = SourceRange(Args.front()->getLocStart(),
8288                               Args.back()->getLocEnd());
8289
8290     if (Failure == FK_ListConstructorOverloadFailed) {
8291       assert(Args.size() == 1 &&
8292              "List construction from other than 1 argument.");
8293       InitListExpr *InitList = cast<InitListExpr>(Args[0]);
8294       Args = MultiExprArg(InitList->getInits(), InitList->getNumInits());
8295     }
8296
8297     // FIXME: Using "DestType" for the entity we're printing is probably
8298     // bad.
8299     switch (FailedOverloadResult) {
8300       case OR_Ambiguous:
8301         S.Diag(Kind.getLocation(), diag::err_ovl_ambiguous_init)
8302           << DestType << ArgsRange;
8303         FailedCandidateSet.NoteCandidates(S, OCD_ViableCandidates, Args);
8304         break;
8305
8306       case OR_No_Viable_Function:
8307         if (Kind.getKind() == InitializationKind::IK_Default &&
8308             (Entity.getKind() == InitializedEntity::EK_Base ||
8309              Entity.getKind() == InitializedEntity::EK_Member) &&
8310             isa<CXXConstructorDecl>(S.CurContext)) {
8311           // This is implicit default initialization of a member or
8312           // base within a constructor. If no viable function was
8313           // found, notify the user that they need to explicitly
8314           // initialize this base/member.
8315           CXXConstructorDecl *Constructor
8316             = cast<CXXConstructorDecl>(S.CurContext);
8317           const CXXRecordDecl *InheritedFrom = nullptr;
8318           if (auto Inherited = Constructor->getInheritedConstructor())
8319             InheritedFrom = Inherited.getShadowDecl()->getNominatedBaseClass();
8320           if (Entity.getKind() == InitializedEntity::EK_Base) {
8321             S.Diag(Kind.getLocation(), diag::err_missing_default_ctor)
8322               << (InheritedFrom ? 2 : Constructor->isImplicit() ? 1 : 0)
8323               << S.Context.getTypeDeclType(Constructor->getParent())
8324               << /*base=*/0
8325               << Entity.getType()
8326               << InheritedFrom;
8327
8328             RecordDecl *BaseDecl
8329               = Entity.getBaseSpecifier()->getType()->getAs<RecordType>()
8330                                                                   ->getDecl();
8331             S.Diag(BaseDecl->getLocation(), diag::note_previous_decl)
8332               << S.Context.getTagDeclType(BaseDecl);
8333           } else {
8334             S.Diag(Kind.getLocation(), diag::err_missing_default_ctor)
8335               << (InheritedFrom ? 2 : Constructor->isImplicit() ? 1 : 0)
8336               << S.Context.getTypeDeclType(Constructor->getParent())
8337               << /*member=*/1
8338               << Entity.getName()
8339               << InheritedFrom;
8340             S.Diag(Entity.getDecl()->getLocation(),
8341                    diag::note_member_declared_at);
8342
8343             if (const RecordType *Record
8344                                  = Entity.getType()->getAs<RecordType>())
8345               S.Diag(Record->getDecl()->getLocation(),
8346                      diag::note_previous_decl)
8347                 << S.Context.getTagDeclType(Record->getDecl());
8348           }
8349           break;
8350         }
8351
8352         S.Diag(Kind.getLocation(), diag::err_ovl_no_viable_function_in_init)
8353           << DestType << ArgsRange;
8354         FailedCandidateSet.NoteCandidates(S, OCD_AllCandidates, Args);
8355         break;
8356
8357       case OR_Deleted: {
8358         OverloadCandidateSet::iterator Best;
8359         OverloadingResult Ovl
8360           = FailedCandidateSet.BestViableFunction(S, Kind.getLocation(), Best);
8361         if (Ovl != OR_Deleted) {
8362           S.Diag(Kind.getLocation(), diag::err_ovl_deleted_init)
8363             << true << DestType << ArgsRange;
8364           llvm_unreachable("Inconsistent overload resolution?");
8365           break;
8366         }
8367
8368         // If this is a defaulted or implicitly-declared function, then
8369         // it was implicitly deleted. Make it clear that the deletion was
8370         // implicit.
