boiler plate class generation, writing fresh variables with macros

[Blake Shaw]

Hiya guilers,

Right now I am working on a window manager extension system in Guile and
GOOPs, and I want to eliminate the boilerplate for generating class slots,
with a syntax-case macro like:

#+begin_example scheme
(define-syntax slot-machine
  (λ (form)
    (syntax-case form ()
      ((_ category quality value)
     #'(let* ((sym      (symbol-append category '- quality))
          (set-sym! (symbol-append 'set- sym '!))
          (get-sym  (symbol-append 'get- sym))
          (acc-sym  (symbol-append 'acc- sym)))
     (quasiquote (,sym #:init-value value
               #:setter     ,set-sym!
               #:getter     ,get-sym
               #:accessor   ,acc-sym))))))
#+end_example

With this I can evaluate (slot-machine 'inner 'color "green") resulting in
what looks like an acceptable slot definition:
=> (inner-color #:init-value "#BF3D52" #:setter set-inner-color! #:getter
get-inner-color #:accessor acc-inner-color)

Indeed, if I define a class with this slot definition in place (ie
manually/without calling the macro), it works fine:
#+begin_example scheme

(define-class <dummy> ()
    (inner-color #:init-value "#BF3D52" #:setter set-inner-color! #:getter
get-inner-color #:accessor acc-inner-color))

(describe <dummy>)
=> <dummy> is a class. It's an instance of <class>
Superclasses are:
    <object>
Directs slots are:
    inner-color
(No direct subclass)
Class Precedence List is:
    <dummy>
    <object>
    <top>
Class direct methods are:
    Method #<<accessor-method> (<dummy> <top>) 7f7b27e10ac0>
         Generic: setter:acc-inner-color
    Specializers: <dummy> <top>
    Method #<<accessor-method> (<dummy>) 7f7b27e10b00>
         Generic: acc-inner-color
    Specializers: <dummy>
    Method #<<accessor-method> (<dummy> <top>) 7f7b27e10b40>
         Generic: set-inner-color!
    Specializers: <dummy> <top>
    Method #<<accessor-method> (<dummy>) 7f7b27e10b80>
         Generic: get-inner-color
    Specializers: <dummy>
#+end_example

But if I try to use `slot-machine` inside a class definition i'm out of
luck:

(define-class <dummy> ()
  (slot-machine 'inner 'color "green"))
=> While compiling expression:
Syntax error:
socket:7257:0: source expression failed to match any pattern in form
(define-class-pre-definition ((quote inner) (quote color) "green"))

I have tried to remedy this ina number of ways, using datum->syntax,
quasisyntax/unsyntax, make-variable and by defining a new syntax-case macro
to define classes, all without luck.

This is actually a recurring theme with my experience with Guile, working
on a project, needing to generate boilerplate, and then being unable to
find a result, so I figured its time I reach out to figure out what I'm
doing wrong in this situation.

Thanks for your help!

Best,
Blake