> On Jan 11, 2017, at 10:35 AM, Erica Sadun <er...@ericasadun.com> wrote:
> 
>> 
>> On Jan 10, 2017, at 10:35 PM, Russ Bishop via swift-evolution 
>> <swift-evolution@swift.org <mailto:swift-evolution@swift.org>> wrote:
>> 
>> 
>>> On Dec 28, 2016, at 8:11 PM, Chris Lattner via swift-evolution 
>>> <swift-evolution@swift.org <mailto:swift-evolution@swift.org>> wrote:
>>> 
>>> 
>>>> On Dec 28, 2016, at 7:47 PM, Xiaodi Wu via swift-evolution 
>>>> <swift-evolution@swift.org <mailto:swift-evolution@swift.org>> wrote:
>>>> 
>>>> I thought there is already a pending proposal on typed throws?
>>> 
>>> There was, I vaguely recall that it was by Russ?  I don’t see any open PRs 
>>> for it.
>> 
>> Hey now, there is no need for name calling ;)
>> 
>> 
>>> 
>>> I’m personally a big fan of typed throws, but I know that John McCall has 
>>> strong concerns.  I can’t argue that typed throws is a high priority at the 
>>> moment, but as soon as we start talking about concurrency the topic of a 
>>> Result type will come back up (for use with futures/async).
>> 
>> I fall firmly in John McCall’s camp on this one. If someone wants to read 
>> that part of the thread: 
>> https://lists.swift.org/pipermail/swift-evolution/Week-of-Mon-20151207/000958.html
>>  
>> <https://lists.swift.org/pipermail/swift-evolution/Week-of-Mon-20151207/000958.html>
>> 
>> Of course if we want to automatically convert a throws function into an 
>> awaitable Result then that naturally begs the question of either Result’s 
>> error is typed as Error or not. I think I fall into the “as Error” camp here 
>> too because Swift’s switch is powerful enough to pattern match on the type 
>> fairly nicely but I haven’t thought about it very much.
>> 
>> 
>> All that said… if Swift got a macro system Rust’s error-chain seems to have 
>> some interesting ideas that avoid a lot of boilerplate.
> 
> If Swift has a canonical built-in system for reporting an Error, why wouldn't 
> it be used here? Why use casting?
> 
> — E

I was using shorthand for “struct Result<T> { let error: Error? }” vs “struct 
Result<T, E: Error> { let error: E? }”… as in I prefer not having a second 
generic type parameter to denote the error.

Russ



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