[clang] Migrate away from ArrayRef(std::nullopt) (NFC) (#144982)

ArrayRef has a constructor that accepts std::nullopt.  This
constructor dates back to the days when we still had llvm::Optional.

Since the use of std::nullopt outside the context of std::optional is
kind of abuse and not intuitive to new comers, I would like to move
away from the constructor and eventually remove it.

This patch takes care of the clang side of the migration.

Author: kazutakahirata

clang/include/clang/AST/TypeProperties.td

@@ -753,7 +753,7 @@ let Class = TemplateSpecializationType in {
   }
 
   def : Creator<[{
-    return ctx.getTemplateSpecializationType(templateName, args, std::nullopt, UnderlyingType);
+    return ctx.getTemplateSpecializationType(templateName, args, {}, UnderlyingType);
   }]>;
 }
 

clang/lib/AST/ASTContext.cpp

@@ -14283,7 +14283,7 @@ static QualType getCommonNonSugarTypeNode(ASTContext &Ctx, const Type *X,
         ::getCommonTemplateNameChecked(Ctx, TX->getTemplateName(),
                                        TY->getTemplateName(),
                                        /*IgnoreDeduced=*/true),
-        As, /*CanonicalArgs=*/std::nullopt, X->getCanonicalTypeInternal());
+        As, /*CanonicalArgs=*/{}, X->getCanonicalTypeInternal());
   }
   case Type::Decltype: {
     const auto *DX = cast<DecltypeType>(X);
@@ -14529,7 +14529,7 @@ static QualType getCommonSugarTypeNode(ASTContext &Ctx, const Type *X,
                                    TY->template_arguments()))
       return QualType();
     return Ctx.getTemplateSpecializationType(CTN, As,
-                                             /*CanonicalArgs=*/std::nullopt,
+                                             /*CanonicalArgs=*/{},
                                              Ctx.getQualifiedType(Underlying));
   }
   case Type::Typedef: {

clang/lib/AST/ASTDiagnostic.cpp

@@ -130,7 +130,7 @@ QualType clang::desugarForDiagnostic(ASTContext &Context, QualType QT,
         if (DesugarArgument) {
           ShouldAKA = true;
           QT = Context.getTemplateSpecializationType(
-              TST->getTemplateName(), Args, /*CanonicalArgs=*/std::nullopt, QT);
+              TST->getTemplateName(), Args, /*CanonicalArgs=*/{}, QT);
         }
         break;
       }
@@ -1143,7 +1143,7 @@ class TemplateDiff {
 
     Ty = Context.getTemplateSpecializationType(
         TemplateName(CTSD->getSpecializedTemplate()),
-        CTSD->getTemplateArgs().asArray(), /*CanonicalArgs=*/std::nullopt,
+        CTSD->getTemplateArgs().asArray(), /*CanonicalArgs=*/{},
         Ty.getLocalUnqualifiedType().getCanonicalType());
 
     return Ty->getAs<TemplateSpecializationType>();

clang/lib/AST/ASTImporter.cpp

@@ -1664,7 +1664,7 @@ ExpectedType ASTNodeImporter::VisitTemplateSpecializationType(
   if (!ToUnderlyingOrErr)
     return ToUnderlyingOrErr.takeError();
   return Importer.getToContext().getTemplateSpecializationType(
-      *ToTemplateOrErr, ToTemplateArgs, std::nullopt, *ToUnderlyingOrErr);
+      *ToTemplateOrErr, ToTemplateArgs, {}, *ToUnderlyingOrErr);
 }
 
 ExpectedType ASTNodeImporter::VisitElaboratedType(const ElaboratedType *T) {

clang/lib/AST/DeclTemplate.cpp

@@ -669,7 +669,7 @@ ClassTemplateDecl::getInjectedClassNameSpecialization() {
   CommonPtr->InjectedClassNameType =
       Context.getTemplateSpecializationType(Name,
                                             /*SpecifiedArgs=*/TemplateArgs,
-                                            /*CanonicalArgs=*/std::nullopt);
+                                            /*CanonicalArgs=*/{});
   return CommonPtr->InjectedClassNameType;
 }
 

