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<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">Hi,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">It appears that VC11's STL has found a bug in clang. 
<a href="https://connect.microsoft.com/VisualStudio/feedback/details/747847/type-deduction-fail">
https://connect.microsoft.com/VisualStudio/feedback/details/747847/type-deduction-fail</a> says "This code is simplified one from clang project and you can get the same error trying to compile clang using vc110."  (They didn't mention where the offending code
 was, but it should be easy enough to find.)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">The issue is that when A has a user-defined conversion to B and B has a user-defined conversion to C, C++03/VC10 permits pair<A, X> to be converted (explicitly or implicitly)
 to pair<C, X>, while C++11/VC11 forbids this because A is not implicitly convertible to C.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">Presumably, this also indicates that libc++ hasn't constrained its pair (and tuple!) as specified by C++11.  So, two bugs for the price of one.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">Stephan T. Lavavej<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">Visual C++ Libraries Developer<o:p></o:p></span></p>
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