<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=""><br class=""><div><blockquote type="cite" class=""><div class="">On Feb 21, 2017, at 11:34 PM, Adrian Zubarev via swift-evolution <<a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><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 style="margin: 15px 0px; -webkit-margin-before: 0px;" class="">I’d love if we could extend the idea even further. It would be great to be able to extend the typealias type, because it can be a more constrained type (with a where clause).</p><pre 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;" class=""><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;">protocol P {
associatedtype Q
}
class C {}
typealias CP = C & P where Q == Int
extension CP { … }
</code></pre><p style="margin: 15px 0px;" class="">This would make a lot of constrained extension vanish.</p><div class=""><br class=""></div></div></div></blockquote><br class="">Once we have generalized existentials, it should be possible to make something like the above desugar into a constrained extension.</div><div><br class=""></div><div>Slava<br class=""><blockquote type="cite" class=""><div class=""><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 style="margin: 15px 0px;" class=""><br class="webkit-block-placeholder"></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" style="font-family: Helvetica, Arial; font-size: 13px; margin: 0px;" class=""><br class=""></div><br class=""><div id="bloop_sign_1487748590962904064" 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 22. Februar 2017 um 08:26:33, David Hart 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>) schrieb:</p><blockquote type="cite" class="clean_bq" style="margin: 15px 0px;"><span style="margin-top: 0px; margin-bottom: 0px;" class=""><div dir="auto" class=""><div class=""></div><div class=""><div class="">Yes, but it's not very discoverable. Plus, if the subclass existentials proposal is accepted, it would actually allow us to do:</div><div class=""><br class=""></div><div class="">class C {}</div><div class="">extension C & P1 {}</div><div class=""><br class="">On 22 Feb 2017, at 08:06, Jacob Bandes-Storch <<a href="mailto:jtbandes@gmail.com" style="color: rgb(65, 131, 196); background-color: inherit; text-decoration: none;" class="">jtbandes@gmail.com</a>> wrote:<br class=""><br class=""></div><blockquote type="cite" style="margin: 15px 0px;" class=""><div style="margin-top: 0px; margin-bottom: 0px;" class=""><div dir="ltr" class="">This works today:<div class=""><br class=""></div><div class=""><div class="">protocol P1{}</div><div class="">protocol P2{}</div><div class=""><br class=""></div><div class="">extension P1 where Self: P2 {</div><div class=""> func foo() {}</div><div class="">}</div><div class=""><br class=""></div><div class="">func bar(x: P1 & P2) {</div><div class=""> x.foo()</div><div class="">}</div></div><div class=""><br class=""></div><div class="gmail_extra"><br class=""><div class="gmail_quote">On Tue, Feb 21, 2017 at 10:53 PM, David Hart via swift-evolution<span class="Apple-converted-space"> </span><span dir="ltr" class=""><<a href="mailto:swift-evolution@swift.org" target="_blank" style="color: rgb(65, 131, 196); background-color: inherit; text-decoration: none;" class="">swift-evolution@swift.org</a>></span><span class="Apple-converted-space"> </span>wrote:<br class=""><blockquote class="gmail_quote" style="margin: 0px 0px 0px 0.8ex; border-left-width: 1px; border-left-style: solid; border-left-color: rgb(204, 204, 204); padding-left: 1ex;"><div style="margin-top: 0px; word-wrap: break-word;" class="">Hello list,<div class=""><br class=""></div><div class="">Found out yesterday that you can’t extend all existentials in Swift:</div><div class=""><br class=""></div><div class=""><font face="Menlo" class="">protocol P1 {}</font></div><div class=""><font face="Menlo" class="">extension P1 {}</font></div><div class=""><font face="Menlo" class="">// works as expected</font></div><div class=""><font face="Menlo" class=""><br class=""></font></div><div class=""><font face="Menlo" class="">protocol P2 {}</font></div><div class=""><font face="Menlo" class="">extension P1 & P2 {}</font></div><div class=""><font face="Menlo" class="">// error: non-nominal type 'P1 & P2' cannot be extended</font></div><div class=""><font face="Menlo" class=""><br class=""></font></div><div class=""><font face="Menlo" class="">extension Any {}</font></div><div class=""><font face="Menlo" class="">// error: non-nominal type 'Any' cannot be extended</font></div><div class=""><font face="Menlo" class=""><br class=""></font></div><div class=""><font face="Menlo" class="">extension AnyObject {}</font></div><div class=""><font face="Menlo" class="">// error: 'AnyObject' protocol cannot be extended</font></div><div class=""><br class=""></div><div class="">I’d like to write a proposal to lift some of those restrictions. But the question is: which should be lifted?<span class="Apple-converted-space"> </span><font face="Menlo" class="">P1 & P2</font><span class="Apple-converted-space"> </span>seems like an obvious case. But what about<span class="Apple-converted-space"> </span><font face="Menlo" class="">Any</font><span class="Apple-converted-space"> </span>and<span class="Apple-converted-space"> </span><font face="Menlo" class="">AnyObject</font>? Is there a design reason that we shouldn’t allow it?</div><div class=""><span class="gmail-HOEnZb"><font color="#888888" class=""><br class=""></font></span></div><div class=""><span class="gmail-HOEnZb"><font color="#888888" class="">David.</font></span></div></div><br class="">______________________________<wbr class="">_________________<br class="">swift-evolution mailing list<br class=""><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><br class=""><a href="https://lists.swift.org/mailman/listinfo/swift-evolution" rel="noreferrer" target="_blank" style="color: rgb(65, 131, 196); background-color: inherit; text-decoration: none;" class="">https://lists.swift.org/<wbr class="">mailman/listinfo/swift-<wbr class="">evolution</a><br class=""><br style="margin-bottom: 0px;" class=""></blockquote></div><br class=""></div></div></div></blockquote>_______________________________________________<br class="">swift-evolution mailing list<br class=""><a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a><br class="">https://lists.swift.org/mailman/listinfo/swift-evolution<br class=""></div></div></span></blockquote></div><div class="bloop_markdown" style="font-family: Helvetica, Arial; 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