<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/100726>100726</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            `<algorithm>`: `ranges::upper_bound` uses incorrect helper lambda
        </td>
    </tr>

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

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

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

<pre>
    https://github.com/llvm/llvm-project/blob/94e966255fb4309f24805273d2e17f63a4e36d17/libcxx/include/__algorithm/ranges_upper_bound.h#L49-L62

The parameter type of the help lambda here is _const_ _lvalue_ reference, which results in it passing two const lvalue to `comp` which may not be invocable.

```cpp
#include <vector>
#include <algorithm>

struct S {
  operator int();
  operator int() const = delete;
};

int main() {
  std::vector<int> v;
  auto cmp = [](int, int) { return true; };
  auto proj = [](int) { return S{}; };
 (void) std::ranges::upper_bound(v, 0, cmp, proj); // hard error in libc++
}
```
https://godbolt.org/z/hxhf6esbv
</pre>
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