<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/68615>68615</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [clang] [Modules] Add warning for including header in module purview
        </td>
    </tr>

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

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

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

<pre>
    Given the following code

```cpp
export module a;

#include <new>
```

When compiling with `-std=c++26 -stdlib=libc++ -Weverything`

all that we get as output is

```console
In file included from <source>:3:
/opt/compiler-explorer/clang-assertions-trunk-20231009/bin/../include/c++/v1/new:217:66: error: declaration of 'operator new' in module a follows declaration in the global module
  217 | _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_OVERRIDABLE_FUNC_VIS void* operator new(std::size_t __sz) _THROW_BAD_ALLOC;
      | ^
note: previous declaration is here
/opt/compiler-explorer/clang-assertions-trunk-20231009/bin/../include/c++/v1/new:219:36: error: declaration of 'operator delete' in module a follows declaration in the global module
  219 | _LIBCPP_OVERRIDABLE_FUNC_VIS void  operator delete(void* __p) _NOEXCEPT;
      | ^
note: previous declaration is here
/opt/compiler-explorer/clang-assertions-trunk-20231009/bin/../include/c++/v1/new:225:66: error: declaration of 'operator new[]' in module a follows declaration in the global module
  225 | _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_OVERRIDABLE_FUNC_VIS void* operator new[](std::size_t __sz) _THROW_BAD_ALLOC;
      | ^
note: previous declaration is here
/opt/compiler-explorer/clang-assertions-trunk-20231009/bin/../include/c++/v1/new:227:36: error: declaration of 'operator delete[]' in module a follows declaration in the global module
  227 | _LIBCPP_OVERRIDABLE_FUNC_VIS void  operator delete[](void* __p) _NOEXCEPT;
      | ^
note: previous declaration is here
/opt/compiler-explorer/clang-assertions-trunk-20231009/bin/../include/c++/v1/new:234:66: error: declaration of 'operator new' in module a follows declaration in the global module
  234 | _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_OVERRIDABLE_FUNC_VIS void* operator new(std::size_t __sz, std::align_val_t) _THROW_BAD_ALLOC;
      | ^
note: previous declaration is here
/opt/compiler-explorer/clang-assertions-trunk-20231009/bin/../include/c++/v1/new:236:36: error: declaration of 'operator delete' in module a follows declaration in the global module
  236 | _LIBCPP_OVERRIDABLE_FUNC_VIS void  operator delete(void* __p, std::align_val_t) _NOEXCEPT;
      | ^
note: previous declaration is here
/opt/compiler-explorer/clang-assertions-trunk-20231009/bin/../include/c++/v1/new:242:66: error: declaration of 'operator new[]' in module a follows declaration in the global module
  242 | _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_OVERRIDABLE_FUNC_VIS void* operator new[](std::size_t __sz, std::align_val_t) _THROW_BAD_ALLOC;
      | ^
note: previous declaration is here
/opt/compiler-explorer/clang-assertions-trunk-20231009/bin/../include/c++/v1/new:244:36: error: declaration of 'operator delete[]' in module a follows declaration in the global module
  244 | _LIBCPP_OVERRIDABLE_FUNC_VIS void  operator delete[](void* __p, std::align_val_t) _NOEXCEPT;
      | ^
note: previous declaration is here
8 errors generated.
Compiler returned: 1
```

This is not obvious to users what they did wrong. The issue here is that the `#include` is in the module purview. It would be nice to have a general warning saying "Don't include there, type `module; #include <whatever>` instead.
</pre>
<img width="1px" height="1px" alt="" src="http://email.email.llvm.org/o/eJzcWFtv2zgT_TX0y8CGRN2sBz_IF32fgWxTpNm2bwItjiXu0qRAUnbTX7-grLhNdrfYbbMJGsOwLN5mzpw5GoyYtaJRiAuSLEmynrDetdosODsKbp1WONlpfrf4nziiAtci7LWU-iRUA7XmSII1CYrxNw3O37rrziP4qdPGwUHzXiIwEi0frKeRULXsOQKJVgpPJNo8Ounr5R9aVFDrQyekt34SrgWSBlPrOInWNaFLQpc0BT8gxY5Eayl24zBMP-ARzZ1rhWoencukBNcyByeEBh0wC7p3Xe9A2L-Gp5XVcoS-VbAXEmFEwmFv9MHjsbo3NXpIURGR6IK51J0jtDwDQTPFT53UBo0fk0w1U2YtGie0slNnevX7lAY0CoMgJ7TcCUVoOZsRWo4G_bYzRkLLY0hoOQSyoGFGoiJNSVQAGqON_8OxlswwfzjoPRCa6Q4Nc9qA30UzEOrC1si0fbBLnJOgkXrH5Lj0jAyAhhmQbAXV1Xa5evu2enO93r5bFTfrqihvNzfV6uPHMLvMXr_f3Nxs18XyalOVv75ZVe-37-CoBSe0gIduzQeKCxIVVnzGykFV2c-E5lDd_v_m-kO1LNZVcXV1vbokGAwf7wxJxpxS2qGPQWfwKHT_CJaFFg0-O0e5T45_zBFHiQ5_nKb8AU1_SwTAnyzP7wmqqm4g4M315uNq8_b2Z4s8Tf61Oobn4w8Hnyb_iUZG516tUmj2PUp5Isqy79XLPSuvRTVR_Ow1JYqftaas4DLOpGhUdWSycq9BQYN4nr3WROkT1ZpvEPOzqimmL1SDYvoCNej1KiuOX642xfGT1qZnU9n8HCoLDSrvF_LZeWI1sgUGXW8Uem8g_EZbeNsK689W2oHenc06Db1FY-Hk-zrX4h1wweFktGpmcNsiCGt7HPzxe924zPeTX7pSkgZ-coz_yFHXm6PA0wy2Dk66lxx2CErU6I227OhZPGOScGJG-VbVsjt_IZSutSI0c_fdoj_YoA-7u-sG6yO90RIedsceiO9gfT_p3VLWIeOzCV9EPI9yNsFFmObpPIvjIJm0izjaz1lMeU0DNs8SmsdROA8wz1mcRllYT8TiPtnDeRAEdJbWWY4Z4_s0YUEeZiQO8MCEnEl5PMy0aSZDzBbpPA2TiWQ7lHZ4aUDpoCZCKUnWE7Pw66e7vrEkDqSwzn45wQknhzcN5x3JGkiy_GWAbP1dwfklaHttxjD5uxYZR_OVVkYeJr2Ri9a5zvqspSWhZSNc2-9mtT4QWnrT42XaGf0b1v6RMCCxhJYDmD8CAAD__9WTTVw">