<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="">Name updated: <a href="https://github.com/apple/swift-evolution/pull/281" class="">https://github.com/apple/swift-evolution/pull/281</a><div class=""><br class=""><div><blockquote type="cite" class=""><div class="">On 02 May 2016, at 09:39, David Hart <<a href="mailto:david@hartbit.com" class="">david@hartbit.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><meta http-equiv="content-type" content="text/html; charset=utf-8" class=""><div dir="auto" class=""><div class="">I'll update the proposal ASAP :) Btw, wasn't sure if you wanted to be cited as co-author because I did not have your express approval, but I thought it was the right thing to do. Was in a bit in a hurry to send the Pull Request before going to work.</div><div class=""><br class="">On 02 May 2016, at 09:20, Developer <<a href="mailto:devteam.codafi@gmail.com" class="">devteam.codafi@gmail.com</a>> wrote:<br class=""><br class=""></div><blockquote type="cite" class=""><div class=""><meta http-equiv="content-type" content="text/html; charset=utf-8" class=""><div class="">Hi there, just wanted to let you know I have a name! It's unfortunate that the mailing list won't accept the update I've made (this has been the 3rd-ish time I've tried).<br class=""><br class="">~Robert Widmann</div><div class=""><br class="">2016/05/02 3:16、David Hart <<a href="mailto:david@hartbit.com" class="">david@hartbit.com</a>> のメッセージ:<br class=""><br class=""></div><blockquote type="cite" class=""><div class=""><meta http-equiv="Content-Type" content="text/html charset=utf-8" class="">Hello swift-evolution,<div class=""><br class=""></div><div class="">I took the pitch originally from Developer to move the where clause out of the generic parameter list, with improvements brought up by Pyry Jahkola, and wrote a proposal for it. I opened a Pull Request, but if anybody wants to bring some modifications to it before it is merged, please let me know what you think:</div><div class=""><br class=""></div><div class=""><h1 style="box-sizing: border-box; font-size: 2.25em; margin-right: 0px; margin-bottom: 16px; margin-left: 0px; line-height: 1.2; 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: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; background-color: rgb(255, 255, 255); margin-top: 0px !important;" class="">Move where clause to end of declaration</h1><ul style="box-sizing: border-box; padding-left: 2em; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class=""><li style="box-sizing: border-box;" class="">Proposal: <a href="https://github.com/apple/swift-evolution/blob/master/proposals/XXXX-move-where-expression.md" style="box-sizing: border-box; background-color: transparent; -webkit-text-decoration-skip: objects; color: rgb(64, 120, 192); text-decoration: none;" class="">SE-XXXX</a></li><li style="box-sizing: border-box;" class="">Author(s): <a href="https://github.com/hartbit" style="box-sizing: border-box; background-color: transparent; -webkit-text-decoration-skip: objects; color: rgb(64, 120, 192); text-decoration: none;" class="">David Hart</a>, Developer, <a href="https://github.com/hartbit/swift-evolution/blob/move-where-clause/proposals/pyry.jahkola@iki.fi" style="box-sizing: border-box; background-color: transparent; -webkit-text-decoration-skip: objects; color: rgb(64, 120, 192); text-decoration: none;" class="">Pry Jahkola</a></li><li style="box-sizing: border-box;" class="">Status: TBD</li><li style="box-sizing: border-box;" class="">Review manager: TBD</li></ul><h2 style="box-sizing: border-box; margin-top: 1em; margin-bottom: 16px; line-height: 1.225; font-size: 1.75em; 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: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; background-color: rgb(255, 255, 255);" class=""><a id="user-content-introduction" class="anchor" href="https://github.com/hartbit/swift-evolution/blob/move-where-clause/proposals/XXXX-move-where-expression.md#introduction" aria-hidden="true" style="box-sizing: border-box; background-color: transparent; -webkit-text-decoration-skip: objects; color: rgb(64, 120, 192); text-decoration: none; display: inline-block; padding-right: 