std::unexpect_t, std::unexpect

std::unexpect_t, std::unexpect - cppreference.com

From cppreference.com

Defined in header `<expected>`
`struct unexpect_t { explicit unexpect_t() = default; };`	(1)	(since C++23)
`inline constexpr std::unexpect_t unexpect{};`	(2)	(since C++23)

1) A tag type for in-place construction of an unexpected value in an std::expected object.

2) A constant of type const std::unexpect_t which is usually directly passed to a constructor of std::expected to construct an unexpected value.

Like other construction tag types, unexpect_t is a trivial, empty class with an explicit default constructor.