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improve ->i syntax error message when dependencies are cyclic

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This commit is contained in:
Robby Findler 2014-05-26 12:30:22 -05:00
parent 817ec2238a
commit 5631732e9d
1 changed files with 28 additions and 6 deletions
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34
racket/collects/racket/contract/private/arr-i-parse.rkt
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@ -216,12 +216,34 @@ code does the parsing and validation of the syntax.
[(free-identifier-mapping-get safe var (λ () #f))
(void)]
[(memf (λ (x) (free-identifier=? x var)) visited)
(let ([ids (trim-at var visited)])
(raise-syntax-error #f
"cyclic dependencies are not allowed"
stx
(car ids)
(cdr ids)))]
(define ids (trim-at var visited))
(cond
[(null? (cdr ids))
(raise-syntax-error #f
(format "~s's contract depends on ~s's value"
(syntax-e (car ids))
(syntax-e (car ids)))
stx
(car ids))]
[else
(raise-syntax-error
#f
(format "generation of ~s's contract depends on ~s's value; specifically:~a~a"
(syntax-e (car ids))
(syntax-e (car ids))
(apply
string-append
(for/list ([i (in-list ids)]
[j (in-list (cdr ids))])
(format "\n ~s's contract depends on ~s"
(syntax-e i)
(syntax-e j))))
(format " and\n ~s's contract depends on ~a"
(syntax-e (car (reverse ids)))
(syntax-e (car ids))))
stx
(car ids)
(cdr ids))])]
[else
(let ([new-visited (cons var visited)])
(for ([neighbor (in-list (free-identifier-mapping-get neighbors var))])