Using typed racket with web server continuations `(send/suspend/dispatch ...)`

[Marc Kaufmann]

Hi,

if possible, I'd like to use web server continuations with `(send/suspend/dispatch...)`. However, currently I need to return something of type `response?`, but when send/suspend/dispatch (and friends) don't return a response - they send it to the client and return `Any` (or other types).

The question is: is this even possible to get working when my servlet expects a response back? And if not, is there some clever way to make it work anyway - typing things differently? I think that I won't go down the road of using different types, since sometimes I want to use a function that returns a response directly, rather than via web continuations.

The cod so far:

```{module that creates the response}

#lang typed/racket

(require typed/web-server/http)
(define-type EmbedURL (-> (-> request Any) String))
(define-type ResponseMaker (-> EmbedURL response))

(require/typed web-server/servlet
               [send/suspend/dispatch (-> ResponseMaker Any)])

(define continuation-servlet

  (λ (req)
     (: response-generator ResponseMaker)
     (define (response-generator embed/url)
       (response/wrap-xexpr
         #:title text
         #:wrap-body? #t
         #:xexpr `(body (h1 ,text)
                        ,(if when-done
                           (next-button (λ () (when-done (state-response 'next 'display-page)))
                                        embed/url)
                           '(p "Thanks and goodbye"))
                        )))
     (send/suspend/dispatch response-generator))))

```

which gets called elsewhere in a non-typed module via `(continuation-servlet req)`, which has the wrong type. I could simply claim that the returned type is response (it's thrown away anyway, I think), but that seems wrong at the conceptual level.

Thanks for any pointers as to how to make this work - or why not to try to make it work.

Cheers,
Marc