On Jul 5, 2012 8:50 PM, "Neil Toronto" <neil.toro...@gmail.com> wrote: > > I just found this today: > > > #lang typed/racket > > (define: b : (Boxof Any) (box 4)) > > (define-predicate boxof-integer? (Boxof Integer))
This is the bug -- there's no way to write the boxof-integer? predicate, and define- predicate shouldn't think it can. > (define (set-b-box! v) (set-box! b v)) > > (: a-very-listy-integer (-> Integer)) > (define (a-very-listy-integer) > (cond [(boxof-integer? b) (set-b-box! '(1 2 3)) > (unbox b)] > [else (error 'a-very-listy-integer "can't happen")])) > > > > (a-very-listy-integer) > - : Integer > '(1 2 3) > > > Is this a bug or a limitation? It can be replicated with any mutable container type as far as I can tell. A bug. Anytime you get a result like that it's a bug. > > Also, if it's a limitation, can I get (Vectorof Index) to be a subtype of (Vectorof Integer)? No, that relationship would be unsound for similar reasons. > Neil ⊥ > _________________________ > Racket Developers list: > http://lists.racket-lang.org/dev
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