Move `GetTypeName` implementation into `ClassData`.

For LITE messages we append the type name to the data, avoiding an
indirection and a relocation.
For descriptor messages we have a single secondary vtable. This reduces the per-message cost of all the descriptor methods to a single pointer.

PiperOrigin-RevId: 574877986

src/google/protobuf/compiler/cpp/message.cc

@@ -1603,26 +1603,20 @@ void MessageGenerator::GenerateClassDefinition(io::Printer* p) {
       break;
   }
 
+  if (!HasSimpleBaseClass(descriptor_, options_)) {
+    p->Emit(R"cc(
+      const ::$proto_ns$::MessageLite::ClassData* GetClassData() const final;
+    )cc");
+  }
+
   format(
       "public:\n"
       "\n");
 
   if (HasDescriptorMethods(descriptor_->file(), options_)) {
-    if (HasGeneratedMethods(descriptor_->file(), options_) &&
-        !HasSimpleBaseClass(descriptor_, options_)) {
-      format(
-          "static const ClassData _class_data_;\n"
-          "const ::$proto_ns$::Message::ClassData*"
-          "GetClassData() const final;\n"
-          "\n");
-    }
     format(
         "::$proto_ns$::Metadata GetMetadata() const final;\n"
         "\n");
-  } else {
-    format(
-        "std::string GetTypeName() const final;\n"
-        "\n");
   }
 
   if (ShouldSplit(descriptor_, options_)) {
@@ -2049,6 +2043,8 @@ void MessageGenerator::GenerateClassMethods(io::Printer* p) {
     format("\n");
   }
 
+  GenerateClassData(p);
+
   if (HasGeneratedMethods(descriptor_->file(), options_)) {
     GenerateClear(p);
     format("\n");
@@ -2124,12 +2120,6 @@ void MessageGenerator::GenerateClassMethods(io::Printer* p) {
           "}\n",
           index_in_file_messages_);
     }
-  } else {
-    format(
-        "std::string $classname$::GetTypeName() const {\n"
-        "  return \"$full_name$\";\n"
-        "}\n"
-        "\n");
   }
 
   if (HasTracker(descriptor_, options_)) {
@@ -3587,21 +3577,27 @@ void MessageGenerator::GenerateSwap(io::Printer* p) {
   format("}\n");
 }
 
-void MessageGenerator::GenerateMergeFrom(io::Printer* p) {
+void MessageGenerator::GenerateClassData(io::Printer* p) {
   Formatter format(p);
   if (HasSimpleBaseClass(descriptor_, options_)) return;
-  if (HasDescriptorMethods(descriptor_->file(), options_)) {
-    // We don't override the generalized MergeFrom (aka that which
-    // takes in the Message base class as a parameter); instead we just
-    // let the base Message::MergeFrom take care of it.  The base MergeFrom
-    // knows how to quickly confirm the types exactly match, and if so, will
-    // use GetClassData() to retrieve the address of MergeImpl, which calls
-    // the fast MergeFrom overload.  Most callers avoid all this by passing
-    // a "from" message that is the same type as the message being merged
-    // into, rather than a generic Message.
 
+  const auto class_data_members = [&] {
     p->Emit(
         {
+            {"merge_impl",
+             [&] {
+               // TODO: This check is not needed once we migrate
+               // CheckTypeAndMergeFrom to ClassData fully.
+               if (HasDescriptorMethods(descriptor_->file(), options_)) {
+                 p->Emit(R"cc(
+                   $classname$::MergeImpl,
+                 )cc");
+               } else {
+                 p->Emit(R"cc(
+                   nullptr,  // MergeImpl
+                 )cc");
+               }
+             }},
             {"on_demand_register_arena_dtor",
              [&] {
                if (NeedsArenaDestructor() == ArenaDtorNeeds::kOnDemand) {
@@ -3614,17 +3610,67 @@ void MessageGenerator::GenerateMergeFrom(io::Printer* p) {
                  )cc");
                }
              }},
+            {"descriptor_methods",
+             [&] {
+               if (HasDescriptorMethods(descriptor_->file(), options_)) {
+                 p->Emit(R"cc(
+                   &::$proto_ns$::Message::kDescriptorMethods,
+                 )cc");
+               } else {
+                 p->Emit(R"cc(
+                   nullptr,  // DescriptorMethods
+                 )cc");
+               }
+             }},
         },
         R"cc(
-          const ::$proto_ns$::Message::ClassData $classname$::_class_data_ = {
+          $merge_impl$, $on_demand_register_arena_dtor$, $descriptor_methods$,
-              $classname$::MergeImpl,
+        )cc");
-              $on_demand_register_arena_dtor$,
+  };
-          };
+
-          const ::$proto_ns$::Message::ClassData* $classname$::GetClassData() const {
+  if (HasDescriptorMethods(descriptor_->file(), options_)) {
-            return &_class_data_;
+    p->Emit(
+        {{"class_data_members", class_data_members}},
+        R"cc(
+          const ::$proto_ns$::MessageLite::ClassData*
+          $classname$::GetClassData() const {
+            PROTOBUF_CONSTINIT static const ::$proto_ns$::MessageLite::ClassData
+                data = {
+                    $class_data_members$,
+                };
+            return &data;
           }
         )cc");
   } else {
+    p->Emit(
+        {
+            {"class_data_members", class_data_members},
+            {"type_size", descriptor_->full_name().size() + 1},
+        },
+        R"cc(
+          const ::$proto_ns$::MessageLite::ClassData*
+          $classname$::GetClassData() const {
+            struct ClassData_ {
+              ::$proto_ns$::MessageLite::ClassData header;
+              char type_name[$type_size$];
+            };
+            PROTOBUF_CONSTINIT static const ClassData_ data = {
+                {
+                    $class_data_members$,
+                },
+                "$full_name$",
+            };
+
+            return &data.header;
+          }
+        )cc");
+  }
+}
+
+void MessageGenerator::GenerateMergeFrom(io::Printer* p) {
+  Formatter format(p);
+
+  if (!HasDescriptorMethods(descriptor_->file(), options_)) {
     // Generate CheckTypeAndMergeFrom().
     format(
         "void $classname$::CheckTypeAndMergeFrom(\n"

src/google/protobuf/compiler/cpp/message.h

@@ -117,6 +117,7 @@ class MessageGenerator {
   void GenerateSerializeWithCachedSizesBody(io::Printer* p);
   void GenerateSerializeWithCachedSizesBodyShuffled(io::Printer* p);
   void GenerateByteSize(io::Printer* p);
+  void GenerateClassData(io::Printer* p);
   void GenerateMergeFrom(io::Printer* p);
   void GenerateClassSpecificMergeImpl(io::Printer* p);
   void GenerateCopyFrom(io::Printer* p);

src/google/protobuf/compiler/java/java_features.pb.cc

@@ -196,6 +196,16 @@ inline void JavaFeatures::SharedDtor() {
   _impl_.~Impl_();
 }
 
+const ::google::protobuf::MessageLite::ClassData*
+JavaFeatures::GetClassData() const {
+  PROTOBUF_CONSTINIT static const ::google::protobuf::MessageLite::ClassData
+      data = {
+          JavaFeatures::MergeImpl,
+           nullptr,  // OnDemandRegisterArenaDtor
+           &::google::protobuf::Message::kDescriptorMethods,
+      };
+  return &data;
+}
 PROTOBUF_NOINLINE void JavaFeatures::Clear() {
 // @@protoc_insertion_point(message_clear_start:pb.JavaFeatures)
   PROTOBUF_TSAN_WRITE(&_impl_._tsan_detect_race);
@@ -312,13 +322,6 @@ const ::_pbi::TcParseTable<1, 2, 1, 0, 2> JavaFeatures::_table_ = {
   return MaybeComputeUnknownFieldsSize(total_size, &_impl_._cached_size_);
 }
 
-const ::google::protobuf::Message::ClassData JavaFeatures::_class_data_ = {
-    JavaFeatures::MergeImpl,
-    nullptr,  // OnDemandRegisterArenaDtor
-};
-const ::google::protobuf::Message::ClassData* JavaFeatures::GetClassData() const {
-  return &_class_data_;
-}
 
 void JavaFeatures::MergeImpl(::google::protobuf::Message& to_msg, const ::google::protobuf::Message& from_msg) {
   auto* const _this = static_cast<JavaFeatures*>(&to_msg);

src/google/protobuf/compiler/java/java_features.pb.h

@@ -224,11 +224,9 @@ class PROTOC_EXPORT JavaFeatures final :
   protected:
   explicit JavaFeatures(::google::protobuf::Arena* arena);
   JavaFeatures(::google::protobuf::Arena* arena, const JavaFeatures& from);
+  const ::google::protobuf::MessageLite::ClassData* GetClassData() const final;
   public:
 
-  static const ClassData _class_data_;
-  const ::google::protobuf::Message::ClassData*GetClassData() const final;
-
   ::google::protobuf::Metadata GetMetadata() const final;
 
   // nested types ----------------------------------------------------

src/google/protobuf/compiler/plugin.pb.cc

@@ -381,6 +381,16 @@ inline void Version::SharedDtor() {
   _impl_.~Impl_();
 }
 
+const ::google::protobuf::MessageLite::ClassData*
+Version::GetClassData() const {
+  PROTOBUF_CONSTINIT static const ::google::protobuf::MessageLite::ClassData
+      data = {
+          Version::MergeImpl,
+           nullptr,  // OnDemandRegisterArenaDtor
+           &::google::protobuf::Message::kDescriptorMethods,
+      };
+  return &data;
+}
 PROTOBUF_NOINLINE void Version::Clear() {
 // @@protoc_insertion_point(message_clear_start:google.protobuf.compiler.Version)
   PROTOBUF_TSAN_WRITE(&_impl_._tsan_detect_race);
@@ -543,13 +553,6 @@ const ::_pbi::TcParseTable<2, 4, 0, 47, 2> Version::_table_ = {
   return MaybeComputeUnknownFieldsSize(total_size, &_impl_._cached_size_);
 }
 
-const ::google::protobuf::Message::ClassData Version::_class_data_ = {
-    Version::MergeImpl,
-    nullptr,  // OnDemandRegisterArenaDtor
-};
-const ::google::protobuf::Message::ClassData* Version::GetClassData() const {
-  return &_class_data_;
-}
 
 void Version::MergeImpl(::google::protobuf::Message& to_msg, const ::google::protobuf::Message& from_msg) {
   auto* const _this = static_cast<Version*>(&to_msg);
@@ -695,6 +698,16 @@ inline void CodeGeneratorRequest::SharedDtor() {
   _impl_.~Impl_();
 }
 
+const ::google::protobuf::MessageLite::ClassData*
+CodeGeneratorRequest::GetClassData() const {
+  PROTOBUF_CONSTINIT static const ::google::protobuf::MessageLite::ClassData
+      data = {
+          CodeGeneratorRequest::MergeImpl,
+           nullptr,  // OnDemandRegisterArenaDtor
+           &::google::protobuf::Message::kDescriptorMethods,
+      };
+  return &data;
+}
 PROTOBUF_NOINLINE void CodeGeneratorRequest::Clear() {
 // @@protoc_insertion_point(message_clear_start:google.protobuf.compiler.CodeGeneratorRequest)
   PROTOBUF_TSAN_WRITE(&_impl_._tsan_detect_race);
@@ -887,13 +900,6 @@ const ::_pbi::TcParseTable<3, 5, 3, 79, 2> CodeGeneratorRequest::_table_ = {
   return MaybeComputeUnknownFieldsSize(total_size, &_impl_._cached_size_);
 }
 
-const ::google::protobuf::Message::ClassData CodeGeneratorRequest::_class_data_ = {
-    CodeGeneratorRequest::MergeImpl,
-    nullptr,  // OnDemandRegisterArenaDtor
-};
-const ::google::protobuf::Message::ClassData* CodeGeneratorRequest::GetClassData() const {
-  return &_class_data_;
-}
 
 void CodeGeneratorRequest::MergeImpl(::google::protobuf::Message& to_msg, const ::google::protobuf::Message& from_msg) {
   auto* const _this = static_cast<CodeGeneratorRequest*>(&to_msg);
@@ -1043,6 +1049,16 @@ inline void CodeGeneratorResponse_File::SharedDtor() {
   _impl_.~Impl_();
 }
 