2px; margin-left: -18px; line-height: 1;"><svg aria-hidden="true" class="octicon octicon-link" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path d="M4 9h1v1h-1c-1.5 0-3-1.69-3-3.5s1.55-3.5 3-3.5h4c1.45 0 3 1.69 3 3.5 0 1.41-0.91 2.72-2 3.25v-1.16c0.58-0.45 1-1.27 1-2.09 0-1.28-1.02-2.5-2-2.5H4c-0.98 0-2 1.22-2 2.5s1 2.5 2 2.5z m9-3h-1v1h1c1 0 2 1.22 2 2.5s-1.02 2.5-2 2.5H9c-0.98 0-2-1.22-2-2.5 0-0.83 0.42-1.64 1-2.09v-1.16c-1.09 0.53-2 1.84-2 3.25 0 1.81 1.55 3.5 3 3.5h4c1.45 0 3-1.69 3-3.5s-1.5-3.5-3-3.5z"></path></svg></a>Introduction</h2><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class="">This proposal suggests moving the <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 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="">where</code> clause to the end of the declaration syntax, but before the body, for readability reasons. It has been discussed at length on the following swift-evolution thread:</p><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class=""><a href="https://github.com/hartbit/swift-evolution/blob/move-where-clause/proposals/GMANE_DOWN_FOR_NOW" style="box-sizing: border-box; background-color: transparent; -webkit-text-decoration-skip: objects; color: rgb(64, 120, 192); text-decoration: none;" class="">[Pitch] Moving where Clauses Out Of Parameter Lists</a></p><h2 style="box-sizing: border-box; margin-top: 1em; margin-bottom: 16px; line-height: 1.225; font-size: 1.75em; 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: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; background-color: rgb(255, 255, 255);" class=""><a id="user-content-motivation" class="anchor" href="https://github.com/hartbit/swift-evolution/blob/move-where-clause/proposals/XXXX-move-where-expression.md#motivation" aria-hidden="true" style="box-sizing: border-box; background-color: transparent; -webkit-text-decoration-skip: objects; color: rgb(64, 120, 192); text-decoration: none; display: inline-block; padding-right: 2px; margin-left: -18px; line-height: 1;"><svg aria-hidden="true" class="octicon octicon-link" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path d="M4 9h1v1h-1c-1.5 0-3-1.69-3-3.5s1.55-3.5 3-3.5h4c1.45 0 3 1.69 3 3.5 0 1.41-0.91 2.72-2 3.25v-1.16c0.58-0.45 1-1.27 1-2.09 0-1.28-1.02-2.5-2-2.5H4c-0.98 0-2 1.22-2 2.5s1 2.5 2 2.5z m9-3h-1v1h1c1 0 2 1.22 2 2.5s-1.02 2.5-2 2.5H9c-0.98 0-2-1.22-2-2.5 0-0.83 0.42-1.64 1-2.09v-1.16c-1.09 0.53-2 1.84-2 3.25 0 1.81 1.55 3.5 3 3.5h4c1.45 0 3-1.69 3-3.5s-1.5-3.5-3-3.5z"></path></svg></a>Motivation</h2><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class="">The <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 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="">where</code> clause in declarations can become quite long. When that happens, it breaks the declaration syntax in two, hurting its readability. There is also no good way of formatting the declaration syntax to make it much better.</p><h2 style="box-sizing: border-box; margin-top: 1em; margin-bottom: 16px; line-height: 1.225; font-size: 1.75em; 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: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; background-color: rgb(255, 255, 255);" class=""><a id="user-content-proposed-solution" class="anchor" href="https://github.com/hartbit/swift-evolution/blob/move-where-clause/proposals/XXXX-move-where-expression.md#proposed-solution" aria-hidden="true" style="box-sizing: border-box; background-color: transparent; -webkit-text-decoration-skip: objects; color: rgb(64, 120, 192); text-decoration: none; display: inline-block; padding-right: 2px; margin-left: -18px; line-height: 1;"><svg aria-hidden="true" class="octicon octicon-link" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path d="M4 9h1v1h-1c-1.5 0-3-1.69-3-3.5s1.55-3.5 3-3.5h4c1.45 0 3 1.69 3 3.5 0 1.41-0.91 2.72-2 3.25v-1.16c0.58-0.45 1-1.27 1-2.09 0-1.28-1.02-2.5-2-2.5H4c-0.98 0-2 1.22-2 2.5s1 2.5 2 2.5z m9-3h-1v1h1c1 0 2 1.22 2 2.5s-1.02 2.5-2 2.5H9c-0.98 0-2-1.22-2-2.5 0-0.83 0.42-1.64 1-2.09v-1.16c-1.09 0.53-2 1.84-2 3.25 0 1.81 1.55 3.5 3 3.5h4c1.45 0 3-1.69 3-3.5s-1.5-3.5-3-3.5z"></path></svg></a>Proposed solution</h2><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class="">The proposal suggests moving the <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 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="">where</code> clause at the end of the declaration, but before the body of concerned declarations. With the proposed change, <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 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="">where</code> clauses do not impede the main declaration and are also more easily formattable. For example, here is the same function declaration before and after the change: </p><div class="highlight highlight-source-swift" style="box-sizing: border-box; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);"><pre style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; margin-top: 0px; margin-bottom: 0px; line-height: 1.45; padding: 16px; overflow: 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-wrap: normal; word-break: normal;" class=""><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">func</span> <span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">anyCommonElements</span><T <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">:</span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">SequenceType</span>, U <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">:</span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">SequenceType</span> <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">where</span>
T<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>Generator<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>Element: <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">Equatable</span>,
T<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>Generator<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>Element <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">==</span> U<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>Generator<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>Element>(lhs: T, <span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">_</span> <span class="pl-smi" style="box-sizing: border-box;">rhs</span>: U) <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">-></span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">Bool</span> where
{
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">...</span>
}
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">func</span> <span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">anyCommonElements</span><T <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">:</span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">SequenceType</span>, U <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">:</span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">SequenceType</span>>(lhs: T, <span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">_</span> <span class="pl-smi" style="box-sizing: border-box;">rhs</span>: U) <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">-></span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">Bool</span> where
T<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>Generator<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>Element: <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">Equatable</span>,
T<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>Generator<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>Element <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">==</span> U<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>Generator<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>Element
{
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">...</span>
