1 files changed, 60 insertions, 23 deletions

diff --git a/libcxx/test/std/numerics/numeric.ops/inclusive.scan/inclusive_scan_op.pass.cpp b/libcxx/test/std/numerics/numeric.ops/inclusive.scan/inclusive_scan_op.pass.cpp
index 322b502369f3..00092a69317c 100644
--- a/libcxx/test/std/numerics/numeric.ops/inclusive.scan/inclusive_scan_op.pass.cpp
+++ b/libcxx/test/std/numerics/numeric.ops/inclusive.scan/inclusive_scan_op.pass.cpp
@@ -8,7 +8,9 @@
 
 // <numeric>
 // UNSUPPORTED: c++03, c++11, c++14
+// UNSUPPORTED: clang-8
 
+// Became constexpr in C++20
 // template<class InputIterator, class OutputIterator, class T, class BinaryOperation>
 //     OutputIterator
 //     inclusive_scan(InputIterator first, InputIterator last,
@@ -17,6 +19,7 @@
 
 #include <numeric>
 #include <algorithm>
+#include <array>
 #include <cassert>
 #include <functional>
 #include <iterator>
@@ -24,27 +27,43 @@
 
 #include "test_macros.h"
 #include "test_iterators.h"
+// FIXME Remove constexpr vector workaround introduced in D90569
+#if TEST_STD_VER > 17
+#include <span>
+#endif
 
-template <class Iter1, class T, class Op, class Iter2>
-void
+template <class Iter1, class Op, class Iter2>
+TEST_CONSTEXPR_CXX20 void
 test(Iter1 first, Iter1 last, Op op, Iter2 rFirst, Iter2 rLast)
 {
-    std::vector<typename std::iterator_traits<Iter1>::value_type> v;
+    // C++17 doesn't test constexpr so can use a vector.
+    // C++20 can use vector in constexpr evaluation, but both libc++ and MSVC
+    // don't have the support yet. In these cases use a std::span for the test.
+    // FIXME Remove constexpr vector workaround introduced in D90569
+    size_t size = std::distance(first, last);
+#if TEST_STD_VER < 20 || \
+    (defined(__cpp_lib_constexpr_vector) && __cpp_lib_constexpr_vector >= 201907L)
+
+    std::vector<typename std::iterator_traits<Iter1>::value_type> v(size);
+#else
+    assert((size <= 5) && "Increment the size of the array");
+    typename std::iterator_traits<Iter1>::value_type b[5];
+    std::span<typename std::iterator_traits<Iter1>::value_type> v{b, size};
+#endif
 
 //  Not in place
-    std::inclusive_scan(first, last, std::back_inserter(v), op);
+    std::inclusive_scan(first, last, v.begin(), op);
     assert(std::equal(v.begin(), v.end(), rFirst, rLast));
 
 //  In place
-    v.clear();
-    v.assign(first, last);
+    std::copy(first, last, v.begin());
     std::inclusive_scan(v.begin(), v.end(), v.begin(), op);
     assert(std::equal(v.begin(), v.end(), rFirst, rLast));
 }
 
 
 template <class Iter>
-void
+TEST_CONSTEXPR_CXX20 void
 test()
 {
           int ia[]   = {1, 3,  5,   7,   9};
@@ -60,13 +79,14 @@ test()
         }
 }
 
-size_t triangle(size_t n) { return n*(n+1)/2; }
+constexpr size_t triangle(size_t n) { return n*(n+1)/2; }
 
 //  Basic sanity
-void basic_tests()
+TEST_CONSTEXPR_CXX20 void
+basic_tests()
 {
     {
-    std::vector<size_t> v(10);
+    std::array<size_t, 10> v;
     std::fill(v.begin(), v.end(), 3);
     std::inclusive_scan(v.begin(), v.end(), v.begin(), std::plus<>());
     for (size_t i = 0; i < v.size(); ++i)
@@ -74,7 +94,7 @@ void basic_tests()
     }
 
     {
-    std::vector<size_t> v(10);
+    std::array<size_t, 10> v;
     std::iota(v.begin(), v.end(), 0);
     std::inclusive_scan(v.begin(), v.end(), v.begin(), std::plus<>());
     for (size_t i = 0; i < v.size(); ++i)
@@ -82,7 +102,7 @@ void basic_tests()
     }
 
     {
-    std::vector<size_t> v(10);
+    std::array<size_t, 10> v;
     std::iota(v.begin(), v.end(), 1);
     std::inclusive_scan(v.begin(), v.end(), v.begin(), std::plus<>());
     for (size_t i = 0; i < v.size(); ++i)
@@ -90,26 +110,43 @@ void basic_tests()
     }
 
     {
+    // C++17 doesn't test constexpr so can use a vector.
+    // C++20 can use vector in constexpr evaluation, but both libc++ and MSVC
+    // don't have the support yet. In these cases use a std::span for the test.
+    // FIXME Remove constexpr vector workaround introduced in D90569
+#if TEST_STD_VER < 20 || \
+    (defined(__cpp_lib_constexpr_vector) && __cpp_lib_constexpr_vector >= 201907L)
     std::vector<size_t> v, res;
     std::inclusive_scan(v.begin(), v.end(), std::back_inserter(res), std::plus<>());
+#else
+    std::array<size_t, 0> v, res;
+    std::inclusive_scan(v.begin(), v.end(), res.begin(), std::plus<>());
+#endif
     assert(res.empty());
     }
 }
 
-
-int main(int, char**)
+TEST_CONSTEXPR_CXX20 bool
+test()
 {
-
     basic_tests();
 
 //  All the iterator categories
-//     test<input_iterator        <const int*> >();
-//     test<forward_iterator      <const int*> >();
-//     test<bidirectional_iterator<const int*> >();
-//     test<random_access_iterator<const int*> >();
-//     test<const int*>();
-//     test<      int*>();
-
+    test<input_iterator        <const int*> >();
+    test<forward_iterator      <const int*> >();
+    test<bidirectional_iterator<const int*> >();
+    test<random_access_iterator<const int*> >();
+    test<const int*>();
+    test<      int*>();
+
+    return true;
+}
 
-  return 0;
+int main(int, char**)
+{
+    test();
+#if TEST_STD_VER > 17
+    static_assert(test());
+#endif
+    return 0;
 }