+const ::google::protobuf::MessageLite::ClassData*
+CodeGeneratorResponse_File::GetClassData() const {
+  PROTOBUF_CONSTINIT static const ::google::protobuf::MessageLite::ClassData
+      data = {
+          CodeGeneratorResponse_File::MergeImpl,
+           nullptr,  // OnDemandRegisterArenaDtor
+           &::google::protobuf::Message::kDescriptorMethods,
+      };
+  return &data;
+}
 PROTOBUF_NOINLINE void CodeGeneratorResponse_File::Clear() {
 // @@protoc_insertion_point(message_clear_start:google.protobuf.compiler.CodeGeneratorResponse.File)
   PROTOBUF_TSAN_WRITE(&_impl_._tsan_detect_race);
@@ -1216,13 +1232,6 @@ const ::_pbi::TcParseTable<2, 4, 1, 86, 2> CodeGeneratorResponse_File::_table_ =
   return MaybeComputeUnknownFieldsSize(total_size, &_impl_._cached_size_);
 }
 
-const ::google::protobuf::Message::ClassData CodeGeneratorResponse_File::_class_data_ = {
-    CodeGeneratorResponse_File::MergeImpl,
-    nullptr,  // OnDemandRegisterArenaDtor
-};
-const ::google::protobuf::Message::ClassData* CodeGeneratorResponse_File::GetClassData() const {
-  return &_class_data_;
-}
 
 void CodeGeneratorResponse_File::MergeImpl(::google::protobuf::Message& to_msg, const ::google::protobuf::Message& from_msg) {
   auto* const _this = static_cast<CodeGeneratorResponse_File*>(&to_msg);
@@ -1345,6 +1354,16 @@ inline void CodeGeneratorResponse::SharedDtor() {
   _impl_.~Impl_();
 }
 
+const ::google::protobuf::MessageLite::ClassData*
+CodeGeneratorResponse::GetClassData() const {
+  PROTOBUF_CONSTINIT static const ::google::protobuf::MessageLite::ClassData
+      data = {
+          CodeGeneratorResponse::MergeImpl,
+           nullptr,  // OnDemandRegisterArenaDtor
+           &::google::protobuf::Message::kDescriptorMethods,
+      };
+  return &data;
+}
 PROTOBUF_NOINLINE void CodeGeneratorResponse::Clear() {
 // @@protoc_insertion_point(message_clear_start:google.protobuf.compiler.CodeGeneratorResponse)
   PROTOBUF_TSAN_WRITE(&_impl_._tsan_detect_race);
@@ -1487,13 +1506,6 @@ const ::_pbi::TcParseTable<2, 3, 1, 60, 2> CodeGeneratorResponse::_table_ = {
   return MaybeComputeUnknownFieldsSize(total_size, &_impl_._cached_size_);
 }
 
-const ::google::protobuf::Message::ClassData CodeGeneratorResponse::_class_data_ = {
-    CodeGeneratorResponse::MergeImpl,
-    nullptr,  // OnDemandRegisterArenaDtor
-};
-const ::google::protobuf::Message::ClassData* CodeGeneratorResponse::GetClassData() const {
-  return &_class_data_;
-}
 
 void CodeGeneratorResponse::MergeImpl(::google::protobuf::Message& to_msg, const ::google::protobuf::Message& from_msg) {
   auto* const _this = static_cast<CodeGeneratorResponse*>(&to_msg);

src/google/protobuf/compiler/plugin.pb.h

@@ -241,11 +241,9 @@ class PROTOC_EXPORT Version final :
   protected:
   explicit Version(::google::protobuf::Arena* arena);
   Version(::google::protobuf::Arena* arena, const Version& from);
+  const ::google::protobuf::MessageLite::ClassData* GetClassData() const final;
   public:
 
-  static const ClassData _class_data_;
-  const ::google::protobuf::Message::ClassData*GetClassData() const final;
-
   ::google::protobuf::Metadata GetMetadata() const final;
 
   // nested types ----------------------------------------------------
@@ -463,11 +461,9 @@ class PROTOC_EXPORT CodeGeneratorResponse_File final :
   protected:
   explicit CodeGeneratorResponse_File(::google::protobuf::Arena* arena);
   CodeGeneratorResponse_File(::google::protobuf::Arena* arena, const CodeGeneratorResponse_File& from);
+  const ::google::protobuf::MessageLite::ClassData* GetClassData() const final;
   public:
 
-  static const ClassData _class_data_;
-  const ::google::protobuf::Message::ClassData*GetClassData() const final;
-
   ::google::protobuf::Metadata GetMetadata() const final;
 
   // nested types ----------------------------------------------------
@@ -701,11 +697,9 @@ class PROTOC_EXPORT CodeGeneratorResponse final :
   protected:
   explicit CodeGeneratorResponse(::google::protobuf::Arena* arena);
   CodeGeneratorResponse(::google::protobuf::Arena* arena, const CodeGeneratorResponse& from);
+  const ::google::protobuf::MessageLite::ClassData* GetClassData() const final;
   public:
 
-  static const ClassData _class_data_;
-  const ::google::protobuf::Message::ClassData*GetClassData() const final;
-
   ::google::protobuf::Metadata GetMetadata() const final;
 
   // nested types ----------------------------------------------------
@@ -940,11 +934,9 @@ class PROTOC_EXPORT CodeGeneratorRequest final :
   protected:
   explicit CodeGeneratorRequest(::google::protobuf::Arena* arena);
   CodeGeneratorRequest(::google::protobuf::Arena* arena, const CodeGeneratorRequest& from);
+  const ::google::protobuf::MessageLite::ClassData* GetClassData() const final;
   public:
 
-  static const ClassData _class_data_;
-  const ::google::protobuf::Message::ClassData*GetClassData() const final;
-
   ::google::protobuf::Metadata GetMetadata() const final;
 
   // nested types ----------------------------------------------------

src/google/protobuf/cpp_features.pb.cc

@@ -157,6 +157,16 @@ inline void CppFeatures::SharedDtor() {
   _impl_.~Impl_();
 }
 
+const ::google::protobuf::MessageLite::ClassData*
+CppFeatures::GetClassData() const {
+  PROTOBUF_CONSTINIT static const ::google::protobuf::MessageLite::ClassData
+      data = {
+          CppFeatures::MergeImpl,
+           nullptr,  // OnDemandRegisterArenaDtor
+           &::google::protobuf::Message::kDescriptorMethods,
+      };
+  return &data;
+}
 PROTOBUF_NOINLINE void CppFeatures::Clear() {
 // @@protoc_insertion_point(message_clear_start:pb.CppFeatures)
   PROTOBUF_TSAN_WRITE(&_impl_._tsan_detect_race);
@@ -247,13 +257,6 @@ const ::_pbi::TcParseTable<0, 1, 0, 0, 2> CppFeatures::_table_ = {
   return MaybeComputeUnknownFieldsSize(total_size, &_impl_._cached_size_);
 }
 
-const ::google::protobuf::Message::ClassData CppFeatures::_class_data_ = {
-    CppFeatures::MergeImpl,
-    nullptr,  // OnDemandRegisterArenaDtor
-};
-const ::google::protobuf::Message::ClassData* CppFeatures::GetClassData() const {
-  return &_class_data_;
-}
 
 void CppFeatures::MergeImpl(::google::protobuf::Message& to_msg, const ::google::protobuf::Message& from_msg) {
   auto* const _this = static_cast<CppFeatures*>(&to_msg);

src/google/protobuf/cpp_features.pb.h

@@ -193,11 +193,9 @@ class PROTOBUF_EXPORT CppFeatures final :
   protected:
   explicit CppFeatures(::google::protobuf::Arena* arena);
   CppFeatures(::google::protobuf::Arena* arena, const CppFeatures& from);
+  const ::google::protobuf::MessageLite::ClassData* GetClassData() const final;
   public:
 
-  static const ClassData _class_data_;
-  const ::google::protobuf::Message::ClassData*GetClassData() const final;
-
   ::google::protobuf::Metadata GetMetadata() const final;
 
   // nested types ----------------------------------------------------

src/google/protobuf/descriptor.pb.cc

@@ -2396,6 +2396,16 @@ inline void FileDescriptorSet::SharedDtor() {
   _impl_.~Impl_();
 }
 
+const ::google::protobuf::MessageLite::ClassData*
+FileDescriptorSet::GetClassData() const {
+  PROTOBUF_CONSTINIT static const ::google::protobuf::MessageLite::ClassData
+      data = {
+          FileDescriptorSet::MergeImpl,
+           nullptr,  // OnDemandRegisterArenaDtor
+           &::google::protobuf::Message::kDescriptorMethods,
+      };
+  return &data;
+}
 PROTOBUF_NOINLINE void FileDescriptorSet::Clear() {
 // @@protoc_insertion_point(message_clear_start:google.protobuf.FileDescriptorSet)
   PROTOBUF_TSAN_WRITE(&_impl_._tsan_detect_race);
@@ -2484,13 +2494,6 @@ constexpr ::_pbi::TcParseTable<0, 1, 1, 0, 2> FileDescriptorSet::_table_ = {
   return MaybeComputeUnknownFieldsSize(total_size, &_impl_._cached_size_);
 }
 
-const ::google::protobuf::Message::ClassData FileDescriptorSet::_class_data_ = {
-    FileDescriptorSet::MergeImpl,
-    nullptr,  // OnDemandRegisterArenaDtor
-};
-const ::google::protobuf::Message::ClassData* FileDescriptorSet::GetClassData() const {
-  return &_class_data_;
-}
 
 void FileDescriptorSet::MergeImpl(::google::protobuf::Message& to_msg, const ::google::protobuf::Message& from_msg) {
   auto* const _this = static_cast<FileDescriptorSet*>(&to_msg);
@@ -2647,6 +2650,16 @@ inline void FileDescriptorProto::SharedDtor() {
   _impl_.~Impl_();
 }
 
+const ::google::protobuf::MessageLite::ClassData*
+FileDescriptorProto::GetClassData() const {
+  PROTOBUF_CONSTINIT static const ::google::protobuf::MessageLite::ClassData
+      data = {
+          FileDescriptorProto::MergeImpl,
+           nullptr,  // OnDemandRegisterArenaDtor
+           &::google::protobuf::Message::kDescriptorMethods,
+      };
+  return &data;
+}
 PROTOBUF_NOINLINE void FileDescriptorProto::Clear() {
 // @@protoc_insertion_point(message_clear_start:google.protobuf.FileDescriptorProto)
   PROTOBUF_TSAN_WRITE(&_impl_._tsan_detect_race);
@@ -3025,13 +3038,6 @@ constexpr ::_pbi::TcParseTable<4, 13, 7, 79, 2> FileDescriptorProto::_table_ = {
   return MaybeComputeUnknownFieldsSize(total_size, &_impl_._cached_size_);
 }
 
-const ::google::protobuf::Message::ClassData FileDescriptorProto::_class_data_ = {
-    FileDescriptorProto::MergeImpl,
-    nullptr,  // OnDemandRegisterArenaDtor
-};
-const ::google::protobuf::Message::ClassData* FileDescriptorProto::GetClassData() const {
-  return &_class_data_;
-}
 
 void FileDescriptorProto::MergeImpl(::google::protobuf::Message& to_msg, const ::google::protobuf::Message& from_msg) {
   auto* const _this = static_cast<FileDescriptorProto*>(&to_msg);
@@ -3214,6 +3220,16 @@ inline void DescriptorProto_ExtensionRange::SharedDtor() {
   _impl_.~Impl_();
 }
 
+const ::google::protobuf::MessageLite::ClassData*
+DescriptorProto_ExtensionRange::GetClassData() const {
+  PROTOBUF_CONSTINIT static const ::google::protobuf::MessageLite::ClassData
+      data = {
+          DescriptorProto_ExtensionRange::MergeImpl,
+           nullptr,  // OnDemandRegisterArenaDtor
+           &::google::protobuf::Message::kDescriptorMethods,
+      };
+  return &data;
+}
 PROTOBUF_NOINLINE void DescriptorProto_ExtensionRange::Clear() {
 // @@protoc_insertion_point(message_clear_start:google.protobuf.DescriptorProto.ExtensionRange)
   PROTOBUF_TSAN_WRITE(&_impl_._tsan_detect_race);
@@ -3354,13 +3370,6 @@ constexpr ::_pbi::TcParseTable<2, 3, 1, 0, 2> DescriptorProto_ExtensionRange::_t
   return MaybeComputeUnknownFieldsSize(total_size, &_impl_._cached_size_);
 }
 
-const ::google::protobuf::Message::ClassData DescriptorProto_ExtensionRange::_class_data_ = {
-    DescriptorProto_ExtensionRange::MergeImpl,
-    nullptr,  // OnDemandRegisterArenaDtor
-};
-const ::google::protobuf::Message::ClassData* DescriptorProto_ExtensionRange::GetClassData() const {
-  return &_class_data_;
-}
 
 void DescriptorProto_ExtensionRange::MergeImpl(::google::protobuf::Message& to_msg, const ::google::protobuf::Message& from_msg) {
   auto* const _this = static_cast<DescriptorProto_ExtensionRange*>(&to_msg);
@@ -3470,6 +3479,16 @@ inline void DescriptorProto_ReservedRange::SharedDtor() {
   _impl_.~Impl_();
 }
 
