[racket] What am I doing wrong in this typed racket program?

+1 

A flavor of this problem has come up repeatedly, and it will come up again. We need some fix. 





On Sep 18, 2012, at 6:28 PM, Ryan Culpepper wrote:

> Typed Racket should raise an error saying something like "(Setof Any) cannot be translated to a contract". Then elaborate in the docs where you discuss interaction with untyped code about what types cannot be converted to contracts and maybe why.
> 
> Ryan
> 
> 
> On 09/18/2012 06:00 PM, Sam Tobin-Hochstadt wrote:
>> I'm saying that I don't at the moment know how to avoid giving this
>> error, given the current behavior of `set/c`.
>> 
>> On Tue, Sep 18, 2012 at 5:57 PM, Robby Findler
>> <robby at eecs.northwestern.edu> wrote:
>>> Are you saying it is reasonable that a typed racket program should
>>> produce contract constructor errors like that?
>>> 
>>> Robby
>>> 
>>> On Tue, Sep 18, 2012 at 4:53 PM, Sam Tobin-Hochstadt <samth at ccs.neu.edu> wrote:
>>>> The problem here is that `Any` is a special contract which isn't a
>>>> "chaperone contract", and `set/c` requires chaperone contracts.
>>>> 
>>>> It's not obvious to me if this can be detected statically, but you can
>>>> work around this by changing `Any` to some other type.
>>>> 
>>>> Sam
>>>> 
>>>> On Tue, Sep 18, 2012 at 5:44 PM, Tony Garnock-Jones <tonyg at ccs.neu.edu> wrote:
>>>>> Hi all,
>>>>> 
>>>>> What could I be doing wrong here?
>>>>> 
>>>>>     #lang typed/racket
>>>>>     (provide (struct-out foo))
>>>>>     (struct: foo ([bar : (Setof Any)]))
>>>>> 
>>>>> Racket 5.3.0.24 complains about it ("racket problem.rkt"):
>>>>> 
>>>>>     set/c: contract violation
>>>>>       expected: chaperone-contract?
>>>>>       given: #<make-contract>
>>>>>       context...:
>>>>>        /Users/tonyg/src/racket-typed-matrix/problem.rkt: [running body]
>>>>> 
>>>>> The complaint vanishes if I comment out the provide, remove the bar
>>>>> field, or change the bar field's type to Any/Integer/etc.
>>>>> 
>>>>>   Tony
>>>>> ____________________
>>>>>   Racket Users list:
>>>>>   http://lists.racket-lang.org/users
>>>> 
>>>> 
>>>> 
>>>> --
>>>> sam th
>>>> samth at ccs.neu.edu
>>>> ____________________
>>>>   Racket Users list:
>>>>   http://lists.racket-lang.org/users
>> 
>> 
>> 
> 
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