8371         if (S.isImplicitlyDeleted(Best->Function))
8372           S.Diag(Kind.getLocation(), diag::err_ovl_deleted_special_init)
8373             << S.getSpecialMember(cast<CXXMethodDecl>(Best->Function))
8374             << DestType << ArgsRange;
8375         else
8376           S.Diag(Kind.getLocation(), diag::err_ovl_deleted_init)
8377             << true << DestType << ArgsRange;
8378
8379         S.NoteDeletedFunction(Best->Function);
8380         break;
8381       }
8382
8383       case OR_Success:
8384         llvm_unreachable("Conversion did not fail!");
8385     }
8386   }
8387   break;
8388
8389   case FK_DefaultInitOfConst:
8390     if (Entity.getKind() == InitializedEntity::EK_Member &&
8391         isa<CXXConstructorDecl>(S.CurContext)) {
8392       // This is implicit default-initialization of a const member in
8393       // a constructor. Complain that it needs to be explicitly
8394       // initialized.
8395       CXXConstructorDecl *Constructor = cast<CXXConstructorDecl>(S.CurContext);
8396       S.Diag(Kind.getLocation(), diag::err_uninitialized_member_in_ctor)
8397         << (Constructor->getInheritedConstructor() ? 2 :
8398             Constructor->isImplicit() ? 1 : 0)
8399         << S.Context.getTypeDeclType(Constructor->getParent())
8400         << /*const=*/1
8401         << Entity.getName();
8402       S.Diag(Entity.getDecl()->getLocation(), diag::note_previous_decl)
8403         << Entity.getName();
8404     } else {
8405       S.Diag(Kind.getLocation(), diag::err_default_init_const)
8406           << DestType << (bool)DestType->getAs<RecordType>();
8407     }
8408     break;
8409
8410   case FK_Incomplete:
8411     S.RequireCompleteType(Kind.getLocation(), FailedIncompleteType,
8412                           diag::err_init_incomplete_type);
8413     break;
8414
8415   case FK_ListInitializationFailed: {
8416     // Run the init list checker again to emit diagnostics.
8417     InitListExpr *InitList = cast<InitListExpr>(Args[0]);
8418     diagnoseListInit(S, Entity, InitList);
8419     break;
8420   }
8421
8422   case FK_PlaceholderType: {
8423     // FIXME: Already diagnosed!
8424     break;
8425   }
8426
8427   case FK_ExplicitConstructor: {
8428     S.Diag(Kind.getLocation(), diag::err_selected_explicit_constructor)
8429       << Args[0]->getSourceRange();
8430     OverloadCandidateSet::iterator Best;
8431     OverloadingResult Ovl
8432       = FailedCandidateSet.BestViableFunction(S, Kind.getLocation(), Best);
8433     (void)Ovl;
8434     assert(Ovl == OR_Success && "Inconsistent overload resolution");
8435     CXXConstructorDecl *CtorDecl = cast<CXXConstructorDecl>(Best->Function);
8436     S.Diag(CtorDecl->getLocation(),
8437            diag::note_explicit_ctor_deduction_guide_here) << false;
8438     break;
8439   }
8440   }
8441
8442   PrintInitLocationNote(S, Entity);
8443   return true;
8444 }
8445
8446 void InitializationSequence::dump(raw_ostream &OS) const {
8447   switch (SequenceKind) {
8448   case FailedSequence: {
8449     OS << "Failed sequence: ";
8450     switch (Failure) {
8451     case FK_TooManyInitsForReference:
8452       OS << "too many initializers for reference";
8453       break;
8454
8455     case FK_ParenthesizedListInitForReference:
8456       OS << "parenthesized list init for reference";
8457       break;
8458
8459     case FK_ArrayNeedsInitList:
8460       OS << "array requires initializer list";
8461       break;
8462
8463     case FK_AddressOfUnaddressableFunction:
8464       OS << "address of unaddressable function was taken";
8465       break;
8466
8467     case FK_ArrayNeedsInitListOrStringLiteral:
8468       OS << "array requires initializer list or string literal";
8469       break;
8470
8471     case FK_ArrayNeedsInitListOrWideStringLiteral:
8472       OS << "array requires initializer list or wide string literal";
8473       break;
8474
8475     case FK_NarrowStringIntoWideCharArray:
8476       OS << "narrow string into wide char array";
8477       break;
8478
8479     case FK_WideStringIntoCharArray:
8480       OS << "wide string into char array";
8481       break;
8482
8483     case FK_IncompatWideStringIntoWideChar:
8484       OS << "incompatible wide string into wide char array";
8485       break;
8486
8487     case FK_PlainStringIntoUTF8Char:
8488       OS << "plain string literal into char8_t array";
8489       break;
8490
8491     case FK_UTF8StringIntoPlainChar:
8492       OS << "u8 string literal into char array";
8493       break;
8494
8495     case FK_ArrayTypeMismatch:
8496       OS << "array type mismatch";
8497       break;
8498
8499     case FK_NonConstantArrayInit:
8500       OS << "non-constant array initializer";