+const ::google::protobuf::MessageLite::ClassData*
+DescriptorProto_ReservedRange::GetClassData() const {
+  PROTOBUF_CONSTINIT static const ::google::protobuf::MessageLite::ClassData
+      data = {
+          DescriptorProto_ReservedRange::MergeImpl,
+           nullptr,  // OnDemandRegisterArenaDtor
+           &::google::protobuf::Message::kDescriptorMethods,
+      };
+  return &data;
+}
 PROTOBUF_NOINLINE void DescriptorProto_ReservedRange::Clear() {
 // @@protoc_insertion_point(message_clear_start:google.protobuf.DescriptorProto.ReservedRange)
   PROTOBUF_TSAN_WRITE(&_impl_._tsan_detect_race);
@@ -3586,13 +3605,6 @@ constexpr ::_pbi::TcParseTable<1, 2, 0, 0, 2> DescriptorProto_ReservedRange::_ta
   return MaybeComputeUnknownFieldsSize(total_size, &_impl_._cached_size_);
 }
 
-const ::google::protobuf::Message::ClassData DescriptorProto_ReservedRange::_class_data_ = {
-    DescriptorProto_ReservedRange::MergeImpl,
-    nullptr,  // OnDemandRegisterArenaDtor
-};
-const ::google::protobuf::Message::ClassData* DescriptorProto_ReservedRange::GetClassData() const {
-  return &_class_data_;
-}
 
 void DescriptorProto_ReservedRange::MergeImpl(::google::protobuf::Message& to_msg, const ::google::protobuf::Message& from_msg) {
   auto* const _this = static_cast<DescriptorProto_ReservedRange*>(&to_msg);
@@ -3731,6 +3743,16 @@ inline void DescriptorProto::SharedDtor() {
   _impl_.~Impl_();
 }
 
+const ::google::protobuf::MessageLite::ClassData*
+DescriptorProto::GetClassData() const {
+  PROTOBUF_CONSTINIT static const ::google::protobuf::MessageLite::ClassData
+      data = {
+          DescriptorProto::MergeImpl,
+           nullptr,  // OnDemandRegisterArenaDtor
+           &::google::protobuf::Message::kDescriptorMethods,
+      };
+  return &data;
+}
 PROTOBUF_NOINLINE void DescriptorProto::Clear() {
 // @@protoc_insertion_point(message_clear_start:google.protobuf.DescriptorProto)
   PROTOBUF_TSAN_WRITE(&_impl_._tsan_detect_race);
@@ -4037,13 +4059,6 @@ constexpr ::_pbi::TcParseTable<4, 10, 8, 65, 2> DescriptorProto::_table_ = {
   return MaybeComputeUnknownFieldsSize(total_size, &_impl_._cached_size_);
 }
 
-const ::google::protobuf::Message::ClassData DescriptorProto::_class_data_ = {
-    DescriptorProto::MergeImpl,
-    nullptr,  // OnDemandRegisterArenaDtor
-};
-const ::google::protobuf::Message::ClassData* DescriptorProto::GetClassData() const {
-  return &_class_data_;
-}
 
 void DescriptorProto::MergeImpl(::google::protobuf::Message& to_msg, const ::google::protobuf::Message& from_msg) {
   auto* const _this = static_cast<DescriptorProto*>(&to_msg);
@@ -4217,6 +4232,16 @@ inline void ExtensionRangeOptions_Declaration::SharedDtor() {
   _impl_.~Impl_();
 }
 
+const ::google::protobuf::MessageLite::ClassData*
+ExtensionRangeOptions_Declaration::GetClassData() const {
+  PROTOBUF_CONSTINIT static const ::google::protobuf::MessageLite::ClassData
+      data = {
+          ExtensionRangeOptions_Declaration::MergeImpl,
+           nullptr,  // OnDemandRegisterArenaDtor
+           &::google::protobuf::Message::kDescriptorMethods,
+      };
+  return &data;
+}
 PROTOBUF_NOINLINE void ExtensionRangeOptions_Declaration::Clear() {
 // @@protoc_insertion_point(message_clear_start:google.protobuf.ExtensionRangeOptions.Declaration)
   PROTOBUF_TSAN_WRITE(&_impl_._tsan_detect_race);
@@ -4405,13 +4430,6 @@ constexpr ::_pbi::TcParseTable<3, 5, 0, 71, 2> ExtensionRangeOptions_Declaration
   return MaybeComputeUnknownFieldsSize(total_size, &_impl_._cached_size_);
 }
 
-const ::google::protobuf::Message::ClassData ExtensionRangeOptions_Declaration::_class_data_ = {
-    ExtensionRangeOptions_Declaration::MergeImpl,
-    nullptr,  // OnDemandRegisterArenaDtor
-};
-const ::google::protobuf::Message::ClassData* ExtensionRangeOptions_Declaration::GetClassData() const {
-  return &_class_data_;
-}
 
 void ExtensionRangeOptions_Declaration::MergeImpl(::google::protobuf::Message& to_msg, const ::google::protobuf::Message& from_msg) {
   auto* const _this = static_cast<ExtensionRangeOptions_Declaration*>(&to_msg);
@@ -4553,6 +4571,16 @@ inline void ExtensionRangeOptions::SharedDtor() {
   _impl_.~Impl_();
 }
 
+const ::google::protobuf::MessageLite::ClassData*
+ExtensionRangeOptions::GetClassData() const {
+  PROTOBUF_CONSTINIT static const ::google::protobuf::MessageLite::ClassData
+      data = {
+          ExtensionRangeOptions::MergeImpl,
+           nullptr,  // OnDemandRegisterArenaDtor
+           &::google::protobuf::Message::kDescriptorMethods,
+      };
+  return &data;
+}
 PROTOBUF_NOINLINE void ExtensionRangeOptions::Clear() {
 // @@protoc_insertion_point(message_clear_start:google.protobuf.ExtensionRangeOptions)
   PROTOBUF_TSAN_WRITE(&_impl_._tsan_detect_race);
@@ -4727,13 +4755,6 @@ constexpr ::_pbi::TcParseTable<3, 4, 4, 0, 12> ExtensionRangeOptions::_table_ =
   return MaybeComputeUnknownFieldsSize(total_size, &_impl_._cached_size_);
 }
 
-const ::google::protobuf::Message::ClassData ExtensionRangeOptions::_class_data_ = {
-    ExtensionRangeOptions::MergeImpl,
-    nullptr,  // OnDemandRegisterArenaDtor
-};
-const ::google::protobuf::Message::ClassData* ExtensionRangeOptions::GetClassData() const {
-  return &_class_data_;
-}
 
 void ExtensionRangeOptions::MergeImpl(::google::protobuf::Message& to_msg, const ::google::protobuf::Message& from_msg) {
   auto* const _this = static_cast<ExtensionRangeOptions*>(&to_msg);
@@ -4926,6 +4947,16 @@ inline void FieldDescriptorProto::SharedDtor() {
   _impl_.~Impl_();
 }
 
+const ::google::protobuf::MessageLite::ClassData*
+FieldDescriptorProto::GetClassData() const {
+  PROTOBUF_CONSTINIT static const ::google::protobuf::MessageLite::ClassData
+      data = {
+          FieldDescriptorProto::MergeImpl,
+           nullptr,  // OnDemandRegisterArenaDtor
+           &::google::protobuf::Message::kDescriptorMethods,
+      };
+  return &data;
+}
 PROTOBUF_NOINLINE void FieldDescriptorProto::Clear() {
 // @@protoc_insertion_point(message_clear_start:google.protobuf.FieldDescriptorProto)
   PROTOBUF_TSAN_WRITE(&_impl_._tsan_detect_race);
@@ -5257,13 +5288,6 @@ constexpr ::_pbi::TcParseTable<4, 11, 3, 96, 2> FieldDescriptorProto::_table_ =
   return MaybeComputeUnknownFieldsSize(total_size, &_impl_._cached_size_);
 }
 
-const ::google::protobuf::Message::ClassData FieldDescriptorProto::_class_data_ = {
-    FieldDescriptorProto::MergeImpl,
-    nullptr,  // OnDemandRegisterArenaDtor
-};
-const ::google::protobuf::Message::ClassData* FieldDescriptorProto::GetClassData() const {
-  return &_class_data_;
-}
 
 void FieldDescriptorProto::MergeImpl(::google::protobuf::Message& to_msg, const ::google::protobuf::Message& from_msg) {
   auto* const _this = static_cast<FieldDescriptorProto*>(&to_msg);
@@ -5427,6 +5451,16 @@ inline void OneofDescriptorProto::SharedDtor() {
   _impl_.~Impl_();
 }
 
+const ::google::protobuf::MessageLite::ClassData*
+OneofDescriptorProto::GetClassData() const {
+  PROTOBUF_CONSTINIT static const ::google::protobuf::MessageLite::ClassData
+      data = {
+          OneofDescriptorProto::MergeImpl,
+           nullptr,  // OnDemandRegisterArenaDtor
+           &::google::protobuf::Message::kDescriptorMethods,
+      };
+  return &data;
+}
 PROTOBUF_NOINLINE void OneofDescriptorProto::Clear() {
 // @@protoc_insertion_point(message_clear_start:google.protobuf.OneofDescriptorProto)
   PROTOBUF_TSAN_WRITE(&_impl_._tsan_detect_race);
@@ -5551,13 +5585,6 @@ constexpr ::_pbi::TcParseTable<1, 2, 1, 49, 2> OneofDescriptorProto::_table_ = {
   return MaybeComputeUnknownFieldsSize(total_size, &_impl_._cached_size_);
 }
 
-const ::google::protobuf::Message::ClassData OneofDescriptorProto::_class_data_ = {
-    OneofDescriptorProto::MergeImpl,
-    nullptr,  // OnDemandRegisterArenaDtor
-};
-const ::google::protobuf::Message::ClassData* OneofDescriptorProto::GetClassData() const {
-  return &_class_data_;
-}
 
 void OneofDescriptorProto::MergeImpl(::google::protobuf::Message& to_msg, const ::google::protobuf::Message& from_msg) {
   auto* const _this = static_cast<OneofDescriptorProto*>(&to_msg);
@@ -5661,6 +5688,16 @@ inline void EnumDescriptorProto_EnumReservedRange::SharedDtor() {
   _impl_.~Impl_();
 }
 
+const ::google::protobuf::MessageLite::ClassData*
+EnumDescriptorProto_EnumReservedRange::GetClassData() const {
+  PROTOBUF_CONSTINIT static const ::google::protobuf::MessageLite::ClassData
+      data = {
+          EnumDescriptorProto_EnumReservedRange::MergeImpl,
+           nullptr,  // OnDemandRegisterArenaDtor
+           &::google::protobuf::Message::kDescriptorMethods,
+      };
+  return &data;
+}
 PROTOBUF_NOINLINE void EnumDescriptorProto_EnumReservedRange::Clear() {
 // @@protoc_insertion_point(message_clear_start:google.protobuf.EnumDescriptorProto.EnumReservedRange)
   PROTOBUF_TSAN_WRITE(&_impl_._tsan_detect_race);
@@ -5777,13 +5814,6 @@ constexpr ::_pbi::TcParseTable<1, 2, 0, 0, 2> EnumDescriptorProto_EnumReservedRa
   return MaybeComputeUnknownFieldsSize(total_size, &_impl_._cached_size_);
 }
 
-const ::google::protobuf::Message::ClassData EnumDescriptorProto_EnumReservedRange::_class_data_ = {
-    EnumDescriptorProto_EnumReservedRange::MergeImpl,
-    nullptr,  // OnDemandRegisterArenaDtor
-};
-const ::google::protobuf::Message::ClassData* EnumDescriptorProto_EnumReservedRange::GetClassData() const {
-  return &_class_data_;
-}
 
 void EnumDescriptorProto_EnumReservedRange::MergeImpl(::google::protobuf::Message& to_msg, const ::google::protobuf::Message& from_msg) {
   auto* const _this = static_cast<EnumDescriptorProto_EnumReservedRange*>(&to_msg);
@@ -5912,6 +5942,16 @@ inline void EnumDescriptorProto::SharedDtor() {
   _impl_.~Impl_();
 }
 
