Re: [racket-users] Raising arbitrary errors in Typed Racket

2017-12-02 Thread Ben Greenman 
Oh right --- instead of making a new exception type, it's possible to
use `require/typed` to give `raise` a different type signature:

```
#lang typed/racket/base

(require/typed racket/base
  (raise (All (A) (-> Any A

(with-handlers ((vector? values))
  (raise (vector 1 2 3)))
;; '#(1 2 3)
```

[[ any-wrap/c is the contract for the `Any` type ]]

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Re: [racket-users] Raising arbitrary errors in Typed Racket

2017-12-02 Thread Robby Findler 
It is a contract that TR uses internally that might be helpful here,
maybe. Or maybe not! :)

Robby

On Sat, Dec 2, 2017 at 3:32 AM, HiPhish  wrote:
> What is any-wrap/c? It does not show up in the documentation.
>
> On Friday, December 1, 2017 at 9:17:18 PM UTC+1, Robby Findler wrote:
>>
>> Why not use any-wrap/c?
>
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Re: [racket-users] Raising arbitrary errors in Typed Racket

2017-12-02 Thread HiPhish 
What is any-wrap/c? It does not show up in the documentation.

On Friday, December 1, 2017 at 9:17:18 PM UTC+1, Robby Findler wrote:
>
> Why not use any-wrap/c?
>

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Re: [racket-users] Raising arbitrary errors in Typed Racket

2017-12-01 Thread Robby Findler 
Why not use any-wrap/c?

Robby

On Fri, Dec 1, 2017 at 8:39 PM Sam Tobin-Hochstadt 
wrote:

> Two notes:
>
> 1. It is unsafe to expose mutable data to untyped code via exceptions
> without wrapping them. If you `(raise f)`, then untyped code could
> catch the exception and call `f`.
>
> 2. You should inherit from `exn:fail` -- other `exn` types are for
> non-standard exceptions such as `exn:break`.
>
> Sam
>
> On Fri, Dec 1, 2017 at 2:24 PM, Ben Greenman
>  wrote:
> > That name sounds good to me.
> >
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Re: [racket-users] Raising arbitrary errors in Typed Racket

2017-12-01 Thread Sam Tobin-Hochstadt 
Two notes:

1. It is unsafe to expose mutable data to untyped code via exceptions
without wrapping them. If you `(raise f)`, then untyped code could
catch the exception and call `f`.

2. You should inherit from `exn:fail` -- other `exn` types are for
non-standard exceptions such as `exn:break`.

Sam

On Fri, Dec 1, 2017 at 2:24 PM, Ben Greenman
 wrote:
> That name sounds good to me.
>
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Re: [racket-users] Raising arbitrary errors in Typed Racket

2017-12-01 Thread Ben Greenman 
That name sounds good to me.

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Re: [racket-users] Raising arbitrary errors in Typed Racket

2017-12-01 Thread HiPhish 
Thank you, I have made my own exception type now. Is `exn:fail:rpc` 
appropriate or should I use a different name? Using that name looks like 
I'm inserting it into Racket's own exception type hierarchy.

On Friday, December 1, 2017 at 8:11:27 PM UTC+1, Ben Greenman wrote:
>
> ...
>

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Re: [racket-users] Raising arbitrary errors in Typed Racket

2017-12-01 Thread Ben Greenman 
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:

```
#lang typed/racket/base

(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  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)
> (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)))
> #
>
> 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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[racket-users] Raising arbitrary errors in Typed Racket

2017-12-01 Thread HiPhish 
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)))
#

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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