<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 7, 2016, at 1:44 AM, Dennis Weissmann via swift-users <<a href="mailto:swift-users@swift.org" class="">swift-users@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="">Hi Neil,<div class=""><br class=""></div><div class="">indeed the compiler should be able to infer the type here.</div><div class=""><br class=""></div><div class="">The error message in the latest development snapshot (swift-DEVELOPMENT-SNAPSHOT-2016-03-01-a) is a little better:</div></div></div></blockquote><div><br class=""></div><div>Yep, further improvements are tracked by:</div><div><div><<a href="rdar://problem/24209966" class="">rdar://problem/24209966</a>> QoI: When a non-single-expression closure type can't be inferred, say that we didn't look at the body</div><div><div><<a href="rdar://problem/22123191" class="">rdar://problem/22123191</a>> QoI: multi-line closure with failure to infer result type should add a fixit</div><div class=""><br class=""></div></div><div>-Chris</div></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=""><br class=""></div><div class=""><blockquote type="cite" class="">Expression type '[_]' is ambiguous without more context</blockquote></div><div class=""><br class=""></div><div class="">You can work around like this:</div><div class=""><br class=""></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">let</span><span style="font-variant-ligatures: no-common-ligatures" class=""> x2 = [</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: #3d1d81" class="">map</span><span style="font-variant-ligatures: no-common-ligatures" class=""> { </span><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">_</span><span style="font-variant-ligatures: no-common-ligatures" class=""> -> </span><span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">String</span><span style="font-variant-ligatures: no-common-ligatures" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">in</span></div><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: #bb2ca2" class="">let</span><span style="font-variant-ligatures: no-common-ligatures" class=""> x = </span><span style="font-variant-ligatures: no-common-ligatures; color: #d12f1b" class="">"abc"</span></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; color: rgb(187, 44, 162);" class=""><span style="" class=""> </span><span style="font-variant-ligatures: no-common-ligatures" class="">return</span><span style="" class=""> x</span></div><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 class=""><br class=""></div><div class="">or</div><div class=""><br class=""></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">let</span><span style="font-variant-ligatures: no-common-ligatures" class=""> x2: [</span><span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">String]</span><span style="font-variant-ligatures: no-common-ligatures" class=""> = [</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: #3d1d81" class="">map</span><span style="font-variant-ligatures: no-common-ligatures" class=""> { </span><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">_</span><span style="font-variant-ligatures: no-common-ligatures" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">in</span></div><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: #bb2ca2" class="">let</span><span style="font-variant-ligatures: no-common-ligatures" class=""> x = </span><span style="font-variant-ligatures: no-common-ligatures; color: #d12f1b" class="">"abc"</span></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; color: rgb(187, 44, 162);" class=""><span style="" class=""> </span><span style="font-variant-ligatures: no-common-ligatures" class="">return</span><span style="" class=""> x</span></div><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 class=""><br class=""></div><div class="">- Dennis</div><div class=""><br class=""></div><div class=""><div class=""><blockquote type="cite" class=""><div class="">On Mar 7, 2016, at 12:55 AM, Neil Faiman via swift-users <<a href="mailto:swift-users@swift.org" class="">swift-users@swift.org</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div class="">Using the version of Swift in Xcode 7.2.1, I compile the following program:<br class=""><br class=""> let x1 = [1,2].map { _ in<br class=""> return "abc"<br class=""> }<br class=""><br class=""> let x2 = [1,2].map { _ in<br class=""> let x = "abc"<br class=""> return x<br class=""> }<br class=""><br class="">The assignment to x1 compiles successfully, but the assignment to x2 produces this error:<br class=""><br class=""> Cannot invoke 'map' with an argument list of type '(@noescape (Int) throws -> _)'<br class=""> Expected an argument list of type '(@noescape (Self.Generator.Element) throws -> T)'<br class=""><br class="">It seems that in both calls, the transform closure is returning a String, so I don’t see why the compiler can infer the return type in one case, but not in the other. Am I missing something obvious?<br class=""><br class="">Thanks,<br class=""><br class=""><span class="Apple-tab-span" style="white-space:pre"> </span>Neil Faiman<br class="">_______________________________________________<br class="">swift-users mailing list<br class=""><a href="mailto:swift-users@swift.org" class="">swift-users@swift.org</a><br class=""><a href="https://lists.swift.org/mailman/listinfo/swift-users" class="">https://lists.swift.org/mailman/listinfo/swift-users</a><br class=""></div></div></blockquote></div><br class=""></div></div>_______________________________________________<br class="">swift-users mailing list<br class=""><a href="mailto:swift-users@swift.org" class="">swift-users@swift.org</a><br class="">https://lists.swift.org/mailman/listinfo/swift-users<br class=""></div></blockquote></div><br class=""></body></html>