[racket-dev] TR & check-equal?

I use this workaround in the math library, whose arrays are higher-order 
values that *can* be checked for equality:

(require (except-in typed/rackunit check-equal?))

;; This gets around the fact that typed/rackunit can no longer test
;; higher-order values for equality, since TR has firmed up its rules
;; on passing `Any' types in and out of untyped code
(define-syntax-rule (check-equal? a b . message)
   (check-true (equal? a b) . message))


There's got to be a more general fix along these lines.

Neil ⊥

On 05/29/2013 09:19 AM, Robby Findler wrote:
> Yes: my message is about strange error messages that cause newbies to
> just conclude that testing TR programs doesn't work. While I can
> certainly fault someone for coming to this conclusion (and I did) I
> think only half of the problem is on their side.
>
> If they had gotten this message, they might have said "equal? isn't what
> I want here" and then maybe made some progress.
>
> But I do agree with you and if it is hard to get to even this state,
> then it probably isn't worth pursuing.
>
> Robby
>
>
> On Wed, May 29, 2013 at 10:11 AM, Matthias Felleisen
> <matthias at ccs.neu.edu <mailto:matthias at ccs.neu.edu>> wrote:
>
>
>     If TR lived up exactly to the R level of semantics, to wit:
>
>      > Welcome to DrRacket, version 5.3.4.10--2013-05-29(05524114/d) [3m].
>      > Language: racket.
>      > > (struct s ())
>      > > (require rackunit)
>      > > (check-equal? (s) (s))
>      > --------------------
>      > FAILURE
>      > actual:     #<s>
>      > expected:   #<s>
>      > name:       check-equal?
>      > location:   (unsaved-editor324 5 2 126 22)
>      > expression: (check-equal? (s) (s))
>      >
>      > . . Check failure
>      > --------------------
>
>
>     would you really write a different message to dev? Opaque structures
>     pose a problem for testing and that problem exists at both levels.
>
>     -- Matthias
>
>
>
>
>
>
>     On May 29, 2013, at 8:02 AM, Robby Findler
>     <robby at eecs.northwestern.edu <mailto:robby at eecs.northwestern.edu>>
>     wrote:
>
>      > Well, given that replacing check-equal? with equal? (on the typed
>     side) works, then it seems to me that one solution would be to move
>     more of rackunit into TR, or to refactor rackunit to be more
>     friendly to TR. (And if someone is going to work on this, then it
>     would also be great if the error messages from failed test cases
>     were made a bit more legible.)
>      >
>      > Robby
>      >
>      >
>      > On Wed, May 29, 2013 at 6:53 AM, Sam Tobin-Hochstadt
>     <samth at ccs.neu.edu <mailto:samth at ccs.neu.edu>> wrote:
>      > That is indeed the correct fix.  I'm not entirely sure how to improve
>      > the error message, since the problem in your original code is real.
>      > There's no way the generated contract can tell at runtime that the
>      > values passed to `check-equal?` aren't higher-order, so it has to
>      > conservatively reject the call.  Suggestions are certainly welcome.
>      >
>      > Sam
>      >
>      > On Wed, May 29, 2013 at 7:46 AM, Robby Findler
>      > <robby at eecs.northwestern.edu
>     <mailto:robby at eecs.northwestern.edu>> wrote:
>      > > I'm not sure if this should be considered a bug or a feature
>     request (or
>      > > something else, but hopefully one of those two!) so I thought
>     I'd ask here
>      > > before sending in a PR. This program:
>      > >
>      > >   #lang typed/racket
>      > >   (require typed/rackunit)
>      > >   (struct: s ([a : Integer]))
>      > >   (check-equal? (s 1) (s 2))
>      > >
>      > > produces the output:
>      > >
>      > > check-equal?: broke its contract
>      > >   Attempted to use a higher-order value passed as `Any` in
>     untyped code:
>      > > #<s>
>      > >   in: the 1st argument of
>      > >       (recursive-contract
>      > >        (->* (Any Any) (String) any/c)
>      > >        #:impersonator)
>      > >   contract from: (interface for check-equal?)
>      > >   blaming: (interface for check-equal?)
>      > >   at: <collects>/typed/rackunit/main.rkt:20.2
>      > >
>      > > which is a bit confusing. (As someone who's been around Racket
>     long enough,
>      > > I guessed that sticking #:transparent into the struct
>     declaration would be a
>      > > thing to try, but newcomers seem unlikely to find that workaround.)
>      > >
>      > > Robby
>      > >
>      > >
>      > > _________________________
>      > >   Racket Developers list:
>      > > http://lists.racket-lang.org/dev
>      > >
>      >
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>
>
>
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