<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">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 class=""><br class=""></div><div class="">Thank you all,</div><div class=""><br class=""></div><div class="">- David<br class=""><div><br class=""><blockquote type="cite" class=""><div class="">On Aug 10, 2017, at 1:51 PM, Xiaodi Wu <<a href="mailto:xiaodi.wu@gmail.com" class="">xiaodi.wu@gmail.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class="">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 class=""><div class="gmail_quote"><div dir="ltr" class="">On Thu, Aug 10, 2017 at 14:45 Robert Bennett via swift-evolution <<a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a>> wrote:<br class=""></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" class="">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" class="">https://github.com/erica/swift-evolution/blob/c541f517dacc2030c987b6d60ad3d26d8ec5fa3a/proposals/XXXX-role-keywords.md</a><div class=""><br class=""></div><div class="">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" class=""><div class=""><br class=""><div class=""><blockquote type="cite" class=""><div class="">On Aug 10, 2017, at 3:39 PM, Chris Lattner <<a href="mailto:clattner@nondot.org" target="_blank" class="">clattner@nondot.org</a>> wrote:</div><br class="m_940041053373071184Apple-interchange-newline"><div class=""><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" class=""><br class="m_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" class="">swift-evolution@swift.org</a>> wrote:<br class=""><br class="">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 class=""></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" class=""><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" class="">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" class=""><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" class="">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" class=""><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" class=""><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" class="">-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" class=""><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" class=""><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" class=""><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" class=""><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" class="">.<br class=""><br class=""><blockquote type="cite" class="">On Aug 10, 2017, at 3:09 PM, David Ungar via swift-evolution <<a href="mailto:swift-evolution@swift.org" target="_blank" class="">swift-evolution@swift.org</a>> wrote:<br class=""><br class="">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 class=""><br class="">struct Snort: Hashable {<br class="">static var hashValu /* NOTE MISSPELLING */ : Int { return 666 }<br class="">}<br class=""><br class="">In the above example, the programmer meant to implement hashValue but misspelled it.<br class="">With the proposal as-is, the error could be covered up.<br class=""><br class="">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 class=""><br class="">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 class=""><br class="">struct Foo: Synth Hashable, Equatable<span class="m_940041053373071184Apple-converted-space"> </span><br class=""><br class="">Would say that Hashable requirements get synthesized but Equatable ones do not.<br class=""><br class="">Alternatively, it might be clearer, though more verbose to move the signalling inside:<br class=""><br class="">struct Snort: Hashable {<br class="">synth hashValue<br class="">}<br class=""><br class="">(I don't advocate this specific syntax, btw.) But it has the virtual of possibly making it clearer to read the code.<br class=""><br class="">TL;DR: I favor the proposal but would prefer modification to make it more explicit.<br class="">_______________________________________________<br class="">swift-evolution mailing list<br class=""><a href="mailto:swift-evolution@swift.org" target="_blank" class="">swift-evolution@swift.org</a><br class=""><a href="https://lists.swift.org/mailman/listinfo/swift-evolution" target="_blank" class="">https://lists.swift.org/mailman/listinfo/swift-evolution</a><br class=""></blockquote><br class="">_______________________________________________<br class="">swift-evolution mailing list<br class=""><a href="mailto:swift-evolution@swift.org" target="_blank" class="">swift-evolution@swift.org</a><br class=""><a href="https://lists.swift.org/mailman/listinfo/swift-evolution" target="_blank" class="">https://lists.swift.org/mailman/listinfo/swift-evolution</a></blockquote></div></blockquote></div><br class=""></div></div>_______________________________________________<br class="">
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