<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/145975>145975</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            Unexpected "reference to 'std' is ambiguous" error with C++20 modules
        </td>
    </tr>

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

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

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

<pre>
    Reproducer: https://gist.github.com/MikailBag/1759e1c092649ee749fa0f620805fd62

Adding `namespace std {}` to GMF in connection.cpp fixes error.

Compiler version:
```
$ /home/mb/projects/llvm-project/build/bin/clang++ --version
clang version 21.0.0git (https://github.com/llvm/llvm-project.git 1276a5b368493cc73ef0febee35a6591b92464d5)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /home/mb/projects/llvm-project/build/bin
Build config: +assertions
```

Originally reported in https://github.com/llvm/llvm-project/issues/118137#issuecomment-3005759000, this is minimized version.
</pre>
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