diff --git a/src/google/protobuf/compiler/cpp/message.cc b/src/google/protobuf/compiler/cpp/message.cc
index 650cd46f50195..8a202cb5c488c 100644
--- a/src/google/protobuf/compiler/cpp/message.cc
+++ b/src/google/protobuf/compiler/cpp/message.cc
@@ -1473,7 +1473,8 @@ void MessageGenerator::GenerateImplDefinition(io::Printer* p) {
           inline explicit Impl_($pbi$::InternalVisibility visibility,
                                 ::$proto_ns$::Arena* arena);
           inline explicit Impl_($pbi$::InternalVisibility visibility,
-                                ::$proto_ns$::Arena* arena, const Impl_& from);
+                                ::$proto_ns$::Arena* arena, const Impl_& from,
+                                const $classname$& from_msg);
           //~ Members assumed to align to 8 bytes:
           $extension_set$;
           $tracker$;
@@ -2993,7 +2994,7 @@ void MessageGenerator::GenerateArenaEnabledCopyConstructor(io::Printer* p) {
         R"cc(
           inline PROTOBUF_NDEBUG_INLINE $classname$::Impl_::Impl_(
               $pbi$::InternalVisibility visibility, ::$proto_ns$::Arena* arena,
-              const Impl_& from)
+              const Impl_& from, const $classtype$& from_msg)
               //~
               $init$ {}
         )cc");
@@ -3003,7 +3004,7 @@ void MessageGenerator::GenerateArenaEnabledCopyConstructor(io::Printer* p) {
   auto copy_construct_impl = [&] {
     if (!HasSimpleBaseClass(descriptor_, options_)) {
       p->Emit(R"cc(
-        new (&_impl_) Impl_(internal_visibility(), arena, from._impl_);
+        new (&_impl_) Impl_(internal_visibility(), arena, from._impl_, from);
       )cc");
     }
   };
diff --git a/src/google/protobuf/compiler/java/java_features.pb.h b/src/google/protobuf/compiler/java/java_features.pb.h
index d41c7b146ca82..28d2f9ec37402 100644
--- a/src/google/protobuf/compiler/java/java_features.pb.h
+++ b/src/google/protobuf/compiler/java/java_features.pb.h
@@ -291,7 +291,8 @@ class PROTOC_EXPORT JavaFeatures final : public ::google::protobuf::Message
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
                           ::google::protobuf::Arena* arena);
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
-                          ::google::protobuf::Arena* arena, const Impl_& from);
+                          ::google::protobuf::Arena* arena, const Impl_& from,
+                          const JavaFeatures& from_msg);
     ::google::protobuf::internal::HasBits<1> _has_bits_;
     mutable ::google::protobuf::internal::CachedSize _cached_size_;
     bool legacy_closed_enum_;
diff --git a/src/google/protobuf/compiler/plugin.pb.cc b/src/google/protobuf/compiler/plugin.pb.cc
index aef397153090c..7ab44b6615abb 100644
--- a/src/google/protobuf/compiler/plugin.pb.cc
+++ b/src/google/protobuf/compiler/plugin.pb.cc
@@ -308,7 +308,7 @@ Version::Version(::google::protobuf::Arena* arena)
 }
 inline PROTOBUF_NDEBUG_INLINE Version::Impl_::Impl_(
     ::google::protobuf::internal::InternalVisibility visibility, ::google::protobuf::Arena* arena,
-    const Impl_& from)
+    const Impl_& from, const ::google::protobuf::compiler::Version& from_msg)
       : _has_bits_{from._has_bits_},
         _cached_size_{0},
         suffix_(arena, from.suffix_) {}
@@ -321,7 +321,7 @@ Version::Version(
   (void)_this;
   _internal_metadata_.MergeFrom<::google::protobuf::UnknownFieldSet>(
       from._internal_metadata_);
-  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_);
+  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_, from);
   ::memcpy(reinterpret_cast<char *>(&_impl_) +
                offsetof(Impl_, major_),
            reinterpret_cast<const char *>(&from._impl_) +
@@ -621,7 +621,7 @@ CodeGeneratorRequest::CodeGeneratorRequest(::google::protobuf::Arena* arena)
 }
 inline PROTOBUF_NDEBUG_INLINE CodeGeneratorRequest::Impl_::Impl_(
     ::google::protobuf::internal::InternalVisibility visibility, ::google::protobuf::Arena* arena,
-    const Impl_& from)
+    const Impl_& from, const ::google::protobuf::compiler::CodeGeneratorRequest& from_msg)
       : _has_bits_{from._has_bits_},
         _cached_size_{0},
         file_to_generate_{visibility, arena, from.file_to_generate_},
@@ -637,7 +637,7 @@ CodeGeneratorRequest::CodeGeneratorRequest(
   (void)_this;
   _internal_metadata_.MergeFrom<::google::protobuf::UnknownFieldSet>(
       from._internal_metadata_);
-  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_);
+  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_, from);
   ::uint32_t cached_has_bits = _impl_._has_bits_[0];
   _impl_.compiler_version_ = (cached_has_bits & 0x00000002u) ? ::google::protobuf::Message::CopyConstruct<::google::protobuf::compiler::Version>(
                               arena, *from._impl_.compiler_version_)
@@ -969,7 +969,7 @@ CodeGeneratorResponse_File::CodeGeneratorResponse_File(::google::protobuf::Arena
 }
 inline PROTOBUF_NDEBUG_INLINE CodeGeneratorResponse_File::Impl_::Impl_(
     ::google::protobuf::internal::InternalVisibility visibility, ::google::protobuf::Arena* arena,
-    const Impl_& from)
+    const Impl_& from, const ::google::protobuf::compiler::CodeGeneratorResponse_File& from_msg)
       : _has_bits_{from._has_bits_},
         _cached_size_{0},
         name_(arena, from.name_),
@@ -984,7 +984,7 @@ CodeGeneratorResponse_File::CodeGeneratorResponse_File(
   (void)_this;
   _internal_metadata_.MergeFrom<::google::protobuf::UnknownFieldSet>(
       from._internal_metadata_);
-  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_);
+  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_, from);
   ::uint32_t cached_has_bits = _impl_._has_bits_[0];
   _impl_.generated_code_info_ = (cached_has_bits & 0x00000008u) ? ::google::protobuf::Message::CopyConstruct<::google::protobuf::GeneratedCodeInfo>(
                               arena, *from._impl_.generated_code_info_)
@@ -1287,7 +1287,7 @@ CodeGeneratorResponse::CodeGeneratorResponse(::google::protobuf::Arena* arena)
 }
 inline PROTOBUF_NDEBUG_INLINE CodeGeneratorResponse::Impl_::Impl_(
     ::google::protobuf::internal::InternalVisibility visibility, ::google::protobuf::Arena* arena,
-    const Impl_& from)
+    const Impl_& from, const ::google::protobuf::compiler::CodeGeneratorResponse& from_msg)
       : _has_bits_{from._has_bits_},
         _cached_size_{0},
         file_{visibility, arena, from.file_},
@@ -1301,7 +1301,7 @@ CodeGeneratorResponse::CodeGeneratorResponse(
   (void)_this;
   _internal_metadata_.MergeFrom<::google::protobuf::UnknownFieldSet>(
       from._internal_metadata_);
-  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_);
+  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_, from);
   ::memcpy(reinterpret_cast<char *>(&_impl_) +
                offsetof(Impl_, supported_features_),
            reinterpret_cast<const char *>(&from._impl_) +
diff --git a/src/google/protobuf/compiler/plugin.pb.h b/src/google/protobuf/compiler/plugin.pb.h
index a6a7a5c522a9c..43f0af12092b5 100644
--- a/src/google/protobuf/compiler/plugin.pb.h
+++ b/src/google/protobuf/compiler/plugin.pb.h
@@ -318,7 +318,8 @@ class PROTOC_EXPORT Version final : public ::google::protobuf::Message
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
                           ::google::protobuf::Arena* arena);
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
-                          ::google::protobuf::Arena* arena, const Impl_& from);
+                          ::google::protobuf::Arena* arena, const Impl_& from,
+                          const Version& from_msg);
     ::google::protobuf::internal::HasBits<1> _has_bits_;
     mutable ::google::protobuf::internal::CachedSize _cached_size_;
     ::google::protobuf::internal::ArenaStringPtr suffix_;
@@ -551,7 +552,8 @@ class PROTOC_EXPORT CodeGeneratorResponse_File final : public ::google::protobuf
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
                           ::google::protobuf::Arena* arena);
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
-                          ::google::protobuf::Arena* arena, const Impl_& from);
+                          ::google::protobuf::Arena* arena, const Impl_& from,
