<html><head><style>body{font-family:Helvetica,Arial;font-size:13px}</style></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;"><div id="bloop_customfont" style="font-family:Helvetica,Arial;font-size:13px; color: rgba(0,0,0,1.0); margin: 0px; line-height: auto;">Because it’s not up to the client to decide how the design of the API supposed to work.</div> <br> <div id="bloop_sign_1487546957218615040" class="bloop_sign"><div style="font-family:helvetica,arial;font-size:13px">-- <br>Adrian Zubarev<br>Sent with Airmail</div></div> <br><p class="airmail_on">Am 20. Februar 2017 um 00:28:38, David Hart (<a href="mailto:david@hartbit.com">david@hartbit.com</a>) schrieb:</p> <blockquote type="cite" class="clean_bq"><span><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div></div><div>
<title></title>
<br class="">
<div>
<blockquote type="cite" class="">
<div class="">On 20 Feb 2017, at 00:19, Adrian Zubarev <<a href="mailto:adrian.zubarev@devandartist.com" class="">adrian.zubarev@devandartist.com</a>> wrote:</div>
<br class="Apple-interchange-newline">
<div class="">
<div class="bloop_markdown" style="font-family: Helvetica, Arial; font-size: 13px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(254, 254, 254);">
<p style="margin: 15px 0px; -webkit-margin-before: 0px;" class="">
I’m polite but I don’t see why every single piece is questioned
with “why”.</p>
<p style="margin: 15px 0px;" class="">Your example is exactly the
workaround I presented in first place. Interesting right? But it
still fails the challenge, because the set of types can be extended
by the client, however at least with this there won’t be any
runtime crashes in Swift 3.X</p>
</div>
</div>
</blockquote>
<div>In this example, I don’t see why it’s a problem to have types
be extended by the client:</div>
<div><br class=""></div>
<div>struct Person {</div>
<div> let firstName: String</div>
<div> let lastName: String</div>
<div> let id: String</div>
<div>}</div>
<div><br class=""></div>
<div>extension Person : KeyConvertible {</div>
<div> var key: Key {</div>
<div> return .string(id)</div>
<div> }</div>
<div>}</div>
<br class="">
<blockquote type="cite" class="">
<div class="">
<div class="bloop_original_html" style="font-family: Helvetica, Arial; font-size: 13px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(254, 254, 254);">
<div id="bloop_sign_1487546153884505088" class="bloop_sign">
<div style="font-family: helvetica, arial; font-size: 13px;" class="">-- <br class="">
Adrian Zubarev<br class="">
Sent with Airmail</div>
</div>
<br class="">
<p class="airmail_on" style="margin: 15px 0px;">Am 20. Februar 2017
um 00:14:28, David Hart (<a href="mailto:david@hartbit.com" style="color: rgb(65, 131, 196); background-color: inherit; text-decoration: none;" class="">david@hartbit.com</a>) schrieb:</p>
<blockquote type="cite" class="clean_bq" style="margin: 15px 0px;">
<div class="" style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;">
<div class=""></div>
<div class=""><span style="margin-top: 0px; margin-bottom: 0px;" class=""><br class=""></span>
<div class="">
<blockquote type="cite" class="" style="margin: 15px 0px;">
<div class="" style="margin-top: 0px;"><span style="margin-top: 0px; margin-bottom: 0px;" class="">On 20 Feb 2017, at
00:10, Adrian Zubarev via swift-evolution <<a href="mailto:swift-evolution@swift.org" class="" style="color: rgb(65, 131, 196); background-color: inherit; text-decoration: none;">swift-evolution@swift.org</a>>
wrote:</span></div>
<span style="margin-top: 0px; margin-bottom: 0px;" class=""><br class="Apple-interchange-newline"></span>
<div class="" style="margin-bottom: 0px;">
<div class="bloop_markdown" style="font-family: Helvetica, Arial; font-size: 13px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(254, 254, 254);">
<p class="" style="margin: 15px 0px; -webkit-margin-before: 0px;">
<span style="margin-top: 0px; margin-bottom: 0px;" class="">Because<span class="Apple-converted-space"> </span><code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal; -webkit-margin-before: 0px;">someInstance["key",
.string("key1"), .integer(1), .string(stringKeyInstance),
.integer(intIndexInstance), .integer(intIndexInstance),
…]</code><span class="Apple-converted-space"> </span>is simply
ugly and should be hidden. Such API looks horrible.</span></p>
<p class="" style="margin: 15px 0px;">Is this discussion really
going to end with every statement being questioned with “why”? Why
is 42 the number that rules the universe?</p>
</div>
</div>
</blockquote>
<div class="">Lets stay polite and keep things civil.</div>
<div class=""><br class=""></div>
<div class="">The "the client should not be able to extend the set
of types you can pass to that subscript.” requirement seems totally
arbitrary and an anti-pattern. I’m perfectly happy with:</div>
<div class=""><br class=""></div>
<div class="">enum Key {<br class="">
case string(String)<br class="">
case int(Int)<br class="">
}<br class="">
<br class="">
protocol KeyConvertible {<br class="">
var key: Key { get }<br class="">
}<br class="">
<br class="">
subscript(initial: String, others: KeyConvertible...)
-> Foo</div>
<br class="">
<blockquote type="cite" class="" style="margin: 15px 0px;">
<div class="" style="margin-top: 0px; margin-bottom: 0px;">
<div class="bloop_original_html" style="font-family: Helvetica, Arial; font-size: 13px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(254, 254, 254);">
<div id="bloop_sign_1487545491369880064" class="bloop_sign">
<div class="" style="font-family: helvetica, arial; font-size: 13px;">
-- <br class="">
Adrian Zubarev<br class="">
Sent with Airmail</div>
</div>
<br class="">
<p class="airmail_on" style="margin: 15px 0px;">Am 20. Februar 2017
um 00:03:44, Xiaodi Wu (<a href="mailto:xiaodi.wu@gmail.com" class="" style="color: rgb(65, 131, 196); background-color: inherit; text-decoration: none;">xiaodi.wu@gmail.com</a>)
schrieb:</p>
<blockquote type="cite" class="clean_bq" style="margin: 15px 0px;">
<div class="" style="margin-top: 0px; margin-bottom: 0px;">
<div class=""></div>
<div class="">
<div dir="ltr" class="">
<div class="gmail_extra">
<div class="gmail_quote"><span class="" style="margin-top: 0px; margin-bottom: 0px;">On Sun, Feb 19, 2017 at 4:51
PM, Adrian Zubarev<span class="Apple-converted-space"> </span><span dir="ltr" class=""><<a href="mailto:adrian.zubarev@devandartist.com" target="_blank" class="" style="color: rgb(65, 131, 196); background-color: inherit; text-decoration: none;">adrian.zubarev@devandartist.com</a>></span><span class="Apple-converted-space"> </span>wrote:<br class="">
</span>
<blockquote class="gmail_quote" style="margin: 0px 0px 0px 0.8ex; border-left-width: 1px; border-left-color: rgb(204, 204, 204); border-left-style: solid; padding-left: 1ex;">
<div class="" style="margin-top: 0px; margin-bottom: 0px; word-wrap: break-word;">
<div class="m_2275515528959643236bloop_markdown">
<p class="" style="margin: 15px 0px;">Matthew has pretty much
summed up everything with a single question in his last reply. It
makes me tired of repeating myself over and over again.</p>
<p class="" style="margin: 15px 0px;">Here’s the challenge for
you:</p>
<p class="" style="margin: 15px 0px;">Implement a subscript where
the first parameter is a String (trivial), but the second to n are
String’s and/or Int’s. There is no restriction of order for the
Int’s and String’s and there could be as many as you’d like, so no
overloads are allowed (a hint: variadics). You should be able to
use variables in that subscript and literals. You’re not allowed to
use enum constructors</p>
</div>
</div>
</blockquote>
<div class="">Why not? You want a parameter that takes either
String or Int. In another language, you might express this as
`String | Int`, but Chris Lattner and others have said on this list
that enums are the intended way of expressing this in
Swift.<br class=""></div>
<blockquote class="gmail_quote" style="margin: 0px 0px 0px 0.8ex; border-left-width: 1px; border-left-color: rgb(204, 204, 204); border-left-style: solid; padding-left: 1ex;">
<div class="" style="margin-top: 0px; margin-bottom: 0px; word-wrap: break-word;">
<div class="m_2275515528959643236bloop_markdown">
<p class="" style="margin: 15px 0px;">and the client should not be
able to extend the set of types you can pass to that subscript.
That said it can look like this:<span class="Apple-converted-space"> </span><code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;">someInstance["key",
"key1", 1, stringKeyInstance, intIndexInstance, intIndexInstance,
…]</code></p>
<p class="" style="margin: 15px 0px;">Creating hacks like
unreachable types with hidden inits is prohibited.</p>
<p class="" style="margin: 15px 0px;">Have fun!</p>
</div>
<div class="m_2275515528959643236bloop_original_html">
<div id="m_2275515528959643236bloop_customfont" class="" style="font-family: Helvetica, Arial; font-size: 13px; margin: 0px;">
<span class=""><br class=""></span></div>
<span class=""><br class=""></span>
<div id="m_2275515528959643236bloop_sign_1487544005385085184" class="m_2275515528959643236bloop_sign">
<div class="" style="font-family: helvetica, arial; font-size: 13px;"><span class="">-- <br class="">
Adrian Zubarev<br class="">
Sent with Airmail</span></div>
</div>
<span class=""><br class=""></span>
<div class="">
<div class="h5">
<p class="m_2275515528959643236airmail_on" style="margin: 15px 0px;">Am 19. Februar 2017 um 23:25:11, Xiaodi Wu
(<a href="mailto:xiaodi.wu@gmail.com" target="_blank" class="" style="color: rgb(65, 131, 196); background-color: inherit; text-decoration: none;">xiaodi.wu@gmail.com</a>)
schrieb:</p>
<blockquote type="cite" class="m_2275515528959643236clean_bq" style="margin: 15px 0px;">
<div class="" style="margin-top: 0px; margin-bottom: 0px;">
<div class="">
<div dir="ltr" class=""><span class="">Sorry, I have read through
this thread twice and do not understand the point you are making.
