[AST] Use std::nullopt instead of None (NFC)

This patch mechanically replaces None with std::nullopt where the
compiler would warn if None were deprecated.  The intent is to reduce
the amount of manual work required in migrating from Optional to
std::optional.

This is part of an effort to migrate from llvm::Optional to
std::optional:

https://discourse.llvm.org/t/deprecating-llvm-optional-x-hasvalue-getvalue-getvalueor/63716

clang/include/clang/AST/ASTContext.h

@@ -2293,7 +2293,7 @@ public:
 
   Optional<CharUnits> getTypeSizeInCharsIfKnown(QualType Ty) const {
     if (Ty->isIncompleteType() || Ty->isDependentType())
-      return None;
+      return std::nullopt;
     return getTypeSizeInChars(Ty);
   }
 

clang/include/clang/AST/ASTImporterSharedState.h

@@ -70,7 +70,7 @@ public:
     if (Pos != ImportErrors.end())
       return Pos->second;
     else
-      return None;
+      return std::nullopt;
   }
 
   void setImportDeclError(Decl *To, ASTImportError Error) {

clang/include/clang/AST/CommentSema.h

@@ -80,7 +80,7 @@ public:
   ArrayRef<T> copyArray(ArrayRef<T> Source) {
     if (!Source.empty())
       return Source.copy(Allocator);
-    return None;
+    return std::nullopt;
   }
 
   ParagraphComment *actOnParagraphComment(

clang/include/clang/AST/DeclFriend.h

@@ -108,11 +108,10 @@ public:
   friend class ASTNodeImporter;
   friend TrailingObjects;
 
-  static FriendDecl *Create(ASTContext &C, DeclContext *DC,
+  static FriendDecl *
-                            SourceLocation L, FriendUnion Friend_,
+  Create(ASTContext &C, DeclContext *DC, SourceLocation L, FriendUnion Friend_,
          SourceLocation FriendL,
-                            ArrayRef<TemplateParameterList*> FriendTypeTPLists
+         ArrayRef<TemplateParameterList *> FriendTypeTPLists = std::nullopt);
-                            = None);
   static FriendDecl *CreateDeserialized(ASTContext &C, unsigned ID,
                                         unsigned FriendTypeNumTPLists);
 

clang/include/clang/AST/DeclObjC.h

@@ -389,9 +389,8 @@ public:
   /// Sets the method's parameters and selector source locations.
   /// If the method is implicit (not coming from source) \p SelLocs is
   /// ignored.
-  void setMethodParams(ASTContext &C,
+  void setMethodParams(ASTContext &C, ArrayRef<ParmVarDecl *> Params,
-                       ArrayRef<ParmVarDecl*> Params,
+                       ArrayRef<SourceLocation> SelLocs = std::nullopt);
-                       ArrayRef<SourceLocation> SelLocs = llvm::None);
 
   // Iterator access to parameter types.
   struct GetTypeFn {

clang/include/clang/AST/DeclOpenMP.h

@@ -34,7 +34,7 @@ template <typename U> class OMPDeclarativeDirective : public U {
   /// Get the clauses storage.
   MutableArrayRef<OMPClause *> getClauses() {
     if (!Data)
-      return llvm::None;
+      return std::nullopt;
     return Data->getClauses();
   }
 
@@ -90,7 +90,7 @@ public:
 
   ArrayRef<OMPClause *> clauses() const {
     if (!Data)
-      return llvm::None;
+      return std::nullopt;
     return Data->getClauses();
   }
 };

clang/include/clang/AST/DeclTemplate.h

@@ -1245,14 +1245,11 @@ class TemplateTypeParmDecl final : public TypeDecl,
         NumExpanded(NumExpanded.value_or(0)) {}
 
 public:
-  static TemplateTypeParmDecl *Create(const ASTContext &C, DeclContext *DC,
+  static TemplateTypeParmDecl *
-                                      SourceLocation KeyLoc,
+  Create(const ASTContext &C, DeclContext *DC, SourceLocation KeyLoc,
-                                      SourceLocation NameLoc,
+         SourceLocation NameLoc, unsigned D, unsigned P, IdentifierInfo *Id,
-                                      unsigned D, unsigned P,
+         bool Typename, bool ParameterPack, bool HasTypeConstraint = false,
-                                      IdentifierInfo *Id, bool Typename,
+         Optional<unsigned> NumExpanded = std::nullopt);
-                                      bool ParameterPack,
-                                      bool HasTypeConstraint = false,
-                                      Optional<unsigned> NumExpanded = None);
   static TemplateTypeParmDecl *CreateDeserialized(const ASTContext &C,
                                                   unsigned ID);
   static TemplateTypeParmDecl *CreateDeserialized(const ASTContext &C,
@@ -3453,7 +3450,7 @@ inline Optional<unsigned> getExpandedPackSize(const NamedDecl *Param) {
       return TTP->getNumExpansionTemplateParameters();
   }
 
-  return None;
+  return std::nullopt;
 }
 
 /// Internal helper used by Subst* nodes to retrieve the parameter list

clang/include/clang/AST/ExprCXX.h

@@ -2273,13 +2273,13 @@ public:
   /// If the result is not-None, it will never wrap a nullptr.
   Optional<Expr *> getArraySize() {
     if (!isArray())
-      return None;
+      return std::nullopt;
 
     if (auto *Result =
             cast_or_null<Expr>(getTrailingObjects<Stmt *>()[arraySizeOffset()]))
       return Result;
 
-    return None;
+    return std::nullopt;
   }
 
   /// This might return None even if isArray() returns true,
@@ -2287,13 +2287,13 @@ public:
   /// If the result is not-None, it will never wrap a nullptr.
   Optional<const Expr *> getArraySize() const {
     if (!isArray())
-      return None;
+      return std::nullopt;
 
     if (auto *Result =
             cast_or_null<Expr>(getTrailingObjects<Stmt *>()[arraySizeOffset()]))
       return Result;
 
-    return None;
+    return std::nullopt;
   }
 
   unsigned getNumPlacementArgs() const {
@@ -4116,7 +4116,7 @@ public:
     if (NumExpansions)
       return NumExpansions - 1;
 
