<div dir="ltr">This works today:<div><br></div><div><div>protocol P1{}</div><div>protocol P2{}</div><div><br></div><div>extension P1 where Self: P2 {</div><div> func foo() {}</div><div>}</div><div><br></div><div>func bar(x: P1 & P2) {</div><div> x.foo()</div><div>}</div></div><div><br></div><div class="gmail_extra">
<br><div class="gmail_quote">On Tue, Feb 21, 2017 at 10:53 PM, David Hart 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:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div style="word-wrap:break-word">Hello list,<div><br></div><div>Found out yesterday that you can’t extend all existentials in Swift:</div><div><br></div><div><font face="Menlo">protocol P1 {}</font></div><div><font face="Menlo">extension P1 {}</font></div><div><font face="Menlo">// works as expected</font></div><div><font face="Menlo"><br></font></div><div><font face="Menlo">protocol P2 {}</font></div><div><font face="Menlo">extension P1 & P2 {}</font></div><div><font face="Menlo">// error: non-nominal type 'P1 & P2' cannot be extended</font></div><div><font face="Menlo"><br></font></div><div><font face="Menlo">extension Any {}</font></div><div><font face="Menlo">// error: non-nominal type 'Any' cannot be extended</font></div><div><font face="Menlo"><br></font></div><div><font face="Menlo">extension AnyObject {}</font></div><div><font face="Menlo">// error: 'AnyObject' protocol cannot be extended</font></div><div><br></div><div>I’d like to write a proposal to lift some of those restrictions. But the question is: which should be lifted? <font face="Menlo">P1 & P2</font> seems like an obvious case. But what about <font face="Menlo">Any</font> and <font face="Menlo">AnyObject</font>? Is there a design reason that we shouldn’t allow it?</div><span class="gmail-HOEnZb"><font color="#888888"><div><br></div><div>David.</div></font></span></div><br>______________________________<wbr>_________________<br>
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