Class has_get

tests/test_container_helpers.h:130–135

// Detect if type has get() method (smart pointers)
template<typename T>
class has_get {
    template<typename C> static auto test(int) -> decltype(fl::declval<C>().get(), fl::true_type());
    template<typename> static fl::false_type test(...);
public:
    static constexpr bool value = fl::is_same<decltype(test<T>(0)), fl::true_type>::value;
};

// Detect if type has pop(T&) method (circular buffers)
template<typename T>