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eval-when matches situations symbolically

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* module/ice-9/psyntax.scm (chi-when-list): Just match symbolically
  instead of lexically, so as not to tie the meaning of eval-when to the
  bindings of eval, load, compile, and expand.
This commit is contained in:
Andy Wingo 2011-04-29 16:36:10 +02:00
parent 5138551787
commit aa5698fb53
1 changed files with 11 additions and 10 deletions
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21
module/ice-9/psyntax.scm
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@ -1066,20 +1066,21 @@
(define chi-when-list
(lambda (e when-list w)
;; when-list is syntax'd version of list of situations
;; `when-list' is syntax'd version of list of situations. We
;; could match these keywords lexically, via free-id=?, but then
;; we twingle the definition of eval-when to the bindings of
;; eval, load, expand, and compile, which is totally unintended.
;; So do a symbolic match instead.
(let f ((when-list when-list) (situations '()))
(if (null? when-list)
situations
(f (cdr when-list)
(cons (let ((x (car when-list)))
(cond
((free-id=? x #'compile) 'compile)
((free-id=? x #'load) 'load)
((free-id=? x #'eval) 'eval)
((free-id=? x #'expand) 'expand)
(else (syntax-violation 'eval-when
"invalid situation"
e (wrap x w #f)))))
(cons (let ((x (syntax->datum (car when-list))))
(if (memq x '(compile load eval expand))
x
(syntax-violation 'eval-when
"invalid situation"
e (wrap (car when-list) w #f))))
situations))))))
;; syntax-type returns six values: type, value, e, w, s, and mod. The