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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Assertion fail with nested requires requires and varadic template"
href="https://bugs.llvm.org/show_bug.cgi?id=48780">48780</a>
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<th>Summary</th>
<td>Assertion fail with nested requires requires and varadic template
</td>
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<th>Product</th>
<td>clang
</td>
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<th>Version</th>
<td>trunk
</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>
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<th>Severity</th>
<td>enhancement
</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
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<th>Reporter</th>
<td>ryan_greenblatt@brown.edu
</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>
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<pre>```
template <typename T> struct StructWithMember;
template <typename T>
concept NestedRequiresRequires = requires {
requires requires { StructWithMember<T>::value; };
};
template <NestedRequiresRequires... T> struct Variadic {};
constexpr Variadic<int> a;
```
This trips an assertion:
Assertion `!isExprSubstitutionFailure() && "ExprRequirement has no expression
because there has been a " "substitution failure."' failed.
This minimal reproduction doesn't crash when compiled by a -NDEBUG build of
clang, but I have seen crashes in -NDEBUG builds related to this issue in more
complex code. So the probablem isn't just an incorrect assertion.</pre>
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