-    return None;
+    return std::nullopt;
   }
 
   SourceLocation getBeginLoc() const LLVM_READONLY {
@@ -4201,11 +4201,11 @@ class SizeOfPackExpr final
       : Expr(SizeOfPackExprClass, Empty), Length(NumPartialArgs) {}
 
 public:
-  static SizeOfPackExpr *Create(ASTContext &Context, SourceLocation OperatorLoc,
+  static SizeOfPackExpr *
-                                NamedDecl *Pack, SourceLocation PackLoc,
+  Create(ASTContext &Context, SourceLocation OperatorLoc, NamedDecl *Pack,
-                                SourceLocation RParenLoc,
+         SourceLocation PackLoc, SourceLocation RParenLoc,
-                                Optional<unsigned> Length = None,
+         Optional<unsigned> Length = std::nullopt,
-                                ArrayRef<TemplateArgument> PartialArgs = None);
+         ArrayRef<TemplateArgument> PartialArgs = std::nullopt);
   static SizeOfPackExpr *CreateDeserialized(ASTContext &Context,
                                             unsigned NumPartialArgs);
 
@@ -4316,7 +4316,7 @@ public:
 
   Optional<unsigned> getPackIndex() const {
     if (PackIndex == 0)
-      return None;
+      return std::nullopt;
     return PackIndex - 1;
   }
 
@@ -4681,7 +4681,7 @@ public:
   Optional<unsigned> getNumExpansions() const {
     if (NumExpansions)
       return NumExpansions - 1;
-    return None;
+    return std::nullopt;
   }
 
   SourceLocation getBeginLoc() const LLVM_READONLY {

clang/include/clang/AST/ExprObjC.h

@@ -362,7 +362,8 @@ public:
   ObjCDictionaryElement getKeyValueElement(unsigned Index) const {
     assert((Index < NumElements) && "Arg access out of range!");
     const KeyValuePair &KV = getTrailingObjects<KeyValuePair>()[Index];
-    ObjCDictionaryElement Result = { KV.Key, KV.Value, SourceLocation(), None };
+    ObjCDictionaryElement Result = {KV.Key, KV.Value, SourceLocation(),
+                                    std::nullopt};
     if (HasPackExpansions) {
       const ExpansionData &Expansion =
           getTrailingObjects<ExpansionData>()[Index];

clang/include/clang/AST/OpenMPClause.h

@@ -5838,14 +5838,14 @@ public:
     return const_component_lists_iterator(
         getUniqueDeclsRef(), getDeclNumListsRef(), getComponentListSizesRef(),
         getComponentsRef(), SupportsMapper,
-        SupportsMapper ? getUDMapperRefs() : llvm::None);
+        SupportsMapper ? getUDMapperRefs() : std::nullopt);
   }
   const_component_lists_iterator component_lists_end() const {
     return const_component_lists_iterator(
         ArrayRef<ValueDecl *>(), ArrayRef<unsigned>(), ArrayRef<unsigned>(),
         MappableExprComponentListRef(getComponentsRef().end(),
                                      getComponentsRef().end()),
-        SupportsMapper, llvm::None);
+        SupportsMapper, std::nullopt);
   }
   const_component_lists_range component_lists() const {
     return {component_lists_begin(), component_lists_end()};
@@ -5858,7 +5858,7 @@ public:
     return const_component_lists_iterator(
         VD, getUniqueDeclsRef(), getDeclNumListsRef(),
         getComponentListSizesRef(), getComponentsRef(), SupportsMapper,
-        SupportsMapper ? getUDMapperRefs() : llvm::None);
+        SupportsMapper ? getUDMapperRefs() : std::nullopt);
   }
   const_component_lists_iterator decl_component_lists_end() const {
     return component_lists_end();

clang/include/clang/AST/StmtOpenMP.h

@@ -277,7 +277,7 @@ class OMPExecutableDirective : public Stmt {
   /// Get the clauses storage.
   MutableArrayRef<OMPClause *> getClauses() {
     if (!Data)
-      return llvm::None;
+      return std::nullopt;
     return Data->getClauses();
   }
 
@@ -571,7 +571,7 @@ public:
 
   ArrayRef<OMPClause *> clauses() const {
     if (!Data)
-      return llvm::None;
+      return std::nullopt;
     return Data->getClauses();
   }
 

clang/include/clang/AST/TemplateBase.h

@@ -233,7 +233,9 @@ public:
 
   TemplateArgument(TemplateName, bool) = delete;
 
-  static TemplateArgument getEmptyPack() { return TemplateArgument(None); }
+  static TemplateArgument getEmptyPack() {
+    return TemplateArgument(std::nullopt);
+  }
 
   /// Create a new template argument pack by copying the given set of
   /// template arguments.

clang/include/clang/AST/TemplateName.h

@@ -397,7 +397,7 @@ public:
 
   Optional<unsigned> getPackIndex() const {
     if (Bits.Data == 0)
-      return None;
+      return std::nullopt;
     return Bits.Data - 1;
   }
 

clang/include/clang/AST/Type.h

@@ -5113,7 +5113,7 @@ public:
 
   Optional<unsigned> getPackIndex() const {
     if (SubstTemplateTypeParmTypeBits.PackIndex == 0)
-      return None;
+      return std::nullopt;
     return SubstTemplateTypeParmTypeBits.PackIndex - 1;
   }
 
@@ -5855,7 +5855,7 @@ public:
   Optional<unsigned> getNumExpansions() const {
     if (PackExpansionTypeBits.NumExpansions)
       return PackExpansionTypeBits.NumExpansions - 1;
-    return None;
+    return std::nullopt;
   }
 
   bool isSugared() const { return false; }

clang/lib/AST/ASTContext.cpp

@@ -771,9 +771,9 @@ canonicalizeImmediatelyDeclaredConstraint(const ASTContext &C, Expr *IDC,
 
   if (auto *OrigFold = dyn_cast<CXXFoldExpr>(IDC))
     NewIDC = new (C) CXXFoldExpr(
-        OrigFold->getType(), /*Callee*/nullptr, SourceLocation(), NewIDC,
+        OrigFold->getType(), /*Callee*/ nullptr, SourceLocation(), NewIDC,
         BinaryOperatorKind::BO_LAnd, SourceLocation(), /*RHS=*/nullptr,
-        SourceLocation(), /*NumExpansions=*/None);
+        SourceLocation(), /*NumExpansions=*/std::nullopt);
   return NewIDC;
 }
 
