Remove bogus writability check in DefineGetterSetter.

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index 2b6f2352ae647b5a2eec0b7461caa3aeab50b8a2..fac8b5bd876c662e02680aa53e81bd9a721581c9 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -4257,10 +4257,9 @@ void JSObject::LookupCallback(String* name, LookupResult* result) {
 
 
 // Search for a getter or setter in an elements dictionary and update its
-// attributes.  Returns either undefined if the element is read-only, or the
-// getter/setter pair (fixed array) if there is an existing one, or the hole
-// value if the element does not exist or is a normal non-getter/setter data
-// element.
+// attributes.  Returns either the getter/setter pair (fixed array) if there
+// is an existing one, or the hole value if the element does not exist or is
+// a normal non-getter/setter data element.
 static Object* UpdateGetterSetterInDictionary(NumberDictionary* dictionary,
                                               uint32_t index,
                                               PropertyAttributes attributes,
@@ -4269,7 +4268,6 @@ static Object* UpdateGetterSetterInDictionary(NumberDictionary* dictionary,
   if (entry != NumberDictionary::kNotFound) {
     Object* result = dictionary->ValueAt(entry);
     PropertyDetails details = dictionary->DetailsAt(entry);
-    if (details.IsReadOnly()) return heap->undefined_value();

[rossberg, 2011/12/16 12:03:36]

IsReadOnly clearly is the wrong check here. But I suggest adding a check for
IsConfigurable (as an assertion?).

Please also document configurability as a pre-condition.

[Michael Starzinger, 2011/12/16 12:38:02]

Done. As discussed offline: The correct check here would be to check for
details.IsDontDelete() and return undefined if the property is non-deletable.
But since we call into the runtime twice (once for getter and once for setter),
we cannot do that yet. Left a TODO comment that explains the situation.

We should define both (getter and setter) in one single runtime call and then
add the correct check here.

     if (details.type() == CALLBACKS && result->IsFixedArray()) {
       if (details.attributes() != attributes) {
         dictionary->DetailsAtPut(entry,
@@ -4353,7 +4351,6 @@ MaybeObject* JSObject::DefineGetterSetter(String* name,
     LookupResult result(heap->isolate());
     LocalLookup(name, &result);
     if (result.IsProperty()) {
-      if (result.IsReadOnly()) return heap->undefined_value();
       if (result.type() == CALLBACKS) {
         Object* obj = result.GetCallbackObject();
         // Need to preserve old getters/setters.