<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 Aug 23, 2016, at 3:44 PM, Zach Waldowski 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="">
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<div class=""><div style="font-family:Arial;" class="">Early feedback is +1, you folks sure know how to write proposals on Foundation. ;-)<br class=""></div>
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<div style="font-family:Arial;" class="">I filed radar <<a href="rdar://problem/20807093" class="">rdar://problem/20807093</a>> related to this a while ago. Is there any chance the struct conformances could be applied using the objc_boxable attribute added to Clang last year? Apple's definition of what they consider to be simple, fixed structs should ideally live in one place (apinotes would do as well).</div></div></div></blockquote><div><br class=""></div><div>I’d forgotten about objc_boxable. It might be possible to synthesize an _ObjectiveCBridgeable conformance for objc_boxable types, using the @encode string to match whether a particular NSValue can be bridged to that type.</div><div><br class=""></div><span class="Apple-tab-span" style="white-space:pre"> </span>- Doug</div><div><br class=""><blockquote type="cite" class=""><div class=""><div class="">
<div id="sig40804545" class=""><div class="signature"><span class="font" style="font-family:arial, sans-serif, sans-serif">Sincerely,</span><span class="font" style="font-family:arial, sans-serif, sans-serif"></span><br class=""></div>
<div class="signature"><span class="font" style="font-family:arial, sans-serif, sans-serif"> Zachary Waldowski</span><span class="font" style="font-family:arial, sans-serif, sans-serif"></span><br class=""></div>
<div class="signature"><span class="font" style="font-family:arial, sans-serif, sans-serif"> </span><a href="mailto:zach@waldowski.me" class=""><span class="font" style="font-family:arial, sans-serif, sans-serif">zach@waldowski.me</span></a><br class=""></div>
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<div class="">On Tue, Aug 23, 2016, at 03:36 PM, Douglas Gregor via swift-evolution wrote:<br class=""></div>
<blockquote type="cite" class=""><h2 style="margin-top:24px;margin-bottom:16px;line-height:1.25;padding-bottom:0.3em;border-bottom-width:1px;border-bottom-style:solid;border-bottom-color:rgb(238, 238, 238);color:rgb(51, 51, 51);font-family:-apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol';background-color:rgb(255, 255, 255);" class="">Introduction<br class=""></h2><p style="margin-top: 0px; margin-bottom: 16px;" class=""><span class="highlight" style="background-color:rgb(255, 255, 255)"><span class="colour" style="color:rgb(51, 51, 51)"><span class="font" style="font-family:-apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'"><span class="size" style="font-size:16px">A handful of Swift numeric types are bridged to <code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">NSNumber</code> when passed into Objective-C object contexts. We should extend this bridging behavior to all Swift numeric types. We should also bridge common Cocoa structs such as <code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">NSRange</code>by boxing them into <code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">NSValue</code> objects.</span></span></span></span><br class=""></p><p style="margin-top: 0px; margin-bottom: 16px;" class=""><span class="highlight" style="background-color:rgb(255, 255, 255)"><span class="colour" style="color:rgb(51, 51, 51)"><span class="font" style="font-family:-apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'"><span class="size" style="font-size:16px">Swift-evolution thread: <a style="background-color:transparent;-webkit-text-decoration-skip:objects;color:rgb(64, 120, 192);text-decoration:none;" href="https://lists.swift.org/pipermail/swift-evolution/" class="">TBD</a></span></span></span></span><br class=""></p><h2 style="margin-top:24px;margin-bottom:16px;line-height:1.25;padding-bottom:0.3em;border-bottom-width:1px;border-bottom-style:solid;border-bottom-color:rgb(238, 238, 238);color:rgb(51, 51, 51);font-family:-apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol';background-color:rgb(255, 255, 255);" class=""><a style="background-color:transparent;-webkit-text-decoration-skip:objects;color:rgb(64, 120, 192);text-decoration:none;float:left;padding-right:4px;line-height:1;" href="https://github.com/jckarter/swift-evolution/blob/be49e08f56450ffea394306198bcd25f58915e30/proposals/XXXX-bridge-nsnumber-and-nsvalue.md#motivation" class=""></a>Motivation<br class=""></h2><p style="margin-top: 0px; margin-bottom: 16px;" class=""><span class="highlight" style="background-color:rgb(255, 255, 255)"><span class="colour" style="color:rgb(51, 51, 51)"><span class="font" style="font-family:-apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'"><span class="size" style="font-size:16px"><a style="background-color:transparent;-webkit-text-decoration-skip:objects;color:rgb(64, 120, 192);text-decoration:none;" href="https://github.com/apple/swift-evolution/blob/master/proposals/0116-id-as-any.md" class="">SE-0116</a> changed