[clang] Use {} instead of std::nullopt to initialize empty ArrayRef (#109399)

Follow up to #109133.

Author: jayfoad

clang/include/clang/AST/CommentSema.h

@@ -80,7 +80,7 @@ class Sema {
   ArrayRef<T> copyArray(ArrayRef<T> Source) {
     if (!Source.empty())
       return Source.copy(Allocator);
-    return std::nullopt;
+    return {};
   }
 
   ParagraphComment *actOnParagraphComment(

clang/include/clang/AST/DeclFriend.h

@@ -115,7 +115,7 @@ class FriendDecl final
   static FriendDecl *
   Create(ASTContext &C, DeclContext *DC, SourceLocation L, FriendUnion Friend_,
          SourceLocation FriendL, SourceLocation EllipsisLoc = {},
-         ArrayRef<TemplateParameterList *> FriendTypeTPLists = std::nullopt);
+         ArrayRef<TemplateParameterList *> FriendTypeTPLists = {});
   static FriendDecl *CreateDeserialized(ASTContext &C, GlobalDeclID ID,
                                         unsigned FriendTypeNumTPLists);
 

clang/include/clang/AST/DeclObjC.h

@@ -386,7 +386,7 @@ class ObjCMethodDecl : public NamedDecl, public DeclContext {
   /// If the method is implicit (not coming from source) \p SelLocs is
   /// ignored.
   void setMethodParams(ASTContext &C, ArrayRef<ParmVarDecl *> Params,
-                       ArrayRef<SourceLocation> SelLocs = std::nullopt);
+                       ArrayRef<SourceLocation> SelLocs = {});
 
   // 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 std::nullopt;
+      return {};
     return Data->getClauses();
   }
 
@@ -90,7 +90,7 @@ template <typename U> class OMPDeclarativeDirective : public U {
 
   ArrayRef<OMPClause *> clauses() const {
     if (!Data)
-      return std::nullopt;
+      return {};
     return Data->getClauses();
   }
 };

clang/include/clang/AST/ExprCXX.h

@@ -4306,11 +4306,11 @@ class SizeOfPackExpr final
       : Expr(SizeOfPackExprClass, Empty), Length(NumPartialArgs) {}
 
 public:
-  static SizeOfPackExpr *
-  Create(ASTContext &Context, SourceLocation OperatorLoc, NamedDecl *Pack,
-         SourceLocation PackLoc, SourceLocation RParenLoc,
-         std::optional<unsigned> Length = std::nullopt,
-         ArrayRef<TemplateArgument> PartialArgs = std::nullopt);
+  static SizeOfPackExpr *Create(ASTContext &Context, SourceLocation OperatorLoc,
+                                NamedDecl *Pack, SourceLocation PackLoc,
+                                SourceLocation RParenLoc,
+                                std::optional<unsigned> Length = std::nullopt,
+                                ArrayRef<TemplateArgument> PartialArgs = {});
   static SizeOfPackExpr *CreateDeserialized(ASTContext &Context,
                                             unsigned NumPartialArgs);
 

clang/include/clang/AST/OpenMPClause.h

@@ -6108,14 +6108,14 @@ class OMPMappableExprListClause : public OMPVarListClause<T>,
     return const_component_lists_iterator(
         getUniqueDeclsRef(), getDeclNumListsRef(), getComponentListSizesRef(),
         getComponentsRef(), SupportsMapper,
-        SupportsMapper ? getUDMapperRefs() : std::nullopt);
+        SupportsMapper ? getUDMapperRefs() : ArrayRef<Expr *>());
   }
   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, std::nullopt);
+        SupportsMapper, {});
   }
   const_component_lists_range component_lists() const {
     return {component_lists_begin(), component_lists_end()};
@@ -6128,7 +6128,7 @@ class OMPMappableExprListClause : public OMPVarListClause<T>,
     return const_component_lists_iterator(
         VD, getUniqueDeclsRef(), getDeclNumListsRef(),
         getComponentListSizesRef(), getComponentsRef(), SupportsMapper,
-        SupportsMapper ? getUDMapperRefs() : std::nullopt);
+        SupportsMapper ? getUDMapperRefs() : ArrayRef<Expr *>());
   }
   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 std::nullopt;
+      return {};
     return Data->getClauses();
   }
 