Can you explain your example once more?</span>
<div class=""><span class=""><br class=""></span></div>
<div class=""><span class="">Specifically, I do not understand why
it is that your code should have problems with third-party types
that conform to your protocol. If your protocol has requirements
that third-party types cannot fulfill, then naturally those
requirements will prevent a third-party from conforming new types
to your protocol. OTOH, if your protocol does not have any
requirements that third-party types cannot fulfill, then your code
that accepts anything that conforms to your protocol should be
indifferent to whether the conforming type is defined by you or
someone else. After all, a conforming type would fulfill all the
semantic and syntactic requirements of the protocol! If your
protocol has requirements that you are unable to state in code,
causing third-party types to conform that really shouldn't, then
that is a case for additional features that allow you to express
those requirements more accurately, not an argument for having
protocols that can't be conformed to by a third-party. What am I
missing?</span></div>
<div class=""><span class=""><br class=""></span>
<div class="">
<div class="gmail_extra"><span class=""><br class=""></span>
<div class="gmail_quote"><span class="">On Sun, Feb 19, 2017 at
11:53 AM, Adrian Zubarev via swift-evolution<span class="Apple-converted-space"> </span><span dir="ltr" class=""><<a href="mailto:swift-evolution@swift.org" target="_blank" class="" style="color: rgb(65, 131, 196); background-color: inherit; text-decoration: none;">swift-evolution@swift.org</a>></span><span class="Apple-converted-space"> </span>wrote:<br class="">
</span>
<blockquote class="gmail_quote" style="margin: 0px 0px 0px 0.8ex; border-left-width: 1px; border-left-color: rgb(204, 204, 204); border-left-style: solid; padding-left: 1ex;">
<div class="" style="margin-top: 0px; word-wrap: break-word;">
<div id="m_2275515528959643236m_2643987633502928267bloop_customfont" class="" style="font-family: Helvetica, Arial; font-size: 13px; margin: 0px;">
That’s the whole point I was making. :) Thank you Matthew. That
makes my example a real world example and not just some bike
shedding.</div>
<span class=""><br class=""></span>
<div id="m_2275515528959643236m_2643987633502928267bloop_sign_1487526717218961920" class="m_2275515528959643236m_2643987633502928267bloop_sign">
<div class="" style="font-family: helvetica, arial; font-size: 13px;"><span class="">-- <br class="">
Adrian Zubarev<br class="">
Sent with Airmail</span></div>
</div>
<span class=""><br class=""></span>
<div class="">
<div class="m_2275515528959643236h5">
<p class="m_2275515528959643236m_2643987633502928267airmail_on" style="margin: 15px 0px;">Am 19. Februar 2017 um 18:50:31, Matthew
Johnson (<a href="mailto:matthew@anandabits.com" target="_blank" class="" style="color: rgb(65, 131, 196); background-color: inherit; text-decoration: none;">matthew@anandabits.com</a>)
schrieb:</p>
<blockquote type="cite" class="m_2275515528959643236m_2643987633502928267clean_bq" style="margin: 15px 0px;">
<div dir="auto" class="" style="margin-top: 0px; margin-bottom: 0px;">
<div class="">
<div class=""><span class=""><br class="">
<br class="">
Sent from my iPad</span></div>
<div class=""><span class=""><br class="">
On Feb 19, 2017, at 11:29 AM, David Waite via swift-evolution
<<a href="mailto:swift-evolution@swift.org" target="_blank" class="" style="color: rgb(65, 131, 196); background-color: inherit; text-decoration: none;">swift-evolution@swift.org</a>>
wrote:<br class="">
<br class=""></span></div>
<blockquote type="cite" class="" style="margin: 15px 0px;">
<div class="" style="margin-top: 0px; margin-bottom: 0px;">
<span class="">Just FYI, I solved this issue in my own library
(which included a json jpointer implementation) via:</span>
<div class=""><span class=""><span class="" style="font-family: Menlo; font-size: 18px; font-variant-ligatures: no-common-ligatures; color: rgb(196, 34, 117);">
<br class=""></span></span></div>
<div class="" style="font-size: 8px;"><span class="" style="font-family: Menlo; font-size: 13px; font-variant-ligatures: no-common-ligatures; color: rgb(196, 34, 117);">
public</span><span class="Apple-converted-space"> </span><span class="" style="font-family: Menlo; font-size: 13px; font-variant-ligatures: no-common-ligatures; color: rgb(196, 34, 117);">enum</span><span class="Apple-converted-space"> </span><span class="" style="font-family: Menlo; font-size: 13px; font-variant-ligatures: no-common-ligatures;">SubscriptParameter
{</span></div>
<div class="">
<div class="" style="margin: 0px; font-size: 13px; line-height: normal; font-family: Menlo;">
<span class="" style="font-variant-ligatures: no-common-ligatures;"> </span><span class="Apple-converted-space"> </span><span class="" style="font-variant-ligatures: no-common-ligatures; color: rgb(196, 34, 117);">case</span><span class="Apple-converted-space"> </span><span class="" style="font-variant-ligatures: no-common-ligatures;">string(</span><span class="" style="font-variant-ligatures: no-common-ligatures; color: rgb(112, 61, 170);">String</span><span class="" style="font-variant-ligatures: no-common-ligatures;">)</span></div>
<div class="" style="margin: 0px; font-size: 13px; line-height: normal; font-family: Menlo;">
<span class="" style="font-variant-ligatures: no-common-ligatures;"> </span><span class="Apple-converted-space"> </span><span class="" style="font-variant-ligatures: no-common-ligatures; color: rgb(196, 34, 117);">case</span><span class="Apple-converted-space"> </span><span class="" style="font-variant-ligatures: no-common-ligatures;">int(</span><span class="" style="font-variant-ligatures: no-common-ligatures; color: rgb(112, 61, 170);">Int</span><span class="" style="font-variant-ligatures: no-common-ligatures;">)</span></div>
<div class="" style="margin: 0px; font-size: 13px; line-height: normal; font-family: Menlo;">
<span class="" style="font-variant-ligatures: no-common-ligatures;">}</span></div>
<div class="" style="margin: 0px; font-size: 13px; line-height: normal; font-family: Menlo; min-height: 21px;">
<br class=""></div>
<div class="" style="margin: 0px; font-size: 13px; line-height: normal; font-family: Menlo; color: rgb(97, 34, 174);">
<span class="" style="font-variant-ligatures: no-common-ligatures; color: rgb(196, 34, 117);">
extension</span><span class="Apple-converted-space"> </span><span class="" style="font-variant-ligatures: no-common-ligatures; color: rgb(83, 154, 164);">SubscriptParameter</span><span class="Apple-converted-space"> </span><span class="" style="font-variant-ligatures: no-common-ligatures;">:</span><span class="Apple-converted-space"> </span><span class="" style="font-variant-ligatures: no-common-ligatures;">ExpressibleByIntegerLiteral</span><span class="Apple-converted-space"> </span><span class="" style="font-variant-ligatures: no-common-ligatures;">{</span></div>
<div class="" style="margin: 0px; font-size: 13px; line-height: normal; font-family: Menlo;">
<span class="" style="font-variant-ligatures: no-common-ligatures;"> </span><span class="Apple-converted-space"> </span><span class="" style="font-variant-ligatures: no-common-ligatures; color: rgb(196, 34, 117);">public</span><span class="Apple-converted-space"> </span><span class="" style="font-variant-ligatures: no-common-ligatures; color: rgb(196, 34, 117);">init</span><span class="" style="font-variant-ligatures: no-common-ligatures;">(integerLiteral
value:</span><span class="Apple-converted-space"> </span><span class="" style="font-variant-ligatures: no-common-ligatures; color: rgb(112, 61, 170);">Int</span><span class="" style="font-variant-ligatures: no-common-ligatures;">)
{</span></div>
<div class="" style="margin: 0px; font-size: 13px; line-height: normal; font-family: Menlo;">
<span class="" style="font-variant-ligatures: no-common-ligatures;">
</span><span class="Apple-converted-space"> </span><span class="" style="font-variant-ligatures: no-common-ligatures; color: rgb(196, 34, 117);">self</span><span class="Apple-converted-space"> </span><span class="" style="font-variant-ligatures: no-common-ligatures;">=
.</span><span class="" style="font-variant-ligatures: no-common-ligatures; color: rgb(49, 89, 93);">int</span><span class="" style="font-variant-ligatures: no-common-ligatures;">(value)</span></div>
<div class="" style="margin: 0px; font-size: 13px; line-height: normal; font-family: Menlo;">
<span class="" style="font-variant-ligatures: no-common-ligatures;">
}</span></div>
<div class="" style="margin: 0px; font-size: 13px; line-height: normal; font-family: Menlo;">
<span class="" style="font-variant-ligatures: no-common-ligatures;">}</span></div>
<div class="" style="margin: 0px; font-size: 13px; line-height: normal; font-family: Menlo; min-height: 21px;">
<br class=""></div>
<div class="" style="margin: 0px; font-size: 13px; line-height: normal; font-family: Menlo; color: rgb(97, 34, 174);">
<span class="" style="font-variant-ligatures: no-common-ligatures; color: rgb(196, 34, 117);">
extension</span><span class="Apple-converted-space"> </span><span class="" style="font-variant-ligatures: no-common-ligatures; color: rgb(83, 154, 164);">SubscriptParameter</span><span class="Apple-converted-space"> </span><span class="" style="font-variant-ligatures: no-common-ligatures;">:</span><span class="Apple-converted-space"> </span><span class="" style="font-variant-ligatures: no-common-ligatures;">ExpressibleByStringLiteral</span><span class="Apple-converted-space"> </span><span class="" style="font-variant-ligatures: no-common-ligatures;">{</span></div>
<div class="" style="margin: 0px; font-size: 13px; line-height: normal; font-family: Menlo; color: rgb(33, 150, 28);">
<span class="" style="font-variant-ligatures: no-common-ligatures;"> </span><span class="" style="font-variant-ligatures: no-common-ligatures; color: rgb(196, 34, 117);">public</span><span class="Apple-converted-space"> </span><span class="" style="font-variant-ligatures: no-common-ligatures; color: rgb(196, 34, 117);">init</span><span class="" style="font-variant-ligatures: no-common-ligatures;">(stringLiteral
value:</span><span class="Apple-converted-space"> </span><span class="" style="font-variant-ligatures: no-common-ligatures; color: rgb(112, 61, 170);">String</span><span class="" style="font-variant-ligatures: no-common-ligatures;">)
{</span></div>
<div class="" style="margin: 0px; font-size: 13px; line-height: normal; font-family: Menlo;">