how Objective-C's <code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">id</code> and untyped collections import into Swift to use the <code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">Any</code> type. This makes it much more natural to pass in Swift value types such as <code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">String</code> and <code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">Array</code>, but introduces the hazard of passing in types that don't bridge well to Objective-C objects. Particularly problematic are number types; whereas <code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">Int</code>, <code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">UInt</code>, and <code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">Double</code> will automatically bridge as <code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">NSNumber</code>, other-sized numeric types fall back to opaque boxing:</span></span></span></span><br class=""></p><div style="margin-bottom:16px;color:rgb(51, 51, 51);font-family:-apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol';font-size:16px;background-color:rgb(255, 255, 255);" class=""><pre style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;margin-top:0px;margin-bottom:0px;line-height:1.45;word-wrap:normal;padding-top:16px;padding-right:16px;padding-bottom:16px;padding-left:16px;overflow-y:auto;overflow-x:auto;background-color:rgb(247, 247, 247);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;word-break:normal;" class=""><span class="colour" style="color:rgb(167, 29, 93)">let</span> i <span class="colour" style="color:rgb(167, 29, 93)">=</span> <span class="colour" style="color:rgb(0, 134, 179)">17</span>
<span class="colour" style="color:rgb(167, 29, 93)">let</span> plist <span class="colour" style="color:rgb(167, 29, 93)">=</span> [<span class="colour" style="color:rgb(24, 54, 145)"><span style="" class="">"</span>seventeen<span style="" class="">"</span></span>: i]
<span class="colour" style="color:rgb(150, 152, 150)">// OK</span>
<span class="colour" style="color:rgb(167, 29, 93)">try</span><span class="colour" style="color:rgb(167, 29, 93)">!</span> NSJSONSerialization<span class="colour" style="color:rgb(167, 29, 93)">.</span>data(withJSONObject: plist)
<span class="colour" style="color:rgb(167, 29, 93)">let</span> j: <span class="colour" style="color:rgb(0, 134, 179)">UInt8</span> <span class="colour" style="color:rgb(167, 29, 93)">=</span> <span class="colour" style="color:rgb(0, 134, 179)">38</span>
<span class="colour" style="color:rgb(167, 29, 93)">let</span> brokenPlist <span class="colour" style="color:rgb(167, 29, 93)">=</span> [<span class="colour" style="color:rgb(24, 54, 145)"><span style="" class="">"</span>thirty-eight<span style="" class="">"</span></span>: j]
<span class="colour" style="color:rgb(150, 152, 150)">// Will throw because `j` didn't bridge to a JSON type</span>
<span class="colour" style="color:rgb(167, 29, 93)">try</span><span class="colour" style="color:rgb(167, 29, 93)">!</span> NSJSONSerialization<span class="colour" style="color:rgb(167, 29, 93)">.</span>data(withJSONObject: brokenPlist)<br class=""></pre></div><p style="margin-top: 0px; margin-bottom: 16px;" class=""><span class="highlight" style="background-color:rgb(255, 255, 255)"><span class="colour" style="color:rgb(51, 51, 51)"><span class="font" style="font-family:-apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'"><span class="size" style="font-size:16px">We had shied away from enabling this bridging for all numeric types in the Swift 1.x days, among other reasons because we allowed implicit bridging conversions in both directions from Swift value types to <code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">NS</code> objects and back, which meant that you could slowly and brokenly convert between any two numeric types transitively via NSNumber if we allowed this. We killed the implicit conversions completely with <a style="background-color:transparent;-webkit-text-decoration-skip:objects;color:rgb(64, 120, 192);text-decoration:none;" href="https://github.com/apple/swift-evolution/blob/master/proposals/0072-eliminate-implicit-bridging-conversions.md" class="">SE-0072</a> so that is no longer a concern, so expanding the bridging behavior should no longer be a major problem, since it must now always be explicitly asked for.