<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/54279>54279</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [Crash][UNREACHABLE] Didn't find this decl on its identifier's chain!
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            new issue
      </td>
    </tr>

    <tr>
      <th>Assignees</th>
      <td>
      </td>
    </tr>

    <tr>
      <th>Reporter</th>
      <td>
          Sameeranjoshi
      </td>
    </tr>
</table>

<pre>
    While compiling the application dealii[1] with trunk, I am getting an error in the semantic phase of Clang.

TL;DR version
```
Didn't find this decl on its identifier's chain!
UNREACHABLE executed at ${HOME}/llvm-project/clang/lib/Sema/IdentifierResolver.cpp:82!
```
Attaching the bug report, script, and preprocessed sources as 

- [x] [bug_report.txt](https://github.com/llvm/llvm-project/files/8207514/bug_report.txt)
- [ ] Script = Unable to attach script
- [ ] Preprocessed Sources = Unable to attach a `.cpp` file 

Not sure if GitHub is not allowing to upload the files, but if needed I can attach or paste text.
[1] https://github.com/dealii/dealii

</pre>
<img width="1px" height="1px" alt="" src="http://email.email.llvm.org/o/eJydU11vnDAQ_DXmZRUE5i5wDzzcR9pEStMq16iPlbENOPVhZC_J9d934Uh6TatKrYTwYrO7M7Pjyqnv5ZfWWA3SHXpjTdcAthpE31sjBRrXgdLCGsOWm5Qtd_BssAX0Q_eN8S3cgDhAoxHHRNGB9t55MN1UJOiD6NBI6FsRNLgatlZ0TcySHUvWp_fnW5ZtdvfwpH2gZvPRZTI_0-fOqI7xHKE2naLKJhAmaYGwGQxglKYutdGefgogW2Ho9_SU-3B3f7XeXq83t1egj1oOqBUIBMYXLN9cf_xwxfId4--sfTpc9N49aon0KUeg47ap6L0nIrTcvDa618FZghzLvmfZuuCv_d5AXyMK2b6oWg0NeN07j6N2QXrTT5EgWj0deCd1CAQwuMFTCCLAuVgXQFM4jlOglYp9PRWL8Yi0yXjRIvaBABFYehoa1VDFNNmZ4O88axp9oLXgSb5MFxS9KctXZ61hbL2fYAPLdvDQiYqsg44UHXm-UHqT8emc2n6m9sd8AaTcJOplAiO2X-jfOYQweA2mhvcGr4cKyAod7Qpr3fOksoOht06oSe-Z3ZaExzGp01oRhBuQZNW5Jdm1FwEJhT7iizVnr_9FzvlSvAZTXqTKTK2ylYjQoNUl1dl6EdpxOMvNmRXH4v_n6mjwtvznMZsQhmnOywXPV1FbVhlfLFQia5kVMld5tuKFlLlM84prdVlHVlTahpEB47zTzzCVoJigR6bkCedJlhTpMlulq7golEp4VchUZHWaS7ZI6MoYG484YuebyJcTJHJXoENrAoafhyIE09BwpnZUXwzYOl_uxUFrL7pHF1oTTQDKicAP3jN-jQ">