[swift-evolution] [Review] SE-0117: Default classes to be non-subclassable publicly

plx plxswift at icloud.com
Wed Jul 6 09:23:52 CDT 2016

+1 except for the choice of names if I understand it correctly, but I want to make sure I understand it correctly.

The scenario I want to to make sure I understand is what happens for a class-cluster type pattern like the following:

  // Module A:
  public class PublicBaseClass {
    func someMethod() { /* placeholder here */ }

  private class PrivateSubclass : PublicBaseClass {
    override func someMethod() { /* new logic here */ }

…I think this would make `PublicBaseClass` effectively “final” (e.g. non-subclassable) from outside of Module A, but `PrivateSubclass` (and similar constructs, etc.) would still be allowed and work as one would expect?

If so, that’s what I’d want semantically, so +1 on that for the semantics.

*But*, that behavior means that it is *very* confusing to be using `subclassable` and `overridable` for what they mean in this protocol.

I usually stay out of bike shedding but these attributes are really poorly named IMHO; I’d *highly recommend* something like either the ugly-but-explicit `externally_subclassable` / `externally_overrideable` or something else entirely (like maybe `open`?) that avoids the confusion.

Apologies if this has already come up or is based upon a misunderstanding of the proposal.

> On Jul 5, 2016, at 6:11 PM, Chris Lattner via swift-evolution <swift-evolution at swift.org> wrote:
> Hello Swift community,
> The review of "SE-0117: Default classes to be non-subclassable publicly" begins now and runs through July 11. The proposal is available here:
> 	https://github.com/apple/swift-evolution/blob/master/proposals/0117-non-public-subclassable-by-default.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
> or, if you would like to keep your feedback private, directly to the review manager.
> What goes into a review?
> The goal of the review process is to improve the proposal under review through constructive criticism and contribute to 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
> Thank you,
> -Chris Lattner
> Review Manager
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