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better error message for define-syntax-rule

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This commit is contained in:
Jon Rafkind 2010-11-09 17:23:25 -07:00
parent 3936a40717
commit 81eac261dc
1 changed files with 12 additions and 10 deletions
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22
collects/racket/private/misc.rkt
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@ -12,18 +12,20 @@
(define-syntax define-syntax-rule
(lambda (stx)
(syntax-case stx ()
[(dr (foo . pattern) template)
(identifier? #'foo)
[(dr (name . pattern) template)
(identifier? #'name)
(syntax/loc stx
(define-syntax foo
(lambda (x)
(syntax-case** dr #t x () free-identifier=?
[(_ . pattern) (syntax/loc x template)]))))]
[(dr (foo . pattern) template)
(raise-syntax-error 'define-syntax-rule "expected an identifier" stx #'foo)]
[(dr (foo . pattern))
(define-syntax name
(lambda (user)
(syntax-case** dr #t user () free-identifier=?
[(_ . pattern) (syntax/loc user template)]
[else (raise-syntax-error 'name (format "~a did not match pattern ~a" (syntax->datum user) '(name . pattern)))]
))))]
[(dr (name . pattern) template)
(raise-syntax-error 'define-syntax-rule "expected an identifier" stx #'name)]
[(dr (name . pattern))
(raise-syntax-error 'define-syntax-rule "no template provided" stx)]
[(dr (foo . pattern) template . etc)
[(dr (name . pattern) template . etc)
(raise-syntax-error 'define-syntax-rule "too many templates" stx #'etc)]
[(dr head . template)
(raise-syntax-error 'define-syntax-rule "invalid pattern" stx #'head)])))