The code below fails to compile on GCC and CLang (msvc fails because of the experimental/propagate_const).

It is just PoC. Imagine the type X being complex, comparison operator meaningful and vector m non-empty.

#include <ranges>
#include <vector>
#include <experimental/propagate_const>
#include <memory>
#include <algorithm>

class X {};

std::shared_ptr<X> simplify(std::experimental::propagate_const<std::shared_ptr<X>>& i) {
   return get_underlying(i);
}

int operator<=>(const std::shared_ptr<X>& lhs, const std::shared_ptr<X>& rhs) {
   return 0;
}

void swap(std::shared_ptr<X> lhs, std::shared_ptr<X> rhs) {
   std::swap(lhs, rhs);
}

int main() {
   std::vector<std::experimental::propagate_const<std::shared_ptr<X>>> m;
   decltype(m | std::views::transform(simplify)) r = m | std::views::transform(simplify);
   std::sort(r.begin(), r.end()); // compiles
   std::stable_sort(r.begin(), r.end()); // ERROR: no matching function for call to ‘__rotate`...
}

What is so special in std::stable_sort that it prevents compilation? How should I implement the __rotate?