Correct test for, and use of, concepts for numeric_limits

Author: rollbear

ChangeLog

@@ -1,3 +1,7 @@
+        * Corrected the test for, and use of, concepts when specializing
+          std::numeric_limits<> for strong::arithmetic types. Thank you
+          Björn Schäpers for reporting.
+
 v9 2023-01-23
 
         * Lowered the minimum required CMake version to 3.7, unless unit-tests

include/strong_type/arithmetic.hpp

@@ -166,11 +166,12 @@ class arithmetic::modifier
 }
 
 template <typename T, typename Tag, typename ... Ms>
+#if defined(__cpp_concepts)
+requires strong::type_is_v<strong::type<T, Tag, Ms...>, strong::arithmetic>
 class std::numeric_limits<strong::type<T, Tag, Ms...>>
-#if __cplusplus >= 202003L
-    requires strong::type_is<strong::type<T, Tag, Ms...>, strong::arithmetic>
-        : public std::numeric_limits<T>
+    : public std::numeric_limits<T>
 #else
+class std::numeric_limits<strong::type<T, Tag, Ms...>>
     : public std::conditional<
         strong::type_is_v<strong::type<T, Tag, Ms...>, strong::arithmetic>,
         std::numeric_limits<T>,

test/test.cpp

@@ -147,6 +147,11 @@ using uint = unsigned int;
 using handle = strong::type<int, struct handle_tag>;
 
 static_assert(!std::numeric_limits<handle>::is_specialized, "");
+#if defined(__cpp_concepts)
+static_assert(!std::is_base_of<std::numeric_limits<void>, std::numeric_limits<handle>>{},"");
+#else
+static_assert(std::is_base_of<std::numeric_limits<void>, std::numeric_limits<handle>>{},"");
+#endif
 static_assert(std::is_same<int, strong::underlying_type_t<handle>>{},"");
 static_assert(std::is_same<int, strong::underlying_type_t<int>>{},"");