Trying to nest a helper inside a macro...

nest.ss

#lang racket
(define-syntax defsyntax (syntax-rules () ((_ x ...) (define-syntax x ...))))

;; These two work:
(defsyntax Rnest
  (syntax-rules ()
    ((_ (rev ...) (one more ...)) (Rnest (one rev ...) (more ...)))
    ((_ () ()) ())
    ((_ (x) ()) x)
    ((_ (x (y ...) z ...) ()) (Rnest ((y ... x) z ...) ()))))

(defsyntax nest
  (syntax-rules ()
    ((_ x ...) (Rnest () (x ...)))))

(write (nest (quote) (a b) (c d) (e) f)) (newline) ;;=> prints: (a b (c d (e f)))


;; I tried to make Rnest a local macro, but failed with an error as follows
;; the position given being after the first z:
;; syntax: no pattern variables before ellipsis in template
(defsyntax nest
  (syntax-rules ()
    ((_ x ...)
     (let-syntax
         ((r
           (syntax-rules ()
             ((_ (x ...) (y z ...)) (r (y x ...) (z ...))) ;; reverse the list
             ((_ (x (y ...) z ...) ()) (r ((y ... x) z ...) ())))) ;; nest
             ((_ (x) ()) x)) ;; bottom case
       (r () (x ...))))))

;; I tried unhoisting the let-syntax, and only got this errors in the last r with: r: unbound identifier in module
(defsyntax nest
  (let-syntax
      ((r
        (syntax-rules ()
          ((_ (x ...) (y z ...)) (r (y x ...) (z ...))) ;; reverse the list
          ((_ (x (y ...) z ...) ()) (r ((y ... x) z ...) ())) ;; nest
          ((_ (x) ()) x)))) ;; bottom case
    (syntax-rules ()
      ((_ x ...) (r () (x ...))))))