<!DOCTYPE html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta name="generator" content="rustdoc"><meta name="description" content="Source to the Rust file `libcore/mem.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>mem.rs.html -- source</title><link rel="stylesheet" type="text/css" href="../../normalize.css"><link rel="stylesheet" type="text/css" href="../../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" type="text/css" href="../../dark.css"><link rel="stylesheet" type="text/css" href="../../light.css" id="themeStyle"><script src="../../storage.js"></script><link rel="shortcut icon" href="https://doc.rust-lang.org/favicon.ico"></head><body class="rustdoc source"><!--[if lte IE 8]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><div class="sidebar-menu">☰</div><a href='../../core/index.html'><img src='https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png' alt='logo' width='100'></a></nav><div class="theme-picker"><button id="theme-picker" aria-label="Pick another theme!"><img src="../../brush.svg" width="18" alt="Pick another theme!"></button><div id="theme-choices"></div></div><script src="../../theme.js"></script><nav class="sub"><form class="search-form js-only"><div class="search-container"><input class="search-input" name="search" autocomplete="off" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><a id="settings-menu" href="../../settings.html"><img src="../../wheel.svg" width="18" alt="Change settings"></a></div></form></nav><section id="main" class="content"><pre class="line-numbers"><span id="1"> 1</span>
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</pre><pre class="rust ">
<span class="comment">// Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT</span>
<span class="comment">// file at the top-level directory of this distribution and at</span>
<span class="comment">// http://rust-lang.org/COPYRIGHT.</span>
<span class="comment">//</span>
<span class="comment">// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or</span>
<span class="comment">// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license</span>
<span class="comment">// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your</span>
<span class="comment">// option. This file may not be copied, modified, or distributed</span>
<span class="comment">// except according to those terms.</span>
<span class="doccomment">//! Basic functions for dealing with memory.</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! This module contains functions for querying the size and alignment of</span>
<span class="doccomment">//! types, initializing and manipulating memory.</span>
<span class="attribute">#![<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">use</span> <span class="ident">clone</span>;
<span class="kw">use</span> <span class="ident">cmp</span>;
<span class="kw">use</span> <span class="ident">fmt</span>;
<span class="kw">use</span> <span class="ident">hash</span>;
<span class="kw">use</span> <span class="ident">intrinsics</span>;
<span class="kw">use</span> <span class="ident">marker</span>::{<span class="ident">Copy</span>, <span class="ident">PhantomData</span>, <span class="ident">Sized</span>, <span class="ident">Unpin</span>, <span class="ident">Unsize</span>};
<span class="kw">use</span> <span class="ident">ptr</span>;
<span class="kw">use</span> <span class="ident">ops</span>::{<span class="ident">Deref</span>, <span class="ident">DerefMut</span>, <span class="ident">CoerceUnsized</span>};
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">use</span> <span class="ident">intrinsics</span>::<span class="ident">transmute</span>;
<span class="doccomment">/// Leaks a value: takes ownership and "forgets" about the value **without running</span>
<span class="doccomment">/// its destructor**.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Any resources the value manages, such as heap memory or a file handle, will linger</span>
<span class="doccomment">/// forever in an unreachable state.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// If you want to dispose of a value properly, running its destructor, see</span>
<span class="doccomment">/// [`mem::drop`][drop].</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Safety</span>
<span class="doccomment">///</span>
<span class="doccomment">/// `forget` is not marked as `unsafe`, because Rust's safety guarantees</span>
<span class="doccomment">/// do not include a guarantee that destructors will always run. For example,</span>
<span class="doccomment">/// a program can create a reference cycle using [`Rc`][rc], or call</span>
<span class="doccomment">/// [`process::exit`][exit] to exit without running destructors. Thus, allowing</span>
<span class="doccomment">/// `mem::forget` from safe code does not fundamentally change Rust's safety</span>
<span class="doccomment">/// guarantees.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// That said, leaking resources such as memory or I/O objects is usually undesirable,</span>
<span class="doccomment">/// so `forget` is only recommended for specialized use cases like those shown below.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Because forgetting a value is allowed, any `unsafe` code you write must</span>
<span class="doccomment">/// allow for this possibility. You cannot return a value and expect that the</span>
<span class="doccomment">/// caller will necessarily run the value's destructor.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [rc]: ../../std/rc/struct.Rc.html</span>
<span class="doccomment">/// [exit]: ../../std/process/fn.exit.html</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Leak some heap memory by never deallocating it:</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use std::mem;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let heap_memory = Box::new(3);</span>
<span class="doccomment">/// mem::forget(heap_memory);</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Leak an I/O object, never closing the file:</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```no_run</span>
<span class="doccomment">/// use std::mem;</span>
<span class="doccomment">/// use std::fs::File;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let file = File::open("foo.txt").unwrap();</span>
<span class="doccomment">/// mem::forget(file);</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The practical use cases for `forget` are rather specialized and mainly come</span>
<span class="doccomment">/// up in unsafe or FFI code.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ## Use case 1</span>
<span class="doccomment">///</span>
<span class="doccomment">/// You have created an uninitialized value using [`mem::uninitialized`][uninit].</span>
<span class="doccomment">/// You must either initialize or `forget` it on every computation path before</span>
<span class="doccomment">/// Rust drops it automatically, like at the end of a scope or after a panic.</span>
<span class="doccomment">/// Running the destructor on an uninitialized value would be [undefined behavior][ub].</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use std::mem;</span>
<span class="doccomment">/// use std::ptr;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # let some_condition = false;</span>
<span class="doccomment">/// unsafe {</span>
<span class="doccomment">/// let mut uninit_vec: Vec<u32> = mem::uninitialized();</span>
<span class="doccomment">///</span>
<span class="doccomment">/// if some_condition {</span>
<span class="doccomment">/// // Initialize the variable.</span>
<span class="doccomment">/// ptr::write(&mut uninit_vec, Vec::new());</span>
<span class="doccomment">/// } else {</span>
<span class="doccomment">/// // Forget the uninitialized value so its destructor doesn't run.</span>
<span class="doccomment">/// mem::forget(uninit_vec);</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ## Use case 2</span>
<span class="doccomment">///</span>
<span class="doccomment">/// You have duplicated the bytes making up a value, without doing a proper</span>
<span class="doccomment">/// [`Clone`][clone]. You need the value's destructor to run only once,</span>
<span class="doccomment">/// because a double `free` is undefined behavior.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// An example is a possible implementation of [`mem::swap`][swap]:</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use std::mem;</span>
<span class="doccomment">/// use std::ptr;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # #[allow(dead_code)]</span>
<span class="doccomment">/// fn swap<T>(x: &mut T, y: &mut T) {</span>
<span class="doccomment">/// unsafe {</span>
<span class="doccomment">/// // Give ourselves some scratch space to work with</span>
<span class="doccomment">/// let mut t: T = mem::uninitialized();</span>
<span class="doccomment">///</span>
<span class="doccomment">/// // Perform the swap, `&mut` pointers never alias</span>
<span class="doccomment">/// ptr::copy_nonoverlapping(&*x, &mut t, 1);</span>
<span class="doccomment">/// ptr::copy_nonoverlapping(&*y, x, 1);</span>
<span class="doccomment">/// ptr::copy_nonoverlapping(&t, y, 1);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// // y and t now point to the same thing, but we need to completely</span>
<span class="doccomment">/// // forget `t` because we do not want to run the destructor for `T`</span>
<span class="doccomment">/// // on its value, which is still owned somewhere outside this function.</span>
<span class="doccomment">/// mem::forget(t);</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ## Use case 3</span>
<span class="doccomment">///</span>
<span class="doccomment">/// You are transferring ownership across a [FFI] boundary to code written in</span>
<span class="doccomment">/// another language. You need to `forget` the value on the Rust side because Rust</span>
<span class="doccomment">/// code is no longer responsible for it.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```no_run</span>
<span class="doccomment">/// use std::mem;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// extern "C" {</span>
<span class="doccomment">/// fn my_c_function(x: *const u32);</span>
<span class="doccomment">/// }</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let x: Box<u32> = Box::new(3);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// // Transfer ownership into C code.</span>
<span class="doccomment">/// unsafe {</span>
<span class="doccomment">/// my_c_function(&*x);</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// mem::forget(x);</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">///</span>
<span class="doccomment">/// In this case, C code must call back into Rust to free the object. Calling C's `free`</span>
<span class="doccomment">/// function on a [`Box`][box] is *not* safe! Also, `Box` provides an [`into_raw`][into_raw]</span>
<span class="doccomment">/// method which is the preferred way to do this in practice.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [drop]: fn.drop.html</span>
<span class="doccomment">/// [uninit]: fn.uninitialized.html</span>
<span class="doccomment">/// [clone]: ../clone/trait.Clone.html</span>
<span class="doccomment">/// [swap]: fn.swap.html</span>
<span class="doccomment">/// [FFI]: ../../book/first-edition/ffi.html</span>
<span class="doccomment">/// [box]: ../../std/boxed/struct.Box.html</span>
<span class="doccomment">/// [into_raw]: ../../std/boxed/struct.Box.html#method.into_raw</span>
<span class="doccomment">/// [ub]: ../../reference/behavior-considered-undefined.html</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">forget</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>(<span class="ident">t</span>: <span class="ident">T</span>) {
<span class="ident">ManuallyDrop</span>::<span class="ident">new</span>(<span class="ident">t</span>);
}
<span class="doccomment">/// Returns the size of a type in bytes.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// More specifically, this is the offset in bytes between successive elements</span>
<span class="doccomment">/// in an array with that item type including alignment padding. Thus, for any</span>
<span class="doccomment">/// type `T` and length `n`, `[T; n]` has a size of `n * size_of::<T>()`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// In general, the size of a type is not stable across compilations, but</span>
<span class="doccomment">/// specific types such as primitives are.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The following table gives the size for primitives.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Type | size_of::\<Type>()</span>
<span class="doccomment">/// ---- | ---------------</span>
<span class="doccomment">/// () | 0</span>
<span class="doccomment">/// bool | 1</span>
<span class="doccomment">/// u8 | 1</span>
<span class="doccomment">/// u16 | 2</span>
<span class="doccomment">/// u32 | 4</span>
<span class="doccomment">/// u64 | 8</span>
<span class="doccomment">/// i8 | 1</span>
<span class="doccomment">/// i16 | 2</span>
<span class="doccomment">/// i32 | 4</span>
<span class="doccomment">/// i64 | 8</span>
<span class="doccomment">/// f32 | 4</span>
<span class="doccomment">/// f64 | 8</span>
<span class="doccomment">/// char | 4</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Furthermore, `usize` and `isize` have the same size.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The types `*const T`, `&T`, `Box<T>`, `Option<&T>`, and `Option<Box<T>>` all have</span>
<span class="doccomment">/// the same size. If `T` is Sized, all of those types have the same size as `usize`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The mutability of a pointer does not change its size. As such, `&T` and `&mut T`</span>
<span class="doccomment">/// have the same size. Likewise for `*const T` and `*mut T`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Size of `#[repr(C)]` items</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The `C` representation for items has a defined layout. With this layout,</span>
<span class="doccomment">/// the size of items is also stable as long as all fields have a stable size.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ## Size of Structs</span>
<span class="doccomment">///</span>
<span class="doccomment">/// For `structs`, the size is determined by the following algorithm.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// For each field in the struct ordered by declaration order:</span>
<span class="doccomment">///</span>
<span class="doccomment">/// 1. Add the size of the field.</span>
<span class="doccomment">/// 2. Round up the current size to the nearest multiple of the next field's [alignment].</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Finally, round the size of the struct to the nearest multiple of its [alignment].</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Unlike `C`, zero sized structs are not rounded up to one byte in size.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ## Size of Enums</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Enums that carry no data other than the descriminant have the same size as C enums</span>
<span class="doccomment">/// on the platform they are compiled for.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ## Size of Unions</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The size of a union is the size of its largest field.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Unlike `C`, zero sized unions are not rounded up to one byte in size.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use std::mem;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// // Some primitives</span>
<span class="doccomment">/// assert_eq!(4, mem::size_of::<i32>());</span>
<span class="doccomment">/// assert_eq!(8, mem::size_of::<f64>());</span>
<span class="doccomment">/// assert_eq!(0, mem::size_of::<()>());</span>
<span class="doccomment">///</span>
<span class="doccomment">/// // Some arrays</span>
<span class="doccomment">/// assert_eq!(8, mem::size_of::<[i32; 2]>());</span>
<span class="doccomment">/// assert_eq!(12, mem::size_of::<[i32; 3]>());</span>
<span class="doccomment">/// assert_eq!(0, mem::size_of::<[i32; 0]>());</span>
<span class="doccomment">///</span>
<span class="doccomment">///</span>
<span class="doccomment">/// // Pointer size equality</span>
<span class="doccomment">/// assert_eq!(mem::size_of::<&i32>(), mem::size_of::<*const i32>());</span>
<span class="doccomment">/// assert_eq!(mem::size_of::<&i32>(), mem::size_of::<Box<i32>>());</span>
<span class="doccomment">/// assert_eq!(mem::size_of::<&i32>(), mem::size_of::<Option<&i32>>());</span>
<span class="doccomment">/// assert_eq!(mem::size_of::<Box<i32>>(), mem::size_of::<Option<Box<i32>>>());</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Using `#[repr(C)]`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use std::mem;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// #[repr(C)]</span>
<span class="doccomment">/// struct FieldStruct {</span>
<span class="doccomment">/// first: u8,</span>
<span class="doccomment">/// second: u16,</span>
<span class="doccomment">/// third: u8</span>
<span class="doccomment">/// }</span>
<span class="doccomment">///</span>
<span class="doccomment">/// // The size of the first field is 1, so add 1 to the size. Size is 1.</span>
<span class="doccomment">/// // The alignment of the second field is 2, so add 1 to the size for padding. Size is 2.</span>
<span class="doccomment">/// // The size of the second field is 2, so add 2 to the size. Size is 4.</span>
<span class="doccomment">/// // The alignment of the third field is 1, so add 0 to the size for padding. Size is 4.</span>
<span class="doccomment">/// // The size of the third field is 1, so add 1 to the size. Size is 5.</span>
<span class="doccomment">/// // Finally, the alignment of the struct is 2, so add 1 to the size for padding. Size is 6.</span>
<span class="doccomment">/// assert_eq!(6, mem::size_of::<FieldStruct>());</span>
<span class="doccomment">///</span>
<span class="doccomment">/// #[repr(C)]</span>
<span class="doccomment">/// struct TupleStruct(u8, u16, u8);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// // Tuple structs follow the same rules.</span>
<span class="doccomment">/// assert_eq!(6, mem::size_of::<TupleStruct>());</span>
<span class="doccomment">///</span>
<span class="doccomment">/// // Note that reordering the fields can lower the size. We can remove both padding bytes</span>
<span class="doccomment">/// // by putting `third` before `second`.</span>
<span class="doccomment">/// #[repr(C)]</span>
<span class="doccomment">/// struct FieldStructOptimized {</span>
<span class="doccomment">/// first: u8,</span>
<span class="doccomment">/// third: u8,</span>
<span class="doccomment">/// second: u16</span>
<span class="doccomment">/// }</span>
<span class="doccomment">///</span>
<span class="doccomment">/// assert_eq!(4, mem::size_of::<FieldStructOptimized>());</span>
<span class="doccomment">///</span>
<span class="doccomment">/// // Union size is the size of the largest field.</span>
<span class="doccomment">/// #[repr(C)]</span>
<span class="doccomment">/// union ExampleUnion {</span>
<span class="doccomment">/// smaller: u8,</span>
<span class="doccomment">/// larger: u16</span>
<span class="doccomment">/// }</span>
<span class="doccomment">///</span>
<span class="doccomment">/// assert_eq!(2, mem::size_of::<ExampleUnion>());</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [alignment]: ./fn.align_of.html</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">const</span> <span class="kw">fn</span> <span class="ident">size_of</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>() <span class="op">-></span> <span class="ident">usize</span> {
