<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><br class=""><div><blockquote type="cite" class=""><div class="">On Jan 13, 2017, at 12:14 PM, Jonathan Hull 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=""><meta http-equiv="Content-Type" content="text/html charset=utf-8" class=""><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div class="">I think the “when all their associated values were Equatable” is the technical issue holding this type of thing up. The ability to spell that type of thing is on the generics roadmap, but I don’t know when it will actually happen. There seem to be a lot of things on hold because of it.</div></div></div></blockquote><div><br class=""></div><div>The proposal for conditional conformances was accepted. However, right now the generics feature being worked on is recursive conformances, together with a large overall cleanup of the generics implementation to fix bugs and improve correctness. Conditional conformances will come at some point after that.</div><div><br class=""></div><div>Slava</div><div><br class=""></div><blockquote type="cite" class=""><div class=""><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div class=""><br class=""></div><div class="">Thanks,</div><div class="">Jon</div><div class=""><br class=""><div class=""><blockquote type="cite" class=""><div class="">On Jan 13, 2017, at 11:51 AM, Adam Shin 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" class=""><div class="gmail_msg" style="font-size:13px">When using enums with associated values, it's often necessary to check for equality between two enum objects in some way. That can lead to boilerplate code like this:<br class="gmail_msg"></div><div class="gmail_msg" style="font-size:13px"><br class="gmail_msg"></div><div class="gmail_msg" style="font-size:13px">enum Option {</div><div class="gmail_msg" style="font-size:13px"> case foo(String)</div><div class="gmail_msg" style="font-size:13px"> case bar(Int)</div><div class="gmail_msg" style="font-size:13px"><span class="gmail_msg inbox-m_-1513968597867029764Apple-tab-span" style="white-space:pre-wrap"> </span>case zip</div><div class="gmail_msg" style="font-size:13px">}</div><div class="gmail_msg" style="font-size:13px"><br class="gmail_msg"></div><div class="gmail_msg" style="font-size:13px">func ==(lhs: Option, rhs: Option) -> Bool {</div><div class="gmail_msg" style="font-size:13px"> switch (lhs, rhs) {</div><div class="gmail_msg" style="font-size:13px"> case (.foo(let a), .foo(let b)) where a == b: return true</div><div class="gmail_msg" style="font-size:13px"> case (.bar(let a), .bar(let b)) where a == b: return true</div><div class="gmail_msg" style="font-size:13px"> case (.zip, .zip): return true</div><div class="gmail_msg" style="font-size:13px"> default: return false</div><div class="gmail_msg" style="font-size:13px"> }</div><div class="gmail_msg" style="font-size:13px">}</div><div class="gmail_msg" style="font-size:13px"><br class="gmail_msg"></div><div class="gmail_msg" style="font-size:13px">..which results in code duplication and opens the door to potential logic errors.</div><div class="gmail_msg" style="font-size:13px"><br class="gmail_msg"></div><div class="gmail_msg" style="font-size:13px">Instead, what if enums with associated values were automatically Equatable when all their associated values were Equatable? That would remove the need for such boilerplate code.</div><div class="gmail_msg" style="font-size:13px"><br class="gmail_msg"></div><div class="gmail_msg" style="font-size:13px">The Swift language guide states that custom classes and structs don't receive a default implementation of the == operator because the compiler can't guess what "equality" means for them. However, I think this could make sense for enums. An enum case, even with associated values, seems closer to a value itself than an object with logic and state.</div><div class="gmail_msg" style="font-size:13px"><br class="gmail_msg"></div><div class="gmail_msg" style="font-size:13px">I'd be interested to hear any thoughts on this. Would this be a beneficial addition?</div></div>
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