Make ExtensionIdentifier's constructor private

PiperOrigin-RevId: 687065564

hpb/extension.h

@@ -61,14 +61,14 @@ class ExtensionIdentifier : public ExtensionMiniTableProvider {
   using Extension = ExtensionType;
   using Extendee = ExtendeeType;
 
+ private:
   constexpr explicit ExtensionIdentifier(
       const upb_MiniTableExtension* mini_table_ext)
       : ExtensionMiniTableProvider(mini_table_ext) {}
-
- private:
   constexpr uint32_t number() const {
     return upb_MiniTableExtension_Number(mini_table_ext());
   }
+
   friend struct PrivateAccess;
 };
 

hpb/internal/internal.h

@@ -9,6 +9,7 @@
 #define GOOGLE_PROTOBUF_HPB_INTERNAL_INTERNAL_H__
 
 #include <cstdint>
+#include <utility>
 
 #include "upb/mem/arena.h"
 #include "upb/message/message.h"
@@ -37,6 +38,11 @@ struct PrivateAccess {
     return typename T::Proxy(upb_Message_New(T::minitable(), arena), arena);
   }
 
+  template <typename T, typename... Args>
+  static auto InvokeConstructor(Args&&... args) {
+    return T(std::forward<Args>(args)...);
+  }
+
   template <typename ExtensionId>
   static constexpr uint32_t GetExtensionNumber(const ExtensionId& id) {
     return id.number();

hpb_generator/gen_extensions.cc

@@ -9,7 +9,6 @@
 
 #include "absl/strings/str_cat.h"
 #include "google/protobuf/compiler/hpb/context.h"
-#include "google/protobuf/compiler/hpb/gen_utils.h"
 #include "google/protobuf/compiler/hpb/names.h"
 #include "upb_generator/c/names.h"
 
@@ -69,14 +68,18 @@ void WriteExtensionIdentifier(const protobuf::FieldDescriptor* ext,
   if (ext->extension_scope()) {
     ctx.EmitLegacy(
         R"cc(
-          const hpb::internal::ExtensionIdentifier<$0, $3> $4::$2(&$1);
+          const hpb::internal::ExtensionIdentifier<$0, $3> $4::$2 =
+              hpb::internal::PrivateAccess::InvokeConstructor<
+                  hpb::internal::ExtensionIdentifier<$0, $3>>(&$1);
         )cc",
         ContainingTypeName(ext), mini_table_name, ext->name(),
         CppTypeParameterName(ext), ClassName(ext->extension_scope()));
   } else {
     ctx.EmitLegacy(
         R"cc(
-          const hpb::internal::ExtensionIdentifier<$0, $3> $2(&$1);
+          const hpb::internal::ExtensionIdentifier<$0, $3> $2 =
+              hpb::internal::PrivateAccess::InvokeConstructor<
+                  hpb::internal::ExtensionIdentifier<$0, $3>>(&$1);
         )cc",
         ContainingTypeName(ext), mini_table_name, ext->name(),
         CppTypeParameterName(ext));