On 2013-02-05 16:06:11 -0500, Joe Gibbs Politz wrote: > This worked in 5.3.1: > > typed.rkt > ======= > #lang typed/racket > > (provide wrap) > > (define: (wrap (p : Procedure)) : Procedure > (λ (_) p)) > > untyped.rkt > =========== > #lang racket > > (require "typed.rkt") > (define f (λ (n) n)) > > ((wrap f) 5) ;; returns f itself; f is eq? to ((wrap f) 5)
It turns out that allowing values of `Procedure` type escape into untyped code is unsound. In particular, you could use `wrap` to "cast" any typed procedure into one that doesn't get protected when exported to untyped code. > In 5.3.2, when running untyped.rkt, I get: > > #<case-lambda-procedure>: arity mismatch; > the expected number of arguments does not match the given number > given: 1 > arguments...: > 5 I agree that this error message is bad. It's a result of changing the type `Procedure` to use the contract `(case->)`. Maybe we should use a custom contract here instead that produces a better error message. Cheers, Asumu ____________________ Racket Users list: http://lists.racket-lang.org/users
