revert as workaround for compiler error with old clang < 17

commit 940af9f2c87b436559b97c53763aa9eaaf1254eb
Author: Jeremy Roman <jbroman@chromium.org>
Date:   Wed Nov 15 16:24:54 2023 +0000

    Use C++20 features to simplify blink::NativeValueTraitsBase.
    
    These allow some of the metaprogramming bits to be simplified a little.
    
    Change-Id: I052b4397586d21348401616e1792afdb9662f975
    Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5030335
    Reviewed-by: Yuki Shiino <yukishiino@chromium.org>
    Commit-Queue: Jeremy Roman <jbroman@chromium.org>
    Cr-Commit-Position: refs/heads/main@{#1224978}

--- a/third_party/blink/renderer/bindings/core/v8/native_value_traits.h
+++ b/third_party/blink/renderer/bindings/core/v8/native_value_traits.h
@@ -5,7 +5,6 @@
 #ifndef THIRD_PARTY_BLINK_RENDERER_BINDINGS_CORE_V8_NATIVE_VALUE_TRAITS_H_
 #define THIRD_PARTY_BLINK_RENDERER_BINDINGS_CORE_V8_NATIVE_VALUE_TRAITS_H_
 
-#include <concepts>
 #include <type_traits>
 
 #include "third_party/blink/renderer/bindings/core/v8/idl_types_base.h"
@@ -31,7 +30,7 @@ class ExceptionState;
 //     return toInt32(isolate, value, exceptionState, NormalConversion);
 //   }
 // }
-template <typename T>
+template <typename T, typename SFINAEHelper = void>
 struct NativeValueTraits;
 
 // This declaration serves only as a blueprint for specializations: the
@@ -46,15 +45,22 @@ struct NativeValueTraits;
 
 namespace bindings {
 
+template <typename T, typename = void>
+struct NativeValueTraitsHasIsNull : std::false_type {};
+
 template <typename T>
-struct ImplTypeFor {
-  using type = T;
-};
+struct NativeValueTraitsHasIsNull<
+    T,
+    std::void_t<decltype(std::declval<T>().IsNull())>> : std::true_type {};
 
 template <typename T>
-  requires std::derived_from<T, IDLBase>
-struct ImplTypeFor<T> {
-  using type = typename T::ImplType;
+struct NativeValueTraitsHasNullValue {
+  // true if |T| supports IDL null value.
+  static constexpr bool value =
+      // ScriptValue, String, and union types have IsNull member function.
+      bindings::NativeValueTraitsHasIsNull<T>::value ||
+      // Pointer types have nullptr as IDL null value.
+      std::is_pointer<T>::value;
 };
 
 }  // namespace bindings
@@ -72,17 +78,37 @@ struct ImplTypeFor<T> {
 // If present, |NullValue()| will be used when converting from the nullable type
 // T?, and should be used if the impl type has an existing "null" state. If not
 // present, WTF::Optional will be used to wrap the type.
-template <typename T>
+template <typename T, typename SFINAEHelper = void>
 struct NativeValueTraitsBase {
   STATIC_ONLY(NativeValueTraitsBase);
 
-  using ImplType = bindings::ImplTypeFor<T>::type;
+  using ImplType = T;
+
+  static constexpr bool has_null_value =
+      bindings::NativeValueTraitsHasNullValue<ImplType>::value;
+
+  template <typename... ExtraArgs>
+  static decltype(auto) ArgumentValue(v8::Isolate* isolate,
+                                      int argument_index,
+                                      v8::Local<v8::Value> value,
+                                      ExceptionState& exception_state,
+                                      ExtraArgs... extra_args) {
+    return NativeValueTraits<std::remove_pointer_t<T>>::NativeValue(
+        isolate, value, exception_state,
+        std::forward<ExtraArgs>(extra_args)...);
+  }
+};
+
+template <typename T>
+struct NativeValueTraitsBase<
+    T,
+    std::enable_if_t<std::is_base_of<IDLBase, T>::value>> {
+  STATIC_ONLY(NativeValueTraitsBase);
+
+  using ImplType = typename T::ImplType;
 
-  // Pointer types have nullptr as IDL null value.
-  // ScriptValue, String, and union types have IsNull member function.
   static constexpr bool has_null_value =
-      std::is_pointer_v<ImplType> ||
-      requires(ImplType value) { value.IsNull(); };
+      bindings::NativeValueTraitsHasNullValue<ImplType>::value;
 