</span></span></span></span><br class=""></p><p style="margin-top: 0px; margin-bottom: 16px;" class=""><span class="highlight" style="background-color:rgb(255, 255, 255)"><span class="colour" style="color:rgb(51, 51, 51)"><span class="font" style="font-family:-apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'"><span class="size" style="font-size:16px">There are also many Cocoa APIs that accept <code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">NSArray</code> and <code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">NSDictionary</code> objects with members that are <code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">NSValue</code>-boxed structs. Matt Neuberg highlights Core Automation as an example in <a style="background-color:transparent;-webkit-text-decoration-skip:objects;color:rgb(64, 120, 192);text-decoration:none;" href="https://bugs.swift.org/browse/SR-2414" class="">this bug report</a>. With <code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">id</code>-as-<code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">Any</code>, it's natural to expect this to work:</span></span></span></span><br class=""></p><div style="margin-bottom:16px;color:rgb(51, 51, 51);font-family:-apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol';font-size:16px;background-color:rgb(255, 255, 255);" class=""><pre style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;margin-top:0px;margin-bottom:0px;line-height:1.45;word-wrap:normal;padding-top:16px;padding-right:16px;padding-bottom:16px;padding-left:16px;overflow-y:auto;overflow-x:auto;background-color:rgb(247, 247, 247);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;word-break:normal;" class="">anim<span class="colour" style="color:rgb(167, 29, 93)">.</span>toValue <span class="colour" style="color:rgb(167, 29, 93)">=</span> CGPoint<span class="colour" style="color:rgb(167, 29, 93)">.</span>zero<br class=""></pre></div><p style="margin-top: 0px; margin-bottom: 16px;" class=""><span class="highlight" style="background-color:rgb(255, 255, 255)"><span class="colour" style="color:rgb(51, 51, 51)"><span class="font" style="font-family:-apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'"><span class="size" style="font-size:16px">However, the <code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">CGPoint</code> value does not box as a meaningful Objective-C object, so this currently breaks Core Animation at runtime despite compiling successfully. It would be more idiomatic to bridge these types to <code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">NSValue</code>.</span></span></span></span><br class=""></p><h2 style="margin-top:24px;margin-bottom:16px;line-height:1.25;padding-bottom:0.3em;border-bottom-width:1px;border-bottom-style:solid;border-bottom-color:rgb(238, 238, 238);color:rgb(51, 51, 51);font-family:-apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol';background-color:rgb(255, 255, 255);" class=""><a style="background-color:transparent;-webkit-text-decoration-skip:objects;color:rgb(64, 120, 192);text-decoration:none;float:left;padding-right:4px;line-height:1;" href="https://github.com/jckarter/swift-evolution/blob/be49e08f56450ffea394306198bcd25f58915e30/proposals/XXXX-bridge-nsnumber-and-nsvalue.md#proposed-solution" class=""></a>Proposed solution<br class=""></h2><p style="margin-top: 0px; margin-bottom: 16px;" class=""><span class="highlight" style="background-color:rgb(255, 255, 255)"><span class="colour" style="color:rgb(51, 51, 51)"><span class="font" style="font-family:-apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'"><span class="size" style="font-size:16px">All of Swift's number types should be made to bridge to <code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">NSNumber</code> when used as objects in Objective-C:</span></span></span></span><br class=""></p><ul style="padding-left:2em;margin-top:0px;margin-bottom:16px;color:rgb(51, 51, 51);font-family:-apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol';font-size:16px;background-color:rgb(255, 255, 255);" class=""><li style="" class=""><code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">Int8</code><br class=""></li><li style="margin-top:0.25em;" class=""><code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">Int16</code><br class=""></li><li style="margin-top:0.25em;" class=""><code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">Int32</code><br class=""></li><li style="margin-top:0.25em;" class=""><code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">Int64</code><br class=""></li><li style="margin-top:0.25em;" class=""><code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">UInt8</code><br class=""></li><li style="margin-top:0.25em;" class=""><code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">UInt16</code><br class=""></li><li style="margin-top:0.25em;" class=""><code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">UInt32</code><br class=""></li><li style="margin-top:0.25em;" class=""><code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">UInt64</code><br class=""></li><li style="margin-top:0.25em;" class=""><code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">Float</code><br class=""></li><li style="margin-top:0.25em;" class=""><code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">Double</code><br class=""></li></ul><p style="margin-top: 0px; margin-bottom: 16px;" class=""><span class="highlight" style="background-color:rgb(255, 255, 255)"><span class="colour" style="color:rgb(51, 51, 51)"><span class="font" style="font-family:-apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'"><span class="size" style="font-size:16px">Cocoa structs with existing <code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">NSValue</code> factory and property support should be made to bridge to <code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">NSValue</code> when