<span class="kw">unsafe</span> { <span class="ident">intrinsics</span>::<span class="ident">size_of</span>::<span class="op"><</span><span class="ident">T</span><span class="op">></span>() }
}
<span class="doccomment">/// Returns the size of the pointed-to value in bytes.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This is usually the same as `size_of::<T>()`. However, when `T` *has* no</span>
<span class="doccomment">/// statically known size, e.g. a slice [`[T]`][slice] or a [trait object],</span>
<span class="doccomment">/// then `size_of_val` can be used to get the dynamically-known size.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [slice]: ../../std/primitive.slice.html</span>
<span class="doccomment">/// [trait object]: ../../book/first-edition/trait-objects.html</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use std::mem;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// assert_eq!(4, mem::size_of_val(&5i32));</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let x: [u8; 13] = [0; 13];</span>
<span class="doccomment">/// let y: &[u8] = &x;</span>
<span class="doccomment">/// assert_eq!(13, mem::size_of_val(y));</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">size_of_val</span><span class="op"><</span><span class="ident">T</span>: <span class="question-mark">?</span><span class="ident">Sized</span><span class="op">></span>(<span class="ident">val</span>: <span class="kw-2">&</span><span class="ident">T</span>) <span class="op">-></span> <span class="ident">usize</span> {
<span class="kw">unsafe</span> { <span class="ident">intrinsics</span>::<span class="ident">size_of_val</span>(<span class="ident">val</span>) }
}
<span class="doccomment">/// Returns the [ABI]-required minimum alignment of a type.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Every reference to a value of the type `T` must be a multiple of this number.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This is the alignment used for struct fields. It may be smaller than the preferred alignment.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [ABI]: https://en.wikipedia.org/wiki/Application_binary_interface</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// # #![allow(deprecated)]</span>
<span class="doccomment">/// use std::mem;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// assert_eq!(4, mem::min_align_of::<i32>());</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="attribute">#[<span class="ident">rustc_deprecated</span>(<span class="ident">reason</span> <span class="op">=</span> <span class="string">"use `align_of` instead"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.2.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">min_align_of</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>() <span class="op">-></span> <span class="ident">usize</span> {
<span class="kw">unsafe</span> { <span class="ident">intrinsics</span>::<span class="ident">min_align_of</span>::<span class="op"><</span><span class="ident">T</span><span class="op">></span>() }
}
<span class="doccomment">/// Returns the [ABI]-required minimum alignment of the type of the value that `val` points to.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Every reference to a value of the type `T` must be a multiple of this number.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [ABI]: https://en.wikipedia.org/wiki/Application_binary_interface</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// # #![allow(deprecated)]</span>
<span class="doccomment">/// use std::mem;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// assert_eq!(4, mem::min_align_of_val(&5i32));</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="attribute">#[<span class="ident">rustc_deprecated</span>(<span class="ident">reason</span> <span class="op">=</span> <span class="string">"use `align_of_val` instead"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.2.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">min_align_of_val</span><span class="op"><</span><span class="ident">T</span>: <span class="question-mark">?</span><span class="ident">Sized</span><span class="op">></span>(<span class="ident">val</span>: <span class="kw-2">&</span><span class="ident">T</span>) <span class="op">-></span> <span class="ident">usize</span> {
<span class="kw">unsafe</span> { <span class="ident">intrinsics</span>::<span class="ident">min_align_of_val</span>(<span class="ident">val</span>) }
}
