<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=""><div class="">Great job thinking this all through (as usual), and I’ll be very happy to have Optional and Array become Equatable. Here’s some of my thoughts on the library evolution aspect of this:</div><div class=""><br class=""></div><div class="">- Removing a conditional conformance isn’t allowed, obviously.</div><div class="">- Adding a conditional conformance is just like adding an unconditional conformance—it needs availability info.</div><div class="">- It would be nice™ if making a conditional conformance more general <i class="">was</i> allowed. Since the plan doesn't allow overlapping conformances, I think this is actually implementable: just don’t put the constraints in the symbol name. I don’t know how to represent the backwards-deploying aspects of this right now, so it probably makes sense to forbid it today, but I think it would be nice if the implementation left the door open.</div><div class=""><br class=""></div><div class="">On that note, what happens here?</div><div class=""><br class=""></div><blockquote style="margin: 0 0 0 40px; border: none; padding: 0px;" class=""><div class="">// Module Lib</div><div class="">public protocol Base {}</div><div class="">public protocol Sub: Base {}</div><div class="">public protocol Special: Sub {}</div><div class=""><br class=""></div><div class="">public struct Impl<T> {}</div><div class="">extension Impl: Special where T: Special {}</div><div class=""><br class=""></div><div class=""><br class=""></div><div class="">// Module Client</div><div class="">import Lib</div><div class=""><br class=""></div><div class="">extension Impl: Sub where T: Sub {}</div></blockquote><div class=""><br class=""></div>I think this gets rejected because Impl already has a conformance to Sub—the extension in Client, despite being less specialized, shows up too late to actually declare this conformance “better”. Is that correct?<div class=""><br class=""></div><div class="">Jordan<br class=""></div></body></html>