;; a.scm
(declare (unit a))

(import r7rs)

(define-library (a)
  (import (scheme base)
          (scheme write))
  (export do-it)

  (begin
    (define (do-it)
      (display "I did it.")
      (newline))

    ))

;; b.scm
(declare (unit b))
(declare (uses a))

(import r7rs)

(define-library (b)
  (import (scheme base) (a))
  (export foo)

  (begin
    (define (foo)
      (do-it))

    ))

;; z.scm
(declare (uses a b))

(import r7rs)

(define-library (z)
  (import (scheme base) (b))
  (export baz)

  (begin
    (define (baz)
      (foo))

    ))

(import (z))
(baz)