<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=""><blockquote type="cite" class="">On Jan 20, 2016, at 11:56 PM, Slava Pestov <<a href="mailto:spestov@apple.com" class="">spestov@apple.com</a>> wrote:<br class=""></blockquote><div><blockquote type="cite" class=""><br class="Apple-interchange-newline"><div class=""><div class="" style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;"><div class=""><blockquote type="cite" class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;"><div class=""><div class="" style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;"><div class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;">Okay, in the example above, that leaves five places for the generic signature to go: after the “if”, after the “let”, after the variable name, after the equals sign, and after the “as?”. Or perhaps we could introduce some sort of new keyword in there to which to attach the generic signature.</div></div></div></blockquote><div style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><br class=""></div><span style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;" class="">Various approaches have been discussed before. The one that’s closest to what you describe above is to have some kind of ‘open’ keyword,</span></div><div class=""><br class=""></div><div class="">func foo(p: SomeProto) {</div><div class=""> let t = open p as T {</div><div class=""> T.SomeAssocType.someStaticMethod(…)</div><div class=""> }</div><div class="">}</div></div></div></blockquote><div><br class=""></div><div>Thanks, this looks good. Based on this, I found the earlier discussion where this came up, but it seems that the example above assumes you already know p is SomeProto. I assume there’d be a way to take p as something else, like an Any, and dynamically cast it to SomeProto using some combination of as? and open, right?</div><br class=""><blockquote type="cite" class=""><div class=""><div class="" style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;"><div class=""><blockquote type="cite" class=""><div class=""><div class="" style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;"><div class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;"><div class=""><blockquote type="cite" class=""><blockquote type="cite" class=""><div class=""><div class="">Is this a feasible thing to ask for?<br class=""></div></div></blockquote><div class=""><br class=""></div>I think so, but we have to careful with the design. This ties in with some of the discussions on generalizing existential types, also.</blockquote></div></div><div class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;"><br class=""></div><div class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;">That’s good to hear. Is there any information on what the Swift team is planning to do with existentials?</div></div></div></blockquote><div class=""><br class=""></div>Oh, I was just referring to the discussion on this list. No concrete proposals have been accepted so far, AFAIK.</div></div></div></blockquote></div><div class=""><br class=""></div><div class="">Well, if someone proposes one, it’ll get a +1 from me.</div><div class=""><br class=""></div>Thanks,<br class=""><div class="">Charles</div><div class=""><br class=""></div></body></html>