<span class="doccomment">/// Returns the [ABI]-required minimum alignment of a type.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Every reference to a value of the type `T` must be a multiple of this number.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This is the alignment used for struct fields. It may be smaller than the preferred alignment.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [ABI]: https://en.wikipedia.org/wiki/Application_binary_interface</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use std::mem;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// assert_eq!(4, mem::align_of::<i32>());</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">const</span> <span class="kw">fn</span> <span class="ident">align_of</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>() <span class="op">-></span> <span class="ident">usize</span> {
<span class="kw">unsafe</span> { <span class="ident">intrinsics</span>::<span class="ident">min_align_of</span>::<span class="op"><</span><span class="ident">T</span><span class="op">></span>() }
}
<span class="doccomment">/// Returns the [ABI]-required minimum alignment of the type of the value that `val` points to.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Every reference to a value of the type `T` must be a multiple of this number.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [ABI]: https://en.wikipedia.org/wiki/Application_binary_interface</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use std::mem;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// assert_eq!(4, mem::align_of_val(&5i32));</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">align_of_val</span><span class="op"><</span><span class="ident">T</span>: <span class="question-mark">?</span><span class="ident">Sized</span><span class="op">></span>(<span class="ident">val</span>: <span class="kw-2">&</span><span class="ident">T</span>) <span class="op">-></span> <span class="ident">usize</span> {
<span class="kw">unsafe</span> { <span class="ident">intrinsics</span>::<span class="ident">min_align_of_val</span>(<span class="ident">val</span>) }
}
<span class="doccomment">/// Returns whether dropping values of type `T` matters.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This is purely an optimization hint, and may be implemented conservatively:</span>
<span class="doccomment">/// it may return `true` for types that don't actually need to be dropped.</span>
<span class="doccomment">/// As such always returning `true` would be a valid implementation of</span>
<span class="doccomment">/// this function. However if this function actually returns `false`, then you</span>
<span class="doccomment">/// can be certain dropping `T` has no side effect.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Low level implementations of things like collections, which need to manually</span>
<span class="doccomment">/// drop their data, should use this function to avoid unnecessarily</span>
<span class="doccomment">/// trying to drop all their contents when they are destroyed. This might not</span>
<span class="doccomment">/// make a difference in release builds (where a loop that has no side-effects</span>
<span class="doccomment">/// is easily detected and eliminated), but is often a big win for debug builds.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Note that `ptr::drop_in_place` already performs this check, so if your workload</span>
<span class="doccomment">/// can be reduced to some small number of drop_in_place calls, using this is</span>
<span class="doccomment">/// unnecessary. In particular note that you can drop_in_place a slice, and that</span>
<span class="doccomment">/// will do a single needs_drop check for all the values.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Types like Vec therefore just `drop_in_place(&mut self[..])` without using</span>
<span class="doccomment">/// needs_drop explicitly. Types like HashMap, on the other hand, have to drop</span>
<span class="doccomment">/// values one at a time and should use this API.</span>
<span class="doccomment">///</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Here's an example of how a collection might make use of needs_drop:</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use std::{mem, ptr};</span>
<span class="doccomment">///</span>
<span class="doccomment">/// pub struct MyCollection<T> {</span>
<span class="doccomment">/// # data: [T; 1],</span>
<span class="doccomment">/// /* ... */</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// # impl<T> MyCollection<T> {</span>
<span class="doccomment">/// # fn iter_mut(&mut self) -> &mut [T] { &mut self.data }</span>
<span class="doccomment">/// # fn free_buffer(&mut self) {}</span>
<span class="doccomment">/// # }</span>
<span class="doccomment">///</span>
<span class="doccomment">/// impl<T> Drop for MyCollection<T> {</span>
<span class="doccomment">/// fn drop(&mut self) {</span>
<span class="doccomment">/// unsafe {</span>
<span class="doccomment">/// // drop the data</span>
<span class="doccomment">/// if mem::needs_drop::<T>() {</span>
<span class="doccomment">/// for x in self.iter_mut() {</span>