8501       break;
8502
8503     case FK_AddressOfOverloadFailed:
8504       OS << "address of overloaded function failed";
8505       break;
8506
8507     case FK_ReferenceInitOverloadFailed:
8508       OS << "overload resolution for reference initialization failed";
8509       break;
8510
8511     case FK_NonConstLValueReferenceBindingToTemporary:
8512       OS << "non-const lvalue reference bound to temporary";
8513       break;
8514
8515     case FK_NonConstLValueReferenceBindingToBitfield:
8516       OS << "non-const lvalue reference bound to bit-field";
8517       break;
8518
8519     case FK_NonConstLValueReferenceBindingToVectorElement:
8520       OS << "non-const lvalue reference bound to vector element";
8521       break;
8522
8523     case FK_NonConstLValueReferenceBindingToUnrelated:
8524       OS << "non-const lvalue reference bound to unrelated type";
8525       break;
8526
8527     case FK_RValueReferenceBindingToLValue:
8528       OS << "rvalue reference bound to an lvalue";
8529       break;
8530
8531     case FK_ReferenceInitDropsQualifiers:
8532       OS << "reference initialization drops qualifiers";
8533       break;
8534
8535     case FK_ReferenceInitFailed:
8536       OS << "reference initialization failed";
8537       break;
8538
8539     case FK_ConversionFailed:
8540       OS << "conversion failed";
8541       break;
8542
8543     case FK_ConversionFromPropertyFailed:
8544       OS << "conversion from property failed";
8545       break;
8546
8547     case FK_TooManyInitsForScalar:
8548       OS << "too many initializers for scalar";
8549       break;
8550
8551     case FK_ParenthesizedListInitForScalar:
8552       OS << "parenthesized list init for reference";
8553       break;
8554
8555     case FK_ReferenceBindingToInitList:
8556       OS << "referencing binding to initializer list";
8557       break;
8558
8559     case FK_InitListBadDestinationType:
8560       OS << "initializer list for non-aggregate, non-scalar type";
8561       break;
8562
8563     case FK_UserConversionOverloadFailed:
8564       OS << "overloading failed for user-defined conversion";
8565       break;
8566
8567     case FK_ConstructorOverloadFailed:
8568       OS << "constructor overloading failed";
8569       break;
8570
8571     case FK_DefaultInitOfConst:
8572       OS << "default initialization of a const variable";
8573       break;
8574
8575     case FK_Incomplete:
8576       OS << "initialization of incomplete type";
8577       break;
8578
8579     case FK_ListInitializationFailed:
8580       OS << "list initialization checker failure";
8581       break;
8582
8583     case FK_VariableLengthArrayHasInitializer:
8584       OS << "variable length array has an initializer";
8585       break;
8586
8587     case FK_PlaceholderType:
8588       OS << "initializer expression isn't contextually valid";
8589       break;
8590
8591     case FK_ListConstructorOverloadFailed:
8592       OS << "list constructor overloading failed";
8593       break;
8594
8595     case FK_ExplicitConstructor:
8596       OS << "list copy initialization chose explicit constructor";
8597       break;
8598     }
8599     OS << '\n';
8600     return;
8601   }
8602
8603   case DependentSequence:
8604     OS << "Dependent sequence\n";
8605     return;
8606
8607   case NormalSequence:
8608     OS << "Normal sequence: ";
8609     break;
8610   }
8611
8612   for (step_iterator S = step_begin(), SEnd = step_end(); S != SEnd; ++S) {
8613     if (S != step_begin()) {
8614       OS << " -> ";
8615     }
8616
8617     switch (S->Kind) {
8618     case SK_ResolveAddressOfOverloadedFunction:
8619       OS << "resolve address of overloaded function";
8620       break;
8621
8622     case SK_CastDerivedToBaseRValue:
8623       OS << "derived-to-base (rvalue)";
8624       break;
8625
8626     case SK_CastDerivedToBaseXValue:
8627       OS << "derived-to-base (xvalue)";
8628       break;
8629
8630     case SK_CastDerivedToBaseLValue:
8631       OS << "derived-to-base (lvalue)";
8632       break;
8633
8634     case SK_BindReference:
8635       OS << "bind reference to lvalue";
8636       break;
8637
8638     case SK_BindReferenceToTemporary:
8639       OS << "bind reference to a temporary";
8640       break;
8641
8642     case SK_FinalCopy:
8643       OS << "final copy in class direct-initialization";
8644       break;
8645
8646     case SK_ExtraneousCopyToTemporary:
8647       OS << "extraneous C++03 copy to temporary";
8648       break;
8649
8650     case SK_UserConversion:
8651       OS << "user-defined conversion via " << *S->Function.Function;
8652       break;
8653
8654     case SK_QualificationConversionRValue:
8655       OS << "qualification conversion (rvalue)";
8656       break;
8657
8658     case SK_QualificationConversionXValue:
8659       OS << "qualification conversion (xvalue)";
8660       break;
8661
8662     case SK_QualificationConversionLValue:
8663       OS << "qualification conversion (lvalue)";
8664       break;
8665
8666     case SK_AtomicConversion:
8667       OS << "non-atomic-to-atomic conversion";
8668       break;
8669
8670     case SK_LValueToRValue:
8671       OS << "load (lvalue to rvalue)";
8672       break;
8673
8674     case SK_ConversionSequence:
8675       OS << "implicit conversion sequence (";
8676       S->ICS->dump(); // FIXME: use OS
8677       OS << ")";
8678       break;
8679
8680     case SK_ConversionSequenceNoNarrowing:
8681       OS << "implicit conversion sequence with narrowing prohibited (";
8682       S->ICS->dump(); // FIXME: use OS
8683       OS << ")";
8684       break;
8685
8686     case SK_ListInitialization:
8687       OS << "list aggregate initialization";
8688       break;
8689
8690     case SK_UnwrapInitList:
8691       OS << "unwrap reference initializer list";
8692       break;
8693
8694     case SK_RewrapInitList:
8695       OS << "rewrap reference initializer list";
8696       break;
8697
8698     case SK_ConstructorInitialization:
8699       OS << "constructor initialization";
8700       break;
8701
8702     case SK_ConstructorInitializationFromList:
8703       OS << "list initialization via constructor";
8704       break;
8705
8706     case SK_ZeroInitialization:
8707       OS << "zero initialization";
8708       break;
8709
8710     case SK_CAssignment:
8711       OS << "C assignment";
8712       break;
8713
8714     case SK_StringInit:
8715       OS << "string initialization";
8716       break;
8717
8718     case SK_ObjCObjectConversion:
8719       OS << "Objective-C object conversion";
8720       break;
8721
8722     case SK_ArrayLoopIndex:
8723       OS << "indexing for array initialization loop";
8724       break;
8725
8726     case SK_ArrayLoopInit:
8727       OS << "array initialization loop";
8728       break;
8729
8730     case SK_ArrayInit:
8731       OS << "array initialization";
8732       break;
8733
8734     case SK_GNUArrayInit:
8735       OS << "array initialization (GNU extension)";
8736       break;
8737
8738     case SK_ParenthesizedArrayInit:
8739       OS << "parenthesized array initialization";
8740       break;
8741
8742     case SK_PassByIndirectCopyRestore:
8743       OS << "pass by indirect copy and restore";
8744       break;
8745
8746     case SK_PassByIndirectRestore:
8747       OS << "pass by indirect restore";
8748       break;
8749
8750     case SK_ProduceObjCObject:
8751       OS << "Objective-C object retension";
8752       break;
8753
8754     case SK_StdInitializerList:
8755       OS << "std::initializer_list from initializer list";
8756       break;
8757
8758     case SK_StdInitializerListConstructorCall:
8759       OS << "list initialization from std::initializer_list";
8760       break;
8761
8762     case SK_OCLSamplerInit:
8763       OS << "OpenCL sampler_t from integer constant";
8764       break;
8765
8766     case SK_OCLZeroEvent:
8767       OS << "OpenCL event_t from zero";
8768       break;
8769
8770     case SK_OCLZeroQueue:
8771       OS << "OpenCL queue_t from zero";
8772       break;
8773     }
8774
8775     OS << " [" << S->Type.getAsString() << ']';
8776   }
8777
8778   OS << '\n';
8779 }
8780
8781 void InitializationSequence::dump() const {
8782   dump(llvm::errs());
8783 }
8784
8785 static bool NarrowingErrs(const LangOptions &L) {
8786   return L.CPlusPlus11 &&
8787          (!L.MicrosoftExt || L.isCompatibleWithMSVC(LangOptions::MSVC2015));
8788 }
8789
8790 static void DiagnoseNarrowingInInitList(Sema &S,
8791                                         const ImplicitConversionSequence &ICS,
8792                                         QualType PreNarrowingType,
8793                                         QualType EntityType,
8794                                         const Expr *PostInit) {
8795   const StandardConversionSequence *SCS = nullptr;
8796   switch (ICS.getKind()) {
8797   case ImplicitConversionSequence::StandardConversion:
8798     SCS = &ICS.Standard;
8799     break;
8800   case ImplicitConversionSequence::UserDefinedConversion:
8801     SCS = &ICS.UserDefined.After;
8802     break;
8803   case ImplicitConversionSequence::AmbiguousConversion:
8804   case ImplicitConversionSequence::EllipsisConversion:
8805   case ImplicitConversionSequence::BadConversion:
8806     return;
8807   }
8808
8809   // C++11 [dcl.init.list]p7: Check whether this is a narrowing conversion.
