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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++20] Wrongly worded warning on defaulted-as-deleted operator!="
href="https://bugs.llvm.org/show_bug.cgi?id=51874">51874</a>
</td>
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<th>Summary</th>
<td>[C++20] Wrongly worded warning on defaulted-as-deleted operator!=
</td>
</tr>
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<th>Product</th>
<td>clang
</td>
</tr>
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>All
</td>
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<th>OS</th>
<td>All
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>C++2a
</td>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
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<th>Reporter</th>
<td>arthur.j.odwyer@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>// <a href="https://godbolt.org/z/GP1d8f5Kx">https://godbolt.org/z/GP1d8f5Kx</a>
#include <compare>
struct C {
friend std::strong_ordering operator<=>(const C&, const C&);
bool operator!=(const C&) const = default;
};
<source>:5:8: warning: explicitly defaulted equality comparison operator is
implicitly deleted [-Wdefaulted-function-deleted]
bool operator!=(const C&) const = default;
^
<source>:5:8: note: defaulted 'operator!=' is implicitly deleted because there
is no viable three-way comparison function for 'C'
The compiler is right to diagnose this ill-formed program, but wrong to claim
that there is no viable "three-way comparison function".
GCC gives a more accurate diagnostic (but only at the point where the
defaulted-as-deleted function is actually called):
<source>:5:8: note: 'bool C::operator!=(const C&) const' is implicitly deleted
because the default definition would be ill-formed:
5 | bool operator!=(const C&) const = default;
| ^~~~~~~~
<source>:5:8: error: no match for 'operator==' (operand types are 'const C' and
'const C')</pre>
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