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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Operator overload resolution fails in fold expressions"
href="https://bugs.llvm.org/show_bug.cgi?id=46577">46577</a>
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<th>Summary</th>
<td>Operator overload resolution fails in fold expressions
</td>
</tr>
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<th>Product</th>
<td>clang
</td>
</tr>
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<th>Version</th>
<td>10.0
</td>
</tr>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>All
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>C++17
</td>
</tr>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>micjabbour@gmail.com
</td>
</tr>
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<th>CC</th>
<td>blitzrakete@gmail.com, erik.pilkington@gmail.com, llvm-bugs@lists.llvm.org, richard-llvm@metafoo.co.uk
</td>
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<p>
<div>
<pre>Given the following minimal example (which compiles successfully on GCC and
MSVC):
struct A {};
namespace detail {
// operator+ overload
A operator+(A, A) { return A{}; }
A f(A a) {
return a + a; // this works fine
}
template <typename... As> A g(As... as) {
// this however, fails to find operator+ when g is instantiated with "A"s
return (as + ... + A{});
}
}
int main() {
detail::f(A{}); // works
detail::g(A{}); // fails!
}
Clang gives the following error:
D:\ws> clang++ -std=c++17 prog.cc
prog.cc:11:16: error: call to function 'operator+' that is neither visible in
the template definition nor found by argument-dependent lookup
return (as + ... + A{});
^
prog.cc:17:11: note: in instantiation of function template specialization
'detail::g<A>' requested here
detail::g(A{}); // fails!
^
prog.cc:5:3: note: 'operator+' should be declared prior to the call site or in
the global namespace
A operator+(A, A) { return A{}; }
^
1 error generated.</pre>
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