LWG-3847 ranges::to can still return views (#3479)

Co-authored-by: Stephan T. Lavavej <[email protected]>

stl/inc/ranges

@@ -8402,6 +8402,9 @@ namespace ranges {
     _EXPORT_STD template <class _Container, input_range _Rng, class... _Types>
         requires (!view<_Container>)
     _NODISCARD constexpr _Container to(_Rng&& _Range, _Types&&... _Args) {
+        static_assert(!is_const_v<_Container>, "C must not be const. ([range.utility.conv.to])");
+        static_assert(!is_volatile_v<_Container>, "C must not be volatile. ([range.utility.conv.to])");
+        static_assert(is_class_v<_Container>, "C must be a class type. ([range.utility.conv.to])");
         if constexpr (_Converts_direct_constructible<_Rng, _Container, _Types...>) {
             return _Container(_STD forward<_Rng>(_Range), _STD forward<_Types>(_Args)...);
         } else if constexpr (_Converts_tag_constructible<_Rng, _Container, _Types...>) {
@@ -8427,6 +8430,9 @@ namespace ranges {
 
     template <class _Container>
     struct _To_class_fn {
+        _STL_INTERNAL_STATIC_ASSERT(!is_const_v<_Container>);
+        _STL_INTERNAL_STATIC_ASSERT(!is_volatile_v<_Container>);
+        _STL_INTERNAL_STATIC_ASSERT(is_class_v<_Container>);
         _STL_INTERNAL_STATIC_ASSERT(!view<_Container>);
 
         template <input_range _Rng, class... _Types>
@@ -8440,6 +8446,9 @@ namespace ranges {
     _EXPORT_STD template <class _Container, class... _Types>
         requires (!view<_Container>)
     _NODISCARD constexpr auto to(_Types&&... _Args) {
+        static_assert(!is_const_v<_Container>, "C must not be const. ([range.utility.conv.adaptors])");
+        static_assert(!is_volatile_v<_Container>, "C must not be volatile. ([range.utility.conv.adaptors])");
+        static_assert(is_class_v<_Container>, "C must be a class type. ([range.utility.conv.adaptors])");
         return _Range_closure<_To_class_fn<_Container>, decay_t<_Types>...>{_STD forward<_Types>(_Args)...};
     }