[swift-evolution] [Review] SE-0156: Class and Subtype existentials

[David Hart]

> On 28 Feb 2017, at 22:52, Christopher Kornher via swift-evolution <swift-evolution at swift.org> wrote:
> 
> What is your evaluation of the proposal?
> It seems to be a very straightforward and natural extension of existing syntax to bring Swift closer to the functionality of Objective-C and other languages. 
> 
> My only concern is that using `AnyObject` at first glance seems less descriptive  than ‘class’ when used in a protocol declaration, but it may be simply because I already familiar with the `class` syntax.

To be honest, I didn’t feel very strongly either way. But using class would make the following syntax valid and weird:

let a: class = Object()

So I followed the road of Objective-C, which uses the type generic class type (AnyObject) as the class constraint keyword.

> Is the problem being addressed significant enough to warrant a change to Swift?
> Absolutely. 
> 
> Does this proposal fit well with the feel and direction of Swift?
> Yes. It is a sensible extension to existing patters. Eliminating the redundancy and ambiguity in `class` and `AnyObject` eliminates a barrier to understanding the language and is probably worth the pain of deprecating `class` which I have used extensively in my code.
> 
> If you have used other languages or libraries with a similar feature, how do you feel that this proposal compares to those?
> I have used the feature numerous times in Objective-C over the years and this proposal is a perfect analog as far as I know.
> 
> How much effort did you put into your review? A glance, a quick reading, or an in-depth study?
> I gave the proposal a thorough reading. It is straightforward enough to not require much study.
> 
> 
> 
> 
>> On Feb 28, 2017, at 2:11 PM, Douglas Gregor via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>> 
>> Hello Swift community,
>> 
>> The review of SE-0156 "Class and Subtype existentials" begins now and runs through March 7, 2017. The proposal is available here:
>> 
>> https://github.com/apple/swift-evolution/blob/master/proposals/0156-subclass-existentials.md <https://github.com/apple/swift-evolution/blob/master/proposals/0156-subclass-existentials.md>
>> Reviews are an important part of the Swift evolution process. All reviews should be sent to the swift-evolution mailing list at
>> 
>> https://lists.swift.org/mailman/listinfo/swift-evolution <https://lists.swift.org/mailman/listinfo/swift-evolution>
>> or, if you would like to keep your feedback private, directly to the review manager. When replying, please try to keep the proposal link at the top of the message:
>> 
>> Proposal link:
>> 
>> https://github.com/apple/swift-evolution/blob/master/proposals/0156-subclass-existentials.md <https://github.com/apple/swift-evolution/blob/master/proposals/0156-subclass-existentials.md>
>> Reply text
>> 
>> Other replies
>>  <https://github.com/apple/swift-evolution/pull/607/files#what-goes-into-a-review-1>What goes into a review?
>> 
>> The goal of the review process is to improve the proposal under review through constructive criticism and, eventually, determine the direction of Swift. When writing your review, here are some questions you might want to answer in your review:
>> 
>> What is your evaluation of the proposal?
>> Is the problem being addressed significant enough to warrant a change to Swift?
>> Does this proposal fit well with the feel and direction of Swift?
>> If you have used other languages or libraries with a similar feature, how do you feel that this proposal compares to those?
>> How much effort did you put into your review? A glance, a quick reading, or an in-depth study?
>> More information about the Swift evolution process is available at
>> 
>> https://github.com/apple/swift-evolution/blob/master/process.md <https://github.com/apple/swift-evolution/blob/master/process.md>
>> Thank you,
>> 
>> -Doug
>> 
>> Review Manager
>> 
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> 
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