}</pre></div><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class="">This proposal has no impact on extension declarations with constraints because those declarations already have the <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 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="">where</code> clauses right before the body. In that regard, the proposal makes the other declarations more consistent with extension declarations.</p><h2 style="box-sizing: border-box; margin-top: 1em; margin-bottom: 16px; line-height: 1.225; font-size: 1.75em; 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: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; background-color: rgb(255, 255, 255);" class=""><a id="user-content-detailed-design" class="anchor" href="https://github.com/hartbit/swift-evolution/blob/move-where-clause/proposals/XXXX-move-where-expression.md#detailed-design" aria-hidden="true" style="box-sizing: border-box; background-color: transparent; -webkit-text-decoration-skip: objects; color: rgb(64, 120, 192); text-decoration: none; display: inline-block; padding-right: 2px; margin-left: -18px; line-height: 1;"><svg aria-hidden="true" class="octicon octicon-link" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path d="M4 9h1v1h-1c-1.5 0-3-1.69-3-3.5s1.55-3.5 3-3.5h4c1.45 0 3 1.69 3 3.5 0 1.41-0.91 2.72-2 3.25v-1.16c0.58-0.45 1-1.27 1-2.09 0-1.28-1.02-2.5-2-2.5H4c-0.98 0-2 1.22-2 2.5s1 2.5 2 2.5z m9-3h-1v1h1c1 0 2 1.22 2 2.5s-1.02 2.5-2 2.5H9c-0.98 0-2-1.22-2-2.5 0-0.83 0.42-1.64 1-2.09v-1.16c-1.09 0.53-2 1.84-2 3.25 0 1.81 1.55 3.5 3 3.5h4c1.45 0 3-1.69 3-3.5s-1.5-3.5-3-3.5z"></path></svg></a>Detailed design</h2><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class="">First of all, the grammar of <em style="box-sizing: border-box;" class="">generic-parameter-clause</em> is modified to loose the <em style="box-sizing: border-box;" class="">requirement- clause</em>:</p><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class=""><em style="box-sizing: border-box;" class="">generic-parameter-clause</em> → <span style="box-sizing: border-box;" class=""><</span> <em style="box-sizing: border-box;" class="">generic-parameter-list</em> <span style="box-sizing: border-box;" class="">></span></p><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class="">The grammar of declarations are then amended to gain the <em style="box-sizing: border-box;" class="">requirement-clause</em>: </p><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class=""><em style="box-sizing: border-box;" class="">function-declaration</em> → <em style="box-sizing: border-box;" class="">function-head</em> <em style="box-sizing: border-box;" class="">function-name</em> <em style="box-sizing: border-box;" class="">generic-parameter-clause<span style="box-sizing: border-box; font-size: 12px; line-height: 0; position: relative; vertical-align: baseline; bottom: -0.25em;" class="">opt</span></em> <em style="box-sizing: border-box;" class="">function-signature</em> <em style="box-sizing: border-box;" class="">requirement-clause<span style="box-sizing: border-box; font-size: 12px; line-height: 0; position: relative; vertical-align: baseline; bottom: -0.25em;" class="">opt</span></em> <em style="box-sizing: border-box;" class="">function-body<span style="box-sizing: border-box; font-size: 12px; line-height: 0; position: relative; vertical-align: baseline; bottom: -0.25em;" class="">opt</span></em></p><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class=""><em style="box-sizing: border-box;" class="">union-style-enum</em> → <span style="box-sizing: border-box;" class="">indirect</span><em style="box-sizing: border-box;" class=""><span style="box-sizing: border-box; font-size: 12px; line-height: 0; position: relative; vertical-align: baseline; bottom: -0.25em;" class="">opt</span></em> <span style="box-sizing: border-box;" class="">enum</span> <em style="box-sizing: border-box;" class="">enum-name</em> <em style="box-sizing: border-box;" class="">generic-parameter-clause<span style="box-sizing: border-box; font-size: 12px; line-height: 0; position: relative; vertical-align: baseline; bottom: -0.25em;" class="">opt</span></em> <em style="box-sizing: border-box;" class="">type-inheritance-clause<span style="box-sizing: border-box; font-size: 12px; line-height: 0; position: relative; vertical-align: baseline; bottom: -0.25em;" class="">opt</span></em> <em style="box-sizing: border-box;" class="">requirement-clause<span style="box-sizing: border-box; font-size: 12px; line-height: 0; position: relative; vertical-align: baseline; bottom: -0.25em;" class="">opt</span></em> <span style="box-sizing: border-box;" class="">{</span> <em style="box-sizing: border-box;" class="">union-style-enum-members<span style="box-sizing: border-box; font-size: 12px; line-height: 0; position: relative; vertical-align: baseline; bottom: -0.25em;" class="">opt</span></em> <span style="box-sizing: border-box;" class="">}</span></p><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class=""><em style="box-sizing: border-box;" class="">raw-value-style-enum</em> → <span style="box-sizing: border-box;" class="">enum</span> <em style="box-sizing: border-box;" class="">enum-name</em> <em style="box-sizing: border-box;" class="">generic-parameter-clause<span style="box-sizing: border-box; font-size: 12px; line-height: 0; position: relative; vertical-align: baseline; bottom: -0.25em;" class="">opt</span></em> <em style="box-sizing: border-box;" class="">type-inheritance-clause</em> <em style="box-sizing: border-box;" class="">requirement-clause<span style="box-sizing: border-box; font-size: 12px; line-height: 0; position: relative; vertical-align: baseline; bottom: -0.25em;" class="">opt</span></em> <span style="box-sizing: border-box;" class="">{</span> <em style="box-sizing: border-box;" class="">raw-value-style-enum-members</em> *<em style="box-sizing: border-box;" class="">}</em>*</p><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class=""><em style="box-sizing: border-box;" class="">struct-declaration</em> → <em style="box-sizing: border-box;" class="">attributes<span style="box-sizing: border-box; font-size: 12px; line-height: 0; position: relative; vertical-align: baseline; bottom: -0.25em;" class="">opt</span></em> <em style="box-sizing: border-box;" class="">access-level-modifier<span style="box-sizing: border-box; font-size: 12px; line-height: 0; position: relative; vertical-align: baseline; bottom: -0.25em;" class="">opt</span></em> <span style="box-sizing: border-box;" class="">struct</span> <em style="box-sizing: border-box;" class="">struct-name</em> <em style="box-sizing: border-box;" class="">generic-parameter-clause<span style="box-sizing: border-box; font-size: 12px; line-height: 0; position: relative; vertical-align: baseline; bottom: -0.25em;" class="">opt</span></em> <em style="box-sizing: border-box;" class="">type-inheritance-clause<span style="box-sizing: border-box; font-size: 12px; line-height: 0; position: relative; vertical-align: baseline; bottom: -0.25em;" class="">opt</span></em> <em style="box-sizing: border-box;" class="">requirement-clause<span style="box-sizing: border-box; font-size: 12px; line-height: 0; position: relative; vertical-align: baseline; bottom: -0.25em;" class="">opt</span></em> <em style="box-sizing: border-box;" class="">struct-body</em></p><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class=""><em style="box-sizing: border-box;" class="">class-declaration</em> → <em style="box-sizing: border-box;" class="">attributes<span style="box-sizing: border-box; font-size: 12px; line-height: 0; position: relative; vertical-align: baseline; bottom: -0.25em;" class="">opt</span></em> <em style="box-sizing: border-box;" class="">access-level-modifier<span style="box-sizing: border-box; font-size: 12px; line-height: 0; position: relative; vertical-align: baseline; bottom: -0.25em;" class="">opt</span></em> <span style="box-sizing: border-box;" class="">final</span><em style="box-sizing: border-box;" class=""><span style="box-sizing: border-box; font-size: 12px; line-height: 0; position: relative; vertical-align: baseline; bottom: -0.25em;" class="">opt</span></em> <span style="box-sizing: border-box;" class="">class</span> <em style="box-sizing: border-box;" class="">class-name</em> <em style="box-sizing: border-box;" class="">generic-parameter-clause<span style="box-sizing: border-box; font-size: 12px; line-height: 0; position: relative; vertical-align: baseline; bottom: -0.25em;" class="">opt</span></em> <em style="box-sizing: border-box;" class="">type-inheritance-clause<span style="box-sizing: border-box; font-size: 12px; line-height: 0; position: relative; vertical-align: baseline; bottom: -0.25em;" class="">opt</span></em> <em style="box-sizing: border-box;" class="">requirement-clause<span style="box-sizing: border-box; font-size: 