(Don't ask me why or how I got here, but ...) I came across a very old (Nov 1980) post in a mailing list that might be related to our current confusion on the different interpretations of what types mean:
The second way is to keep careful tabs on what functions call this one and the way that they have to be changed to match changes in this function. It is exactly this latter type of control (auditing function) that I mean should be included in NIL (or whatever). I am not against extending the language any more than I am against GOTOs (which is not very much).