<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/65907>65907</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            std::pair constructor helper __pair_like_explicit_wknd not SFINAE correctly
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            libc++,
            new issue
      </td>
    </tr>

    <tr>
      <th>Assignees</th>
      <td>
            huixie90
      </td>
    </tr>

    <tr>
      <th>Reporter</th>
      <td>
          huixie90
      </td>
    </tr>
</table>

<pre>
    The following code, extracted from Boost.JSON, compiles under C++20
but fails with Clang trunk libc++ in C++2b mode:

```cpp
#include <type_traits>
#include <utility>

struct kvp {
  kvp() = default;
  explicit kvp(std::pair<int, int> const& p);
};

namespace std {

template <>
struct tuple_size<kvp> : std::integral_constant<std::size_t, 2> {};

template <>
struct tuple_element<0, kvp> {
  using type = int;
};

template <>
struct tuple_element<1, kvp> {
  using type = int;
};

} // namespace std

int main()
{
  kvp k1;
 static_assert(noexcept(kvp(std::move(k1))));
}
```
(https://godbolt.org/z/4cGdPxrxx)
</pre>
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