<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto"><div>Calling super asynchronously would not meet an @requires_super specification IMO. I would interpret it to mean you must call super before returning.</div><div id="AppleMailSignature"><br></div><div id="AppleMailSignature">The compiler already guarantees all code paths return and guarantees subclass initializers call super. I don't think a sensible definition of <span style="background-color: rgba(255, 255, 255, 0);">@requires_super would be any more complex than that. </span></div><div id="AppleMailSignature"><br>Sent from my iPad</div><div><br>On Dec 16, 2015, at 11:49 AM, Marc Knaup <<a href="mailto:marc@knaup.koeln">marc@knaup.koeln</a>> wrote:<br><br></div><blockquote type="cite"><div><div dir="ltr">Sounds reasonable since even the best flow analysis cannot ensure that all codepaths call the super implementation.<div><br></div><div>Some more edge cases:</div><div><ul><li>Calling super asynchronously by using it in a closure</li><li>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"><br><div class="gmail_quote">On Wed, Dec 16, 2015 at 6:25 PM, Vester Gottfried <span dir="ltr"><<a href="mailto:vester.gottfried@gmail.com" target="_blank">vester.gottfried@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">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><div class="gmail_quote">On Wed, Dec 16, 2015 at 5:46 PM, Marc Knaup <span dir="ltr"><<a href="mailto:marc@knaup.koeln" target="_blank">marc@knaup.koeln</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">+1 always had such issues with UIViewController's lifecycle methods.<div><br></div><div>But edge cases need to be considered like "throws" for example.</div><div>Do I need to call super before I throw something?</div></div><div><div><div class="gmail_extra"><br><div class="gmail_quote">On Wed, Dec 16, 2015 at 5:41 PM, Matthew Johnson 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:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word">+1 to this. Anything that helps ensure inheritance is thought through carefully and used correctly is a win.<div><br><div><blockquote type="cite"><div><div><div>On Dec 16, 2015, at 10:32 AM, Vester Gottfried via swift-evolution <<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>> wrote:</div><br></div></div><div><div><div><div dir="ltr"><div>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><br></div><div>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><br></div><div>Example:<br></div><div><br></div><div>class Box {</div><div> @requires_super<br></div><div> func addStuff() { ... }</div><div>}<br></div><div><br></div><div>Overriding class Box's addStuff without calling super.addStuff() should result in an error</div><div><br></div><div>class Chest : Box {</div><div> override addStuff() {<br></div><div> // ERROR: addStuff() requires call to super.addStuff()</div><div> ...</div><div> }</div><div>}<br></div><div><br></div><div>Objective-C developers know this as NS_REQUIRES_SUPER and I think its worth thinking about adapting it.</div><div><div><br></div><div>I hope my proposal was clear and thanks for reading,</div><div><br></div></div><div>Gottfried</div></div>
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