[expected.object.assign]

🔗

constexpr expected& operator=(const expected& rhs);

Effects:

(2.1)
If this->has_value() && rhs.has_value() is true, equivalent to val = *rhs.
(2.2)
Otherwise, if this->has_value() is true, equivalent to: reinit-expected(unex, val, rhs.error()
(2.3)
Otherwise, if rhs.has_value() is true, equivalent to: reinit-expected(val, unex, *rhs)
(2.4)
Otherwise, equivalent to unex = rhs.error().

Then, if no exception was thrown, equivalent to: has_val = rhs.has_value(); return *this;

Remarks: This operator is defined as deleted unless:

(4.1)
is_copy_assignable_v<T> is true and
(4.2)
is_copy_constructible_v<T> is true and
(4.3)
is_copy_assignable_v<E> is true and
(4.4)
is_copy_constructible_v<E> is true and
(4.5)
is_nothrow_move_constructible_v<T> || is_nothrow_move_constructible_v<E> is true.

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constexpr expected& operator=(expected&& rhs) noexcept(see below);

Constraints:

(5.1)
is_move_constructible_v<T> is true and
(5.2)
is_move_assignable_v<T> is true and
(5.3)
is_move_constructible_v<E> is true and
(5.4)
is_move_assignable_v<E> is true and
(5.5)
is_nothrow_move_constructible_v<T> || is_nothrow_move_constructible_v<E> is true.

Effects:

(6.1)
If this->has_value() && rhs.has_value() is true, equivalent to val = std::move(*rhs).
(6.2)
Otherwise, if this->has_value() is true, equivalent to: reinit-expected(unex, val, std::move(rhs.error()
(6.3)
Otherwise, if rhs.has_value() is true, equivalent to: reinit-expected(val, unex, std::move(*rhs))
(6.4)
Otherwise, equivalent to unex = std::move(rhs.error().

Then, if no exception was thrown, equivalent to: has_val = rhs.has_value(); return *this;

Remarks: The exception specification is equivalent to: is_nothrow_move_assignable_v<T> && is_nothrow_move_constructible_v<T> && is_nothrow_move_assignable_v<E> && is_nothrow_move_constructible_v<E>

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template<class U = remove_cv_t<T>>
  constexpr expected& operator=(U&& v);

Constraints:

(9.1)
is_same_v<expected, remove_cvref_t> is false; and
(9.2)
remove_cvref_t is not a specialization of unexpected; and
(9.3)
is_constructible_v<T, U> is true; and
(9.4)
is_assignable_v<T&, U> is true; and
(9.5)
is_nothrow_constructible_v<T, U> || is_nothrow_move_constructible_v<T> ||
is_nothrow_move_constructible_v<E> is true.

Effects:

(10.1)
If has_value() is true, equivalent to: val = std::forward(v);
(10.2)
Otherwise, equivalent to: reinit-expected(val, unex, std::forward(v)); has_val = true;

Returns: *this.

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template<class G>
  constexpr expected& operator=(const unexpected<G>& e);
template<class G>
  constexpr expected& operator=(unexpected<G>& e);

Let GF be const G& for the first overload and G for the second overload.

Effects:

(14.1)
If has_value() is true, equivalent to: reinit-expected(unex, val, std::forward<GF>(e.error(); has_val = false;
(14.2)
Otherwise, equivalent to: unex = std::forward<GF>(e.error();

Returns: *this.

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template<class. Args>
  constexpr T& emplace(Args&&. args) noexcept;

Effects: Equivalent to: if (has_value() { destroy_at(addressof(val)); } else { destroy_at(addressof(unex)); has_val = true; } return *construct_at(addressof(val), std::forward<Args>(args).);

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template<class U, class. Args>
  constexpr T& emplace(initializer_list<U> il, Args&&. args) noexcept;

Constraints: is_nothrow_constructible_v<T, initializer_list&, Args..> is true.