<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=""><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="">Does inference still work correctly when trailing closure syntax is used, if the arguments are not given types?<div class=""><br class=""></div><div class="">For example, here’s some code that works in Swift right now:</div><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: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class="">let</span><span style="font-variant-ligatures: no-common-ligatures" class=""> a = [</span><span style="font-variant-ligatures: no-common-ligatures; color: #272ad8" class="">1</span><span style="font-variant-ligatures: no-common-ligatures" class="">, </span><span style="font-variant-ligatures: no-common-ligatures; color: #272ad8" class="">2</span><span style="font-variant-ligatures: no-common-ligatures" class="">, </span><span style="font-variant-ligatures: no-common-ligatures; color: #272ad8" class="">3</span><span style="font-variant-ligatures: no-common-ligatures" class="">, </span><span style="font-variant-ligatures: no-common-ligatures; color: #272ad8" class="">4</span><span style="font-variant-ligatures: no-common-ligatures" class="">, </span><span style="font-variant-ligatures: no-common-ligatures; color: #272ad8" class="">5</span><span style="font-variant-ligatures: no-common-ligatures" class="">]</span></div></div><div class=""><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class="">let</span><span style="font-variant-ligatures: no-common-ligatures" class=""> b = </span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">a</span><span style="font-variant-ligatures: no-common-ligatures" class="">.</span><span style="font-variant-ligatures: no-common-ligatures; color: #3e1e81" class="">reduce</span><span style="font-variant-ligatures: no-common-ligatures" class="">([]) { (result, element) </span><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class="">in</span></div></div><div class=""><div style="margin: 0px; font-size: 11px; 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="">return</span><span style="font-variant-ligatures: no-common-ligatures" class=""> result </span><span style="font-variant-ligatures: no-common-ligatures; color: #3e1e81" class="">+</span><span style="font-variant-ligatures: no-common-ligatures" class=""> [element * </span><span style="font-variant-ligatures: no-common-ligatures; color: #272ad8" class="">2</span><span style="font-variant-ligatures: no-common-ligatures" class="">]</span></div></div><div class=""><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures" class="">}</span></div></div></blockquote><div class=""><span style="font-variant-ligatures: no-common-ligatures" class=""><br class=""></span></div><div class="">Under the new proposal, this code would also be valid:</div><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: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class="">let</span><span style="font-variant-ligatures: no-common-ligatures" class=""> a = [</span><span style="font-variant-ligatures: no-common-ligatures; color: #272ad8" class="">1</span><span style="font-variant-ligatures: no-common-ligatures" class="">, </span><span style="font-variant-ligatures: no-common-ligatures; color: #272ad8" class="">2</span><span style="font-variant-ligatures: no-common-ligatures" class="">, </span><span style="font-variant-ligatures: no-common-ligatures; color: #272ad8" class="">3</span><span style="font-variant-ligatures: no-common-ligatures" class="">, </span><span style="font-variant-ligatures: no-common-ligatures; color: #272ad8" class="">4</span><span style="font-variant-ligatures: no-common-ligatures" class="">, </span><span style="font-variant-ligatures: no-common-ligatures; color: #272ad8" class="">5</span><span style="font-variant-ligatures: no-common-ligatures" class="">]</span></div></div><div class=""><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; min-height: 13px;" class=""><br class=""></div></div><div class=""><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class="">let</span><span style="font-variant-ligatures: no-common-ligatures" class=""> b = </span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">a</span><span style="font-variant-ligatures: no-common-ligatures" class="">.