+const ::google::protobuf::MessageLite::ClassData*
+EnumDescriptorProto::GetClassData() const {
+  PROTOBUF_CONSTINIT static const ::google::protobuf::MessageLite::ClassData
+      data = {
+          EnumDescriptorProto::MergeImpl,
+           nullptr,  // OnDemandRegisterArenaDtor
+           &::google::protobuf::Message::kDescriptorMethods,
+      };
+  return &data;
+}
 PROTOBUF_NOINLINE void EnumDescriptorProto::Clear() {
 // @@protoc_insertion_point(message_clear_start:google.protobuf.EnumDescriptorProto)
   PROTOBUF_TSAN_WRITE(&_impl_._tsan_detect_race);
@@ -6105,13 +6145,6 @@ constexpr ::_pbi::TcParseTable<3, 5, 3, 61, 2> EnumDescriptorProto::_table_ = {
   return MaybeComputeUnknownFieldsSize(total_size, &_impl_._cached_size_);
 }
 
-const ::google::protobuf::Message::ClassData EnumDescriptorProto::_class_data_ = {
-    EnumDescriptorProto::MergeImpl,
-    nullptr,  // OnDemandRegisterArenaDtor
-};
-const ::google::protobuf::Message::ClassData* EnumDescriptorProto::GetClassData() const {
-  return &_class_data_;
-}
 
 void EnumDescriptorProto::MergeImpl(::google::protobuf::Message& to_msg, const ::google::protobuf::Message& from_msg) {
   auto* const _this = static_cast<EnumDescriptorProto*>(&to_msg);
@@ -6254,6 +6287,16 @@ inline void EnumValueDescriptorProto::SharedDtor() {
   _impl_.~Impl_();
 }
 
+const ::google::protobuf::MessageLite::ClassData*
+EnumValueDescriptorProto::GetClassData() const {
+  PROTOBUF_CONSTINIT static const ::google::protobuf::MessageLite::ClassData
+      data = {
+          EnumValueDescriptorProto::MergeImpl,
+           nullptr,  // OnDemandRegisterArenaDtor
+           &::google::protobuf::Message::kDescriptorMethods,
+      };
+  return &data;
+}
 PROTOBUF_NOINLINE void EnumValueDescriptorProto::Clear() {
 // @@protoc_insertion_point(message_clear_start:google.protobuf.EnumValueDescriptorProto)
   PROTOBUF_TSAN_WRITE(&_impl_._tsan_detect_race);
@@ -6399,13 +6442,6 @@ constexpr ::_pbi::TcParseTable<2, 3, 1, 53, 2> EnumValueDescriptorProto::_table_
   return MaybeComputeUnknownFieldsSize(total_size, &_impl_._cached_size_);
 }
 
-const ::google::protobuf::Message::ClassData EnumValueDescriptorProto::_class_data_ = {
-    EnumValueDescriptorProto::MergeImpl,
-    nullptr,  // OnDemandRegisterArenaDtor
-};
-const ::google::protobuf::Message::ClassData* EnumValueDescriptorProto::GetClassData() const {
-  return &_class_data_;
-}
 
 void EnumValueDescriptorProto::MergeImpl(::google::protobuf::Message& to_msg, const ::google::protobuf::Message& from_msg) {
   auto* const _this = static_cast<EnumValueDescriptorProto*>(&to_msg);
@@ -6540,6 +6576,16 @@ inline void ServiceDescriptorProto::SharedDtor() {
   _impl_.~Impl_();
 }
 
+const ::google::protobuf::MessageLite::ClassData*
+ServiceDescriptorProto::GetClassData() const {
+  PROTOBUF_CONSTINIT static const ::google::protobuf::MessageLite::ClassData
+      data = {
+          ServiceDescriptorProto::MergeImpl,
+           nullptr,  // OnDemandRegisterArenaDtor
+           &::google::protobuf::Message::kDescriptorMethods,
+      };
+  return &data;
+}
 PROTOBUF_NOINLINE void ServiceDescriptorProto::Clear() {
 // @@protoc_insertion_point(message_clear_start:google.protobuf.ServiceDescriptorProto)
   PROTOBUF_TSAN_WRITE(&_impl_._tsan_detect_race);
@@ -6687,13 +6733,6 @@ constexpr ::_pbi::TcParseTable<2, 3, 2, 51, 2> ServiceDescriptorProto::_table_ =
   return MaybeComputeUnknownFieldsSize(total_size, &_impl_._cached_size_);
 }
 
-const ::google::protobuf::Message::ClassData ServiceDescriptorProto::_class_data_ = {
-    ServiceDescriptorProto::MergeImpl,
-    nullptr,  // OnDemandRegisterArenaDtor
-};
-const ::google::protobuf::Message::ClassData* ServiceDescriptorProto::GetClassData() const {
-  return &_class_data_;
-}
 
 void ServiceDescriptorProto::MergeImpl(::google::protobuf::Message& to_msg, const ::google::protobuf::Message& from_msg) {
   auto* const _this = static_cast<ServiceDescriptorProto*>(&to_msg);
@@ -6852,6 +6891,16 @@ inline void MethodDescriptorProto::SharedDtor() {
   _impl_.~Impl_();
 }
 
+const ::google::protobuf::MessageLite::ClassData*
+MethodDescriptorProto::GetClassData() const {
+  PROTOBUF_CONSTINIT static const ::google::protobuf::MessageLite::ClassData
+      data = {
+          MethodDescriptorProto::MergeImpl,
+           nullptr,  // OnDemandRegisterArenaDtor
+           &::google::protobuf::Message::kDescriptorMethods,
+      };
+  return &data;
+}
 PROTOBUF_NOINLINE void MethodDescriptorProto::Clear() {
 // @@protoc_insertion_point(message_clear_start:google.protobuf.MethodDescriptorProto)
   PROTOBUF_TSAN_WRITE(&_impl_._tsan_detect_race);
@@ -7065,13 +7114,6 @@ constexpr ::_pbi::TcParseTable<3, 6, 1, 71, 2> MethodDescriptorProto::_table_ =
   return MaybeComputeUnknownFieldsSize(total_size, &_impl_._cached_size_);
 }
 
-const ::google::protobuf::Message::ClassData MethodDescriptorProto::_class_data_ = {
-    MethodDescriptorProto::MergeImpl,
-    nullptr,  // OnDemandRegisterArenaDtor
-};
-const ::google::protobuf::Message::ClassData* MethodDescriptorProto::GetClassData() const {
-  return &_class_data_;
-}
 
 void MethodDescriptorProto::MergeImpl(::google::protobuf::Message& to_msg, const ::google::protobuf::Message& from_msg) {
   auto* const _this = static_cast<MethodDescriptorProto*>(&to_msg);
@@ -7318,6 +7360,16 @@ inline void FileOptions::SharedDtor() {
   _impl_.~Impl_();
 }
 
+const ::google::protobuf::MessageLite::ClassData*
+FileOptions::GetClassData() const {
+  PROTOBUF_CONSTINIT static const ::google::protobuf::MessageLite::ClassData
+      data = {
+          FileOptions::MergeImpl,
+           nullptr,  // OnDemandRegisterArenaDtor
+           &::google::protobuf::Message::kDescriptorMethods,
+      };
+  return &data;
+}
 PROTOBUF_NOINLINE void FileOptions::Clear() {
 // @@protoc_insertion_point(message_clear_start:google.protobuf.FileOptions)
   PROTOBUF_TSAN_WRITE(&_impl_._tsan_detect_race);
@@ -7891,13 +7943,6 @@ constexpr ::_pbi::TcParseTable<5, 22, 3, 202, 12> FileOptions::_table_ = {
   return MaybeComputeUnknownFieldsSize(total_size, &_impl_._cached_size_);
 }
 
-const ::google::protobuf::Message::ClassData FileOptions::_class_data_ = {
-    FileOptions::MergeImpl,
-    nullptr,  // OnDemandRegisterArenaDtor
-};
-const ::google::protobuf::Message::ClassData* FileOptions::GetClassData() const {
-  return &_class_data_;
-}
 
 void FileOptions::MergeImpl(::google::protobuf::Message& to_msg, const ::google::protobuf::Message& from_msg) {
   auto* const _this = static_cast<FileOptions*>(&to_msg);
@@ -8134,6 +8179,16 @@ inline void MessageOptions::SharedDtor() {
   _impl_.~Impl_();
 }
 
+const ::google::protobuf::MessageLite::ClassData*
+MessageOptions::GetClassData() const {
+  PROTOBUF_CONSTINIT static const ::google::protobuf::MessageLite::ClassData
+      data = {
+          MessageOptions::MergeImpl,
+           nullptr,  // OnDemandRegisterArenaDtor
+           &::google::protobuf::Message::kDescriptorMethods,
+      };
+  return &data;
+}
 PROTOBUF_NOINLINE void MessageOptions::Clear() {
 // @@protoc_insertion_point(message_clear_start:google.protobuf.MessageOptions)
   PROTOBUF_TSAN_WRITE(&_impl_._tsan_detect_race);
@@ -8352,13 +8407,6 @@ constexpr ::_pbi::TcParseTable<3, 7, 2, 0, 7> MessageOptions::_table_ = {
   return MaybeComputeUnknownFieldsSize(total_size, &_impl_._cached_size_);
 }
 
-const ::google::protobuf::Message::ClassData MessageOptions::_class_data_ = {
-    MessageOptions::MergeImpl,
-    nullptr,  // OnDemandRegisterArenaDtor
-};
-const ::google::protobuf::Message::ClassData* MessageOptions::GetClassData() const {
-  return &_class_data_;
-}
 
 void MessageOptions::MergeImpl(::google::protobuf::Message& to_msg, const ::google::protobuf::Message& from_msg) {
   auto* const _this = static_cast<MessageOptions*>(&to_msg);
@@ -8499,6 +8547,16 @@ inline void FieldOptions_EditionDefault::SharedDtor() {
   _impl_.~Impl_();
 }
 
+const ::google::protobuf::MessageLite::ClassData*
+FieldOptions_EditionDefault::GetClassData() const {
+  PROTOBUF_CONSTINIT static const ::google::protobuf::MessageLite::ClassData
+      data = {
+          FieldOptions_EditionDefault::MergeImpl,
+           nullptr,  // OnDemandRegisterArenaDtor
+           &::google::protobuf::Message::kDescriptorMethods,
+      };
+  return &data;
+}
 PROTOBUF_NOINLINE void FieldOptions_EditionDefault::Clear() {
 // @@protoc_insertion_point(message_clear_start:google.protobuf.FieldOptions.EditionDefault)
   PROTOBUF_TSAN_WRITE(&_impl_._tsan_detect_race);
@@ -8618,13 +8676,6 @@ constexpr ::_pbi::TcParseTable<1, 2, 1, 57, 2> FieldOptions_EditionDefault::_tab
   return MaybeComputeUnknownFieldsSize(total_size, &_impl_._cached_size_);
 }
 
-const ::google::protobuf::Message::ClassData FieldOptions_EditionDefault::_class_data_ = {
-    FieldOptions_EditionDefault::MergeImpl,
-    nullptr,  // OnDemandRegisterArenaDtor
-};
-const ::google::protobuf::Message::ClassData* FieldOptions_EditionDefault::GetClassData() const {
-  return &_class_data_;
-}
 
 void FieldOptions_EditionDefault::MergeImpl(::google::protobuf::Message& to_msg, const ::google::protobuf::Message& from_msg) {
   auto* const _this = static_cast<FieldOptions_EditionDefault*>(&to_msg);
@@ -8787,6 +8838,16 @@ inline void FieldOptions::SharedDtor() {
   _impl_.~Impl_();
 }
 
+const ::google::protobuf::MessageLite::ClassData*
+FieldOptions::GetClassData() const {
+  PROTOBUF_CONSTINIT static const ::google::protobuf::MessageLite::ClassData
+      data = {
+          FieldOptions::MergeImpl,
+           nullptr,  // OnDemandRegisterArenaDtor
+           &::google::protobuf::Message::kDescriptorMethods,
+      };
+  return &data;
+}
 PROTOBUF_NOINLINE void FieldOptions::Clear() {
 // @@protoc_insertion_point(message_clear_start:google.protobuf.FieldOptions)
   PROTOBUF_TSAN_WRITE(&_impl_._tsan_detect_race);
@@ -9140,13 +9201,6 @@ constexpr ::_pbi::TcParseTable<4, 13, 7, 0, 7> FieldOptions::_table_ = {
   return MaybeComputeUnknownFieldsSize(total_size, &_impl_._cached_size_);
 }
 
-const ::google::protobuf::Message::ClassData FieldOptions::_class_data_ = {
-    FieldOptions::MergeImpl,
-    nullptr,  // OnDemandRegisterArenaDtor
-};
-const ::google::protobuf::Message::ClassData* FieldOptions::GetClassData() const {
-  return &_class_data_;
-}
 
 void FieldOptions::MergeImpl(::google::protobuf::Message& to_msg, const ::google::protobuf::Message& from_msg) {
   auto* const _this = static_cast<FieldOptions*>(&to_msg);
@@ -9314,6 +9368,16 @@ inline void OneofOptions::SharedDtor() {
   _impl_.~Impl_();
 }
 
