#include <iostream>

template<typename T>
concept Printable = requires(T a) {
  std::cout << a;
};

template<typename T>
struct printable
{
  enum {value = Printable<T>};
};

template<typename T>
constexpr bool printable_v = printable<T>::value;

template<typename T>
void check_printable(T value)
{
  if constexpr (printable_v<T>) {
    std::cout << typeid(T).name() << " is a printable type";
  } else
  {
    std::cout << typeid(T).name() << " is not a printable type";
  }
}
struct foo {};

int main() {
  check_printable(10);
  check_printable(foo());
}