<span class="" style="font-variant-ligatures: no-common-ligatures;">
</span><span class="Apple-converted-space"> </span><span class="" style="font-variant-ligatures: no-common-ligatures; color: rgb(196, 34, 117);">self</span><span class="Apple-converted-space"> </span><span class="" style="font-variant-ligatures: no-common-ligatures;">=
.</span><span class="" style="font-variant-ligatures: no-common-ligatures; color: rgb(49, 89, 93);">string</span><span class="" style="font-variant-ligatures: no-common-ligatures;">(value)</span></div>
<div class="" style="margin: 0px; font-size: 13px; line-height: normal; font-family: Menlo;">
<span class="" style="font-variant-ligatures: no-common-ligatures;">
}</span></div>
<div class="" style="margin: 0px; font-size: 13px; line-height: normal; font-family: Menlo;">
<span class="" style="font-variant-ligatures: no-common-ligatures;"> </span><span class="Apple-converted-space"> </span><span class="" style="font-variant-ligatures: no-common-ligatures; color: rgb(196, 34, 117);">public</span><span class="Apple-converted-space"> </span><span class="" style="font-variant-ligatures: no-common-ligatures; color: rgb(196, 34, 117);">init</span><span class="" style="font-variant-ligatures: no-common-ligatures;">(extendedGraphemeClusterLi<wbr class="">teral
value:</span><span class="Apple-converted-space"> </span><span class="" style="font-variant-ligatures: no-common-ligatures; color: rgb(112, 61, 170);">String</span><span class="" style="font-variant-ligatures: no-common-ligatures;">)
{</span></div>
<div class="" style="margin: 0px; font-size: 13px; line-height: normal; font-family: Menlo;">
<span class="" style="font-variant-ligatures: no-common-ligatures;">
</span><span class="Apple-converted-space"> </span><span class="" style="font-variant-ligatures: no-common-ligatures; color: rgb(196, 34, 117);">self</span><span class="" style="font-variant-ligatures: no-common-ligatures;">.</span><span class="" style="font-variant-ligatures: no-common-ligatures; color: rgb(196, 34, 117);">init</span><span class="" style="font-variant-ligatures: no-common-ligatures;">(stringLiteral:
value)</span></div>
<div class="" style="margin: 0px; font-size: 13px; line-height: normal; font-family: Menlo;">
<span class="" style="font-variant-ligatures: no-common-ligatures;">
}</span></div>
<div class="" style="margin: 0px; font-size: 13px; line-height: normal; font-family: Menlo; min-height: 21px;">
<span class="" style="font-variant-ligatures: no-common-ligatures;"> </span><span class="" style="font-variant-ligatures: no-common-ligatures; color: rgb(196, 34, 117);">public</span><span class="Apple-converted-space"> </span><span class="" style="font-variant-ligatures: no-common-ligatures; color: rgb(196, 34, 117);">init</span><span class="" style="font-variant-ligatures: no-common-ligatures;">(unicodeScalarLiteral
value:</span><span class="Apple-converted-space"> </span><span class="" style="font-variant-ligatures: no-common-ligatures; color: rgb(112, 61, 170);">String</span><span class="" style="font-variant-ligatures: no-common-ligatures;">)
{</span></div>
<div class="" style="margin: 0px; font-size: 13px; line-height: normal; font-family: Menlo;">
<span class="" style="font-variant-ligatures: no-common-ligatures;">
</span><span class="Apple-converted-space"> </span><span class="" style="font-variant-ligatures: no-common-ligatures; color: rgb(196, 34, 117);">self</span><span class="" style="font-variant-ligatures: no-common-ligatures;">.</span><span class="" style="font-variant-ligatures: no-common-ligatures; color: rgb(196, 34, 117);">init</span><span class="" style="font-variant-ligatures: no-common-ligatures;">(stringLiteral:
value)</span></div>
<div class="" style="margin: 0px; font-size: 13px; line-height: normal; font-family: Menlo;">
<span class="" style="font-variant-ligatures: no-common-ligatures;">
}</span></div>
<div class="" style="margin: 0px; font-size: 13px; line-height: normal; font-family: Menlo;">
<span class="" style="font-variant-ligatures: no-common-ligatures;">}</span></div>
<div class="" style="margin: 0px; font-size: 13px; line-height: normal; font-family: Menlo; min-height: 21px;">
<br class=""></div>
<div class="" style="margin: 0px; font-size: 13px; line-height: normal; font-family: Menlo; color: rgb(97, 34, 174);">
<span class="" style="font-variant-ligatures: no-common-ligatures; color: rgb(196, 34, 117);">
extension</span><span class="Apple-converted-space"> </span><span class="" style="font-variant-ligatures: no-common-ligatures; color: rgb(83, 154, 164);">SubscriptParameter</span><span class="Apple-converted-space"> </span><span class="" style="font-variant-ligatures: no-common-ligatures;">:</span><span class="Apple-converted-space"> </span><span class="" style="font-variant-ligatures: no-common-ligatures;">CustomStringConvertible</span><span class="Apple-converted-space"> </span><span class="" style="font-variant-ligatures: no-common-ligatures;">{</span></div>
<div class="" style="margin: 0px; font-size: 13px; line-height: normal; font-family: Menlo;">
<span class="" style="font-variant-ligatures: no-common-ligatures;"> </span><span class="Apple-converted-space"> </span><span class="" style="font-variant-ligatures: no-common-ligatures; color: rgb(196, 34, 117);">public</span><span class="Apple-converted-space"> </span><span class="" style="font-variant-ligatures: no-common-ligatures; color: rgb(196, 34, 117);">var</span><span class="Apple-converted-space"> </span><span class="" style="font-variant-ligatures: no-common-ligatures;">description:</span><span class="Apple-converted-space"> </span><span class="" style="font-variant-ligatures: no-common-ligatures; color: rgb(112, 61, 170);">String</span><span class="Apple-converted-space"> </span><span class="" style="font-variant-ligatures: no-common-ligatures;">{</span></div>
<div class="" style="margin: 0px; font-size: 13px; line-height: normal; font-family: Menlo; color: rgb(196, 34, 117);">
<span class="" style="font-variant-ligatures: no-common-ligatures;">
</span><span class="Apple-converted-space"> </span><span class="" style="font-variant-ligatures: no-common-ligatures;">switch</span><span class="Apple-converted-space"> </span><span class="" style="font-variant-ligatures: no-common-ligatures;">self</span><span class="Apple-converted-space"> </span><span class="" style="font-variant-ligatures: no-common-ligatures;">{</span></div>
<div class="" style="margin: 0px; font-size: 13px; line-height: normal; font-family: Menlo;">
<span class="" style="font-variant-ligatures: no-common-ligatures;">
</span><span class="Apple-converted-space"> </span><span class="" style="font-variant-ligatures: no-common-ligatures; color: rgb(196, 34, 117);">case</span><span class="Apple-converted-space"> </span><span class="" style="font-variant-ligatures: no-common-ligatures;">.</span><span class="" style="font-variant-ligatures: no-common-ligatures; color: rgb(49, 89, 93);">string</span><span class="" style="font-variant-ligatures: no-common-ligatures;">(let
str):</span></div>
<div class="" style="margin: 0px; font-size: 13px; line-height: normal; font-family: Menlo;">
<span class="" style="font-variant-ligatures: no-common-ligatures;">
</span><span class="Apple-converted-space"> </span><span class="" style="font-variant-ligatures: no-common-ligatures; color: rgb(196, 34, 117);">return</span><span class="Apple-converted-space"> </span><span class="" style="font-variant-ligatures: no-common-ligatures; color: rgb(200, 27, 19);">"\"</span><span class="" style="font-variant-ligatures: no-common-ligatures;">\</span><span class="" style="font-variant-ligatures: no-common-ligatures; color: rgb(200, 27, 19);">(</span><span class="" style="font-variant-ligatures: no-common-ligatures;">str</span><span class="" style="font-variant-ligatures: no-common-ligatures; color: rgb(200, 27, 19);">)\""</span></div>
<div class="" style="margin: 0px; font-size: 13px; line-height: normal; font-family: Menlo;">
<span class="" style="font-variant-ligatures: no-common-ligatures;">
</span><span class="Apple-converted-space"> </span><span class="" style="font-variant-ligatures: no-common-ligatures; color: rgb(196, 34, 117);">case</span><span class="Apple-converted-space"> </span><span class="" style="font-variant-ligatures: no-common-ligatures;">.</span><span class="" style="font-variant-ligatures: no-common-ligatures; color: rgb(49, 89, 93);">int</span><span class="" style="font-variant-ligatures: no-common-ligatures;">(let
i):</span></div>
<div class="" style="margin: 0px; font-size: 13px; line-height: normal; font-family: Menlo;">
<span class="" style="font-variant-ligatures: no-common-ligatures;">
</span><span class="Apple-converted-space"> </span><span class="" style="font-variant-ligatures: no-common-ligatures; color: rgb(196, 34, 117);">return</span><span class="Apple-converted-space"> </span><span class="" style="font-variant-ligatures: no-common-ligatures; color: rgb(112, 61, 170);">String</span><span class="" style="font-variant-ligatures: no-common-ligatures;">(i)</span></div>
<div class="" style="margin: 0px; font-size: 13px; line-height: normal; font-family: Menlo;">
<span class="" style="font-variant-ligatures: no-common-ligatures;">
}</span></div>
<div class="" style="margin: 0px; font-size: 13px; line-height: normal; font-family: Menlo;">
<span class="" style="font-variant-ligatures: no-common-ligatures;">
}</span></div>
<div class="" style="margin: 0px; font-size: 13px; line-height: normal; font-family: Menlo;">
<span class="" style="font-variant-ligatures: no-common-ligatures;">}</span></div>
<div class="" style="margin: 0px; font-size: 13px; line-height: normal; font-family: Menlo; min-height: 21px;">
<br class=""></div>
<div class="" style="margin: 0px; font-size: 13px; line-height: normal; font-family: Menlo;">
<span class="" style="font-variant-ligatures: no-common-ligatures; color: rgb(196, 34, 117);">
func</span><span class="Apple-converted-space"> </span><span class="" style="font-variant-ligatures: no-common-ligatures;">debug(</span><span class="" style="font-variant-ligatures: no-common-ligatures; color: rgb(196, 34, 117);">_</span><span class="Apple-converted-space"> </span><span class="" style="font-variant-ligatures: no-common-ligatures;">path:</span><span class="" style="font-variant-ligatures: no-common-ligatures; color: rgb(83, 154, 164);">SubscriptParameter</span><span class="" style="font-variant-ligatures: no-common-ligatures;">...)
