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In case', report binding info of else' in error

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shhyou 2019-02-27 11:40:04 -06:00 committed by shuhung
parent 68312e43bd
commit e970a6194a
1 changed files with 22 additions and 1 deletions
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23
racket/collects/racket/private/case.rkt
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@ -67,7 +67,28 @@
[(bad . _)
(raise-syntax-error
#f
"bad syntax (not a datum sequence)"
;; If #'bad is an identifier, report its binding in the error message.
;; This helps resolving the syntax error when `else' is shadowed somewhere
(if (not (symbol? (syntax-e (syntax bad))))
"bad syntax (not a datum sequence)"
(string-append
"bad syntax (not a datum sequence)\n"
" expected: a datum sequence or the binding 'else' from racket/base\n"
" given: "
(let ([binding (identifier-binding (syntax bad))])
(cond
[(not binding) "an unbound identifier"]
[(eq? binding 'lexical) "a locally bound identifier"]
[else
(let*-values ([(src) (car binding)]
[(mpath base) (module-path-index-split src)])
(cond
[(not mpath)
"an identifier bound by the current module"]
[else
(format "an identifier required from the module ~a"
(resolved-module-path-name
(module-path-index-resolve src)))]))]))))
stx
(syntax bad))]
[_