[Chicken-janitors] #1362: A case when composing with ir-macro-transformer

[Chicken Trac]

#1362: A case when composing with ir-macro-transformer
---------------------------------+--------------------------------
 Reporter:  megane               |                 Owner:
     Type:  defect               |                Status:  new
 Priority:  not urgent at all    |             Milestone:  someday
Component:  expander             |               Version:  4.12.0
 Keywords:  ir-macro-trasformer  |  Estimated difficulty:
---------------------------------+--------------------------------
 I ran into this unexpected behaviour when using ir macros in ir macros. I
 don't think this should happen:

  (I have tested this with 4.12, not with 5. )

  First macro:
  {{{#!scheme
  (define-syntax bind-pair
    (ir-macro-transformer
     (lambda (e i c)
       (let* ((b (second e))
              (exp (third e))
              (body (drop e 3)))
         `(let* ((x ,exp)
                 (,(first b) (car x))
                 (,(second b) (cdr x)))
            ,@body)))))
 }}}

  Testing:

 {{{
  (bind-pair (x y) (cons 1 2) (print y))

  => prints 2
 }}}

  Now a second macro using bind-pair:

 {{{#!scheme
  (define-syntax foo
    (ir-macro-transformer
     (lambda (e i c)
       `(bind-pair (x y) (cons 'foo-car 'b) (print y)))))
 }}}

  Running (foo) gives the error:

  Error: (cdr) bad argument type: foo-car

  The expansion of (foo) looks like this:

 {{{
  ;; (##core#let
  ;;   ((x40 (cons42 (quote43 foo-car44) (quote43 b45))))
  ;;   (##core#let
  ;;     ((x40 (car48 x40)))
  ;;     (##core#let ((y41 (cdr49 x40))) (##core#let () (print46 y41)))))
  }}}

  As you can see, the x in bind-pair and foo macros refer to the same
  variable in the expansion. You can confirm this happens by changing the
  x in foo to, say z.

--
Ticket URL: <https://bugs.call-cc.org/ticket/1362>
CHICKEN Scheme <https://www.call-cc.org/>
CHICKEN Scheme is a compiler for the Scheme programming language.