>>>> Would it be possible to rename the primitive Object>>class to
>>>> Object>>basicClass, and then implement Object>>class as:
>>>
>>> In many Smalltalks, you can't override #class. Squeak is one of 
>>> those --
>>> you can comment out the primitive call in Object >> #class, and 
>>> everything
>>> still works fine. The compiler short-circuits the message, and just 
>>> answers
>>> the class (or something like that).
>>
>> I once did something similar: you can remove #class from the 
>> special-selectors collection in the compiler (class-var StdSelectors 
>> in ParseNode). From then on all methods you compile actually send the 
>> message #class and therefor it can also be overridden.
>
> Oh, it's not in the VM - good.  Markus, does the new Compiler package 
> still have this?  Can we get rid of it?

Well, it is in both, the VM and the compiler. There are special 
byte-codes for selectors like #class, #at:, #<=, etc. That's also why 
these selectors never appear in the literal-frame of a method. So 
obviously the VM does directly push the class onto the stack, when 
processing the #class-byte-code. If you tell the compiler not to emit 
this special byte-code (as explained above), but the standard 
message-send-byte-code, there is no optimization of the VM going on.

Lukas

-- 
Lukas Renggli
http://www.lukas-renggli.ch