22 General utilities library [utilities]

22.8 Expected objects [expected]

22.8.6 Class template expected [expected.expected]

22.8.6.7 Equality operators [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);
Mandates: 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);
Mandates: The expression *x == v is well-formed and its result is convertible to bool.
[Note 1:
T1 need not be Cpp17EqualityComparable.
— end note]
Returns: x.has_­value() && static_­cast<bool>(*x == v).
template<class E2> friend constexpr bool operator==(const expected& x, const unexpected<E2>& e);
Mandates: The expression x.error() == e.value() is well-formed and its result is convertible to bool.
Returns: !x.has_­value() && static_­cast<bool>(x.error() == e.value()).