Remove custom HasPreservingUnknownEnumSemantics method.

C++ descriptor now provides is_closed() on EnumDescriptor, use that instead.

PiperOrigin-RevId: 485307512

src/google/protobuf/compiler/objectivec/enum.cc

@@ -126,7 +126,7 @@ void EnumGenerator::GenerateHeader(io::Printer* printer) {
       name_);
   printer->Indent();
 
-  if (HasPreservingUnknownEnumSemantics(descriptor_->file())) {
+  if (!descriptor_->is_closed()) {
     // Include the unknown value.
     printer->Print(
         // clang-format off

src/google/protobuf/compiler/objectivec/enum_field.cc

@@ -76,7 +76,7 @@ EnumFieldGenerator::EnumFieldGenerator(const FieldDescriptor* descriptor)
 
 void EnumFieldGenerator::GenerateCFunctionDeclarations(
     io::Printer* printer) const {
-  if (!HasPreservingUnknownEnumSemantics(descriptor_->file())) {
+  if (descriptor_->enum_type()->is_closed()) {
     return;
   }
 
@@ -100,7 +100,9 @@ void EnumFieldGenerator::GenerateCFunctionDeclarations(
 
 void EnumFieldGenerator::GenerateCFunctionImplementations(
     io::Printer* printer) const {
-  if (!HasPreservingUnknownEnumSemantics(descriptor_->file())) return;
+  if (descriptor_->enum_type()->is_closed()) {
+    return;
+  }
 
   // clang-format off
   printer->Print(

src/google/protobuf/compiler/objectivec/helpers.h

@@ -44,10 +44,6 @@ namespace protobuf {
 namespace compiler {
 namespace objectivec {
 
-inline bool HasPreservingUnknownEnumSemantics(const FileDescriptor* file) {
-  return file->syntax() == FileDescriptor::SYNTAX_PROTO3;
-}
-
 // Escape C++ trigraphs by escaping question marks to "\?".
 std::string EscapeTrigraphs(absl::string_view to_escape);