read-all receiving #<unspecified> unless preceded by a predicate

[sjamaan]

This happens in csi:

;; This works:
(require-extension utils)

(define (command/string command)
  (define-values (proc-output proc-input proc-id) (process command))
  (port? proc-output)
  (define retval (read-all proc-output))
  (close-input-port proc-output)
  (close-output-port proc-input)
  retval)

(print (command/string "ls"))

;; This breaks:

(require-extension utils)

(define (command/string command)
  (define-values (proc-output proc-input proc-id) (process command))
  (define retval (read-all proc-output))
  (close-input-port proc-output)
  (close-output-port proc-input)
  retval)

(print (command/string "ls"))

;; Gives us:
;; Error: (open-input-file) bad argument type - not a string: #<unspecified>

[evhan]

Transcribed from IRC: basically, ##sys#canonicalize-body reorders
internal definitions so that multi-valued assignments always follow
normal ones. The result is always a bunch of let bindings to introduce
the vars followed by a bunch of ##core#set! nodes to assign them,
but the normal and multi-valued var/val pairs are accumulated in
separate lists so the ordering gets lost. Then, the templating just
blindly puts the multi-valued ##core#sets! after the others.
Currently, the "dimensions" of the lists are different, so to speak --
in the code, vars/vals gets a list of variables/expressions, whereas
mvars/mvals gets a list of lists of variables/expressions -- and
mvars/mvals has to be processed a bit more to produce a c-w-v.

[evhan]

Fixed by 469f2bb / 6992762.