12px; line-height: 0; position: relative; vertical-align: baseline; bottom: -0.25em;" class="">opt</span></em> <em style="box-sizing: border-box;" class="">class-body</em></p><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class=""><em style="box-sizing: border-box;" class="">protocol-method-declaration</em> → <em style="box-sizing: border-box;" class="">function-head</em> <em style="box-sizing: border-box;" class="">function-name</em> <em style="box-sizing: border-box;" class="">generic-parameter-clause<span style="box-sizing: border-box; font-size: 12px; line-height: 0; position: relative; vertical-align: baseline; bottom: -0.25em;" class="">opt</span></em> <em style="box-sizing: border-box;" class="">function-signature</em> <em style="box-sizing: border-box;" class="">requirement-clause<span style="box-sizing: border-box; font-size: 12px; line-height: 0; position: relative; vertical-align: baseline; bottom: -0.25em;" class="">opt</span></em></p><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class=""><em style="box-sizing: border-box;" class="">protocol-initializer-declaration</em> → <em style="box-sizing: border-box;" class="">initializer-head</em> <em style="box-sizing: border-box;" class="">generic-parameter-clause<span style="box-sizing: border-box; font-size: 12px; line-height: 0; position: relative; vertical-align: baseline; bottom: -0.25em;" class="">opt</span></em> <em style="box-sizing: border-box;" class="">parameter-clause</em> <span style="box-sizing: border-box;" class="">throws</span><em style="box-sizing: border-box;" class=""><span style="box-sizing: border-box; font-size: 12px; line-height: 0; position: relative; vertical-align: baseline; bottom: -0.25em;" class="">opt</span></em> <em style="box-sizing: border-box;" class="">requirement-clause<span style="box-sizing: border-box; font-size: 12px; line-height: 0; position: relative; vertical-align: baseline; bottom: -0.25em;" class="">opt</span></em></p><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class=""><em style="box-sizing: border-box;" class="">protocol-initializer-declaration</em> → <em style="box-sizing: border-box;" class="">initializer-head</em> <em style="box-sizing: border-box;" class="">generic-parameter-clause<span style="box-sizing: border-box; font-size: 12px; line-height: 0; position: relative; vertical-align: baseline; bottom: -0.25em;" class="">opt</span></em> <em style="box-sizing: border-box;" class="">parameter-clause</em> <span style="box-sizing: border-box;" class="">rethrows</span> <em style="box-sizing: border-box;" class="">requirement-clause<span style="box-sizing: border-box; font-size: 12px; line-height: 0; position: relative; vertical-align: baseline; bottom: -0.25em;" class="">opt</span></em></p><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class=""><em style="box-sizing: border-box;" class="">initializer-declaration</em> → <em style="box-sizing: border-box;" class="">initializer-head</em> <em style="box-sizing: border-box;" class="">generic-parameter-clause<span style="box-sizing: border-box; font-size: 12px; line-height: 0; position: relative; vertical-align: baseline; bottom: -0.25em;" class="">opt</span></em> <em style="box-sizing: border-box;" class="">parameter-clause</em> <span style="box-sizing: border-box;" class="">throws</span><em style="box-sizing: border-box;" class=""><span style="box-sizing: border-box; font-size: 12px; line-height: 0; position: relative; vertical-align: baseline; bottom: -0.25em;" class="">opt</span></em> <em style="box-sizing: border-box;" class="">requirement-clause<span style="box-sizing: border-box; font-size: 12px; line-height: 0; position: relative; vertical-align: baseline; bottom: -0.25em;" class="">opt</span></em> <em style="box-sizing: border-box;" class="">initializer-body</em></p><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class=""><em style="box-sizing: border-box;" class="">initializer-declaration</em> → <em style="box-sizing: border-box;" class="">initializer-head</em> <em style="box-sizing: border-box;" class="">generic-parameter-clause<span style="box-sizing: border-box; font-size: 12px; line-height: 0; position: relative; vertical-align: