<html><head><meta http-equiv="Content-Type" content="text/html charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">I am currently working on updating some protocol APIs in a framework that's shared among several of my projects. The issue here is that the protocol has an extension with default implementation. For example:<div class=""><br class=""></div><blockquote style="margin: 0 0 0 40px; border: none; padding: 0px;" class=""><div class=""><div style="margin: 0px; font-size: 9px; line-height: normal; font-family: Menlo; color: rgb(186, 45, 162);" class=""><span style="font-variant-ligatures: no-common-ligatures" class="">protocol</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class=""> Foo {</span></div></div><div class=""><div style="margin: 0px; font-size: 9px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures;" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class="">func</span><span style="font-variant-ligatures: no-common-ligatures" class=""> doSomethingWithArray(</span><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class="">_</span><span style="font-variant-ligatures: no-common-ligatures" class=""> arr: [</span><span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">String</span><span style="font-variant-ligatures: no-common-ligatures" class="">])</span></div></div><div class=""><div style="margin: 0px; font-size: 9px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures" class="">}</span></div></div><div class=""><div style="margin: 0px; font-size: 9px; line-height: normal; font-family: Menlo; min-height: 10px;" class=""><br class=""></div></div><div class=""><div style="margin: 0px; font-size: 9px; line-height: normal; font-family: Menlo; color: rgb(186, 45, 162);" class=""><span style="font-variant-ligatures: no-common-ligatures" class="">extension</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">Foo</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class=""> {</span></div></div><div class=""><div style="margin: 0px; font-size: 9px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class=""> func</span><span style="font-variant-ligatures: no-common-ligatures" class=""> doSomethingWithArray(</span><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class="">_</span><span style="font-variant-ligatures: no-common-ligatures" class=""> arr: [</span><span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">String</span><span style="font-variant-ligatures: no-common-ligatures" class="">]) {</span></div></div><div class=""><div style="margin: 0px; font-size: 9px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #3e1e81" class=""> </span> <span style="font-variant-ligatures: no-common-ligatures; color: rgb(62, 30, 129);" class="">print</span><span style="font-variant-ligatures: no-common-ligatures;" class="">(arr)</span></div></div><div class=""><div style="margin: 0px; font-size: 9px; line-height: normal; font-family: Menlo;" class=""> }</div></div><div class=""><div style="margin: 0px; font-size: 9px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures" class="">}</span></div></div></blockquote><div class=""><div style="margin: 0px; font-size: 9px; line-height: normal; font-family: Menlo; min-height: 10px;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""></span></div></div><div style="margin: 0px; font-size: 9px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""><br class=""></span></div><div style="margin: 0px; font-size: 9px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""><span style="font-family: Helvetica; font-size: 10px;" class="">With this you can easily write </span></span></div><div style="margin: 0px; font-size: 9px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""><span style="font-family: Helvetica; font-size: 10px;" class=""><br class=""></span></span></div><blockquote style="margin: 0 0 0 40px; border: none; padding: 0px;" class=""><div style="margin: 0px; font-size: 9px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class="">struct</span> Bar: <span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">Foo</span> { }</span></div></blockquote><div style="margin: 0px; font-size: 9px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""><br class=""></span></div><div style="margin: 0px; font-size: 9px; line-height: normal; font-family: Menlo;" class=""><br class=""></div><div style="margin: 0px; line-height: normal;" class="">The issue comes when the struct actually implements the method and you decide to rename it in the protocol:</div><blockquote style="margin: 0 0 0 40px; border: none; padding: 0px;" class=""><div style="margin: 0px; line-height: normal;" class=""><br class=""></div><div style="margin: 0px; line-height: normal;" class=""><div style="margin: 0px; font-size: 9px; line-height: normal; font-family: Menlo;" class=""><div style="margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class="">struct</span><span style="font-variant-ligatures: no-common-ligatures" class=""> Bar: </span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">Foo</span><span style="font-variant-ligatures: no-common-ligatures" class=""> {</span></div></div></div><div style="margin: 0px; line-height: normal;" class=""><div style="margin: 0px; font-size: 9px; line-height: normal; font-family: Menlo;" class=""><div