<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div><blockquote type="cite" class=""><div class="">On Oct 7, 2016, at 10:44 AM, Goffredo Marocchi <<a href="mailto:panajev@gmail.com" class="">panajev@gmail.com</a>> wrote:</div><div class=""><div style="font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(254, 254, 254);" class="">I would say we should, I think we moved a bit hastily and the strict push for non subclassable by default and the sealed by default discussion may still yield nasty side effects that are exponentially costlier as we move to Swift 4+<br class=""></div></div></blockquote><div><br class=""></div>It sounds like you're talking about re-opening the public/open class discussion, which is not the discussion I understand Adrian to be asking about.</div><div><br class=""></div><div>If people would like to talk about adding some way to express a protocol that can be implemented only internally but still used elsewhere, they should feel free. The core team isn't inviting that kind of formal proposal yet, but that shouldn't prevent any discussion here. However, please understand that changing the interpretation of "public" would be a source-breaking change and therefore needs to meet a much higher bar in 4.0 than it would have in 3.0; that may significantly shape your discussion.</div><div><br class=""></div><div>John.</div><div><br class=""><blockquote type="cite" class=""><div class=""><div style="font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(254, 254, 254);" class=""><br class="">Sent from my iPhone</div><div style="font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(254, 254, 254);" class=""><br class="">On 7 Oct 2016, at 17:40, Adrian Zubarev via swift-evolution <<a href="mailto:swift-evolution@swift.org" style="color: rgb(65, 131, 196); background-color: inherit; text-decoration: none;" class="">swift-evolution@swift.org</a>> wrote:<br class=""><br class=""></div><blockquote type="cite" style="margin: 15px 0px; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(254, 254, 254);" class=""><div style="margin-top: 0px; margin-bottom: 0px;" class=""><div class="bloop_markdown"><p style="margin: 15px 0px; -webkit-margin-before: 0px;" class="">Shall we revive this discussion?</p><div style="margin: 15px 0px;" class=""><br class="webkit-block-placeholder"></div></div><div class="bloop_original_html"><div id="bloop_customfont" style="font-family: Helvetica, Arial; font-size: 13px; margin: 0px;" class=""><br class=""></div><br class=""><div id="bloop_sign_1475858278199183104" class="bloop_sign"><div style="font-family: helvetica, arial; font-size: 13px;" class="">-- <br class="">Adrian Zubarev<br class="">Sent with Airmail</div></div><br class=""><p class="airmail_on" style="margin: 15px 0px;">Am 25. August 2016 um 19:29:13, John McCall (<a href="mailto:rjmccall@apple.com" style="color: rgb(65, 131, 196); background-color: inherit; text-decoration: none;" class="">rjmccall@apple.com</a>) schrieb:</p><blockquote type="cite" class="clean_bq" style="margin: 15px 0px;"><span style="margin-top: 0px; margin-bottom: 0px;" class=""><div class="" style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;"><div class=""></div><div class=""><div class=""><blockquote type="cite" class="" style="margin: 15px 0px;"><div class="" style="margin-top: 0px;">On Aug 25, 2016, at 2:29 AM, Karl via swift-evolution <<a href="mailto:swift-evolution@swift.org" class="" style="color: rgb(65, 131, 196); background-color: inherit; text-decoration: none;">swift-evolution@swift.org</a>> wrote:</div><div class="" style="margin-bottom: 0px;"><div class="" style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;">This is not a new inconsistency. We’ve known about this since “open” was first proposed.<div class=""><br class=""></div><div class="">Having sealed protocols would be nice, but it’s too late for Swift 3 IMO.</div></div></div></blockquote><div class=""><br class=""></div>Everything is too late for Swift 3. Bug fixes are about to be too late for Swift 3, much less any actual language changes.</div><div class=""><br class=""></div><div class="">John.</div><div class=""><br class=""><blockquote type="cite" class="" style="margin: 15px 0px;"><div class="" style="margin-top: 0px; margin-bottom: 0px;"><div class="" style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;"><div class=""><br class=""></div><div class="">Karl</div><div class=""><br class=""><div class=""><blockquote type="cite" class="" style="margin: 15px 0px;"><div class="" style="margin-top: 0px;">On 22 Aug 2016, at 20:40, Adrian Zubarev via swift-evolution <<a href="mailto:swift-evolution@swift.org" class="" style="color: rgb(65, 131, 196); background-color: inherit; text-decoration: none;">swift-evolution@swift.org</a>> wrote:</div><br class="Apple-interchange-newline"><div class="" style="margin-bottom: 0px;"><div class="bloop_markdown" style="font-family: Helvetica, Arial; font-size: 13px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(254, 254, 254);"><p class="" style="margin: 15px 0px; -webkit-margin-before: 0px;">Hello dear Swift community,</p><p class="" style="margin: 15px 0px;">I was updating some of my libraries where I noticed that the new<span class="Apple-converted-space"> </span><code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal; -webkit-margin-before: 0px;">open</code><span class="Apple-converted-space"> </span>access modifier made the<span class="Apple-converted-space"> </span><code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;">public</code><span class="Apple-converted-space"> </span>modifier inconsistent in one way.