<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/61676>61676</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            Format, IntegerLiteralSeparator not correct with literal suffix
        </td>
    </tr>

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

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

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

<pre>
    `auto NR = 0x4000'0000_u64;` becomes `auto NR = 0x4'0000'000_u64;` for config:
````
IntegerLiteralSeparator:
 Binary:          4
  Decimal:         0
  Hex: 4
````
I would expect the first.

Note that literal is defined in the following way (in another header):
````
   constexpr auto operator"" _u64(unsigned long long value) noexcept -> std::uint64_t
 {
      return static_cast<std::uint64_t>(value);
 }
````

It feels like it considers the _ as part of the number. Though this is needed according to https://en.cppreference.com/w/cpp/language/user_literal
> All ud-suffixes introduced by a program must begin with the underscore character _. The standard library ud-suffixes do not begin with underscores. 

Bug found on LLVM 16, was not a problem in LLVM 16-rc2
</pre>
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