[expected.void.assign]

# 22 General utilities library [[utilities]](./#utilities)

## 22.8 Expected objects [[expected]](expected#void.assign)

### 22.8.7 Partial specialization of expected for void types [[expected.void]](expected.void#assign)

#### 22.8.7.4 Assignment [expected.void.assign]

[🔗](#lib:operator=,expected%3cvoid%3e)

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

[1](#1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L9771)

*Effects*: 

- [(1.1)](#1.1)

  If this->has_value() && rhs.has_value() is true, no effects[.](#1.1.sentence-1)

- [(1.2)](#1.2)

  Otherwise, if this->has_value() is true,
equivalent to: construct_at(addressof(*unex*), rhs.*unex*); *has_val* = false;

- [(1.3)](#1.3)

  Otherwise, if rhs.has_value() is true,
destroys *unex* and sets *has_val* to true[.](#1.3.sentence-1)

- [(1.4)](#1.4)

  Otherwise, equivalent to *unex* = rhs.error()[.](#1.4.sentence-1)

[2](#2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L9786)

*Returns*: *this[.](#2.sentence-1)

[3](#3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L9790)

*Remarks*: This operator is defined as deleted unlessis_copy_assignable_v<E> is true andis_copy_constructible_v<E> is true[.](#3.sentence-1)

[🔗](#lib:operator=,expected%3cvoid%3e_)

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

[4](#4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L9803)

*Constraints*: is_move_constructible_v<E> is true andis_move_assignable_v<E> is true[.](#4.sentence-1)

[5](#5)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L9808)

*Effects*: 

- [(5.1)](#5.1)

  If this->has_value() && rhs.has_value() is true, no effects[.](#5.1.sentence-1)

- [(5.2)](#5.2)

  Otherwise, if this->has_value() is true, equivalent to:construct_at(addressof(*unex*), std::move(rhs.*unex*));*has_val* = false;

- [(5.3)](#5.3)

  Otherwise, if rhs.has_value() is true,
destroys *unex* and sets *has_val* to true[.](#5.3.sentence-1)

- [(5.4)](#5.4)

  Otherwise, equivalent to *unex* = std​::​move(rhs.error())[.](#5.4.sentence-1)

[6](#6)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L9826)

*Returns*: *this[.](#6.sentence-1)

[7](#7)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L9830)

*Remarks*: The exception specification is equivalent tois_nothrow_move_constructible_v<E> && is_nothrow_move_assignable_v<E>[.](#7.sentence-1)

[🔗](#lib:operator=,expected%3cvoid%3e__)

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

[8](#8)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L9845)

Let GF be const G& for the first overload andG for the second overload[.](#8.sentence-1)

[9](#9)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L9849)

*Constraints*: is_constructible_v<E, GF> is true andis_assignable_v<E&, GF> is true[.](#9.sentence-1)

[10](#10)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L9854)

*Effects*: 

- [(10.1)](#10.1)

If has_value() is true, equivalent to:construct_at(addressof(*unex*), std::forward<GF>(e.error()));*has_val* = false;

- [(10.2)](#10.2)

Otherwise, equivalent to:*unex* = std​::​forward<GF>(e.error());

[11](#11)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L9868)

*Returns*: *this[.](#11.sentence-1)

[🔗](#lib:emplace,expected%3cvoid%3e)

`constexpr void emplace() noexcept;
`

[12](#12)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L9879)

*Effects*: If has_value() is false,
destroys *unex* and sets *has_val* to true[.](#12.sentence-1)