   // This should only be true for certain subclasses of ScriptWrappable
   // that satisfy the assumptions of CreateIDLSequenceFromV8ArraySlow() with
--- a/third_party/blink/renderer/bindings/core/v8/native_value_traits_buffer_sources.cc
+++ b/third_party/blink/renderer/bindings/core/v8/native_value_traits_buffer_sources.cc
@@ -7,7 +7,6 @@
 #include "third_party/blink/renderer/core/core_export.h"
 #include "third_party/blink/renderer/core/execution_context/execution_context.h"
 #include "third_party/blink/renderer/core/frame/web_feature.h"
-#include "third_party/blink/renderer/core/typed_arrays/flexible_array_buffer_view.h"
 #include "third_party/blink/renderer/core/typed_arrays/typed_flexible_array_buffer_view.h"
 
 namespace blink {
@@ -698,11 +697,12 @@ DOMArrayBufferBase* NativeValueTraits<
 // ArrayBufferView
 
 template <typename T>
-  requires std::derived_from<T, DOMArrayBufferView>
-NotShared<T> NativeValueTraits<NotShared<T>>::NativeValue(
-    v8::Isolate* isolate,
-    v8::Local<v8::Value> value,
-    ExceptionState& exception_state) {
+NotShared<T> NativeValueTraits<
+    NotShared<T>,
+    typename std::enable_if_t<std::is_base_of<DOMArrayBufferView, T>::value>>::
+    NativeValue(v8::Isolate* isolate,
+                v8::Local<v8::Value> value,
+                ExceptionState& exception_state) {
   return NativeValueImpl<
       RecipeTrait<NotShared<T>>, ToDOMViewType<T, kNotShared>,
       Nullablity::kIsNotNullable, BufferSizeCheck::kCheck,
@@ -711,12 +711,13 @@ NotShared<T> NativeValueTraits<NotShared
 }
 
 template <typename T>
-  requires std::derived_from<T, DOMArrayBufferView>
-NotShared<T> NativeValueTraits<NotShared<T>>::ArgumentValue(
-    v8::Isolate* isolate,
-    int argument_index,
-    v8::Local<v8::Value> value,
-    ExceptionState& exception_state) {
+NotShared<T> NativeValueTraits<
+    NotShared<T>,
+    typename std::enable_if_t<std::is_base_of<DOMArrayBufferView, T>::value>>::
+    ArgumentValue(v8::Isolate* isolate,
+                  int argument_index,
+                  v8::Local<v8::Value> value,
+                  ExceptionState& exception_state) {
   return ArgumentValueImpl<
       RecipeTrait<NotShared<T>>, ToDOMViewType<T, kNotShared>,
       Nullablity::kIsNotNullable, BufferSizeCheck::kCheck,
@@ -727,11 +728,12 @@ NotShared<T> NativeValueTraits<NotShared
 // [AllowShared] ArrayBufferView
 
 template <typename T>
-  requires std::derived_from<T, DOMArrayBufferView>
-MaybeShared<T> NativeValueTraits<MaybeShared<T>>::NativeValue(
-    v8::Isolate* isolate,
-    v8::Local<v8::Value> value,
-    ExceptionState& exception_state) {
+MaybeShared<T> NativeValueTraits<
+    MaybeShared<T>,
+    typename std::enable_if_t<std::is_base_of<DOMArrayBufferView, T>::value>>::
+    NativeValue(v8::Isolate* isolate,
+                v8::Local<v8::Value> value,
+                ExceptionState& exception_state) {
   return NativeValueImpl<RecipeTrait<MaybeShared<T>>,
                          ToDOMViewType<T, kMaybeShared>,
                          Nullablity::kIsNotNullable, BufferSizeCheck::kCheck,
@@ -740,12 +742,13 @@ MaybeShared<T> NativeValueTraits<MaybeSh
 }
 
 template <typename T>
-  requires std::derived_from<T, DOMArrayBufferView>
-MaybeShared<T> NativeValueTraits<MaybeShared<T>>::ArgumentValue(
-    v8::Isolate* isolate,
-    int argument_index,
-    v8::Local<v8::Value> value,
-    ExceptionState& exception_state) {
+MaybeShared<T> NativeValueTraits<
+    MaybeShared<T>,
+    typename std::enable_if_t<std::is_base_of<DOMArrayBufferView, T>::value>>::
+    ArgumentValue(v8::Isolate* isolate,
+                  int argument_index,
+                  v8::Local<v8::Value> value,
+                  ExceptionState& exception_state) {
   return ArgumentValueImpl<RecipeTrait<MaybeShared<T>>,
                            ToDOMViewType<T, kMaybeShared>,
                            Nullablity::kIsNotNullable, BufferSizeCheck::kCheck,
@@ -756,12 +759,12 @@ MaybeShared<T> NativeValueTraits<MaybeSh
 // [AllowShared, BufferSourceTypeNoSizeLimit] ArrayBufferView
 