</span><span style="font-variant-ligatures: no-common-ligatures; color: #3e1e81" class="">reduce</span><span style="font-variant-ligatures: no-common-ligatures" class="">([]) { (result, element) </span><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class="">in</span></div></div><div class=""><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> result.append(element * </span><span style="font-variant-ligatures: no-common-ligatures; color: #272ad8" class="">2</span><span style="font-variant-ligatures: no-common-ligatures" class="">)</span></div></div><div class=""><div style="margin: 0px; font-size: 11px; 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: 11px; line-height: normal; font-family: Menlo; min-height: 13px;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""></span></div></div><div class="">Note that these both of these closures appear to have the same signature: two parameters of inferred type, and an inferred return type. The “inout” and return types differ, but neither are specified here. Will the compiler be able to correctly infer the types based on the presence or absence of a “return” statement in the closure body? If not, it seems like the first example will become ambiguous.</div><div class=""><br class=""></div><div class="">-BJ</div><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><div class=""><blockquote type="cite" class=""><div class="">On Apr 14, 2017, at 12:37 PM, Ben Cohen 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=""><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="">Hello Swift community,<br class=""><br class="">The review of “SE-0171: Reduce with inout" begins now and runs through the Friday after next, April 14th. The proposal is available here:<div class=""><span class="Apple-tab-span" style="white-space: pre;"> </span><a href="https://github.com/apple/swift-evolution/blob/master/proposals/0155-normalize-enum-case-representation.md" class="">https://github.com/apple/swift-evolution/blob/master/proposals/0171-reduce-with-inout.md</a></div><div class=""><br class=""></div><div class=""><div class="">Reviews are an important part of the Swift evolution process. All reviews should be sent to the swift-evolution mailing list at</div><div class=""><span class="Apple-tab-span" style="white-space: pre;"> </span><a href="https://lists.swift.org/mailman/listinfo/swift-evolution" class="">https://lists.swift.org/mailman/listinfo/swift-evolution</a></div><div class="">or, if you would like to keep your feedback private, directly to the review manager. When replying, please try to keep the proposal link at the top of the message:</div><div class=""><br class=""><span class="Apple-tab-span" style="white-space: pre;"> </span>Proposal link: <a href="https://github.com/apple/swift-evolution/blob/master/proposals/0155-normalize-enum-case-representation.md" class="">https://github.com/apple/swift-evolution/blob/master/proposals/0171-reduce-with-inout.md</a></div><div class=""><br class=""></div><div class=""><span class="Apple-tab-span" style="white-space: pre;"> </span>Reply text</div><div class=""><br class=""><span class="Apple-tab-span" style="white-space: pre;"> </span>Other replies</div><div class=""><br class=""></div><div class=""><b class="">What goes into a review?</b><br class=""><br class="">The goal of the review process is to improve the proposal under review through constructive criticism and, eventually, determine the direction of Swift. When writing your review, here are some questions you might want to answer in your review:<br class=""><br class=""><div class=""><span class="Apple-tab-span" style="white-space: pre;"> </span>• What is your evaluation of the proposal?<br class=""></div><div class=""><span class="Apple-tab-span" style="white-space: pre;"> </span>• Is the problem being addressed significant enough to warrant a change to Swift?<br class=""></div><div class=""><span class="Apple-tab-span" style="white-space: pre;"> </span>• Does this proposal fit well with the feel and direction of Swift?<br class=""></div><div class=""><span class="Apple-tab-span" style="white-space: pre;"> </span>• If you have used other languages or libraries with a similar feature, how do you feel that this proposal compares to those?<br class=""></div><div class=""><span class="Apple-tab-span" style="white-space: pre;"> </span>• How much effort did you put into your review? A glance, a quick reading, or an in-depth study?<br class=""></div><div class=""><br class=""></div>More information about the Swift evolution process is available at <a href="https://github.com/apple/swift-evolution/blob/master/process.md" class="">https://github.com/apple/swift-evolution/blob/master/process.md</a><div class=""><br class=""><div class="">Thank you,</div><div class=""><br class=""></div><div class="">Ben Cohen</div><div class="">Review Manager</div><div class=""><br class=""></div><div class=""><br class=""></div></div></div></div></div>_______________________________________________<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></blockquote></div><br class=""></div></div></body></html>