<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/125521>125521</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [clang++] Implicit template instantiations in modules cause errors in other modules
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            clang
      </td>
    </tr>

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

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

<pre>
    If module A instantiates a template Class\<T\>, any module that imports module A and also tries to instantiate Class\<T\> (with the same T) will get an error:
```
/home/modBug/reproducer/src/hello.h:8:38: error: declaration 'get' attached to named module 'Mod2' can't be attached to other modules
 8 |     template <typename V> friend int get() noexcept;
      | ^
/home/modBug/reproducer/src/hello.h:3:27: note: also found
    3 | template <typename V> int get() noexcept {return 0;};
 |                           ^
```
See [this reproducer](https://github.com/user-attachments/files/18644458/reproducer.zip) or https://godbolt.org/z/d7YW7TM4a where instantiating List\<int\> in Mod2 causes any module that also imports Mod2 to fail to instantiate List\<int\>.
I think this is a bug because the global module fragment is not supposed to be exported.
</pre>
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