+                          const CodeGeneratorResponse_File& from_msg);
     ::google::protobuf::internal::HasBits<1> _has_bits_;
     mutable ::google::protobuf::internal::CachedSize _cached_size_;
     ::google::protobuf::internal::ArenaStringPtr name_;
@@ -807,7 +809,8 @@ class PROTOC_EXPORT CodeGeneratorResponse final : public ::google::protobuf::Mes
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
                           ::google::protobuf::Arena* arena);
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
-                          ::google::protobuf::Arena* arena, const Impl_& from);
+                          ::google::protobuf::Arena* arena, const Impl_& from,
+                          const CodeGeneratorResponse& from_msg);
     ::google::protobuf::internal::HasBits<1> _has_bits_;
     mutable ::google::protobuf::internal::CachedSize _cached_size_;
     ::google::protobuf::RepeatedPtrField< ::google::protobuf::compiler::CodeGeneratorResponse_File > file_;
@@ -1070,7 +1073,8 @@ class PROTOC_EXPORT CodeGeneratorRequest final : public ::google::protobuf::Mess
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
                           ::google::protobuf::Arena* arena);
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
-                          ::google::protobuf::Arena* arena, const Impl_& from);
+                          ::google::protobuf::Arena* arena, const Impl_& from,
+                          const CodeGeneratorRequest& from_msg);
     ::google::protobuf::internal::HasBits<1> _has_bits_;
     mutable ::google::protobuf::internal::CachedSize _cached_size_;
     ::google::protobuf::RepeatedPtrField<std::string> file_to_generate_;
diff --git a/src/google/protobuf/cpp_features.pb.h b/src/google/protobuf/cpp_features.pb.h
index 289625b15855a..01b2446212081 100644
--- a/src/google/protobuf/cpp_features.pb.h
+++ b/src/google/protobuf/cpp_features.pb.h
@@ -293,7 +293,8 @@ class PROTOBUF_EXPORT CppFeatures final : public ::google::protobuf::Message
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
                           ::google::protobuf::Arena* arena);
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
-                          ::google::protobuf::Arena* arena, const Impl_& from);
+                          ::google::protobuf::Arena* arena, const Impl_& from,
+                          const CppFeatures& from_msg);
     ::google::protobuf::internal::HasBits<1> _has_bits_;
     mutable ::google::protobuf::internal::CachedSize _cached_size_;
     bool legacy_closed_enum_;
diff --git a/src/google/protobuf/descriptor.pb.cc b/src/google/protobuf/descriptor.pb.cc
index 4573d670899b6..edba5596c0b68 100644
--- a/src/google/protobuf/descriptor.pb.cc
+++ b/src/google/protobuf/descriptor.pb.cc
@@ -2344,7 +2344,7 @@ FileDescriptorSet::FileDescriptorSet(::google::protobuf::Arena* arena)
 }
 inline PROTOBUF_NDEBUG_INLINE FileDescriptorSet::Impl_::Impl_(
     ::google::protobuf::internal::InternalVisibility visibility, ::google::protobuf::Arena* arena,
-    const Impl_& from)
+    const Impl_& from, const ::google::protobuf::FileDescriptorSet& from_msg)
       : file_{visibility, arena, from.file_},
         _cached_size_{0} {}
 
@@ -2356,7 +2356,7 @@ FileDescriptorSet::FileDescriptorSet(
   (void)_this;
   _internal_metadata_.MergeFrom<::google::protobuf::UnknownFieldSet>(
       from._internal_metadata_);
-  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_);
+  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_, from);
 
   // @@protoc_insertion_point(copy_constructor:google.protobuf.FileDescriptorSet)
 }
@@ -2540,7 +2540,7 @@ FileDescriptorProto::FileDescriptorProto(::google::protobuf::Arena* arena)
 }
 inline PROTOBUF_NDEBUG_INLINE FileDescriptorProto::Impl_::Impl_(
     ::google::protobuf::internal::InternalVisibility visibility, ::google::protobuf::Arena* arena,
-    const Impl_& from)
+    const Impl_& from, const ::google::protobuf::FileDescriptorProto& from_msg)
       : _has_bits_{from._has_bits_},
         _cached_size_{0},
         dependency_{visibility, arena, from.dependency_},
@@ -2562,7 +2562,7 @@ FileDescriptorProto::FileDescriptorProto(
   (void)_this;
   _internal_metadata_.MergeFrom<::google::protobuf::UnknownFieldSet>(
       from._internal_metadata_);
-  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_);
+  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_, from);
   ::uint32_t cached_has_bits = _impl_._has_bits_[0];
   _impl_.options_ = (cached_has_bits & 0x00000008u) ? ::google::protobuf::Message::CopyConstruct<::google::protobuf::FileOptions>(
                               arena, *from._impl_.options_)
@@ -3136,7 +3136,7 @@ DescriptorProto_ExtensionRange::DescriptorProto_ExtensionRange(::google::protobu
 }
 inline PROTOBUF_NDEBUG_INLINE DescriptorProto_ExtensionRange::Impl_::Impl_(
     ::google::protobuf::internal::InternalVisibility visibility, ::google::protobuf::Arena* arena,
-    const Impl_& from)
+    const Impl_& from, const ::google::protobuf::DescriptorProto_ExtensionRange& from_msg)
       : _has_bits_{from._has_bits_},
         _cached_size_{0} {}
 
@@ -3148,7 +3148,7 @@ DescriptorProto_ExtensionRange::DescriptorProto_ExtensionRange(
   (void)_this;
   _internal_metadata_.MergeFrom<::google::protobuf::UnknownFieldSet>(
       from._internal_metadata_);
-  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_);
+  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_, from);
   ::uint32_t cached_has_bits = _impl_._has_bits_[0];
   _impl_.options_ = (cached_has_bits & 0x00000001u) ? ::google::protobuf::Message::CopyConstruct<::google::protobuf::ExtensionRangeOptions>(
                               arena, *from._impl_.options_)
@@ -3651,7 +3651,7 @@ DescriptorProto::DescriptorProto(::google::protobuf::Arena* arena)
 }
 inline PROTOBUF_NDEBUG_INLINE DescriptorProto::Impl_::Impl_(
     ::google::protobuf::internal::InternalVisibility visibility, ::google::protobuf::Arena* arena,
-    const Impl_& from)
+    const Impl_& from, const ::google::protobuf::DescriptorProto& from_msg)
       : _has_bits_{from._has_bits_},
         _cached_size_{0},
         field_{visibility, arena, from.field_},
@@ -3672,7 +3672,7 @@ DescriptorProto::DescriptorProto(
   (void)_this;
   _internal_metadata_.MergeFrom<::google::protobuf::UnknownFieldSet>(
       from._internal_metadata_);
-  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_);
+  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_, from);
   ::uint32_t cached_has_bits = _impl_._has_bits_[0];
   _impl_.options_ = (cached_has_bits & 0x00000002u) ? ::google::protobuf::Message::CopyConstruct<::google::protobuf::MessageOptions>(
                               arena, *from._impl_.options_)
@@ -4150,7 +4150,7 @@ ExtensionRangeOptions_Declaration::ExtensionRangeOptions_Declaration(::google::p
 }
 inline PROTOBUF_NDEBUG_INLINE ExtensionRangeOptions_Declaration::Impl_::Impl_(
     ::google::protobuf::internal::InternalVisibility visibility, ::google::protobuf::Arena* arena,
-    const Impl_& from)
+    const Impl_& from, const ::google::protobuf::ExtensionRangeOptions_Declaration& from_msg)
       : _has_bits_{from._has_bits_},
         _cached_size_{0},
         full_name_(arena, from.full_name_),
@@ -4164,7 +4164,7 @@ ExtensionRangeOptions_Declaration::ExtensionRangeOptions_Declaration(
   (void)_this;
   _internal_metadata_.MergeFrom<::google::protobuf::UnknownFieldSet>(
       from._internal_metadata_);
-  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_);
+  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_, from);
   ::memcpy(reinterpret_cast<char *>(&_impl_) +
                offsetof(Impl_, number_),
            reinterpret_cast<const char *>(&from._impl_) +
@@ -4488,7 +4488,7 @@ ExtensionRangeOptions::ExtensionRangeOptions(::google::protobuf::Arena* arena)
 }
 inline PROTOBUF_NDEBUG_INLINE ExtensionRangeOptions::Impl_::Impl_(
     ::google::protobuf::internal::InternalVisibility visibility, ::google::protobuf::Arena* arena,
-    const Impl_& from)
+    const Impl_& from, const ::google::protobuf::ExtensionRangeOptions& from_msg)
       : _extensions_{visibility, arena},
         _has_bits_{from._has_bits_},
