Comment 4 for bug 309072

Reviewing the patch in comment #3:

* I would use &key (name nil namep) rather than the member
  test in the lambda list;
* the error should be a reference condition, using
  '(:amop :initialization slot-definition) as one of the references;
* if we're going to do this, we should at least try to perform all
  the intialization checks referred to at once;
* I'm not worried about the slowdown; I don't think the bottleneck
  in any application is likely to be the creation of slotds.