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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - implicit instantiation of undefined template 'std::tuple_size<auto>'"
href="https://bugs.llvm.org/show_bug.cgi?id=49747">49747</a>
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<th>Summary</th>
<td>implicit instantiation of undefined template 'std::tuple_size<auto>'
</td>
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<th>Product</th>
<td>libc++
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<th>Version</th>
<td>11.0
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>All
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>release blocker
</td>
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>All Bugs
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>pro.guillaume.dua@gmail.com
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org, mclow.lists@gmail.com
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<p>
<div>
<pre>Not sure if this is error is caused by the way `std::tuple_size` 's SFINAE is
implemented, and/or the way template-template-parameters are instanciated in
such context.
<a href="https://godbolt.org/z/GGs7ndKE4">https://godbolt.org/z/GGs7ndKE4</a>
```log
error: implicit instantiation of undefined template 'std::tuple_size<auto>'
```
Also, Clang-CL add this error message previously to the one mentioned above :
```log
error : cannot mangle this 'auto' type yet
```
See also the original discussion on SO :
<a href="https://stackoverflow.com/questions/66821952/clang-error-implicit-instantiation-of-undefined-template-stdtuple-sizeauto/66822584">https://stackoverflow.com/questions/66821952/clang-error-implicit-instantiation-of-undefined-template-stdtuple-sizeauto/66822584</a></pre>
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