[expected.object.eq]

template<class T2, class E2> requires (!is_void_v<T2>)
  friend constexpr bool operator=(const expected& x, const expected<T2, E2>& y);

Constraints: The expressions *x == *y and x.error() == y.error() are well-formed and their results are convertible to bool.

Returns: If x.has_value() does not equal y.has_value(), false; otherwise if x.has_value() is true, *x == *y; otherwise x.error() == y.error().

template<class T2> friend constexpr bool operator=(const expected& x, const T2& v);

Constraints: T2 is not a specialization of expected.

The expression *x == v is well-formed and its result is convertible to bool.

[Note 1:

— end note]

Returns: If x.has_value() is true, *x == v; otherwise false.

template<class E2> friend constexpr bool operator=(const expected& x, const unexpected<E2>& e);

Constraints: The expression x.error() == e.error() is well-formed and its result is convertible to bool.

Returns: If x.has_value() is true, x.error() == e.error(); otherwise false.

22 General utilities library [utilities]