[clang] Migrate away from PointerUnion::dyn_cast (NFC) (#124425)

Note that PointerUnion::dyn_cast has 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>

This patch migrates uses of PointerUnion::dyn_cast to
dyn_cast_if_present (see the definition of PointerUnion::dyn_cast).
Note that we cannot use dyn_cast in any of the migrations in this
patch; placing

  assert(!X.isNull());

just before any of dyn_cast_if_present in this patch triggers some
failure in check-clang.

Author: kazutakahirata

clang/include/clang/AST/APValue.h

@@ -161,8 +161,9 @@ class APValue {
 
     template <class T> T get() const { return cast<T>(Ptr); }
 
-    template <class T>
-    T dyn_cast() const { return Ptr.dyn_cast<T>(); }
+    template <class T> T dyn_cast() const {
+      return dyn_cast_if_present<T>(Ptr);
+    }
 
     void *getOpaqueValue() const;
 

clang/include/clang/AST/ASTContext.h

@@ -769,7 +769,7 @@ class ASTContext : public RefCountedBase<ASTContext> {
   /// pool.
   DeclListNode *AllocateDeclListNode(clang::NamedDecl *ND) {
     if (DeclListNode *Alloc = ListNodeFreeList) {
-      ListNodeFreeList = Alloc->Rest.dyn_cast<DeclListNode*>();
+      ListNodeFreeList = dyn_cast_if_present<DeclListNode *>(Alloc->Rest);
       Alloc->D = ND;
       Alloc->Rest = nullptr;
       return Alloc;

clang/include/clang/AST/Decl.h

@@ -4035,7 +4035,7 @@ class EnumDecl : public TagDecl {
   /// Return the type source info for the underlying integer type,
   /// if no type source info exists, return 0.
   TypeSourceInfo *getIntegerTypeSourceInfo() const {
-    return IntegerType.dyn_cast<TypeSourceInfo*>();
+    return dyn_cast_if_present<TypeSourceInfo *>(IntegerType);
   }
 
   /// Retrieve the source range that covers the underlying type if

clang/include/clang/AST/DeclBase.h

@@ -1391,7 +1391,7 @@ class DeclContextLookupResult {
   const_iterator end() const { return iterator(); }
 
   bool empty() const { return Result.isNull();  }
-  bool isSingleResult() const { return Result.dyn_cast<NamedDecl*>(); }
+  bool isSingleResult() const { return isa_and_present<NamedDecl *>(Result); }
   reference front() const { return *begin(); }
 
   // Find the first declaration of the given type in the list. Note that this

clang/include/clang/AST/DeclTemplate.h

@@ -2009,7 +2009,8 @@ class ClassTemplateSpecializationDecl : public CXXRecordDecl,
   /// Retrieve the template argument list as written in the sources,
   /// if any.
   const ASTTemplateArgumentListInfo *getTemplateArgsAsWritten() const {
-    if (auto *Info = ExplicitInfo.dyn_cast<ExplicitInstantiationInfo *>())
+    if (auto *Info =
+            dyn_cast_if_present<ExplicitInstantiationInfo *>(ExplicitInfo))
       return Info->TemplateArgsAsWritten;
     return cast<const ASTTemplateArgumentListInfo *>(ExplicitInfo);
   }
@@ -2041,7 +2042,8 @@ class ClassTemplateSpecializationDecl : public CXXRecordDecl,
 
   /// Gets the location of the template keyword, if present.
   SourceLocation getTemplateKeywordLoc() const {
-    if (auto *Info = ExplicitInfo.dyn_cast<ExplicitInstantiationInfo *>())
+    if (auto *Info =
+            dyn_cast_if_present<ExplicitInstantiationInfo *>(ExplicitInfo))
       return Info->TemplateKeywordLoc;
     return SourceLocation();
   }
@@ -2786,7 +2788,8 @@ class VarTemplateSpecializationDecl : public VarDecl,
   /// Set the template argument list as written in the sources.
   void
   setTemplateArgsAsWritten(const ASTTemplateArgumentListInfo *ArgsWritten) {
-    if (auto *Info = ExplicitInfo.dyn_cast<ExplicitInstantiationInfo *>())
+    if (auto *Info =
+            dyn_cast_if_present<ExplicitInstantiationInfo *>(ExplicitInfo))
       Info->TemplateArgsAsWritten = ArgsWritten;
     else
       ExplicitInfo = ArgsWritten;

