The following code example is taken from the book
C++ Templates - The Complete Guide, 2nd Edition
by David Vandevoorde, Nicolai M. Josuttis, and Douglas Gregor,
Addison-Wesley, 2017
© Copyright David Vandevoorde, Nicolai M. Josuttis, Douglas Gregor 2017
#include <type_traits> // for true_type, false_type, and void_t
#define DEFINE_HAS_TYPE(MemType) \
template<typename, typename = std::void_t<>> \
struct HasTypeT_##MemType \
: std::false_type { }; \
template<typename T> \
struct HasTypeT_##MemType<T, std::void_t<typename T::MemType>> \
: std::true_type { } // ; intentionally skipped