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syntax/parse: add dynamic check for null ellipsis-head match

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Otherwise, nullable ellipsis-head patterns could cause infinite loop.
This commit is contained in:
Ryan Culpepper 2016-05-16 00:46:57 -04:00
parent 669460da34
commit fb5c1310d8
2 changed files with 8 additions and 2 deletions
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5
racket/collects/syntax/parse/private/parse.rkt
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@ -984,8 +984,9 @@ Conventions:
(for/list ([id (in-list ids)]) (bound-id-table-ref table id)))]) (for/list ([id (in-list ids)]) (bound-id-table-ref table id)))])
(with-syntax ([(id ...) ids] (with-syntax ([(id ...) ids]
[(alt-id ...) alt-ids]) [(alt-id ...) alt-ids])
#`(let ([alt-id (rep:combine repc (attribute id) alt-id)] ...) #`(let ([alt-id (rep:combine repc (attribute id) alt-id)] ...
k)))) [diff (ps-difference pr pr*)])
(if (zero? diff) (error/null-eh-match) k)))))
(syntax-case #'repc () (syntax-case #'repc ()
[#f #`(parse:H x cx x* cx* pr* head pr es k*)] [#f #`(parse:H x cx x* cx* pr* head pr es k*)]
[_ #`(parse:H x cx x* cx* pr* head pr es [_ #`(parse:H x cx x* cx* pr* head pr es

5
racket/collects/syntax/parse/private/residual.rkt
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@ -60,6 +60,7 @@
datum->syntax/with-clause datum->syntax/with-clause
check/force-syntax-list^depth check/force-syntax-list^depth
check-literal* check-literal*
error/null-eh-match
begin-for-syntax/once begin-for-syntax/once
name->too-few/once name->too-few/once
@ -216,6 +217,10 @@
(and used-phase (- used-phase mod-phase))) (and used-phase (- used-phase mod-phase)))
ctx id))) ctx id)))
;; error/null-eh-match : -> (escapes)
(define (error/null-eh-match)
(error 'syntax-parse "an ellipsis-head pattern matched an empty sequence"))
;; (begin-for-syntax/once expr/phase1 ...) ;; (begin-for-syntax/once expr/phase1 ...)
;; evaluates in pass 2 of module/intdefs expansion ;; evaluates in pass 2 of module/intdefs expansion
(define-syntax (begin-for-syntax/once stx) (define-syntax (begin-for-syntax/once stx)