@@ -572,7 +572,7 @@ class OMPExecutableDirective : public Stmt {
 
   ArrayRef<OMPClause *> clauses() const {
     if (!Data)
-      return std::nullopt;
+      return {};
     return Data->getClauses();
   }
 

clang/include/clang/AST/TemplateBase.h

@@ -283,7 +283,7 @@ class TemplateArgument {
   }
 
   static TemplateArgument getEmptyPack() {
-    return TemplateArgument(std::nullopt);
+    return TemplateArgument(ArrayRef<TemplateArgument>());
   }
 
   /// Create a new template argument pack by copying the given set of

clang/include/clang/ASTMatchers/ASTMatchersInternal.h

@@ -121,7 +121,7 @@ template <typename T> struct TypeListContainsSuperOf<EmptyTypeList, T> {
 template <typename ResultT, typename ArgT,
           ResultT (*Func)(ArrayRef<const ArgT *>)>
 struct VariadicFunction {
-  ResultT operator()() const { return Func(std::nullopt); }
+  ResultT operator()() const { return Func({}); }
 
   template <typename... ArgsT>
   ResultT operator()(const ArgT &Arg1, const ArgsT &... Args) const {
@@ -1949,35 +1949,35 @@ inline ArrayRef<TemplateArgument>
 getTemplateSpecializationArgs(const FunctionDecl &FD) {
   if (const auto* TemplateArgs = FD.getTemplateSpecializationArgs())
     return TemplateArgs->asArray();
-  return std::nullopt;
+  return {};
 }
 
 inline ArrayRef<TemplateArgumentLoc>
 getTemplateArgsWritten(const ClassTemplateSpecializationDecl &D) {
   if (const ASTTemplateArgumentListInfo *Args = D.getTemplateArgsAsWritten())
     return Args->arguments();
-  return std::nullopt;
+  return {};
 }
 
 inline ArrayRef<TemplateArgumentLoc>
 getTemplateArgsWritten(const VarTemplateSpecializationDecl &D) {
   if (const ASTTemplateArgumentListInfo *Args = D.getTemplateArgsAsWritten())
     return Args->arguments();
-  return std::nullopt;
+  return {};
 }
 
 inline ArrayRef<TemplateArgumentLoc>
 getTemplateArgsWritten(const FunctionDecl &FD) {
   if (const auto *Args = FD.getTemplateSpecializationArgsAsWritten())
     return Args->arguments();
-  return std::nullopt;
+  return {};
 }
 
 inline ArrayRef<TemplateArgumentLoc>
 getTemplateArgsWritten(const DeclRefExpr &DRE) {
   if (const auto *Args = DRE.getTemplateArgs())
     return {Args, DRE.getNumTemplateArgs()};
-  return std::nullopt;
+  return {};
 }
 
 inline SmallVector<TemplateArgumentLoc>

clang/include/clang/Analysis/Analyses/ThreadSafetyTIL.h

@@ -1470,7 +1470,7 @@ class Return : public Terminator {
   static bool classof(const SExpr *E) { return E->opcode() == COP_Return; }
 
   /// Return an empty list.
-  ArrayRef<BasicBlock *> successors() { return std::nullopt; }
+  ArrayRef<BasicBlock *> successors() { return {}; }
 
   SExpr *returnValue() { return Retval; }
   const SExpr *returnValue() const { return Retval; }
@@ -1496,7 +1496,7 @@ inline ArrayRef<BasicBlock*> Terminator::successors() {
     case COP_Branch: return cast<Branch>(this)->successors();
     case COP_Return: return cast<Return>(this)->successors();
     default:
-      return std::nullopt;
+      return {};
   }
 }