Welcome to the CHICKEN Scheme pasting service

;; Broken version
(let-syntax
    ((foo (syntax-rules ()
            ((_)
             (letrec-syntax
                 ((bar (er-macro-transformer
                        (lambda (e r c)
                          (if (= (cadr e) 0)
                              0
                              `(,(r '+) 1 (,(r 'bar) ,(- (cadr e) 1))))))))
               (bar 5))))))
  (foo))

;; Correct version
(let-syntax
    ((foo (syntax-rules ()
            ((_)
             (letrec-syntax
                 ((bar (er-macro-transformer
                        (lambda (e r c)
                          (if (= (caddr e) 0)
                              0
                              `(,(r '+) 1 (,(cadr e) ,(cadr e)
                                           ,(- (caddr e) 1))))))))
               (bar bar 5))))))
  (foo))

(let-syntax ((foo (syntax-rules ()
                    ((_)
                     (letrec-syntax
                         ((bar (macro-rules ()
                                 ((_ recur x) (where (= x 0)) 0)
                                 ((_ recur x) `(+ 1 (,recur ,recur ,(- x 1)))))))
                       (bar bar 5))))))
  (foo))

;; Much more fun: no need to pass the macro its own name
(let-syntax ((foo (syntax-rules ()
                    ((_)
                     (letrec-syntax
                         ((bar (syntax-rules .. ()
                                 ((_) 0)
                                 ((_ x rest ..) (+ 1 (bar rest ..))))))
                       (bar 1 2 3 4 5))))))
  (foo))