+const ::google::protobuf::MessageLite::ClassData*
+OneofOptions::GetClassData() const {
+  PROTOBUF_CONSTINIT static const ::google::protobuf::MessageLite::ClassData
+      data = {
+          OneofOptions::MergeImpl,
+           nullptr,  // OnDemandRegisterArenaDtor
+           &::google::protobuf::Message::kDescriptorMethods,
+      };
+  return &data;
+}
 PROTOBUF_NOINLINE void OneofOptions::Clear() {
 // @@protoc_insertion_point(message_clear_start:google.protobuf.OneofOptions)
   PROTOBUF_TSAN_WRITE(&_impl_._tsan_detect_race);
@@ -9440,13 +9504,6 @@ constexpr ::_pbi::TcParseTable<2, 2, 2, 0, 7> OneofOptions::_table_ = {
   return MaybeComputeUnknownFieldsSize(total_size, &_impl_._cached_size_);
 }
 
-const ::google::protobuf::Message::ClassData OneofOptions::_class_data_ = {
-    OneofOptions::MergeImpl,
-    nullptr,  // OnDemandRegisterArenaDtor
-};
-const ::google::protobuf::Message::ClassData* OneofOptions::GetClassData() const {
-  return &_class_data_;
-}
 
 void OneofOptions::MergeImpl(::google::protobuf::Message& to_msg, const ::google::protobuf::Message& from_msg) {
   auto* const _this = static_cast<OneofOptions*>(&to_msg);
@@ -9591,6 +9648,16 @@ inline void EnumOptions::SharedDtor() {
   _impl_.~Impl_();
 }
 
+const ::google::protobuf::MessageLite::ClassData*
+EnumOptions::GetClassData() const {
+  PROTOBUF_CONSTINIT static const ::google::protobuf::MessageLite::ClassData
+      data = {
+          EnumOptions::MergeImpl,
+           nullptr,  // OnDemandRegisterArenaDtor
+           &::google::protobuf::Message::kDescriptorMethods,
+      };
+  return &data;
+}
 PROTOBUF_NOINLINE void EnumOptions::Clear() {
 // @@protoc_insertion_point(message_clear_start:google.protobuf.EnumOptions)
   PROTOBUF_TSAN_WRITE(&_impl_._tsan_detect_race);
@@ -9775,13 +9842,6 @@ constexpr ::_pbi::TcParseTable<3, 5, 2, 0, 7> EnumOptions::_table_ = {
   return MaybeComputeUnknownFieldsSize(total_size, &_impl_._cached_size_);
 }
 
-const ::google::protobuf::Message::ClassData EnumOptions::_class_data_ = {
-    EnumOptions::MergeImpl,
-    nullptr,  // OnDemandRegisterArenaDtor
-};
-const ::google::protobuf::Message::ClassData* EnumOptions::GetClassData() const {
-  return &_class_data_;
-}
 
 void EnumOptions::MergeImpl(::google::protobuf::Message& to_msg, const ::google::protobuf::Message& from_msg) {
   auto* const _this = static_cast<EnumOptions*>(&to_msg);
@@ -9941,6 +10001,16 @@ inline void EnumValueOptions::SharedDtor() {
   _impl_.~Impl_();
 }
 
+const ::google::protobuf::MessageLite::ClassData*
+EnumValueOptions::GetClassData() const {
+  PROTOBUF_CONSTINIT static const ::google::protobuf::MessageLite::ClassData
+      data = {
+          EnumValueOptions::MergeImpl,
+           nullptr,  // OnDemandRegisterArenaDtor
+           &::google::protobuf::Message::kDescriptorMethods,
+      };
+  return &data;
+}
 PROTOBUF_NOINLINE void EnumValueOptions::Clear() {
 // @@protoc_insertion_point(message_clear_start:google.protobuf.EnumValueOptions)
   PROTOBUF_TSAN_WRITE(&_impl_._tsan_detect_race);
@@ -10110,13 +10180,6 @@ constexpr ::_pbi::TcParseTable<3, 4, 2, 0, 7> EnumValueOptions::_table_ = {
   return MaybeComputeUnknownFieldsSize(total_size, &_impl_._cached_size_);
 }
 
-const ::google::protobuf::Message::ClassData EnumValueOptions::_class_data_ = {
-    EnumValueOptions::MergeImpl,
-    nullptr,  // OnDemandRegisterArenaDtor
-};
-const ::google::protobuf::Message::ClassData* EnumValueOptions::GetClassData() const {
-  return &_class_data_;
-}
 
 void EnumValueOptions::MergeImpl(::google::protobuf::Message& to_msg, const ::google::protobuf::Message& from_msg) {
   auto* const _this = static_cast<EnumValueOptions*>(&to_msg);
@@ -10264,6 +10327,16 @@ inline void ServiceOptions::SharedDtor() {
   _impl_.~Impl_();
 }
 
+const ::google::protobuf::MessageLite::ClassData*
+ServiceOptions::GetClassData() const {
+  PROTOBUF_CONSTINIT static const ::google::protobuf::MessageLite::ClassData
+      data = {
+          ServiceOptions::MergeImpl,
+           nullptr,  // OnDemandRegisterArenaDtor
+           &::google::protobuf::Message::kDescriptorMethods,
+      };
+  return &data;
+}
 PROTOBUF_NOINLINE void ServiceOptions::Clear() {
 // @@protoc_insertion_point(message_clear_start:google.protobuf.ServiceOptions)
   PROTOBUF_TSAN_WRITE(&_impl_._tsan_detect_race);
@@ -10411,13 +10484,6 @@ constexpr ::_pbi::TcParseTable<2, 3, 2, 0, 12> ServiceOptions::_table_ = {
   return MaybeComputeUnknownFieldsSize(total_size, &_impl_._cached_size_);
 }
 
-const ::google::protobuf::Message::ClassData ServiceOptions::_class_data_ = {
-    ServiceOptions::MergeImpl,
-    nullptr,  // OnDemandRegisterArenaDtor
-};
-const ::google::protobuf::Message::ClassData* ServiceOptions::GetClassData() const {
-  return &_class_data_;
-}
 
 void ServiceOptions::MergeImpl(::google::protobuf::Message& to_msg, const ::google::protobuf::Message& from_msg) {
   auto* const _this = static_cast<ServiceOptions*>(&to_msg);
@@ -10571,6 +10637,16 @@ inline void MethodOptions::SharedDtor() {
   _impl_.~Impl_();
 }
 
+const ::google::protobuf::MessageLite::ClassData*
+MethodOptions::GetClassData() const {
+  PROTOBUF_CONSTINIT static const ::google::protobuf::MessageLite::ClassData
+      data = {
+          MethodOptions::MergeImpl,
+           nullptr,  // OnDemandRegisterArenaDtor
+           &::google::protobuf::Message::kDescriptorMethods,
+      };
+  return &data;
+}
 PROTOBUF_NOINLINE void MethodOptions::Clear() {
 // @@protoc_insertion_point(message_clear_start:google.protobuf.MethodOptions)
   PROTOBUF_TSAN_WRITE(&_impl_._tsan_detect_race);
@@ -10745,13 +10821,6 @@ constexpr ::_pbi::TcParseTable<3, 4, 3, 0, 12> MethodOptions::_table_ = {
   return MaybeComputeUnknownFieldsSize(total_size, &_impl_._cached_size_);
 }
 
-const ::google::protobuf::Message::ClassData MethodOptions::_class_data_ = {
-    MethodOptions::MergeImpl,
-    nullptr,  // OnDemandRegisterArenaDtor
-};
-const ::google::protobuf::Message::ClassData* MethodOptions::GetClassData() const {
-  return &_class_data_;
-}
 
 void MethodOptions::MergeImpl(::google::protobuf::Message& to_msg, const ::google::protobuf::Message& from_msg) {
   auto* const _this = static_cast<MethodOptions*>(&to_msg);
@@ -10886,6 +10955,16 @@ inline void UninterpretedOption_NamePart::SharedDtor() {
   _impl_.~Impl_();
 }
 
+const ::google::protobuf::MessageLite::ClassData*
+UninterpretedOption_NamePart::GetClassData() const {
+  PROTOBUF_CONSTINIT static const ::google::protobuf::MessageLite::ClassData
+      data = {
+          UninterpretedOption_NamePart::MergeImpl,
+           nullptr,  // OnDemandRegisterArenaDtor
+           &::google::protobuf::Message::kDescriptorMethods,
+      };
+  return &data;
+}
 PROTOBUF_NOINLINE void UninterpretedOption_NamePart::Clear() {
 // @@protoc_insertion_point(message_clear_start:google.protobuf.UninterpretedOption.NamePart)
   PROTOBUF_TSAN_WRITE(&_impl_._tsan_detect_race);
@@ -11004,13 +11083,6 @@ constexpr ::_pbi::TcParseTable<1, 2, 0, 62, 2> UninterpretedOption_NamePart::_ta
   return MaybeComputeUnknownFieldsSize(total_size, &_impl_._cached_size_);
 }
 
-const ::google::protobuf::Message::ClassData UninterpretedOption_NamePart::_class_data_ = {
-    UninterpretedOption_NamePart::MergeImpl,
-    nullptr,  // OnDemandRegisterArenaDtor
-};
-const ::google::protobuf::Message::ClassData* UninterpretedOption_NamePart::GetClassData() const {
-  return &_class_data_;
-}
 
 void UninterpretedOption_NamePart::MergeImpl(::google::protobuf::Message& to_msg, const ::google::protobuf::Message& from_msg) {
   auto* const _this = static_cast<UninterpretedOption_NamePart*>(&to_msg);
@@ -11157,6 +11229,16 @@ inline void UninterpretedOption::SharedDtor() {
   _impl_.~Impl_();
 }
 
+const ::google::protobuf::MessageLite::ClassData*
+UninterpretedOption::GetClassData() const {
+  PROTOBUF_CONSTINIT static const ::google::protobuf::MessageLite::ClassData
+      data = {
+          UninterpretedOption::MergeImpl,
+           nullptr,  // OnDemandRegisterArenaDtor
+           &::google::protobuf::Message::kDescriptorMethods,
+      };
+  return &data;
+}
 PROTOBUF_NOINLINE void UninterpretedOption::Clear() {
 // @@protoc_insertion_point(message_clear_start:google.protobuf.UninterpretedOption)
   PROTOBUF_TSAN_WRITE(&_impl_._tsan_detect_race);
@@ -11386,13 +11468,6 @@ constexpr ::_pbi::TcParseTable<3, 7, 1, 75, 2> UninterpretedOption::_table_ = {
   return MaybeComputeUnknownFieldsSize(total_size, &_impl_._cached_size_);
 }
 
-const ::google::protobuf::Message::ClassData UninterpretedOption::_class_data_ = {
-    UninterpretedOption::MergeImpl,
-    nullptr,  // OnDemandRegisterArenaDtor
-};
-const ::google::protobuf::Message::ClassData* UninterpretedOption::GetClassData() const {
-  return &_class_data_;
-}
 
 void UninterpretedOption::MergeImpl(::google::protobuf::Message& to_msg, const ::google::protobuf::Message& from_msg) {
   auto* const _this = static_cast<UninterpretedOption*>(&to_msg);
@@ -11552,6 +11627,16 @@ inline void FeatureSet::SharedDtor() {
   _impl_.~Impl_();
 }
 
+const ::google::protobuf::MessageLite::ClassData*
+FeatureSet::GetClassData() const {
+  PROTOBUF_CONSTINIT static const ::google::protobuf::MessageLite::ClassData
+      data = {
+          FeatureSet::MergeImpl,
+           nullptr,  // OnDemandRegisterArenaDtor
+           &::google::protobuf::Message::kDescriptorMethods,
+      };
+  return &data;
+}
 PROTOBUF_NOINLINE void FeatureSet::Clear() {
 // @@protoc_insertion_point(message_clear_start:google.protobuf.FeatureSet)
   PROTOBUF_TSAN_WRITE(&_impl_._tsan_detect_race);
@@ -11757,13 +11842,6 @@ constexpr ::_pbi::TcParseTable<3, 6, 6, 0, 2> FeatureSet::_table_ = {
   return MaybeComputeUnknownFieldsSize(total_size, &_impl_._cached_size_);
 }
 
-const ::google::protobuf::Message::ClassData FeatureSet::_class_data_ = {
-    FeatureSet::MergeImpl,
-    nullptr,  // OnDemandRegisterArenaDtor
-};
-const ::google::protobuf::Message::ClassData* FeatureSet::GetClassData() const {
-  return &_class_data_;
-}
 
 void FeatureSet::MergeImpl(::google::protobuf::Message& to_msg, const ::google::protobuf::Message& from_msg) {
   auto* const _this = static_cast<FeatureSet*>(&to_msg);
@@ -11906,6 +11984,16 @@ inline void FeatureSetDefaults_FeatureSetEditionDefault::SharedDtor() {
   _impl_.~Impl_();
 }
 
