[racket] TR: struct: #:prefab option

Couldn't this be solved by protecting the struct on export?

#lang racket/load

(module foo racket
 (struct foo (f) #:prefab)
 (define x (foo (lambda (x) (* 3.3 x))))
 (provide/contract
   (x (struct/c foo (-> number? number?)))))
(module bar racket
  (require 'foo)
  (struct foo (f) #:prefab)
  ((foo-f x) "foo"))
(require 'bar)

On Mon, May 6, 2013 at 7:27 AM, Asumu Takikawa <asumu at ccs.neu.edu> wrote:
> On 2013-05-06 10:09:06 -0400, Ray Racine wrote:
>>    The below is now failing for me.
>>    (struct: Stuff ([this : String][that : Natural]) #:prefab)
>>
>> [...]
>>
>>    If there is a typing issue with the use of #:prefab and its banishment
>>    permanent, is there an alternate best practice mechanism for easy struct:
>>    serialization/de-serialization?
>
> If you're using the Racket pre-release, then that was probably my commit
> that broke that. Sorry for breaking compatibility here, but it's unsound
> for TR to admit #:prefab as is. Here's an example:
>
>   $ racket
>   Welcome to Racket v5.3.
>   -> (module foo typed/racket
>        (struct: foo ([f : (Float -> Float)]) #:prefab)
>        (define x (foo (lambda: ([x : Float]) (* 3.3 x))))
>        (provide x))
>   -> (module bar racket
>        (require 'foo)
>        (struct foo (f) #:prefab)
>        ((foo-f x) "foo"))
>   -> (require 'bar)
>   2.293305645053357e-309
>
> The first module exports a #:prefab struct instance containing an
> optimized (Float -> Float) function. Since it's a prefab, the second
> module (which is untyped), can freely access the function stored inside.
>
> Since the function is unprotected, it does an unsafe multiplication on a
> string and no contract error is raised.
>
> I'm not sure what's a good alternative for serialization in TR off the
> top of my head.
>
> Cheers,
> Asumu
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