         _cached_size_{0},
@@ -4503,7 +4503,7 @@ ExtensionRangeOptions::ExtensionRangeOptions(
   (void)_this;
   _internal_metadata_.MergeFrom<::google::protobuf::UnknownFieldSet>(
       from._internal_metadata_);
-  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_);
+  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_, from);
   _impl_._extensions_.MergeFrom(this, from._impl_._extensions_);
   ::uint32_t cached_has_bits = _impl_._has_bits_[0];
   _impl_.features_ = (cached_has_bits & 0x00000001u) ? ::google::protobuf::Message::CopyConstruct<::google::protobuf::FeatureSet>(
@@ -4820,7 +4820,7 @@ FieldDescriptorProto::FieldDescriptorProto(::google::protobuf::Arena* arena)
 }
 inline PROTOBUF_NDEBUG_INLINE FieldDescriptorProto::Impl_::Impl_(
     ::google::protobuf::internal::InternalVisibility visibility, ::google::protobuf::Arena* arena,
-    const Impl_& from)
+    const Impl_& from, const ::google::protobuf::FieldDescriptorProto& from_msg)
       : _has_bits_{from._has_bits_},
         _cached_size_{0},
         name_(arena, from.name_),
@@ -4837,7 +4837,7 @@ FieldDescriptorProto::FieldDescriptorProto(
   (void)_this;
   _internal_metadata_.MergeFrom<::google::protobuf::UnknownFieldSet>(
       from._internal_metadata_);
-  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_);
+  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_, from);
   ::uint32_t cached_has_bits = _impl_._has_bits_[0];
   _impl_.options_ = (cached_has_bits & 0x00000020u) ? ::google::protobuf::Message::CopyConstruct<::google::protobuf::FieldOptions>(
                               arena, *from._impl_.options_)
@@ -5349,7 +5349,7 @@ OneofDescriptorProto::OneofDescriptorProto(::google::protobuf::Arena* arena)
 }
 inline PROTOBUF_NDEBUG_INLINE OneofDescriptorProto::Impl_::Impl_(
     ::google::protobuf::internal::InternalVisibility visibility, ::google::protobuf::Arena* arena,
-    const Impl_& from)
+    const Impl_& from, const ::google::protobuf::OneofDescriptorProto& from_msg)
       : _has_bits_{from._has_bits_},
         _cached_size_{0},
         name_(arena, from.name_) {}
@@ -5362,7 +5362,7 @@ OneofDescriptorProto::OneofDescriptorProto(
   (void)_this;
   _internal_metadata_.MergeFrom<::google::protobuf::UnknownFieldSet>(
       from._internal_metadata_);
-  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_);
+  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_, from);
   ::uint32_t cached_has_bits = _impl_._has_bits_[0];
   _impl_.options_ = (cached_has_bits & 0x00000002u) ? ::google::protobuf::Message::CopyConstruct<::google::protobuf::OneofOptions>(
                               arena, *from._impl_.options_)
@@ -5834,7 +5834,7 @@ EnumDescriptorProto::EnumDescriptorProto(::google::protobuf::Arena* arena)
 }
 inline PROTOBUF_NDEBUG_INLINE EnumDescriptorProto::Impl_::Impl_(
     ::google::protobuf::internal::InternalVisibility visibility, ::google::protobuf::Arena* arena,
-    const Impl_& from)
+    const Impl_& from, const ::google::protobuf::EnumDescriptorProto& from_msg)
       : _has_bits_{from._has_bits_},
         _cached_size_{0},
         value_{visibility, arena, from.value_},
@@ -5850,7 +5850,7 @@ EnumDescriptorProto::EnumDescriptorProto(
   (void)_this;
   _internal_metadata_.MergeFrom<::google::protobuf::UnknownFieldSet>(
       from._internal_metadata_);
-  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_);
+  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_, from);
   ::uint32_t cached_has_bits = _impl_._has_bits_[0];
   _impl_.options_ = (cached_has_bits & 0x00000002u) ? ::google::protobuf::Message::CopyConstruct<::google::protobuf::EnumOptions>(
                               arena, *from._impl_.options_)
@@ -6180,7 +6180,7 @@ EnumValueDescriptorProto::EnumValueDescriptorProto(::google::protobuf::Arena* ar
 }
 inline PROTOBUF_NDEBUG_INLINE EnumValueDescriptorProto::Impl_::Impl_(
     ::google::protobuf::internal::InternalVisibility visibility, ::google::protobuf::Arena* arena,
-    const Impl_& from)
+    const Impl_& from, const ::google::protobuf::EnumValueDescriptorProto& from_msg)
       : _has_bits_{from._has_bits_},
         _cached_size_{0},
         name_(arena, from.name_) {}
@@ -6193,7 +6193,7 @@ EnumValueDescriptorProto::EnumValueDescriptorProto(
   (void)_this;
   _internal_metadata_.MergeFrom<::google::protobuf::UnknownFieldSet>(
       from._internal_metadata_);
-  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_);
+  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_, from);
   ::uint32_t cached_has_bits = _impl_._has_bits_[0];
   _impl_.options_ = (cached_has_bits & 0x00000002u) ? ::google::protobuf::Message::CopyConstruct<::google::protobuf::EnumValueOptions>(
                               arena, *from._impl_.options_)
@@ -6473,7 +6473,7 @@ ServiceDescriptorProto::ServiceDescriptorProto(::google::protobuf::Arena* arena)
 }
 inline PROTOBUF_NDEBUG_INLINE ServiceDescriptorProto::Impl_::Impl_(
     ::google::protobuf::internal::InternalVisibility visibility, ::google::protobuf::Arena* arena,
-    const Impl_& from)
+    const Impl_& from, const ::google::protobuf::ServiceDescriptorProto& from_msg)
       : _has_bits_{from._has_bits_},
         _cached_size_{0},
         method_{visibility, arena, from.method_},
@@ -6487,7 +6487,7 @@ ServiceDescriptorProto::ServiceDescriptorProto(
   (void)_this;
   _internal_metadata_.MergeFrom<::google::protobuf::UnknownFieldSet>(
       from._internal_metadata_);
-  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_);
+  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_, from);
   ::uint32_t cached_has_bits = _impl_._has_bits_[0];
   _impl_.options_ = (cached_has_bits & 0x00000002u) ? ::google::protobuf::Message::CopyConstruct<::google::protobuf::ServiceOptions>(
                               arena, *from._impl_.options_)
@@ -6762,7 +6762,7 @@ MethodDescriptorProto::MethodDescriptorProto(::google::protobuf::Arena* arena)
 }
 inline PROTOBUF_NDEBUG_INLINE MethodDescriptorProto::Impl_::Impl_(
     ::google::protobuf::internal::InternalVisibility visibility, ::google::protobuf::Arena* arena,
-    const Impl_& from)
+    const Impl_& from, const ::google::protobuf::MethodDescriptorProto& from_msg)
       : _has_bits_{from._has_bits_},
         _cached_size_{0},
         name_(arena, from.name_),
@@ -6777,7 +6777,7 @@ MethodDescriptorProto::MethodDescriptorProto(
   (void)_this;
   _internal_metadata_.MergeFrom<::google::protobuf::UnknownFieldSet>(
       from._internal_metadata_);
-  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_);
+  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_, from);
   ::uint32_t cached_has_bits = _impl_._has_bits_[0];
   _impl_.options_ = (cached_has_bits & 0x00000008u) ? ::google::protobuf::Message::CopyConstruct<::google::protobuf::MethodOptions>(
                               arena, *from._impl_.options_)
@@ -7146,7 +7146,7 @@ FileOptions::FileOptions(::google::protobuf::Arena* arena)
 }
 inline PROTOBUF_NDEBUG_INLINE FileOptions::Impl_::Impl_(
     ::google::protobuf::internal::InternalVisibility visibility, ::google::protobuf::Arena* arena,
-    const Impl_& from)
+    const Impl_& from, const ::google::protobuf::FileOptions& from_msg)
       : _extensions_{visibility, arena},
         _has_bits_{from._has_bits_},
         _cached_size_{0},
@@ -7170,7 +7170,7 @@ FileOptions::FileOptions(
   (void)_this;
   _internal_metadata_.MergeFrom<::google::protobuf::UnknownFieldSet>(
       from._internal_metadata_);
-  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_);
+  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_, from);
   _impl_._extensions_.MergeFrom(this, from._impl_._extensions_);
   ::uint32_t cached_has_bits = _impl_._has_bits_[0];
   _impl_.features_ = (cached_has_bits & 0x00000400u) ? ::google::protobuf::Message::CopyConstruct<::google::protobuf::FeatureSet>(
@@ -7965,7 +7965,7 @@ MessageOptions::MessageOptions(::google::protobuf::Arena* arena)
 }
 inline PROTOBUF_NDEBUG_INLINE MessageOptions::Impl_::Impl_(
     ::google::protobuf::internal::InternalVisibility visibility, ::google::protobuf::Arena* arena,
-    const Impl_& from)
+    const Impl_& from, const ::google::protobuf::MessageOptions& from_msg)
