Filtering calls

[Steven <Handerson@CMU-CS-C.ARPA>]

The current language definition seems to have a small problem.
I'll follow through a hack example - anyone with any imagination should see the
problem (whether my example means anything is a separate issue).

Let's assume that you have to write (VAR X) instead of X to reference a given
variable (and, for convenience, that everything works like SETF).  The global
macro for VAR does the normal variable thing.

DEFMETHOD could then *filter* through the calls to VAR for those of instance
variables, replacing them with calls to a macro IV, and leaving the rest for
the global macro.  How can we set up such a filter?  We can't just deal with
the global definition, because someone might want to filter the remaining VARs
in some code wrapped around ours.  Macrolet would cause the remaining VARs to
be examined again and again...  I think we need some way to deal with expansion
functions explicitly, but I'm not sure.

-- Steve