meta::dereferenceable

Defined in header <mgs/meta/concepts/dereferenceable.hpp>.

template <typename T>
concept dereferenceable = requires(T& t) {
   { *t } -> /* see below */;
 };

Pre-C++20 implementation of the exposition-only dereferenceable concept.

---

The dereferenceable concept specifies that the type obtained when dereferencing a value of type T is itself referenceable.

Concept emulation

namespace mgs {
namespace meta {

template <typename T>
struct is_dereferenceable { /* ... */ };

template <typename T>
constexpr auto is_dereferenceable_v = is_dereferenceable<T>::value;

template <typename T,
          typename = std::enable_if_t<is_dereferenceable_v<T>>>
using dereferenceable = T;

} // namespace meta
} // namespace mgs

Example

#include <mgs/meta/concepts/dereferenceable.hpp>

using namespace mgs::meta;

struct invalid { void operator*(); };

static_assert(is_dereferenceable_v<int*>, "");
static_assert(!is_dereferenceable_v<void*>, "");
// void cannot be referenced (i.e. void& is ill-formed)
static_assert(!is_dereferenceable_v<invalid>, "");