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<p class="MsoNormal">For the test case below, clang++-12 does not emit an error (likely the same on ToT). Nor does g++-9.4.0 with libstdc++. But should they? I suppose “23.7.3.1 Constructors” of C++17 is the relevant specification. Can anyone clarify?
I’m not quite sure: is this particular overload resolution issue more of a compiler or library issue?<o:p></o:p></p>
<p class="MsoNormal" style="margin-left:.5in"><o:p> </o:p></p>
<p class="MsoNormal" style="margin-left:.5in">$ clang++ -fsyntax-only -std=c++17 -x c++ -c test_case.cpp -stdlib=libc++<o:p></o:p></p>
<p class="MsoNormal" style="margin-left:.5in"><o:p> </o:p></p>
<p class="MsoNormal" style="margin-left:.5in">~~~~<br>
<br>
<o:p></o:p></p>
<p class="MsoNormal" style="margin-left:.5in">#include <variant><o:p></o:p></p>
<p class="MsoNormal" style="margin-left:.5in"><o:p> </o:p></p>
<p class="MsoNormal" style="margin-left:.5in">struct A {} const a;<o:p></o:p></p>
<p class="MsoNormal" style="margin-left:.5in"><o:p> </o:p></p>
<p class="MsoNormal" style="margin-left:.5in">template <class T> struct S{<o:p></o:p></p>
<p class="MsoNormal" style="margin-left:.5in"> S(T&&...) {}<o:p></o:p></p>
<p class="MsoNormal" style="margin-left:.5in"> S(int) {}<o:p></o:p></p>
<p class="MsoNormal" style="margin-left:.5in">};<o:p></o:p></p>
<p class="MsoNormal" style="margin-left:.5in"><o:p> </o:p></p>
<p class="MsoNormal" style="margin-left:.5in">std::variant<int, S<A>> b(1);<o:p></o:p></p>
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