@@ -797,12 +797,13 @@ ASTContext::getCanonicalTemplateTemplateParmDecl(
                                           PEnd = Params->end();
        P != PEnd; ++P) {
     if (const auto *TTP = dyn_cast<TemplateTypeParmDecl>(*P)) {
-      TemplateTypeParmDecl *NewTTP = TemplateTypeParmDecl::Create(*this,
+      TemplateTypeParmDecl *NewTTP = TemplateTypeParmDecl::Create(
-          getTranslationUnitDecl(), SourceLocation(), SourceLocation(),
+          *this, getTranslationUnitDecl(), SourceLocation(), SourceLocation(),
           TTP->getDepth(), TTP->getIndex(), nullptr, false,
           TTP->isParameterPack(), TTP->hasTypeConstraint(),
-          TTP->isExpandedParameterPack() ?
+          TTP->isExpandedParameterPack()
-          llvm::Optional<unsigned>(TTP->getNumExpansionParameters()) : None);
+              ? llvm::Optional<unsigned>(TTP->getNumExpansionParameters())
+              : std::nullopt);
       if (const auto *TC = TTP->getTypeConstraint()) {
         QualType ParamAsArgument(NewTTP->getTypeForDecl(), 0);
         Expr *NewIDC = canonicalizeImmediatelyDeclaredConstraint(
@@ -1139,7 +1140,7 @@ ASTContext::getModulesWithMergedDefinition(const NamedDecl *Def) {
   auto MergedIt =
       MergedDefModules.find(cast<NamedDecl>(Def->getCanonicalDecl()));
   if (MergedIt == MergedDefModules.end())
-    return None;
+    return std::nullopt;
   return MergedIt->second;
 }
 
@@ -1197,7 +1198,7 @@ void ASTContext::addLazyModuleInitializers(Module *M, ArrayRef<uint32_t> IDs) {
 ArrayRef<Decl *> ASTContext::getModuleInitializers(Module *M) {
   auto It = ModuleInitializers.find(M);
   if (It == ModuleInitializers.end())
-    return None;
+    return std::nullopt;
 
   auto *Inits = It->second;
   Inits->resolve(*this);
@@ -2743,7 +2744,7 @@ getSubobjectSizeInBits(const FieldDecl *Field, const ASTContext &Context) {
   bool IsBitIntType = Field->getType()->isBitIntType();
   if (!Field->getType()->isReferenceType() && !IsBitIntType &&
       !Context.hasUniqueObjectRepresentations(Field->getType()))
-    return llvm::None;
+    return std::nullopt;
 
   int64_t FieldSizeInBits =
       Context.toBits(Context.getTypeSizeInChars(Field->getType()));
@@ -2752,14 +2753,14 @@ getSubobjectSizeInBits(const FieldDecl *Field, const ASTContext &Context) {
     if (IsBitIntType) {
       if ((unsigned)BitfieldSize >
           cast<BitIntType>(Field->getType())->getNumBits())
-        return llvm::None;
+        return std::nullopt;
     } else if (BitfieldSize > FieldSizeInBits) {
-      return llvm::None;
+      return std::nullopt;
     }
     FieldSizeInBits = BitfieldSize;
   } else if (IsBitIntType &&
              !Context.hasUniqueObjectRepresentations(Field->getType())) {
-    return llvm::None;
+    return std::nullopt;
   }
   return FieldSizeInBits;
 }
@@ -2777,11 +2778,11 @@ static llvm::Optional<int64_t> structSubobjectsHaveUniqueObjectRepresentations(
     llvm::Optional<int64_t> SizeInBits =
         getSubobjectSizeInBits(Subobject, Context);
     if (!SizeInBits)
-      return llvm::None;
+      return std::nullopt;
     if (*SizeInBits != 0) {
       int64_t Offset = getSubobjectOffset(Subobject, Context, Layout);
       if (Offset != CurOffsetInBits)
-        return llvm::None;
+        return std::nullopt;
       CurOffsetInBits += *SizeInBits;
     }
   }
@@ -2797,7 +2798,7 @@ structHasUniqueObjectRepresentations(const ASTContext &Context,
   int64_t CurOffsetInBits = 0;
   if (const auto *ClassDecl = dyn_cast<CXXRecordDecl>(RD)) {
     if (ClassDecl->isDynamicClass())
-      return llvm::None;
+      return std::nullopt;
 
     SmallVector<CXXRecordDecl *, 4> Bases;
     for (const auto &Base : ClassDecl->bases()) {
@@ -2814,7 +2815,7 @@ structHasUniqueObjectRepresentations(const ASTContext &Context,
         structSubobjectsHaveUniqueObjectRepresentations(Bases, CurOffsetInBits,
                                                         Context, Layout);
     if (!OffsetAfterBases)
-      return llvm::None;
+      return std::nullopt;
     CurOffsetInBits = *OffsetAfterBases;
   }
 
@@ -2822,7 +2823,7 @@ structHasUniqueObjectRepresentations(const ASTContext &Context,
       structSubobjectsHaveUniqueObjectRepresentations(
           RD->fields(), CurOffsetInBits, Context, Layout);
   if (!OffsetAfterFields)
-    return llvm::None;
+    return std::nullopt;
   CurOffsetInBits = *OffsetAfterFields;
 
   return CurOffsetInBits;
@@ -5218,7 +5219,7 @@ TemplateArgument ASTContext::getInjectedTemplateArg(NamedDecl *Param) {
   if (const auto *TTP = dyn_cast<TemplateTypeParmDecl>(Param)) {
     QualType ArgType = getTypeDeclType(TTP);
     if (TTP->isParameterPack())
-      ArgType = getPackExpansionType(ArgType, None);
+      ArgType = getPackExpansionType(ArgType, std::nullopt);
 
     Arg = TemplateArgument(ArgType);
   } else if (auto *NTTP = dyn_cast<NonTypeTemplateParmDecl>(Param)) {
@@ -5235,8 +5236,8 @@ TemplateArgument ASTContext::getInjectedTemplateArg(NamedDecl *Param) {
         Expr::getValueKindForType(NTTP->getType()), NTTP->getLocation());
 
     if (NTTP->isParameterPack())
-      E = new (*this) PackExpansionExpr(DependentTy, E, NTTP->getLocation(),
+      E = new (*this)
-                                        None);
+          PackExpansionExpr(DependentTy, E, NTTP->getLocation(), std::nullopt);
     Arg = TemplateArgument(E);
   } else {
     auto *TTP = cast<TemplateTemplateParmDecl>(Param);
@@ -11923,7 +11924,7 @@ MangleContext *ASTContext::createDeviceMangleContext(const TargetInfo &T) {
         [](ASTContext &, const NamedDecl *ND) -> llvm::Optional<unsigned> {
           if (const auto *RD = dyn_cast<CXXRecordDecl>(ND))
             return RD->getDeviceLambdaManglingNumber();
-          return llvm::None;
+          return std::nullopt;
         },
         /*IsAux=*/true);
   case TargetCXXABI::Microsoft:

clang/lib/AST/ASTImporter.cpp

@@ -223,7 +223,7 @@ namespace clang {
     template<typename T>
     Expected<Optional<T>> import(Optional<T> From) {
       if (!From)
-        return None;
+        return std::nullopt;
       return import(*From);
     }
 
