Structure* Structure::removePropertyTransition(VM& vm, Structure* structure, PropertyName propertyName, PropertyOffset& offset)
{
// NOTE: There are some good reasons why this goes directly to uncacheable dictionary rather than
// caching the removal. We can fix all of these things, but we must remember to do so, if we ever try
// to optimize this case.
//
// - Cached transitions usually steal the property table, and assume that this is possible because they
// can just rebuild the table by looking at past transitions. That code assumes that the table only
// grew and never shrank. To support removals, we'd have to change the property table materialization
// code to handle deletions. Also, we have logic to get the list of properties on a structure that
// lacks a property table by just looking back through the set of transitions since the last
// structure that had a pinned table. That logic would also have to be changed to handle cached
// removals.
//
// - InferredTypeTable assumes that removal has never happened. This is important since if we could
// remove a property and then re-add it later, then the "absence means top" optimization wouldn't
// work anymore, unless removal also either poisoned type inference (by doing something equivalent to
// hasBeenDictionary) or by strongly marking the entry as Top by ensuring that it is not absent, but
// instead, has a null entry.
ASSERT(!structure->isUncacheableDictionary());
Structure* transition = toUncacheableDictionaryTransition(vm, structure);
offset = transition->remove(propertyName);
transition->checkOffsetConsistency();
return transition;
}
Structure* Structure::removePropertyTransition(JSGlobalData& globalData, Structure* structure, PropertyName propertyName, PropertyOffset& offset)
{
ASSERT(!structure->isUncacheableDictionary());
Structure* transition = toUncacheableDictionaryTransition(globalData, structure);
offset = transition->remove(propertyName);
return transition;
}
Structure* Structure::removePropertyTransition(VM& vm, Structure* structure, PropertyName propertyName, PropertyOffset& offset)
{
ASSERT(!structure->isUncacheableDictionary());
Structure* transition = toUncacheableDictionaryTransition(vm, structure);
offset = transition->remove(propertyName);
transition->checkOffsetConsistency();
return transition;
}
