<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=http://email.email.llvm.org/c/eJylVE1v4zYQ_TXyZWBDpiLbOejgOE6RS4siAXpcUOJIZkuTAknZyb_vo6T1bhbBtmgN2hY_9ObNm8epnXqvDkbajqIf7F-UiV1wzlJ0VDOt7zJxT57_5CYGiicd6CKNVnTIxAMG9d51Xp6zYp_lj1m-zzb5PMZp5HNvZOSsODRGhkCvWXEkOQC9RSRtYyYO9Iqo-z5FWqZtxY2J7z3jwLyeFQ8_w2ucDZHfek8AHIGNs91H5Gz7gDzi4C2tAYf54wQZooy6-QIw9mCza4F9cVoBGLM8odjBmD76EaZ4xADEd6RS0LPUduQ7RrqB_yDH9Pt64qRbbfhMOqkqI00lCEPfOw-l0xuJ-Can1nlKfKh3CMQ-JEYykLTEb5Ft0M6mhOohTlC3VYCD0zaS0kEimoI89PL0_Ot-lAyKxbCi5wgyQAYiXaW3GjyQiWziII15J33bj-Ad5Jlvx-JVNzwq8Xn153PYpueX326eUY4DWRcJ-O4KUkp7-CsxTqNnL60i11IyAbhsx_ShBx4pKx-Wf6SFJSqyVOy5xdeCRzlr_t_dRT_9ZOUx2x4_TfSr9iA4ZdY5p4itG7rTaq6tZVYhXaubsnMp5FW-j9oC7hNysMDs21GO4KYqpxccfjy5C3vjpKIGlsCdbU4usF19dBx8huFZDQ180Hp3HhEUt9rqSfo2EQhRpWoWe9Sg4zA9a9juyxlxEhl4aC6kyFf_8pUwOTsg9NRXtL24JnlytLe07wnomM5ekRLP_j_OL1_ZmCUOnlmlgkICmDJl9AEFh8d7K1J1kpMm3VNtUkl-ORxWC1UV6r64lwuY5OR89fswvPVmCM7yYvCmOsXYjxmIJ4xOx9NQrxp3xsSYy9e_JW5v6oiY6hAG5CyeyuJuLRanatOuNxtZ1rmqS5a1LDf1VuzuC9mKXd3sdgsjazahgo8zIZpJSTylxL4tiPy7pZQGOKFouLNWfduZ-_JybMlpuXxc_P8cdCVyIfK12OTFXVGuV_m22Akp1jnvtu2mLLO7nNHvzCrhrJzvFr4aIeuhC9g0OqCx3DbRWXUH948pg2HU0XD1cnKDUVN_mtveP3e9SIZliJ_0scWYRDVm8DfymBjh>53412</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            Shouldn't support `*p` for void pointers, at least in SFINAE contexts
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            c++,
            c++20,
            clang:frontend,
            rejects-valid
      </td>
    </tr>

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

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

<pre>
    Clang trunk (soon to be 14) rejects this valid C++ program:
```
template<class T> auto f(int, T *p) -> decltype(*p);
template<class T> constexpr int f(long, T *p) { return 1; }
static_assert(f<void>(0, nullptr) == 1);
int main() {}
```

The problem is that Clang supports `*p` for void pointers, as an extension; but that extension isn't disabled in SFINAE contexts. It prints a warning (actually it prints the same warning twice):
```
warning: ISO C++ does not allow indirection on operand of type 'void *' [-Wvoid-ptr-dereference]
auto f(int, T *p) -> decltype(*p);
                              ^~
```
but that's not good enough. Clang needs to actually SFINAE away the `decltype(*p)` return type so that the other overload can be chosen.

This is reduced from the definition of `std::ranges::iter_move` in C++20. `std::ranges::iter_move` is supposed to be invocable for any `E` where `*E` is well-formed, so it is invocable for `void*` on Clang but not GCC.
</pre>
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