Optimize proto2::MoveField for lazy extensions.

PiperOrigin-RevId: 826342531

Author: protobuf-github-bot

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

@@ -2395,6 +2395,7 @@ void MessageGenerator::GenerateClassDefinition(io::Printer* p) {
 
           friend class $pb$::MessageLite;
           friend class $pb$::Arena;
+          friend $pbi$::PrivateAccess;
           template <typename T>
           friend class $pb$::Arena::InternalHelper;
           using InternalArenaConstructable_ = void;

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

@@ -625,6 +625,21 @@ class PROTOBUF_EXPORT ExtensionSet {
   }
 #endif
 
+  // Moves an extension from one ExtensionSet to another.
+  //
+  // If the source extension does not exist, then destination extension is
+  // freed (non-arena allocated) or cleared (arena allocated).
+  //
+  // If the destination extension already exists, it is overwritten.
+  // If the destination extension does not exist, it is created.
+  void MoveExtension(Arena* arena, int dst_number, ExtensionSet& src,
+                     int src_number);
+
+  bool IsLazy(int number) {
+    Extension* extension = FindOrNull(number);
+    return extension != nullptr && extension->is_lazy;
+  }
+
  private:
   template <typename Type>
   friend class PrimitiveTypeTraits;

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

@@ -14,8 +14,11 @@
 
 #include <cstddef>
 #include <cstdint>
+#include <cstring>
 #include <initializer_list>
 #include <string>
+#include <tuple>
+#include <utility>
 #include <variant>
 #include <vector>