libstdc++: Add code comment documenting LWG 4027 change [PR118083]

	PR libstdc++/118083

libstdc++-v3/ChangeLog:

	* include/bits/ranges_base.h
	(ranges::__access::__possibly_const_range): Mention LWG 4027.

(cherry picked from commit 640697f7c2def415db81c84010ae25be0785d867)

diff --git a/libstdc++-v3/include/bits/ranges_base.h b/libstdc++-v3/include/bits/ranges_base.h
index 481d9bb5c5d5fd3a20d8bc771c15af38a9743a4d..eafd982f48e28c298d14e29ffcbc14546a8a4ffe 100644 (file)
--- a/libstdc++-v3/include/bits/ranges_base.h
+++ b/libstdc++-v3/include/bits/ranges_base.h
@@ -635,6 +635,8 @@ namespace ranges
       constexpr auto&
       __possibly_const_range(_Range& __r) noexcept
       {
+       // _GLIBCXX_RESOLVE_LIB_DEFECTS
+       // 4027. possibly-const-range should prefer returning const R&
        if constexpr (input_range<const _Range>)
          return const_cast<const _Range&>(__r);
        else