<div dir="ltr">Daryle, this discussion has indeed taken place before. One good place to start is the Google result for "swift evolution non-conformance".</div><div class="gmail_extra"><br><div class="gmail_quote">On Sun, Jul 30, 2017 at 5:30 PM, Daryle Walker via swift-evolution <span dir="ltr"><<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><span class=""><br>
> On Jul 30, 2017, at 5:03 PM, Tino Heth <<a href="mailto:2th@gmx.de">2th@gmx.de</a>> wrote:<br>
><br>
>> [Apologies if this is in Swift 4 already.]<br>
>><br>
>> 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>
> Why do you want that?<br>
> 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>
> Also:<br>
> Don't forget retroactive conformance — you can never rely on non-conformance.<br>
<br>
</span>I forgot about that last part. But my idea still has merit, due to why I desired it in the first place.<br>
<br>
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>
<br>
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>
<br>
—<br>
<span class="im HOEnZb">Daryle Walker<br>
Mac, Internet, and Video Game Junkie<br>
darylew AT mac DOT com<br>
<br>
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