Make sure api interceptors don't change the store target w/o storing

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index a5da88a0b3b2e0b5e44b17e0918d17655ea38e09..d3212c64fe945dddb472bb7017dec53131d4057b 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -4309,10 +4309,19 @@ Maybe<bool> Object::SetPropertyInternal(LookupIterator* it,
 
       case LookupIterator::INTERCEPTOR:
         if (it->HolderIsReceiverOrHiddenPrototype()) {
+          Handle<Map> store_target_map =
+              handle(it->GetStoreTarget()->map(), it->isolate());
           Maybe<bool> result =
               JSObject::SetPropertyWithInterceptor(it, should_throw, value);
           if (result.IsNothing() || result.FromJust()) return result;
+          // Interceptor modified the store target but failed to set the
+          // property.
+          Utils::ApiCheck(*store_target_map == it->GetStoreTarget()->map(),
+                          it->IsElement() ? "v8::IndexedPropertySetterCallback"
+                                          : "v8::NamedPropertySetterCallback",
+                          "Interceptor silently changed store target.");
         } else {
+          Handle<JSObject> store_target = it->GetStoreTarget();
           Maybe<PropertyAttributes> maybe_attributes =
               JSObject::GetPropertyAttributesWithInterceptor(it);
           if (!maybe_attributes.IsJust()) return Nothing<bool>();
@@ -4320,6 +4329,12 @@ Maybe<bool> Object::SetPropertyInternal(LookupIterator* it,
           if ((maybe_attributes.FromJust() & READ_ONLY) != 0) {
             return WriteToReadOnlyProperty(it, value, should_throw);
           }
+          // Interceptor modified the store target but failed to set the
+          // property.
+          Utils::ApiCheck(*store_target == *it->GetStoreTarget(),

[Toon Verwaest, 2016/06/21 13:09:24]

Don't you want to do exactly the same check in both cases?

+                          it->IsElement() ? "v8::IndexedPropertySetterCallback"
+                                          : "v8::NamedPropertySetterCallback",
+                          "Interceptor silently changed store target.");
           *found = false;
           return Nothing<bool>();
         }