<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=""><div><blockquote type="cite" class=""><div class="">On Dec 27, 2015, at 4:02 PM, Chris Lattner via swift-evolution <<a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a>> wrote:</div><div class=""><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">On Dec 27, 2015, at 10:37 AM, Joe Groff via swift-evolution <<a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a>> wrote:<div class=""><blockquote type="cite" class=""><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div class=""><blockquote type="cite" class=""><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div class=""><ul style="box-sizing: border-box; padding: 0px 0px 0px 2em; margin-top: 0px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; background-color: rgb(255, 255, 255); margin-bottom: 0px !important;" class=""><li style="box-sizing: border-box;" class=""><p style="box-sizing: border-box; margin-top: 16px; margin-bottom: 16px;" class="">can be correctly parsed as a reference to <code style="box-sizing: border-box; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; padding: 0.2em 0px; margin: 0px; background-color: rgba(0, 0, 0, 0.0392157); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px;" class="">insertSubview(_:at:)</code>. However, it breaks down at the margins, e.g., with getter/setter references or no-argument functions:</p><div class="highlight highlight-source-swift" style="box-sizing: border-box; margin-bottom: 16px;"><pre style="box-sizing: border-box; overflow: auto; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 14px; margin-top: 0px; margin-bottom: 0px; line-height: 1.45; padding: 16px; background-color: rgb(247, 247, 247); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; word-wrap: normal; word-break: normal;" class=""><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">extension</span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">Optional</span> {
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">func</span> <span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">get</span>() <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">-></span> T { <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">return</span> <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">self</span><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">!</span> }
}
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">let</span> fn1 <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">=</span> button<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>currentTitle<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">get</span> <span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">// getter or Optional<String>.get?</span>
<span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">let</span> fn2 <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">=</span> <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">set</span><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">.</span>removeAllElements() <span class="pl-c" style="box-sizing: border-box; color: rgb(150, 152, 150);">// call or reference?</span></pre></div></li></ul></div></div></blockquote>From what I remember, the bigger concern with allowing foo(bar:bas:) without backticks is parser error recovery. The unambiguity with call syntax depends on having the `:)` token pair at the end. The edit distance between foo(bar:bas:) and a call foo(bar: bas) or work-in-progress call foo(bar: x, bas: ) is pretty slight, and would be tricky to give good diagnostics for. If we felt confident we could give good diagnostics, I'd support removing the backticks.</div></div></blockquote><br class=""></div><div class="">I’m a fan of good error recovery, but I don’t think it is a major concern here for two reasons:</div><div class=""><br class=""></div><div class="">1) The most common case in a method will lack a label, and "thing.foo(_: “ and “thing.foo(:” are both unambiguously a curried reference.</div><div class="">2) A common case of accidentally completing a nullary call (thing.foo() vs thing.foo) will produce a type error. We already produce good QoI for an unapplied function - adding the inverse would be simple.</div><div class=""><br class=""></div><div class="">Further, it will be uncommon *in general* to form a curried reference, so error recovery doesn’t have to be perfect in all the edge cases. As with other commenters, if it is at all possible to avoid the extra backticks, I’d really prefer that.</div></div></div></blockquote><div><br class=""></div>The concern, I think, is that a messed-up normal call might look like a curried reference.</div><div><br class=""></div><div>My inclination would be to go the other way: if we get a syntax for this that we like, I think we should use it for *all* curried member references, and reject things like foo.bar in favor of foo.`bar`. The ability to write foo.bar for a method has always struck me as more clever than wise, to be honest.</div><div><br class=""></div><div>John.</div></body></html>