Recursive flatten syntax-rules macro crashes NodeJS

[jcubic]

This is the result of running macro:

(define-syntax flatten
  (syntax-rules (aux reverse)
    ((_ xs)
     (flatten aux xs ()))
    ((_ aux ((xs ...) ys ...) (result ...))
     (flatten aux (xs ... ys ...) (result ...)))
    ((_ aux (x xs ...) (result ...))
     (flatten aux (xs ...) (x result ...)))
    ((_ aux () (result ...))
     (flatten reverse (result ...) ()))
    ((_ reverse () (result ...))
     '(result ...))
    ((_ reverse (x xs ...) (result ...))
     (flatten reverse (xs ...) (x result ...)))))

(print (flatten ((1 2 (a b) (c d)) (3 4 (e f) (g h)))))

Bun on the other hand creates a very long expansion and probably throws StackOverflow: