You see, now I got it :)  I am just slow.
Thanks Henrik for this example. In fact, it was not even obvious for me until you told me. The "problem" is that the bytecodes to access/set instanceVariables work by position instead of name, no?
I mean, 'one' is never put in the literals of A >> #foo

Nevertheless, exactly the same happens with #valueWithReceiver:arguments:    so...ok, we have this problem but we also have from before ;)
right ?

solutions?

First I would put a nice comment in #valueWithReceiver:arguments:   and #valueWithReceiver:arguments: 

Second, if I understood you correctly you mean to do in your previous email, you want to validate that the class of the receiver is the same as the class where the CompiledMethod is installed and if it is not, throw an error ?

On the one hand that would limit a bit the usage because that fails only when there is instance var access, doesn't it?  On the other hand, it prevents some crashes or weird cases where the results are not the expected ones.

Opinions?