 template <typename T>
-  requires std::derived_from<T, DOMArrayBufferView>
-MaybeShared<T>
-NativeValueTraits<IDLBufferSourceTypeNoSizeLimit<MaybeShared<T>>>::NativeValue(
-    v8::Isolate* isolate,
-    v8::Local<v8::Value> value,
-    ExceptionState& exception_state) {
+MaybeShared<T> NativeValueTraits<
+    IDLBufferSourceTypeNoSizeLimit<MaybeShared<T>>,
+    typename std::enable_if_t<std::is_base_of<DOMArrayBufferView, T>::value>>::
+    NativeValue(v8::Isolate* isolate,
+                v8::Local<v8::Value> value,
+                ExceptionState& exception_state) {
   return NativeValueImpl<
       RecipeTrait<MaybeShared<T>>, ToDOMViewType<T, kMaybeShared>,
       Nullablity::kIsNotNullable, BufferSizeCheck::kDoNotCheck,
@@ -770,12 +773,13 @@ NativeValueTraits<IDLBufferSourceTypeNoS
 }
 
 template <typename T>
-  requires std::derived_from<T, DOMArrayBufferView>
-MaybeShared<T> NativeValueTraits<IDLBufferSourceTypeNoSizeLimit<
-    MaybeShared<T>>>::ArgumentValue(v8::Isolate* isolate,
-                                    int argument_index,
-                                    v8::Local<v8::Value> value,
-                                    ExceptionState& exception_state) {
+MaybeShared<T> NativeValueTraits<
+    IDLBufferSourceTypeNoSizeLimit<MaybeShared<T>>,
+    typename std::enable_if_t<std::is_base_of<DOMArrayBufferView, T>::value>>::
+    ArgumentValue(v8::Isolate* isolate,
+                  int argument_index,
+                  v8::Local<v8::Value> value,
+                  ExceptionState& exception_state) {
   return ArgumentValueImpl<
       RecipeTrait<MaybeShared<T>>, ToDOMViewType<T, kMaybeShared>,
       Nullablity::kIsNotNullable, BufferSizeCheck::kDoNotCheck,
@@ -786,11 +790,12 @@ MaybeShared<T> NativeValueTraits<IDLBuff
 // Nullable ArrayBufferView
 
 template <typename T>
-  requires std::derived_from<T, DOMArrayBufferView>
-NotShared<T> NativeValueTraits<IDLNullable<NotShared<T>>>::NativeValue(
-    v8::Isolate* isolate,
-    v8::Local<v8::Value> value,
-    ExceptionState& exception_state) {
+NotShared<T> NativeValueTraits<
+    IDLNullable<NotShared<T>>,
+    typename std::enable_if_t<std::is_base_of<DOMArrayBufferView, T>::value>>::
+    NativeValue(v8::Isolate* isolate,
+                v8::Local<v8::Value> value,
+                ExceptionState& exception_state) {
   return NativeValueImpl<
       RecipeTrait<NotShared<T>>, ToDOMViewType<T, kNotShared>,
       Nullablity::kIsNullable, BufferSizeCheck::kCheck,
@@ -799,12 +804,13 @@ NotShared<T> NativeValueTraits<IDLNullab
 }
 
 template <typename T>
-  requires std::derived_from<T, DOMArrayBufferView>
-NotShared<T> NativeValueTraits<IDLNullable<NotShared<T>>>::ArgumentValue(
-    v8::Isolate* isolate,
-    int argument_index,
-    v8::Local<v8::Value> value,
-    ExceptionState& exception_state) {
+NotShared<T> NativeValueTraits<
+    IDLNullable<NotShared<T>>,
+    typename std::enable_if_t<std::is_base_of<DOMArrayBufferView, T>::value>>::
+    ArgumentValue(v8::Isolate* isolate,
+                  int argument_index,
+                  v8::Local<v8::Value> value,
+                  ExceptionState& exception_state) {
   return ArgumentValueImpl<
       RecipeTrait<NotShared<T>>, ToDOMViewType<T, kNotShared>,
       Nullablity::kIsNullable, BufferSizeCheck::kCheck,
@@ -815,11 +821,12 @@ NotShared<T> NativeValueTraits<IDLNullab
 // Nullable [AllowShared] ArrayBufferView
 
 template <typename T>
-  requires std::derived_from<T, DOMArrayBufferView>
-MaybeShared<T> NativeValueTraits<IDLNullable<MaybeShared<T>>>::NativeValue(
-    v8::Isolate* isolate,
-    v8::Local<v8::Value> value,
-    ExceptionState& exception_state) {
+MaybeShared<T> NativeValueTraits<
+    IDLNullable<MaybeShared<T>>,
+    typename std::enable_if_t<std::is_base_of<DOMArrayBufferView, T>::value>>::
+    NativeValue(v8::Isolate* isolate,
+                v8::Local<v8::Value> value,
+                ExceptionState& exception_state) {
   return NativeValueImpl<RecipeTrait<MaybeShared<T>>,
                          ToDOMViewType<T, kMaybeShared>,
                          Nullablity::kIsNullable, BufferSizeCheck::kCheck,
@@ -828,12 +835,13 @@ MaybeShared<T> NativeValueTraits<IDLNull
 }
 
