[swift-evolution] Adding Result to the Standard Library

[Benjamin G]

I'm also in favor of providing the ability to specify the type of the error
for the result. It provides self-documenting and type safety advantages
over the generic Error that really makes the type much more useful.

The ideal would be to have the two possible syntax (Result<T> and
Result<T,E>) , but i'm not sure how feasible that is.

On Thu, Nov 2, 2017 at 7:15 PM, Jon Shier via swift-evolution <
swift-evolution at 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 <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> 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
>
>
> Thanks,
>
> Jon Shier
>
>
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