@@ -8544,7 +8544,7 @@ Optional<unsigned> ASTImporter::getFieldIndex(Decl *F) {
 
   auto *Owner = dyn_cast<RecordDecl>(F->getDeclContext());
   if (!Owner)
-    return None;
+    return std::nullopt;
 
   unsigned Index = 0;
   for (const auto *D : Owner->decls()) {
@@ -8557,7 +8557,7 @@ Optional<unsigned> ASTImporter::getFieldIndex(Decl *F) {
 
   llvm_unreachable("Field was not found in its parent context.");
 
-  return None;
+  return std::nullopt;
 }
 
 ASTImporter::FoundDeclsTy
@@ -10022,7 +10022,7 @@ ASTImporter::getImportDeclErrorIfAny(Decl *FromD) const {
   if (Pos != ImportDeclErrors.end())
     return Pos->second;
   else
-    return None;
+    return std::nullopt;
 }
 
 void ASTImporter::setImportDeclError(Decl *From, ASTImportError Error) {

clang/lib/AST/ASTStructuralEquivalence.cpp

@@ -2128,7 +2128,7 @@ StructuralEquivalenceContext::findUntaggedStructOrUnionIndex(RecordDecl *Anon) {
 
   const auto *Owner = dyn_cast<RecordDecl>(Anon->getDeclContext());
   if (!Owner)
-    return None;
+    return std::nullopt;
 
   unsigned Index = 0;
   for (const auto *D : Owner->noload_decls()) {

clang/lib/AST/AttrImpl.cpp

@@ -151,7 +151,7 @@ void OMPDeclareTargetDeclAttr::printPrettyPragma(
 llvm::Optional<OMPDeclareTargetDeclAttr *>
 OMPDeclareTargetDeclAttr::getActiveAttr(const ValueDecl *VD) {
   if (!VD->hasAttrs())
-    return llvm::None;
+    return std::nullopt;
   unsigned Level = 0;
   OMPDeclareTargetDeclAttr *FoundAttr = nullptr;
   for (auto *Attr : VD->specific_attrs<OMPDeclareTargetDeclAttr>()) {
@@ -162,7 +162,7 @@ OMPDeclareTargetDeclAttr::getActiveAttr(const ValueDecl *VD) {
   }
   if (FoundAttr)
     return FoundAttr;
-  return llvm::None;
+  return std::nullopt;
 }
 
 llvm::Optional<OMPDeclareTargetDeclAttr::MapTypeTy>
@@ -170,7 +170,7 @@ OMPDeclareTargetDeclAttr::isDeclareTargetDeclaration(const ValueDecl *VD) {
   llvm::Optional<OMPDeclareTargetDeclAttr *> ActiveAttr = getActiveAttr(VD);
   if (ActiveAttr)
     return ActiveAttr.value()->getMapType();
-  return llvm::None;
+  return std::nullopt;
 }
 
 llvm::Optional<OMPDeclareTargetDeclAttr::DevTypeTy>
@@ -178,7 +178,7 @@ OMPDeclareTargetDeclAttr::getDeviceType(const ValueDecl *VD) {
   llvm::Optional<OMPDeclareTargetDeclAttr *> ActiveAttr = getActiveAttr(VD);
   if (ActiveAttr)
     return ActiveAttr.value()->getDevType();
-  return llvm::None;
+  return std::nullopt;
 }
 
 llvm::Optional<SourceLocation>
@@ -186,7 +186,7 @@ OMPDeclareTargetDeclAttr::getLocation(const ValueDecl *VD) {
   llvm::Optional<OMPDeclareTargetDeclAttr *> ActiveAttr = getActiveAttr(VD);
   if (ActiveAttr)
     return ActiveAttr.value()->getRange().getBegin();
-  return llvm::None;
+  return std::nullopt;
 }
 
 namespace clang {

clang/lib/AST/Comment.cpp

@@ -206,7 +206,7 @@ void DeclInfo::fill() {
   IsInstanceMethod = false;
   IsClassMethod = false;
   IsVariadic = false;
-  ParamVars = None;
+  ParamVars = std::nullopt;
   TemplateParameters = nullptr;
 
   if (!CommentDecl) {

clang/lib/AST/CommentParser.cpp

@@ -334,7 +334,7 @@ BlockCommandComment *Parser::parseBlockCommand() {
   if (isTokBlockCommand()) {
     // Block command ahead.  We can't nest block commands, so pretend that this
     // command has an empty argument.
-    ParagraphComment *Paragraph = S.actOnParagraphComment(None);
+    ParagraphComment *Paragraph = S.actOnParagraphComment(std::nullopt);
     if (PC) {
       S.actOnParamCommandFinish(PC, Paragraph);
       return PC;
@@ -376,7 +376,7 @@ BlockCommandComment *Parser::parseBlockCommand() {
 
   ParagraphComment *Paragraph;
   if (EmptyParagraph)
-    Paragraph = S.actOnParagraphComment(None);
+    Paragraph = S.actOnParagraphComment(std::nullopt);
   else {
     BlockContentComment *Block = parseParagraphOrBlockCommand();
     // Since we have checked for a block command, we should have parsed a

clang/lib/AST/ComparisonCategories.cpp

@@ -37,7 +37,7 @@ clang::getComparisonCategoryForBuiltinCmp(QualType T) {
     return CCT::StrongOrdering;
 
   // TODO: Extend support for operator<=> to ObjC types.
-  return llvm::None;
+  return std::nullopt;
 }
 
 bool ComparisonCategoryInfo::ValueInfo::hasValidIntValue() const {

clang/lib/AST/Decl.cpp

@@ -235,7 +235,7 @@ static Optional<Visibility> getVisibilityOf(const NamedDecl *D,
     return getVisibilityFromAttr(A);
   }
 
