<div>Left unsaid from my reply about enums is that implicit conversions should absolutely be added. We already have this magic for one particular enum, Optional.</div><div><br></div><div>I'm not arguing with you that enums are currently unsuitable. In fact I entirely agree. But Chris Lattner and others have said (now I'm paraphrasing, but I believe accurately) that they *should* be. What will it take? At minimum, some way to opt into implicit conversions. It's a no-brainer in my mind.</div><div><br></div><div>Bottom line: the language needs one excellent way to model Foo | Bar | Baz, not two or three mediocre workarounds. The core team has said that they want that excellence to be built through enums. Let's do it.</div><div><br></div><div><br></div><div><div class="gmail_quote"><div>On Sun, Feb 19, 2017 at 21:28 Zach Waldowski via swift-evolution <<a href="mailto:swift-evolution@swift.org">swift-evolution@swift.org</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div class="gmail_msg"><div style="font-family:Arial" class="gmail_msg">On Sun, Feb 19, 2017, at 06:40 PM, Xiaodi Wu via swift-evolution wrote:<br class="gmail_msg"></div>
</div><div class="gmail_msg"><blockquote type="cite" class="gmail_msg"><div class="gmail_msg"><div class="gmail_msg"><div class="gmail_msg"><div style="font-family:Arial" class="gmail_msg">On Sun, Feb 19, 2017 at 5:15 PM, Brent Royal-Gordon via swift-evolution <span class="gmail_msg"><<a href="mailto:swift-evolution@swift.org" class="gmail_msg" target="_blank">swift-evolution@swift.org</a>></span> wrote:<br class="gmail_msg"></div>
<blockquote style="margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0.8ex;border-left-width:1px;border-left-style:solid;border-left-color:rgb(204,204,204);padding-left:1ex" class="gmail_msg"><div style="font-family:Arial" class="gmail_msg">What is the harm of permitting an outside conformance to `SQLiteValue`?<br class="gmail_msg"></div>
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<div style="font-family:Arial" class="gmail_msg">I'll put words in Brent's mouth here as an attempt at an answer: you sometimes need to exclusively switch a downcast of an existential. Consider a serialization type - or SQLiteValue - where need to treat specific fundamental types ("primitives") in implementation-dependent ways. In a theoretical serialization design, all non-primitives would have an explicit protocol of semantics to conform to support serialization, much like the stdlib's "Custom" protocol pattern, and you compose from there.<br class="gmail_msg"></div>
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<div style="font-family:Arial" class="gmail_msg">Using an enum to represent this exclusivity remains unconvincing to me, unless we choose to add implicit conversions to the language. `.int(42)` is an overwhelming level of duplicate type information in any practical, non-trivial use case. Yes, (closed) enums model exclusivity. They are not the only things to do so.<br class="gmail_msg"></div>
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<div style="font-family:Arial" class="gmail_msg">The stdlib alone is reason enough for this feature to exist, even if not exposed publicly.<br class="gmail_msg"></div>
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<div style="font-family:Arial" class="gmail_msg">Zachary</div>
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