<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=""><br class=""><div><blockquote type="cite" class=""><div class="">On Jan 15, 2016, at 11:56 PM, Nate Cook <<a href="mailto:natecook@gmail.com" class="">natecook@gmail.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><meta http-equiv="Content-Type" content="text/html charset=us-ascii" class=""><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">There's a fairly subtle difference between `case Foo` and `case let Foo` when using a switch inside an enumeration. The first matches the Foo case of the current enumeration, the second binds a local `Foo` (that shadows .Foo) to any case. See the `testLet` property in this example:<div class=""><br class=""></div><div class=""><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><div style="margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">enum</span> Test {</div><div style="margin: 0px; line-height: normal;" class=""> <span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">case</span> One, Two</div><div style="margin: 0px; line-height: normal; min-height: 13px;" class=""> <br class="webkit-block-placeholder"></div><div style="margin: 0px; line-height: normal;" class=""> <span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">var</span> testDot: <span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">String</span> {</div><div style="margin: 0px; line-height: normal;" class=""> <span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">switch</span> <span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">self</span> {</div><div style="margin: 0px; line-height: normal;" class=""> <span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">case</span> .One: <span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">return</span> <span style="font-variant-ligatures: no-common-ligatures; color: #d12f1b" class="">"One"</span></div><div style="margin: 0px; line-height: normal;" class=""> <span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">case</span> .Two: <span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">return</span> <span style="font-variant-ligatures: no-common-ligatures; color: #d12f1b" class="">"Two"</span></div><div style="margin: 0px; line-height: normal;" class=""> }</div><div style="margin: 0px; line-height: normal;" class=""> }</div><div style="margin: 0px; line-height: normal; min-height: 13px;" class=""> <br class="webkit-block-placeholder"></div><div style="margin: 0px; line-height: normal;" class=""> <span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">var</span> testLetDot: <span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">String</span> {</div><div style="margin: 0px; line-height: normal;" class=""> <span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">switch</span> <span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">self</span> {</div><div style="margin: 0px; line-height: normal;" class=""> <span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">case</span> <span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">let</span> .One: <span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">return</span> <span style="font-variant-ligatures: no-common-ligatures; color: #d12f1b" class="">"One"</span></div><div style="margin: 0px; line-height: normal;" class=""> <span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">case</span> <span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">let</span> .Two: <span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">return</span> <span style="font-variant-ligatures: no-common-ligatures; color: #d12f1b" class="">"Two"</span></div><div style="margin: 0px; line-height: normal;" class=""> }</div><div style="margin: 0px; line-height: normal;" class=""> }</div><div style="margin: 0px; line-height: normal; min-height: 13px;" class=""> <br class="webkit-block-placeholder"></div><div style="margin: 0px; line-height: normal;" class=""> <span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">var</span> testLet: <span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">String</span> {</div><div style="margin: 0px; line-height: normal;" class=""> <span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">switch</span> <span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">self</span> {</div><div style="margin: 0px; line-height: normal; color: rgb(0, 132, 0);" class=""><span style="" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">case</span><span style="" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">let</span><span style="" class=""> One: </span><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">return</span><span style="" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: #d12f1b" class="">"One" </span><span style="" class=""> </span>// Danger Will Robinson</div><div style="margin: 0px; line-height: normal;" class=""> <span style="color: rgb(187, 44, 162);" class="">case</span> <span style="color: rgb(187, 44, 162);" class="">let</span> Two: <span style="color: rgb(187, 44, 162);" class="">return</span> <span style="color: rgb(209, 47, 27);" class="">"Two"</span></div><div style="margin: 0px; line-height: normal;" class=""> }</div><div style="margin: 0px; line-height: normal;" class=""> }</div><div style="margin: 0px; line-height: normal; min-height: 13px;" class=""> <br class="webkit-block-placeholder"></div><div style="margin: 0px; line-height: normal;" class=""> <span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">var</span> testNone: <span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">String</span> {</div><div style="margin: 0px; line-height: normal;" class=""> <span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">switch</span> <span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">self</span> {</div><div style="margin: 0px; line-height: normal;" class=""> <span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">case</span> One: <span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">return</span> <span style="font-variant-ligatures: no-common-ligatures; color: #d12f1b" class="">"One"</span></div><div style="margin: 0px; line-height: normal;" class=""> <span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">case</span> Two: <span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">return</span> <span style="font-variant-ligatures: no-common-ligatures; color: #d12f1b" class="">"Two"</span></div><div style="margin: 0px; line-height: normal;" class=""> }</div><div style="margin: 0px; line-height: normal;" class=""> }</div><div style="margin: 0px; line-height: normal;" class="">}</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="">let</span> two = <span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">Test</span>.<span style="font-variant-ligatures: no-common-ligatures; color: #31595d" class="">Two</span></div><div style="margin: 0px; line-height: normal; color: rgb(79, 129, 135);" class="">two<span style="" class="">.</span>testDot<span style="" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: #008400" class="">// Two</span></div><div style="margin: 0px; line-height: normal; color: rgb(79, 129, 135);" class="">two<span style="" class="">.</span>testLetDot<span style="" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: #008400" class="">// Two</span></div><div style="margin: 0px; line-height: normal; color: rgb(79, 129, 135);" class="">two<span style="" class="">.</span>testLet<span style="" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: #008400" class="">// One</span></div><div style="margin: 0px; line-height: normal; color: rgb(79, 129, 135);" class="">two<span style="" class="">.</span>testNone<span style="" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: #008400" class="">// Two</span></div></div></div></div></div></blockquote><div><br class=""></div><div>Definitely, Rob Rix has run into this problem in the wild too. I think that's a general ergonomic problem with our pattern syntax, though; 'let' on every pattern variable is verbose, and it's tempting when doing heavy pattern matching to reflexively type 'case let' at the start of every match to avoid it.</div><div><br class=""></div><div>-Joe</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=""><blockquote type="cite" class=""><div class="">On Jan 15, 2016, at 6:42 PM, Joe Groff 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=""><div class=""><br class=""><blockquote type="cite" class="">On Jan 15, 2016, at 2:44 PM, Jens Persson via swift-evolution <<a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a>> wrote:<br class=""><br class="">enum SomeEnum {<br class=""> case Foo<br class=""> case Bar<br class=""> func demoDotAndNoDot() {<br class=""> switch self {<br class=""> case .Foo: print("This has the usual dot before the case name.")<br class=""> case Bar: print("This has no dot, which is ok, at least in this particular context.")<br class=""> }<br class=""> }<br class="">}<br class=""><br class="">I'm just throwing this out in case someone should feel like writing a formal proposal to remove the dotless form.<br class=""><br class="">I'd be ok with removing it since it only works in some specific contexts. <br class=""></blockquote><br class="">This works by normal instance member lookup. Why do you think it should be removed?<br class=""><br class="">-Joe<br class=""><br class="">_______________________________________________<br class="">swift-evolution mailing list<br class=""><a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a><br class=""><a href="https://lists.swift.org/mailman/listinfo/swift-evolution" class="">https://lists.swift.org/mailman/listinfo/swift-evolution</a><br class=""></div></div></blockquote></div><br class=""></div></div></div></blockquote></div><br class=""></body></html>