Levente pointed out that while Cog has this primitive, the Interpreter VM doesn't, and so his Inbox submission (http://source.squeak.org/inbox/System-ul.528.mcz) can't really go into Trunk yet.
Given that this is something that I feel strongly about - I need this primitive so that builds will actually _fail_ and not continue trying random things on things in random states - it seems likely that I'll be the one to implement the thing.
SO. How might I go about porting the Cog version? Do I simply start to Read the Source?
frank