You would continue to be free to discourage the usage of Result for
whatever you want. For the rest of us, Result isn’t intended to replace throws
or do/catch, but provide a way to accomplish things in a much more compact and
sometimes natural way. As with any API it could be used stupidly. But frankly,
what developers what to do to wrap their errors is up to them. Adding Result is
just a way of blessing a result/error representation, since it has become a
rather common pattern. If you’ve looked at the implementation I showed, you’ll
see that there’s far more functionality than just a Result type, including API
for converting back and forth from throwing functions, as well as functional
transforms. Result is a complement to try do catch, not a replacement.
Jon
> On Nov 2, 2017, at 2:48 PM, Tony Allevato <tony.allev...@gmail.com> wrote:
>
>
>
> On Thu, Nov 2, 2017 at 11:32 AM Jon Shier <j...@jonshier.com
> <mailto:j...@jonshier.com>> wrote:
> That’s been an argument against Result for 2 years now. The usefulness
> of the type, even outside of whatever asynchronous language support the core
> team comes up with, perhaps this year, perhaps next year, is still very high.
> Even as something that just wraps throwing functions, or otherwise exists as
> a local, synchronous value, it’s still very useful as way to encapsulate the
> value/error pattern.
>
> This is one of the parts that concerns me, actually. The beauty of Swift's
> error design is that function results denote expected/successful outcomes and
> thrown errors denote unexpected/erroneous outcomes. Since they are different,
> each is handled through its own language constructs, and since the language
> itself supports it (rather than being entirely type-based), you don't have
> the proliferation of unwrapping boilerplate that you have with Result<>.
>
> In our own code bases, I actively discourage the use of Result<> in that way,
> because it tries to cram both of those concepts into the expected/successful
> outcomes slot in the language. For asynchronous APIs that's somewhat
> unavoidable today, but if that's going to change, I'd rather the language
> focus on a way that's consistent with other error handling already present in
> Swift.
>
> Adding an API to the standard library is the core team saying "this is
> blessed as something around which we support APIs being designed." IMO, I'd
> prefer it if the language did *not* bless two disparate ways of communicating
> error outcomes but rather converged on one.
>
> IMO, "things aren't happening fast enough" isn't great motivation for putting
> something permanently into the standard library or the language without
> considering the context of other things going on around it. If you're going
> to propose something that overlaps with asynchronous APIs, it only helps your
> case if you can discuss how it can integrate—rather than collide—with those
> efforts.
>
>
>
> That pattern will likely never go away. Additionally, having the Result type
> in the standard library removes a source of conflict between all other Result
> implementations, which are becoming more common.
>
>
>> On Nov 2, 2017, at 2:26 PM, Tony Allevato <tony.allev...@gmail.com
>> <mailto:tony.allev...@gmail.com>> wrote:
>>
>> Given that the Swift team is currently working on laying the groundwork for
>> asynchronous APIs using an async/await model, which would presumably tie the
>> throwing cases more naturally into the language than what is possible using
>> completion-closures today, are we sure that this wouldn't duplicate any
>> efforts there or be made obsolete through other means?
>>
>> In other words, while Result<> can be a very useful foundational component
>> on its own, I think any proposal for it can't be made in isolation, but very
>> much needs to consider other asynchronous work going on in the language.
>>
>>
>> On Thu, Nov 2, 2017 at 11:15 AM Jon Shier via swift-evolution
>> <swift-evolution@swift.org <mailto:swift-evolution@swift.org>> wrote:
>> You don’t lose it, it’s just behind `Error`. You can cast out whatever
>> strong error type you need without having to bind an entire type to it
>> generically. If getting a common error type out happens a lot, I usually add
>> a convenience property to `Error` to do the cast for me. Plus, having to
>> expose an entire new error wrapper is just a non starter for me and doesn’t
>> seem necessary, given how Result is currently used in the community.
>>
>>
>> Jon
>>
>>
>>> On Nov 2, 2017, at 2:12 PM, Dave DeLong <sw...@davedelong.com
>>> <mailto:sw...@davedelong.com>> wrote:
>>>
>>> I think I’d personally rather see this done with a generic error as well,
>>> like:
>>>
>>> enum GenericResult<T, E: Error> {
>>> case success(T)
>>> case failure(E)
>>> }
>>>
>>> And a typealias:
>>>
>>> typealias Result<T> = GenericResult<T, AnyError>
>>>
>>> This would require an “AnyError” type to type-erase a specific Error, but
>>> I’ve come across many situations where a strongly-typed error is incredibly
>>> useful, and I’d be reluctant to see that thrown away.
>>>
>>> Dave
>>>
>>>> On Nov 2, 2017, at 12:08 PM, Jon Shier via swift-evolution
>>>> <swift-evolution@swift.org <mailto:swift-evolution@swift.org>> wrote:
>>>>
>>>> Swift-Evolution:
>>>> I’ve written a first draft of a proposal to add Result<T> to the
>>>> standard library by directly porting the Result<T> type used in Alamofire
>>>> to the standard library. I’d be happy to implement it (type and tests for
>>>> free!) if someone could point me to the right place to do so. I’m not
>>>> including it directly in this email, since it includes the full
>>>> implementation and is therefore quite long. (Discourse, please!)
>>>>
>>>> https://github.com/jshier/swift-evolution/blob/master/proposals/0187-add-result-to-the-standard-library.md
>>>>
>>>> <https://github.com/jshier/swift-evolution/blob/master/proposals/0187-add-result-to-the-standard-library.md>
>>>>
>>>>
>>>> Thanks,
>>>>
>>>> Jon Shier
>>>>
>>>>
>>>> _______________________________________________
>>>> swift-evolution mailing list
>>>> swift-evolution@swift.org <mailto:swift-evolution@swift.org>
>>>> https://lists.swift.org/mailman/listinfo/swift-evolution
>>>> <https://lists.swift.org/mailman/listinfo/swift-evolution>
>>>
>>
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>
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