🔊 add test for type traits

include/nlohmann/detail/input/lexer.hpp

@@ -13,6 +13,7 @@
 #include <nlohmann/detail/input/input_adapters.hpp>
 #include <nlohmann/detail/input/position_t.hpp>
 #include <nlohmann/detail/macro_scope.hpp>
+#include <nlohmann/detail/meta/type_traits.hpp>
 
 namespace nlohmann
 {
@@ -918,10 +919,6 @@ class lexer : public lexer_base<BasicJsonType>
         f = std::strtold(str, endptr);
     }
 
-    template<typename NumberType>
-    struct is_64_bit : std::integral_constant < bool, (sizeof(NumberType) <= 8) >
-    {};
-
     JSON_HEDLEY_NON_NULL(2)
     unsigned long long strtoull(const char* str, char** str_end, std::true_type)
     {