<span class="doccomment">/// ptr::drop_in_place(x);</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// self.free_buffer();</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"needs_drop"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.21.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">needs_drop</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>() <span class="op">-></span> <span class="ident">bool</span> {
<span class="kw">unsafe</span> { <span class="ident">intrinsics</span>::<span class="ident">needs_drop</span>::<span class="op"><</span><span class="ident">T</span><span class="op">></span>() }
}
<span class="doccomment">/// Creates a value whose bytes are all zero.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This has the same effect as allocating space with</span>
<span class="doccomment">/// [`mem::uninitialized`][uninit] and then zeroing it out. It is useful for</span>
<span class="doccomment">/// [FFI] sometimes, but should generally be avoided.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// There is no guarantee that an all-zero byte-pattern represents a valid value of</span>
<span class="doccomment">/// some type `T`. If `T` has a destructor and the value is destroyed (due to</span>
<span class="doccomment">/// a panic or the end of a scope) before being initialized, then the destructor</span>
<span class="doccomment">/// will run on zeroed data, likely leading to [undefined behavior][ub].</span>
<span class="doccomment">///</span>
<span class="doccomment">/// See also the documentation for [`mem::uninitialized`][uninit], which has</span>
<span class="doccomment">/// many of the same caveats.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [uninit]: fn.uninitialized.html</span>
<span class="doccomment">/// [FFI]: ../../book/first-edition/ffi.html</span>
<span class="doccomment">/// [ub]: ../../reference/behavior-considered-undefined.html</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use std::mem;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let x: i32 = unsafe { mem::zeroed() };</span>
<span class="doccomment">/// assert_eq!(0, x);</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">unsafe</span> <span class="kw">fn</span> <span class="ident">zeroed</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>() <span class="op">-></span> <span class="ident">T</span> {
<span class="ident">intrinsics</span>::<span class="ident">init</span>()
}
<span class="doccomment">/// Bypasses Rust's normal memory-initialization checks by pretending to</span>
<span class="doccomment">/// produce a value of type `T`, while doing nothing at all.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// **This is incredibly dangerous and should not be done lightly. Deeply</span>
<span class="doccomment">/// consider initializing your memory with a default value instead.**</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This is useful for [FFI] functions and initializing arrays sometimes,</span>
<span class="doccomment">/// but should generally be avoided.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [FFI]: ../../book/first-edition/ffi.html</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Undefined behavior</span>
<span class="doccomment">///</span>
<span class="doccomment">/// It is [undefined behavior][ub] to read uninitialized memory, even just an</span>
<span class="doccomment">/// uninitialized boolean. For instance, if you branch on the value of such</span>
<span class="doccomment">/// a boolean, your program may take one, both, or neither of the branches.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Writing to the uninitialized value is similarly dangerous. Rust believes the</span>
<span class="doccomment">/// value is initialized, and will therefore try to [`Drop`] the uninitialized</span>
<span class="doccomment">/// value and its fields if you try to overwrite it in a normal manner. The only way</span>
<span class="doccomment">/// to safely initialize an uninitialized value is with [`ptr::write`][write],</span>
<span class="doccomment">/// [`ptr::copy`][copy], or [`ptr::copy_nonoverlapping`][copy_no].</span>
<span class="doccomment">///</span>
<span class="doccomment">/// If the value does implement [`Drop`], it must be initialized before</span>
<span class="doccomment">/// it goes out of scope (and therefore would be dropped). Note that this</span>
<span class="doccomment">/// includes a `panic` occurring and unwinding the stack suddenly.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Here's how to safely initialize an array of [`Vec`]s.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use std::mem;</span>
<span class="doccomment">/// use std::ptr;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// // Only declare the array. This safely leaves it</span>
<span class="doccomment">/// // uninitialized in a way that Rust will track for us.</span>
<span class="doccomment">/// // However we can't initialize it element-by-element</span>
<span class="doccomment">/// // safely, and we can't use the `[value; 1000]`</span>
