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<div name="messageBodySection" style="font-size: 14px; font-family: -apple-system, BlinkMacSystemFont, sans-serif;">Hi Swift community,
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<div>I was wondering if we have considered adding support for providing Xcode automatic fix-it’s for closures being returned from a function.</div>
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<div>For example, here is an incorrect version of a function that requires two `@escaping` keywords to be inserted.</div>
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<p style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;"><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2">func</span> <span style="font-variant-ligatures: no-common-ligatures">mapping <A, B, C> (f:</span> <span style="font-variant-ligatures: no-common-ligatures">(</span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187">A</span><span style="font-variant-ligatures: no-common-ligatures">) -> (</span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187">B</span><span style="font-variant-ligatures: no-common-ligatures">)) -></span> <span style="font-variant-ligatures: no-common-ligatures">((</span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187">C</span><span style="font-variant-ligatures: no-common-ligatures">,</span> <span style="font-variant-ligatures: no-common-ligatures; color: #4f8187">B</span><span style="font-variant-ligatures: no-common-ligatures">) -> (</span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187">C</span><span style="font-variant-ligatures: no-common-ligatures">)) -> ((</span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187">C</span><span style="font-variant-ligatures: no-common-ligatures">,</span> <span style="font-variant-ligatures: no-common-ligatures; color: #4f8187">A</span><span style="font-variant-ligatures: no-common-ligatures">) -> (</span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187">C</span><span style="font-variant-ligatures: no-common-ligatures">))</span></p>
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<div>Despite the complexity, the compiler manages to catch two errors.</div>
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<div>1. Closure use of non-escaping parameter `f` may allow it to escape</div>
<div> a. Automatic Fix-it by doing `f: @escaping (A) - > (B)`<br /></div>
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<div>2. Closure use of non-escaping parameter `reducer` may allow it to escape</div>
<div> b. No Fix-it provided <———— <br /></div>
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<div>As you see above, the two places where a compile-time error occurred had the same exact problem; they both needed a `@escaping`. However, while the function parameter was offered an automatic fix-it, the nested closure being returned was not.</div>
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<div>Here’s the correct version of the function.</div>
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<p style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;"><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2">func</span> <span style="font-variant-ligatures: no-common-ligatures">mapping <A, B, C> (f:</span> <span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2">@escaping</span> <span style="font-variant-ligatures: no-common-ligatures">(</span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187">A</span><span style="font-variant-ligatures: no-common-ligatures">) -> (</span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187">B</span><span style="font-variant-ligatures: no-common-ligatures">)) -> (</span><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2">@escaping</span> <span style="font-variant-ligatures: no-common-ligatures">((</span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187">C</span><span style="font-variant-ligatures: no-common-ligatures">,</span> <span style="font-variant-ligatures: no-common-ligatures; color: #4f8187">B</span><span style="font-variant-ligatures: no-common-ligatures">) -> (</span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187">C</span><span style="font-variant-ligatures: no-common-ligatures">))) -> ((</span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187">C</span><span style="font-variant-ligatures: no-common-ligatures">,</span> <span style="font-variant-ligatures: no-common-ligatures; color: #4f8187">A</span><span style="font-variant-ligatures: no-common-ligatures">) -> (</span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187">C</span><span style="font-variant-ligatures: no-common-ligatures">)) {</span></p>
<p style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;"><span style="font-variant-ligatures: no-common-ligatures">   </span> <span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2">return</span> <span style="font-variant-ligatures: no-common-ligatures">{ reducer</span> <span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2">in</span></p>
<p style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;"><span style="font-variant-ligatures: no-common-ligatures">       </span> <span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2">return</span> <span style="font-variant-ligatures: no-common-ligatures">{ accum, input</span> <span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2">in</span></p>
<p style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;"><span style="font-variant-ligatures: no-common-ligatures">            reducer(accum, f(input))</span></p>
<p style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;"><span style="font-variant-ligatures: no-common-ligatures">        }</span></p>
<p style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;"><span style="font-variant-ligatures: no-common-ligatures">    }</span></p>
<p style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;"></p>
<p style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;"><span style="font-variant-ligatures: no-common-ligatures">}</span></p>
<p style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;"><span style="font-variant-ligatures: no-common-ligatures"><br /></span></p>
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<div>I know this is a small feature for a very specific use case but I think it could help make Xcode a little smarter :D </div>
<div>Thanks for reading!</div>
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