{</span></div>
<div class="" style="margin: 0px; font-size: 13px; line-height: normal; font-family: Menlo; color: rgb(200, 27, 19);">
<span class="" style="font-variant-ligatures: no-common-ligatures;"> </span><span class="Apple-converted-space"> </span><span class="" style="font-variant-ligatures: no-common-ligatures; color: rgb(62, 30, 129);">print</span><span class="" style="font-variant-ligatures: no-common-ligatures;">(</span><span class="" style="font-variant-ligatures: no-common-ligatures;">"path
is</span><span class="Apple-converted-space"> </span><span class="" style="font-variant-ligatures: no-common-ligatures;">\</span><span class="" style="font-variant-ligatures: no-common-ligatures;">(</span><span class="" style="font-variant-ligatures: no-common-ligatures;">path</span><span class="" style="font-variant-ligatures: no-common-ligatures;">)"</span><span class="" style="font-variant-ligatures: no-common-ligatures;">)</span></div>
<div class="" style="margin: 0px; font-size: 13px; line-height: normal; font-family: Menlo;">
<span class="" style="font-variant-ligatures: no-common-ligatures;">}</span></div>
<div class="" style="margin: 0px; font-size: 13px; line-height: normal; font-family: Menlo; min-height: 21px;">
<br class=""></div>
<div class="" style="margin: 0px; font-size: 13px; line-height: normal; font-family: Menlo; color: rgb(200, 27, 19);">
<span class="" style="font-variant-ligatures: no-common-ligatures; color: rgb(41, 76, 80);">
debug</span><span class="" style="font-variant-ligatures: no-common-ligatures;">(</span><span class="" style="font-variant-ligatures: no-common-ligatures; color: rgb(4, 53, 255);">1</span><span class="" style="font-variant-ligatures: no-common-ligatures;">,</span><span class="Apple-converted-space"> </span><span class="" style="font-variant-ligatures: no-common-ligatures;">"foo"</span><span class="" style="font-variant-ligatures: no-common-ligatures;">,</span><span class="Apple-converted-space"> </span><span class="" style="font-variant-ligatures: no-common-ligatures; color: rgb(4, 53, 255);">2</span><span class="" style="font-variant-ligatures: no-common-ligatures;">,</span><span class="Apple-converted-space"> </span><span class="" style="font-variant-ligatures: no-common-ligatures;">"bar”</span><span class="" style="font-variant-ligatures: no-common-ligatures;">) // path is
[1, “foo”, 2, “bar”]</span></div>
</div>
</div>
</blockquote>
<div class=""><br class=""></div>
Can you make this work with variables - not just literals - and
still prevent users from extending the set of types and without
requiring an enum case constructor to be used by clients?
<div class=""><br class="">
<div class=""><br class="">
<blockquote type="cite" class="" style="margin: 15px 0px;">
<div class="" style="margin-top: 0px; margin-bottom: 0px;">
<div class="">
<div class=""><br class=""></div>
<div class="">
<div class="">
<blockquote type="cite" class="" style="margin: 15px 0px;">
<div class="" style="margin-top: 0px;">On Feb 19, 2017, at 1:14 AM,
Adrian Zubarev <<a href="mailto:adrian.zubarev@devandartist.com" target="_blank" class="" style="color: rgb(65, 131, 196); background-color: inherit; text-decoration: none;">adrian.zubarev@devandartist.c<wbr class="">om</a>>
wrote:</div>
<br class="m_2275515528959643236m_2643987633502928267Apple-interchange-newline">
<div class="" style="margin-bottom: 0px;">
<div class="m_2275515528959643236m_2643987633502928267bloop_markdown" style="font-family: Helvetica, Arial; font-size: 13px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; background-color: rgb(254, 254, 254);">
<p class="" style="margin: 15px 0px;">If you haven’t followed the
other thread Matthew previously opened than you have missed the
example I showed there.</p>
<p class="" style="margin: 15px 0px;">Here it is again:</p>
<pre class="" style="margin: 15px 0px; font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(204, 204, 204); overflow: auto; padding: 4px 8px; word-break: normal; word-wrap: normal;"><code class="m_2275515528959643236m_2643987633502928267swift" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 0px; margin: 0px; padding: 0px; word-break: normal; word-wrap: normal;">public protocol SubscriptParameterType {
// This property was needed to prevent the client from breaking
// the library by conforming to the protocol, but I'd like to
// keep it invisible for the client, or even better prevent the
// client from conforming to the protocol.
var parameter: Document.SubscriptParameter { get }
}
extension Document {
public enum SubscriptParameter {
case string(String)
case integer(Int)
}
}
extension String : SubscriptParameterType {
public var parameter: Document.SubscriptParameter {
return .string(self)
}
}
extension Int : SubscriptParameterType {
public var parameter: Document.SubscriptParameter {
return .integer(self)
}
}
// Somewhere inside the `Document` type
public subscript(firstKey: String, parameters: SubscriptParameterType...) -> Value? { … }
</code></pre>
<p class="" style="margin: 15px 0px;">The absence of closed
protocols forced me to create a special requirement on that
protocol to prevent the client from conforming to that protocol and
passing instances of other types my API wouldn’t want to deal with.