       : _extensions_{visibility, arena},
         _has_bits_{from._has_bits_},
         _cached_size_{0},
@@ -7979,7 +7979,7 @@ MessageOptions::MessageOptions(
   (void)_this;
   _internal_metadata_.MergeFrom<::google::protobuf::UnknownFieldSet>(
       from._internal_metadata_);
-  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_);
+  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_, from);
   _impl_._extensions_.MergeFrom(this, from._impl_._extensions_);
   ::uint32_t cached_has_bits = _impl_._has_bits_[0];
   _impl_.features_ = (cached_has_bits & 0x00000001u) ? ::google::protobuf::Message::CopyConstruct<::google::protobuf::FeatureSet>(
@@ -8356,7 +8356,7 @@ FieldOptions_EditionDefault::FieldOptions_EditionDefault(::google::protobuf::Are
 }
 inline PROTOBUF_NDEBUG_INLINE FieldOptions_EditionDefault::Impl_::Impl_(
     ::google::protobuf::internal::InternalVisibility visibility, ::google::protobuf::Arena* arena,
-    const Impl_& from)
+    const Impl_& from, const ::google::protobuf::FieldOptions_EditionDefault& from_msg)
       : _has_bits_{from._has_bits_},
         _cached_size_{0},
         value_(arena, from.value_) {}
@@ -8369,7 +8369,7 @@ FieldOptions_EditionDefault::FieldOptions_EditionDefault(
   (void)_this;
   _internal_metadata_.MergeFrom<::google::protobuf::UnknownFieldSet>(
       from._internal_metadata_);
-  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_);
+  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_, from);
   _impl_.edition_ = from._impl_.edition_;
 
   // @@protoc_insertion_point(copy_constructor:google.protobuf.FieldOptions.EditionDefault)
@@ -8596,7 +8596,7 @@ FieldOptions::FieldOptions(::google::protobuf::Arena* arena)
 }
 inline PROTOBUF_NDEBUG_INLINE FieldOptions::Impl_::Impl_(
     ::google::protobuf::internal::InternalVisibility visibility, ::google::protobuf::Arena* arena,
-    const Impl_& from)
+    const Impl_& from, const ::google::protobuf::FieldOptions& from_msg)
       : _extensions_{visibility, arena},
         _has_bits_{from._has_bits_},
         _cached_size_{0},
@@ -8612,7 +8612,7 @@ FieldOptions::FieldOptions(
   (void)_this;
   _internal_metadata_.MergeFrom<::google::protobuf::UnknownFieldSet>(
       from._internal_metadata_);
-  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_);
+  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_, from);
   _impl_._extensions_.MergeFrom(this, from._impl_._extensions_);
   ::uint32_t cached_has_bits = _impl_._has_bits_[0];
   _impl_.features_ = (cached_has_bits & 0x00000001u) ? ::google::protobuf::Message::CopyConstruct<::google::protobuf::FeatureSet>(
@@ -9147,7 +9147,7 @@ OneofOptions::OneofOptions(::google::protobuf::Arena* arena)
 }
 inline PROTOBUF_NDEBUG_INLINE OneofOptions::Impl_::Impl_(
     ::google::protobuf::internal::InternalVisibility visibility, ::google::protobuf::Arena* arena,
-    const Impl_& from)
+    const Impl_& from, const ::google::protobuf::OneofOptions& from_msg)
       : _extensions_{visibility, arena},
         _has_bits_{from._has_bits_},
         _cached_size_{0},
@@ -9161,7 +9161,7 @@ OneofOptions::OneofOptions(
   (void)_this;
   _internal_metadata_.MergeFrom<::google::protobuf::UnknownFieldSet>(
       from._internal_metadata_);
-  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_);
+  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_, from);
   _impl_._extensions_.MergeFrom(this, from._impl_._extensions_);
   ::uint32_t cached_has_bits = _impl_._has_bits_[0];
   _impl_.features_ = (cached_has_bits & 0x00000001u) ? ::google::protobuf::Message::CopyConstruct<::google::protobuf::FeatureSet>(
@@ -9412,7 +9412,7 @@ EnumOptions::EnumOptions(::google::protobuf::Arena* arena)
 }
 inline PROTOBUF_NDEBUG_INLINE EnumOptions::Impl_::Impl_(
     ::google::protobuf::internal::InternalVisibility visibility, ::google::protobuf::Arena* arena,
-    const Impl_& from)
+    const Impl_& from, const ::google::protobuf::EnumOptions& from_msg)
       : _extensions_{visibility, arena},
         _has_bits_{from._has_bits_},
         _cached_size_{0},
@@ -9426,7 +9426,7 @@ EnumOptions::EnumOptions(
   (void)_this;
   _internal_metadata_.MergeFrom<::google::protobuf::UnknownFieldSet>(
       from._internal_metadata_);
-  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_);
+  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_, from);
   _impl_._extensions_.MergeFrom(this, from._impl_._extensions_);
   ::uint32_t cached_has_bits = _impl_._has_bits_[0];
   _impl_.features_ = (cached_has_bits & 0x00000001u) ? ::google::protobuf::Message::CopyConstruct<::google::protobuf::FeatureSet>(
@@ -9763,7 +9763,7 @@ EnumValueOptions::EnumValueOptions(::google::protobuf::Arena* arena)
 }
 inline PROTOBUF_NDEBUG_INLINE EnumValueOptions::Impl_::Impl_(
     ::google::protobuf::internal::InternalVisibility visibility, ::google::protobuf::Arena* arena,
-    const Impl_& from)
+    const Impl_& from, const ::google::protobuf::EnumValueOptions& from_msg)
       : _extensions_{visibility, arena},
         _has_bits_{from._has_bits_},
         _cached_size_{0},
@@ -9777,7 +9777,7 @@ EnumValueOptions::EnumValueOptions(
   (void)_this;
   _internal_metadata_.MergeFrom<::google::protobuf::UnknownFieldSet>(
       from._internal_metadata_);
-  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_);
+  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_, from);
   _impl_._extensions_.MergeFrom(this, from._impl_._extensions_);
   ::uint32_t cached_has_bits = _impl_._has_bits_[0];
   _impl_.features_ = (cached_has_bits & 0x00000001u) ? ::google::protobuf::Message::CopyConstruct<::google::protobuf::FeatureSet>(
@@ -10096,7 +10096,7 @@ ServiceOptions::ServiceOptions(::google::protobuf::Arena* arena)
 }
 inline PROTOBUF_NDEBUG_INLINE ServiceOptions::Impl_::Impl_(
     ::google::protobuf::internal::InternalVisibility visibility, ::google::protobuf::Arena* arena,
-    const Impl_& from)
+    const Impl_& from, const ::google::protobuf::ServiceOptions& from_msg)
       : _extensions_{visibility, arena},
         _has_bits_{from._has_bits_},
         _cached_size_{0},
@@ -10110,7 +10110,7 @@ ServiceOptions::ServiceOptions(
   (void)_this;
   _internal_metadata_.MergeFrom<::google::protobuf::UnknownFieldSet>(
       from._internal_metadata_);
-  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_);
+  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_, from);
   _impl_._extensions_.MergeFrom(this, from._impl_._extensions_);
   ::uint32_t cached_has_bits = _impl_._has_bits_[0];
   _impl_.features_ = (cached_has_bits & 0x00000001u) ? ::google::protobuf::Message::CopyConstruct<::google::protobuf::FeatureSet>(
@@ -10398,7 +10398,7 @@ MethodOptions::MethodOptions(::google::protobuf::Arena* arena)
 }
 inline PROTOBUF_NDEBUG_INLINE MethodOptions::Impl_::Impl_(
     ::google::protobuf::internal::InternalVisibility visibility, ::google::protobuf::Arena* arena,
-    const Impl_& from)
+    const Impl_& from, const ::google::protobuf::MethodOptions& from_msg)
       : _extensions_{visibility, arena},
         _has_bits_{from._has_bits_},
         _cached_size_{0},
@@ -10412,7 +10412,7 @@ MethodOptions::MethodOptions(
   (void)_this;
   _internal_metadata_.MergeFrom<::google::protobuf::UnknownFieldSet>(
       from._internal_metadata_);
-  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_);
+  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_, from);
   _impl_._extensions_.MergeFrom(this, from._impl_._extensions_);
   ::uint32_t cached_has_bits = _impl_._has_bits_[0];
   _impl_.features_ = (cached_has_bits & 0x00000001u) ? ::google::protobuf::Message::CopyConstruct<::google::protobuf::FeatureSet>(
@@ -10739,7 +10739,7 @@ UninterpretedOption_NamePart::UninterpretedOption_NamePart(::google::protobuf::A
 }
 inline PROTOBUF_NDEBUG_INLINE UninterpretedOption_NamePart::Impl_::Impl_(
     ::google::protobuf::internal::InternalVisibility visibility, ::google::protobuf::Arena* arena,
-    const Impl_& from)
+    const Impl_& from, const ::google::protobuf::UninterpretedOption_NamePart& from_msg)
       : _has_bits_{from._has_bits_},
         _cached_size_{0},
         name_part_(arena, from.name_part_) {}
