Use is_closed() in more places in the runtime.

PiperOrigin-RevId: 508709514

src/google/protobuf/generated_message_reflection.cc

@@ -1339,8 +1339,8 @@ void Reflection::ClearField(Message* message,
 
         case FieldDescriptor::CPPTYPE_MESSAGE:
           if (schema_.HasBitIndex(field) == static_cast<uint32_t>(-1)) {
-            // Proto3 does not have has-bits and we need to set a message field
-            // to nullptr in order to indicate its un-presence.
+            // Some fields do not have hasbits and we need to set a message
+            // field to nullptr in order to indicate its un-presence.
             if (message->GetArenaForAllocation() == nullptr) {
               delete *MutableRaw<Message*>(message, field);
             }
@@ -1554,8 +1554,7 @@ void CheckInOrder(const FieldDescriptor* field, uint32_t* last) {
 
 namespace internal {
 bool CreateUnknownEnumValues(const FieldDescriptor* field) {
-  bool open_enum = false;
-  return field->file()->syntax() == FileDescriptor::SYNTAX_PROTO3 || open_enum;
+  return field->enum_type() == nullptr || !field->enum_type()->is_closed();
 }
 }  // namespace internal
 using internal::CreateUnknownEnumValues;

src/google/protobuf/wire_format.cc

@@ -412,7 +412,7 @@ bool WireFormat::ParseAndMergeMessageSetField(uint32_t field_number,
 }
 
 static bool StrictUtf8Check(const FieldDescriptor* field) {
-  return field->file()->syntax() == FileDescriptor::SYNTAX_PROTO3;
+  return field->requires_utf8_validation();
 }
 
 bool WireFormat::ParseAndMergeField(
@@ -484,8 +484,7 @@ bool WireFormat::ParseAndMergeField(
           if (!WireFormatLite::ReadPrimitive<int, WireFormatLite::TYPE_ENUM>(
                   input, &value))
             return false;
-          if (message->GetDescriptor()->file()->syntax() ==
-              FileDescriptor::SYNTAX_PROTO3) {
+          if (!field->enum_type()->is_closed()) {
             message_reflection->AddEnumValue(message, field, value);
           } else {
             const EnumValueDescriptor* enum_value =
@@ -869,8 +868,7 @@ const char* WireFormat::_InternalParseAndMergeField(
           auto rep_enum =
               reflection->MutableRepeatedFieldInternal<int>(msg, field);
           bool open_enum = false;
-          if (field->file()->syntax() == FileDescriptor::SYNTAX_PROTO3 ||
-              open_enum) {
+          if (!field->enum_type()->is_closed() || open_enum) {
             ptr = internal::PackedEnumParser(rep_enum, ptr, ctx);
           } else {
             return ctx->ReadPackedVarint(