8810   APValue ConstantValue;
8811   QualType ConstantType;
8812   switch (SCS->getNarrowingKind(S.Context, PostInit, ConstantValue,
8813                                 ConstantType)) {
8814   case NK_Not_Narrowing:
8815   case NK_Dependent_Narrowing:
8816     // No narrowing occurred.
8817     return;
8818
8819   case NK_Type_Narrowing:
8820     // This was a floating-to-integer conversion, which is always considered a
8821     // narrowing conversion even if the value is a constant and can be
8822     // represented exactly as an integer.
8823     S.Diag(PostInit->getLocStart(), NarrowingErrs(S.getLangOpts())
8824                                         ? diag::ext_init_list_type_narrowing
8825                                         : diag::warn_init_list_type_narrowing)
8826         << PostInit->getSourceRange()
8827         << PreNarrowingType.getLocalUnqualifiedType()
8828         << EntityType.getLocalUnqualifiedType();
8829     break;
8830
8831   case NK_Constant_Narrowing:
8832     // A constant value was narrowed.
8833     S.Diag(PostInit->getLocStart(),
8834            NarrowingErrs(S.getLangOpts())
8835                ? diag::ext_init_list_constant_narrowing
8836                : diag::warn_init_list_constant_narrowing)
8837         << PostInit->getSourceRange()
8838         << ConstantValue.getAsString(S.getASTContext(), ConstantType)
8839         << EntityType.getLocalUnqualifiedType();
8840     break;
8841
8842   case NK_Variable_Narrowing:
8843     // A variable's value may have been narrowed.
8844     S.Diag(PostInit->getLocStart(),
8845            NarrowingErrs(S.getLangOpts())
8846                ? diag::ext_init_list_variable_narrowing
8847                : diag::warn_init_list_variable_narrowing)
8848         << PostInit->getSourceRange()
8849         << PreNarrowingType.getLocalUnqualifiedType()
8850         << EntityType.getLocalUnqualifiedType();
8851     break;
8852   }
8853
8854   SmallString<128> StaticCast;
8855   llvm::raw_svector_ostream OS(StaticCast);
8856   OS << "static_cast<";
8857   if (const TypedefType *TT = EntityType->getAs<TypedefType>()) {
8858     // It's important to use the typedef's name if there is one so that the
8859     // fixit doesn't break code using types like int64_t.
8860     //
8861     // FIXME: This will break if the typedef requires qualification.  But
8862     // getQualifiedNameAsString() includes non-machine-parsable components.
8863     OS << *TT->getDecl();
8864   } else if (const BuiltinType *BT = EntityType->getAs<BuiltinType>())
8865     OS << BT->getName(S.getLangOpts());
8866   else {
8867     // Oops, we didn't find the actual type of the variable.  Don't emit a fixit
8868     // with a broken cast.
8869     return;
8870   }
8871   OS << ">(";
8872   S.Diag(PostInit->getLocStart(), diag::note_init_list_narrowing_silence)
8873       << PostInit->getSourceRange()
8874       << FixItHint::CreateInsertion(PostInit->getLocStart(), OS.str())
8875       << FixItHint::CreateInsertion(
8876              S.getLocForEndOfToken(PostInit->getLocEnd()), ")");
8877 }
8878
8879 //===----------------------------------------------------------------------===//
8880 // Initialization helper functions
8881 //===----------------------------------------------------------------------===//
8882 bool
8883 Sema::CanPerformCopyInitialization(const InitializedEntity &Entity,
8884                                    ExprResult Init) {
8885   if (Init.isInvalid())
8886     return false;
8887
8888   Expr *InitE = Init.get();
8889   assert(InitE && "No initialization expression");
8890
8891   InitializationKind Kind
8892     = InitializationKind::CreateCopy(InitE->getLocStart(), SourceLocation());
8893   InitializationSequence Seq(*this, Entity, Kind, InitE);
8894   return !Seq.Failed();
8895 }
8896
8897 ExprResult
8898 Sema::PerformCopyInitialization(const InitializedEntity &Entity,
8899                                 SourceLocation EqualLoc,
8900                                 ExprResult Init,
8901                                 bool TopLevelOfInitList,
8902                                 bool AllowExplicit) {
8903   if (Init.isInvalid())
8904     return ExprError();
8905
8906   Expr *InitE = Init.get();
8907   assert(InitE && "No initialization expression?");
8908
8909   if (EqualLoc.isInvalid())
8910     EqualLoc = InitE->getLocStart();
8911
8912   InitializationKind Kind = InitializationKind::CreateCopy(InitE->getLocStart(),
8913                                                            EqualLoc,
8914                                                            AllowExplicit);
8915   InitializationSequence Seq(*this, Entity, Kind, InitE, TopLevelOfInitList);
8916
8917   // Prevent infinite recursion when performing parameter copy-initialization.
