`MapEntry` no longer needs `Derived` template parameter.

Removed some dead code from `MapField`.

PiperOrigin-RevId: 669361776

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

@@ -1368,12 +1368,12 @@ void MessageGenerator::GenerateMapEntryClassDefinition(io::Printer* p) {
       R"cc(
         class $classname$ final
             : public ::$proto_ns$::internal::MapEntry<
-                  $classname$, $key_cpp$, $val_cpp$,
+                  $key_cpp$, $val_cpp$,
                   ::$proto_ns$::internal::WireFormatLite::$key_wire_type$,
                   ::$proto_ns$::internal::WireFormatLite::$val_wire_type$> {
          public:
           using SuperType = ::$proto_ns$::internal::MapEntry<
-              $classname$, $key_cpp$, $val_cpp$,
+              $key_cpp$, $val_cpp$,
               ::$proto_ns$::internal::WireFormatLite::$key_wire_type$,
               ::$proto_ns$::internal::WireFormatLite::$val_wire_type$>;
           $classname$();

src/google/protobuf/map_entry.h

@@ -30,18 +30,9 @@
 
 namespace google {
 namespace protobuf {
+
 class Arena;
-namespace internal {
-template <typename Derived, typename Key, typename Value,
-          WireFormatLite::FieldType kKeyFieldType,
-          WireFormatLite::FieldType kValueFieldType>
-class MapField;
-}
-}  // namespace protobuf
-}  // namespace google
 
-namespace google {
-namespace protobuf {
 namespace internal {
 
 // MapEntry is the returned google::protobuf::Message when calling AddMessage of
@@ -70,8 +61,7 @@ namespace internal {
 // The in-memory types of primitive types can be inferred from its proto type,
 // while we need to explicitly specify the cpp type if proto type is
 // TYPE_MESSAGE to infer the in-memory type.
-template <typename Derived, typename Key, typename Value,
-          WireFormatLite::FieldType kKeyFieldType,
+template <typename Key, typename Value, WireFormatLite::FieldType kKeyFieldType,
           WireFormatLite::FieldType kValueFieldType>
 class MapEntry : public Message {
   // Provide utilities to parse/serialize key/value.  Provide utilities to
@@ -119,11 +109,9 @@ class MapEntry : public Message {
   } _impl_;
 };
 
-template <typename Derived, typename Key, typename Value,
-          WireFormatLite::FieldType kKeyFieldType,
+template <typename Key, typename Value, WireFormatLite::FieldType kKeyFieldType,
           WireFormatLite::FieldType kValueFieldType>
-struct MapEntry<Derived, Key, Value, kKeyFieldType,
-                kValueFieldType>::_Internal {
+struct MapEntry<Key, Value, kKeyFieldType, kValueFieldType>::_Internal {
   static constexpr ::int32_t kHasBitsOffset =
       8 * PROTOBUF_FIELD_OFFSET(MapEntry, _impl_._has_bits_);
 };

src/google/protobuf/map_field.h

@@ -26,7 +26,6 @@
 #include "google/protobuf/generated_message_util.h"
 #include "google/protobuf/internal_visibility.h"
 #include "google/protobuf/map.h"
-#include "google/protobuf/map_entry.h"
 #include "google/protobuf/map_field_lite.h"
 #include "google/protobuf/map_type_handler.h"
 #include "google/protobuf/message.h"
@@ -656,9 +655,6 @@ class MapField final : public TypeDefinedMapFieldBase<Key, T> {
   typedef MapTypeHandler<kKeyFieldType_, Key> KeyTypeHandler;
   typedef MapTypeHandler<kValueFieldType_, T> ValueTypeHandler;
 
-  // Define message type for internal repeated field.
-  typedef Derived EntryType;
-
  public:
   typedef Map<Key, T> MapType;
   static constexpr WireFormatLite::FieldType kKeyFieldType = kKeyFieldType_;
@@ -678,12 +674,6 @@ class MapField final : public TypeDefinedMapFieldBase<Key, T> {
     this->MergeFromImpl(*this, from);
   }
 
-  // Used in the implementation of parsing. Caller should take the ownership iff
-  // arena_ is nullptr.
-  EntryType* NewEntry() const {
-    return Arena::Create<EntryType>(this->arena());
-  }
-
  private:
   typedef void InternalArenaConstructable_;
   typedef void DestructorSkippable_;
@@ -712,14 +702,6 @@ bool AllAreInitialized(const TypeDefinedMapFieldBase<Key, T>& field) {
   return true;
 }
 
-template <typename T, typename Key, typename Value,
-          WireFormatLite::FieldType kKeyFieldType,
-          WireFormatLite::FieldType kValueFieldType>
-struct MapEntryToMapField<
-    MapEntry<T, Key, Value, kKeyFieldType, kValueFieldType>> {
-  typedef MapField<T, Key, Value, kKeyFieldType, kValueFieldType> MapFieldType;
-};
-
 class PROTOBUF_EXPORT DynamicMapField final
     : public TypeDefinedMapFieldBase<MapKey, MapValueRef> {
  public:

src/google/protobuf/map_test.inc

@@ -2322,7 +2322,7 @@ TEST_F(MapFieldReflectionTest, UninitializedEntry) {
 }
 
 class MyMapEntry
-    : public internal::MapEntry<MyMapEntry, ::int32_t, ::int32_t,
+    : public internal::MapEntry<::int32_t, ::int32_t,
                                 internal::WireFormatLite::TYPE_INT32,
                                 internal::WireFormatLite::TYPE_INT32> {
  public: