[racket] Typed Racket error (exporting a struct containing a hash table)

From: Sam Tobin-Hochstadt (samth at ccs.neu.edu)
Date: Sat Dec 10 19:41:26 EST 2011

On Sat, Dec 10, 2011 at 7:35 PM, Jeremiah Willcock <jewillco at osl.iu.edu> wrote:
> On Sat, 10 Dec 2011, Sam Tobin-Hochstadt wrote:
>> On Sat, Dec 10, 2011 at 5:54 PM, Jeremiah Willcock <jewillco at osl.iu.edu>
>> wrote:
>>> When I run the following program:
>>> #lang typed/racket
>>> (struct: A ((f : (HashTable Any Any))))
>>> (provide (all-defined-out))
>>> I get the error message:
>>> racket-Linux-install/lib/racket/collects/racket/contract/private/hash.rkt:57:0:
>>> hash/c: expected either a flat or chaperone contract for the domain, got
>>> Any
>>> "Check Syntax" does not produce any errors, and highlights the program
>>> correctly.  My "About DrRacket..." version string is "Welcome to
>>> DrRacket,
>>> version, english" (from the Git repository as of
>>> Dec. 6, 2011).  The "provide" form is necessary for the program to fail.
>>> I
>>> would appreciate any help you might be able to give.
>> The problem is in the `Any' contract.  The implementation of `Any'
>> can't be used as the contract for hashtable keys.
>> I'll fix this so that it works for this program, but you won't be able
>> to, in general, define a `HashTable' with key type `Any' in Typed
>> Racket and insert higher-order values as keys.
>> To work around this for the moment, use a more specific contract than
>> `Any' on the keys.
> I've tried more specific key types as well, and got similar errors for those
> as well (at least for something define-typed as (U (Vectorof Any) Symbol)).

If it contains the type `Any' (roughly), it will have this problem.
sam th
samth at ccs.neu.edu

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