On Sun, Oct 23, 2011 at 1:39 PM, Sam Tobin-Hochstadt <sa...@ccs.neu.edu> wrote:
>
> Yes, I have planned to do this for a while. Probably the form it will
> take will be a macro that always produces a type error when checked,
> rather than a new type. Then macros could use this form to ensure
> exhaustiveness.
This is now implemented in git.
There's an `typecheck-fail' form which raises a type error when it is
reachable. Here's an example [1]
(define-syntax (cond* stx)
(syntax-case stx ()
[(_ x clause ...)
#`(cond clause ... [else (typecheck-fail #,stx "incomplete
coverage" #:covered-id x)])]))
(: f : (U String Integer) -> Boolean)
(define (f x)
(cond* x
[(string? x) #t]
[(exact-nonnegative-integer? x) #f]))
This produces a type error highlighting the `cond*' form, with the message:
Type Checker: incomplete coverage; missing coverage of Negative-Integer in:
(cond* x ((string? x) #t) ((exact-nonnegative-integer? x) #f))
[1] https://gist.github.com/1314097
--
sam th
sa...@ccs.neu.edu
_________________________________________________
For list-related administrative tasks:
http://lists.racket-lang.org/listinfo/users