clang/lib/AST/QualTypeNames.cpp

@@ -140,7 +140,7 @@ static const Type *getFullyQualifiedTemplateType(const ASTContext &Ctx,
     if (MightHaveChanged) {
       QualType QT = Ctx.getTemplateSpecializationType(
           TST->getTemplateName(), FQArgs,
-          /*CanonicalArgs=*/std::nullopt, TST->desugar());
+          /*CanonicalArgs=*/{}, TST->desugar());
       // getTemplateSpecializationType returns a fully qualified
       // version of the specialization itself, so no need to qualify
       // it.
@@ -172,8 +172,7 @@ static const Type *getFullyQualifiedTemplateType(const ASTContext &Ctx,
         TemplateName TN(TSTDecl->getSpecializedTemplate());
         QualType QT = Ctx.getTemplateSpecializationType(
             TN, FQArgs,
-            /*CanonicalArgs=*/std::nullopt,
-            TSTRecord->getCanonicalTypeInternal());
+            /*CanonicalArgs=*/{}, TSTRecord->getCanonicalTypeInternal());
         // getTemplateSpecializationType returns a fully qualified
         // version of the specialization itself, so no need to qualify
         // it.

clang/lib/Basic/Targets/Xtensa.h

@@ -77,7 +77,7 @@ class LLVM_LIBRARY_VISIBILITY XtensaTargetInfo : public TargetInfo {
   }
 
   ArrayRef<TargetInfo::GCCRegAlias> getGCCRegAliases() const override {
-    return std::nullopt;
+    return {};
   }
 
   bool validateAsmConstraint(const char *&Name,

clang/lib/CodeGen/CGBuiltin.cpp

@@ -2032,7 +2032,7 @@ Value *CodeGenFunction::EmitCheckedArgForAssume(const Expr *E) {
       std::make_pair(ArgValue, CheckOrdinal), CheckHandler,
       {EmitCheckSourceLocation(E->getExprLoc()),
        llvm::ConstantInt::get(Builder.getInt8Ty(), BCK_AssumePassedFalse)},
-      std::nullopt);
+      {});
   return ArgValue;
 }
 

clang/lib/Driver/ToolChains/Clang.cpp

@@ -8953,7 +8953,7 @@ void OffloadBundler::ConstructJob(Compilation &C, const JobAction &JA,
   C.addCommand(std::make_unique<Command>(
       JA, *this, ResponseFileSupport::None(),
       TCArgs.MakeArgString(getToolChain().GetProgramPath(getShortName())),
-      CmdArgs, std::nullopt, Output));
+      CmdArgs, ArrayRef<InputInfo>(), Output));
 }
 
 void OffloadBundler::ConstructJobMultipleOutputs(
@@ -9040,7 +9040,7 @@ void OffloadBundler::ConstructJobMultipleOutputs(
   C.addCommand(std::make_unique<Command>(
       JA, *this, ResponseFileSupport::None(),
       TCArgs.MakeArgString(getToolChain().GetProgramPath(getShortName())),
-      CmdArgs, std::nullopt, Outputs));
+      CmdArgs, ArrayRef<InputInfo>(), Outputs));
 }
 
 void OffloadPackager::ConstructJob(Compilation &C, const JobAction &JA,

clang/lib/Sema/SemaConcept.cpp

@@ -1081,10 +1081,10 @@ static bool CheckFunctionConstraintsWithoutInstantiation(
   // FIXME: Add TemplateArgs through the 'Innermost' parameter once
   // the refactoring of getTemplateInstantiationArgs() relands.
   MultiLevelTemplateArgumentList MLTAL;
-  MLTAL.addOuterTemplateArguments(Template, std::nullopt, /*Final=*/false);
+  MLTAL.addOuterTemplateArguments(Template, {}, /*Final=*/false);
   SemaRef.getTemplateInstantiationArgs(
       MLTAL, /*D=*/FD, FD,
-      /*Final=*/false, /*Innermost=*/std::nullopt, /*RelativeToPrimary=*/true,
+      /*Final=*/false, /*Innermost=*/{}, /*RelativeToPrimary=*/true,
       /*Pattern=*/nullptr, /*ForConstraintInstantiation=*/true);
   MLTAL.replaceInnermostTemplateArguments(Template, TemplateArgs);