[es6] Partially implement Reflect.preventExtensions.

src/objects.cc

 // Copyright 2013 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 <sstream>
 
@@ skipping 6700 matching lines @@
 
       return context->extension_object()->ReferencesObject(obj);
     }
   }
 
   // No references to object.
   return false;
 }
 
 
-Maybe<bool> JSObject::PreventExtensionsInternal(Handle<JSObject> object) {
+#define RETURN_FAILURE(isolate, should_throw, call) \
+  do {                                              \
+    if ((should_throw) == DONT_THROW) {             \
+      return Just(false);                           \
+    } else {                                        \
+      isolate->Throw(*isolate->factory()->call);    \
+      return Nothing<bool>();                       \
+    }                                               \
+  } while (false)
+
+
+Maybe<bool> JSReceiver::PreventExtensions(Handle<JSReceiver> object,
+                                          ShouldThrow should_throw) {
+  if (!object->IsJSObject()) return Just(false);  // TODO(proxies)

[rossberg, 2015/10/19 14:33:08]

Style nit: TODO(neis): what

[neis, 2015/10/20 07:58:35]

Done.

+  return JSObject::PreventExtensions(Handle<JSObject>::cast(object),
+                                     should_throw);
+}
+
+
+Maybe<bool> JSObject::PreventExtensions(Handle<JSObject> object,
+                                        ShouldThrow should_throw) {
   Isolate* isolate = object->GetIsolate();
 
   if (!object->map()->is_extensible()) return Just(true);
 
   if (!object->HasSloppyArgumentsElements() && !object->map()->is_observed()) {
-    return PreventExtensionsWithTransition<NONE>(object);
+    return PreventExtensionsWithTransition<NONE>(object, should_throw);
   }
 
   if (object->IsAccessCheckNeeded() &&
       !isolate->MayAccess(handle(isolate->context()), object)) {
     isolate->ReportFailedAccessCheck(object);
     RETURN_VALUE_IF_SCHEDULED_EXCEPTION(isolate, Nothing<bool>());
     UNREACHABLE();
-    return Just(false);
+    RETURN_FAILURE(isolate, should_throw,
+                   NewTypeError(MessageTemplate::kNoAccess));
   }
 
   if (object->IsJSGlobalProxy()) {
     PrototypeIterator iter(isolate, object);
     if (iter.IsAtEnd()) return Just(true);
     DCHECK(PrototypeIterator::GetCurrent(iter)->IsJSGlobalObject());
-    return PreventExtensionsInternal(
-        PrototypeIterator::GetCurrent<JSObject>(iter));
+    return PreventExtensions(PrototypeIterator::GetCurrent<JSObject>(iter),
+                             should_throw);
   }
 
   // It's not possible to seal objects with external array elements
   if (object->HasFixedTypedArrayElements()) {
     isolate->Throw(*isolate->factory()->NewTypeError(
         MessageTemplate::kCannotPreventExtExternalArray));
     return Nothing<bool>();
   }
 
   // If there are fast elements we normalize.
@@ skipping 16 matching lines @@
     RETURN_ON_EXCEPTION_VALUE(
         isolate,
         EnqueueChangeRecord(object, "preventExtensions", Handle<Name>(),
                             isolate->factory()->the_hole_value()),
         Nothing<bool>());
   }
   return Just(true);
 }
 
 
-static MaybeHandle<Object> ReturnObjectOrThrowTypeError(
-    Handle<JSObject> object, Maybe<bool> maybe, MessageTemplate::Template msg) {
-  if (!maybe.IsJust()) return MaybeHandle<Object>();
-  if (maybe.FromJust()) return object;
-  Isolate* isolate = object->GetIsolate();
-  THROW_NEW_ERROR(isolate, NewTypeError(msg), Object);
-}
-
-
-MaybeHandle<Object> JSObject::PreventExtensions(Handle<JSObject> object) {
-  return ReturnObjectOrThrowTypeError(object, PreventExtensionsInternal(object),
-                                      MessageTemplate::kCannotPreventExt);
-}
-
-
 bool JSObject::IsExtensible(Handle<JSObject> object) {
   Isolate* isolate = object->GetIsolate();
   if (object->IsAccessCheckNeeded() &&
       !isolate->MayAccess(handle(isolate->context()), object)) {
     return true;
   }
   if (object->IsJSGlobalProxy()) {
     PrototypeIterator iter(isolate, *object);
     if (iter.IsAtEnd()) return false;
     DCHECK(iter.GetCurrent()->IsJSGlobalObject());
@@ skipping 21 matching lines @@
       }
       details = details.CopyAddAttributes(
           static_cast<PropertyAttributes>(attrs));
       dictionary->DetailsAtPut(i, details);
     }
   }
 }
 
