Hi Nicolai,

On Jul 26, 2016, at 6:33 AM, Nicolai Hess <nicolaihess@gmail.com> wrote:

2016-07-26 15:08 GMT+02:00 Denis Kudriashov <dionisiydk@gmail.com>:
Hi.

Look at UndefinedObject instance side methods. You will see class hierarchy protocol. For example nil understands #subclasses message:

nil subclasses "==> {ProtoObject}"

ProtoObjects superclass is nil, so maybe it just should behave the same way for all other objects.

ByteString superclass subclasses includes: ByteString. "true"

ProtoObject superclass subclasses includes: ProtoObject. "true"

Sorry to sound harsh but that's no sense. ProtoObject doesn't have a superclass. This is indicated by ProtoObject superclass answering nil, where nil is the object that represents being undefined.

It is (as Denis points out) a bug, showing some confusion, to try and program around this one case by adding class protocol to the undefined object. A horrible hack.

Denis, you're right; that behaviour should be deleted.

It implemented like this:

UndefinedObject >>subclassesDo: aBlock
"Evaluate aBlock with all subclasses of nil. Others are not direct subclasses of Class."

^ Class subclassesDo: [:cl |
cl isMeta ifTrue: [aBlock value: cl soleInstance]].

So my question is: why it needs to be like that? And does it really needed?

I removed all this methods and not saw any problem.