The error is because type signature of `raise` doesn't allow
"non-flat" values like functions and mutable vectors.
It might not be safe to allow `(raise (vector 1 2 3))` in Typed Racket
... I'm not sure.
For now I think you should make a new exception type. Example:
(define-type Packable (U Byte (Vectorof Packable)))
(struct exn:fail:rpc exn ((val : Packable)))
(with-handlers ((exn:fail:rpc? exn:fail:rpc-val))
(raise (exn:fail:rpc "oops" (current-continuation-marks) (vector 1 2 3))))
On Fri, Dec 1, 2017 at 9:05 AM, HiPhish <hiph...@openmailbox.org> wrote:
> Hello Racketeers,
> I have been trying to port a module over to Typed Racket, and I have almost
> succeeded except for one issue: raising an arbitrary object as an error.
> Compare the following code:
> ;; Works fine
> (raise 3)
> ;; Does not work
> (raise (vector 1 2 3))
> The error I get is
> ; nvim-client/client.rkt:244:55: Type Checker: No function domains
> matched in
> ; function application:
> ; Domains: (U (Rec flat (U (Pairof flat flat) Boolean Char Complex
> Keyword Null
> ; String Symbol)) exn) Any
> ; (U (Rec flat (U (Pairof flat flat) Boolean Char Complex
> Keyword Null
> ; String Symbol)) exn)
> ; Arguments: (U (Immutable-HashTable Packable Packable)
> ; Packable Packable) (Pairof Packable (Listof Packable))
> ; Packable Packable) Boolean Bytes Ext Message-Args Null Real String)
> ; in: (raise error)
> ; [,bt for context]
> So I looked up the signature of `raise` and I get this:
> > raise
> - : (->* ((U (Rec
> (U (Pairof flat flat)
> (Nothing : (Bot | Bot)))
> So what does this mean and what should I do? I am porting a module from my
> Neovim client which uses the MessagePack-RPC protocol, and part of the
> is that any object that can be packed can be raised as an error.
> Raising any object as an error would have allowed someone making an RPC
> to just do something like this:
> (with-handlers ([packable? (λ (exn) (display exn))])
> (rpc-request "foo" '#(bar)))
> What should I do instead? Create a new error type like `exn:fail:rpc`? Or am
> missing something here?
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