 template <typename T>
-  requires std::derived_from<T, DOMArrayBufferView>
-MaybeShared<T> NativeValueTraits<IDLNullable<MaybeShared<T>>>::ArgumentValue(
-    v8::Isolate* isolate,
-    int argument_index,
-    v8::Local<v8::Value> value,
-    ExceptionState& exception_state) {
+MaybeShared<T> NativeValueTraits<
+    IDLNullable<MaybeShared<T>>,
+    typename std::enable_if_t<std::is_base_of<DOMArrayBufferView, T>::value>>::
+    ArgumentValue(v8::Isolate* isolate,
+                  int argument_index,
+                  v8::Local<v8::Value> value,
+                  ExceptionState& exception_state) {
   return ArgumentValueImpl<RecipeTrait<MaybeShared<T>>,
                            ToDOMViewType<T, kMaybeShared>,
                            Nullablity::kIsNullable, BufferSizeCheck::kCheck,
@@ -844,9 +852,9 @@ MaybeShared<T> NativeValueTraits<IDLNull
 // Nullable [AllowShared, BufferSourceTypeNoSizeLimit] ArrayBufferView
 
 template <typename T>
-  requires std::derived_from<T, DOMArrayBufferView>
-MaybeShared<T>
-NativeValueTraits<IDLNullable<IDLBufferSourceTypeNoSizeLimit<MaybeShared<T>>>>::
+MaybeShared<T> NativeValueTraits<
+    IDLNullable<IDLBufferSourceTypeNoSizeLimit<MaybeShared<T>>>,
+    typename std::enable_if_t<std::is_base_of<DOMArrayBufferView, T>::value>>::
     ArgumentValue(v8::Isolate* isolate,
                   int argument_index,
                   v8::Local<v8::Value> value,
@@ -861,11 +869,13 @@ NativeValueTraits<IDLNullable<IDLBufferS
 // [AllowShared, FlexibleArrayBufferView] ArrayBufferView
 
 template <typename T>
-  requires std::derived_from<T, FlexibleArrayBufferView>
-T NativeValueTraits<T>::ArgumentValue(v8::Isolate* isolate,
-                                      int argument_index,
-                                      v8::Local<v8::Value> value,
-                                      ExceptionState& exception_state) {
+T NativeValueTraits<T,
+                    typename std::enable_if_t<
+                        std::is_base_of<FlexibleArrayBufferView, T>::value>>::
+    ArgumentValue(v8::Isolate* isolate,
+                  int argument_index,
+                  v8::Local<v8::Value> value,
+                  ExceptionState& exception_state) {
   return ArgumentValueImpl<RecipeTrait<T>, ToFlexibleArrayBufferView,
                            Nullablity::kIsNotNullable, BufferSizeCheck::kCheck,
                            ResizableAllowance::kDisallowResizable,
@@ -877,12 +887,13 @@ T NativeValueTraits<T>::ArgumentValue(v8
 // ArrayBufferView
 
 template <typename T>
-  requires std::derived_from<T, FlexibleArrayBufferView>
-T NativeValueTraits<IDLBufferSourceTypeNoSizeLimit<T>>::ArgumentValue(
-    v8::Isolate* isolate,
-    int argument_index,
-    v8::Local<v8::Value> value,
-    ExceptionState& exception_state) {
+T NativeValueTraits<IDLBufferSourceTypeNoSizeLimit<T>,
+                    typename std::enable_if_t<
+                        std::is_base_of<FlexibleArrayBufferView, T>::value>>::
+    ArgumentValue(v8::Isolate* isolate,
+                  int argument_index,
+                  v8::Local<v8::Value> value,
+                  ExceptionState& exception_state) {
   return ArgumentValueImpl<
       RecipeTrait<T>, ToFlexibleArrayBufferView, Nullablity::kIsNotNullable,
       BufferSizeCheck::kDoNotCheck, ResizableAllowance::kDisallowResizable,
@@ -893,12 +904,13 @@ T NativeValueTraits<IDLBufferSourceTypeN
 // Nullable [AllowShared, FlexibleArrayBufferView] ArrayBufferView
 
