[swift-evolution] Adding Result to the Standard Library

[Jon Shier]

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 <swift at 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 at swift.org <mailto:swift-evolution at 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
>> 
>> 
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> 

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