-  return None;
+  return std::nullopt;
 }
 
 LinkageInfo LinkageComputer::getLVForType(const Type &T,
@@ -1194,11 +1194,11 @@ getExplicitVisibilityAux(const NamedDecl *ND,
     const auto *TD = spec->getSpecializedTemplate()->getTemplatedDecl();
     while (TD != nullptr) {
       auto Vis = getVisibilityOf(TD, kind);
-      if (Vis != None)
+      if (Vis != std::nullopt)
         return Vis;
       TD = TD->getPreviousDecl();
     }
-    return None;
+    return std::nullopt;
   }
 
   // Use the most recent declaration.
@@ -1219,7 +1219,7 @@ getExplicitVisibilityAux(const NamedDecl *ND,
       return getVisibilityOf(VTSD->getSpecializedTemplate()->getTemplatedDecl(),
                              kind);
 
-    return None;
+    return std::nullopt;
   }
   // Also handle function template specializations.
   if (const auto *fn = dyn_cast<FunctionDecl>(ND)) {
@@ -1236,14 +1236,14 @@ getExplicitVisibilityAux(const NamedDecl *ND,
     if (InstantiatedFrom)
       return getVisibilityOf(InstantiatedFrom, kind);
 
-    return None;
+    return std::nullopt;
   }
 
   // The visibility of a template is stored in the templated decl.
   if (const auto *TD = dyn_cast<TemplateDecl>(ND))
     return getVisibilityOf(TD->getTemplatedDecl(), kind);
 
-  return None;
+  return std::nullopt;
 }
 
 Optional<Visibility>
@@ -5130,8 +5130,9 @@ IndirectFieldDecl::Create(ASTContext &C, DeclContext *DC, SourceLocation L,
 
 IndirectFieldDecl *IndirectFieldDecl::CreateDeserialized(ASTContext &C,
                                                          unsigned ID) {
-  return new (C, ID) IndirectFieldDecl(C, nullptr, SourceLocation(),
+  return new (C, ID)
-                                       DeclarationName(), QualType(), None);
+      IndirectFieldDecl(C, nullptr, SourceLocation(), DeclarationName(),
+                        QualType(), std::nullopt);
 }
 
 SourceRange EnumConstantDecl::getSourceRange() const {
@@ -5362,7 +5363,7 @@ ImportDecl *ImportDecl::CreateDeserialized(ASTContext &C, unsigned ID,
 
 ArrayRef<SourceLocation> ImportDecl::getIdentifierLocs() const {
   if (!isImportComplete())
-    return None;
+    return std::nullopt;
 
   const auto *StoredLocs = getTrailingObjects<SourceLocation>();
   return llvm::makeArrayRef(StoredLocs,

clang/lib/AST/DeclCXX.cpp

@@ -3139,7 +3139,8 @@ UsingPackDecl *UsingPackDecl::Create(ASTContext &C, DeclContext *DC,
 UsingPackDecl *UsingPackDecl::CreateDeserialized(ASTContext &C, unsigned ID,
                                                  unsigned NumExpansions) {
   size_t Extra = additionalSizeToAlloc<NamedDecl *>(NumExpansions);
-  auto *Result = new (C, ID, Extra) UsingPackDecl(nullptr, nullptr, None);
+  auto *Result =
+      new (C, ID, Extra) UsingPackDecl(nullptr, nullptr, std::nullopt);
   Result->NumExpansions = NumExpansions;
   auto *Trail = Result->getTrailingObjects<NamedDecl *>();
   for (unsigned I = 0; I != NumExpansions; ++I)
@@ -3277,7 +3278,7 @@ DecompositionDecl *DecompositionDecl::CreateDeserialized(ASTContext &C,
   size_t Extra = additionalSizeToAlloc<BindingDecl *>(NumBindings);
   auto *Result = new (C, ID, Extra)
       DecompositionDecl(C, nullptr, SourceLocation(), SourceLocation(),
-                        QualType(), nullptr, StorageClass(), None);
+                        QualType(), nullptr, StorageClass(), std::nullopt);
   // Set up and clean out the bindings array.
   Result->NumBindings = NumBindings;
   auto *Trail = Result->getTrailingObjects<BindingDecl *>();

clang/lib/AST/DeclObjC.cpp

@@ -910,12 +910,12 @@ void ObjCMethodDecl::setMethodParams(ASTContext &C,
   assert((!SelLocs.empty() || isImplicit()) &&
          "No selector locs for non-implicit method");
   if (isImplicit())
-    return setParamsAndSelLocs(C, Params, llvm::None);
+    return setParamsAndSelLocs(C, Params, std::nullopt);
 
   setSelLocsKind(hasStandardSelectorLocs(getSelector(), SelLocs, Params,
                                         DeclEndLoc));
   if (getSelLocsKind() != SelLoc_NonStandard)
-    return setParamsAndSelLocs(C, Params, llvm::None);
+    return setParamsAndSelLocs(C, Params, std::nullopt);
 
   setParamsAndSelLocs(C, Params, SelLocs);
 }

clang/lib/AST/DeclOpenMP.cpp

@@ -30,7 +30,7 @@ OMPThreadPrivateDecl *OMPThreadPrivateDecl::Create(ASTContext &C,
                                                    SourceLocation L,
                                                    ArrayRef<Expr *> VL) {
   auto *D = OMPDeclarativeDirective::createDirective<OMPThreadPrivateDecl>(
-      C, DC, llvm::None, VL.size(), L);
+      C, DC, std::nullopt, VL.size(), L);
   D->setVars(VL);
   return D;
 }

clang/lib/AST/DeclTemplate.cpp

@@ -656,9 +656,9 @@ TemplateTypeParmDecl::Create(const ASTContext &C, DeclContext *DC,
 
 TemplateTypeParmDecl *
 TemplateTypeParmDecl::CreateDeserialized(const ASTContext &C, unsigned ID) {
-  return new (C, ID) TemplateTypeParmDecl(nullptr, SourceLocation(),
+  return new (C, ID)
-                                          SourceLocation(), nullptr, false,
+      TemplateTypeParmDecl(nullptr, SourceLocation(), SourceLocation(), nullptr,
-                                          false, None);
+                           false, false, std::nullopt);
 }
 
