#include <di/meta/relation.h>
template<typename R, typename T, typename U T>
detail::InvocableToComparisonCategory<R, T, T> && detail::InvocableToComparisonCategory<R, T, U> &&
detail::InvocableToComparisonCategory<R, U, T> && detail::InvocableToComparisonCategory<R, U, U>