@@ -10752,7 +10752,7 @@ UninterpretedOption_NamePart::UninterpretedOption_NamePart(
   (void)_this;
   _internal_metadata_.MergeFrom<::google::protobuf::UnknownFieldSet>(
       from._internal_metadata_);
-  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_);
+  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_, from);
   _impl_.is_extension_ = from._impl_.is_extension_;
 
   // @@protoc_insertion_point(copy_constructor:google.protobuf.UninterpretedOption.NamePart)
@@ -10981,7 +10981,7 @@ UninterpretedOption::UninterpretedOption(::google::protobuf::Arena* arena)
 }
 inline PROTOBUF_NDEBUG_INLINE UninterpretedOption::Impl_::Impl_(
     ::google::protobuf::internal::InternalVisibility visibility, ::google::protobuf::Arena* arena,
-    const Impl_& from)
+    const Impl_& from, const ::google::protobuf::UninterpretedOption& from_msg)
       : _has_bits_{from._has_bits_},
         _cached_size_{0},
         name_{visibility, arena, from.name_},
@@ -10997,7 +10997,7 @@ UninterpretedOption::UninterpretedOption(
   (void)_this;
   _internal_metadata_.MergeFrom<::google::protobuf::UnknownFieldSet>(
       from._internal_metadata_);
-  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_);
+  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_, from);
   ::memcpy(reinterpret_cast<char *>(&_impl_) +
                offsetof(Impl_, positive_int_value_),
            reinterpret_cast<const char *>(&from._impl_) +
@@ -11375,7 +11375,7 @@ FeatureSet::FeatureSet(::google::protobuf::Arena* arena)
 }
 inline PROTOBUF_NDEBUG_INLINE FeatureSet::Impl_::Impl_(
     ::google::protobuf::internal::InternalVisibility visibility, ::google::protobuf::Arena* arena,
-    const Impl_& from)
+    const Impl_& from, const ::google::protobuf::FeatureSet& from_msg)
       : _extensions_{visibility, arena},
         _has_bits_{from._has_bits_},
         _cached_size_{0} {}
@@ -11388,7 +11388,7 @@ FeatureSet::FeatureSet(
   (void)_this;
   _internal_metadata_.MergeFrom<::google::protobuf::UnknownFieldSet>(
       from._internal_metadata_);
-  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_);
+  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_, from);
   _impl_._extensions_.MergeFrom(this, from._impl_._extensions_);
   ::memcpy(reinterpret_cast<char *>(&_impl_) +
                offsetof(Impl_, field_presence_),
@@ -11731,7 +11731,7 @@ FeatureSetDefaults_FeatureSetEditionDefault::FeatureSetDefaults_FeatureSetEditio
 }
 inline PROTOBUF_NDEBUG_INLINE FeatureSetDefaults_FeatureSetEditionDefault::Impl_::Impl_(
     ::google::protobuf::internal::InternalVisibility visibility, ::google::protobuf::Arena* arena,
-    const Impl_& from)
+    const Impl_& from, const ::google::protobuf::FeatureSetDefaults_FeatureSetEditionDefault& from_msg)
       : _has_bits_{from._has_bits_},
         _cached_size_{0} {}
 
@@ -11743,7 +11743,7 @@ FeatureSetDefaults_FeatureSetEditionDefault::FeatureSetDefaults_FeatureSetEditio
   (void)_this;
   _internal_metadata_.MergeFrom<::google::protobuf::UnknownFieldSet>(
       from._internal_metadata_);
-  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_);
+  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_, from);
   ::uint32_t cached_has_bits = _impl_._has_bits_[0];
   _impl_.features_ = (cached_has_bits & 0x00000001u) ? ::google::protobuf::Message::CopyConstruct<::google::protobuf::FeatureSet>(
                               arena, *from._impl_.features_)
@@ -11987,7 +11987,7 @@ FeatureSetDefaults::FeatureSetDefaults(::google::protobuf::Arena* arena)
 }
 inline PROTOBUF_NDEBUG_INLINE FeatureSetDefaults::Impl_::Impl_(
     ::google::protobuf::internal::InternalVisibility visibility, ::google::protobuf::Arena* arena,
-    const Impl_& from)
+    const Impl_& from, const ::google::protobuf::FeatureSetDefaults& from_msg)
       : _has_bits_{from._has_bits_},
         _cached_size_{0},
         defaults_{visibility, arena, from.defaults_} {}
@@ -12000,7 +12000,7 @@ FeatureSetDefaults::FeatureSetDefaults(
   (void)_this;
   _internal_metadata_.MergeFrom<::google::protobuf::UnknownFieldSet>(
       from._internal_metadata_);
-  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_);
+  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_, from);
   ::memcpy(reinterpret_cast<char *>(&_impl_) +
                offsetof(Impl_, minimum_edition_),
            reinterpret_cast<const char *>(&from._impl_) +
@@ -12262,7 +12262,7 @@ SourceCodeInfo_Location::SourceCodeInfo_Location(::google::protobuf::Arena* aren
 }
 inline PROTOBUF_NDEBUG_INLINE SourceCodeInfo_Location::Impl_::Impl_(
     ::google::protobuf::internal::InternalVisibility visibility, ::google::protobuf::Arena* arena,
-    const Impl_& from)
+    const Impl_& from, const ::google::protobuf::SourceCodeInfo_Location& from_msg)
       : _has_bits_{from._has_bits_},
         _cached_size_{0},
         path_{visibility, arena, from.path_},
@@ -12281,7 +12281,7 @@ SourceCodeInfo_Location::SourceCodeInfo_Location(
   (void)_this;
   _internal_metadata_.MergeFrom<::google::protobuf::UnknownFieldSet>(
       from._internal_metadata_);
-  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_);
+  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_, from);
 
   // @@protoc_insertion_point(copy_constructor:google.protobuf.SourceCodeInfo.Location)
 }
@@ -12605,7 +12605,7 @@ SourceCodeInfo::SourceCodeInfo(::google::protobuf::Arena* arena)
 }
 inline PROTOBUF_NDEBUG_INLINE SourceCodeInfo::Impl_::Impl_(
     ::google::protobuf::internal::InternalVisibility visibility, ::google::protobuf::Arena* arena,
-    const Impl_& from)
+    const Impl_& from, const ::google::protobuf::SourceCodeInfo& from_msg)
       : location_{visibility, arena, from.location_},
         _cached_size_{0} {}
 
@@ -12617,7 +12617,7 @@ SourceCodeInfo::SourceCodeInfo(
   (void)_this;
   _internal_metadata_.MergeFrom<::google::protobuf::UnknownFieldSet>(
       from._internal_metadata_);
-  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_);
+  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_, from);
 
   // @@protoc_insertion_point(copy_constructor:google.protobuf.SourceCodeInfo)
 }
@@ -12800,7 +12800,7 @@ GeneratedCodeInfo_Annotation::GeneratedCodeInfo_Annotation(::google::protobuf::A
 }
 inline PROTOBUF_NDEBUG_INLINE GeneratedCodeInfo_Annotation::Impl_::Impl_(
     ::google::protobuf::internal::InternalVisibility visibility, ::google::protobuf::Arena* arena,
-    const Impl_& from)
+    const Impl_& from, const ::google::protobuf::GeneratedCodeInfo_Annotation& from_msg)
       : _has_bits_{from._has_bits_},
         _cached_size_{0},
         path_{visibility, arena, from.path_},
@@ -12815,7 +12815,7 @@ GeneratedCodeInfo_Annotation::GeneratedCodeInfo_Annotation(
   (void)_this;
   _internal_metadata_.MergeFrom<::google::protobuf::UnknownFieldSet>(
       from._internal_metadata_);
-  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_);
+  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_, from);
   ::memcpy(reinterpret_cast<char *>(&_impl_) +
                offsetof(Impl_, begin_),
            reinterpret_cast<const char *>(&from._impl_) +
@@ -13139,7 +13139,7 @@ GeneratedCodeInfo::GeneratedCodeInfo(::google::protobuf::Arena* arena)
 }
 inline PROTOBUF_NDEBUG_INLINE GeneratedCodeInfo::Impl_::Impl_(
     ::google::protobuf::internal::InternalVisibility visibility, ::google::protobuf::Arena* arena,
-    const Impl_& from)
+    const Impl_& from, const ::google::protobuf::GeneratedCodeInfo& from_msg)
       : annotation_{visibility, arena, from.annotation_},
         _cached_size_{0} {}
 
@@ -13151,7 +13151,7 @@ GeneratedCodeInfo::GeneratedCodeInfo(
   (void)_this;
   _internal_metadata_.MergeFrom<::google::protobuf::UnknownFieldSet>(
       from._internal_metadata_);
-  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_);
+  new (&_impl_) Impl_(internal_visibility(), arena, from._impl_, from);
 
   // @@protoc_insertion_point(copy_constructor:google.protobuf.GeneratedCodeInfo)
 }
diff --git a/src/google/protobuf/descriptor.pb.h b/src/google/protobuf/descriptor.pb.h
index b9c4e270bf288..f1b5ccea67e57 100644
--- a/src/google/protobuf/descriptor.pb.h
+++ b/src/google/protobuf/descriptor.pb.h
