Implement LWG-3860 range_common_reference_t is missing (#3480)

Co-authored-by: Jakub Mazurkiewicz <[email protected]>
microsoft · Feb 23, 2023 · 7aaa151 · 7aaa151
1 parent 1bddf4c
commit 7aaa151
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diff --git a/stl/inc/xutility b/stl/inc/xutility
@@ -2459,6 +2459,9 @@ namespace ranges {
     _EXPORT_STD template <range _Rng>
     using range_rvalue_reference_t = iter_rvalue_reference_t<iterator_t<_Rng>>;
 
+    _EXPORT_STD template <range _Rng>
+    using range_common_reference_t = iter_common_reference_t<iterator_t<_Rng>>;
+
 #if _HAS_CXX23
     _EXPORT_STD template <class _Rng>
     concept constant_range = input_range<_Rng> && _Constant_iterator<iterator_t<_Rng>>;

diff --git a/tests/std/tests/P0896R4_ranges_range_machinery/test.cpp b/tests/std/tests/P0896R4_ranges_range_machinery/test.cpp
@@ -399,6 +399,12 @@ constexpr bool test_input_range() {
     STATIC_ASSERT(std::same_as<ranges::range_rvalue_reference_t<Range&>, RvalueReference>);
     STATIC_ASSERT(std::same_as<ranges::range_rvalue_reference_t<Range&&>, RvalueReference>);
 
+    // LWG-3860, validate ranges::range_common_reference_t
+    using CommonReference = std::iter_common_reference_t<Iterator>;
+    STATIC_ASSERT(std::same_as<ranges::range_common_reference_t<Range>, CommonReference>);
+    STATIC_ASSERT(std::same_as<ranges::range_common_reference_t<Range&>, CommonReference>);
+    STATIC_ASSERT(std::same_as<ranges::range_common_reference_t<Range&&>, CommonReference>);
+
     return true;
 }