ok I see this is the oneWayBecome: of VW.

>> stéphane> Hi brent
>> stéphane> I'm not sure but in VW it is advised to do
>>
>> stéphane>       i become: String new    and not i become: nil
>>
>> stéphane> The point explained to me was that  else you will have a 
>> lot of
>> stéphane> pointer pointing to nil while you would prefer to have them 
>> pointing
>> stéphane> on fresh objects that will be garbagecollected.
>>
>> Well, in some VMs, "become:" is a swap, not unidirectional.  "become: 
>> nil"
>> would be a very very very (...) very bad thing to do.
>
> Yes, that's true in Squeak as well.  You want #becomeForward:.
>
> Avi
>
>