<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/73664>73664</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            `vector<int*const>` fail to build with an error in C++20 mode
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            libc++
      </td>
    </tr>

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

    <tr>
      <th>Reporter</th>
      <td>
          ilya-biryukov
      </td>
    </tr>
</table>

<pre>
    This code should technically be allowed per C++20 standard (`int *const` meets the requirement of [MoveInsertable](https://en.cppreference.com/w/cpp/named_req/MoveInsertable) and [Erasable](https://en.cppreference.com/w/cpp/named_req/Erasable)):
```cpp
#include <vector>

int main() {
    std::vector<int* const> foo;
 foo.push_back(nullptr);
}
```

However, when I build with `clang++ -std=c++20` using libc++ from close to head, I get a compiler error:
```
../include/c++/v1/__algorithm/move.h:42:17: error: cannot assign to return value because function 'operator*' returns a const value
 42 |       *__result = _IterOps<_AlgPolicy>::__iter_move(__first);
...
<source>:5:9: note: in instantiation of member function 'std::vector<const int *const>::push_back' requested here
    5 | foo.push_back(nullptr);

```

Compiling with `-std=c++17` produces no errors. I believe this is somehow related to allocators, because specifying `-D_LIBCPP_ENABLE_CXX20_REMOVED_ALLOCATOR_MEMBERS` and `-D_LIBCPP_ENABLE_CXX20_REMOVED_ALLOCATOR_VOID_SPECIALIZATION` with `-std=c++20` makes this code compile again.


See [godbolt](https://gcc.godbolt.org/z/4rfx7nqzM) too.

</pre>
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