clang/include/clang/AST/Expr.h

@@ -5180,7 +5180,7 @@ class InitListExpr : public Expr {
   /// than there are initializers in the list, specifies an expression to be
   /// used for value initialization of the rest of the elements.
   Expr *getArrayFiller() {
-    return ArrayFillerOrUnionFieldInit.dyn_cast<Expr *>();
+    return dyn_cast_if_present<Expr *>(ArrayFillerOrUnionFieldInit);
   }
   const Expr *getArrayFiller() const {
     return const_cast<InitListExpr *>(this)->getArrayFiller();
@@ -5205,7 +5205,7 @@ class InitListExpr : public Expr {
   /// union. However, a designated initializer can specify the
   /// initialization of a different field within the union.
   FieldDecl *getInitializedFieldInUnion() {
-    return ArrayFillerOrUnionFieldInit.dyn_cast<FieldDecl *>();
+    return dyn_cast_if_present<FieldDecl *>(ArrayFillerOrUnionFieldInit);
   }
   const FieldDecl *getInitializedFieldInUnion() const {
     return const_cast<InitListExpr *>(this)->getInitializedFieldInUnion();

clang/include/clang/AST/ExprCXX.h

@@ -5026,19 +5026,19 @@ class CXXParenListInitExpr final
   void setArrayFiller(Expr *E) { ArrayFillerOrUnionFieldInit = E; }
 
   Expr *getArrayFiller() {
-    return ArrayFillerOrUnionFieldInit.dyn_cast<Expr *>();
+    return dyn_cast_if_present<Expr *>(ArrayFillerOrUnionFieldInit);
   }
 
   const Expr *getArrayFiller() const {
-    return ArrayFillerOrUnionFieldInit.dyn_cast<Expr *>();
+    return dyn_cast_if_present<Expr *>(ArrayFillerOrUnionFieldInit);
   }
 
   void setInitializedFieldInUnion(FieldDecl *FD) {
     ArrayFillerOrUnionFieldInit = FD;
   }
 
   FieldDecl *getInitializedFieldInUnion() {
-    return ArrayFillerOrUnionFieldInit.dyn_cast<FieldDecl *>();
+    return dyn_cast_if_present<FieldDecl *>(ArrayFillerOrUnionFieldInit);
   }
 
   const FieldDecl *getInitializedFieldInUnion() const {

clang/include/clang/Basic/IdentifierTable.h

@@ -1008,7 +1008,7 @@ class Selector {
   }
 
   const IdentifierInfo *getAsIdentifierInfo() const {
-    return InfoPtr.getPointer().dyn_cast<const IdentifierInfo *>();
+    return dyn_cast_if_present<const IdentifierInfo *>(InfoPtr.getPointer());
   }
 
   MultiKeywordSelector *getMultiKeywordSelector() const {

clang/include/clang/Lex/Preprocessor.h

@@ -856,7 +856,7 @@ class Preprocessor {
           !PP.CurSubmoduleState->VisibleModules.getGeneration())
         return nullptr;
 
-      auto *Info = State.dyn_cast<ModuleMacroInfo*>();
+      auto *Info = dyn_cast_if_present<ModuleMacroInfo *>(State);
       if (!Info) {
         Info = new (PP.getPreprocessorAllocator())
             ModuleMacroInfo(cast<MacroDirective *>(State));
@@ -885,18 +885,18 @@ class Preprocessor {
     }
 
     ~MacroState() {
-      if (auto *Info = State.dyn_cast<ModuleMacroInfo*>())
+      if (auto *Info = dyn_cast_if_present<ModuleMacroInfo *>(State))
         Info->~ModuleMacroInfo();
     }
 
     MacroDirective *getLatest() const {
-      if (auto *Info = State.dyn_cast<ModuleMacroInfo*>())
+      if (auto *Info = dyn_cast_if_present<ModuleMacroInfo *>(State))
         return Info->MD;
       return cast<MacroDirective *>(State);
     }
 
     void setLatest(MacroDirective *MD) {
-      if (auto *Info = State.dyn_cast<ModuleMacroInfo*>())
+      if (auto *Info = dyn_cast_if_present<ModuleMacroInfo *>(State))
         Info->MD = MD;
       else
         State = MD;
@@ -940,7 +940,7 @@ class Preprocessor {
 
     void setOverriddenMacros(Preprocessor &PP,
                              ArrayRef<ModuleMacro *> Overrides) {
-      auto *Info = State.dyn_cast<ModuleMacroInfo*>();
+      auto *Info = dyn_cast_if_present<ModuleMacroInfo *>(State);
       if (!Info) {
         if (Overrides.empty())
           return;

clang/lib/APINotes/APINotesManager.cpp

@@ -56,7 +56,7 @@ APINotesManager::APINotesManager(SourceManager &SM, const LangOptions &LangOpts)
 APINotesManager::~APINotesManager() {
   // Free the API notes readers.
   for (const auto &Entry : Readers) {
-    if (auto Reader = Entry.second.dyn_cast<APINotesReader *>())
+    if (auto Reader = dyn_cast_if_present<APINotesReader *>(Entry.second))
       delete Reader;
   }
 
@@ -381,7 +381,7 @@ APINotesManager::findAPINotes(SourceLocation Loc) {
       }
 
       // We have the answer.
-      if (auto Reader = Known->second.dyn_cast<APINotesReader *>())
+      if (auto Reader = dyn_cast_if_present<APINotesReader *>(Known->second))
         Results.push_back(Reader);
       break;
     }