<html><head><meta http-equiv="Content-Type" content="text/html charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">The reason this is appearing here before filing a radar is getting a quick feedback as I have been assuming this is the expected behavior but Nate Cook told me otherwise. See this <a href="https://lists.swift.org/pipermail/swift-evolution/Week-of-Mon-20160509/017048.html" class="">thread</a> for the initial discussion that lead to this.<div class=""><br class=""></div><div class="">Run this code to see the issue: (Works with the latest Swift 3.0 snapshot)</div><div class=""><br class=""></div><div class=""><div style="margin: 0px; line-height: normal;" class=""><div style="font-family: Menlo; font-size: 11px; margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">func</span><span style="font-variant-ligatures: no-common-ligatures" class=""> subSequenceIndexBug</span></div><p style="font-family: Menlo; font-size: 11px; margin: 0px; line-height: normal; min-height: 13px;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> </span><br class="webkit-block-placeholder"></p><div style="font-family: Menlo; font-size: 11px; margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> <C: </span><span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">Collection</span></div><div style="font-family: Menlo; font-size: 11px; margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">where</span></div><div style="font-family: Menlo; font-size: 11px; margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">C</span><span style="font-variant-ligatures: no-common-ligatures" class="">.Iterator.Element: </span><span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">Equatable</span><span style="font-variant-ligatures: no-common-ligatures" class="">,</span></div><div style="font-family: Menlo; font-size: 11px; margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">C</span><span style="font-variant-ligatures: no-common-ligatures" class="">.SubSequence: </span><span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">Collection</span><span style="font-variant-ligatures: no-common-ligatures" class="">,</span></div><div style="font-family: Menlo; font-size: 11px; margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">C</span><span style="font-variant-ligatures: no-common-ligatures" class="">.SubSequence.Index == </span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">C</span><span style="font-variant-ligatures: no-common-ligatures" class="">.Index,</span></div><div style="font-family: Menlo; font-size: 11px; margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">C</span><span style="font-variant-ligatures: no-common-ligatures" class="">.SubSequence.Iterator.Element == </span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">C</span><span style="font-variant-ligatures: no-common-ligatures" class="">.Iterator.Element></span></div><p style="font-family: Menlo; font-size: 11px; margin: 0px; line-height: normal; min-height: 13px;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> </span><br class="webkit-block-placeholder"></p><div style="font-family: Menlo; font-size: 11px; margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> (</span><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">_</span><span style="font-variant-ligatures: no-common-ligatures" class=""> c: </span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">C</span><span style="font-variant-ligatures: no-common-ligatures" class="">, </span><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">_</span><span style="font-variant-ligatures: no-common-ligatures" class=""> e: </span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">C</span><span style="font-variant-ligatures: no-common-ligatures" class="">.Iterator.Element)</span></div><div style="font-family: Menlo; font-size: 11px; margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> {</span></div><div style="font-family: Menlo; font-size: 11px; margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">let</span><span style="font-variant-ligatures: no-common-ligatures" class=""> junction = c.</span><span style="font-variant-ligatures: no-common-ligatures; color: #3d1d81" class="">index</span><span style="font-variant-ligatures: no-common-ligatures" class="">(c.</span><span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">startIndex</span><span style="font-variant-ligatures: no-common-ligatures" class="">, offsetBy: </span><span style="font-variant-ligatures: no-common-ligatures; color: #3d1d81" class="">numericCast</span><span style="font-variant-ligatures: no-common-ligatures" class="">(</span><span style="font-variant-ligatures: no-common-ligatures; color: #272ad8" class="">5</span><span style="font-variant-ligatures: no-common-ligatures" class="">)) </span><span style="color: rgb(0, 132, 0);" class="">// Arbitrary split point.</span></div><p style="font-family: Menlo; font-size: 11px; margin: 0px; line-height: normal; min-height: 13px;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> </span><br class="webkit-block-placeholder"></p><div style="font-family: Menlo; font-size: 11px; margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">if</span><span style="font-variant-ligatures: no-common-ligatures" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: #bb2ca2" class="">let</span><span style="font-variant-ligatures: no-common-ligatures" class=""> i = c.</span><span style="font-variant-ligatures: no-common-ligatures; color: #3d1d81" class="">suffix</span><span style="font-variant-ligatures: no-common-ligatures" class="">(from: junction).</span><span style="font-variant-ligatures: no-common-ligatures; color: #3d1d81" class="">index</span><span style="font-variant-ligatures: no-common-ligatures" class="">(of: e) {</span></div><p style="font-family: Menlo; font-size: 11px; margin: 0px; line-height: normal; min-height: 13px;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> </span><br class="webkit-block-placeholder"></p><div style="font-family: Menlo; font-size: 11px; margin: 0px; line-height: normal; color: rgb(209, 47, 27);" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: #3d1d81" class="">print</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">(</span><span style="font-variant-ligatures: no-common-ligatures" class="">"Searched for \"</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">\</span><span style="font-variant-ligatures: no-common-ligatures" class="">(</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">e</span><span style="font-variant-ligatures: no-common-ligatures" class="">)\" and found \"</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">\</span><span style="font-variant-ligatures: no-common-ligatures" class="">(</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">c[i]</span><span style="font-variant-ligatures: no-common-ligatures" class="">)\". Result of testing them for equality is: </span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">\</span><span style="font-variant-ligatures: no-common-ligatures" class="">(</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">e </span><span style="font-variant-ligatures: no-common-ligatures; color: #3d1d81" class="">==</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class=""> c[i]</span><span style="font-variant-ligatures: no-common-ligatures" class="">)"</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">)</span></div><div style="font-family: Menlo; font-size: 11px; margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> }</span></div><div style="font-family: Menlo; font-size: 11px; margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> }</span></div><p style="font-family: Menlo; font-size: 11px; margin: 0px; line-height: normal; min-height: 13px;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> </span><br class="webkit-block-placeholder"></p><div style="font-family: Menlo; font-size: 11px; margin: 0px; line-height: normal; color: rgb(209, 47, 27);" class=""><div style="margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: #31595d" class="">subSequenceIndexBug</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">(</span><span style="font-variant-ligatures: no-common-ligatures" class="">"ABCDEFGHIJKLMNOPQRSTUVWXYZ"</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">.</span><span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">characters</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">, </span><span style="font-variant-ligatures: no-common-ligatures" class="">"Q"</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class="">)</span></div><div style="margin: 0px; line-height: normal; color: rgb(0, 132, 0);" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class=""> </span><span style="font-variant-ligatures: no-common-ligatures" class="">// Prints: "Searched for "Q" and found "L". Result of testing them for equality is: false</span>"</div><div style="margin: 0px; line-height: normal; color: rgb(0, 132, 0);" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""><br class=""></span></div><div style="margin: 0px; line-height: normal; color: rgb(0, 132, 0);" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""><div style="color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px;" class="">Is this a generics design limitation, my bug, or a compiler bug?</div><div style="color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px;" class=""><br class=""></div><div style="color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px;" class="">Thanks for your,</div><div style="color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px;" class="">Hooman</div><div class=""><br class=""></div></span></div></div></div></div></body></html>