meta::constructible_from¶
Defined in header <mgs/meta/concepts/constructible_from.hpp>.
template <typename T, typename... Args>
concept constructible_from =
meta::destructible<T> &&
std::is_constructible_v<T, Args...>;
Pre-C++20 implementation of the std::constructible_from concept.
Differences with the C++20 version¶
Checks template arguments before calling std::is_constructible_v, which is not SFINAE-friendly.
Concept emulation¶
namespace mgs {
namespace meta {
template <typename T, typename... Args>
struct is_constructible_from { /* ... */ };
template <typename T, typename... Args>
constexpr auto is_constructible_from_v = is_constructible_from<T, Args...>::value;
} // namespace meta
} // namespace mgs
Note
Unlike other concept emulations, there is no constructible_from alias because of the template parameter pack.
Example¶
#include <mgs/meta/concepts/constructible_from.hpp>
using namespace mgs::meta;
static_assert(is_constructible_from_v<int>, "");
static_assert(is_constructible_from_v<std::string, std::string const&>, "");
static_assert(is_constructible_from_v<std::string, int, int, int, int>, "");
static_assert(!is_constructible_from_v<int, void>, "");