That creates unnecessary copies and I need to unpack the enum
payload to find out which type the user passed. Instead I could
simply close the protocol, wouldn’t need the requirement to exist
and I could simply cast the type to<span class="m_2275515528959643236m_2643987633502928267Apple-converted-space"> </span><code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;">String</code><span class="m_2275515528959643236m_2643987633502928267Apple-converted-space"> </span>or<span class="m_2275515528959643236m_2643987633502928267Apple-converted-space"> </span><code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;">Int</code><span class="m_2275515528959643236m_2643987633502928267Apple-converted-space"> </span>when
needed.</p>
<p class="" style="margin: 15px 0px;">That implementation enables
more safe queries of my Document type like</p>
<p class="" style="margin: 15px 0px;"><code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;">
document["key1", intIndexInstance, stringKeyInstance, 10,
"key"]</code></p>
<p class="" style="margin: 15px 0px;">rather than<span class="m_2275515528959643236m_2643987633502928267Apple-converted-space"> </span></p>
<p class="" style="margin: 15px 0px;"><code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;">
document["key1/\(intIndexInsta<wbr class="">nce)/\(stringKeyInstance)/10/<wbr class="">key"]</code>.</p>
<hr class="" style="height: 0.2em; border: 0px; color: rgb(204, 204, 204); background-color: rgb(204, 204, 204); display: inherit;">
<p class="" style="margin: 15px 0px;">Here is a list of hidden and
semi-hidden protocols from the standard library that could be
closed. Formatted version:<span class="m_2275515528959643236m_2643987633502928267Apple-converted-space"> </span><a href="https://gist.github.com/DevAndArtist/168c800d784829be536c407311953ab7" target="_blank" class="" style="color: rgb(65, 131, 196); background-color: inherit; text-decoration: none;">https://gist.github.c<wbr class="">om/DevAndArtist/168c800d784829<wbr class="">be536c407311953ab7</a></p>
<table class="" style="margin: 15px 0px; border-collapse: collapse; font-family: Helvetica, arial, freesans, clean, sans-serif; color: rgb(51, 51, 51); font-size: 15px; line-height: 25px; padding: 0px;">
<colgroup class="">
<col class="" style="text-align: left;">
<col class="" style="text-align: center;"></colgroup>
<thead class="">
<tr class="" style="border-top-width: 1px; border-top-style: solid; border-top-color: rgb(204, 204, 204); background-color: white; margin: 0px; padding: 0px;">
<th class="" style="font-weight: bold; border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: left;">
Path</th>
<th class="" style="font-weight: bold; border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: center;">
Protocol</th>
</tr>
</thead>
<tbody class="">
<tr class="" style="border-top-width: 1px; border-top-style: solid; border-top-color: rgb(204, 204, 204); background-color: white; margin: 0px; padding: 0px;">
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: left;">
/swift/stdlib/public/core/AnyH<wbr class="">ashable.swift:16</td>
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: center;">
<code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;">
_HasCustomAnyHashableRepresent<wbr class="">ation</code></td>
</tr>
<tr class="" style="border-top-width: 1px; border-top-style: solid; border-top-color: rgb(204, 204, 204); background-color: rgb(248, 248, 248); margin: 0px; padding: 0px;">
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: left;">
/swift/stdlib/public/core/Bidi<wbr class="">rectionalCollection.swift:21</td>
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: center;">
<code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;">
_BidirectionalIndexable</code></td>
</tr>
<tr class="" style="border-top-width: 1px; border-top-style: solid; border-top-color: rgb(204, 204, 204); background-color: white; margin: 0px; padding: 0px;">
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: left;">
/swift/stdlib/public/core/Brid<wbr class="">geObjectiveC.swift:19</td>
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: center;">
<code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;">
_ObjectiveCBridgeable</code></td>
</tr>
<tr class="" style="border-top-width: 1px; border-top-style: solid; border-top-color: rgb(204, 204, 204); background-color: rgb(248, 248, 248); margin: 0px; padding: 0px;">
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: left;">
/swift/stdlib/public/core/Coll<wbr class="">ection.swift:20</td>
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: center;">
<code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;">
_IndexableBase</code></td>
</tr>
<tr class="" style="border-top-width: 1px; border-top-style: solid; border-top-color: rgb(204, 204, 204); background-color: white; margin: 0px; padding: 0px;">
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: left;">
/swift/stdlib/public/core/Coll<wbr class="">ection.swift:176</td>
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: center;">
<code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;">
_Indexable</code></td>
</tr>
<tr class="" style="border-top-width: 1px; border-top-style: solid; border-top-color: rgb(204, 204, 204); background-color: rgb(248, 248, 248); margin: 0px; padding: 0px;">
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: left;">
/swift/stdlib/public/core/Comp<wbr class="">ilerProtocols.swift:193</td>
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: center;">
<code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;">
_ExpressibleByBuiltinIntegerLi<wbr class="">teral</code></td>
</tr>
<tr class="" style="border-top-width: 1px; border-top-style: solid; border-top-color: rgb(204, 204, 204); background-color: white; margin: 0px; padding: 0px;">
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: left;">
/swift/stdlib/public/core/Comp<wbr class="">ilerProtocols.swift:240</td>
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: center;">
<code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;">
_ExpressibleByBuiltinFloatLite<wbr class="">ral</code></td>
</tr>
<tr class="" style="border-top-width: 1px; border-top-style: solid; border-top-color: rgb(204, 204, 204); background-color: rgb(248, 248, 248); margin: 0px; padding: 0px;">
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: left;">
/swift/stdlib/public/core/Comp<wbr class="">ilerProtocols.swift:283</td>
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: center;">
<code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;">
_ExpressibleByBuiltinBooleanLi<wbr class="">teral</code></td>
</tr>
<tr class="" style="border-top-width: 1px; border-top-style: solid; border-top-color: rgb(204, 204, 204); background-color: white; margin: 0px; padding: 0px;">
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: left;">
/swift/stdlib/public/core/Comp<wbr class="">ilerProtocols.swift:316</td>
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: center;">
<code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;">
_ExpressibleByBuiltinUnicodeSc<wbr class="">alarLiteral</code></td>
</tr>
<tr class="" style="border-top-width: 1px; border-top-style: solid; border-top-color: rgb(204, 204, 204); background-color: rgb(248, 248, 248); margin: 0px; padding: 0px;">
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: left;">
/swift/stdlib/public/core/Comp<wbr class="">ilerProtocols.swift:350</td>
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: center;">
<code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;">
_ExpressibleByBuiltinExtendedG<wbr class="">raphemeClusterLiteral</code></td>
</tr>
<tr class="" style="border-top-width: 1px; border-top-style: solid; border-top-color: rgb(204, 204, 204); background-color: white; margin: 0px; padding: 0px;">
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: left;">
/swift/stdlib/public/core/Comp<wbr class="">ilerProtocols.swift:398</td>
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: center;">
<code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;">
_ExpressibleByBuiltinStringLit<wbr class="">eral</code></td>
</tr>
<tr class="" style="border-top-width: 1px; border-top-style: solid; border-top-color: rgb(204, 204, 204); background-color: rgb(248, 248, 248); margin: 0px; padding: 0px;">
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: left;">
/swift/stdlib/public/core/Comp<wbr class="">ilerProtocols.swift:407</td>
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: center;">
<code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;">
_ExpressibleByBuiltinUTF16Stri<wbr class="">ngLiteral</code></td>
</tr>
<tr class="" style="border-top-width: 1px; border-top-style: solid; border-top-color: rgb(204, 204, 204); background-color: white; margin: 0px; padding: 0px;">
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: left;">
/swift/stdlib/public/core/Comp<wbr class="">ilerProtocols.swift:670</td>
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: center;">
<code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;">
_ExpressibleByStringInterpolat<wbr class="">ion</code></td>
</tr>
<tr class="" style="border-top-width: 1px; border-top-style: solid; border-top-color: rgb(204, 204, 204); background-color: rgb(248, 248, 248); margin: 0px; padding: 0px;">
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: left;">
/swift/stdlib/public/core/Comp<wbr class="">ilerProtocols.swift:709</td>
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: center;">
<code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;">
_ExpressibleByColorLiteral</code></td>
</tr>
<tr class="" style="border-top-width: 1px; border-top-style: solid; border-top-color: rgb(204, 204, 204); background-color: white; margin: 0px; padding: 0px;">
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: left;">
/swift/stdlib/public/core/Comp<wbr class="">ilerProtocols.swift:720</td>
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: center;">
<code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;">
_ExpressibleByImageLiteral</code></td>
</tr>
<tr class="" style="border-top-width: 1px; border-top-style: solid; border-top-color: rgb(204, 204, 204); background-color: rgb(248, 248, 248); margin: 0px; padding: 0px;">
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: left;">
/swift/stdlib/public/core/Comp<wbr class="">ilerProtocols.swift:730</td>
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: center;">
<code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;">
_ExpressibleByFileReferenceLit<wbr class="">eral</code></td>
</tr>
<tr class="" style="border-top-width: 1px; border-top-style: solid; border-top-color: rgb(204, 204, 204); background-color: white; margin: 0px; padding: 0px;">
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: left;">
/swift/stdlib/public/core/Comp<wbr class="">ilerProtocols.swift:750</td>
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: center;">
<code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;">
_DestructorSafeContainer</code></td>
</tr>
<tr class="" style="border-top-width: 1px; border-top-style: solid; border-top-color: rgb(204, 204, 204); background-color: rgb(248, 248, 248); margin: 0px; padding: 0px;">
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: left;">
/swift/stdlib/public/core/Fixe<wbr class="">dPoint.swift.gyb:53</td>
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: center;">
<code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;">
_Integer</code></td>
</tr>
<tr class="" style="border-top-width: 1px; border-top-style: solid; border-top-color: rgb(204, 204, 204); background-color: white; margin: 0px; padding: 0px;">
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: left;">
/swift/stdlib/public/core/Fixe<wbr class="">dPoint.swift.gyb:70</td>
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: center;">
<code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;">