8918   const bool ShouldTrackCopy =
8919       Entity.isParameterKind() && Seq.isConstructorInitialization();
8920   if (ShouldTrackCopy) {
8921     if (llvm::find(CurrentParameterCopyTypes, Entity.getType()) !=
8922         CurrentParameterCopyTypes.end()) {
8923       Seq.SetOverloadFailure(
8924           InitializationSequence::FK_ConstructorOverloadFailed,
8925           OR_No_Viable_Function);
8926
8927       // Try to give a meaningful diagnostic note for the problematic
8928       // constructor.
8929       const auto LastStep = Seq.step_end() - 1;
8930       assert(LastStep->Kind ==
8931              InitializationSequence::SK_ConstructorInitialization);
8932       const FunctionDecl *Function = LastStep->Function.Function;
8933       auto Candidate =
8934           llvm::find_if(Seq.getFailedCandidateSet(),
8935                         [Function](const OverloadCandidate &Candidate) -> bool {
8936                           return Candidate.Viable &&
8937                                  Candidate.Function == Function &&
8938                                  Candidate.Conversions.size() > 0;
8939                         });
8940       if (Candidate != Seq.getFailedCandidateSet().end() &&
8941           Function->getNumParams() > 0) {
8942         Candidate->Viable = false;
8943         Candidate->FailureKind = ovl_fail_bad_conversion;
8944         Candidate->Conversions[0].setBad(BadConversionSequence::no_conversion,
8945                                          InitE,
8946                                          Function->getParamDecl(0)->getType());
8947       }
8948     }
8949     CurrentParameterCopyTypes.push_back(Entity.getType());
8950   }
8951
8952   ExprResult Result = Seq.Perform(*this, Entity, Kind, InitE);
8953
8954   if (ShouldTrackCopy)
8955     CurrentParameterCopyTypes.pop_back();
8956
8957   return Result;
8958 }
8959
8960 /// Determine whether RD is, or is derived from, a specialization of CTD.
8961 static bool isOrIsDerivedFromSpecializationOf(CXXRecordDecl *RD,
8962                                               ClassTemplateDecl *CTD) {
8963   auto NotSpecialization = [&] (const CXXRecordDecl *Candidate) {
8964     auto *CTSD = dyn_cast<ClassTemplateSpecializationDecl>(Candidate);
8965     return !CTSD || !declaresSameEntity(CTSD->getSpecializedTemplate(), CTD);
8966   };
8967   return !(NotSpecialization(RD) && RD->forallBases(NotSpecialization));
8968 }
8969
8970 QualType Sema::DeduceTemplateSpecializationFromInitializer(
8971     TypeSourceInfo *TSInfo, const InitializedEntity &Entity,
8972     const InitializationKind &Kind, MultiExprArg Inits) {
8973   auto *DeducedTST = dyn_cast<DeducedTemplateSpecializationType>(
8974       TSInfo->getType()->getContainedDeducedType());
8975   assert(DeducedTST && "not a deduced template specialization type");
8976
8977   // We can only perform deduction for class templates.
8978   auto TemplateName = DeducedTST->getTemplateName();
8979   auto *Template =
8980       dyn_cast_or_null<ClassTemplateDecl>(TemplateName.getAsTemplateDecl());
8981   if (!Template) {
8982     Diag(Kind.getLocation(),
8983          diag::err_deduced_non_class_template_specialization_type)
8984       << (int)getTemplateNameKindForDiagnostics(TemplateName) << TemplateName;
8985     if (auto *TD = TemplateName.getAsTemplateDecl())
8986       Diag(TD->getLocation(), diag::note_template_decl_here);
8987     return QualType();
8988   }
8989
8990   // Can't deduce from dependent arguments.
8991   if (Expr::hasAnyTypeDependentArguments(Inits))
8992     return Context.DependentTy;
8993
8994   // FIXME: Perform "exact type" matching first, per CWG discussion?
8995   //        Or implement this via an implied 'T(T) -> T' deduction guide?
8996
8997   // FIXME: Do we need/want a std::initializer_list<T> special case?
8998
8999   // Look up deduction guides, including those synthesized from constructors.
9000   //
9001   // C++1z [over.match.class.deduct]p1:
9002   //   A set of functions and function templates is formed comprising:
9003   //   - For each constructor of the class template designated by the
9004   //     template-name, a function template [...]
9005   //  - For each deduction-guide, a function or function template [...]
9006   DeclarationNameInfo NameInfo(
9007       Context.DeclarationNames.getCXXDeductionGuideName(Template),
9008       TSInfo->getTypeLoc().getEndLoc());
9009   LookupResult Guides(*this, NameInfo, LookupOrdinaryName);
9010   LookupQualifiedName(Guides, Template->getDeclContext());
9011
9012   // FIXME: Do not diagnose inaccessible deduction guides. The standard isn't
9013   // clear on this, but they're not found by name so access does not apply.
9014   Guides.suppressDiagnostics();
9015
9016   // Figure out if this is list-initialization.
9017   InitListExpr *ListInit =
9018       (Inits.size() == 1 && Kind.getKind() != InitializationKind::IK_Direct)
9019           ? dyn_cast<InitListExpr>(Inits[0])
9020           : nullptr;
9021
9022   // C++1z [over.match.class.deduct]p1:
9023   //   Initialization and overload resolution are performed as described in
9024   //   [dcl.init] and [over.match.ctor], [over.match.copy], or [over.match.list]
9025   //   (as appropriate for the type of initialization performed) for an object
9026   //   of a hypothetical class type, where the selected functions and function
9027   //   templates are considered to be the constructors of that class type
9028   //
9029   // Since we know we're initializing a class type of a type unrelated to that
9030   // of the initializer, this reduces to something fairly reasonable.
9031   OverloadCandidateSet Candidates(Kind.getLocation(),
9032                                   OverloadCandidateSet::CSK_Normal);
9033   OverloadCandidateSet::iterator Best;
9034   auto tryToResolveOverload =
9035       [&](bool OnlyListConstructors) -> OverloadingResult {
9036     Candidates.clear(OverloadCandidateSet::CSK_Normal);
9037     for (auto I = Guides.begin(), E = Guides.end(); I != E; ++I) {
9038       NamedDecl *D = (*I)->getUnderlyingDecl();
9039       if (D->isInvalidDecl())
9040         continue;
9041
9042       auto *TD = dyn_cast<FunctionTemplateDecl>(D);
9043       auto *GD = dyn_cast_or_null<CXXDeductionGuideDecl>(
9044           TD ? TD->getTemplatedDecl() : dyn_cast<FunctionDecl>(D));
9045       if (!GD)
9046         continue;
9047
9048       // C++ [over.match.ctor]p1: (non-list copy-initialization from non-class)
9049       //   For copy-initialization, the candidate functions are all the
9050       //   converting constructors (12.3.1) of that class.
9051       // C++ [over.match.copy]p1: (non-list copy-initialization from class)
9052       //   The converting constructors of T are candidate functions.
9053       if (Kind.isCopyInit() && !ListInit) {
9054         // Only consider converting constructors.
9055         if (GD->isExplicit())
9056           continue;
9057
9058         // When looking for a converting constructor, deduction guides that
9059         // could never be called with one argument are not interesting to
9060         // check or note.
9061         if (GD->getMinRequiredArguments() > 1 ||
9062             (GD->getNumParams() == 0 && !GD->isVariadic()))
9063           continue;
9064       }
9065
9066       // C++ [over.match.list]p1.1: (first phase list initialization)
9067       //   Initially, the candidate functions are the initializer-list
9068       //   constructors of the class T
9069       if (OnlyListConstructors && !isInitListConstructor(GD))
9070         continue;
9071
9072       // C++ [over.match.list]p1.2: (second phase list initialization)
9073       //   the candidate functions are all the constructors of the class T
9074       // C++ [over.match.ctor]p1: (all other cases)
9075       //   the candidate functions are all the constructors of the class of
9076       //   the object being initialized
9077
9078       // C++ [over.best.ics]p4:
9079       //   When [...] the constructor [...] is a candidate by
9080       //    - [over.match.copy] (in all cases)
9081       // FIXME: The "second phase of [over.match.list] case can also
9082       // theoretically happen here, but it's not clear whether we can
9083       // ever have a parameter of the right type.
9084       bool SuppressUserConversions = Kind.isCopyInit();
9085
9086       if (TD)
9087         AddTemplateOverloadCandidate(TD, I.getPair(), /*ExplicitArgs*/ nullptr,
9088                                      Inits, Candidates,
9089                                      SuppressUserConversions);
9090       else
9091         AddOverloadCandidate(GD, I.getPair(), Inits, Candidates,
9092                              SuppressUserConversions);
9093     }
9094     return Candidates.BestViableFunction(*this, Kind.getLocation(), Best);
9095   };
9096
9097   OverloadingResult Result = OR_No_Viable_Function;
9098
9099   // C++11 [over.match.list]p1, per DR1467: for list-initialization, first
9100   // try initializer-list constructors.
