<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 Mar 16, 2016, at 5:27 PM, Alex Martini 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="">To help keep proposals moving forward, the Swift core team has set aside some time specifically for design discussions of upcoming proposals. Below are some rough notes from the yesterday's discussion.<br class=""><div class=""><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div class=""><div class=""><br class=""></div><div class="">These are <i class="">informal</i> comments, intended to guide the proposals in directions that draw constructive feedback. You are welcome to ignore the feedback, agree with it, or disagree with it. As always, the formal decision doesn't happen until after the review period ends.</div><div class=""><br class=""></div><div class=""><div class="section" id="se-0043" style="color: rgb(51, 51, 51); font-family: 'DejaVu Sans', Arial, Helvetica, sans-serif;"><div class=""><div class="section" id="se-0048"><h3 style="font-size: 1.1em; font-weight: normal; color: rgb(12, 55, 98); margin-top: 30px;" class="">SE-0048<a class="headerlink" href="file:///Users/alexmartini/DevPubs%20Git%20Repositories/Swift%20Language%20Review/_build/html/LR_MeetingNotes/MeetingNotes-03-15-2016.html#se-0048" title="Permalink to this headline" style="visibility: hidden; font-weight: bold; text-decoration: none; color: rgb(167, 206, 56); padding-left: 5px;"></a></h3><p style="text-align: justify;" class="">This is straightforward and 95% implemented. The contentious point is that it starts simple: you can’t add constraints to the type alias.</p><p style="text-align: justify;" class="">We want to avoid type-based metaprogramming.</p><p style="text-align: justify;" class="">Unclear if this would work:</p><div class="highlight-python"><pre style="overflow-x: auto; overflow-y: hidden; border: thin dotted rgb(12, 55, 98); margin-top: 0px; margin-bottom: 12px; padding: 0.8em; background-color: rgb(240, 240, 240);" class="">typealias StringDictionary<T> = Dictionary<String, T></pre></div><p style="text-align: justify;" class="">It need to infer that <tt class="literal docutils" style="background-color: rgb(226, 226, 226); font-size: 1em;"><span class="pre">T</span></tt> must be hashable. Maybe it’s only 85% implemented.</p><div class=""><br class=""></div></div></div></div></div></div></div></div></div></div></blockquote><br class=""></div><div>Clarification here: the example is</div><div><br class=""></div><blockquote style="margin: 0 0 0 40px; border: none; padding: 0px;" class=""><div><font face="Menlo" class="">typealias DictionaryToStrings<T> = Dictionary<T, String></font></div></blockquote><div><br class=""></div><div>Either we infer T to require Hashable, or we call this ill-formed and require the user to write</div><div><br class=""></div><div><blockquote style="margin: 0px 0px 0px 40px; border: none; padding: 0px;" class=""><div><font face="Menlo" class="">typealias DictionaryToStrings<T: Hashable> = Dictionary<T, String></font></div><div class=""><font face="Menlo" class=""><br class=""></font></div></blockquote></div><div><br class=""></div><div><br class=""></div><div><span class="Apple-tab-span" style="white-space:pre"> </span>- Doug</div><br class=""></body></html>