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<base href="https://bugs.llvm.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - c++2a reports an error of overloaded operator while c++11/17 accepts"
href="https://bugs.llvm.org/show_bug.cgi?id=47356">47356</a>
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<th>Summary</th>
<td>c++2a reports an error of overloaded operator while c++11/17 accepts
</td>
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<th>Product</th>
<td>clang
</td>
</tr>
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<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Linux
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>enhancement
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>C++2a
</td>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>tangyixuan@mail.dlut.edu.cn
</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
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<p>
<div>
<pre>The following code is rejected by -std=c++2a, while ok with -std=c++11 or
-std=c++17.
$ cat s.cpp
template<typename T>
struct A {
A() {}
template<typename U>
A(const A<U>&) {}
bool operator==(const A&) const { return true; }
};
A<const int> a;
A<int> b;
auto c = (a == b);
$ clang -v
clang version 11.0.0 (<a href="https://github.com/llvm/llvm-project.git">https://github.com/llvm/llvm-project.git</a>
ab4627364aefcaac751e757b721b7d07b48a545a)
Target: x86_64-unknown-linux-gnu
Thread model: posix
$ clang++ -c -std=c++17 s.cpp
success.
$ clang++ -c -std=c++2a s.cpp
s.cpp:13:13: error: use of overloaded operator '==' is ambiguous (with operand
types 'A<const int>' and 'A<int>')
auto c = (a == b);
~ ^ ~
s.cpp:8:8: note: candidate function
bool operator==(const A&) const { return true; }
^
s.cpp:8:8: note: candidate function (with reversed parameter order)
1 error generated.</pre>
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