 template <typename T>
-  requires std::derived_from<T, FlexibleArrayBufferView>
-T NativeValueTraits<IDLNullable<T>>::ArgumentValue(
-    v8::Isolate* isolate,
-    int argument_index,
-    v8::Local<v8::Value> value,
-    ExceptionState& exception_state) {
+T NativeValueTraits<IDLNullable<T>,
+                    typename std::enable_if_t<
+                        std::is_base_of<FlexibleArrayBufferView, T>::value>>::
+    ArgumentValue(v8::Isolate* isolate,
+                  int argument_index,
+                  v8::Local<v8::Value> value,
+                  ExceptionState& exception_state) {
   return ArgumentValueImpl<RecipeTrait<T>, ToFlexibleArrayBufferView,
                            Nullablity::kIsNullable, BufferSizeCheck::kCheck,
                            ResizableAllowance::kDisallowResizable,
--- a/third_party/blink/renderer/bindings/core/v8/native_value_traits_impl.h
+++ b/third_party/blink/renderer/bindings/core/v8/native_value_traits_impl.h
@@ -5,9 +5,7 @@
 #ifndef THIRD_PARTY_BLINK_RENDERER_BINDINGS_CORE_V8_NATIVE_VALUE_TRAITS_IMPL_H_
 #define THIRD_PARTY_BLINK_RENDERER_BINDINGS_CORE_V8_NATIVE_VALUE_TRAITS_IMPL_H_
 
-#include <concepts>
 #include <optional>
-#include <type_traits>
 
 #include "third_party/blink/renderer/bindings/core/v8/idl_types.h"
 #include "third_party/blink/renderer/bindings/core/v8/native_value_traits.h"
@@ -718,8 +716,9 @@ struct CORE_EXPORT NativeValueTraits<
 };
 
 template <typename T>
-  requires std::derived_from<T, DOMArrayBufferView>
-struct NativeValueTraits<T> {
+struct NativeValueTraits<
+    T,
+    typename std::enable_if_t<std::is_base_of<DOMArrayBufferView, T>::value>> {
   // NotShared<T> or MaybeShared<T> should be used instead.
   static T* NativeValue(v8::Isolate* isolate,
                         v8::Local<v8::Value> value,
@@ -731,8 +730,9 @@ struct NativeValueTraits<T> {
 };
 
 template <typename T>
-  requires std::derived_from<T, DOMArrayBufferView>
-struct NativeValueTraits<IDLNullable<T>> {
+struct NativeValueTraits<
+    IDLNullable<T>,
+    typename std::enable_if_t<std::is_base_of<DOMArrayBufferView, T>::value>> {
   // NotShared<T> or MaybeShared<T> should be used instead.
   static T* NativeValue(v8::Isolate* isolate,
                         v8::Local<v8::Value> value,
@@ -744,8 +744,9 @@ struct NativeValueTraits<IDLNullable<T>>
 };
 
 template <typename T>
-  requires std::derived_from<T, DOMArrayBufferView>
-struct NativeValueTraits<NotShared<T>>
+struct NativeValueTraits<
+    NotShared<T>,
+    typename std::enable_if_t<std::is_base_of<DOMArrayBufferView, T>::value>>
     : public NativeValueTraitsBase<NotShared<T>> {
   static NotShared<T> NativeValue(v8::Isolate* isolate,
                                   v8::Local<v8::Value> value,
@@ -758,8 +759,9 @@ struct NativeValueTraits<NotShared<T>>
 };
 
 template <typename T>
-  requires std::derived_from<T, DOMArrayBufferView>
-struct NativeValueTraits<IDLNullable<NotShared<T>>>
+struct NativeValueTraits<
+    IDLNullable<NotShared<T>>,
+    typename std::enable_if_t<std::is_base_of<DOMArrayBufferView, T>::value>>
     : public NativeValueTraitsBase<NotShared<T>> {
   static NotShared<T> NativeValue(v8::Isolate* isolate,
                                   v8::Local<v8::Value> value,
@@ -772,8 +774,9 @@ struct NativeValueTraits<IDLNullable<Not
 };
 
 template <typename T>
-  requires std::derived_from<T, DOMArrayBufferView>
-struct NativeValueTraits<MaybeShared<T>>
+struct NativeValueTraits<
+    MaybeShared<T>,
+    typename std::enable_if_t<std::is_base_of<DOMArrayBufferView, T>::value>>
     : public NativeValueTraitsBase<MaybeShared<T>> {
   static MaybeShared<T> NativeValue(v8::Isolate* isolate,
                                     v8::Local<v8::Value> value,
@@ -786,8 +789,9 @@ struct NativeValueTraits<MaybeShared<T>>
 };
 