+const ::google::protobuf::MessageLite::ClassData*
+FeatureSetDefaults_FeatureSetEditionDefault::GetClassData() const {
+  PROTOBUF_CONSTINIT static const ::google::protobuf::MessageLite::ClassData
+      data = {
+          FeatureSetDefaults_FeatureSetEditionDefault::MergeImpl,
+           nullptr,  // OnDemandRegisterArenaDtor
+           &::google::protobuf::Message::kDescriptorMethods,
+      };
+  return &data;
+}
 PROTOBUF_NOINLINE void FeatureSetDefaults_FeatureSetEditionDefault::Clear() {
 // @@protoc_insertion_point(message_clear_start:google.protobuf.FeatureSetDefaults.FeatureSetEditionDefault)
   PROTOBUF_TSAN_WRITE(&_impl_._tsan_detect_race);
@@ -12023,13 +12111,6 @@ constexpr ::_pbi::TcParseTable<1, 2, 2, 0, 2> FeatureSetDefaults_FeatureSetEditi
   return MaybeComputeUnknownFieldsSize(total_size, &_impl_._cached_size_);
 }
 
-const ::google::protobuf::Message::ClassData FeatureSetDefaults_FeatureSetEditionDefault::_class_data_ = {
-    FeatureSetDefaults_FeatureSetEditionDefault::MergeImpl,
-    nullptr,  // OnDemandRegisterArenaDtor
-};
-const ::google::protobuf::Message::ClassData* FeatureSetDefaults_FeatureSetEditionDefault::GetClassData() const {
-  return &_class_data_;
-}
 
 void FeatureSetDefaults_FeatureSetEditionDefault::MergeImpl(::google::protobuf::Message& to_msg, const ::google::protobuf::Message& from_msg) {
   auto* const _this = static_cast<FeatureSetDefaults_FeatureSetEditionDefault*>(&to_msg);
@@ -12158,6 +12239,16 @@ inline void FeatureSetDefaults::SharedDtor() {
   _impl_.~Impl_();
 }
 
+const ::google::protobuf::MessageLite::ClassData*
+FeatureSetDefaults::GetClassData() const {
+  PROTOBUF_CONSTINIT static const ::google::protobuf::MessageLite::ClassData
+      data = {
+          FeatureSetDefaults::MergeImpl,
+           nullptr,  // OnDemandRegisterArenaDtor
+           &::google::protobuf::Message::kDescriptorMethods,
+      };
+  return &data;
+}
 PROTOBUF_NOINLINE void FeatureSetDefaults::Clear() {
 // @@protoc_insertion_point(message_clear_start:google.protobuf.FeatureSetDefaults)
   PROTOBUF_TSAN_WRITE(&_impl_._tsan_detect_race);
@@ -12294,13 +12385,6 @@ constexpr ::_pbi::TcParseTable<1, 3, 3, 0, 2> FeatureSetDefaults::_table_ = {
   return MaybeComputeUnknownFieldsSize(total_size, &_impl_._cached_size_);
 }
 
-const ::google::protobuf::Message::ClassData FeatureSetDefaults::_class_data_ = {
-    FeatureSetDefaults::MergeImpl,
-    nullptr,  // OnDemandRegisterArenaDtor
-};
-const ::google::protobuf::Message::ClassData* FeatureSetDefaults::GetClassData() const {
-  return &_class_data_;
-}
 
 void FeatureSetDefaults::MergeImpl(::google::protobuf::Message& to_msg, const ::google::protobuf::Message& from_msg) {
   auto* const _this = static_cast<FeatureSetDefaults*>(&to_msg);
@@ -12431,6 +12515,16 @@ inline void SourceCodeInfo_Location::SharedDtor() {
   _impl_.~Impl_();
 }
 
+const ::google::protobuf::MessageLite::ClassData*
+SourceCodeInfo_Location::GetClassData() const {
+  PROTOBUF_CONSTINIT static const ::google::protobuf::MessageLite::ClassData
+      data = {
+          SourceCodeInfo_Location::MergeImpl,
+           nullptr,  // OnDemandRegisterArenaDtor
+           &::google::protobuf::Message::kDescriptorMethods,
+      };
+  return &data;
+}
 PROTOBUF_NOINLINE void SourceCodeInfo_Location::Clear() {
 // @@protoc_insertion_point(message_clear_start:google.protobuf.SourceCodeInfo.Location)
   PROTOBUF_TSAN_WRITE(&_impl_._tsan_detect_race);
@@ -12639,13 +12733,6 @@ constexpr ::_pbi::TcParseTable<3, 5, 0, 106, 2> SourceCodeInfo_Location::_table_
   return MaybeComputeUnknownFieldsSize(total_size, &_impl_._cached_size_);
 }
 
-const ::google::protobuf::Message::ClassData SourceCodeInfo_Location::_class_data_ = {
-    SourceCodeInfo_Location::MergeImpl,
-    nullptr,  // OnDemandRegisterArenaDtor
-};
-const ::google::protobuf::Message::ClassData* SourceCodeInfo_Location::GetClassData() const {
-  return &_class_data_;
-}
 
 void SourceCodeInfo_Location::MergeImpl(::google::protobuf::Message& to_msg, const ::google::protobuf::Message& from_msg) {
   auto* const _this = static_cast<SourceCodeInfo_Location*>(&to_msg);
@@ -12750,6 +12837,16 @@ inline void SourceCodeInfo::SharedDtor() {
   _impl_.~Impl_();
 }
 
+const ::google::protobuf::MessageLite::ClassData*
+SourceCodeInfo::GetClassData() const {
+  PROTOBUF_CONSTINIT static const ::google::protobuf::MessageLite::ClassData
+      data = {
+          SourceCodeInfo::MergeImpl,
+           nullptr,  // OnDemandRegisterArenaDtor
+           &::google::protobuf::Message::kDescriptorMethods,
+      };
+  return &data;
+}
 PROTOBUF_NOINLINE void SourceCodeInfo::Clear() {
 // @@protoc_insertion_point(message_clear_start:google.protobuf.SourceCodeInfo)
   PROTOBUF_TSAN_WRITE(&_impl_._tsan_detect_race);
@@ -12838,13 +12935,6 @@ constexpr ::_pbi::TcParseTable<0, 1, 1, 0, 2> SourceCodeInfo::_table_ = {
   return MaybeComputeUnknownFieldsSize(total_size, &_impl_._cached_size_);
 }
 
-const ::google::protobuf::Message::ClassData SourceCodeInfo::_class_data_ = {
-    SourceCodeInfo::MergeImpl,
-    nullptr,  // OnDemandRegisterArenaDtor
-};
-const ::google::protobuf::Message::ClassData* SourceCodeInfo::GetClassData() const {
-  return &_class_data_;
-}
 
 void SourceCodeInfo::MergeImpl(::google::protobuf::Message& to_msg, const ::google::protobuf::Message& from_msg) {
   auto* const _this = static_cast<SourceCodeInfo*>(&to_msg);
@@ -12966,6 +13056,16 @@ inline void GeneratedCodeInfo_Annotation::SharedDtor() {
   _impl_.~Impl_();
 }
 
+const ::google::protobuf::MessageLite::ClassData*
+GeneratedCodeInfo_Annotation::GetClassData() const {
+  PROTOBUF_CONSTINIT static const ::google::protobuf::MessageLite::ClassData
+      data = {
+          GeneratedCodeInfo_Annotation::MergeImpl,
+           nullptr,  // OnDemandRegisterArenaDtor
+           &::google::protobuf::Message::kDescriptorMethods,
+      };
+  return &data;
+}
 PROTOBUF_NOINLINE void GeneratedCodeInfo_Annotation::Clear() {
 // @@protoc_insertion_point(message_clear_start:google.protobuf.GeneratedCodeInfo.Annotation)
   PROTOBUF_TSAN_WRITE(&_impl_._tsan_detect_race);
@@ -13159,13 +13259,6 @@ constexpr ::_pbi::TcParseTable<3, 5, 1, 64, 2> GeneratedCodeInfo_Annotation::_ta
   return MaybeComputeUnknownFieldsSize(total_size, &_impl_._cached_size_);
 }
 
-const ::google::protobuf::Message::ClassData GeneratedCodeInfo_Annotation::_class_data_ = {
-    GeneratedCodeInfo_Annotation::MergeImpl,
-    nullptr,  // OnDemandRegisterArenaDtor
-};
-const ::google::protobuf::Message::ClassData* GeneratedCodeInfo_Annotation::GetClassData() const {
-  return &_class_data_;
-}
 
 void GeneratedCodeInfo_Annotation::MergeImpl(::google::protobuf::Message& to_msg, const ::google::protobuf::Message& from_msg) {
   auto* const _this = static_cast<GeneratedCodeInfo_Annotation*>(&to_msg);
@@ -13278,6 +13371,16 @@ inline void GeneratedCodeInfo::SharedDtor() {
   _impl_.~Impl_();
 }
 
+const ::google::protobuf::MessageLite::ClassData*
+GeneratedCodeInfo::GetClassData() const {
+  PROTOBUF_CONSTINIT static const ::google::protobuf::MessageLite::ClassData
+      data = {
+          GeneratedCodeInfo::MergeImpl,
+           nullptr,  // OnDemandRegisterArenaDtor
+           &::google::protobuf::Message::kDescriptorMethods,
+      };
+  return &data;
+}
 PROTOBUF_NOINLINE void GeneratedCodeInfo::Clear() {
 // @@protoc_insertion_point(message_clear_start:google.protobuf.GeneratedCodeInfo)
   PROTOBUF_TSAN_WRITE(&_impl_._tsan_detect_race);
@@ -13366,13 +13469,6 @@ constexpr ::_pbi::TcParseTable<0, 1, 1, 0, 2> GeneratedCodeInfo::_table_ = {
   return MaybeComputeUnknownFieldsSize(total_size, &_impl_._cached_size_);
 }
 
-const ::google::protobuf::Message::ClassData GeneratedCodeInfo::_class_data_ = {
-    GeneratedCodeInfo::MergeImpl,
-    nullptr,  // OnDemandRegisterArenaDtor
-};
-const ::google::protobuf::Message::ClassData* GeneratedCodeInfo::GetClassData() const {
-  return &_class_data_;
-}
 
 void GeneratedCodeInfo::MergeImpl(::google::protobuf::Message& to_msg, const ::google::protobuf::Message& from_msg) {
   auto* const _this = static_cast<GeneratedCodeInfo*>(&to_msg);

src/google/protobuf/descriptor.pb.h

@@ -822,11 +822,9 @@ class PROTOBUF_EXPORT UninterpretedOption_NamePart final :
   protected:
   explicit UninterpretedOption_NamePart(::google::protobuf::Arena* arena);
   UninterpretedOption_NamePart(::google::protobuf::Arena* arena, const UninterpretedOption_NamePart& from);
+  const ::google::protobuf::MessageLite::ClassData* GetClassData() const final;
   public:
 
-  static const ClassData _class_data_;
-  const ::google::protobuf::Message::ClassData*GetClassData() const final;
-
   ::google::protobuf::Metadata GetMetadata() const final;
 
   // nested types ----------------------------------------------------
@@ -1018,11 +1016,9 @@ class PROTOBUF_EXPORT SourceCodeInfo_Location final :
   protected:
   explicit SourceCodeInfo_Location(::google::protobuf::Arena* arena);
   SourceCodeInfo_Location(::google::protobuf::Arena* arena, const SourceCodeInfo_Location& from);
+  const ::google::protobuf::MessageLite::ClassData* GetClassData() const final;
   public:
 
-  static const ClassData _class_data_;
-  const ::google::protobuf::Message::ClassData*GetClassData() const final;
-
   ::google::protobuf::Metadata GetMetadata() const final;
 
   // nested types ----------------------------------------------------
@@ -1292,11 +1288,9 @@ class PROTOBUF_EXPORT GeneratedCodeInfo_Annotation final :
   protected:
   explicit GeneratedCodeInfo_Annotation(::google::protobuf::Arena* arena);
   GeneratedCodeInfo_Annotation(::google::protobuf::Arena* arena, const GeneratedCodeInfo_Annotation& from);
+  const ::google::protobuf::MessageLite::ClassData* GetClassData() const final;
   public:
 
-  static const ClassData _class_data_;
-  const ::google::protobuf::Message::ClassData*GetClassData() const final;
-
   ::google::protobuf::Metadata GetMetadata() const final;
 
