[clang] NFC: change more places to use Type::getAsTagDecl and friends (#155313)

This changes a bunch of places which use getAs<TagType>, including
derived types, just to obtain the tag definition.

This is preparation for #155028, offloading all the changes that PR used
to introduce which don't depend on any new helpers.

1 files changed, 69 insertions, 91 deletions

diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 160d735..8a5b9fc 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -5291,14 +5291,9 @@ Decl *Sema::ParsedFreeStandingDeclSpec(Scope *S, AccessSpecifier AS,
     //   UNION_TYPE;   <- where UNION_TYPE is a typedef union.
     if ((Tag && Tag->getDeclName()) ||
         DS.getTypeSpecType() == DeclSpec::TST_typename) {
-      RecordDecl *Record = nullptr;
-      if (Tag)
-        Record = dyn_cast<RecordDecl>(Tag);
-      else if (const RecordType *RT =
-                   DS.getRepAsType().get()->getAsStructureType())
-        Record = RT->getOriginalDecl()->getDefinitionOrSelf();
-      else if (const RecordType *UT = DS.getRepAsType().get()->getAsUnionType())
-        Record = UT->getOriginalDecl()->getDefinitionOrSelf();
+      RecordDecl *Record = dyn_cast_or_null<RecordDecl>(Tag);
+      if (!Record)
+        Record = DS.getRepAsType().get()->getAsRecordDecl();
 
       if (Record && getLangOpts().MicrosoftExt) {
         Diag(DS.getBeginLoc(), diag::ext_ms_anonymous_record)
@@ -14480,11 +14475,8 @@ void Sema::ActOnUninitializedDecl(Decl *RealDecl) {
     //   version of one of these types, or an array of one of the preceding
     //   types and is declared without an initializer.
     if (getLangOpts().CPlusPlus && Var->hasLocalStorage()) {
-      if (const RecordType *Record
-            = Context.getBaseElementType(Type)->getAs<RecordType>()) {
-        CXXRecordDecl *CXXRecord =
-            cast<CXXRecordDecl>(Record->getOriginalDecl())
-                ->getDefinitionOrSelf();
+      if (const auto *CXXRecord =
+              Context.getBaseElementType(Type)->getAsCXXRecordDecl()) {
         // Mark the function (if we're in one) for further checking even if the
         // looser rules of C++11 do not require such checks, so that we can
         // diagnose incompatibilities with C++98.
@@ -14947,8 +14939,8 @@ void Sema::CheckCompleteVariableDeclaration(VarDecl *var) {
 
   // Require the destructor.
   if (!type->isDependentType())
-    if (const RecordType *recordType = baseType->getAs<RecordType>())
-      FinalizeVarWithDestructor(var, recordType);
+    if (auto *RD = baseType->getAsCXXRecordDecl())
+      FinalizeVarWithDestructor(var, RD);
 
   // If this variable must be emitted, add it as an initializer for the current
   // module.
@@ -19119,17 +19111,16 @@ FieldDecl *Sema::CheckFieldDecl(DeclarationName Name, QualType T,
 
   if (!InvalidDecl && getLangOpts().CPlusPlus) {
     if (Record->isUnion()) {
-      if (const RecordType *RT = EltTy->getAs<RecordType>()) {
-        CXXRecordDecl *RDecl = cast<CXXRecordDecl>(RT->getOriginalDecl());
-        if (RDecl->getDefinition()) {
-          // C++ [class.union]p1: An object of a class with a non-trivial
-          // constructor, a non-trivial copy constructor, a non-trivial
-          // destructor, or a non-trivial copy assignment operator
-          // cannot be a member of a union, nor can an array of such
-          // objects.
-          if (CheckNontrivialField(NewFD))
-            NewFD->setInvalidDecl();
-        }
+      if (const auto *RD = EltTy->getAsCXXRecordDecl();
+          RD && (RD->isBeingDefined() || RD->isCompleteDefinition())) {
+
+        // C++ [class.union]p1: An object of a class with a non-trivial
+        // constructor, a non-trivial copy constructor, a non-trivial
+        // destructor, or a non-trivial copy assignment operator
+        // cannot be a member of a union, nor can an array of such
+        // objects.
+        if (CheckNontrivialField(NewFD))
+          NewFD->setInvalidDecl();
       }
 
