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cppdraft/indirect/assign.md
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cppdraft/indirect/assign.md
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[indirect.assign]
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# 20 Memory management library [[mem]](./#mem)
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## 20.4 Types for composite class design [[mem.composite.types]](mem.composite.types#indirect.assign)
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### 20.4.1 Class template indirect [[indirect]](indirect#assign)
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#### 20.4.1.5 Assignment [indirect.assign]
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[ð](#lib:operator=,indirect)
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`constexpr indirect& operator=(const indirect& other);
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`
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[1](#1)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L6358)
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*Mandates*:
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- [(1.1)](#1.1)
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is_copy_assignable_v<T> is true, and
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- [(1.2)](#1.2)
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is_copy_constructible_v<T> is true[.](#1.sentence-1)
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[2](#2)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L6368)
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*Effects*: If addressof(other) == this is true, there are no effects[.](#2.sentence-1)
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Otherwise:
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- [(2.1)](#2.1)
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The allocator needs updating ifallocator_traits<Allocator>::propagate_on_container_copy_assignment::value is true[.](#2.1.sentence-1)
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- [(2.2)](#2.2)
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If other is valueless,*this becomes valueless and
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the owned object in *this, if any,
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is destroyed using allocator_traits<Allocator>::destroy and
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then the storage is deallocated[.](#2.2.sentence-1)
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- [(2.3)](#2.3)
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Otherwise,
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if *alloc* == other.*alloc* is true and*this is not valueless,
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equivalent to **this = *other[.](#2.3.sentence-1)
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- [(2.4)](#2.4)
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Otherwise a new owned object is constructed in *this using allocator_traits<Allocator>::con
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struct with
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the owned object from other as the argument,
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using either the allocator in *this or
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the allocator in other if the allocator needs updating[.](#2.4.sentence-1)
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- [(2.5)](#2.5)
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The previously owned object in *this, if any,
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is destroyed using allocator_traits<Allocator>::
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destroy and
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then the storage is deallocated[.](#2.5.sentence-1)
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- [(2.6)](#2.6)
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If the allocator needs updating,
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the allocator in *this is replaced with
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a copy of the allocator in other[.](#2.6.sentence-1)
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[3](#3)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L6415)
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*Returns*: A reference to *this[.](#3.sentence-1)
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[4](#4)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L6419)
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*Remarks*: If any exception is thrown,
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the result of the expression this->valueless_after_move() remains unchanged[.](#4.sentence-1)
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If an exception is thrown during
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the call to T's selected copy constructor, no effect[.](#4.sentence-2)
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If an exception is thrown during the call to T's copy assignment,
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the state of its owned object
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is as defined by the exception safety guarantee ofT's copy assignment[.](#4.sentence-3)
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[ð](#lib:operator=,indirect_)
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`constexpr indirect& operator=(indirect&& other)
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noexcept(allocator_traits<Allocator>::propagate_on_container_move_assignment::value ||
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allocator_traits<Allocator>::is_always_equal::value);
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`
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[5](#5)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L6440)
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*Mandates*: is_copy_constructible_t<T> is true[.](#5.sentence-1)
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[6](#6)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L6444)
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*Effects*: If addressof(other) == this is true, there are no effects[.](#6.sentence-1)
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Otherwise:
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- [(6.1)](#6.1)
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The allocator needs updating ifallocator_traits<Allocator>::propagate_on_container_move_assignment::value is true[.](#6.1.sentence-1)
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- [(6.2)](#6.2)
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If other is valueless,*this becomes valueless and
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the owned object in *this, if any,
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is destroyed using allocator_traits<Allocator>::destroy and
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then the storage is deallocated[.](#6.2.sentence-1)
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- [(6.3)](#6.3)
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Otherwise,
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if *alloc* == other.*alloc* is true,
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swaps the owned objects in *this and other;
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the owned object in other, if any,
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is then destroyed using allocator_traits<Allocator>::destroy and
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then the storage is deallocated[.](#6.3.sentence-1)
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- [(6.4)](#6.4)
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Otherwise,
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constructs a new owned object with
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the owned object of other as the argument as an rvalue,
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using either
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the allocator in *this or
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the allocator in other if the allocator needs updating[.](#6.4.sentence-1)
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- [(6.5)](#6.5)
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The previously owned object in *this, if any,
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is destroyed using allocator_traits<Allocator>::
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destroy and
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then the storage is deallocated[.](#6.5.sentence-1)
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- [(6.6)](#6.6)
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If the allocator needs updating,
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the allocator in *this is replaced with
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a copy of the allocator in other[.](#6.6.sentence-1)
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[7](#7)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L6493)
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*Postconditions*: other is valueless[.](#7.sentence-1)
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[8](#8)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L6497)
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*Returns*: A reference to *this[.](#8.sentence-1)
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[9](#9)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L6501)
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*Remarks*: If any exception is thrown,
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there are no effects on *this or other[.](#9.sentence-1)
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[ð](#lib:operator=,indirect__)
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`template<class U = T>
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constexpr indirect& operator=(U&& u);
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`
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[10](#10)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L6514)
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*Constraints*:
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- [(10.1)](#10.1)
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is_same_v<remove_cvref_t<U>, indirect> is false,
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- [(10.2)](#10.2)
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is_constructible_v<T, U> is true, and
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- [(10.3)](#10.3)
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is_assignable_v<T&, U> is true[.](#10.sentence-1)
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[11](#11)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L6525)
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*Effects*: If *this is valueless then
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constructs an owned object of type T with std::forward<U>(u) using the allocator *alloc*[.](#11.sentence-1)
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Otherwise,
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equivalent to **this = std::forward<U>(u)[.](#11.sentence-2)
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[12](#12)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/memory.tex#L6533)
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*Returns*: A reference to *this[.](#12.sentence-1)
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