Tried this same solution out in VW 2.5 this morning. Interestingly the
Point>>x case crashes there too. The primitive #valueWithReceiver:arguments:
(of course) works correctly.

For the record, the primitive is about 12 times slower than the regular
accessor in VW, so the 100% Squeak (15 times without tests) code seems to be
doing relatively well at first sight. The overhead in Squeak grows to 24
times (without tests) if we use a do: loop. VW remains constant. Even so, it
is difficult to compare things as the basic VW accessor code in a loop (....
timesRepeat: [ p x ] where p a point) is about 20 times faster than the
Squeak equivalent. And in real applications absolute benchmarks sometimes
have a very relative impact.

michel