<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto"><div><span></span></div><div><div><span></span></div><div><div><span></span></div><div><div><span></span></div><div><div><br><br>~Robert Widmann</div><div><br>2016/08/23 20:52、Charles Srstka <<a href="mailto:cocoadev@charlessoft.com">cocoadev@charlessoft.com</a>> のメッセージ:<br><br></div><blockquote type="cite"><div><meta http-equiv="Content-Type" content="text/html charset=utf-8"><blockquote type="cite" class="">On Aug 23, 2016, at 10:34 PM, Robert Widmann <<a href="mailto:devteam.codafi@gmail.com" class="">devteam.codafi@gmail.com</a>> wrote:<br class=""></blockquote><div><blockquote type="cite" class=""><br class="Apple-interchange-newline"><div class=""><div style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class="">2016/08/23 15:29、Charles Srstka <<a href="mailto:cocoadev@charlessoft.com" class="">cocoadev@charlessoft.com</a>> のメッセージ:<br class=""><br class=""></div><blockquote type="cite" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><div class=""><blockquote type="cite" class="">On Aug 23, 2016, at 2:33 PM, Robert Widmann via swift-evolution <<a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a>> wrote:<br class=""></blockquote><div class=""><blockquote type="cite" class=""><br class="Apple-interchange-newline"><div class=""><div class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;">2016/08/22 14:30、David Cordero via swift-evolution <<a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a>> のメッセージ:<br class=""><br class=""></div><blockquote type="cite" class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;"><div class=""><div dir="ltr" class=""><br class=""><div class=""><b class="">The problem:</b></div><div class="">At the moment, looking at the code of a class or a struct implementing a protocol, it is hard to know what methods are actually implementing the protocol and what other methods are just part of the code of the class or struct.<br class=""></div><div class=""><br class=""></div></div></div></blockquote><div class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;"><br class=""></div><div class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;">That seems like a feature, not a bug. Why should I as an author care whether a method contributes to a protocol conformance or not if the compiler can tell me that kind of information itself?</div></div></blockquote><div class=""><br class=""></div><div class="">Being able to reason about your code, what it does, and what it’s for is undesirable?</div></div></div></blockquote><div style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><br class=""></div><div style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class="">That's not an answer to the question I asked. Why is this significant enough to warrant an entire keyword? The clutter of a whole keyword that does nothing but wait for a developer to make a source-compatible binary-breaking change to an interface does not seem worth it. Maybe you can convince me otherwise. </div></div></blockquote><div><br class=""></div><div>Same reason overriding a class method warrants a keyword. It expresses the purpose more clearly, and allows the compiler to catch mistakes for us.</div><br class=""></div></div></blockquote><div><br></div><div>That's just it: The class of mistakes one can make by not being explicit about overrides is significantly more dangerous than the class of mistakes caused by dead code leftover from trimming protocols.</div><div><br></div><blockquote type="cite"><div><div><blockquote type="cite" class=""><div class=""><blockquote type="cite" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><div class=""><div class=""><blockquote type="cite" class=""><blockquote type="cite" class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;"><div class=""><div dir="ltr" class=""><div class="">```</div></div></div></blockquote><blockquote type="cite" class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;"><div class=""><div dir="ltr" class=""><div class="">protocol MyProtocol {</div><div class=""> func myMethod() -> String</div><div class="">}</div><div class=""><br class=""></div><div class="">class MyClass: MyProtocol {</div><div class=""><br class=""></div><div class=""> <span class="Apple-converted-space"> </span><b class="">conform</b> func myMethod() -> String {</div><div class=""> return "Yuhuuu,I am conforming<span class="Apple-converted-space"> </span><a href="smb://o//" class="">\\o//</a>"</div><div class=""> }</div><div class=""><br class=""></div><div class=""> func whatever() {</div><div class=""> print("I am a boring method and I don't conform anything")</div><div class=""> }</div><div class="">}</div><div class="">```</div><div class=""><br class=""></div><div class="">It would be something similar to the current keyword `override` but for protocols. </div><div class=""><br class=""></div><div class="">Apart from improving code readability, It would allow the detection, in compilation time, of errors due to code evolution. For example redundant methods that no longer conform anything once the requirement is removed from the protocol for whatever reason.</div></div></div></blockquote><div class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;"><br class=""></div><div class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;">If you make a breaking change to a protocol like this, you should have gone through a deprecation cycle to indicate to your clients the appropriate changes you're going to make to the protocol. This aspect of the change seems to if not encourage, highlight, bad behavior.</div></blockquote></div><br class=""><div class="">What if it’s your own code and all the callers are internal? What if you’re still developing the protocol and haven’t released the API interface yet?</div></div></blockquote><div style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><br class=""></div><div style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class="">Then your concerns are local enough that you know where<span class="Apple-converted-space"> </span><i class="">all</i> implementations of the protocol lie and whether they require deletion or not. The point about deprecation cycles still stands in all the cases you mention. Just because the interface is private doesn't mean you can't take responsibility for keeping it as clean as you can.</div><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><blockquote type="cite" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><div class=""><div class=""><br class=""></div><div class="">Charles</div><div class=""><br class=""></div></div></blockquote><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><div style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class="">tl;dr It seems like all of this can be subsumed by us warning about dead code.</div></div></blockquote></div><br class=""><div class="">Did you look at my examples earlier in the thread? Neither of those would be caught by warning about dead code.</div></div></blockquote><div><br></div><div>The example involving the default implementation is most compelling, but it indicates that your proposed solution should focus on the protocol extension and not the implementing declaration. Perhaps reusing one of our existing keywords can help here</div><div><br></div><div><div><span style="background-color: rgba(255, 255, 255, 0);">protocol P {</span></div><div> <span style="background-color: rgba(255, 255, 255, 0);"> func foo() {}</span></div><div><span style="background-color: rgba(255, 255, 255, 0);">}</span></div><div><span style="background-color: rgba(255, 255, 255, 0);"><br></span></div><div><span style="background-color: rgba(255, 255, 255, 0);">extension P {</span></div><div> <span style="background-color: rgba(255, 255, 255, 0);"> default func foo() {}</span></div><div><span style="background-color: rgba(255, 255, 255, 0);">}</span></div><div><br></div><div><span style="background-color: rgba(255, 255, 255, 0);">struct S: P {}</span></div></div><div><br></div><div>Of course, this change would be potentially source-breaking either way - I don't like the sound of an "optional keyword". </div><div><br></div><div>Either way, we can all agree we need better diagnostics around these cases.</div><div><br></div><blockquote type="cite"><div><div class=""><br class=""></div><div class="">Charles</div><div class=""><br class=""></div></div></blockquote></div></div></div></div></body></html>