 template <typename T>
-  requires std::derived_from<T, DOMArrayBufferView>
-struct NativeValueTraits<IDLBufferSourceTypeNoSizeLimit<MaybeShared<T>>>
+struct NativeValueTraits<
+    IDLBufferSourceTypeNoSizeLimit<MaybeShared<T>>,
+    typename std::enable_if_t<std::is_base_of<DOMArrayBufferView, T>::value>>
     : public NativeValueTraitsBase<MaybeShared<T>> {
   // FlexibleArrayBufferView uses this in its implementation, so we cannot
   // delete it.
@@ -802,8 +806,9 @@ struct NativeValueTraits<IDLBufferSource
 };
 
 template <typename T>
-  requires std::derived_from<T, DOMArrayBufferView>
-struct NativeValueTraits<IDLNullable<MaybeShared<T>>>
+struct NativeValueTraits<
+    IDLNullable<MaybeShared<T>>,
+    typename std::enable_if_t<std::is_base_of<DOMArrayBufferView, T>::value>>
     : public NativeValueTraitsBase<MaybeShared<T>> {
   static MaybeShared<T> NativeValue(v8::Isolate* isolate,
                                     v8::Local<v8::Value> value,
@@ -816,9 +821,9 @@ struct NativeValueTraits<IDLNullable<May
 };
 
 template <typename T>
-  requires std::derived_from<T, DOMArrayBufferView>
 struct NativeValueTraits<
-    IDLNullable<IDLBufferSourceTypeNoSizeLimit<MaybeShared<T>>>>
+    IDLNullable<IDLBufferSourceTypeNoSizeLimit<MaybeShared<T>>>,
+    typename std::enable_if_t<std::is_base_of<DOMArrayBufferView, T>::value>>
     : public NativeValueTraitsBase<MaybeShared<T>> {
   // BufferSourceTypeNoSizeLimit must be used only as arguments.
   static MaybeShared<T> NativeValue(v8::Isolate* isolate,
@@ -832,8 +837,11 @@ struct NativeValueTraits<
 };
 
 template <typename T>
-  requires std::derived_from<T, FlexibleArrayBufferView>
-struct NativeValueTraits<T> : public NativeValueTraitsBase<T> {
+struct NativeValueTraits<
+    T,
+    typename std::enable_if_t<
+        std::is_base_of<FlexibleArrayBufferView, T>::value>>
+    : public NativeValueTraitsBase<T> {
   // FlexibleArrayBufferView must be used only as arguments.
   static T NativeValue(v8::Isolate* isolate,
                        v8::Local<v8::Value> value,
@@ -846,8 +854,10 @@ struct NativeValueTraits<T> : public Nat
 };
 
 template <typename T>
-  requires std::derived_from<T, FlexibleArrayBufferView>
-struct NativeValueTraits<IDLBufferSourceTypeNoSizeLimit<T>>
+struct NativeValueTraits<
+    IDLBufferSourceTypeNoSizeLimit<T>,
+    typename std::enable_if_t<
+        std::is_base_of<FlexibleArrayBufferView, T>::value>>
     : public NativeValueTraitsBase<T> {
   // BufferSourceTypeNoSizeLimit and FlexibleArrayBufferView must be used only
   // as arguments.
@@ -862,8 +872,11 @@ struct NativeValueTraits<IDLBufferSource
 };
 
 template <typename T>
-  requires std::derived_from<T, FlexibleArrayBufferView>
-struct NativeValueTraits<IDLNullable<T>> : public NativeValueTraitsBase<T> {
+struct NativeValueTraits<
+    IDLNullable<T>,
+    typename std::enable_if_t<
+        std::is_base_of<FlexibleArrayBufferView, T>::value>>
+    : public NativeValueTraitsBase<T> {
   // FlexibleArrayBufferView must be used only as arguments.
   static T NativeValue(v8::Isolate* isolate,
                        v8::Local<v8::Value> value,
@@ -1199,8 +1212,9 @@ NativeValueTraits<IDLSequence<T>>::Nativ
 }
 
 template <typename T>
-  requires NativeValueTraits<IDLSequence<T>>::has_null_value
-struct NativeValueTraits<IDLNullable<IDLSequence<T>>>
+struct NativeValueTraits<IDLNullable<IDLSequence<T>>,
+                         typename std::enable_if_t<
+                             NativeValueTraits<IDLSequence<T>>::has_null_value>>
     : public NativeValueTraitsBase<HeapVector<AddMemberIfNeeded<T>>*> {
   using ImplType = typename NativeValueTraits<IDLSequence<T>>::ImplType*;
 
@@ -1276,8 +1290,9 @@ struct NativeValueTraits<IDLArray<T>>
     : public NativeValueTraits<IDLSequence<T>> {};
 
 template <typename T>
-  requires NativeValueTraits<IDLSequence<T>>::has_null_value
-struct NativeValueTraits<IDLNullable<IDLArray<T>>>
+struct NativeValueTraits<IDLNullable<IDLArray<T>>,
+                         typename std::enable_if_t<
+                             NativeValueTraits<IDLSequence<T>>::has_null_value>>
     : public NativeValueTraits<IDLNullable<IDLSequence<T>>> {};
 