       // C++ [class.union]p1: If a union contains a member of reference type,
@@ -19185,55 +19176,51 @@ bool Sema::CheckNontrivialField(FieldDecl *FD) {
     return false;
 
   QualType EltTy = Context.getBaseElementType(FD->getType());
-  if (const RecordType *RT = EltTy->getAs<RecordType>()) {
-    CXXRecordDecl *RDecl =
-        cast<CXXRecordDecl>(RT->getOriginalDecl())->getDefinitionOrSelf();
-    if (RDecl->getDefinition()) {
-      // We check for copy constructors before constructors
-      // because otherwise we'll never get complaints about
-      // copy constructors.
-
-      CXXSpecialMemberKind member = CXXSpecialMemberKind::Invalid;
-      // We're required to check for any non-trivial constructors. Since the
-      // implicit default constructor is suppressed if there are any
-      // user-declared constructors, we just need to check that there is a
-      // trivial default constructor and a trivial copy constructor. (We don't
-      // worry about move constructors here, since this is a C++98 check.)
-      if (RDecl->hasNonTrivialCopyConstructor())
-        member = CXXSpecialMemberKind::CopyConstructor;
-      else if (!RDecl->hasTrivialDefaultConstructor())
-        member = CXXSpecialMemberKind::DefaultConstructor;
-      else if (RDecl->hasNonTrivialCopyAssignment())
-        member = CXXSpecialMemberKind::CopyAssignment;
-      else if (RDecl->hasNonTrivialDestructor())
-        member = CXXSpecialMemberKind::Destructor;
-
-      if (member != CXXSpecialMemberKind::Invalid) {
-        if (!getLangOpts().CPlusPlus11 &&
-            getLangOpts().ObjCAutoRefCount && RDecl->hasObjectMember()) {
-          // Objective-C++ ARC: it is an error to have a non-trivial field of
-          // a union. However, system headers in Objective-C programs
-          // occasionally have Objective-C lifetime objects within unions,
-          // and rather than cause the program to fail, we make those
-          // members unavailable.
-          SourceLocation Loc = FD->getLocation();
-          if (getSourceManager().isInSystemHeader(Loc)) {
-            if (!FD->hasAttr<UnavailableAttr>())
-              FD->addAttr(UnavailableAttr::CreateImplicit(Context, "",
-                            UnavailableAttr::IR_ARCFieldWithOwnership, Loc));
-            return false;
-          }
+  if (const auto *RDecl = EltTy->getAsCXXRecordDecl();
+      RDecl && (RDecl->isBeingDefined() || RDecl->isCompleteDefinition())) {
+    // We check for copy constructors before constructors
+    // because otherwise we'll never get complaints about
+    // copy constructors.
+
+    CXXSpecialMemberKind member = CXXSpecialMemberKind::Invalid;
+    // We're required to check for any non-trivial constructors. Since the
+    // implicit default constructor is suppressed if there are any
+    // user-declared constructors, we just need to check that there is a
+    // trivial default constructor and a trivial copy constructor. (We don't
+    // worry about move constructors here, since this is a C++98 check.)
+    if (RDecl->hasNonTrivialCopyConstructor())
+      member = CXXSpecialMemberKind::CopyConstructor;
+    else if (!RDecl->hasTrivialDefaultConstructor())
+      member = CXXSpecialMemberKind::DefaultConstructor;
+    else if (RDecl->hasNonTrivialCopyAssignment())
+      member = CXXSpecialMemberKind::CopyAssignment;
+    else if (RDecl->hasNonTrivialDestructor())
+      member = CXXSpecialMemberKind::Destructor;
+
+    if (member != CXXSpecialMemberKind::Invalid) {
+      if (!getLangOpts().CPlusPlus11 && getLangOpts().ObjCAutoRefCount &&
+          RDecl->hasObjectMember()) {
+        // Objective-C++ ARC: it is an error to have a non-trivial field of
+        // a union. However, system headers in Objective-C programs
+        // occasionally have Objective-C lifetime objects within unions,
+        // and rather than cause the program to fail, we make those
+        // members unavailable.
+        SourceLocation Loc = FD->getLocation();
+        if (getSourceManager().isInSystemHeader(Loc)) {
+          if (!FD->hasAttr<UnavailableAttr>())
+            FD->addAttr(UnavailableAttr::CreateImplicit(
+                Context, "", UnavailableAttr::IR_ARCFieldWithOwnership, Loc));
+          return false;
         }
-
-        Diag(
-            FD->getLocation(),
-            getLangOpts().CPlusPlus11
-                ? diag::warn_cxx98_compat_nontrivial_union_or_anon_struct_member
-                : diag::err_illegal_union_or_anon_struct_member)
-            << FD->getParent()->isUnion() << FD->getDeclName() << member;
-        DiagnoseNontrivial(RDecl, member);
-        return !getLangOpts().CPlusPlus11;
       }
+
+      Diag(FD->getLocation(),
+           getLangOpts().CPlusPlus11
+               ? diag::warn_cxx98_compat_nontrivial_union_or_anon_struct_member
+               : diag::err_illegal_union_or_anon_struct_member)
+          << FD->getParent()->isUnion() << FD->getDeclName() << member;
+      DiagnoseNontrivial(RDecl, member);
+      return !getLangOpts().CPlusPlus11;
     }
   }
 