   // nested types ----------------------------------------------------
@@ -1556,11 +1550,9 @@ class PROTOBUF_EXPORT FieldOptions_EditionDefault final :
   protected:
   explicit FieldOptions_EditionDefault(::google::protobuf::Arena* arena);
   FieldOptions_EditionDefault(::google::protobuf::Arena* arena, const FieldOptions_EditionDefault& from);
+  const ::google::protobuf::MessageLite::ClassData* GetClassData() const final;
   public:
 
-  static const ClassData _class_data_;
-  const ::google::protobuf::Message::ClassData*GetClassData() const final;
-
   ::google::protobuf::Metadata GetMetadata() const final;
 
   // nested types ----------------------------------------------------
@@ -1752,11 +1744,9 @@ class PROTOBUF_EXPORT FeatureSet final :
   protected:
   explicit FeatureSet(::google::protobuf::Arena* arena);
   FeatureSet(::google::protobuf::Arena* arena, const FeatureSet& from);
+  const ::google::protobuf::MessageLite::ClassData* GetClassData() const final;
   public:
 
-  static const ClassData _class_data_;
-  const ::google::protobuf::Message::ClassData*GetClassData() const final;
-
   ::google::protobuf::Metadata GetMetadata() const final;
 
   // nested types ----------------------------------------------------
@@ -2300,11 +2290,9 @@ class PROTOBUF_EXPORT ExtensionRangeOptions_Declaration final :
   protected:
   explicit ExtensionRangeOptions_Declaration(::google::protobuf::Arena* arena);
   ExtensionRangeOptions_Declaration(::google::protobuf::Arena* arena, const ExtensionRangeOptions_Declaration& from);
+  const ::google::protobuf::MessageLite::ClassData* GetClassData() const final;
   public:
 
-  static const ClassData _class_data_;
-  const ::google::protobuf::Message::ClassData*GetClassData() const final;
-
   ::google::protobuf::Metadata GetMetadata() const final;
 
   // nested types ----------------------------------------------------
@@ -2541,11 +2529,9 @@ class PROTOBUF_EXPORT EnumDescriptorProto_EnumReservedRange final :
   protected:
   explicit EnumDescriptorProto_EnumReservedRange(::google::protobuf::Arena* arena);
   EnumDescriptorProto_EnumReservedRange(::google::protobuf::Arena* arena, const EnumDescriptorProto_EnumReservedRange& from);
+  const ::google::protobuf::MessageLite::ClassData* GetClassData() const final;
   public:
 
-  static const ClassData _class_data_;
-  const ::google::protobuf::Message::ClassData*GetClassData() const final;
-
   ::google::protobuf::Metadata GetMetadata() const final;
 
   // nested types ----------------------------------------------------
@@ -2731,11 +2717,9 @@ class PROTOBUF_EXPORT DescriptorProto_ReservedRange final :
   protected:
   explicit DescriptorProto_ReservedRange(::google::protobuf::Arena* arena);
   DescriptorProto_ReservedRange(::google::protobuf::Arena* arena, const DescriptorProto_ReservedRange& from);
+  const ::google::protobuf::MessageLite::ClassData* GetClassData() const final;
   public:
 
-  static const ClassData _class_data_;
-  const ::google::protobuf::Message::ClassData*GetClassData() const final;
-
   ::google::protobuf::Metadata GetMetadata() const final;
 
   // nested types ----------------------------------------------------
@@ -2921,11 +2905,9 @@ class PROTOBUF_EXPORT UninterpretedOption final :
   protected:
   explicit UninterpretedOption(::google::protobuf::Arena* arena);
   UninterpretedOption(::google::protobuf::Arena* arena, const UninterpretedOption& from);
+  const ::google::protobuf::MessageLite::ClassData* GetClassData() const final;
   public:
 
-  static const ClassData _class_data_;
-  const ::google::protobuf::Message::ClassData*GetClassData() const final;
-
   ::google::protobuf::Metadata GetMetadata() const final;
 
   // nested types ----------------------------------------------------
@@ -3203,11 +3185,9 @@ class PROTOBUF_EXPORT SourceCodeInfo final :
   protected:
   explicit SourceCodeInfo(::google::protobuf::Arena* arena);
   SourceCodeInfo(::google::protobuf::Arena* arena, const SourceCodeInfo& from);
+  const ::google::protobuf::MessageLite::ClassData* GetClassData() const final;
   public:
 
-  static const ClassData _class_data_;
-  const ::google::protobuf::Message::ClassData*GetClassData() const final;
-
   ::google::protobuf::Metadata GetMetadata() const final;
 
   // nested types ----------------------------------------------------
@@ -3388,11 +3368,9 @@ class PROTOBUF_EXPORT GeneratedCodeInfo final :
   protected:
   explicit GeneratedCodeInfo(::google::protobuf::Arena* arena);
   GeneratedCodeInfo(::google::protobuf::Arena* arena, const GeneratedCodeInfo& from);
+  const ::google::protobuf::MessageLite::ClassData* GetClassData() const final;
   public:
 
-  static const ClassData _class_data_;
-  const ::google::protobuf::Message::ClassData*GetClassData() const final;
-
   ::google::protobuf::Metadata GetMetadata() const final;
 
   // nested types ----------------------------------------------------
@@ -3573,11 +3551,9 @@ class PROTOBUF_EXPORT FeatureSetDefaults_FeatureSetEditionDefault final :
   protected:
   explicit FeatureSetDefaults_FeatureSetEditionDefault(::google::protobuf::Arena* arena);
   FeatureSetDefaults_FeatureSetEditionDefault(::google::protobuf::Arena* arena, const FeatureSetDefaults_FeatureSetEditionDefault& from);
+  const ::google::protobuf::MessageLite::ClassData* GetClassData() const final;
   public:
 
-  static const ClassData _class_data_;
-  const ::google::protobuf::Message::ClassData*GetClassData() const final;
-
   ::google::protobuf::Metadata GetMetadata() const final;
 
   // nested types ----------------------------------------------------
@@ -3767,11 +3743,9 @@ class PROTOBUF_EXPORT ServiceOptions final :
   protected:
   explicit ServiceOptions(::google::protobuf::Arena* arena);
   ServiceOptions(::google::protobuf::Arena* arena, const ServiceOptions& from);
+  const ::google::protobuf::MessageLite::ClassData* GetClassData() const final;
   public:
 
-  static const ClassData _class_data_;
-  const ::google::protobuf::Message::ClassData*GetClassData() const final;
-
   ::google::protobuf::Metadata GetMetadata() const final;
 
   // nested types ----------------------------------------------------
@@ -4160,11 +4134,9 @@ class PROTOBUF_EXPORT OneofOptions final :
   protected:
   explicit OneofOptions(::google::protobuf::Arena* arena);
   OneofOptions(::google::protobuf::Arena* arena, const OneofOptions& from);
+  const ::google::protobuf::MessageLite::ClassData* GetClassData() const final;
   public:
 
-  static const ClassData _class_data_;
-  const ::google::protobuf::Message::ClassData*GetClassData() const final;
-
   ::google::protobuf::Metadata GetMetadata() const final;
 
   // nested types ----------------------------------------------------
@@ -4540,11 +4512,9 @@ class PROTOBUF_EXPORT MethodOptions final :
   protected:
   explicit MethodOptions(::google::protobuf::Arena* arena);
   MethodOptions(::google::protobuf::Arena* arena, const MethodOptions& from);
+  const ::google::protobuf::MessageLite::ClassData* GetClassData() const final;
   public:
 
-  static const ClassData _class_data_;
-  const ::google::protobuf::Message::ClassData*GetClassData() const final;
-
   ::google::protobuf::Metadata GetMetadata() const final;
 
   // nested types ----------------------------------------------------
@@ -4967,11 +4937,9 @@ class PROTOBUF_EXPORT MessageOptions final :
   protected:
   explicit MessageOptions(::google::protobuf::Arena* arena);
   MessageOptions(::google::protobuf::Arena* arena, const MessageOptions& from);
+  const ::google::protobuf::MessageLite::ClassData* GetClassData() const final;
   public:
 
-  static const ClassData _class_data_;
-  const ::google::protobuf::Message::ClassData*GetClassData() const final;
-
   ::google::protobuf::Metadata GetMetadata() const final;
 
   // nested types ----------------------------------------------------
@@ -5412,11 +5380,9 @@ class PROTOBUF_EXPORT FileOptions final :
   protected:
   explicit FileOptions(::google::protobuf::Arena* arena);
   FileOptions(::google::protobuf::Arena* arena, const FileOptions& from);
+  const ::google::protobuf::MessageLite::ClassData* GetClassData() const final;
   public:
 
-  static const ClassData _class_data_;
-  const ::google::protobuf::Message::ClassData*GetClassData() const final;
-
   ::google::protobuf::Metadata GetMetadata() const final;
 
   // nested types ----------------------------------------------------
@@ -6133,11 +6099,9 @@ class PROTOBUF_EXPORT FieldOptions final :
   protected:
   explicit FieldOptions(::google::protobuf::Arena* arena);
   FieldOptions(::google::protobuf::Arena* arena, const FieldOptions& from);
+  const ::google::protobuf::MessageLite::ClassData* GetClassData() const final;
   public:
 
-  static const ClassData _class_data_;
-  const ::google::protobuf::Message::ClassData*GetClassData() const final;
-
   ::google::protobuf::Metadata GetMetadata() const final;
 
   // nested types ----------------------------------------------------
@@ -6764,11 +6728,9 @@ class PROTOBUF_EXPORT FeatureSetDefaults final :
   protected:
   explicit FeatureSetDefaults(::google::protobuf::Arena* arena);
   FeatureSetDefaults(::google::protobuf::Arena* arena, const FeatureSetDefaults& from);
+  const ::google::protobuf::MessageLite::ClassData* GetClassData() const final;
   public:
 
-  static const ClassData _class_data_;
-  const ::google::protobuf::Message::ClassData*GetClassData() const final;
-
   ::google::protobuf::Metadata GetMetadata() const final;
 
   // nested types ----------------------------------------------------
@@ -6976,11 +6938,9 @@ class PROTOBUF_EXPORT ExtensionRangeOptions final :
   protected:
   explicit ExtensionRangeOptions(::google::protobuf::Arena* arena);
   ExtensionRangeOptions(::google::protobuf::Arena* arena, const ExtensionRangeOptions& from);
+  const ::google::protobuf::MessageLite::ClassData* GetClassData() const final;
   public:
 
-  static const ClassData _class_data_;
-  const ::google::protobuf::Message::ClassData*GetClassData() const final;
-
   ::google::protobuf::Metadata GetMetadata() const final;
 
   // nested types ----------------------------------------------------
@@ -7411,11 +7371,9 @@ class PROTOBUF_EXPORT EnumValueOptions final :
   protected:
   explicit EnumValueOptions(::google::protobuf::Arena* arena);
   EnumValueOptions(::google::protobuf::Arena* arena, const EnumValueOptions& from);
+  const ::google::protobuf::MessageLite::ClassData* GetClassData() const final;
   public:
 
-  static const ClassData _class_data_;
-  const ::google::protobuf::Message::ClassData*GetClassData() const final;
-
   ::google::protobuf::Metadata GetMetadata() const final;
 
   // nested types ----------------------------------------------------
@@ -7817,11 +7775,9 @@ class PROTOBUF_EXPORT EnumOptions final :
   protected:
   explicit EnumOptions(::google::protobuf::Arena* arena);
   EnumOptions(::google::protobuf::Arena* arena, const EnumOptions& from);
+  const ::google::protobuf::MessageLite::ClassData* GetClassData() const final;
   public:
 
-  static const ClassData _class_data_;
-  const ::google::protobuf::Message::ClassData*GetClassData() const final;
-
   ::google::protobuf::Metadata GetMetadata() const final;
 
   // nested types ----------------------------------------------------
@@ -8236,11 +8192,9 @@ class PROTOBUF_EXPORT OneofDescriptorProto final :
   protected:
   explicit OneofDescriptorProto(::google::protobuf::Arena* arena);
   OneofDescriptorProto(::google::protobuf::Arena* arena, const OneofDescriptorProto& from);
+  const ::google::protobuf::MessageLite::ClassData* GetClassData() const final;
   public:
 
-  static const ClassData _class_data_;
-  const ::google::protobuf::Message::ClassData*GetClassData() const final;
-
   ::google::protobuf::Metadata GetMetadata() const final;
 
   // nested types ----------------------------------------------------
@@ -8436,11 +8390,9 @@ class PROTOBUF_EXPORT MethodDescriptorProto final :
   protected:
   explicit MethodDescriptorProto(::google::protobuf::Arena* arena);
   MethodDescriptorProto(::google::protobuf::Arena* arena, const MethodDescriptorProto& from);
+  const ::google::protobuf::MessageLite::ClassData* GetClassData() const final;
   public:
 