 // Record types
@@ -1407,8 +1422,10 @@ struct NativeValueTraits<IDLRecord<K, V>
 
 // Callback function types
 template <typename T>
-  requires std::derived_from<T, CallbackFunctionBase>
-struct NativeValueTraits<T> : public NativeValueTraitsBase<T*> {
+struct NativeValueTraits<
+    T,
+    typename std::enable_if_t<std::is_base_of<CallbackFunctionBase, T>::value>>
+    : public NativeValueTraitsBase<T*> {
   static T* NativeValue(v8::Isolate* isolate,
                         v8::Local<v8::Value> value,
                         ExceptionState& exception_state) {
@@ -1431,8 +1448,9 @@ struct NativeValueTraits<T> : public Nat
 };
 
 template <typename T>
-  requires std::derived_from<T, CallbackFunctionBase>
-struct NativeValueTraits<IDLNullable<T>>
+struct NativeValueTraits<
+    IDLNullable<T>,
+    typename std::enable_if_t<std::is_base_of<CallbackFunctionBase, T>::value>>
     : public NativeValueTraitsBase<IDLNullable<T>> {
   static T* NativeValue(v8::Isolate* isolate,
                         v8::Local<v8::Value> value,
@@ -1461,8 +1479,10 @@ struct NativeValueTraits<IDLNullable<T>>
 
 // Callback interface types
 template <typename T>
-  requires std::derived_from<T, CallbackInterfaceBase>
-struct NativeValueTraits<T> : public NativeValueTraitsBase<T*> {
+struct NativeValueTraits<
+    T,
+    typename std::enable_if_t<std::is_base_of<CallbackInterfaceBase, T>::value>>
+    : public NativeValueTraitsBase<T*> {
   static T* NativeValue(v8::Isolate* isolate,
                         v8::Local<v8::Value> value,
                         ExceptionState& exception_state) {
@@ -1486,8 +1506,9 @@ struct NativeValueTraits<T> : public Nat
 
 // Interface types
 template <typename T>
-  requires std::derived_from<T, CallbackInterfaceBase>
-struct NativeValueTraits<IDLNullable<T>>
+struct NativeValueTraits<
+    IDLNullable<T>,
+    typename std::enable_if_t<std::is_base_of<CallbackInterfaceBase, T>::value>>
     : public NativeValueTraitsBase<IDLNullable<T>> {
   static T* NativeValue(v8::Isolate* isolate,
                         v8::Local<v8::Value> value,
@@ -1516,8 +1537,11 @@ struct NativeValueTraits<IDLNullable<T>>
 
 // Dictionary types
 template <typename T>
-  requires std::derived_from<T, bindings::DictionaryBase>
-struct NativeValueTraits<T> : public NativeValueTraitsBase<T*> {
+struct NativeValueTraits<
+    T,
+    typename std::enable_if_t<
+        std::is_base_of<bindings::DictionaryBase, T>::value>>
+    : public NativeValueTraitsBase<T*> {
   static T* NativeValue(v8::Isolate* isolate,
                         v8::Local<v8::Value> value,
                         ExceptionState& exception_state) {
@@ -1528,11 +1552,14 @@ struct NativeValueTraits<T> : public Nat
 // We don't support nullable dictionary types in general since it's quite
 // confusing and often misused.
 template <typename T>
-  requires std::derived_from<T, bindings::DictionaryBase> &&
-           (std::same_as<T, GPUColorTargetState> ||
-            std::same_as<T, GPURenderPassColorAttachment> ||
-            std::same_as<T, GPUVertexBufferLayout>)
-struct NativeValueTraits<IDLNullable<T>> : public NativeValueTraitsBase<T*> {
+struct NativeValueTraits<
+    IDLNullable<T>,
+    typename std::enable_if_t<
+        std::is_base_of<bindings::DictionaryBase, T>::value &&
+        (std::is_same<T, GPUColorTargetState>::value ||
+         std::is_same<T, GPURenderPassColorAttachment>::value ||
+         std::is_same<T, GPUVertexBufferLayout>::value)>>
+    : public NativeValueTraitsBase<T*> {
   static T* NativeValue(v8::Isolate* isolate,
                         v8::Local<v8::Value> value,
                         ExceptionState& exception_state) {
@@ -1544,8 +1571,11 @@ struct NativeValueTraits<IDLNullable<T>>
 