 
 template <PropertyAttributes attrs>
-Maybe<bool> JSObject::PreventExtensionsWithTransition(Handle<JSObject> object) {
+Maybe<bool> JSObject::PreventExtensionsWithTransition(
+    Handle<JSObject> object, ShouldThrow should_throw) {
   STATIC_ASSERT(attrs == NONE || attrs == SEALED || attrs == FROZEN);
 
   // Sealing/freezing sloppy arguments should be handled elsewhere.
   DCHECK(!object->HasSloppyArgumentsElements());
   DCHECK(!object->map()->is_observed());
 
   Isolate* isolate = object->GetIsolate();
   if (object->IsAccessCheckNeeded() &&
       !isolate->MayAccess(handle(isolate->context()), object)) {
     isolate->ReportFailedAccessCheck(object);
     RETURN_VALUE_IF_SCHEDULED_EXCEPTION(isolate, Nothing<bool>());
     UNREACHABLE();
+    RETURN_FAILURE(isolate, should_throw,
+                   NewTypeError(MessageTemplate::kNoAccess));
   }
 
   if (object->IsJSGlobalProxy()) {
     PrototypeIterator iter(isolate, object);
     if (iter.IsAtEnd()) return Just(true);
     DCHECK(PrototypeIterator::GetCurrent(iter)->IsJSGlobalObject());
     return PreventExtensionsWithTransition<attrs>(
-        PrototypeIterator::GetCurrent<JSObject>(iter));
+        PrototypeIterator::GetCurrent<JSObject>(iter), should_throw);
   }
 
   // It's not possible to seal or freeze objects with external array elements
   if (object->HasFixedTypedArrayElements()) {
     isolate->Throw(*isolate->factory()->NewTypeError(
         MessageTemplate::kCannotPreventExtExternalArray));
     return Nothing<bool>();
   }
 
   Handle<SeededNumberDictionary> new_element_dictionary;
@@ skipping 66 matching lines @@
     if (attrs != NONE) {
       ApplyAttributesToDictionary(dictionary, attrs);
     }
   }
 
   return Just(true);
 }
 
 
 MaybeHandle<Object> JSObject::Freeze(Handle<JSObject> object) {
-  return ReturnObjectOrThrowTypeError(
-      object, PreventExtensionsWithTransition<FROZEN>(object),
-      MessageTemplate::kCannotPreventExt);
+  ASSIGN_OR_RETURN(bool, result, PreventExtensionsWithTransition<FROZEN>(
+                                     object, THROW_ON_ERROR),
+                   MaybeHandle<Object>());
+  return object;
 }
 
 
 MaybeHandle<Object> JSObject::Seal(Handle<JSObject> object) {
-  return ReturnObjectOrThrowTypeError(
-      object, PreventExtensionsWithTransition<SEALED>(object),
-      MessageTemplate::kCannotPreventExt);
+  ASSIGN_OR_RETURN(bool, result, PreventExtensionsWithTransition<SEALED>(
+                                     object, THROW_ON_ERROR),
+                   MaybeHandle<Object>());
+  return object;
 }
 
 
 void JSObject::SetObserved(Handle<JSObject> object) {
   DCHECK(!object->IsJSGlobalProxy());
   DCHECK(!object->IsJSGlobalObject());
   Isolate* isolate = object->GetIsolate();
   Handle<Map> new_map;
   Handle<Map> old_map(object->map(), isolate);
   DCHECK(!old_map->is_observed());
@@ skipping 10699 matching lines @@
   if (cell->value() != *new_value) {
     cell->set_value(*new_value);
     Isolate* isolate = cell->GetIsolate();
     cell->dependent_code()->DeoptimizeDependentCodeGroup(
         isolate, DependentCode::kPropertyCellChangedGroup);
   }
 }
 
 }  // namespace internal
 }  // namespace v8