;; foo.scm
(define-syntax foo
  (er-macro-transformer
   (lambda (x r t) `(print "debug: " ##sys#current-source-filename))))

(foo 123)

;; bash:
$ csc foo.scm && ./foo
debug: #f

;; ^ got
;; expected:
debug: foo.scm:3

;; does not work when ##sys#current-source-filename is unquoted in macro either.