 TemplateTypeParmDecl *
@@ -666,8 +666,8 @@ TemplateTypeParmDecl::CreateDeserialized(const ASTContext &C, unsigned ID,
                                          bool HasTypeConstraint) {
   return new (C, ID,
               additionalSizeToAlloc<TypeConstraint>(HasTypeConstraint ? 1 : 0))
-         TemplateTypeParmDecl(nullptr, SourceLocation(), SourceLocation(),
+      TemplateTypeParmDecl(nullptr, SourceLocation(), SourceLocation(), nullptr,
-                              nullptr, false, HasTypeConstraint, None);
+                           false, HasTypeConstraint, std::nullopt);
 }
 
 SourceLocation TemplateTypeParmDecl::getDefaultArgumentLoc() const {
@@ -781,12 +781,12 @@ NonTypeTemplateParmDecl::CreateDeserialized(ASTContext &C, unsigned ID,
                                             unsigned NumExpandedTypes,
                                             bool HasTypeConstraint) {
   auto *NTTP =
-      new (C, ID, additionalSizeToAlloc<std::pair<QualType, TypeSourceInfo *>,
+      new (C, ID,
-                                        Expr *>(
+           additionalSizeToAlloc<std::pair<QualType, TypeSourceInfo *>, Expr *>(
                NumExpandedTypes, HasTypeConstraint ? 1 : 0))
           NonTypeTemplateParmDecl(nullptr, SourceLocation(), SourceLocation(),
-                                  0, 0, nullptr, QualType(), nullptr, None,
+                                  0, 0, nullptr, QualType(), nullptr,
-                                  None);
+                                  std::nullopt, std::nullopt);
   NTTP->NumExpandedTypes = NumExpandedTypes;
   return NTTP;
 }
@@ -854,7 +854,7 @@ TemplateTemplateParmDecl::CreateDeserialized(ASTContext &C, unsigned ID,
   auto *TTP =
       new (C, ID, additionalSizeToAlloc<TemplateParameterList *>(NumExpansions))
           TemplateTemplateParmDecl(nullptr, SourceLocation(), 0, 0, nullptr,
-                                   nullptr, None);
+                                   nullptr, std::nullopt);
   TTP->NumExpandedParams = NumExpansions;
   return TTP;
 }

clang/lib/AST/Expr.cpp

@@ -647,7 +647,7 @@ std::string SYCLUniqueStableNameExpr::ComputeName(ASTContext &Context,
                            const NamedDecl *ND) -> llvm::Optional<unsigned> {
     if (const auto *RD = dyn_cast<CXXRecordDecl>(ND))
       return RD->getDeviceLambdaManglingNumber();
-    return llvm::None;
+    return std::nullopt;
   };
 
   std::unique_ptr<MangleContext> Ctx{ItaniumMangleContext::create(
@@ -4533,7 +4533,8 @@ DesignatedInitUpdateExpr::DesignatedInitUpdateExpr(const ASTContext &C,
            OK_Ordinary) {
   BaseAndUpdaterExprs[0] = baseExpr;
 
-  InitListExpr *ILE = new (C) InitListExpr(C, lBraceLoc, None, rBraceLoc);
+  InitListExpr *ILE =
+      new (C) InitListExpr(C, lBraceLoc, std::nullopt, rBraceLoc);
   ILE->setType(baseExpr->getType());
   BaseAndUpdaterExprs[1] = ILE;
 

clang/lib/AST/ExprConstant.cpp

@@ -5680,7 +5680,7 @@ static Optional<DynamicType> ComputeDynamicType(EvalInfo &Info, const Expr *E,
   // meaningful dynamic type. (We consider objects of non-class type to have no
   // dynamic type.)
   if (!checkDynamicType(Info, E, This, AK, true))
-    return None;
+    return std::nullopt;
 
   // Refuse to compute a dynamic type in the presence of virtual bases. This
   // shouldn't happen other than in constant-folding situations, since literal
@@ -5692,7 +5692,7 @@ static Optional<DynamicType> ComputeDynamicType(EvalInfo &Info, const Expr *E,
       This.Designator.MostDerivedType->getAsCXXRecordDecl();
   if (!Class || Class->getNumVBases()) {
     Info.FFDiag(E);
-    return None;
+    return std::nullopt;
   }
 
   // FIXME: For very deep class hierarchies, it might be beneficial to use a
@@ -5725,7 +5725,7 @@ static Optional<DynamicType> ComputeDynamicType(EvalInfo &Info, const Expr *E,
   // 'This', so that object has not yet begun its period of construction and
   // any polymorphic operation on it results in undefined behavior.
   Info.FFDiag(E);
-  return None;
+  return std::nullopt;
 }
 
 /// Perform virtual dispatch.
@@ -6753,13 +6753,13 @@ static Optional<DynAlloc *> CheckDeleteKind(EvalInfo &Info, const Expr *E,
         << PointerAsString();
     if (Pointer.Base)
       NoteLValueLocation(Info, Pointer.Base);
-    return None;
+    return std::nullopt;
   }
 
   Optional<DynAlloc *> Alloc = Info.lookupDynamicAlloc(DA);
   if (!Alloc) {
     Info.FFDiag(E, diag::note_constexpr_double_delete);
-    return None;
+    return std::nullopt;
   }
 
   QualType AllocType = Pointer.Base.getDynamicAllocType();
@@ -6767,7 +6767,7 @@ static Optional<DynAlloc *> CheckDeleteKind(EvalInfo &Info, const Expr *E,
     Info.FFDiag(E, diag::note_constexpr_new_delete_mismatch)
         << DeallocKind << (*Alloc)->getKind() << AllocType;
     NoteLValueLocation(Info, Pointer.Base);
-    return None;
+    return std::nullopt;
   }
 
   bool Subobject = false;
@@ -6781,7 +6781,7 @@ static Optional<DynAlloc *> CheckDeleteKind(EvalInfo &Info, const Expr *E,
   if (Subobject) {
     Info.FFDiag(E, diag::note_constexpr_delete_subobject)
         << PointerAsString() << Pointer.Designator.isOnePastTheEnd();
-    return None;
+    return std::nullopt;
   }
 
   return Alloc;
@@ -7028,7 +7028,7 @@ public:
     CharUnits DstSize = Info.Ctx.getTypeSizeInChars(BCE->getType());
     APValueToBufferConverter Converter(Info, DstSize, BCE);
     if (!Converter.visit(Src, BCE->getSubExpr()->getType()))
-      return None;
+      return std::nullopt;
     return Converter.Buffer;
   }
 };
@@ -7050,14 +7050,14 @@ class BufferToAPValueConverter {
     Info.FFDiag(BCE->getBeginLoc(),
                 diag::note_constexpr_bit_cast_unsupported_type)
         << Ty;
-    return None;
+    return std::nullopt;
   }
 
   std::nullopt_t unrepresentableValue(QualType Ty, const APSInt &Val) {
     Info.FFDiag(BCE->getBeginLoc(),
                 diag::note_constexpr_bit_cast_unrepresentable_value)
         << Ty << toString(Val, /*Radix=*/10);
-    return None;
+    return std::nullopt;
   }
 
