<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/54578>54578</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            clang 14.0.0 bug: "undefined reference error" for a consteval function.
        </td>
    </tr>

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

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

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

<pre>
    ```
inline consteval unsigned char operator""_UC(const unsigned long long n)
{
    return static_cast<unsigned char>(n);
}

inline consteval char f1(auto const octet)
{
    return char(octet >> 4_UC);
}

inline constexpr char f2(auto const octet)
{
    return char(octet >> 4_UC);
}

int main()
{
    auto c1 = f1('A'); // ok
    auto c2 = f2('A'); // error

    return c1 + c2;
}
```

Compiled with: ```clang++-14 -std=c++20 -stdlib=libc++```, and the error message is:

```undefined reference to `operator"" _UC(unsigned long long)'```

See online demo: [https://godbolt.org/z/WarbWYcfP](https://godbolt.org/z/WarbWYcfP)

StackOverflow question link: https://stackoverflow.com/questions/71634835/why-does-consteval-not-behave-as-expected

</pre>
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