9101   if (ListInit) {
9102     bool TryListConstructors = true;
9103
9104     // Try list constructors unless the list is empty and the class has one or
9105     // more default constructors, in which case those constructors win.
9106     if (!ListInit->getNumInits()) {
9107       for (NamedDecl *D : Guides) {
9108         auto *FD = dyn_cast<FunctionDecl>(D->getUnderlyingDecl());
9109         if (FD && FD->getMinRequiredArguments() == 0) {
9110           TryListConstructors = false;
9111           break;
9112         }
9113       }
9114     } else if (ListInit->getNumInits() == 1) {
9115       // C++ [over.match.class.deduct]:
9116       //   As an exception, the first phase in [over.match.list] (considering
9117       //   initializer-list constructors) is omitted if the initializer list
9118       //   consists of a single expression of type cv U, where U is a
9119       //   specialization of C or a class derived from a specialization of C.
9120       Expr *E = ListInit->getInit(0);
9121       auto *RD = E->getType()->getAsCXXRecordDecl();
9122       if (!isa<InitListExpr>(E) && RD &&
9123           isCompleteType(Kind.getLocation(), E->getType()) &&
9124           isOrIsDerivedFromSpecializationOf(RD, Template))
9125         TryListConstructors = false;
9126     }
9127
9128     if (TryListConstructors)
9129       Result = tryToResolveOverload(/*OnlyListConstructor*/true);
9130     // Then unwrap the initializer list and try again considering all
9131     // constructors.
9132     Inits = MultiExprArg(ListInit->getInits(), ListInit->getNumInits());
9133   }
9134
9135   // If list-initialization fails, or if we're doing any other kind of
9136   // initialization, we (eventually) consider constructors.
9137   if (Result == OR_No_Viable_Function)
9138     Result = tryToResolveOverload(/*OnlyListConstructor*/false);
9139
9140   switch (Result) {
9141   case OR_Ambiguous:
9142     Diag(Kind.getLocation(), diag::err_deduced_class_template_ctor_ambiguous)
9143       << TemplateName;
9144     // FIXME: For list-initialization candidates, it'd usually be better to
9145     // list why they were not viable when given the initializer list itself as
9146     // an argument.
9147     Candidates.NoteCandidates(*this, OCD_ViableCandidates, Inits);
9148     return QualType();
9149
9150   case OR_No_Viable_Function: {
9151     CXXRecordDecl *Primary =
9152         cast<ClassTemplateDecl>(Template)->getTemplatedDecl();
9153     bool Complete =
9154         isCompleteType(Kind.getLocation(), Context.getTypeDeclType(Primary));
9155     Diag(Kind.getLocation(),
9156          Complete ? diag::err_deduced_class_template_ctor_no_viable
9157                   : diag::err_deduced_class_template_incomplete)
9158       << TemplateName << !Guides.empty();
9159     Candidates.NoteCandidates(*this, OCD_AllCandidates, Inits);
9160     return QualType();
9161   }
9162
9163   case OR_Deleted: {
9164     Diag(Kind.getLocation(), diag::err_deduced_class_template_deleted)
9165       << TemplateName;
9166     NoteDeletedFunction(Best->Function);
9167     return QualType();
9168   }
9169
9170   case OR_Success:
9171     // C++ [over.match.list]p1:
9172     //   In copy-list-initialization, if an explicit constructor is chosen, the
9173     //   initialization is ill-formed.
9174     if (Kind.isCopyInit() && ListInit &&
9175         cast<CXXDeductionGuideDecl>(Best->Function)->isExplicit()) {
9176       bool IsDeductionGuide = !Best->Function->isImplicit();
9177       Diag(Kind.getLocation(), diag::err_deduced_class_template_explicit)
9178           << TemplateName << IsDeductionGuide;
9179       Diag(Best->Function->getLocation(),
9180            diag::note_explicit_ctor_deduction_guide_here)
9181           << IsDeductionGuide;
9182       return QualType();
9183     }
9184
9185     // Make sure we didn't select an unusable deduction guide, and mark it
9186     // as referenced.
9187     DiagnoseUseOfDecl(Best->Function, Kind.getLocation());
9188     MarkFunctionReferenced(Kind.getLocation(), Best->Function);
9189     break;
9190   }
9191
9192   // C++ [dcl.type.class.deduct]p1:
9193   //  The placeholder is replaced by the return type of the function selected
9194   //  by overload resolution for class template deduction.
9195   return SubstAutoType(TSInfo->getType(), Best->Function->getReturnType());
9196 }