[Bug libstdc++/100833] New: ranges::advance should return n when i == bound

[hewillk at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100833

            Bug ID: 100833
           Summary: ranges::advance should return n when i == bound
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: hewillk at gmail dot com
  Target Milestone: ---

This is specified in [range.iter.op.advance#7]:
"Returns: n - M, where M is the difference between the ending and starting
positions of i."


#include <ranges>

constexpr auto diff = [] {
  auto r = std::views::single(0) | 
           std::views::filter([](int) { return true; });
  auto it = r.begin();
  return std::ranges::advance(it, 100, r.begin());
}();

static_assert(diff == 100);

https://godbolt.org/z/6nh8xMWYd