_SignedInteger</code></td>
</tr>
<tr class="" style="border-top-width: 1px; border-top-style: solid; border-top-color: rgb(204, 204, 204); background-color: rgb(248, 248, 248); margin: 0px; padding: 0px;">
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: left;">
/swift/stdlib/public/core/Fixe<wbr class="">dPoint.swift.gyb:108</td>
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: center;">
<code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;">
_DisallowMixedSignArithmetic</code></td>
</tr>
<tr class="" style="border-top-width: 1px; border-top-style: solid; border-top-color: rgb(204, 204, 204); background-color: white; margin: 0px; padding: 0px;">
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: left;">
/swift/stdlib/public/core/Hash<wbr class="">able.swift:16</td>
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: center;">
<code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;">
_Hashable</code></td>
</tr>
<tr class="" style="border-top-width: 1px; border-top-style: solid; border-top-color: rgb(204, 204, 204); background-color: rgb(248, 248, 248); margin: 0px; padding: 0px;">
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: left;">
/swift/stdlib/public/core/Inde<wbr class="">x.swift:16</td>
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: center;">
<code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;">
_Incrementable</code></td>
</tr>
<tr class="" style="border-top-width: 1px; border-top-style: solid; border-top-color: rgb(204, 204, 204); background-color: white; margin: 0px; padding: 0px;">
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: left;">
/swift/stdlib/public/core/Inte<wbr class="">gerArithmetic.swift.gyb:33</td>
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: center;">
<code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;">
_IntegerArithmetic</code></td>
</tr>
<tr class="" style="border-top-width: 1px; border-top-style: solid; border-top-color: rgb(204, 204, 204); background-color: rgb(248, 248, 248); margin: 0px; padding: 0px;">
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: left;">
/swift/stdlib/public/core/Mirr<wbr class="">or.swift:721</td>
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: center;">
<code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;">
_DefaultCustomPlaygroundQuickL<wbr class="">ookable</code></td>
</tr>
<tr class="" style="border-top-width: 1px; border-top-style: solid; border-top-color: rgb(204, 204, 204); background-color: white; margin: 0px; padding: 0px;">
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: left;">
/swift/stdlib/public/core/Muta<wbr class="">bleCollection.swift:20</td>
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: center;">
<code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;">
_MutableIndexable</code></td>
</tr>
<tr class="" style="border-top-width: 1px; border-top-style: solid; border-top-color: rgb(204, 204, 204); background-color: rgb(248, 248, 248); margin: 0px; padding: 0px;">
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: left;">
/swift/stdlib/public/core/Newt<wbr class="">ypeWrapper.swift.gyb:16</td>
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: center;">
<code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;">
_SwiftNewtypeWrapper</code></td>
</tr>
<tr class="" style="border-top-width: 1px; border-top-style: solid; border-top-color: rgb(204, 204, 204); background-color: white; margin: 0px; padding: 0px;">
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: left;">
/swift/stdlib/public/core/Poin<wbr class="">ter.swift:16</td>
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: center;">
<code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;">
_Pointer</code></td>
</tr>
<tr class="" style="border-top-width: 1px; border-top-style: solid; border-top-color: rgb(204, 204, 204); background-color: rgb(248, 248, 248); margin: 0px; padding: 0px;">
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: left;">
/swift/stdlib/public/core/Rand<wbr class="">omAccessCollection.swift:20</td>
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: center;">
<code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;">
_RandomAccessIndexable</code></td>
</tr>
<tr class="" style="border-top-width: 1px; border-top-style: solid; border-top-color: rgb(204, 204, 204); background-color: white; margin: 0px; padding: 0px;">
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: left;">
/swift/stdlib/public/core/Rang<wbr class="">eReplaceableCollection.swift.<wbr class="">gyb:27</td>
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: center;">
<code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;">
_RangeReplaceableIndexable</code></td>
</tr>
<tr class="" style="border-top-width: 1px; border-top-style: solid; border-top-color: rgb(204, 204, 204); background-color: rgb(248, 248, 248); margin: 0px; padding: 0px;">
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: left;">
/swift/stdlib/public/core/Refl<wbr class="">ectionLegacy.swift:41</td>
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: center;">
<code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;">
_Mirror</code></td>
</tr>
<tr class="" style="border-top-width: 1px; border-top-style: solid; border-top-color: rgb(204, 204, 204); background-color: white; margin: 0px; padding: 0px;">
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: left;">
/swift/stdlib/public/core/Shad<wbr class="">owProtocols.swift:27</td>
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: center;">
<code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;">
_ShadowProtocol</code></td>
</tr>
<tr class="" style="border-top-width: 1px; border-top-style: solid; border-top-color: rgb(204, 204, 204); background-color: rgb(248, 248, 248); margin: 0px; padding: 0px;">
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: left;">
/swift/stdlib/public/core/Shad<wbr class="">owProtocols.swift:31</td>
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: center;">
<code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;">
_NSFastEnumeration</code></td>
</tr>
<tr class="" style="border-top-width: 1px; border-top-style: solid; border-top-color: rgb(204, 204, 204); background-color: white; margin: 0px; padding: 0px;">
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: left;">
/swift/stdlib/public/core/Shad<wbr class="">owProtocols.swift:41</td>
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: center;">
<code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;">
_NSEnumerator</code></td>
</tr>
<tr class="" style="border-top-width: 1px; border-top-style: solid; border-top-color: rgb(204, 204, 204); background-color: rgb(248, 248, 248); margin: 0px; padding: 0px;">
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: left;">
/swift/stdlib/public/core/Shad<wbr class="">owProtocols.swift:51</td>
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: center;">
<code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;">
_NSCopying</code></td>
</tr>
<tr class="" style="border-top-width: 1px; border-top-style: solid; border-top-color: rgb(204, 204, 204); background-color: white; margin: 0px; padding: 0px;">
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: left;">
/swift/stdlib/public/core/Shad<wbr class="">owProtocols.swift:61</td>
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: center;">
<code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;">
_NSArrayCore</code></td>
</tr>
<tr class="" style="border-top-width: 1px; border-top-style: solid; border-top-color: rgb(204, 204, 204); background-color: rgb(248, 248, 248); margin: 0px; padding: 0px;">
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: left;">
/swift/stdlib/public/core/Shad<wbr class="">owProtocols.swift:83</td>
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: center;">
<code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;">
_NSDictionaryCore</code></td>
</tr>
<tr class="" style="border-top-width: 1px; border-top-style: solid; border-top-color: rgb(204, 204, 204); background-color: white; margin: 0px; padding: 0px;">
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: left;">
/swift/stdlib/public/core/Shad<wbr class="">owProtocols.swift:125</td>
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: center;">
<code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;">
_NSDictionary</code></td>
</tr>
<tr class="" style="border-top-width: 1px; border-top-style: solid; border-top-color: rgb(204, 204, 204); background-color: rgb(248, 248, 248); margin: 0px; padding: 0px;">
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: left;">
/swift/stdlib/public/core/Shad<wbr class="">owProtocols.swift:137</td>
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: center;">
<code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;">
_NSSetCore</code></td>
</tr>
<tr class="" style="border-top-width: 1px; border-top-style: solid; border-top-color: rgb(204, 204, 204); background-color: white; margin: 0px; padding: 0px;">
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: left;">
/swift/stdlib/public/core/Shad<wbr class="">owProtocols.swift:171</td>
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: center;">
<code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;">
_NSSet</code></td>
</tr>
<tr class="" style="border-top-width: 1px; border-top-style: solid; border-top-color: rgb(204, 204, 204); background-color: rgb(248, 248, 248); margin: 0px; padding: 0px;">
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: left;">
/swift/stdlib/public/core/Shad<wbr class="">owProtocols.swift:177</td>
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: center;">
<code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;">
_NSNumber</code></td>
</tr>
<tr class="" style="border-top-width: 1px; border-top-style: solid; border-top-color: rgb(204, 204, 204); background-color: white; margin: 0px; padding: 0px;">
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: left;">
/swift/stdlib/public/core/Shad<wbr class="">owProtocols.swift:187</td>
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: center;">
<code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;">
_NSArrayCore</code></td>
</tr>
<tr class="" style="border-top-width: 1px; border-top-style: solid; border-top-color: rgb(204, 204, 204); background-color: rgb(248, 248, 248); margin: 0px; padding: 0px;">
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: left;">
/swift/stdlib/public/core/Shad<wbr class="">owProtocols.swift:188</td>
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: center;">
<code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;">
_NSDictionaryCore</code></td>
</tr>
<tr class="" style="border-top-width: 1px; border-top-style: solid; border-top-color: rgb(204, 204, 204); background-color: white; margin: 0px; padding: 0px;">
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: left;">
/swift/stdlib/public/core/Shad<wbr class="">owProtocols.swift:189</td>
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: center;">
<code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;">
_NSSetCore</code></td>
</tr>
<tr class="" style="border-top-width: 1px; border-top-style: solid; border-top-color: rgb(204, 204, 204); background-color: rgb(248, 248, 248); margin: 0px; padding: 0px;">
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: left;">
/swift/stdlib/public/core/Stri<wbr class="">ngBridge.swift:194</td>
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: center;">
<code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;">
_NSStringCore</code></td>
</tr>
<tr class="" style="border-top-width: 1px; border-top-style: solid; border-top-color: rgb(204, 204, 204); background-color: white; margin: 0px; padding: 0px;">
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: left;">
/swift/stdlib/public/SDK/Found<wbr class="">ation/NSError.swift:353</td>
