<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><br class=""><div><blockquote type="cite" class=""><div class="">Le 9 mars 2016 à 12:40, David Hart via swift-evolution <<a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a>> a écrit :</div><br class="Apple-interchange-newline"><div class=""><meta http-equiv="content-type" content="text/html; charset=utf-8" class=""><div dir="auto" class=""><div class=""><span class=""></span></div><div class=""><div class=""><span class=""></span></div><div class=""><div class="">You would at least need #} to disambiguate. With your proposal:</div><div class=""><br class=""></div><div class="">#if FALSE {</div><div class="">if false {</div><div class="">}</div><div class="">print("hello")</div><div class="">#if FALSE {</div><div class="">}</div><div class="">}</div><div class=""><br class=""></div><div class="">This either:</div><div class="">• is invalid syntax</div><div class="">• prints hello</div><div class="">• does nothing</div></div></div></div></div></blockquote><div><br class=""></div>Swift required the block in compiler directive to be syntactically correct. So, you can’t have a dandling "{" and so that sample should not introduced ambiguity.</div><div><br class=""><blockquote type="cite" class=""><div class=""><div dir="auto" class=""><div class=""><div class=""><div class=""><div class="">Sent from my iPhone</div>On 09 Mar 2016, at 02:22, Félix Cloutier via swift-evolution <<a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a>> wrote:<br class=""><br class=""></div><blockquote type="cite" class=""><div class=""><meta http-equiv="Content-Type" content="text/html charset=utf-8" class="">I don't think that this change can be implemented at all. `#if swift` doesn't parse inactive branches, so you wouldn't be able to disambiguate an `#if swift` end brace from a normal end brace.<br class=""><div class="">
<br class="Apple-interchange-newline"><span style="font-family: 'Lucida Grande'; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;" class="">Félix</span>
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<br class=""><div class=""><blockquote type="cite" class=""><div class="">Le 8 mars 2016 à 19:33:49, Richard Ross via swift-evolution <<a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a>> a écrit :</div><br class="Apple-interchange-newline"><div class=""><span style="font-family: Menlo-Regular; font-size: 10px; font-style: normal; font-variant: 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; float: none; display: inline !important;" class="">-1. Keeping it the current way makes it significantly more obvious where the conditional compilation ends, rather than having to scour for yet another pesky curly brace.</span><br style="font-family: Menlo-Regular; font-size: 10px; font-style: normal; font-variant: 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;" class=""><br style="font-family: Menlo-Regular; font-size: 10px; font-style: normal; font-variant: 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;" class=""><span style="font-family: Menlo-Regular; font-size: 10px; font-style: normal; font-variant: 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; float: none; display: inline !important;" class="">Additionally, some of us are logical and prefer not to use conditional compilation as an extra indentation level :)</span><br style="font-family: Menlo-Regular; font-size: 10px; font-style: normal; font-variant: 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;" class=""><span style="font-family: Menlo-Regular; font-size: 10px; font-style: normal; font-variant: 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; float: none; display: inline !important;" class="">--</span><br style="font-family: Menlo-Regular; font-size: 10px; font-style: normal; font-variant: 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;" class=""><span style="font-family: Menlo-Regular; font-size: 10px; font-style: normal; font-variant: 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; float: none; display: inline !important;" class="">Richard</span><br style="font-family: Menlo-Regular; font-size: 10px; font-style: normal; font-variant: 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;" class=""><br style="font-family: Menlo-Regular; font-size: 10px; font-style: normal; font-variant: 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;" class=""><blockquote type="cite" style="font-family: Menlo-Regular; font-size: 10px; font-style: normal; font-variant: 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;" class="">On Mar 8, 2016, at 4:23 PM, Brent Royal-Gordon via swift-evolution <<a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a>> wrote:<br class=""><br class="">Swift inherited an odd preprocessor-related inconsistency from C, and I'm wondering if we should change it.