</p><p class="" style="margin: 15px 0px;">Conformances to protocols is logically the same as inheritances on classes.<span class="Apple-converted-space"> </span></p><ul class="" style="margin: 15px 0px;"><li class="" style="margin: 15px 0px; -webkit-margin-before: 0px;"><code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal; -webkit-margin-before: 0px;">Conformances == (abstract) inheritance</code></li></ul><p class="" style="margin: 15px 0px;">That said we should allow protocols to be<span class="Apple-converted-space"> </span><code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal; -webkit-margin-before: 0px;">open/public</code><span class="Apple-converted-space"> </span>like we now allow this distinction for classes.</p><ul class="" style="margin: 15px 0px;"><li class="" style="margin: 15px 0px; -webkit-margin-before: 0px;"><code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal; -webkit-margin-before: 0px;">open protocol</code><span class="Apple-converted-space"> </span>from module A should mean that I’m allowed to conform to it in module B</li><li class="" style="margin: 15px 0px;"><code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal; -webkit-margin-before: 0px;">public protocol</code><span class="Apple-converted-space"> </span>will act as an interface in module B</li></ul><p class="" style="margin: 15px 0px;">Not only sounds this behavior like ‘nice to have’, it’s inconsistency and it’s a ‘really need’ + a source breaking change in general.</p><p class="" style="margin: 15px 0px;">A common mistake in Swift 3.0 would be to hide protocol members behind<span class="Apple-converted-space"> </span><code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal; -webkit-margin-before: 0px;">public</code><span class="Apple-converted-space"> </span>modifier for protocols that meant to be<span class="Apple-converted-space"> </span><code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;">open</code>. If a protocol member in an open class is disallowed to be overridden by the<span class="Apple-converted-space"> </span><code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;">public</code><span class="Apple-converted-space"> </span>modifier and this behavior is fixed, that will imply that you’ll have to open the member which you intended to be not overridable.<span class="Apple-converted-space"> </span></p><pre class="" style="margin: 15px 0px; font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(204, 204, 204); overflow: auto; padding: 4px 8px; word-break: normal; word-wrap: normal;"><code class="swift" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 0px; margin: 0px; padding: 0px; word-break: normal; word-wrap: normal; -webkit-margin-before: 0px;">// Before:
// In module A
public protocol Proto {
func doSomething()
}
open class Base : Proto {
// Dissallow to override - this would be a common mistake
public func doSomething() {}
}
// Used in module B - so it should be `open` after all
class Test : Proto {
func doSomething() {}
}
// After:
// In module A
open protocol Proto {
func doSomething()
}
open class Base : Proto {
// Whops we have to grant the ability to override this method now
// I made a mistake designing my protocol in Swift 3.0 :/
open func doSomething() {}
}
// In module B
class Test2 : Base {
// Uuuuuuh I can do bad things with this now if the module A was not redesigned to fix this. :)))
override func doSomething() {}
}
</code></pre><p class="" style="margin: 15px 0px;">Personally I don’t have any feeling of how huge the impact might be on Swift if this behavior will be fixed. I also cannot tell if it’s something for Swift 3.x or Swift 4.0.</p><div class="" style="margin: 15px 0px;"><br class="webkit-block-placeholder" style="-webkit-margin-before: 0px;"></div></div><div class="bloop_original_html" style="font-family: Helvetica, Arial; font-size: 13px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(254, 254, 254);"><div id="bloop_customfont" class="" style="font-family: Helvetica, Arial; font-size: 13px; margin: 0px;"><br class=""></div><br class=""><div id="bloop_sign_1471887332279883776" class="bloop_sign"><div class="" style="font-family: helvetica, arial; font-size: 13px;">-- <br class="">Adrian Zubarev<br class="">Sent with Airmail</div></div></div><div class="bloop_markdown" style="font-family: Helvetica, Arial; font-size: 13px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(254, 254, 254);"><div class="" style="-webkit-margin-before: 0px; margin: 15px 0px;"><br class="webkit-block-placeholder" style="-webkit-margin-before: 0px;"></div></div><span class="" style="font-family: Helvetica, Arial; font-size: 13px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(254, 254, 254); float: none; display: inline !important;">_______________________________________________</span><br class="" style="font-family: Helvetica, Arial; font-size: 13px; font-style: normal; font-variant-caps: normal; 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