Comment 0 for bug 520877

as briefly discussed on SBCL10, with a relatively simple extension it could be possible to avoid degrading the performance of slot-value when a custom svuc is defined.

the idea is to have a MOP extension, a generic method called something like compute-slot-value-using-class-form, that libraries can customize on SBCL to build the SVUC body and then the current optimizations can kick in.

this would mean a 10-fold speed-up in many of our customizations.