[Bug libstdc++/121913] New: ranges::rotate should use ranges::iter_move

[redi at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121913

            Bug ID: 121913
           Summary: ranges::rotate should use ranges::iter_move
           Product: gcc
           Version: 15.2.0
            Status: UNCONFIRMED
          Keywords: rejects-valid
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: redi at gcc dot gnu.org
  Target Milestone: ---

#include <algorithm>

struct A { };

struct B {
  B() = default;
  B& operator=(const B&) = delete;
  B& operator=(const A&) const;

  operator A() const;
};

struct I {
  using value_type = A;
  using difference_type = int;
  B operator*() const { return {}; }
  I& operator++() { ++pos; return *this; }
  I operator++(int) { I tmp = *this; ++pos; return tmp; }
  bool operator==(const I& i) const { return pos == i.pos; }
  friend A iter_move(const I&) { return {}; }

  auto operator<=>(const I&) const = default;

  I& operator--() { --pos; return *this; }
  I operator--(int) { I tmp = *this; --pos; return tmp; }
  I& operator+=(int n) { pos += n; return *this; }
  I& operator-=(int n) { pos -= n; return *this; }

  B operator[](int n) const { return *(*this + n); }

  friend I operator+(I i, int n) { return i += n; }
  friend I operator-(I i, int n) { return i -= n; }
  friend I operator+(int n, I i) { return i += n; }
  friend int operator-(I i, I j) { return i.pos - j.pos; }

  int pos;
};

static_assert( std::random_access_iterator<I> );

int main() {
  std::ranges::rotate(I{0}, I{1}, I{2});
}


In file included from /usr/include/c++/15/algorithm:65,
                 from rotate.cc:1:
/usr/include/c++/15/bits/ranges_algo.h: In instantiation of ‘constexpr
std::ranges::subrange<_Iter1> std::ranges::__rotate_fn::operator()(_Iter,
_Iter, _Sent) const [with _Iter = I; _Sent = I]’:
rotate.cc:42:22:   required from here
   42 |   std::ranges::rotate(I{0}, I{1}, I{2});
      |   ~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~
/usr/include/c++/15/bits/ranges_algo.h:1404:44: error: use of deleted function
‘B& B::operator=(const B&)’
 1404 |                           *(__p + __n - 1) = std::move(__t);
      |                           ~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~
rotate.cc:7:6: note: declared here
    7 |   B& operator=(const B&) = delete;
      |      ^~~~~~~~
/usr/include/c++/15/bits/ranges_algo.h:1404:44: note: use
‘-fdiagnostics-all-candidates’ to display considered candidates
 1404 |                           *(__p + __n - 1) = std::move(__t);
      |                           ~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~
/usr/include/c++/15/bits/ranges_algo.h:1430:32: error: use of deleted function
‘B& B::operator=(const B&)’
 1430 |                           *__p = std::move(__t);
      |                           ~~~~~^~~~~~~~~~~~~~~~
rotate.cc:7:6: note: declared here
    7 |   B& operator=(const B&) = delete;
      |      ^~~~~~~~
/usr/include/c++/15/bits/ranges_algo.h:1430:32: note: use
‘-fdiagnostics-all-candidates’ to display considered candidates
 1430 |                           *__p = std::move(__t);
      |                           ~~~~~^~~~~~~~~~~~~~~~