[swift-evolution] [Pitch] Introducing role keywords to reduce hard-to-find bugs

Erica Sadun erica at ericasadun.com
Fri Jun 16 08:33:27 CDT 2017

> On Jun 14, 2017, at 11:46 PM, Dave Abrahams via swift-evolution <swift-evolution at swift.org> wrote:
> on Wed Jun 14 2017, Chris Lattner <swift-evolution at swift.org> wrote:
>>> On Jun 14, 2017, at 10:11 AM, Erica Sadun via swift-evolution
>>> <swift-evolution at swift.org> wrote:
>>> Some pals and I have been kicking an idea around about introducing
>>> better ways to support the compiler in protocol extensions. We want
>>> to eliminate some hard-to-detect bugs. We've been brainstorming on
>>> how to do this without affecting backward compatibility and
>>> introducing a minimal impact on keywords.
>>> We'd love to know what you think of our idea, which is to introduce
>>> "role" keywords. Roles allow the compiler to automatically check the
>>> intended use of a extension member definition against its protocol
>>> declarations, and emit errors, warnings, and fixits as needed.  We
>>> think it's a pretty straightforward approach that, if adopted,
>>> eliminates an entire category of bugs.
>>> The draft proposal is here:
>>> https://gist.github.com/erica/14283fe18254489c1498a7069b7760c4
>>> <https://gist.github.com/erica/14283fe18254489c1498a7069b7760c4>
>>> Thanks in advance for your thoughtful feedback,
>> +1 on the idea of this.  
> ditto.  IMO it also makes the protocol extension much more expressive
> and easy to read.
> -- 
> -Dave

Pull request: https://github.com/apple/swift-evolution/pull/724 <https://github.com/apple/swift-evolution/pull/724>

-- E

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