This method must presume that both INSTANTIATOR and MATCHSPEC are
already validated by the corresponding validate_* methods, and
- may abort if they are invalid.
+ may ABORT if they are invalid.
Return value is an instance, which is returned immediately to the
caller, or Qunbound to continue instantiation lookup chain.
/* #### get image instances out of domains! */
-/* #### I think the following should abort() rather than return nil
+/* #### I think the following should ABORT() rather than return nil
when an invalid domain is given; much more likely we'll catch design
errors early. --ben */