Yes, but to be clear, this is an objection that is equally applicable to any change where a protocol requirement is given a default implementation.<br><br>Unless I’m mistaken, ordinarily, the addition of such a default implementation isn’t even considered an API change and doesn’t require Swift Evolution approval.<br><div class="gmail_quote"><div dir="ltr">On Thu, Aug 10, 2017 at 16:41 David Ungar <<a href="mailto:dungar@apple.com">dungar@apple.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word;line-break:after-white-space">As long as I've been clear that the adoption of *this* proposal would transform a misspelling from a bug that the compiler catches to a bug that the compiler does not catch, I feel that my objection has been heard.<div><br></div><div>Thank you all,</div><div><br></div><div>- David</div></div><div style="word-wrap:break-word;line-break:after-white-space"><div><br><div><br><blockquote type="cite"><div>On Aug 10, 2017, at 1:51 PM, Xiaodi Wu <<a href="mailto:xiaodi.wu@gmail.com" target="_blank">xiaodi.wu@gmail.com</a>> wrote:</div><br class="m_-3234872308753257105Apple-interchange-newline"><div>Right. The objection raised is applicable to the overriding of any default implementation. However. _this_ proposal under review is about the synthesis of a default implementation, and we shouldn’t try to invent new syntax to address an orthogonal issue—and only partially at that.<br><div class="gmail_quote"><div dir="ltr">On Thu, Aug 10, 2017 at 14:45 Robert Bennett via swift-evolution <<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word">Yes, thanks! Here’s the full proposal for those interested: <a href="https://github.com/erica/swift-evolution/blob/c541f517dacc2030c987b6d60ad3d26d8ec5fa3a/proposals/XXXX-role-keywords.md" target="_blank">https://github.com/erica/swift-evolution/blob/c541f517dacc2030c987b6d60ad3d26d8ec5fa3a/proposals/XXXX-role-keywords.md</a><div><br></div><div>I think that if we want to deal with the issue of some mistake arising from conforming to Equatable and/or Hashable, it should be through that proposal, not something specific to Equatable and Hashable. This sort of issue should not count against this Equatable/Hashable proposal.</div></div><div style="word-wrap:break-word"><div><br><div><blockquote type="cite"><div>On Aug 10, 2017, at 3:39 PM, Chris Lattner <<a href="mailto:clattner@nondot.org" target="_blank">clattner@nondot.org</a>> wrote:</div><br class="m_-3234872308753257105m_940041053373071184Apple-interchange-newline"><div><blockquote type="cite" style="font-family:Helvetica;font-size:13px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px"><br class="m_-3234872308753257105m_940041053373071184Apple-interchange-newline">On Aug 10, 2017, at 12:24 PM, Robert Bennett via swift-evolution <<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>> wrote:<br><br>I could have sworn that this sort of issue came up on this list earlier this year… Someone proposed a mechanism encompassing all protocols, not just Equatable and Hashable, to handle the issue of mistakenly believing you’re overriding a default implementation. Having trouble finding it at the moment.<br></blockquote><br style="font-family:Helvetica;font-size:13px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px"><span style="font-family:Helvetica;font-size:13px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;float:none;display:inline!important">Is this what you’re thinking of?</span><br style="font-family:Helvetica;font-size:13px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px"><a href="https://github.com/apple/swift-evolution/pull/724" style="font-family:Helvetica;font-size:13px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px" target="_blank">https://github.com/apple/swift-evolution/pull/724</a><br style="font-family:Helvetica;font-size:13px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px"><br style="font-family:Helvetica;font-size:13px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px"><span style="font-family:Helvetica;font-size:13px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;float:none;display:inline!important">-Chris</span><br style="font-family:Helvetica;font-size:13px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px"><br style="font-family:Helvetica;font-size:13px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px"><br style="font-family:Helvetica;font-size:13px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px"><br style="font-family:Helvetica;font-size:13px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px"><blockquote type="cite" style="font-family:Helvetica;font-size:13px;font-style:normal;font-variant-caps:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">.<br><br><blockquote type="cite">On Aug 10, 2017, at 3:09 PM, David Ungar via swift-evolution <<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>> wrote:<br><br>If I understand it, merely adding Equatable or Hashable will cause the compiler to synthesize requirements. This syntax opens up the possibility for errors:<br><br>struct Snort: Hashable {<br>static var hashValu /* NOTE MISSPELLING */ : Int { return 666 }<br>}<br><br>In the above example, the programmer meant to implement hashValue but misspelled it.<br>With the proposal as-is, the error could be covered up.<br><br>I would prefer to see a different syntax than merely adding conformance to "HashValue", in order to distinguish the two cases: explicit supplying the requirement vs synthesis.<br><br>Also, what if we want to extend this idea to other protocols? Perhaps some sort of modifier on the protocol name would be more orthogonal:<br><br>struct Foo: Synth Hashable, Equatable<span class="m_-3234872308753257105m_940041053373071184Apple-converted-space"> </span><br><br>Would say that Hashable requirements get synthesized but Equatable ones do not.<br><br>Alternatively, it might be clearer, though more verbose to move the signalling inside:<br><br>struct Snort: Hashable {<br>synth hashValue<br>}<br><br>(I don't advocate this specific syntax, btw.) But it has the virtual of possibly making it clearer to read the code.<br><br>TL;DR: I favor the proposal but would prefer modification to make it more explicit.<br>_______________________________________________<br>swift-evolution mailing list<br><a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a><br><a href="https://lists.swift.org/mailman/listinfo/swift-evolution" target="_blank">https://lists.swift.org/mailman/listinfo/swift-evolution</a><br></blockquote><br>_______________________________________________<br>swift-evolution mailing list<br><a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a><br><a href="https://lists.swift.org/mailman/listinfo/swift-evolution" target="_blank">https://lists.swift.org/mailman/listinfo/swift-evolution</a></blockquote></div></blockquote></div><br></div></div>_______________________________________________<br>
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