 // Enumeration types
 template <typename T>
-  requires std::derived_from<T, bindings::EnumerationBase>
-struct NativeValueTraits<T> : public NativeValueTraitsBase<T> {
+struct NativeValueTraits<
+    T,
+    typename std::enable_if_t<
+        std::is_base_of<bindings::EnumerationBase, T>::value>>
+    : public NativeValueTraitsBase<T> {
   static T NativeValue(v8::Isolate* isolate,
                        v8::Local<v8::Value> value,
                        ExceptionState& exception_state) {
@@ -1555,8 +1585,10 @@ struct NativeValueTraits<T> : public Nat
 
 // Interface types
 template <typename T>
-  requires std::derived_from<T, ScriptWrappable>
-struct NativeValueTraits<T> : public NativeValueTraitsBase<T*> {
+struct NativeValueTraits<
+    T,
+    typename std::enable_if_t<std::is_base_of<ScriptWrappable, T>::value>>
+    : public NativeValueTraitsBase<T*> {
   // This signifies that CreateIDLSequenceFromV8ArraySlow() may apply
   // certain optimization based on assumptions about `NativeValue()`
   // implementation below. For subclasses of ScriptWrappable that have
@@ -1593,8 +1625,9 @@ struct NativeValueTraits<T> : public Nat
 };
 
 template <typename T>
-  requires std::derived_from<T, ScriptWrappable>
-struct NativeValueTraits<IDLNullable<T>>
+struct NativeValueTraits<
+    IDLNullable<T>,
+    typename std::enable_if_t<std::is_base_of<ScriptWrappable, T>::value>>
     : public NativeValueTraitsBase<IDLNullable<T>> {
   static inline T* NativeValue(v8::Isolate* isolate,
                                v8::Local<v8::Value> value,
@@ -1629,8 +1662,10 @@ struct NativeValueTraits<IDLNullable<T>>
 };
 
 template <typename T>
-  requires std::derived_from<T, bindings::UnionBase>
-struct NativeValueTraits<T> : public NativeValueTraitsBase<T*> {
+struct NativeValueTraits<
+    T,
+    typename std::enable_if_t<std::is_base_of<bindings::UnionBase, T>::value>>
+    : public NativeValueTraitsBase<T*> {
   static T* NativeValue(v8::Isolate* isolate,
                         v8::Local<v8::Value> value,
                         ExceptionState& exception_state) {
@@ -1646,8 +1681,10 @@ struct NativeValueTraits<T> : public Nat
 };
 
 template <typename T>
-  requires std::derived_from<T, bindings::UnionBase>
-struct NativeValueTraits<IDLNullable<T>> : public NativeValueTraitsBase<T*> {
+struct NativeValueTraits<
+    IDLNullable<T>,
+    typename std::enable_if_t<std::is_base_of<bindings::UnionBase, T>::value>>
+    : public NativeValueTraitsBase<T*> {
   static T* NativeValue(v8::Isolate* isolate,
                         v8::Local<v8::Value> value,
                         ExceptionState& exception_state) {
@@ -1668,8 +1705,9 @@ struct NativeValueTraits<IDLNullable<T>>
 
 // Nullable types
 template <typename InnerType>
-  requires(!NativeValueTraits<InnerType>::has_null_value)
-struct NativeValueTraits<IDLNullable<InnerType>>
+struct NativeValueTraits<
+    IDLNullable<InnerType>,
+    typename std::enable_if_t<!NativeValueTraits<InnerType>::has_null_value>>
     : public NativeValueTraitsBase<IDLNullable<InnerType>> {
   // https://webidl.spec.whatwg.org/#es-nullable-type
   using ImplType =
@@ -1701,8 +1739,9 @@ struct NativeValueTraits<IDLNullable<IDL
 
 // Optional types
 template <typename T>
-  requires std::is_arithmetic_v<typename NativeValueTraits<T>::ImplType>
-struct NativeValueTraits<IDLOptional<T>>
+struct NativeValueTraits<IDLOptional<T>,
+                         typename std::enable_if_t<std::is_arithmetic<
+                             typename NativeValueTraits<T>::ImplType>::value>>
     : public NativeValueTraitsBase<typename NativeValueTraits<T>::ImplType> {
   using ImplType = typename NativeValueTraits<T>::ImplType;
 
@@ -1724,8 +1763,9 @@ struct NativeValueTraits<IDLOptional<T>>
 };
 
 template <typename T>
-  requires std::is_pointer_v<typename NativeValueTraits<T>::ImplType>
-struct NativeValueTraits<IDLOptional<T>>
+struct NativeValueTraits<IDLOptional<T>,
+                         typename std::enable_if_t<std::is_pointer<
+                             typename NativeValueTraits<T>::ImplType>::value>>
     : public NativeValueTraitsBase<typename NativeValueTraits<T>::ImplType> {
   using ImplType = typename NativeValueTraits<T>::ImplType;