style="margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class=""> func</span><span style="font-variant-ligatures: no-common-ligatures" class=""> doSomethingWithArray(</span><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class="">_</span><span style="font-variant-ligatures: no-common-ligatures" class=""> arr: [</span><span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">String</span><span style="font-variant-ligatures: no-common-ligatures" class="">]) {</span></div></div></div><div style="margin: 0px; line-height: normal;" class=""><div style="margin: 0px; font-size: 9px; line-height: normal; font-family: Menlo;" class=""><div style="margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> fatalError()</span></div></div></div><div style="margin: 0px; line-height: normal;" class=""><div style="margin: 0px; font-size: 9px; line-height: normal; font-family: Menlo;" class=""><div style="margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> }</span></div></div></div><div style="margin: 0px; line-height: normal;" class=""><div style="margin: 0px; font-size: 9px; line-height: normal; font-family: Menlo;" class=""><div style="margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures" class="">}</span></div></div></div><div style="margin: 0px; line-height: normal;" class=""><div style="margin: 0px; font-size: 9px; line-height: normal; font-family: Menlo;" class=""><div style="margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""><br class=""></span></div></div></div><div style="margin: 0px; line-height: normal;" class=""><div style="margin: 0px; font-size: 9px; line-height: normal; font-family: Menlo;" class=""><div style="margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""><br class=""></span></div></div></div><div style="margin: 0px; line-height: normal;" class=""><div style="margin: 0px; font-size: 9px; line-height: normal; font-family: Menlo;" class=""><div style="margin: 0px; line-height: normal;" class=""><div style="margin: 0px; line-height: normal; color: rgb(186, 45, 162);" class=""><span style="font-variant-ligatures: no-common-ligatures" class="">protocol</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class=""> Foo {</span></div></div></div></div><div style="margin: 0px; line-height: normal;" class=""><div style="margin: 0px; font-size: 9px; line-height: normal; font-family: Menlo;" class=""><div style="margin: 0px; line-height: normal;" class=""><div style="margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures;" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class="">func</span><span style="font-variant-ligatures: no-common-ligatures" class=""> doSomething(with arr: [</span><span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">String</span><span style="font-variant-ligatures: no-common-ligatures" class="">])</span></div></div></div></div><div style="margin: 0px; line-height: normal;" class=""><div style="margin: 0px; font-size: 9px; line-height: normal; font-family: Menlo;" class=""><div style="margin: 0px; line-height: normal;" class=""><div style="margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures" class="">}</span></div></div></div></div><div style="margin: 0px; line-height: normal;" class=""><div style="margin: 0px; font-size: 9px; line-height: normal; font-family: Menlo;" class=""><div style="margin: 0px; line-height: normal;" class=""><div style="margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""><br class=""></span></div></div></div></div><div style="margin: 0px; line-height: normal;" class=""><div style="margin: 0px; font-size: 9px; line-height: normal; font-family: Menlo;" class=""><div style="margin: 0px; line-height: normal;" class=""><div style="margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""><div style="margin: 0px; line-height: normal; color: rgb(186, 45, 162);" class=""><span style="font-variant-ligatures: no-common-ligatures" class="">extension</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">Foo</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class=""> {</span></div></span></div></div></div></div><div style="margin: 0px; line-height: normal;" class=""><div style="margin: 0px; font-size: 9px; line-height: normal; font-family: Menlo;" class=""><div style="margin: 0px; line-height: normal;" class=""><div style="margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""><div style="margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class=""> func</span><span style="font-variant-ligatures: no-common-ligatures" class=""> doSomething(with arr: [</span><span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">String</span><span style="font-variant-ligatures: no-common-ligatures" class="">]) {</span></div></span></div></div></div></div><div style="margin: 0px; line-height: normal;" class=""><div style="margin: 0px; font-size: 9px; line-height: normal; font-family: Menlo;" class=""><div style="margin: 0px; line-height: normal;" class=""><div style="margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""><div style="margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #3e1e81" class=""> </span> <span style="font-variant-ligatures: no-common-ligatures; color: rgb(62, 30, 129);" class="">print</span><span style="font-variant-ligatures: no-common-ligatures;" class="">(arr)</span></div></span></div></div></div></div><div style="margin: 0px; line-height: normal;" class=""><div style="margin: 0px; font-size: 9px; line-height: normal; font-family: Menlo;" class=""><div style="margin: 0px; line-height: normal;" class=""><div style="margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""><div style="margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> }</span></div></span></div></div></div></div><div style="margin: 0px; line-height: normal;" class=""><div style="margin: 0px; font-size: 9px; line-height: normal; font-family: Menlo;" class=""><div style="margin: 0px; line-height: normal;" class=""><div style="margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""><div style="margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures" class="">}</span></div></span></div></div></div></div></blockquote><div style="margin: 0px; line-height: normal;" class=""><div style="margin: 0px; font-size: 9px; line-height: normal; font-family: Menlo;" class=""><div style="margin: 0px; line-height: normal;" class=""><div style="margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""><div style="margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""><br class=""></span></div><div style="margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""><span style="font-family: Helvetica; font-size: 10px;" class="">The code still compiles, yet the behavior of the app changes incredibly. There is no way (to my knowledge) of marking some protocol members as deprecated. I've tried the "obvious" solution:</span></span></div><div style="margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""><span style="font-family: Helvetica; font-size: 10px;" class=""><br class=""></span></span></div></span></div></div></div></div><blockquote style="margin: 0 0 0 40px; border: none; padding: 0px;" class=""><div style="margin: 0px; line-height: normal;" class=""><div style="margin: 0px; font-size: 9px; line-height: normal; font-family: Menlo;" class=""><div style="margin: 0px; line-height: normal;" class=""><div style="margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""><div style="margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""><div style="margin: 0px; line-height: normal;" class=""><div style="margin: 0px; line-height: normal; color: rgb(186, 45, 162);" class=""><span style="font-variant-ligatures: no-common-ligatures" class="">extension</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">Foo</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class=""> {</span></div><div style="margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures;" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: rgb(186, 45, 162);" class="">@available</span><span style="font-variant-ligatures: no-common-ligatures;" class="">(*, deprecated, renamed: </span><span style="font-variant-ligatures: no-common-ligatures; color: rgb(209, 47, 27);" class="">"doSomething(with:)"</span><span style="font-variant-ligatures: no-common-ligatures;" class="">)</span></div><div style="margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class=""> func</span><span style="font-variant-ligatures: no-common-ligatures" class=""> doSomethingWithArray(</span><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class="">_</span><span style="font-variant-ligatures: no-common-ligatures" class=""> arr: [</span><span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">String</span><span style="font-variant-ligatures: no-common-ligatures" class="">]) {</span></div><div style="margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class=""> </span> <span style="font-variant-ligatures: no-common-ligatures; color: rgb(186, 45, 162);" class="">self</span><span style="font-variant-ligatures: no-common-ligatures;" class="">.</span><span style="font-variant-ligatures: no-common-ligatures; color: rgb(49, 89, 93);" class="">doSomething</span><span style="font-variant-ligatures: no-common-ligatures;" class="">(with: arr)</span></div><div style="margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> }</span></div><div style="margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures" class="">}</span></div><div class=""><span style="font-variant-ligatures: no-common-ligatures" class=""><br class=""></span></div></div></span></div></span></div></div></div></div></blockquote>But unfortunately, this doesn't emit any warning on the Bar structure. I personally believe that this is a major flaw, given that Swift is being claimed as Protocol-Oriented language, there is no way to declare that a protocol method is deprecated/renamed. Mainly with protocols with default implementations (or in ObjC optional).<div class=""><br class=""></div><div class="">I know there were discussions about marking members that should implement the protocol requirements with a keyword, but unfortunately, most members here were against such a proposal as it would introduce a lot of visual clutter.</div><div class=""><br class=""></div><div class="">I'm suggesting that implementing a same-named member from a protocol marked as "deprecated" that also has a default implementation would emit a warning.</div><div class=""><br class=""></div><div class="">Does anyone else view this as an issue in the language?</div><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><br class=""></div></body></html>