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)
(Mutable-HashTable
; Packable Packable) (Pairof Packable (Listof Packable))
(Weak-HashTable
; 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
flat
(U (Pairof flat flat)
Boolean
Char
Complex
Keyword
Null
String
Symbol))
exn))
(Any)
(Nothing : (Bot | Bot)))
#<procedure:raise>
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
protocol
is that any object that can be packed can be raised as an error.
https://github.com/msgpack-rpc/msgpack-rpc/blob/master/spec.md#error
Raising any object as an error would have allowed someone making an RPC
request
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 I
missing something here?
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