Implemented LWG3919

Author: H-G-Hristov

libcxx/docs/Status/Cxx2cIssues.csv

@@ -41,7 +41,7 @@
 "`LWG4001 <https://wg21.link/LWG4001>`__","``iota_view`` should provide ``empty``","2023-11 (Kona)","|Complete|","19",""
 "","","","","",""
 "`LWG3767 <https://wg21.link/LWG3767>`__","``codecvt<charN_t, char8_t, mbstate_t>`` incorrectly added to locale","2024-03 (Tokyo)","","",""
-"`LWG3919 <https://wg21.link/LWG3919>`__","``enumerate_view`` may invoke UB for sized common non-forward underlying ranges","2024-03 (Tokyo)","","",""
+"`LWG3919 <https://wg21.link/LWG3919>`__","``enumerate_view`` may invoke UB for sized common non-forward underlying ranges","2024-03 (Tokyo)","|Complete|","21",""
 "`LWG3950 <https://wg21.link/LWG3950>`__","``std::basic_string_view`` comparison operators are overspecified","2024-03 (Tokyo)","|Complete|","18",""
 "`LWG3975 <https://wg21.link/LWG3975>`__","Specializations of ``basic_format_context`` should not be permitted","2024-03 (Tokyo)","|Nothing To Do|","",""
 "`LWG3984 <https://wg21.link/LWG3984>`__","``ranges::to``'s recursion branch may be ill-formed","2024-03 (Tokyo)","|Complete|","19",""

libcxx/include/__ranges/enumerate_view.h

@@ -84,15 +84,15 @@ class enumerate_view : public view_interface<enumerate_view<_View>> {
   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto end()
     requires(!__simple_view<_View>)
   {
-    if constexpr (common_range<_View> && sized_range<_View>)
+    if constexpr (forward_range<_View> && common_range<_View> && sized_range<_View>)
       return __iterator<false>(ranges::end(__base_), ranges::distance(__base_));
     else
       return __sentinel<false>(ranges::end(__base_));
   }
   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto end() const
     requires __range_with_movable_references<const _View>
   {
-    if constexpr (common_range<const _View> && sized_range<const _View>)
+    if constexpr (forward_range<_View> && common_range<const _View> && sized_range<const _View>)
       return __iterator<true>(ranges::end(__base_), ranges::distance(__base_));
     else
       return __sentinel<true>(ranges::end(__base_));