[racket] Typed Racket and require/typed for polymorphic structs

From: Eric Dobson (eric.n.dobson at gmail.com)
Date: Wed Aug 7 00:53:14 EDT 2013

I'm assuming you mean parametric contracts instead of polymorphic. But
not sure why those would be the correct solution, I think any/c would
work, I'm not seeing a case where wrapping the value would protect

I don't see a fundamental limitation to doing this either.

On Tue, Aug 6, 2013 at 2:56 PM, Asumu Takikawa <asumu at ccs.neu.edu> wrote:
> Hi all,
> Does anyone know why Typed Racket does not support importing polymorphic
> structs using the #:struct keyword in `require/typed`? Is this a
> fundamental limitation or just a "small matter of programming"?
> i.e., I want to do something like
>   (require/typed lang/posn
>     [#:struct posn (A) ([x : A] [y: A])])
> This seems like it could be supported by the contract system in most
> cases (with polymorphic contracts on accessors and constructors). The
> case in which it wouldn't work is if you wanted to export a struct
> instance with a polymorphic type from the untyped module.
> Cheers,
> Asumu
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