[committed] libstdc++: Implement LWG 3490 change to drop_while_view::begin()

[Patrick Palka via Gcc-patches]

Tested on x86_64-pc-linux-gnu, committed to trunk as obvious.

libstdc++-v3/ChangeLog:

        PR libstdc++/100606
        * include/std/ranges (drop_while_view::begin): Assert the
        precondition added by LWG 3490.
---
 libstdc++-v3/include/std/ranges | 1 +
 1 file changed, 1 insertion(+)

diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges
index 767a65c5822..76add252ca6 100644
--- a/libstdc++-v3/include/std/ranges
+++ b/libstdc++-v3/include/std/ranges
@@ -2190,6 +2190,7 @@ namespace views::__adaptor
        if (_M_cached_begin._M_has_value())
          return _M_cached_begin._M_get(_M_base);
 
+       __glibcxx_assert(_M_pred.has_value());
        auto __it = __detail::find_if_not(ranges::begin(_M_base),
                                          ranges::end(_M_base),
                                          std::cref(*_M_pred));
-- 
2.32.0.rc0