   Optional<APValue> visit(const BuiltinType *T, CharUnits Offset,
@@ -7097,7 +7097,7 @@ class BufferToAPValueConverter {
         Info.FFDiag(BCE->getExprLoc(),
                     diag::note_constexpr_bit_cast_indet_dest)
             << DisplayType << Info.Ctx.getLangOpts().CharIsSigned;
-        return None;
+        return std::nullopt;
       }
 
       return APValue::IndeterminateValue();
@@ -7152,7 +7152,7 @@ class BufferToAPValueConverter {
         Optional<APValue> SubObj = visitType(
             BS.getType(), Layout.getBaseClassOffset(BaseDecl) + Offset);
         if (!SubObj)
-          return None;
+          return std::nullopt;
         ResultVal.getStructBase(I) = *SubObj;
       }
     }
@@ -7165,7 +7165,7 @@ class BufferToAPValueConverter {
       if (FD->isBitField()) {
         Info.FFDiag(BCE->getBeginLoc(),
                     diag::note_constexpr_bit_cast_unsupported_bitfield);
-        return None;
+        return std::nullopt;
       }
 
       uint64_t FieldOffsetBits = Layout.getFieldOffset(FieldIdx);
@@ -7177,7 +7177,7 @@ class BufferToAPValueConverter {
       QualType FieldTy = FD->getType();
       Optional<APValue> SubObj = visitType(FieldTy, FieldOffset);
       if (!SubObj)
-        return None;
+        return std::nullopt;
       ResultVal.getStructField(FieldIdx) = *SubObj;
       ++FieldIdx;
     }
@@ -7205,7 +7205,7 @@ class BufferToAPValueConverter {
       Optional<APValue> ElementValue =
           visitType(Ty->getElementType(), Offset + I * ElementWidth);
       if (!ElementValue)
-        return None;
+        return std::nullopt;
       ArrayValue.getArrayInitializedElt(I) = std::move(*ElementValue);
     }
 
@@ -10571,7 +10571,7 @@ static llvm::Optional<APValue> handleVectorUnaryOperator(ASTContext &Ctx,
   }
   default:
     // FIXME: Implement the rest of the unary operators.
-    return llvm::None;
+    return std::nullopt;
   }
 }
 
@@ -15943,7 +15943,7 @@ Optional<llvm::APSInt> Expr::getIntegerConstantExpr(const ASTContext &Ctx,
                                                     bool isEvaluated) const {
   if (isValueDependent()) {
     // Expression evaluator can't succeed on a dependent expression.
-    return None;
+    return std::nullopt;
   }
 
   APSInt Value;
@@ -15951,11 +15951,11 @@ Optional<llvm::APSInt> Expr::getIntegerConstantExpr(const ASTContext &Ctx,
   if (Ctx.getLangOpts().CPlusPlus11) {
     if (EvaluateCPlusPlus11IntegralConstantExpr(Ctx, this, &Value, Loc))
       return Value;
-    return None;
+    return std::nullopt;
   }
 
   if (!isIntegerConstantExpr(Ctx, Loc))
-    return None;
+    return std::nullopt;
 
   // The only possible side-effects here are due to UB discovered in the
   // evaluation (for instance, INT_MAX + 1). In such a case, we are still

clang/lib/AST/ExternalASTSource.cpp

@@ -32,7 +32,7 @@ ExternalASTSource::~ExternalASTSource() = default;
 
 llvm::Optional<ASTSourceDescriptor>
 ExternalASTSource::getSourceDescriptor(unsigned ID) {
-  return None;
+  return std::nullopt;
 }
 
 ExternalASTSource::ExtKind

clang/lib/AST/FormatString.cpp

@@ -740,7 +740,7 @@ ConversionSpecifier::getStandardSpecifier() const {
 
   switch (getKind()) {
   default:
-    return None;
+    return std::nullopt;
   case DArg:
     NewKind = dArg;
     break;
@@ -1041,7 +1041,7 @@ Optional<LengthModifier> FormatSpecifier::getCorrectedLengthModifier() const {
     }
   }
 
-  return None;
+  return std::nullopt;
 }
 
 bool FormatSpecifier::namedTypeToLengthModifier(QualType QT,

clang/lib/AST/ItaniumCXXABI.cpp

@@ -96,7 +96,7 @@ Optional<bool> areDenseMapKeysEqualSpecialValues(T LHS, T RHS) {
   if (LHSTombstone || RHSTombstone)
     return LHSTombstone && RHSTombstone;
 
-  return None;
+  return std::nullopt;
 }
 
 template<>

clang/lib/AST/ItaniumMangle.cpp

@@ -6560,7 +6560,7 @@ ItaniumMangleContext *ItaniumMangleContext::create(ASTContext &Context,
   return new ItaniumMangleContextImpl(
       Context, Diags,
       [](ASTContext &, const NamedDecl *) -> llvm::Optional<unsigned> {
-        return llvm::None;
+        return std::nullopt;
       },
       IsAux);
 }

clang/lib/AST/Linkage.h

@@ -95,7 +95,7 @@ class LinkageComputer {
                                      LVComputationKind Kind) const {
     auto Iter = CachedLinkageInfo.find(makeCacheKey(ND, Kind));
     if (Iter == CachedLinkageInfo.end())
-      return None;
+      return std::nullopt;
     return Iter->second;
   }
 

clang/lib/AST/MicrosoftMangle.cpp

@@ -376,7 +376,7 @@ public:
   void mangleBits(llvm::APInt Number);
   void mangleTagTypeKind(TagTypeKind TK);
   void mangleArtificialTagType(TagTypeKind TK, StringRef UnqualifiedName,
-                              ArrayRef<StringRef> NestedNames = None);
+                               ArrayRef<StringRef> NestedNames = std::nullopt);
   void mangleAddressSpaceType(QualType T, Qualifiers Quals, SourceRange Range);
   void mangleType(QualType T, SourceRange Range,
                   QualifierMangleMode QMM = QMM_Mangle);

clang/lib/AST/NSAPI.cpp

@@ -149,7 +149,7 @@ Optional<NSAPI::NSArrayMethodKind> NSAPI::getNSArrayMethodKind(Selector Sel) {
       return MK;
   }
 