used as objects:</span></span></span></span><br class=""></p><ul style="padding-left:2em;margin-top:0px;margin-bottom:16px;color:rgb(51, 51, 51);font-family:-apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol';font-size:16px;background-color:rgb(255, 255, 255);" class=""><li style="" class=""><code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">NSRange</code><br class=""></li><li style="margin-top:0.25em;" class=""><code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">CGPoint</code><br class=""></li><li style="margin-top:0.25em;" class=""><code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">CGVector</code><br class=""></li><li style="margin-top:0.25em;" class=""><code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">CGSize</code><br class=""></li><li style="margin-top:0.25em;" class=""><code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">CGRect</code><br class=""></li><li style="margin-top:0.25em;" class=""><code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">CGAffineTransform</code><br class=""></li><li style="margin-top:0.25em;" class=""><code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">UIEdgeInsets</code><br class=""></li><li style="margin-top:0.25em;" class=""><code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">UIOffset</code><br class=""></li><li style="margin-top:0.25em;" class=""><code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">CATransform3D</code><br class=""></li><li style="margin-top:0.25em;" class=""><code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">CMTime</code><br class=""></li><li style="margin-top:0.25em;" class=""><code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">CMTimeRange</code><br class=""></li><li style="margin-top:0.25em;" class=""><code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">CMTimeMapping</code><br class=""></li><li style="margin-top:0.25em;" class=""><code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">MKCoordinate</code><br class=""></li><li style="margin-top:0.25em;" class=""><code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">MKCoordinateSpan</code><br class=""></li><li style="margin-top:0.25em;" class=""><code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">SCNVector3</code><br class=""></li><li style="margin-top:0.25em;" class=""><code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">SCNVector4</code><br class=""></li><li style="margin-top:0.25em;" class=""><code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">SCNMatrix4</code><br class=""></li></ul><h2 style="margin-top:24px;margin-bottom:16px;line-height:1.25;padding-bottom:0.3em;border-bottom-width:1px;border-bottom-style:solid;border-bottom-color:rgb(238, 238, 238);color:rgb(51, 51, 51);font-family:-apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol';background-color:rgb(255, 255, 255);" class=""><a style="background-color:transparent;-webkit-text-decoration-skip:objects;color:rgb(64, 120, 192);text-decoration:none;float:left;padding-right:4px;line-height:1;" href="https://github.com/jckarter/swift-evolution/blob/be49e08f56450ffea394306198bcd25f58915e30/proposals/XXXX-bridge-nsnumber-and-nsvalue.md#detailed-design" class=""></a>Detailed design<br class=""></h2><p style="margin-top: 0px; margin-bottom: 16px;" class=""><span class="highlight" style="background-color:rgb(255, 255, 255)"><span class="colour" style="color:rgb(51, 51, 51)"><span class="font" style="font-family:-apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'"><span class="size" style="font-size:16px">Bridged <code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">NSNumber</code> and <code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">NSValue</code> objects must be castable back to their original Swift value types. <code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">NSValue</code> normally preserves the type information of its included struct in its <code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">objCType</code> property. We can check the <code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">objCType</code> of an <code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">NSValue</code> instance when attempting to cast back to a specific bridged struct type.</span></span></span></span><br class=""></p><p style="margin-top: 0px; margin-bottom: 16px;" class=""><span class="highlight" style="background-color:rgb(255, 255, 255)"><span class="colour" style="color:rgb(51, 51, 51)"><span class="font" style="font-family:-apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'"><span class="size" style="font-size:16px"><code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">NSNumber</code> is a bit trickier, since Cocoa's implementation does not generally guarantee to remember the exact number type an instance was constructed from. We can instead say that casting an <code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">NSNumber</code> to a Swift number type succeeds if the value of the <code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">NSNumber</code> is exactly representable as the target type. This is imperfect, since it means that an <code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">NSNumber</code>can potentially be cast to a different type from the original value, but it at least ensures that Swift values round-trip through the bridge without depending on <code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">NSNumber</code> implementation details.