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: center;">
<code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;">
_ObjectiveCBridgeableError</code></td>
</tr>
<tr class="" style="border-top-width: 1px; border-top-style: solid; border-top-color: rgb(204, 204, 204); background-color: rgb(248, 248, 248); margin: 0px; padding: 0px;">
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: left;">
/swift/stdlib/public/SDK/Found<wbr class="">ation/NSError.swift:379</td>
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: center;">
<code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;">
__BridgedNSError</code></td>
</tr>
<tr class="" style="border-top-width: 1px; border-top-style: solid; border-top-color: rgb(204, 204, 204); background-color: white; margin: 0px; padding: 0px;">
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: left;">
/swift/stdlib/public/SDK/Found<wbr class="">ation/NSError.swift:446</td>
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: center;">
<code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;">
_BridgedNSError</code></td>
</tr>
<tr class="" style="border-top-width: 1px; border-top-style: solid; border-top-color: rgb(204, 204, 204); background-color: rgb(248, 248, 248); margin: 0px; padding: 0px;">
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: left;">
/swift/stdlib/public/SDK/Found<wbr class="">ation/NSError.swift:456</td>
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: center;">
<code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;">
_BridgedStoredNSError</code></td>
</tr>
<tr class="" style="border-top-width: 1px; border-top-style: solid; border-top-color: rgb(204, 204, 204); background-color: white; margin: 0px; padding: 0px;">
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: left;">
/swift/stdlib/public/SDK/Found<wbr class="">ation/NSError.swift:564</td>
<td class="" style="border: 1px solid rgb(204, 204, 204); margin: 0px; padding: 6px 13px; text-align: center;">
<code class="" style="font-family: Menlo, Consolas, 'Liberation Mono', Courier, monospace; font-size: 10pt; border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; background-color: rgb(248, 248, 248); color: inherit; border: 1px solid rgb(234, 234, 234); margin: 0px 2px; padding: 0px 5px; word-break: normal; word-wrap: normal;">
_ErrorCodeProtocol</code></td>
</tr>
</tbody>
</table>
<div class="" style="margin: 15px 0px;"><br class="m_2275515528959643236m_2643987633502928267webkit-block-placeholder">
</div>
</div>
<div class="m_2275515528959643236m_2643987633502928267bloop_original_html" style="font-family: Helvetica, Arial; font-size: 13px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; background-color: rgb(254, 254, 254);">
<div id="m_2275515528959643236m_2643987633502928267bloop_customfont" class="" style="font-family: Helvetica, Arial; font-size: 13px; margin: 0px;">
<br class=""></div>
<br class="">
<div id="m_2275515528959643236m_2643987633502928267bloop_sign_1487490659060471040" class="m_2275515528959643236m_2643987633502928267bloop_sign">
<div class="" style="font-family: helvetica, arial; font-size: 13px;">
-- <br class="">
Adrian Zubarev<br class="">
Sent with Airmail</div>
</div>
<br class="">
<p class="m_2275515528959643236m_2643987633502928267airmail_on" style="margin: 15px 0px;">Am 19. Februar 2017 um 07:59:45, David
Waite via swift-evolution (<a href="mailto:swift-evolution@swift.org" target="_blank" class="" style="color: rgb(65, 131, 196); background-color: inherit; text-decoration: none;">swift-evolution@swift.org</a>)
schrieb:</p>
<blockquote type="cite" class="m_2275515528959643236m_2643987633502928267clean_bq" style="margin: 15px 0px;">
<div class="" style="margin-top: 0px; margin-bottom: 0px;">
<div class=""><span class="" style="margin-top: 0px; margin-bottom: 0px;">I am unsure if this feature
is a good idea. Does someone have a real-world use for this which
isn’t just hiding strong implementation coupling behind a
protocol?<br class="">
<br class="">
When I consume a protocol, it is under the assumption that the
protocol is documented such that I would be able to work against
*any* implementation of the protocol. With a closed protocol, I
would have to assume that there are significant side effects,
either undocumented or difficult for a third party to duplicate. To
my experience, that sounds brittle.<br class="">
<br class="">
Assuming you aren’t switching on the implementing type of a
protocol (which itself can be a sign that your design isn’t
properly using polymorphism), one could get this design by creating
a struct with the interface desired, and passing invocations
through to an internal protocol reference.<br class="">
<br class="">
-DW<br class="">
<br class="">
> On Feb 18, 2017, at 1:41 PM, Matthew Johnson via
swift-evolution <<a href="mailto:swift-evolution@swift.org" target="_blank" class="" style="color: rgb(65, 131, 196); background-color: inherit; text-decoration: none;">swift-evolution@swift.org</a>>
wrote:<br class="">
><span class="m_2275515528959643236m_2643987633502928267Apple-converted-space"> </span><br class="">
> Now that we’re in phase 2 I’d like to officially propose we
introduce `open` protocols and require conformances to `public`
protocols be inside the declaring module. Let’s use this thread for
feedback on the official proposal. After a healthy round of
discussion I’ll open a PR to submit it for review.<br class="">
><span class="m_2275515528959643236m_2643987633502928267Apple-converted-space"> </span><br class="">
><span class="m_2275515528959643236m_2643987633502928267Apple-converted-space"> </span><br class="">
> # Feature name<br class="">
><span class="m_2275515528959643236m_2643987633502928267Apple-converted-space"> </span><br class="">
> * Proposal: [SE-NNNN](NNNN-open-public-<a href="http://protocols.md/" target="_blank" class="" style="color: rgb(65, 131, 196); background-color: inherit; text-decoration: none;">pro<wbr class="">tocols.md</a>)<br class="">
> * Authors: [Matthew Johnson](<a href="https://github.com/anandabits" target="_blank" class="" style="color: rgb(65, 131, 196); background-color: inherit; text-decoration: none;">https://github.com/an<wbr class="">andabits</a>)<br class="">
> * Review Manager: TBD<br class="">
> * Status: **Awaiting review**<br class="">
><span class="m_2275515528959643236m_2643987633502928267Apple-converted-space"> </span><br class="">
> ## Introduction<br class="">
><span class="m_2275515528959643236m_2643987633502928267Apple-converted-space"> </span><br class="">
> This proposal introduces `open protocol` and changes the
meaning of `public protocol` to match the meaning of `public class`
(in this case, conformances are only allowed inside the declaring
module).<br class="">
><span class="m_2275515528959643236m_2643987633502928267Apple-converted-space"> </span><br class="">
> The pitch thread leading up to this proposal was: [consistent
public access modifiers](<a href="https://lists.swift.org/pipermail/swift-evolution/Week-of-Mon-20170206/031653.html" target="_blank" class="" style="color: rgb(65, 131, 196); background-color: inherit; text-decoration: none;">https://lists.swift<wbr class="">.org/pipermail/swift-evolution<wbr class="">/Week-of-Mon-20170206/031653.<wbr class="">html</a>)<br class="">
><span class="m_2275515528959643236m_2643987633502928267Apple-converted-space"> </span><br class="">
> ## Motivation<br class="">
><span class="m_2275515528959643236m_2643987633502928267Apple-converted-space"> </span><br class="">
> A general principle the Swift community has adopted for access
control is that defaults should reserve maximum flexibility for a
library. The ensures that any capabilities beyond mere visibility
are not available unless the author of the library has explicitly
declared their intent that the capabilities be made available.
Finally, when it is possible to switch from one semantic to another
without breaking clients (but not vice-versa) we should prefer the
more forgiving (i.e. fixable) semantic as the (soft)
default.<br class="">
><span class="m_2275515528959643236m_2643987633502928267Apple-converted-space"> </span><br class="">
> `public` is considered a "soft default" in the sense that it
is the first access modifier a user will reach for when exposing a
declaration outside of the module. In the case of protocols the
current meaning of `public` does not meet the principle of
preserving maximum flexibility for the author of the library. It
allows users of the library to conform to the protocol.<br class="">
><span class="m_2275515528959643236m_2643987633502928267Apple-converted-space"> </span><br class="">
> There are good reasons a library may not wish to allow users
to add conformances to a protocol. For example, it may not wish to
expose the conforming concrete types. While similar behavior could
be accomplished with an enum if cases could be private, that
requires an implementation to use switch statements rather than
polymorphism.<br class="">
><span class="m_2275515528959643236m_2643987633502928267Apple-converted-space"> </span><br class="">
> Even if all the conforming types are also public there are
cases where polymorphism is the preferred implementation. For
example, if the set of conforming types is not expected to be fixed
(despite all being inside the library) the authors may not want to
have to maintain switch statements every time they need to add or
remove a confroming type which would be necessary if an enum were
used instead. Polymorphism allows us to avoid this, giving us the
ability to add and remove conforming types within the
implementation of the library without the burden of maintaining
switch statements.<br class="">
><span class="m_2275515528959643236m_2643987633502928267Apple-converted-space"> </span><br class="">
> Aligning the access modifiers for protocols and classes allows
us to specify both conformable and non-conformable protocols,
provides a soft default that is consistent with the principle of
(soft) defaults reserving maximum flexibility for the library, and
increases the overall consistency of the language by aligning the
semantics of access control for protocols and classes.<br class="">
><span class="m_2275515528959643236m_2643987633502928267Apple-converted-space"> </span><br class="">
> The standard library currently has at least one protocol
(`MirrorPath`) that is documented as disallowing client
conformances. If this proposal is adopted it is likely that
`MirrorPath` would be declared `public protocol` and not `open
protocol`.<br class="">
><span class="m_2275515528959643236m_2643987633502928267Apple-converted-space"> </span><br class="">
> Jordan Rose has indicated that the Apple frameworks also
include a number of protocols documented with the intent that users
do not add conformances. Perhaps an importer annotation would allow
the compiler to enforce these semantics in Swift code as
well.<br class="">
><span class="m_2275515528959643236m_2643987633502928267Apple-converted-space"> </span><br class="">
> ## Proposed solution<br class="">
><span class="m_2275515528959643236m_2643987633502928267Apple-converted-space"> </span><br class="">
> The proposed solution is to change the meaning of `public
protocol` to disallow conformances outside the declaring module and
introduce `open protocol` to allow conformances outside the
decalring module (equivalent to the current meaning of `public
protocol`).<br class="">
><span class="m_2275515528959643236m_2643987633502928267Apple-converted-space"> </span><br class="">
> ## Detailed design<br class="">
><span class="m_2275515528959643236m_2643987633502928267Apple-converted-space"> </span><br class="">
> The detailed design is relatively straightforward but there
are three important wrinkles to consider.<br class="">
><span class="m_2275515528959643236m_2643987633502928267Apple-converted-space"> </span><br class="">
