protected Shape transitionWithNewField(Shape oldShape, Object value) { // This duplicates quite a bit of DynamicObject.define(), but should be fixed in Truffle soon. final Property oldProperty = oldShape.getProperty(name); if (oldProperty != null) { if (oldProperty.getFlags() == 0 && oldProperty.getLocation().canSet(null, value)) { return oldShape; // already the right shape } else { DynamicObject copy = oldShape.getLayout().newInstance(oldShape); copy.define(name, value, 0); return copy.getShape(); } } else { final Location location = oldShape .allocator() .locationForValue( value, EnumSet.of(LocationModifier.Final, LocationModifier.NonNull)); final Property newProperty = Property.create(name, location, 0); return oldShape.addProperty(newProperty); } }