<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 Jul 31, 2017, at 1:19 AM, Xiaodi Wu <<a href="mailto:xiaodi.wu@gmail.com" class="">xiaodi.wu@gmail.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div dir="ltr" class="">Daryle, this discussion has indeed taken place before. One good place to start is the Google result for "swift evolution non-conformance".</div></div></blockquote><div><br class=""></div><div>I added SR-5589, to request a counter protocol to AnyObject.</div><div><br class=""></div><blockquote type="cite" class=""><div class=""><div class="gmail_extra"><div class="gmail_quote">On Sun, Jul 30, 2017 at 5:30 PM, Daryle Walker via swift-evolution <span dir="ltr" class=""><<a href="mailto:swift-evolution@swift.org" target="_blank" class="">swift-evolution@swift.org</a>></span> wrote:<br class=""><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><span class=""><br class="">
> On Jul 30, 2017, at 5:03 PM, Tino Heth <<a href="mailto:2th@gmx.de" class="">2th@gmx.de</a>> wrote:<br class="">
><br class="">
>> [Apologies if this is in Swift 4 already.]<br class="">
>><br class="">
>> We can have generic parameters match a protocol. But I have an idea in my head that involves the type NOT conforming to a protocol. I don’t think we have a way currently to work with this.<br class="">
> Why do you want that?<br class="">
> When something conforms, you know that you can call the methods of the protocol, but without conformance, you can't do anything that's not possible using "is".<br class="">
> Also:<br class="">
> Don't forget retroactive conformance — you can never rely on non-conformance.<br class="">
<br class="">
</span>I forgot about that last part. But my idea still has merit, due to why I desired it in the first place.<br class="">
<br class="">
The “AnyObject” protocol is marked on all class types. All class types conform to it, and it’s illegal (as I understand it) to put on a type that isn’t already a class. I have been working on a “strong type-alias” proposal, and it has a similar protocol. And I came up with ideas that depend on a type NOT being a strong type-alias. That’s what prompted the post. Note that these protocols cannot be retroactively applied, so negation has merit.<br class="">
<br class="">
Since there’s a limited number of them, a better solution could be to add a “NeverAnObject” protocol that’s automatically slapped onto non-class types (and cannot be added onto class types). And like “AnyObject,” it can be a base protocol, but this time it forces the conforming protocol to not be for classes.<br class=""></blockquote></div></div></div></blockquote></div><br class=""><div class=""><div class=""><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div class="">— </div><div class="">Daryle Walker<br class="">Mac, Internet, and Video Game Junkie<br class="">darylew AT mac DOT com </div><div class=""><br class=""></div></div></div></div></body></html>