> ### User refinement of public protocols<br class="">
><span class="m_2275515528959643236m_2643987633502928267Apple-converted-space"> </span><br class="">
> Consider the following example:<br class="">
><span class="m_2275515528959643236m_2643987633502928267Apple-converted-space"> </span><br class="">
> ```swift<br class="">
> // Library module:<br class="">
> public protocol P {}<br class="">
> public class C: P {}<br class="">
><span class="m_2275515528959643236m_2643987633502928267Apple-converted-space"> </span><br class="">
> // User module:<br class="">
> protocol User: P {}<br class="">
> extension C: User {}<br class="">
> ```<br class="">
><span class="m_2275515528959643236m_2643987633502928267Apple-converted-space"> </span><br class="">
> The user module is allowed to add a refinement to `P` because
this does not have any impact on the impelementation of the library
or its possible evolution. It simply allows the user to write code
that is generic over a subset of the conforming types provided by
the library.<br class="">
><span class="m_2275515528959643236m_2643987633502928267Apple-converted-space"> </span><br class="">
> ### Public protocols with open conforming classes<br class="">
><span class="m_2275515528959643236m_2643987633502928267Apple-converted-space"> </span><br class="">
> Consider the following example:<br class="">
><span class="m_2275515528959643236m_2643987633502928267Apple-converted-space"> </span><br class="">
> ```swift<br class="">
> public protocol P P{}<br class="">
> open class C: P {}<br class="">
> ```<br class="">
><span class="m_2275515528959643236m_2643987633502928267Apple-converted-space"> </span><br class="">
> Users of this module will be able to add subclasses of `C`
that have a conformance to `P`. This is allowed becuase the client
of the module did not need to explicitly declare a conformance and
the module has explicitly stated its intent to allow subclasses of
`C` with the `open` access modifier.<br class="">
><span class="m_2275515528959643236m_2643987633502928267Apple-converted-space"> </span><br class="">
> ### Open protocols that refine public protocols<br class="">
><span class="m_2275515528959643236m_2643987633502928267Apple-converted-space"> </span><br class="">
> Consider the following example:<br class="">
><span class="m_2275515528959643236m_2643987633502928267Apple-converted-space"> </span><br class="">
> ```swift<br class="">
> // library module:<br class="">
> public protocol P {}<br class="">
> open protocol Q: P {}<br class="">
> open protocol R: P {}<br class="">
><span class="m_2275515528959643236m_2643987633502928267Apple-converted-space"> </span><br class="">
> // user module:<br class="">
> struct S: P {} // error `P` is not `open`<br class="">
> struct T: Q {} // ok<br class="">
> struct U: R {} // ok<br class="">
> ```<br class="">
><span class="m_2275515528959643236m_2643987633502928267Apple-converted-space"> </span><br class="">
> The user module is allowed to introudce a conformance to `P`,
but only indirectly by also conforming to `Q`. The meaning we have
ascribed to the keywords implies that this should be allowed and it
offers libraries a very wide design space from which to choose. The
library is able to have types that conform directly to `P`, while
placing additional requirements on user types if
necessary.<br class="">
><span class="m_2275515528959643236m_2643987633502928267Apple-converted-space"> </span><br class="">
> ## Source compatibility<br class="">
><span class="m_2275515528959643236m_2643987633502928267Apple-converted-space"> </span><br class="">
> This proposal breaks source compatibility, but in a way that
allows for a simple mechanical migration. A multi-release stratgegy
will be used to roll out this proposal to provide maximum possible
source compatibility from one release to the next.<br class="">
><span class="m_2275515528959643236m_2643987633502928267Apple-converted-space"> </span><br class="">
> 1. In Swift 4, introduce the `open` keyword and the `@nonopen`
attribute (which can be applied to `public protocol` to give it the
new semantics of `public`).<br class="">
> 2. In Swift 4 (or 4.1 if necessary) start warning for `public
protocol` with no annotation.<br class="">
> 3. In the subsequent release `public protocol` without
annotation becomes an error.<br class="">
> 4. In the subsequent relase `public protocol` without
annotation takes on the new semantics.<br class="">
> 5. `@nonopen` becomes a warning, and evenutally an erro as
soon as we are comfortable making those changes.<br class="">
><span class="m_2275515528959643236m_2643987633502928267Apple-converted-space"> </span><br class="">
> ## Effect on ABI stability<br class="">
><span class="m_2275515528959643236m_2643987633502928267Apple-converted-space"> </span><br class="">
> I would appreciate it if others can offer input regarding this
section. I believe this proposal has ABI consequences, but it's
possible that it could be an additivie ABI change where the ABI for
conformable protocols remains the same and we add ABI for
non-conformable protocols later. If that is possible, the primary
impact would be the ABI of any standard library protocols that
would prefer to be non-conformable.<br class="">
><span class="m_2275515528959643236m_2643987633502928267Apple-converted-space"> </span><br class="">
> ## Effect on API resilience<br class="">
><span class="m_2275515528959643236m_2643987633502928267Apple-converted-space"> </span><br class="">
> This proposal would may impact one or more protocols in the
standard library, such as `MirrorPath`, which would likely choose
to remain `public` rather than adopt `open`.<br class="">
><span class="m_2275515528959643236m_2643987633502928267Apple-converted-space"> </span><br class="">
> ## Alternatives considered<br class="">
><span class="m_2275515528959643236m_2643987633502928267Apple-converted-space"> </span><br class="">
> The primary alternatives are to either make no change, or to
add something like `closed protocol`. The issues motivating the
current proposal as a better alternative than either of these
options are covered in the motivation section.<br class="">
><span class="m_2275515528959643236m_2643987633502928267Apple-converted-space"> </span><br class="">
> ______________________________<wbr class="">_________________<br class="">
> swift-evolution mailing list<br class="">
><span class="Apple-converted-space"> </span><a href="mailto:swift-evolution@swift.org" target="_blank" class="" style="color: rgb(65, 131, 196); background-color: inherit; text-decoration: none;">swift-evolution@swift.org</a><br class="">
><span class="Apple-converted-space"> </span><a href="https://lists.swift.org/mailman/listinfo/swift-evolution" target="_blank" class="" style="color: rgb(65, 131, 196); background-color: inherit; text-decoration: none;">https://lists.swift.org/mailma<wbr class="">n/listinfo/swift-evolution</a><br class="">
<br class="">
______________________________<wbr class="">_________________<br class="">
swift-evolution mailing list<br class="">
<a href="mailto:swift-evolution@swift.org" target="_blank" class="" style="color: rgb(65, 131, 196); background-color: inherit; text-decoration: none;">
swift-evolution@swift.org</a><br class="">
<a href="https://lists.swift.org/mailman/listinfo/swift-evolution" target="_blank" class="" style="color: rgb(65, 131, 196); background-color: inherit; text-decoration: none;">
https://lists.swift.org/mailma<wbr class="">n/listinfo/swift-evolution</a><br class=""></span></div>
</div>
</blockquote>
</div>
<div class="m_2275515528959643236m_2643987633502928267bloop_markdown" style="font-family: Helvetica, Arial; font-size: 13px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; background-color: rgb(254, 254, 254);">
</div>
</div>
</blockquote>
</div>
<br class=""></div>
</div>
</div>
</blockquote>
<blockquote type="cite" class="" style="margin: 15px 0px;">
<div class="" style="margin-top: 0px; margin-bottom: 0px;">
<span class="">______________________________<wbr class="">_________________</span><br class="">
<span class="">swift-evolution mailing list</span><br class="">
<span class=""><a href="mailto:swift-evolution@swift.org" target="_blank" class="" style="color: rgb(65, 131, 196); background-color: inherit; text-decoration: none;">
swift-evolution@swift.org</a></span><br class="">
<span class=""><a href="https://lists.swift.org/mailman/listinfo/swift-evolution" target="_blank" class="" style="color: rgb(65, 131, 196); background-color: inherit; text-decoration: none;">
https://lists.swift.org/mailma<wbr class="">n/listinfo/swift-evolution</a></span><br class=""></div>
</blockquote>
</div>
</div>
</div>
</div>
</blockquote>
</div>
</div>
</div>
<br class="">
______________________________<wbr class="">_________________<br class="">
swift-evolution mailing list<br class="">
<a href="mailto:swift-evolution@swift.org" target="_blank" class="" style="color: rgb(65, 131, 196); background-color: inherit; text-decoration: none;">
swift-evolution@swift.org</a><br class="">
<a href="https://lists.swift.org/mailman/listinfo/swift-evolution" rel="noreferrer" target="_blank" class="" style="color: rgb(65, 131, 196); background-color: inherit; text-decoration: none;">
https://lists.swift.org/mailma<wbr class="">n/listinfo/swift-evolution</a><br class="">
<br class="" style="margin-bottom: 0px;"></blockquote>
</div>
<br class=""></div>
</div>
</div>
</div>
</div>
</div>
</blockquote>
</div>
</div>
</div>
<div class="m_2275515528959643236bloop_markdown"></div>
</div>
</blockquote>
</div>
<br class=""></div>
</div>
</div>
</div>
</blockquote>
</div>
<div class="bloop_markdown" style="font-family: Helvetica, Arial; font-size: 13px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(254, 254, 254);">
<div class="" style="-webkit-margin-before: 0px; margin: 15px 0px;"><br class="webkit-block-placeholder" style="-webkit-margin-before: 0px;"></div>
</div>
<span class="" style="font-family: Helvetica, Arial; font-size: 13px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(254, 254, 254); float: none; display: inline !important;">_______________________________________________</span><br class="" style="font-family: Helvetica, Arial; font-size: 13px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(254, 254, 254);">
<span class="" style="font-family: Helvetica, Arial; font-size: 13px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(254, 254, 254); float: none; display: inline !important;">
swift-evolution mailing list</span><br class="" style="font-family: Helvetica, Arial; font-size: 13px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(254, 254, 254);">
<a href="mailto:swift-evolution@swift.org" class="" style="color: rgb(65, 131, 196); background-color: rgb(254, 254, 254); text-decoration: none; font-family: Helvetica, Arial; font-size: 13px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;">
swift-evolution@swift.org</a><br class="" style="font-family: Helvetica, Arial; font-size: 13px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(254, 254, 254);">
<a href="https://lists.swift.org/mailman/listinfo/swift-evolution" class="" style="color: rgb(65, 131, 196); background-color: rgb(254, 254, 254); text-decoration: none; font-family: Helvetica, Arial; font-size: 13px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;">
https://lists.swift.org/mailman/listinfo/swift-evolution</a><br class="" style="font-family: Helvetica, Arial; font-size: 13px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(254, 254, 254);">
</div>
</blockquote>
</div>
<br class=""></div>
</div>
</blockquote>
</div>
<div class="bloop_markdown" style="font-family: Helvetica, Arial; font-size: 13px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(254, 254, 254);">
<br class="Apple-interchange-newline"></div>
</div>
</blockquote>
</div>
<br class="">
</div></div></span></blockquote></body></html>