baseline; bottom: -0.25em;" class="">opt</span></em> <em style="box-sizing: border-box;" class="">parameter-clause</em> <span style="box-sizing: border-box;" class="">rethrows</span> <em style="box-sizing: border-box;" class="">requirement-clause<span style="box-sizing: border-box; font-size: 12px; line-height: 0; position: relative; vertical-align: baseline; bottom: -0.25em;" class="">opt</span></em> <em style="box-sizing: border-box;" class="">initializer-body</em></p><h2 style="box-sizing: border-box; margin-top: 1em; margin-bottom: 16px; line-height: 1.225; font-size: 1.75em; 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: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; background-color: rgb(255, 255, 255);" class=""><a id="user-content-impact-on-existing-code" class="anchor" href="https://github.com/hartbit/swift-evolution/blob/move-where-clause/proposals/XXXX-move-where-expression.md#impact-on-existing-code" aria-hidden="true" style="box-sizing: border-box; background-color: transparent; -webkit-text-decoration-skip: objects; color: rgb(64, 120, 192); text-decoration: none; display: inline-block; padding-right: 2px; margin-left: -18px; line-height: 1;"><svg aria-hidden="true" class="octicon octicon-link" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path d="M4 9h1v1h-1c-1.5 0-3-1.69-3-3.5s1.55-3.5 3-3.5h4c1.45 0 3 1.69 3 3.5 0 1.41-0.91 2.72-2 3.25v-1.16c0.58-0.45 1-1.27 1-2.09 0-1.28-1.02-2.5-2-2.5H4c-0.98 0-2 1.22-2 2.5s1 2.5 2 2.5z m9-3h-1v1h1c1 0 2 1.22 2 2.5s-1.02 2.5-2 2.5H9c-0.98 0-2-1.22-2-2.5 0-0.83 0.42-1.64 1-2.09v-1.16c-1.09 0.53-2 1.84-2 3.25 0 1.81 1.55 3.5 3 3.5h4c1.45 0 3-1.69 3-3.5s-1.5-3.5-3-3.5z"></path></svg></a>Impact on existing code</h2><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class="">This proposal impacts all declarations which contain where clauses expect for extension declarations and will therefore require a Fix-It. </p><h2 style="box-sizing: border-box; margin-top: 1em; margin-bottom: 16px; line-height: 1.225; font-size: 1.75em; 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: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; background-color: rgb(255, 255, 255);" class=""><a id="user-content-alternatives-considered" class="anchor" href="https://github.com/hartbit/swift-evolution/blob/move-where-clause/proposals/XXXX-move-where-expression.md#alternatives-considered" aria-hidden="true" style="box-sizing: border-box; background-color: transparent; -webkit-text-decoration-skip: objects; color: rgb(64, 120, 192); text-decoration: none; display: inline-block; padding-right: 2px; margin-left: -18px; line-height: 1;"><svg aria-hidden="true" class="octicon octicon-link" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path d="M4 9h1v1h-1c-1.5 0-3-1.69-3-3.5s1.55-3.5 3-3.5h4c1.45 0 3 1.69 3 3.5 0 1.41-0.91 2.72-2 3.25v-1.16c0.58-0.45 1-1.27 1-2.09 0-1.28-1.02-2.5-2-2.5H4c-0.98 0-2 1.22-2 2.5s1 2.5 2 2.5z m9-3h-1v1h1c1 0 2 1.22 2 2.5s-1.02 2.5-2 2.5H9c-0.98 0-2-1.22-2-2.5 0-0.83 0.42-1.64 1-2.09v-1.16c-1.09 0.53-2 1.84-2 3.25 0 1.81 1.55 3.5 3 3.5h4c1.45 0 3-1.69 3-3.5s-1.5-3.5-3-3.5z"></path></svg></a>Alternatives considered</h2><p style="box-sizing: border-box; margin-top: 0px; margin-bottom: 16px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255);" class="">The first post in the swift-evolution thread originally proposed moving the <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 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="">where</code> clause just after the generic type declaration. Since then, the original author and many other participants in the thread have agreed that the current proposal is superior.</p><div style="box-sizing: border-box; margin-top: 0px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, 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="">It was also proposed to remove the simple inheritance constraints from the generic parameter list, but several arguments were brought up that it would complicate declarations of simple generics which only needed inheritance constraints.</div></div></div></blockquote></div></blockquote></div></div></blockquote></div><br class=""></div></body></html>