<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 24, 2016, at 12:39 AM, Russ Bishop <<a href="mailto:xenadu@gmail.com" class="">xenadu@gmail.com</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=""><div class=""><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=""><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=""><div class="">I added a separate section on Ambiguity and what the behavior is. I think you should be able to resolve ambiguity by casting so I went ahead and put that in. An example:</div><div class=""><br class=""></div><div class=""><div style="margin: 0px; font-size: 14px; line-height: normal; font-family: Menlo; color: rgb(75, 209, 87);" class=""><div style="margin: 0px; font-size: 11px; line-height: normal; color: rgb(0, 132, 0);" class=""><div style="margin: 0px; line-height: normal;" class="">//Bar and Foo bridge to SomeObjectiveCType</div><div style="margin: 0px; line-height: normal; color: rgb(79, 129, 135);" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">struct</span><span style="" class=""> Bar<T>: </span>ObjectiveCBridgeable<span style="" class=""> { }</span></div><div style="margin: 0px; line-height: normal; color: rgb(79, 129, 135);" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">struct</span><span style="" class=""> Foo<T>: </span>ObjectiveCBridgeable<span style="" class=""> { }</span></div><div style="margin: 0px; line-height: normal; min-height: 13px;" class=""><br class=""></div><div style="margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">class</span> API {</div><div style="margin: 0px; line-height: normal;" class=""> <span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">let</span> foo: <span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">Foo</span><<span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">Int</span>></div><div style="margin: 0px; line-height: normal;" class=""> <span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">func</span> objCVersionOfAFunction(obj: <span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">SomeObjectiveCType</span>) -> <span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">SomeObjectiveCType</span> {</div><div style="margin: 0px; line-height: normal;" class=""> <span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">let</span> x = obj <span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">as</span>! <span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">Bar</span><<span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">Int</span>></div><div style="margin: 0px; line-height: normal;" class=""><span style="" class=""> </span>// We've told the compiler which protocol impl to call</div><div style="margin: 0px; line-height: normal; color: rgb(79, 129, 135);" class=""><span style="" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">return</span><span style="" class=""> </span>foo<span style="" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">as</span><span style="" class="">! </span>SomeObjectiveCType</div><div style="margin: 0px; line-height: normal;" class=""> }</div><div style="margin: 0px; line-height: normal;" class="">}</div></div></div></div><div class=""><br class=""></div><div class="">Any problems with this approach? It makes handling the ambiguous or manual bridging case relatively straightforward, though there may be objections to using casting this way. [Be careful, I still mourn the loss of @conversion so I’m biased :)]</div></div></div></div></blockquote><div class=""><br class=""></div><div class=""><br class=""></div><div class="">The problem I have with allowing the ambiguity is that you can get weird behavior if Bar and Foo are in different modules: import just Bar’s module, and an Objective-C API mentioning SomeObjectiveCType gets bridged as a Bar. Import just Foo’s module, and an Objective-C API mentioning SomeObjectiveCType gets bridged as a Foo. Import both, and SomeObjectiveCType doesn’t get bridged! Now start splitting class hierarchies among those modules and you get some very inconsistent imports… that’s why I think this needs to be an error.</div><br class=""></div></div></div></blockquote><div class=""><br class=""></div><div class="">The rule requiring the Swift and @objc types to be in the same module wouldn’t allow the scenario you describe.</div></div></div></div></blockquote><div><br class=""></div><div>Ah, yes.</div><br class=""><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=""><div class=""><br class=""></div><div class="">I’m fine to say it’s an error as this isn’t a capability I have any use for and it definitely could cause confusion. The rule could always be relaxed in the future if there’s a convincing case for it. I’ll update the proposal to make it an error again.</div></div></div></div></blockquote><div><br class=""></div><div>I’d rather call it an error and consider relaxing the rule if we find it’s very important later on.</div><br class=""></div><div><span class="Apple-tab-span" style="white-space:pre"> </span>- Doug</div><div><br class=""></div><br class=""></body></html>