<html>
<head>
<base href="https://bugs.llvm.org/">
</head>
<body><table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Defaulted comparisons deleted for class containing class containing class template with user-provided operator<=> with deduced return type"
href="https://bugs.llvm.org/show_bug.cgi?id=44723">44723</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Defaulted comparisons deleted for class containing class containing class template with user-provided operator<=> with deduced return type
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>Linux
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>C++2a
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>david@doublewise.net
</td>
</tr>
<tr>
<th>CC</th>
<td>blitzrakete@gmail.com, erik.pilkington@gmail.com, llvm-bugs@lists.llvm.org, richard-llvm@metafoo.co.uk
</td>
</tr></table>
<p>
<div>
<pre>The following valid code:
```
#include <compare>
template<int>
struct a {
friend constexpr auto operator<=>(a const & lhs, a const & rhs) {
return std::strong_ordering::equal;
}
};
struct b {
friend auto operator<=>(b const &, b const &) = default;
a<0> m_value;
};
struct c {
friend auto operator<=>(c const &, c const &) = default;
a<0> m_value;
};
auto x = c() <=> c();
```
is rejected with the message:
```
main.cpp:11:14: warning: explicitly defaulted three-way comparison operator is
implicitly deleted [-Wdefaulted-function-deleted]
friend auto operator<=>(b const &, b const &) = default;
^
main.cpp:12:7: note: return type of defaulted 'operator<=>' cannot be deduced
because return type 'auto' of three-way comparison for member 'm_value' is not
a standard comparison category type
a<0> m_value;
^
main.cpp:5:24: note: selected 'operator<=>' for member 'm_value' declared here
friend constexpr auto operator<=>(a const & lhs, a const & rhs) {
^
main.cpp:16:14: warning: explicitly defaulted three-way comparison operator is
implicitly deleted [-Wdefaulted-function-deleted]
friend auto operator<=>(c const &, c const &) = default;
^
main.cpp:17:7: note: return type of defaulted 'operator<=>' cannot be deduced
because return type 'auto' of three-way comparison for member 'm_value' is not
a standard comparison category type
a<0> m_value;
^
main.cpp:5:24: note: selected 'operator<=>' for member 'm_value' declared here
friend constexpr auto operator<=>(a const & lhs, a const & rhs) {
^
main.cpp:19:14: error: overload resolution selected deleted operator '<=>'
auto x = c() <=> c();
~~~ ^ ~~~
main.cpp:16:14: note: candidate function has been implicitly deleted
friend auto operator<=>(c const &, c const &) = default;
^
2 warnings and 1 error generated.
```</pre>
</div>
</p>
<hr>
<span>You are receiving this mail because:</span>
<ul>
<li>You are on the CC list for the bug.</li>
</ul>
</body>
</html>