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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - ICE when not unpacking variadic template into concept"
href="https://bugs.llvm.org/show_bug.cgi?id=47386">47386</a>
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<th>Summary</th>
<td>ICE when not unpacking variadic template into concept
</td>
</tr>
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<th>Product</th>
<td>clang
</td>
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<th>Version</th>
<td>10.0
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Linux
</td>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>enhancement
</td>
</tr>
<tr>
<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>
</tr>
<tr>
<th>Reporter</th>
<td>matt+llvm@offtopica.uk
</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>Compiling this causes an ICE:
template <typename... Ts>
concept Foo = true;
template <typename... Ts> requires Foo<Ts /* ... */>
class Bar {};
Bar<int> bar;
GCC 10.2.0 fails gracefully with an error, stating that the parameter pack
isn't expanded.
$ g++ -std=c++2a -c foo.cc
foo.cc:4:36: error: parameter packs not expanded with '...':
4 | template <typename... Ts> requires Foo<Ts /* ... */>
| ^~~~~~~~~~~~~~~~~
foo.cc:4:36: note: 'Ts'
foo.cc:7:8: error: template constraint failure for 'template<class ... Ts>
requires <erroneous-expression> class Bar'
7 | Bar<int> bar;
| ^
foo.cc:7:8: note: constraints not satisfied</pre>
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