From 1dd1320c8b29099fe5bba591d1b0dba367fa68d7 Mon Sep 17 00:00:00 2001
From: Jordan Maples <jomaples@microsoft.com>
Date: Tue, 17 Mar 2020 13:53:13 -0700
Subject: [PATCH] test commit to get extra eyes on the problem

---
 include/gsl/span                   | 18 ++++++++++++++++++
 tests/span_compatibility_tests.cpp | 16 ++++++++++++++++
 2 files changed, 34 insertions(+)

diff --git a/include/gsl/span b/include/gsl/span
index 23c58c9..7c15eb4 100644
--- a/include/gsl/span
+++ b/include/gsl/span
@@ -441,6 +441,8 @@ public:
         : storage_(KnownNotNull{arr + 0}, details::extent_type<N>())
     {}
 
+// #define useold
+#if defined(useold)
     template <std::size_t N,
               std::enable_if_t<details::is_allowed_extent_conversion<N, Extent>::value, int> = 0>
     constexpr span(std::array<element_type, N>& arr) noexcept
@@ -455,7 +457,23 @@ public:
     constexpr span(const std::array<value_type, N>& arr) noexcept
         : storage_(KnownNotNull{arr.data()}, details::extent_type<N>())
     {}
+#else
+    template <class T, std::size_t N,
+              std::enable_if_t<(details::is_allowed_extent_conversion<N, Extent>::value &&
+                                details::is_allowed_element_type_conversion<T, element_type>::value), int> = 0>
+    constexpr span(std::array<T, N>& arr) noexcept
+        : storage_(KnownNotNull{arr.data()}, details::extent_type<N>())
+    {}
 
+    template <class T, std::size_t N,
+              std::enable_if_t<(details::is_allowed_extent_conversion<N, Extent>::value &&
+                                details::is_allowed_element_type_conversion<const T,
+                                                                            element_type>::value),
+                               int> = 0>
+    constexpr span(const std::array<T, N>& arr) noexcept
+        : storage_(KnownNotNull{arr.data()}, details::extent_type<N>())
+    {}
+#endif
     // NB: the SFINAE here uses .data() as an incomplete/imperfect proxy for the requirement
     // on Container to be a contiguous sequence container.
     template <class Container,
diff --git a/tests/span_compatibility_tests.cpp b/tests/span_compatibility_tests.cpp
index 8733e72..1985f6f 100644
--- a/tests/span_compatibility_tests.cpp
+++ b/tests/span_compatibility_tests.cpp
@@ -46,6 +46,22 @@ TEST(span_compatibility_tests, assertion_tests)
 {
     int arr[3]{10, 20, 30};
     std::array<int, 3> stl{{100, 200, 300}};
+    std::array<int*, 3> stl_nullptr{{nullptr,nullptr,nullptr}};
+
+    {
+        gsl::span<const int* const> sp_const_nullptr_1{stl_nullptr};
+        EXPECT_TRUE(sp_const_nullptr_1.data() == stl_nullptr.data());
+        EXPECT_TRUE(sp_const_nullptr_1.size() == 3);
+
+#if __cplusplus >= 201703l
+        span<const int* const> sp_const_nullptr_2{std::as_const(stl_nullptr)};
+        EXPECT_TRUE(sp_const_nullptr_2.data() == stl_nullptr.data());
+        EXPECT_TRUE(sp_const_nullptr_2.size() == 3);
+
+        static_assert(std::is_same<decltype(span{stl_nullptr}), span<int*, 3>);
+        static_assert(std::is_same<decltype(span{std::as_const(stl_nullptr)}), span<int* const, 3>);
+#endif
+    }
 
     {
         gsl::span<int> sp_dyn;