msvc checks ambiguous void_t

Author: Werner Henze

tests/span_compatibility_tests.cpp

@@ -1004,7 +1004,9 @@ 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
+#if __cplusplus >= 201703l
+using std::void_t;
+#else  // __cplusplus >= 201703l
 template <class...>
 using void_t = void;
 #endif // __cplusplus < 201703l
@@ -1014,7 +1016,7 @@ static constexpr bool AsWritableBytesCompilesFor = false;
 
 template <typename U>
 static constexpr bool
-    AsWritableBytesCompilesFor<U, void_t<decltype(as_writable_bytes(declval<U>()))>> = true;
+    AsWritableBytesCompilesFor<U, ::void_t<decltype(as_writable_bytes(declval<U>()))>> = true;
 
 static_assert(AsWritableBytesCompilesFor<gsl::span<int>>,
               "AsWritableBytesCompilesFor<gsl::span<int>>");