@@ -876,7 +876,8 @@ class PROTOBUF_EXPORT UninterpretedOption_NamePart final : public ::google::prot
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
                           ::google::protobuf::Arena* arena);
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
-                          ::google::protobuf::Arena* arena, const Impl_& from);
+                          ::google::protobuf::Arena* arena, const Impl_& from,
+                          const UninterpretedOption_NamePart& from_msg);
     ::google::protobuf::internal::HasBits<1> _has_bits_;
     mutable ::google::protobuf::internal::CachedSize _cached_size_;
     ::google::protobuf::internal::ArenaStringPtr name_part_;
@@ -1140,7 +1141,8 @@ class PROTOBUF_EXPORT SourceCodeInfo_Location final : public ::google::protobuf:
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
                           ::google::protobuf::Arena* arena);
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
-                          ::google::protobuf::Arena* arena, const Impl_& from);
+                          ::google::protobuf::Arena* arena, const Impl_& from,
+                          const SourceCodeInfo_Location& from_msg);
     ::google::protobuf::internal::HasBits<1> _has_bits_;
     mutable ::google::protobuf::internal::CachedSize _cached_size_;
     ::google::protobuf::RepeatedField<::int32_t> path_;
@@ -1399,7 +1401,8 @@ class PROTOBUF_EXPORT GeneratedCodeInfo_Annotation final : public ::google::prot
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
                           ::google::protobuf::Arena* arena);
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
-                          ::google::protobuf::Arena* arena, const Impl_& from);
+                          ::google::protobuf::Arena* arena, const Impl_& from,
+                          const GeneratedCodeInfo_Annotation& from_msg);
     ::google::protobuf::internal::HasBits<1> _has_bits_;
     mutable ::google::protobuf::internal::CachedSize _cached_size_;
     ::google::protobuf::RepeatedField<::int32_t> path_;
@@ -1594,7 +1597,8 @@ class PROTOBUF_EXPORT FieldOptions_EditionDefault final : public ::google::proto
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
                           ::google::protobuf::Arena* arena);
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
-                          ::google::protobuf::Arena* arena, const Impl_& from);
+                          ::google::protobuf::Arena* arena, const Impl_& from,
+                          const FieldOptions_EditionDefault& from_msg);
     ::google::protobuf::internal::HasBits<1> _has_bits_;
     mutable ::google::protobuf::internal::CachedSize _cached_size_;
     ::google::protobuf::internal::ArenaStringPtr value_;
@@ -2127,7 +2131,8 @@ class PROTOBUF_EXPORT FeatureSet final : public ::google::protobuf::Message
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
                           ::google::protobuf::Arena* arena);
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
-                          ::google::protobuf::Arena* arena, const Impl_& from);
+                          ::google::protobuf::Arena* arena, const Impl_& from,
+                          const FeatureSet& from_msg);
     ::google::protobuf::internal::ExtensionSet _extensions_;
     ::google::protobuf::internal::HasBits<1> _has_bits_;
     mutable ::google::protobuf::internal::CachedSize _cached_size_;
@@ -2365,7 +2370,8 @@ class PROTOBUF_EXPORT ExtensionRangeOptions_Declaration final : public ::google:
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
                           ::google::protobuf::Arena* arena);
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
-                          ::google::protobuf::Arena* arena, const Impl_& from);
+                          ::google::protobuf::Arena* arena, const Impl_& from,
+                          const ExtensionRangeOptions_Declaration& from_msg);
     ::google::protobuf::internal::HasBits<1> _has_bits_;
     mutable ::google::protobuf::internal::CachedSize _cached_size_;
     ::google::protobuf::internal::ArenaStringPtr full_name_;
@@ -2553,7 +2559,8 @@ class PROTOBUF_EXPORT EnumDescriptorProto_EnumReservedRange final : public ::goo
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
                           ::google::protobuf::Arena* arena);
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
-                          ::google::protobuf::Arena* arena, const Impl_& from);
+                          ::google::protobuf::Arena* arena, const Impl_& from,
+                          const EnumDescriptorProto_EnumReservedRange& from_msg);
     ::google::protobuf::internal::HasBits<1> _has_bits_;
     mutable ::google::protobuf::internal::CachedSize _cached_size_;
     ::int32_t start_;
@@ -2738,7 +2745,8 @@ class PROTOBUF_EXPORT DescriptorProto_ReservedRange final : public ::google::pro
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
                           ::google::protobuf::Arena* arena);
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
-                          ::google::protobuf::Arena* arena, const Impl_& from);
+                          ::google::protobuf::Arena* arena, const Impl_& from,
+                          const DescriptorProto_ReservedRange& from_msg);
     ::google::protobuf::internal::HasBits<1> _has_bits_;
     mutable ::google::protobuf::internal::CachedSize _cached_size_;
     ::int32_t start_;
@@ -3008,7 +3016,8 @@ class PROTOBUF_EXPORT UninterpretedOption final : public ::google::protobuf::Mes
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
                           ::google::protobuf::Arena* arena);
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
-                          ::google::protobuf::Arena* arena, const Impl_& from);
+                          ::google::protobuf::Arena* arena, const Impl_& from,
+                          const UninterpretedOption& from_msg);
     ::google::protobuf::internal::HasBits<1> _has_bits_;
     mutable ::google::protobuf::internal::CachedSize _cached_size_;
     ::google::protobuf::RepeatedPtrField< ::google::protobuf::UninterpretedOption_NamePart > name_;
@@ -3193,7 +3202,8 @@ class PROTOBUF_EXPORT SourceCodeInfo final : public ::google::protobuf::Message
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
                           ::google::protobuf::Arena* arena);
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
-                          ::google::protobuf::Arena* arena, const Impl_& from);
+                          ::google::protobuf::Arena* arena, const Impl_& from,
+                          const SourceCodeInfo& from_msg);
     ::google::protobuf::RepeatedPtrField< ::google::protobuf::SourceCodeInfo_Location > location_;
     mutable ::google::protobuf::internal::CachedSize _cached_size_;
     PROTOBUF_TSAN_DECLARE_MEMBER
@@ -3371,7 +3381,8 @@ class PROTOBUF_EXPORT GeneratedCodeInfo final : public ::google::protobuf::Messa
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
                           ::google::protobuf::Arena* arena);
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
-                          ::google::protobuf::Arena* arena, const Impl_& from);
+                          ::google::protobuf::Arena* arena, const Impl_& from,
+                          const GeneratedCodeInfo& from_msg);
     ::google::protobuf::RepeatedPtrField< ::google::protobuf::GeneratedCodeInfo_Annotation > annotation_;
     mutable ::google::protobuf::internal::CachedSize _cached_size_;
     PROTOBUF_TSAN_DECLARE_MEMBER
@@ -3558,7 +3569,8 @@ class PROTOBUF_EXPORT FeatureSetDefaults_FeatureSetEditionDefault final : public
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
                           ::google::protobuf::Arena* arena);
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
-                          ::google::protobuf::Arena* arena, const Impl_& from);
+                          ::google::protobuf::Arena* arena, const Impl_& from,
+                          const FeatureSetDefaults_FeatureSetEditionDefault& from_msg);
     ::google::protobuf::internal::HasBits<1> _has_bits_;
     mutable ::google::protobuf::internal::CachedSize _cached_size_;
