[Serialization] Migrate away from PointerUnion::{is,get} (NFC)

Note that PointerUnion::{is,get} have been soft deprecated in
PointerUnion.h:

  // FIXME: Replace the uses of is(), get() and dyn_cast() with
  //        isa<T>, cast<T> and the llvm::dyn_cast<T>

I'm not touching PointerUnion::dyn_cast for now because it's a bit
complicated; we could blindly migrate it to dyn_cast_if_present, but
we should probably use dyn_cast when the operand is known to be
non-null.

Author: kazutakahirata

clang/lib/Serialization/ASTReaderDecl.cpp

@@ -4598,7 +4598,7 @@ void ASTDeclReader::UpdateDecl(Decl *D) {
                     .dyn_cast<FunctionTemplateSpecializationInfo *>())
           FTSInfo->setPointOfInstantiation(POI);
         else
-          FD->TemplateOrSpecialization.get<MemberSpecializationInfo *>()
+          cast<MemberSpecializationInfo *>(FD->TemplateOrSpecialization)
               ->setPointOfInstantiation(POI);
       }
       break;
@@ -4697,8 +4697,8 @@ void ASTDeclReader::UpdateDecl(Decl *D) {
 
           // FIXME: If we already have a partial specialization set,
           // check that it matches.
-          if (!Spec->getSpecializedTemplateOrPartial()
-                   .is<ClassTemplatePartialSpecializationDecl *>())
+          if (!isa<ClassTemplatePartialSpecializationDecl *>(
+                  Spec->getSpecializedTemplateOrPartial()))
             Spec->setInstantiationOf(PartialSpec, TemplArgList);
         }
       }

clang/lib/Serialization/ASTReaderStmt.cpp

@@ -911,9 +911,9 @@ void ASTStmtReader::VisitRequiresExpr(RequiresExpr *E) {
                   std::move(*Req), Status, SubstitutedConstraintExpr);
         else
           R = new (Record.getContext()) concepts::ExprRequirement(
-                  E.get<concepts::Requirement::SubstitutionDiagnostic *>(),
-                  RK == concepts::Requirement::RK_Simple, NoexceptLoc,
-                  std::move(*Req));
+              cast<concepts::Requirement::SubstitutionDiagnostic *>(E),
+              RK == concepts::Requirement::RK_Simple, NoexceptLoc,
+              std::move(*Req));
       } break;
       case concepts::Requirement::RK_Nested: {
         ASTContext &C = Record.getContext();

clang/lib/Serialization/ASTWriter.cpp

@@ -5111,7 +5111,7 @@ ASTWriter::WriteAST(llvm::PointerUnion<Sema *, Preprocessor *> Subject,
 
   Sema *SemaPtr = Subject.dyn_cast<Sema *>();
   Preprocessor &PPRef =
-      SemaPtr ? SemaPtr->getPreprocessor() : *Subject.get<Preprocessor *>();
+      SemaPtr ? SemaPtr->getPreprocessor() : *cast<Preprocessor *>(Subject);
 
   ASTHasCompilerErrors = PPRef.getDiagnostics().hasUncompilableErrorOccurred();
 

clang/lib/Serialization/ASTWriterDecl.cpp

@@ -1694,7 +1694,7 @@ void ASTDeclWriter::VisitFriendDecl(FriendDecl *D) {
   // so as to simplify memory allocation during deserialization.
   Record.push_back(D->NumTPLists);
   VisitDecl(D);
-  bool hasFriendDecl = D->Friend.is<NamedDecl*>();
+  bool hasFriendDecl = isa<NamedDecl *>(D->Friend);
   Record.push_back(hasFriendDecl);
   if (hasFriendDecl)
     Record.AddDeclRef(D->getFriendDecl());
@@ -1795,7 +1795,7 @@ void ASTDeclWriter::VisitClassTemplateSpecializationDecl(
   if (Decl *InstFromD = InstFrom.dyn_cast<ClassTemplateDecl *>()) {
     Record.AddDeclRef(InstFromD);
   } else {
-    Record.AddDeclRef(InstFrom.get<ClassTemplatePartialSpecializationDecl *>());
+    Record.AddDeclRef(cast<ClassTemplatePartialSpecializationDecl *>(InstFrom));
     Record.AddTemplateArgumentList(&D->getTemplateInstantiationArgs());
   }
 
@@ -1873,7 +1873,7 @@ void ASTDeclWriter::VisitVarTemplateSpecializationDecl(
   if (Decl *InstFromD = InstFrom.dyn_cast<VarTemplateDecl *>()) {
     Record.AddDeclRef(InstFromD);
   } else {
-    Record.AddDeclRef(InstFrom.get<VarTemplatePartialSpecializationDecl *>());
+    Record.AddDeclRef(cast<VarTemplatePartialSpecializationDecl *>(InstFrom));
     Record.AddTemplateArgumentList(&D->getTemplateInstantiationArgs());
   }
 

clang/lib/Serialization/ASTWriterStmt.cpp

@@ -480,7 +480,7 @@ addConstraintSatisfaction(ASTRecordWriter &Record,
       if (E)
         Record.AddStmt(E);
       else {
-        auto *Diag = DetailRecord.get<std::pair<SourceLocation, StringRef> *>();
+        auto *Diag = cast<std::pair<SourceLocation, StringRef> *>(DetailRecord);
         Record.AddSourceLocation(Diag->first);
         Record.AddString(Diag->second);
       }
@@ -532,10 +532,11 @@ void ASTStmtWriter::VisitRequiresExpr(RequiresExpr *E) {
       Record.push_back(ExprReq->getKind());
       Record.push_back(ExprReq->Status);
       if (ExprReq->isExprSubstitutionFailure()) {
-        addSubstitutionDiagnostic(Record,
-         ExprReq->Value.get<concepts::Requirement::SubstitutionDiagnostic *>());
+        addSubstitutionDiagnostic(
+            Record, cast<concepts::Requirement::SubstitutionDiagnostic *>(
+                        ExprReq->Value));
       } else
-        Record.AddStmt(ExprReq->Value.get<Expr *>());
+        Record.AddStmt(cast<Expr *>(ExprReq->Value));
       if (ExprReq->getKind() == concepts::Requirement::RK_Compound) {
         Record.AddSourceLocation(ExprReq->NoexceptLoc);
         const auto &RetReq = ExprReq->getReturnTypeRequirement();
@@ -1166,7 +1167,7 @@ void ASTStmtWriter::VisitInitListExpr(InitListExpr *E) {
   Record.AddStmt(E->getSyntacticForm());
   Record.AddSourceLocation(E->getLBraceLoc());
   Record.AddSourceLocation(E->getRBraceLoc());
-  bool isArrayFiller = E->ArrayFillerOrUnionFieldInit.is<Expr*>();
+  bool isArrayFiller = isa<Expr *>(E->ArrayFillerOrUnionFieldInit);
   Record.push_back(isArrayFiller);
   if (isArrayFiller)
     Record.AddStmt(E->getArrayFiller());