<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="">-1<div class=""><br class=""></div><div class="">Not having the default case allows you to rely on the compiler to handle new options once they are added. Most of my apps consist nowadays from multiple modules and this would be massively inconvenient.</div><div class=""><br class=""></div><div class="">The possible future features may be non-breaking if we consider that we will not allow enums to be extended by default, but would need to be marked explicitely as extendable. Similar to public vs. open classes.</div><div class=""><br class=""><div><blockquote type="cite" class=""><div class="">On Feb 7, 2017, at 4:12 PM, Tanner Nelson 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 dir="ltr" class="">Hello Swift Evolution,<div class=""><br class=""></div><div class="">I'd like to propose that a warning be emitted when default cases are omitted for enums from other modules. </div><div class=""><br class=""></div><div class="">What this would look like:</div><div class=""><br class=""></div><div class="">OtherModule:</div><div class="">```</div><div class="">public enum SomeEnum {</div><div class=""> case one</div><div class=""> case two</div><div class="">}</div><div class=""><br class=""></div><div class="">public let global: SomeEnum = .one</div><div class="">```</div><div class=""><br class=""></div><div class="">executable:</div><div class="">```</div><div class="">import OtherModule</div><div class=""><br class=""></div><div class="">switch OtherModule.global {</div><div class=""> case .one: break</div><div class=""> case .two: break</div><div class=""> ^~~~~ ⚠︎ Warning: Default case recommended for imported enums. Fix-it: Add `default: break`</div><div class="">}</div><div class="">```</div><div class=""><br class=""></div><div class="">Why:</div><div class=""><br class=""></div><div class="">Allowing the omission of a default case in an exhaustive switch makes the addition of a new case to the enum a breaking change. </div><div class="">In other words, if you're exhaustively switching on an enum from an imported library, the imported library can break your code by adding a new case to that enum (which the library authors may erroneously view as an additive/minor-bump change).</div><div class=""><br class=""></div><div class="">Background:</div><div class=""><br class=""></div><div class="">As a maintainer of a Swift framework, public enums have been a pain point in maintaining semver. They've made it difficult to implement additive features and have necessitated the avoidance of enums in our future public API plans.</div><div class=""><br class=""></div><div class="">Related Twitter thread: <a href="https://twitter.com/tanner0101/status/796860273760104454" class="">https://twitter.com/tanner0101/status/796860273760104454</a></div><div class=""><br class=""></div><div class="">Looking forward to hearing your thoughts.</div><div class=""><br class=""></div><div class="">Best,</div><div class="">Tanner</div><div class=""><br class=""></div><div class=""><div style="font-family:'sf ui text';font-size:12px" class=""><font color="#5f5f5f" class="">Tanner Nelson</font></div><div style="font-family:'sf ui text';font-size:12px" class=""><font color="#9dacd1" class="">Va</font><font color="#aeb2cf" class="">p</font><font color="#c8bacd" class="">o</font><font color="#d0becc" class="">r</font><font color="#9dacd1" class=""> </font></div><div style="font-family:'sf ui text';font-size:12px" class=""><font color="#676767" class="">+1 (435) 773-2831</font></div></div><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><br class=""></div></div>
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