     ::google::protobuf::FeatureSet* features_;
@@ -3944,7 +3956,8 @@ class PROTOBUF_EXPORT ServiceOptions final : public ::google::protobuf::Message
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
                           ::google::protobuf::Arena* arena);
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
-                          ::google::protobuf::Arena* arena, const Impl_& from);
+                          ::google::protobuf::Arena* arena, const Impl_& from,
+                          const ServiceOptions& from_msg);
     ::google::protobuf::internal::ExtensionSet _extensions_;
     ::google::protobuf::internal::HasBits<1> _has_bits_;
     mutable ::google::protobuf::internal::CachedSize _cached_size_;
@@ -4320,7 +4333,8 @@ class PROTOBUF_EXPORT OneofOptions final : public ::google::protobuf::Message
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
                           ::google::protobuf::Arena* arena);
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
-                          ::google::protobuf::Arena* arena, const Impl_& from);
+                          ::google::protobuf::Arena* arena, const Impl_& from,
+                          const OneofOptions& from_msg);
     ::google::protobuf::internal::ExtensionSet _extensions_;
     ::google::protobuf::internal::HasBits<1> _has_bits_;
     mutable ::google::protobuf::internal::CachedSize _cached_size_;
@@ -4739,7 +4753,8 @@ class PROTOBUF_EXPORT MethodOptions final : public ::google::protobuf::Message
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
                           ::google::protobuf::Arena* arena);
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
-                          ::google::protobuf::Arena* arena, const Impl_& from);
+                          ::google::protobuf::Arena* arena, const Impl_& from,
+                          const MethodOptions& from_msg);
     ::google::protobuf::internal::ExtensionSet _extensions_;
     ::google::protobuf::internal::HasBits<1> _has_bits_;
     mutable ::google::protobuf::internal::CachedSize _cached_size_;
@@ -5176,7 +5191,8 @@ class PROTOBUF_EXPORT MessageOptions final : public ::google::protobuf::Message
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
                           ::google::protobuf::Arena* arena);
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
-                          ::google::protobuf::Arena* arena, const Impl_& from);
+                          ::google::protobuf::Arena* arena, const Impl_& from,
+                          const MessageOptions& from_msg);
     ::google::protobuf::internal::ExtensionSet _extensions_;
     ::google::protobuf::internal::HasBits<1> _has_bits_;
     mutable ::google::protobuf::internal::CachedSize _cached_size_;
@@ -5864,7 +5880,8 @@ class PROTOBUF_EXPORT FileOptions final : public ::google::protobuf::Message
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
                           ::google::protobuf::Arena* arena);
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
-                          ::google::protobuf::Arena* arena, const Impl_& from);
+                          ::google::protobuf::Arena* arena, const Impl_& from,
+                          const FileOptions& from_msg);
     ::google::protobuf::internal::ExtensionSet _extensions_;
     ::google::protobuf::internal::HasBits<1> _has_bits_;
     mutable ::google::protobuf::internal::CachedSize _cached_size_;
@@ -6492,7 +6509,8 @@ class PROTOBUF_EXPORT FieldOptions final : public ::google::protobuf::Message
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
                           ::google::protobuf::Arena* arena);
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
-                          ::google::protobuf::Arena* arena, const Impl_& from);
+                          ::google::protobuf::Arena* arena, const Impl_& from,
+                          const FieldOptions& from_msg);
     ::google::protobuf::internal::ExtensionSet _extensions_;
     ::google::protobuf::internal::HasBits<1> _has_bits_;
     mutable ::google::protobuf::internal::CachedSize _cached_size_;
@@ -6708,7 +6726,8 @@ class PROTOBUF_EXPORT FeatureSetDefaults final : public ::google::protobuf::Mess
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
                           ::google::protobuf::Arena* arena);
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
-                          ::google::protobuf::Arena* arena, const Impl_& from);
+                          ::google::protobuf::Arena* arena, const Impl_& from,
+                          const FeatureSetDefaults& from_msg);
     ::google::protobuf::internal::HasBits<1> _has_bits_;
     mutable ::google::protobuf::internal::CachedSize _cached_size_;
     ::google::protobuf::RepeatedPtrField< ::google::protobuf::FeatureSetDefaults_FeatureSetEditionDefault > defaults_;
@@ -7133,7 +7152,8 @@ class PROTOBUF_EXPORT ExtensionRangeOptions final : public ::google::protobuf::M
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
                           ::google::protobuf::Arena* arena);
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
-                          ::google::protobuf::Arena* arena, const Impl_& from);
+                          ::google::protobuf::Arena* arena, const Impl_& from,
+                          const ExtensionRangeOptions& from_msg);
     ::google::protobuf::internal::ExtensionSet _extensions_;
     ::google::protobuf::internal::HasBits<1> _has_bits_;
     mutable ::google::protobuf::internal::CachedSize _cached_size_;
@@ -7534,7 +7554,8 @@ class PROTOBUF_EXPORT EnumValueOptions final : public ::google::protobuf::Messag
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
                           ::google::protobuf::Arena* arena);
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
-                          ::google::protobuf::Arena* arena, const Impl_& from);
+                          ::google::protobuf::Arena* arena, const Impl_& from,
+                          const EnumValueOptions& from_msg);
     ::google::protobuf::internal::ExtensionSet _extensions_;
     ::google::protobuf::internal::HasBits<1> _has_bits_;
     mutable ::google::protobuf::internal::CachedSize _cached_size_;
@@ -7947,7 +7968,8 @@ class PROTOBUF_EXPORT EnumOptions final : public ::google::protobuf::Message
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
                           ::google::protobuf::Arena* arena);
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
-                          ::google::protobuf::Arena* arena, const Impl_& from);
+                          ::google::protobuf::Arena* arena, const Impl_& from,
+                          const EnumOptions& from_msg);
     ::google::protobuf::internal::ExtensionSet _extensions_;
     ::google::protobuf::internal::HasBits<1> _has_bits_;
     mutable ::google::protobuf::internal::CachedSize _cached_size_;
@@ -8146,7 +8168,8 @@ class PROTOBUF_EXPORT OneofDescriptorProto final : public ::google::protobuf::Me
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
                           ::google::protobuf::Arena* arena);
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
-                          ::google::protobuf::Arena* arena, const Impl_& from);
+                          ::google::protobuf::Arena* arena, const Impl_& from,
+                          const OneofDescriptorProto& from_msg);
     ::google::protobuf::internal::HasBits<1> _has_bits_;
     mutable ::google::protobuf::internal::CachedSize _cached_size_;
     ::google::protobuf::internal::ArenaStringPtr name_;
@@ -8401,7 +8424,8 @@ class PROTOBUF_EXPORT MethodDescriptorProto final : public ::google::protobuf::M
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
                           ::google::protobuf::Arena* arena);
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
-                          ::google::protobuf::Arena* arena, const Impl_& from);
+                          ::google::protobuf::Arena* arena, const Impl_& from,
+                          const MethodDescriptorProto& from_msg);
     ::google::protobuf::internal::HasBits<1> _has_bits_;
     mutable ::google::protobuf::internal::CachedSize _cached_size_;
