---- Mark H Weaver <mhw@netris.org> wrote: 

The proper solution is as follows:

* Every generic function must be defined (using 'define-generic') and
  exported from one (and only one) module.

* Every module that uses a generic function, or adds a method to it (and
  that includes slot accessors), must first import the generic function
  from the (one) module that exports it.

Think of a generic function as a normal procedure that contains an
internal table of methods.  Like any other procedure, there's a single
module that defines it and exports it.  The fact that some modules add
methods to these internal tables does not mean that it is appropriate to
export the procedure from those other modules.

Thanks Mark.  Very concisely put.