-  static const ClassData _class_data_;
-  const ::google::protobuf::Message::ClassData*GetClassData() const final;
-
   ::google::protobuf::Metadata GetMetadata() const final;
 
   // nested types ----------------------------------------------------
@@ -8700,11 +8652,9 @@ class PROTOBUF_EXPORT FieldDescriptorProto final :
   protected:
   explicit FieldDescriptorProto(::google::protobuf::Arena* arena);
   FieldDescriptorProto(::google::protobuf::Arena* arena, const FieldDescriptorProto& from);
+  const ::google::protobuf::MessageLite::ClassData* GetClassData() const final;
   public:
 
-  static const ClassData _class_data_;
-  const ::google::protobuf::Message::ClassData*GetClassData() const final;
-
   ::google::protobuf::Metadata GetMetadata() const final;
 
   // nested types ----------------------------------------------------
@@ -9098,11 +9048,9 @@ class PROTOBUF_EXPORT EnumValueDescriptorProto final :
   protected:
   explicit EnumValueDescriptorProto(::google::protobuf::Arena* arena);
   EnumValueDescriptorProto(::google::protobuf::Arena* arena, const EnumValueDescriptorProto& from);
+  const ::google::protobuf::MessageLite::ClassData* GetClassData() const final;
   public:
 
-  static const ClassData _class_data_;
-  const ::google::protobuf::Message::ClassData*GetClassData() const final;
-
   ::google::protobuf::Metadata GetMetadata() const final;
 
   // nested types ----------------------------------------------------
@@ -9311,11 +9259,9 @@ class PROTOBUF_EXPORT DescriptorProto_ExtensionRange final :
   protected:
   explicit DescriptorProto_ExtensionRange(::google::protobuf::Arena* arena);
   DescriptorProto_ExtensionRange(::google::protobuf::Arena* arena, const DescriptorProto_ExtensionRange& from);
+  const ::google::protobuf::MessageLite::ClassData* GetClassData() const final;
   public:
 
-  static const ClassData _class_data_;
-  const ::google::protobuf::Message::ClassData*GetClassData() const final;
-
   ::google::protobuf::Metadata GetMetadata() const final;
 
   // nested types ----------------------------------------------------
@@ -9518,11 +9464,9 @@ class PROTOBUF_EXPORT ServiceDescriptorProto final :
   protected:
   explicit ServiceDescriptorProto(::google::protobuf::Arena* arena);
   ServiceDescriptorProto(::google::protobuf::Arena* arena, const ServiceDescriptorProto& from);
+  const ::google::protobuf::MessageLite::ClassData* GetClassData() const final;
   public:
 
-  static const ClassData _class_data_;
-  const ::google::protobuf::Message::ClassData*GetClassData() const final;
-
   ::google::protobuf::Metadata GetMetadata() const final;
 
   // nested types ----------------------------------------------------
@@ -9738,11 +9682,9 @@ class PROTOBUF_EXPORT EnumDescriptorProto final :
   protected:
   explicit EnumDescriptorProto(::google::protobuf::Arena* arena);
   EnumDescriptorProto(::google::protobuf::Arena* arena, const EnumDescriptorProto& from);
+  const ::google::protobuf::MessageLite::ClassData* GetClassData() const final;
   public:
 
-  static const ClassData _class_data_;
-  const ::google::protobuf::Message::ClassData*GetClassData() const final;
-
   ::google::protobuf::Metadata GetMetadata() const final;
 
   // nested types ----------------------------------------------------
@@ -10010,11 +9952,9 @@ class PROTOBUF_EXPORT DescriptorProto final :
   protected:
   explicit DescriptorProto(::google::protobuf::Arena* arena);
   DescriptorProto(::google::protobuf::Arena* arena, const DescriptorProto& from);
+  const ::google::protobuf::MessageLite::ClassData* GetClassData() const final;
   public:
 
-  static const ClassData _class_data_;
-  const ::google::protobuf::Message::ClassData*GetClassData() const final;
-
   ::google::protobuf::Metadata GetMetadata() const final;
 
   // nested types ----------------------------------------------------
@@ -10383,11 +10323,9 @@ class PROTOBUF_EXPORT FileDescriptorProto final :
   protected:
   explicit FileDescriptorProto(::google::protobuf::Arena* arena);
   FileDescriptorProto(::google::protobuf::Arena* arena, const FileDescriptorProto& from);
+  const ::google::protobuf::MessageLite::ClassData* GetClassData() const final;
   public:
 
-  static const ClassData _class_data_;
-  const ::google::protobuf::Message::ClassData*GetClassData() const final;
-
   ::google::protobuf::Metadata GetMetadata() const final;
 
   // nested types ----------------------------------------------------
@@ -10801,11 +10739,9 @@ class PROTOBUF_EXPORT FileDescriptorSet final :
   protected:
   explicit FileDescriptorSet(::google::protobuf::Arena* arena);
   FileDescriptorSet(::google::protobuf::Arena* arena, const FileDescriptorSet& from);
+  const ::google::protobuf::MessageLite::ClassData* GetClassData() const final;
   public:
 
-  static const ClassData _class_data_;
-  const ::google::protobuf::Message::ClassData*GetClassData() const final;
-
   ::google::protobuf::Metadata GetMetadata() const final;
 
   // nested types ----------------------------------------------------

src/google/protobuf/generated_message_bases.cc

@@ -7,6 +7,7 @@
 
 #include "google/protobuf/generated_message_bases.h"
 
+#include "google/protobuf/generated_message_reflection.h"
 #include "google/protobuf/io/coded_stream.h"
 #include "google/protobuf/io/zero_copy_stream_impl.h"
 #include "google/protobuf/parse_context.h"
@@ -95,7 +96,11 @@ void ZeroFieldsBase::InternalSwap(ZeroFieldsBase* other) {
 }
 
 const Message::ClassData* ZeroFieldsBase::GetClassData() const {
-  static constexpr ClassData data = {&MergeImpl};
+  static constexpr ClassData data = {
+      &MergeImpl,
+      nullptr,
+      &kDescriptorMethods,
+  };
   return &data;
 }
 

src/google/protobuf/implicit_weak_message.h

@@ -56,7 +56,14 @@ class PROTOBUF_EXPORT ImplicitWeakMessage : public MessageLite {
 
   static const ImplicitWeakMessage* default_instance();
 
-  std::string GetTypeName() const override { return ""; }
+  const ClassData* GetClassData() const final {
+    struct Data {
+      ClassData header;
+      char name[1];
+    };
+    static constexpr Data data = {{}, ""};
+    return &data.header;
+  }
 
   MessageLite* New(Arena* arena) const override {
     return Arena::CreateMessage<ImplicitWeakMessage>(arena);

src/google/protobuf/message.cc

@@ -58,6 +58,10 @@ using internal::ReflectionOps;
 using internal::WireFormat;
 using internal::WireFormatLite;
 
+void Message::MergeImpl(Message& to, const Message& from) {
+  ReflectionOps::Merge(from, &to);
+}
+
 void Message::MergeFrom(const Message& from) {
   auto* class_to = GetClassData();
   auto* class_from = from.GetClassData();
@@ -70,6 +74,15 @@ void Message::MergeFrom(const Message& from) {
   merge_to_from(*this, from);
 }
 
+const MessageLite::ClassData* Message::GetClassData() const {
+  static constexpr ClassData data = {
+      &MergeImpl,
+      nullptr,
+      &kDescriptorMethods,
+  };
+  return &data;
+}
+
 void Message::CheckTypeAndMergeFrom(const MessageLite& other) {
   MergeFrom(*DownCast<const Message*>(&other));
 }
@@ -99,10 +112,6 @@ void Message::CopyFrom(const Message& from) {
   }
 }
 
-std::string Message::GetTypeName() const {
-  return GetDescriptor()->full_name();
-}
-
 void Message::Clear() { ReflectionOps::Clear(this); }
 
 bool Message::IsInitialized() const {
@@ -182,6 +191,14 @@ size_t Message::SpaceUsedLong() const {
   return GetReflection()->SpaceUsedLong(*this);
 }
 
+static std::string GetTypeNameImpl(const MessageLite& msg) {
+  return DownCast<const Message&>(msg).GetDescriptor()->full_name();
+}
+
+constexpr MessageLite::DescriptorMethods Message::kDescriptorMethods = {
+    GetTypeNameImpl,
+};
+
 namespace internal {
 void* CreateSplitMessageGeneric(Arena* arena, const void* default_split,
                                 size_t size, const void* message,

src/google/protobuf/message.h

@@ -330,7 +330,6 @@ class PROTOBUF_EXPORT Message : public MessageLite {
   // These methods are pure-virtual in MessageLite, but Message provides
   // reflection-based default implementations.
 
-  std::string GetTypeName() const override;
   void Clear() override;
 
   // Returns whether all required fields have been set. Note that required
@@ -370,6 +369,15 @@ class PROTOBUF_EXPORT Message : public MessageLite {
   size_t MaybeComputeUnknownFieldsSize(size_t total_size,
                                        internal::CachedSize* cached_size) const;
 
+  // Reflection based version for reflection based types.
+  static void MergeImpl(Message& to, const Message& from);
+
+  static const DescriptorMethods kDescriptorMethods;
+
+  // Default implementation using reflection. Avoids bloat in MapEntry.
+  // Generated types will make their own.
+  const ClassData* GetClassData() const override;
+
 };
 
 namespace internal {

src/google/protobuf/message_lite.cc

@@ -44,18 +44,29 @@
 namespace google {
 namespace protobuf {
 
+std::string MessageLite::GetTypeName() const {
+  auto* data = GetClassData();
+  ABSL_DCHECK(data != nullptr);
+
+  if (data->descriptor_methods != nullptr) {
+    // For !LITE messages, we use the descriptor method function.
+    return data->descriptor_methods->get_type_name(*this);
+  }
+
+  // For LITE messages, the type name is a char[] just beyond ClassData.
+  return reinterpret_cast<const char*>(data) + sizeof(ClassData);
+}
+
 void MessageLite::OnDemandRegisterArenaDtor(Arena* arena) {
   if (arena == nullptr) return;
   auto* data = GetClassData();
-  if (data != nullptr && data->on_demand_register_arena_dtor != nullptr) {
+  ABSL_DCHECK(data != nullptr);
+
+  if (data->on_demand_register_arena_dtor != nullptr) {
     data->on_demand_register_arena_dtor(*this, *arena);
   }
 }
 
-const MessageLite::ClassData* MessageLite::GetClassData() const {
-  return nullptr;
-}
-
 std::string MessageLite::InitializationErrorString() const {
   return "(cannot determine missing fields for lite message)";
 }

src/google/protobuf/message_lite.h

@@ -211,7 +211,7 @@ class PROTOBUF_EXPORT MessageLite {
   // Basic Operations ------------------------------------------------
 
   // Get the name of this message type, e.g. "foo.bar.BazProto".
-  virtual std::string GetTypeName() const = 0;
+  std::string GetTypeName() const;
 
   // Construct a new instance of the same type.  Ownership is passed to the
   // caller.
@@ -518,12 +518,21 @@ class PROTOBUF_EXPORT MessageLite {
   // of this message or its internal memory could be changed.
   Arena* GetOwningArena() const { return _internal_metadata_.arena(); }
 
+  // We use a secondary vtable for descriptor based methods. This way ClassData
+  // does not growth with the number of descriptor methods. This avoids extra
+  // costs in MessageLite.
+  struct DescriptorMethods {
+    std::string (*get_type_name)(const MessageLite&);
+  };
   struct ClassData {
     // Note: The order of arguments in the functions is chosen so that it has
     // the same ABI as the member function that calls them. Eg the `this`
     // pointer becomes the first argument in the free function.
     void (*merge_to_from)(Message& to, const Message& from_msg);
     void (*on_demand_register_arena_dtor)(MessageLite& msg, Arena& arena);
+    // LITE objects (ie !descriptor_methods) collocate their name as a
+    // char[] just beyond the ClassData.
+    const DescriptorMethods* descriptor_methods;
   };
 
   // GetClassData() returns a pointer to a ClassData struct which
@@ -531,9 +540,9 @@ class PROTOBUF_EXPORT MessageLite {
   // property is used in order to quickly determine whether two messages are
   // of the same type.
   //
-  // This is a work in progress. Currently only SPEED messages return an
+  // This is a work in progress. There are still some types (eg MapEntry) that
-  // instance. In the future all message types will return one.
+  // return a default table instead of a unique one.
-  virtual const ClassData* GetClassData() const;
+  virtual const ClassData* GetClassData() const = 0;
 
   internal::InternalMetadata _internal_metadata_;