     ::google::protobuf::internal::ArenaStringPtr name_;
@@ -8787,7 +8811,8 @@ class PROTOBUF_EXPORT FieldDescriptorProto final : public ::google::protobuf::Me
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
                           ::google::protobuf::Arena* arena);
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
-                          ::google::protobuf::Arena* arena, const Impl_& from);
+                          ::google::protobuf::Arena* arena, const Impl_& from,
+                          const FieldDescriptorProto& from_msg);
     ::google::protobuf::internal::HasBits<1> _has_bits_;
     mutable ::google::protobuf::internal::CachedSize _cached_size_;
     ::google::protobuf::internal::ArenaStringPtr name_;
@@ -9003,7 +9028,8 @@ class PROTOBUF_EXPORT EnumValueDescriptorProto final : public ::google::protobuf
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
                           ::google::protobuf::Arena* arena);
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
-                          ::google::protobuf::Arena* arena, const Impl_& from);
+                          ::google::protobuf::Arena* arena, const Impl_& from,
+                          const EnumValueDescriptorProto& from_msg);
     ::google::protobuf::internal::HasBits<1> _has_bits_;
     mutable ::google::protobuf::internal::CachedSize _cached_size_;
     ::google::protobuf::internal::ArenaStringPtr name_;
@@ -9205,7 +9231,8 @@ class PROTOBUF_EXPORT DescriptorProto_ExtensionRange final : public ::google::pr
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
                           ::google::protobuf::Arena* arena);
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
-                          ::google::protobuf::Arena* arena, const Impl_& from);
+                          ::google::protobuf::Arena* arena, const Impl_& from,
+                          const DescriptorProto_ExtensionRange& from_msg);
     ::google::protobuf::internal::HasBits<1> _has_bits_;
     mutable ::google::protobuf::internal::CachedSize _cached_size_;
     ::google::protobuf::ExtensionRangeOptions* options_;
@@ -9419,7 +9446,8 @@ class PROTOBUF_EXPORT ServiceDescriptorProto final : public ::google::protobuf::
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
                           ::google::protobuf::Arena* arena);
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
-                          ::google::protobuf::Arena* arena, const Impl_& from);
+                          ::google::protobuf::Arena* arena, const Impl_& from,
+                          const ServiceDescriptorProto& from_msg);
     ::google::protobuf::internal::HasBits<1> _has_bits_;
     mutable ::google::protobuf::internal::CachedSize _cached_size_;
     ::google::protobuf::RepeatedPtrField< ::google::protobuf::MethodDescriptorProto > method_;
@@ -9681,7 +9709,8 @@ class PROTOBUF_EXPORT EnumDescriptorProto final : public ::google::protobuf::Mes
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
                           ::google::protobuf::Arena* arena);
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
-                          ::google::protobuf::Arena* arena, const Impl_& from);
+                          ::google::protobuf::Arena* arena, const Impl_& from,
+                          const EnumDescriptorProto& from_msg);
     ::google::protobuf::internal::HasBits<1> _has_bits_;
     mutable ::google::protobuf::internal::CachedSize _cached_size_;
     ::google::protobuf::RepeatedPtrField< ::google::protobuf::EnumValueDescriptorProto > value_;
@@ -10036,7 +10065,8 @@ class PROTOBUF_EXPORT DescriptorProto final : public ::google::protobuf::Message
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
                           ::google::protobuf::Arena* arena);
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
-                          ::google::protobuf::Arena* arena, const Impl_& from);
+                          ::google::protobuf::Arena* arena, const Impl_& from,
+                          const DescriptorProto& from_msg);
     ::google::protobuf::internal::HasBits<1> _has_bits_;
     mutable ::google::protobuf::internal::CachedSize _cached_size_;
     ::google::protobuf::RepeatedPtrField< ::google::protobuf::FieldDescriptorProto > field_;
@@ -10442,7 +10472,8 @@ class PROTOBUF_EXPORT FileDescriptorProto final : public ::google::protobuf::Mes
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
                           ::google::protobuf::Arena* arena);
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
-                          ::google::protobuf::Arena* arena, const Impl_& from);
+                          ::google::protobuf::Arena* arena, const Impl_& from,
+                          const FileDescriptorProto& from_msg);
     ::google::protobuf::internal::HasBits<1> _has_bits_;
     mutable ::google::protobuf::internal::CachedSize _cached_size_;
     ::google::protobuf::RepeatedPtrField<std::string> dependency_;
@@ -10632,7 +10663,8 @@ class PROTOBUF_EXPORT FileDescriptorSet final : public ::google::protobuf::Messa
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
                           ::google::protobuf::Arena* arena);
     inline explicit Impl_(::google::protobuf::internal::InternalVisibility visibility,
-                          ::google::protobuf::Arena* arena, const Impl_& from);
+                          ::google::protobuf::Arena* arena, const Impl_& from,
+                          const FileDescriptorSet& from_msg);
     ::google::protobuf::RepeatedPtrField< ::google::protobuf::FileDescriptorProto > file_;
     mutable ::google::protobuf::internal::CachedSize _cached_size_;
     PROTOBUF_TSAN_DECLARE_MEMBER
diff --git a/src/google/protobuf/extension_set.cc b/src/google/protobuf/extension_set.cc
index dea9d12db79bf..21f24037a91eb 100644
--- a/src/google/protobuf/extension_set.cc
+++ b/src/google/protobuf/extension_set.cc
@@ -1035,7 +1035,7 @@ void ExtensionSet::InternalExtensionMergeFrom(const MessageLite* extendee,
                   other_extension.lazymessage_value->New(arena);
               extension->lazymessage_value->MergeFrom(
                   GetPrototypeForLazyMessage(extendee, number),
-                  *other_extension.lazymessage_value, arena);
+                  *other_extension.lazymessage_value, arena, other_arena);
             } else {
               extension->is_lazy = false;
               extension->message_value =
@@ -1051,7 +1051,7 @@ void ExtensionSet::InternalExtensionMergeFrom(const MessageLite* extendee,
               if (extension->is_lazy) {
                 extension->lazymessage_value->MergeFrom(
                     GetPrototypeForLazyMessage(extendee, number),
-                    *other_extension.lazymessage_value, arena);
+                    *other_extension.lazymessage_value, arena, other_arena);
               } else {
                 extension->message_value->CheckTypeAndMergeFrom(
                     other_extension.lazymessage_value->GetMessage(
diff --git a/src/google/protobuf/extension_set.h b/src/google/protobuf/extension_set.h
index 3eebcefc4021d..8b95b722492fe 100644
--- a/src/google/protobuf/extension_set.h
+++ b/src/google/protobuf/extension_set.h
@@ -609,7 +609,8 @@ class PROTOBUF_EXPORT ExtensionSet {
     virtual size_t SpaceUsedLong() const = 0;
 
     virtual void MergeFrom(const MessageLite* prototype,
-                           const LazyMessageExtension& other, Arena* arena) = 0;
+                           const LazyMessageExtension& other, Arena* arena,
+                           Arena* other_arena) = 0;
     virtual void MergeFromMessage(const MessageLite& msg, Arena* arena) = 0;
     virtual void Clear() = 0;
 
diff --git a/src/google/protobuf/generated_message_reflection.cc b/src/google/protobuf/generated_message_reflection.cc
index 5334e401dc6fa..1443fb5ae1e1e 100644
--- a/src/google/protobuf/generated_message_reflection.cc
+++ b/src/google/protobuf/generated_message_reflection.cc
@@ -3048,7 +3048,6 @@ void Reflection::ClearOneof(Message* message,
         default:
           break;
       }
-    } else {
     }
 
     *MutableOneofCase(message, oneof_descriptor) = 0;