@@ -19509,11 +19496,9 @@ bool Sema::EntirelyFunctionPointers(const RecordDecl *Record) {
       return PointeeType.getDesugaredType(Context)->isFunctionType();
     }
     // If a member is a struct entirely of function pointers, that counts too.
-    if (const RecordType *RT = FieldType->getAs<RecordType>()) {
-      const RecordDecl *Record = RT->getOriginalDecl()->getDefinitionOrSelf();
-      if (Record->isStruct() && EntirelyFunctionPointers(Record))
-        return true;
-    }
+    if (const auto *Record = FieldType->getAsRecordDecl();
+        Record && Record->isStruct() && EntirelyFunctionPointers(Record))
+      return true;
     return false;
   };
 
@@ -19667,10 +19652,8 @@ void Sema::ActOnFields(Scope *S, SourceLocation RecLoc, Decl *EnclosingDecl,
       FD->setInvalidDecl();
       EnclosingDecl->setInvalidDecl();
       continue;
-    } else if (const RecordType *FDTTy = FDTy->getAs<RecordType>()) {
-      if (Record && FDTTy->getOriginalDecl()
-                        ->getDefinitionOrSelf()
-                        ->hasFlexibleArrayMember()) {
+    } else if (const auto *RD = FDTy->getAsRecordDecl()) {
+      if (Record && RD->hasFlexibleArrayMember()) {
         // A type which contains a flexible array member is considered to be a
         // flexible array member.
         Record->setHasFlexibleArrayMember(true);
@@ -19696,7 +19679,6 @@ void Sema::ActOnFields(Scope *S, SourceLocation RecLoc, Decl *EnclosingDecl,
         // Ivars can not have abstract class types
         FD->setInvalidDecl();
       }
-      const RecordDecl *RD = FDTTy->getOriginalDecl()->getDefinitionOrSelf();
       if (Record && RD->hasObjectMember())
         Record->setHasObjectMember(true);
       if (Record && RD->hasVolatileMember())
@@ -19730,10 +19712,8 @@ void Sema::ActOnFields(Scope *S, SourceLocation RecLoc, Decl *EnclosingDecl,
         Record->setHasObjectMember(true);
       else if (Context.getAsArrayType(FD->getType())) {
         QualType BaseType = Context.getBaseElementType(FD->getType());
-        if (BaseType->isRecordType() && BaseType->castAs<RecordType>()
-                                            ->getOriginalDecl()
-                                            ->getDefinitionOrSelf()
-                                            ->hasObjectMember())
+        if (const auto *RD = BaseType->getAsRecordDecl();
+            RD && RD->hasObjectMember())
           Record->setHasObjectMember(true);
         else if (BaseType->isObjCObjectPointerType() ||
                  BaseType.isObjCGCStrong())
@@ -19765,10 +19745,8 @@ void Sema::ActOnFields(Scope *S, SourceLocation RecLoc, Decl *EnclosingDecl,
           Record->setHasNonTrivialToPrimitiveDestructCUnion(true);
       }
 
-      if (const auto *RT = FT->getAs<RecordType>()) {
-        if (RT->getOriginalDecl()
-                ->getDefinitionOrSelf()
-                ->getArgPassingRestrictions() ==
+      if (const auto *RD = FT->getAsRecordDecl()) {
+        if (RD->getArgPassingRestrictions() ==
             RecordArgPassingKind::CanNeverPassInRegs)
           Record->setArgPassingRestrictions(
               RecordArgPassingKind::CanNeverPassInRegs);