<html><head><meta http-equiv="Content-Type" content="text/html charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div class="">+1 from me. FWIW, the Objective-C one is syntactic.</div><div class=""><br class=""></div><div class="">Information from Radar: the request for this is <a href="rdar://problem/17408107" class="">rdar://problem/17408107</a> (plus a few duplicates). One of the dups suggests a variation where a subclass method can be declared as "refine" instead of "override" so that you can document that your <i class="">own</i> method is expected to call super. In this model, "@requires_super" could become something like "imposed". I personally think this doesn't add enough, especially since we wouldn't be publishing refine-vs-override in a library's public interface.</div><div class=""><br class=""></div><div class="">Jordan</div><br class=""><div><blockquote type="cite" class=""><div class="">On Dec 16, 2015, at 9:49 , Marc Knaup via swift-evolution <<a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div dir="ltr" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: 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="">Sounds reasonable since even the best flow analysis cannot ensure that all codepaths call the super implementation.<div class=""><br class=""></div><div class="">Some more edge cases:</div><div class=""><ul class=""><li class="">Calling super asynchronously by using it in a closure</li><li class="">Referring to the super implementation by assign it to a variable and call it later (is that really possible? never did that)</li></ul></div></div><div class="gmail_extra" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: 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 class="gmail_quote">On Wed, Dec 16, 2015 at 6:25 PM, Vester Gottfried<span class="Apple-converted-space"> </span><span dir="ltr" class=""><<a href="mailto:vester.gottfried@gmail.com" target="_blank" class="">vester.gottfried@gmail.com</a>></span><span class="Apple-converted-space"> </span>wrote:<br class=""><blockquote class="gmail_quote" style="margin: 0px 0px 0px 0.8ex; border-left-width: 1px; border-left-color: rgb(204, 204, 204); border-left-style: solid; padding-left: 1ex;"><div dir="ltr" class="">I would suggest that @requires_super only checks if a call to super is present at all. More detailed behaviour should be part of the functions documentation, because I think all possibilities cannot be checked easily by the compiler. For example a call to super my be required to happen early or late inside the function. But when too early or too late is can probably not been forseen by the compiler.</div><div class="HOEnZb"><div class="h5"><div class="gmail_extra"><br class=""><div class="gmail_quote">On Wed, Dec 16, 2015 at 5:46 PM, Marc Knaup<span class="Apple-converted-space"> </span><span dir="ltr" class=""><<a href="mailto:marc@knaup.koeln" target="_blank" class="">marc@knaup.koeln</a>></span><span class="Apple-converted-space"> </span>wrote:<br class=""><blockquote class="gmail_quote" style="margin: 0px 0px 0px 0.8ex; border-left-width: 1px; border-left-color: rgb(204, 204, 204); border-left-style: solid; padding-left: 1ex;"><div dir="ltr" class="">+1 always had such issues with UIViewController's lifecycle methods.<div class=""><br class=""></div><div class="">But edge cases need to be considered like "throws" for example.</div><div class="">Do I need to call super before I throw something?</div></div><div class=""><div class=""><div class="gmail_extra"><br class=""><div class="gmail_quote">On Wed, Dec 16, 2015 at 5:41 PM, Matthew Johnson via swift-evolution<span class="Apple-converted-space"> </span><span dir="ltr" class=""><<a href="mailto:swift-evolution@swift.org" target="_blank" class="">swift-evolution@swift.org</a>></span><span class="Apple-converted-space"> </span>wrote:<br class=""><blockquote class="gmail_quote" style="margin: 0px 0px 0px 0.8ex; border-left-width: 1px; border-left-color: rgb(204, 204, 204); border-left-style: solid; padding-left: 1ex;"><div style="word-wrap: break-word;" class="">+1 to this. Anything that helps ensure inheritance is thought through carefully and used correctly is a win.<div class=""><br class=""><div class=""><blockquote type="cite" class=""><div class=""><div class=""><div class="">On Dec 16, 2015, at 10:32 AM, Vester Gottfried via swift-evolution <<a href="mailto:swift-evolution@swift.org" target="_blank" class="">swift-evolution@swift.org</a>> wrote:</div><br class=""></div></div><div class=""><div class=""><div class=""><div dir="ltr" class=""><div class="">Some class based libraries/frameworks expect the consumer to subclass certain classes and override specific method and require that the super implementation of an overridden method is being called.</div><div class=""><br class=""></div><div class="">Not calling the super implementation is a common source of bugs that may be prevented if the compiler checks if super is called, like it does in some cases of init().</div><div class=""><br class=""></div><div class="">Example:<br class=""></div><div class=""><br class=""></div><div class="">class Box {</div><div class=""> @requires_super<br class=""></div><div class=""> <span class="Apple-converted-space"> </span>func addStuff() { ... }</div><div class="">}<br class=""></div><div class=""><br class=""></div><div class="">Overriding class Box's addStuff without calling super.addStuff() should result in an error</div><div class=""><br class=""></div><div class="">class Chest : Box {</div><div class=""> <span class="Apple-converted-space"> </span>override addStuff() {<br class=""></div><div class=""> // ERROR: addStuff() requires call to super.addStuff()</div><div class=""> <span class="Apple-converted-space"> </span>...</div><div class=""> <span class="Apple-converted-space"> </span>}</div><div class="">}<br class=""></div><div class=""><br class=""></div><div class="">Objective-C developers know this as NS_REQUIRES_SUPER and I think its worth thinking about adapting it.</div><div class=""><div class=""><br class=""></div><div class="">I hope my proposal was clear and thanks for reading,</div><div class=""><br class=""></div></div><div class="">Gottfried</div></div></div></div><img src="https://u2002410.ct.sendgrid.net/wf/open?upn=eLFMrKDT8iBxZ-2Fbnk-2BZqvSchNN-2FvYXdceA0T7VxwkAfetdXVtelgzCfab-2Fp92fvLNUbxvC5Ukh9mTRYtT7oZ-2BzUDHQ-2FkLVfwWHuXGWvz7iaXCPo1KAcjPGxoZUQTW8DMleErzJnIt-2FRMb1-2FEM1WN-2BscY0xmKk-2BmXO16SS-2BCT9-2B7dgbk1nlmgpvH5cNha2dTvKe3-2FSntENn88F21K4ayGJlZuPediCmd1qI2SGJLz5ZQ-3D" alt="" width="1" height="1" border="0" style="min-height: 1px !important; 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