std::expected<T,E>::value

`void`
`constexpr T& value() &;`	(1)	(since C++23)
`constexpr const T& value() const&;`	(2)	(since C++23)
`constexpr T&& value() &&;`	(3)	(since C++23)
`constexpr const T&& value() const&&;`	(4)	(since C++23)
`void`
`constexpr void value() const&;`	(5)	(since C++23)
`constexpr void value() &&;`	(6)	(since C++23)

If *this contains an expected value, returns a reference to the contained value. Returns nothing if T is (possibly cv-qualified) void.

Otherwise, throws an exception of type std::bad_expected_access<std::decay_t<E>> that contains a copy of error().

1,2) If std::is_copy_constructible_v<E> is false, the program is ill-formed.

3,4) If std::is_copy_constructible_v<E> or std::is_constructible_v<E, decltype(std::move(error()))> is false, the program is ill-formed.

5) If std::is_copy_constructible_v<E> is false, the program is ill-formed.

6) If std::is_move_constructible_v<E> is false, the program is ill-formed.

(none)

1-4) The expected value contained in *this.

5,6) (none)

1,2,5) Throws std::bad_expected_access(std::as_const(error())) if *this contains an unexpected value.

3,4,6) Throws std::bad_expected_access(std::move(error())) if *this contains an unexpected value.

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR	Applied to	Behavior as published	Correct behavior
LWG 3940	C++23	`E` was not required to be copy/move-constructible for overloads (5,6)	required

value_or	returns the expected value if present, another value otherwise (public member function)
operator->operator*	accesses the expected value (public member function)
error	returns the unexpected value (public member function)
bad_expected_access (C++23)	exception indicating checked access to an `expected` that contains an unexpected value (class template)

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