🚀 go-pugleaf

;; This a perfectly valid, if somewhat unusual lisp function,
;; simplified from actual code I wrote:

(defun foo (fn-list)			; type M-C-x here
  (mapcar				; to define foo 
   (function				
    (lambda (FROM)
      ((lambda (FROM-1 TO) (list FROM-1 TO 0))
       (concat "/" FROM)	; FROM-1
       (concat "/tmp/" (file-name-nondirectory FROM)) ; TO
       )))
   fn-list))

(foo '("a" "b"))

;; Type C-x C-e at the beginning of this line to validate that foo
;; executes without errors, producing
;; (("/a" "/tmp/a" 0) ("/b" "/tmp/b" 0))

(byte-compile 'foo)

;; Type C-x C-e at the beginning of this line to get this error:
;; (wrong-type-argument symbolp (lambda (FROM-1 TO) (list FROM-1 TO 0)))

;; If you first load the uncompiled version of "bytecomp.el",
;; the backtrace is more readable:

;;get((lambda (FROM-1 TO) (list FROM-1 TO 0)) byte-compile)
;;  (let ...)
;;  (cond ...)
;;  byte-compile-form(((lambda (FROM-1 TO) (list FROM-1 TO 0))
;;		     (concat default-directory FROM)
;;		     (concat "/" (file-name-nondirectory FROM))))   

;; Thus byte-compile-form bombs on nested lambda functions.  It should
;; probably call itself recursively for nested lambdas.
;; The problem vanishes if you use quote instead of function to quote the
;; nested lambda function, because then it will not be byte-compiled at all.
--

Sebastian Kremer <sk@thp.Uni-Koeln.DE>
Institute of Theoretical Physics, University of Cologne, F. R. of Germany