</span></span></span></span><br class=""></p><h2 style="margin-top:24px;margin-bottom:16px;line-height:1.25;padding-bottom:0.3em;border-bottom-width:1px;border-bottom-style:solid;border-bottom-color:rgb(238, 238, 238);color:rgb(51, 51, 51);font-family:-apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol';background-color:rgb(255, 255, 255);" class=""><a style="background-color:transparent;-webkit-text-decoration-skip:objects;color:rgb(64, 120, 192);text-decoration:none;float:left;padding-right:4px;line-height:1;" href="https://github.com/jckarter/swift-evolution/blob/be49e08f56450ffea394306198bcd25f58915e30/proposals/XXXX-bridge-nsnumber-and-nsvalue.md#impact-on-existing-code" class=""></a>Impact on existing code<br class=""></h2><p style="margin-top: 0px; margin-bottom: 16px;" class=""><span class="highlight" style="background-color:rgb(255, 255, 255)"><span class="colour" style="color:rgb(51, 51, 51)"><span class="font" style="font-family:-apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'"><span class="size" style="font-size:16px">This change has no static source impact, but changes the dynamic behavior of the Objective-C bridge. From Objective-C's perspective, values that used to bridge as opaque objects will now come in as semantically meaningful Objective-C objects. This should be a safe change, since existing code should not be relying on the behavior of opaque bridged objects. From Swift's perspective, values should still be able to round-trip from concrete number and struct types to <code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">Any</code>to <code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">id</code> to <code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">Any</code> and back by dynamic casting. The ability to reliably distinguish the exact number type that an <code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">NSNumber</code>was constructed from would be lost.</span></span></span></span><br class=""></p><h2 style="margin-top:24px;margin-bottom:16px;line-height:1.25;padding-bottom:0.3em;border-bottom-width:1px;border-bottom-style:solid;border-bottom-color:rgb(238, 238, 238);color:rgb(51, 51, 51);font-family:-apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol';background-color:rgb(255, 255, 255);" class=""><a style="background-color:transparent;-webkit-text-decoration-skip:objects;color:rgb(64, 120, 192);text-decoration:none;float:left;padding-right:4px;line-height:1;" href="https://github.com/jckarter/swift-evolution/blob/be49e08f56450ffea394306198bcd25f58915e30/proposals/XXXX-bridge-nsnumber-and-nsvalue.md#alternatives-considered" class=""></a>Alternatives considered<br class=""></h2><p style="margin-top: 0px; margin-bottom: 16px;" class=""><span class="highlight" style="background-color:rgb(255, 255, 255)"><span class="colour" style="color:rgb(51, 51, 51)"><span class="font" style="font-family:-apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'"><span class="size" style="font-size:16px">We can of course do nothing and leave the behavior as-is.</span></span></span></span><br class=""></p><div style="margin-top:0px;color:rgb(51, 51, 51);font-family:-apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol';font-size:16px;background-color:rgb(255, 255, 255);margin-bottom:0px !important;" class=""><code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">NSValue</code> also carries factories for <code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">valueWithPointer:</code> and <code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">valueWithNonretainedObject:</code>. Maybe we could bridge<code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">UnsafePointer</code> and <code style="font-family:Consolas, 'Liberation Mono', Menlo, Courier, monospace;font-size:13.600000381469727px;padding-top:0.2em;padding-right:0px;padding-bottom:0.2em;padding-left:0px;margin-top:0px;margin-right:0px;margin-bottom:0px;margin-left:0px;background-color:rgba(0, 0, 0, 0.0392157);border-top-left-radius:3px;border-top-right-radius:3px;border-bottom-right-radius:3px;border-bottom-left-radius:3px;" class="">Unmanaged</code> this way, but we probably shouldn’t.<br class=""></div>
<div style="margin-top:0px;color:rgb(51, 51, 51);font-family:-apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol';font-size:16px;background-color:rgb(255, 255, 255);margin-bottom:0px !important;" class=""><br class=""></div>
<div style="margin-top:0px;color:rgb(51, 51, 51);font-family:-apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol';font-size:16px;background-color:rgb(255, 255, 255);margin-bottom:0px !important;" class=""><span style="white-space:pre;" class=""></span>- Doug<br class=""></div>
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