<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 - Unused arguments in alias template specialisation are not treated as substitution failure"
href="https://bugs.llvm.org/show_bug.cgi?id=45782">45782</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Unused arguments in alias template specialisation are not treated as substitution failure
</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++17
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>v@vsamko.com
</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>template<typename... T>
using void_t = void;
template<typename T, typename=void>
struct has_reflect_members {};
template<typename T>
struct has_reflect_members<T, void_t<typename T::mytype>> {};
template<typename T>
struct has_reflect_members<T, void_t<typename T::anothertype>> {};
results in
<source>:9:8: error: redefinition of 'has_reflect_members<T, void_t<typename
T::anothertype> >'
struct has_reflect_members<T, void_t<typename T::anothertype>> {};
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
<source>:7:8: note: previous definition is here
struct has_reflect_members<T, void_t<typename T::mytype>> {};
But according to <a href="http://open-std.org/JTC1/SC22/WG21/docs/cwg_defects.html#1558">http://open-std.org/JTC1/SC22/WG21/docs/cwg_defects.html#1558</a>
these specialisations can rely on substitution failure and they wouldn't be
redefinitions.</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>