Add a native data property that replaces itself with a real data property

src/objects.cc

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/objects.h"
 
 #include <cmath>
 #include <iomanip>
 #include <memory>
 #include <sstream>
@@ skipping 1334 matching lines @@
       ASSIGN_RETURN_ON_EXCEPTION(isolate, receiver,
                                  Object::ConvertReceiver(isolate, receiver),
                                  Object);
     }
 
     PropertyCallbackArguments args(isolate, info->data(), *receiver, *holder,
                                    Object::DONT_THROW);
     Handle<Object> result = args.Call(call_fun, name);
     RETURN_EXCEPTION_IF_SCHEDULED_EXCEPTION(isolate, Object);
     if (result.is_null()) return isolate->factory()->undefined_value();
-    // Rebox handle before return.
-    return handle(*result, isolate);
+    Handle<Object> reboxed_result = handle(*result, isolate);
+    if (info->replace_on_access() && receiver->IsJSReceiver()) {
+      args.Call(reinterpret_cast<GenericNamedPropertySetterCallback>(
+                    &Accessors::ReconfigureToDataProperty),
+                name, result);
+      RETURN_EXCEPTION_IF_SCHEDULED_EXCEPTION(isolate, Object);
+    }
+    return reboxed_result;
   }
 
   // Regular accessor.
   Handle<Object> getter(AccessorPair::cast(*structure)->getter(), isolate);
   if (getter->IsFunctionTemplateInfo()) {
     return Builtins::InvokeApiFunction(
         isolate, false, Handle<FunctionTemplateInfo>::cast(getter), receiver, 0,
         nullptr, isolate->factory()->undefined_value());
   } else if (getter->IsCallable()) {
     // TODO(rossberg): nicer would be to cast to some JSCallable here...
@@ skipping 18884 matching lines @@
         ns, Accessors::ModuleNamespaceEntryInfo(isolate, name, attr))
         .Check();
   }
   JSObject::PreventExtensions(ns, THROW_ON_ERROR).ToChecked();
 
   return ns;
 }
 
 }  // namespace internal
 }  // namespace v8