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Thanks for you help!
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<div class="">在 2016年6月30日，上午11:58，Neil Faiman <<a href="mailto:neil.swift@faiman.org" class="">neil.swift@faiman.org</a>> 写道：</div>
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<div class="">On Jun 29, 2016, at 11:03 PM, boris via swift-users <<a href="mailto:swift-users@swift.org" class="">swift-users@swift.org</a>> wrote:</div>
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<font face="Menlo" class="">//Report Error: Ambiguous reference to member ‘map’ </font></div>
<div class=""><font face="Menlo" class="">// </font></div>
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<font face="Menlo" class=""><span style="font-variant-ligatures: no-common-ligatures" class="">numbers</span><span style="font-variant-ligatures: no-common-ligatures;" class="">.map({</span></font></div>
<div style="margin: 0px; font-size: 14px; line-height: normal;" class=""><font face="Menlo" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> (number:
</span><span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">Int</span><span style="font-variant-ligatures: no-common-ligatures" class="">)
</span><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class="">in</span></font></div>
<div style="margin: 0px; font-size: 14px; line-height: normal;" class=""><font face="Menlo" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> v</span><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class="">ar</span><span style="font-variant-ligatures: no-common-ligatures" class="">
ret = </span><span style="font-variant-ligatures: no-common-ligatures; color: #272ad8" class="">3</span><span style="font-variant-ligatures: no-common-ligatures" class=""> * number</span></font></div>
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</span><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class="">return</span><span style="font-variant-ligatures: no-common-ligatures" class=""> ret</span></font></div>
<div style="margin: 0px; font-size: 14px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""><font face="Menlo" class="">})</font></span></div>
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<div class="">I asked the same question a few months ago; the answer was that it is a deliberate design choice that you can only omit the return type from a single-expression closure (and that the error message is less than helpful). For example, Jordan Rose
offered this explanation:</div>
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<div class="">Swift very deliberately does <i class="">not</i> infer types across multiple statements in closure bodies. This is mostly an implementation restriction (our type-checking system can't handle it very well), but it's also a simple rule that <i class="">explains</i> the
implementation restriction, rather than having type inference in closure bodies working some of the time but not all.</div>
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<div class="">As Chris pointed out, the compiler could definitely do a better job communicating the problem, but actually <i class="">changing the behavior</i> here would require significant implementation work. So this is not considered a "bug", just an implementation-driven
design choice.</div>
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Regards,
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<div class=""><span class="Apple-tab-span" style="white-space:pre"></span>Neil Faiman</div>
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