<br class=""><br class="">Swift and C both use curly-bracket blocks to delimit if statements and other runtime control flow:<br class=""><br class=""><span class="Apple-tab-span" style="white-space: pre;"> </span>if foo {<br class=""><span class="Apple-tab-span" style="white-space: pre;"> </span><span class="Apple-tab-span" style="white-space: pre;"> </span>blah<br class=""><span class="Apple-tab-span" style="white-space: pre;"> </span>}<br class=""><span class="Apple-tab-span" style="white-space: pre;"> </span>else {<br class=""><span class="Apple-tab-span" style="white-space: pre;"> </span><span class="Apple-tab-span" style="white-space: pre;"> </span>yadda<br class=""><span class="Apple-tab-span" style="white-space: pre;"> </span>}<br class=""><br class="">However, the preprocessor/build configuration equivalent uses keywords in the style of languages like BASIC:<br class=""><br class=""><span class="Apple-tab-span" style="white-space: pre;"> </span>#if FOO<br class=""><span class="Apple-tab-span" style="white-space: pre;"> </span><span class="Apple-tab-span" style="white-space: pre;"> </span>blah<br class=""><span class="Apple-tab-span" style="white-space: pre;"> </span>#else<br class=""><span class="Apple-tab-span" style="white-space: pre;"> </span><span class="Apple-tab-span" style="white-space: pre;"> </span>blah<br class=""><span class="Apple-tab-span" style="white-space: pre;"> </span>#endif<br class=""><br class="">In addition to the inconsistency, I consider this to have several concrete disadvantages:<br class=""><br class="">- It leaves the preferred indentation of a conditional block ambiguous. Some people indent, others don't.<br class="">- It gives us no syntax to build on for other things that should be "scoped". For instance, clang's `#pragma clang diagnostic push/pop` is as strange as it is because there's no sensible way to delimit a block structure.<br class=""><br class="">C justifies this because the preprocessor is a separate pass with its own rules, but Swift does not have this limitation.<br class=""><br class="">Therefore, I suggest we switch to this syntax:<br class=""><br class=""><span class="Apple-tab-span" style="white-space: pre;"> </span>#if FOO {<br class=""><span class="Apple-tab-span" style="white-space: pre;"> </span><span class="Apple-tab-span" style="white-space: pre;"> </span>blah<br class=""><span class="Apple-tab-span" style="white-space: pre;"> </span>}<br class=""><span class="Apple-tab-span" style="white-space: pre;"> </span>#else {<br class=""><span class="Apple-tab-span" style="white-space: pre;"> </span><span class="Apple-tab-span" style="white-space: pre;"> </span>blah<br class=""><span class="Apple-tab-span" style="white-space: pre;"> </span>}<br class=""><br class="">That gives us a basis to cleanly extend compiler directives to add new features. For instance, the #suppress directive discussed in the "[Idea] #suppress(warning-identifier)" could be given a syntax like this:<br class=""><br class=""><span class="Apple-tab-span" style="white-space: pre;"> </span>#suppress self-in-closure {<br class=""><span class="Apple-tab-span" style="white-space: pre;"> </span><span class="Apple-tab-span" style="white-space: pre;"> </span>blah<br class=""><span class="Apple-tab-span" style="white-space: pre;"> </span>}<br class=""><br class="">If their design ends up being purely compile-time with no runtime impact, we might even consider using this syntax for behaviors:<br class=""><br class=""><span class="Apple-tab-span" style="white-space: pre;"> </span>#behavior var lazy<Value>: Value {<br class=""><span class="Apple-tab-span" style="white-space: pre;"> </span><span class="Apple-tab-span" style="white-space: pre;"> </span>private var value: Value?<br class=""><span class="Apple-tab-span" style="white-space: pre;"> </span><span class="Apple-tab-span" style="white-space: pre;"> </span><br class=""><span class="Apple-tab-span" style="white-space: pre;"> </span><span class="Apple-tab-span" style="white-space: pre;"> </span>get {<br class=""><span class="Apple-tab-span" style="white-space: pre;"> </span><span class="Apple-tab-span" style="white-space: pre;"> </span><span class="Apple-tab-span" style="white-space: pre;"> </span>if let value = value {<br class=""><span class="Apple-tab-span" style="white-space: pre;"> </span><span class="Apple-tab-span" style="white-space: pre;"> </span><span class="Apple-tab-span" style="white-space: pre;"> </span><span class="Apple-tab-span" style="white-space: pre;"> </span>return value<br class=""><span class="Apple-tab-span" style="white-space: pre;"> </span><span class="Apple-tab-span" style="white-space: pre;"> </span><span class="Apple-tab-span" style="white-space: pre;"> </span>}<br class=""><span class="Apple-tab-span" style="white-space: pre;"> </span><span class="Apple-tab-span" style="white-space: pre;"> </span><span class="Apple-tab-span" style="white-space: pre;"> </span>let newValue = initialValue<br class=""><span class="Apple-tab-span" style="white-space: pre;"> </span><span class="Apple-tab-span" style="white-space: pre;"> </span><span class="Apple-tab-span" style="white-space: pre;"> </span>value = newValue<br class=""><span class="Apple-tab-span" style="white-space: pre;"> </span><span class="Apple-tab-span" style="white-space: pre;"> </span><span class="Apple-tab-span" style="white-space: pre;"> </span>return newValue<br class=""><span class="Apple-tab-span" style="white-space: pre;"> </span><span class="Apple-tab-span" style="white-space: pre;"> </span>}<br class=""><span class="Apple-tab-span" style="white-space: pre;"> </span><span class="Apple-tab-span" style="white-space: pre;"> </span>set {<br class=""><span class="Apple-tab-span" style="white-space: pre;"> </span><span class="Apple-tab-span" style="white-space: pre;"> </span><span class="Apple-tab-span" style="white-space: pre;"> </span>value = newValue<br class=""><span class="Apple-tab-span" style="white-space: pre;"> </span><span class="Apple-tab-span" style="white-space: pre;"> </span>}<br class=""><span class="Apple-tab-span" style="white-space: pre;"> </span>}<br class=""><br class="">There are two disadvantages I can identify:<br class=""><br class="">- The fact that a particular } is associated with a compiler directive may not be immediately obvious when reading code.<br class=""><br class="">- `#if swift(...)` may not be able to correctly parse the close of the block if unrecognized new language features inside the block appear to unbalance the curly brackets. (For instance, if a new literal syntax is used to quote a closing curly and older Swift compilers don't recognize it.)<br class=""><br class="">If these problems are considered serious enough, an alternative would be to use `#}` to indicate the close of the compiler directive's scope. This is obviously not an ordinary curly bracket and is unlikely to appear in source for any other reason.<br class=""><br class="">--<span class="Apple-converted-space"> </span><br class="">Brent Royal-Gordon<br class="">Architechies<br class=""><br class="">_______________________________________________<br class="">swift-evolution mailing list<br class=""><a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a><br class=""><a href="https://urldefense.proofpoint.com/v2/url?u=https-3A__lists.swift.org_mailman_listinfo_swift-2Devolution&d=CwIGaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=Ezje1IF3xGXfUMfsj4fBc7oM7BcJys1dhQ6psfXzLMU&m=KpVD5NRN240WmQvnHJitBkkgyBtlHU87STAlrcfVNSA&s=V6Bvu749V2ofSYff-m5YKMX_g5Yr48jKkjCeBANWe4w&e=" class="">https://urldefense.proofpoint.com/v2/url?u=https-3A__lists.swift.org_mailman_listinfo_swift-2Devolution&d=CwIGaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=Ezje1IF3xGXfUMfsj4fBc7oM7BcJys1dhQ6psfXzLMU&m=KpVD5NRN240WmQvnHJitBkkgyBtlHU87STAlrcfVNSA&s=V6Bvu749V2ofSYff-m5YKMX_g5Yr48jKkjCeBANWe4w&e=</a><span class="Apple-converted-space"> </span><br class=""></blockquote><br style="font-family: Menlo-Regular; font-size: 10px; font-style: normal; font-variant: 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;" class=""><span style="font-family: Menlo-Regular; font-size: 10px; font-style: normal; font-variant: 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; float: none; display: inline !important;" class="">_______________________________________________</span><br style="font-family: Menlo-Regular; font-size: 10px; font-style: normal; font-variant: 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;" class=""><span style="font-family: Menlo-Regular; font-size: 10px; font-style: normal; font-variant: 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; float: none; display: inline !important;" class="">swift-evolution mailing list</span><br style="font-family: Menlo-Regular; font-size: 10px; font-style: normal; font-variant: 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;" class=""><a href="mailto:swift-evolution@swift.org" style="font-family: Menlo-Regular; font-size: 10px; font-style: normal; font-variant: 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;" class="">swift-evolution@swift.org</a><br style="font-family: Menlo-Regular; font-size: 10px; font-style: normal; font-variant: 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;" class=""><a href="https://lists.swift.org/mailman/listinfo/swift-evolution" style="font-family: Menlo-Regular; font-size: 10px; font-style: normal; font-variant: 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;" class="">https://lists.swift.org/mailman/listinfo/swift-evolution</a></div></blockquote></div><br class=""></div></blockquote><blockquote type="cite" class=""><div class=""><span class="">_______________________________________________</span><br class=""><span class="">swift-evolution mailing list</span><br class=""><span class=""><a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a></span><br class=""><span class=""><a href="https://lists.swift.org/mailman/listinfo/swift-evolution" class="">https://lists.swift.org/mailman/listinfo/swift-evolution</a></span><br class=""></div></blockquote></div></div></div>_______________________________________________<br class="">swift-evolution mailing list<br class=""><a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a><br class="">https://lists.swift.org/mailman/listinfo/swift-evolution<br class=""></div></blockquote></div><br class=""></body></html>