<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/102360>102360</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [C++20][Modules] Variable template in instantiation chain attached to wrong module
        </td>
    </tr>

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

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

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

<pre>
    Given the following translation units:

```c++
export module a;

template<typename>
constexpr auto impl = true;

export template<typename T>
void a() {
}

export template<typename T> requires impl<T>
void a() {
}
```

```c++
export module b;

import a;

static void b() {
        a<void>();
}
```

```c++
export module c;

import a;

static void c() {
        a<void>();
}
```

```c++
import a;
import b;
import c;

static void d() {
        a<void>();
}
```

clang incorrectly errors with

```console
In file included from /app/d.cpp:1:
a.cpp:4:16: error: declaration 'impl<void>' attached to named module 'b' can't be attached to other modules
    4 | constexpr auto impl = true;
      | ^
a.cpp:4:16: note: also found
1 error generated.
```

See it live: https://godbolt.org/z/fKEvse3PK

This occurs even if `impl` is declared `static`, but does not seem to occur if `impl` is declared in the unnamed namespace. That workaround does not work for me, because this was reduced from a bug where clang complained about a variable template specialization of a variable template exported in a different module.
</pre>
<img width="1px" height="1px" alt="" src="http://email.email.llvm.org/o/eJy0Vd9v4zYM_muUF-ICWU7s5MEPbdIMw2HAgBV7pyU61iZLnn4k1_vrB9lJ26Xd4YrtAsMxSOrTx08khSHooyVq2PqerfcLTLF3vlF40ipEZ2nROvXU_KRPZCH2BJ0zxp21PUL0aIPBqJ2FZHUMrLxjfM_49V3x-ZFM3OdnstKX0fkIg1PJECAr71-viTSMBiOxchefRrI4ECsfZp90NkT6MnrAFB3oYTTAyj1En-gG5rLJO2jw-Ix3cloBMrFhYgusvgLU-w8ggae_kvYUJjqs3H0__FWdj0rW3uSqh8l7q2SIGLWEiUX7hgXfIit32Zn5Tt6X9f-Zovw4RfnDKb4hcTG0t4Zb9q9pqv-RpjRoj6CtdN6TjOYJyHvnA5x17N_Px9ngDM3Wny102lAGMEmRgs67AZg44DgycVBLOY6svCueuxIvllW2Vqy8m_fLH4qkQT-3MhP1pZafk6oBY0TZk4LoIBe_uh41E3WbAyRaJuoILf0j1sWe_CU2zDQAAFbA6h18V0PD9MvhbP3wb4lYl1vzDtAEB51LVs2RxZwiHMmSx0hq-Y3z-I0IdASjTxNWH-M4jTRxYOJwdKp1Ji6dPzJx-MrEofv8cApU_vr5NcZjrwM4KZMPQHlk6g5YxSdBKw46XKQmlc1zZWUaYgdtiqAchZwMBKJh0i9DfQNEz0M52flQ8juMKGkJjz1GODv_J_qsxwt0tkHnPAw0bUsSUyCImfkZA3hSSV7LCaFNRzj35AnmepUuT0JtSQG2LkVAOKHX2Bp6npIQRpIajf46l5Tr3o2ah8acBYLSXUee7HWKLBeqKdW23OKCmqIWJa8KUawWfbPGmqjsqpJvKl5WYlN3VVnw1QaJt-W2WOhGcLHiG14Lzqv1arkWShSV7LaioEIVFVtxGlCbpTGnIZ_pQoeQqCm4KCu-MNiSCdOVKISlM0xeJkS-IX2TF31q0zGwFTc6xPACE3U00126m0eP4Gy9Z-v7Xy4dsN7D72900Ba0DRFt1LNesscsyas-OntnjxdhFsmb5qY6dexTu5RuYOKQyVz-Po3e_UEyMnGYUghMHC45nhrxdwAAAP__Wctfjg">