-  return None;
+  return std::nullopt;
 }
 
 Selector NSAPI::getNSDictionarySelector(
@@ -251,7 +251,7 @@ NSAPI::getNSDictionaryMethodKind(Selector Sel) {
       return MK;
   }
 
-  return None;
+  return std::nullopt;
 }
 
 Selector NSAPI::getNSSetSelector(NSSetMethodKind MK) const {
@@ -308,7 +308,7 @@ NSAPI::getNSSetMethodKind(Selector Sel) {
       return MK;
   }
 
-  return None;
+  return std::nullopt;
 }
 
 Selector NSAPI::getNSNumberLiteralSelector(NSNumberLiteralMethodKind MK,
@@ -371,14 +371,14 @@ NSAPI::getNSNumberLiteralMethodKind(Selector Sel) const {
       return MK;
   }
 
-  return None;
+  return std::nullopt;
 }
 
 Optional<NSAPI::NSNumberLiteralMethodKind>
 NSAPI::getNSNumberFactoryMethodKind(QualType T) const {
   const BuiltinType *BT = T->getAs<BuiltinType>();
   if (!BT)
-    return None;
+    return std::nullopt;
 
   const TypedefType *TDT = T->getAs<TypedefType>();
   if (TDT) {
@@ -496,7 +496,7 @@ NSAPI::getNSNumberFactoryMethodKind(QualType T) const {
     break;
   }
 
-  return None;
+  return std::nullopt;
 }
 
 /// Returns true if \param T is a typedef of "BOOL" in objective-c.

clang/lib/AST/Stmt.cpp

@@ -1003,7 +1003,7 @@ bool IfStmt::isObjCAvailabilityCheck() const {
 
 Optional<Stmt *> IfStmt::getNondiscardedCase(const ASTContext &Ctx) {
   if (!isConstexpr() || getCond()->isValueDependent())
-    return None;
+    return std::nullopt;
   return !getCond()->EvaluateKnownConstInt(Ctx) ? getElse() : getThen();
 }
 
@@ -1012,7 +1012,7 @@ IfStmt::getNondiscardedCase(const ASTContext &Ctx) const {
   if (Optional<Stmt *> Result =
           const_cast<IfStmt *>(this)->getNondiscardedCase(Ctx))
     return *Result;
-  return None;
+  return std::nullopt;
 }
 
 ForStmt::ForStmt(const ASTContext &C, Stmt *Init, Expr *Cond, VarDecl *condVar,

clang/lib/AST/StmtOpenMP.cpp

@@ -517,7 +517,7 @@ OMPSectionDirective *OMPSectionDirective::Create(const ASTContext &C,
                                                  Stmt *AssociatedStmt,
                                                  bool HasCancel) {
   auto *Dir =
-      createDirective<OMPSectionDirective>(C, llvm::None, AssociatedStmt,
+      createDirective<OMPSectionDirective>(C, std::nullopt, AssociatedStmt,
                                            /*NumChildren=*/0, StartLoc, EndLoc);
   Dir->setHasCancel(HasCancel);
   return Dir;
@@ -550,7 +550,7 @@ OMPMasterDirective *OMPMasterDirective::Create(const ASTContext &C,
                                                SourceLocation StartLoc,
                                                SourceLocation EndLoc,
                                                Stmt *AssociatedStmt) {
-  return createDirective<OMPMasterDirective>(C, llvm::None, AssociatedStmt,
+  return createDirective<OMPMasterDirective>(C, std::nullopt, AssociatedStmt,
                                              /*NumChildren=*/0, StartLoc,
                                              EndLoc);
 }

clang/lib/AST/TemplateBase.cpp

@@ -276,7 +276,7 @@ Optional<unsigned> TemplateArgument::getNumTemplateExpansions() const {
   if (TemplateArg.NumExpansions)
     return TemplateArg.NumExpansions - 1;
 
-  return None;
+  return std::nullopt;
 }
 
 QualType TemplateArgument::getNonTypeTemplateArgumentType() const {

clang/lib/AST/Type.cpp

@@ -1527,23 +1527,23 @@ Optional<ArrayRef<QualType>> Type::getObjCSubstitutions(
     // substitution to do.
     dcTypeParams = dcClassDecl->getTypeParamList();
     if (!dcTypeParams)
-      return None;
+      return std::nullopt;
   } else {
     // If we are in neither a class nor a category, there's no
     // substitution to perform.
     dcCategoryDecl = dyn_cast<ObjCCategoryDecl>(dc);
     if (!dcCategoryDecl)
-      return None;
+      return std::nullopt;
 
     // If the category does not have any type parameters, there's no
     // substitution to do.
     dcTypeParams = dcCategoryDecl->getTypeParamList();
     if (!dcTypeParams)
-      return None;
+      return std::nullopt;
 
     dcClassDecl = dcCategoryDecl->getClassInterface();
     if (!dcClassDecl)
-      return None;
+      return std::nullopt;
   }
   assert(dcTypeParams && "No substitutions to perform");
   assert(dcClassDecl && "No class context");
@@ -4153,7 +4153,7 @@ Type::getNullability(const ASTContext &Context) const {
 
     Type = AT->getEquivalentType();
   }
-  return None;
+  return std::nullopt;
 }
 
 bool Type::canHaveNullability(bool ResultIfUnknown) const {
@@ -4294,7 +4294,7 @@ AttributedType::getImmediateNullability() const {
     return NullabilityKind::Unspecified;
   if (getAttrKind() == attr::TypeNullableResult)
     return NullabilityKind::NullableResult;
-  return None;
+  return std::nullopt;
 }
 
 Optional<NullabilityKind> AttributedType::stripOuterNullability(QualType &T) {
@@ -4309,7 +4309,7 @@ Optional<NullabilityKind> AttributedType::stripOuterNullability(QualType &T) {
     }
   }
 
-  return None;
+  return std::nullopt;
 }
 
 bool Type::isBlockCompatibleObjCPointerType(ASTContext &ctx) const {