From 6b01a0488b1157a2c49805b85becd09e1fe84f57 Mon Sep 17 00:00:00 2001
From: "Jordan Maples [MSFT]" <49793787+JordanMaples@users.noreply.github.com>
Date: Fri, 14 Feb 2020 16:25:25 -0800
Subject: [PATCH] Update span_compatibility_tests.cpp

some fixes.
---
 tests/span_compatibility_tests.cpp | 35 ++++++++++++++++--------------
 1 file changed, 19 insertions(+), 16 deletions(-)

diff --git a/tests/span_compatibility_tests.cpp b/tests/span_compatibility_tests.cpp
index d4cde0c..57a85e7 100644
--- a/tests/span_compatibility_tests.cpp
+++ b/tests/span_compatibility_tests.cpp
@@ -41,13 +41,6 @@ static_assert(std::is_convertible<Derived*, Base*>::value, "std::is_convertible<
 static_assert(!std::is_convertible<Derived (*)[], Base (*)[]>::value,
               "!std::is_convertible<Derived(*)[], Base(*)[]>");
 
-template <typename U, typename = void>
-static constexpr bool AsWritableBytesCompilesFor = false;
-
-template <typename U>
-static constexpr bool AsWritableBytesCompilesFor<U, void_t<decltype(as_writable_bytes(declval<U>()))>> =
-    true;
-
 TEST(span_compatibility_tests, assertion_tests)
 {
     int arr[3]{10, 20, 30};
@@ -501,15 +494,6 @@ TEST(span_compatibility_tests, assertion_tests)
         static_assert(noexcept(as_writable_bytes(sp_dyn)), "noexcept(as_writable_bytes(sp_dyn))");
         static_assert(noexcept(as_writable_bytes(sp_nine)), "noexcept(as_writable_bytes(sp_nine))");
 
-        static_assert(AsWritableBytesCompilesFor<gsl::span<int>>,
-                      "AsWritableBytesCompilesFor<gsl::span<int>>");
-        static_assert(AsWritableBytesCompilesFor<gsl::span<int, 9>>,
-                      "AsWritableBytesCompilesFor<gsl::span<int, 9>>");
-        static_assert(!AsWritableBytesCompilesFor<gsl::span<const int>>,
-                      "!AsWritableBytesCompilesFor<gsl::span<const int>>");
-        static_assert(!AsWritableBytesCompilesFor<gsl::span<const int, 9>>,
-                      "!AsWritableBytesCompilesFor<gsl::span<const int, 9>>");
-
         auto sp_1 = as_bytes(sp_dyn);
         auto sp_2 = as_bytes(sp_nine);
         auto sp_3 = as_bytes(sp_const_dyn);
@@ -1064,3 +1048,22 @@ static_assert(std::is_convertible<std::array<int, 3>&, gsl::span<const int>>::va
 
 static_assert(std::is_convertible<const std::array<int, 3>&, gsl::span<const int>>::value,
               "std::is_convertible<const std::array<int, 3>&, gsl::span<const int>>");
+              
+              
+#if __cplusplus >= 201703l
+template <typename U, typename = void>
+inline constexpr bool AsWritableBytesCompilesFor = false;
+
+template <typename U>
+inline constexpr bool AsWritableBytesCompilesFor<U, void_t<decltype(as_writable_bytes(declval<U>()))>> =
+    true;
+        
+static_assert(AsWritableBytesCompilesFor<gsl::span<int>>,
+                "AsWritableBytesCompilesFor<gsl::span<int>>");
+static_assert(AsWritableBytesCompilesFor<gsl::span<int, 9>>,
+                "AsWritableBytesCompilesFor<gsl::span<int, 9>>");
+static_assert(!AsWritableBytesCompilesFor<gsl::span<const int>>,
+                "!AsWritableBytesCompilesFor<gsl::span<const int>>");
+static_assert(!AsWritableBytesCompilesFor<gsl::span<const int, 9>>,
+                "!AsWritableBytesCompilesFor<gsl::span<const int, 9>>");
+#endif // __cplusplus >= 201703l