test.cpp: In instantiation of ‘T add(T, T) [with T = std::basic_string<char>]’:
test.cpp:17:21: required from here
test.cpp:11:22: error: static assertion failed
11 | static_assert(std::is_integral_v<T>);
| ~~~~~^~~~~~~~~~~~~~~~
test.cpp:11:22: note: ‘std::is_integral_v<std::basic_string<char> >’ evaluates to false