<span class="doccomment">/// // constructor because it only works with `Copy` data.</span>
<span class="doccomment">/// let mut data: [Vec<u32>; 1000];</span>
<span class="doccomment">///</span>
<span class="doccomment">/// unsafe {</span>
<span class="doccomment">/// // So we need to do this to initialize it.</span>
<span class="doccomment">/// data = mem::uninitialized();</span>
<span class="doccomment">///</span>
<span class="doccomment">/// // DANGER ZONE: if anything panics or otherwise</span>
<span class="doccomment">/// // incorrectly reads the array here, we will have</span>
<span class="doccomment">/// // Undefined Behavior.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// // It's ok to mutably iterate the data, since this</span>
<span class="doccomment">/// // doesn't involve reading it at all.</span>
<span class="doccomment">/// // (ptr and len are statically known for arrays)</span>
<span class="doccomment">/// for elem in &mut data[..] {</span>
<span class="doccomment">/// // *elem = Vec::new() would try to drop the</span>
<span class="doccomment">/// // uninitialized memory at `elem` -- bad!</span>
<span class="doccomment">/// //</span>
<span class="doccomment">/// // Vec::new doesn't allocate or do really</span>
<span class="doccomment">/// // anything. It's only safe to call here</span>
<span class="doccomment">/// // because we know it won't panic.</span>
<span class="doccomment">/// ptr::write(elem, Vec::new());</span>
<span class="doccomment">/// }</span>
<span class="doccomment">///</span>
<span class="doccomment">/// // SAFE ZONE: everything is initialized.</span>
<span class="doccomment">/// }</span>
<span class="doccomment">///</span>
<span class="doccomment">/// println!("{:?}", &data[0]);</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This example emphasizes exactly how delicate and dangerous using `mem::uninitialized`</span>
<span class="doccomment">/// can be. Note that the [`vec!`] macro *does* let you initialize every element with a</span>
<span class="doccomment">/// value that is only [`Clone`], so the following is semantically equivalent and</span>
<span class="doccomment">/// vastly less dangerous, as long as you can live with an extra heap</span>
<span class="doccomment">/// allocation:</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// let data: Vec<Vec<u32>> = vec![Vec::new(); 1000];</span>
<span class="doccomment">/// println!("{:?}", &data[0]);</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`Vec`]: ../../std/vec/struct.Vec.html</span>
<span class="doccomment">/// [`vec!`]: ../../std/macro.vec.html</span>
<span class="doccomment">/// [`Clone`]: ../../std/clone/trait.Clone.html</span>
<span class="doccomment">/// [ub]: ../../reference/behavior-considered-undefined.html</span>
<span class="doccomment">/// [write]: ../ptr/fn.write.html</span>
<span class="doccomment">/// [copy]: ../intrinsics/fn.copy.html</span>
<span class="doccomment">/// [copy_no]: ../intrinsics/fn.copy_nonoverlapping.html</span>
<span class="doccomment">/// [`Drop`]: ../ops/trait.Drop.html</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">unsafe</span> <span class="kw">fn</span> <span class="ident">uninitialized</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>() <span class="op">-></span> <span class="ident">T</span> {
<span class="ident">intrinsics</span>::<span class="ident">uninit</span>()
}
<span class="doccomment">/// Swaps the values at two mutable locations, without deinitializing either one.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use std::mem;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let mut x = 5;</span>
<span class="doccomment">/// let mut y = 42;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// mem::swap(&mut x, &mut y);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// assert_eq!(42, x);</span>
<span class="doccomment">/// assert_eq!(5, y);</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">swap</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>(<span class="ident">x</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">T</span>, <span class="ident">y</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">T</span>) {
<span class="kw">unsafe</span> {
<span class="ident">ptr</span>::<span class="ident">swap_nonoverlapping</span>(<span class="ident">x</span>, <span class="ident">y</span>, <span class="number">1</span>);
}
}
<span class="doccomment">/// Replaces the value at a mutable location with a new one, returning the old value, without</span>
<span class="doccomment">/// deinitializing either one.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// A simple example:</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use std::mem;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let mut v: Vec<i32> = vec![1, 2];</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let old_v = mem::replace(&mut v, vec![3, 4, 5]);</span>
<span class="doccomment">/// assert_eq!(2, old_v.len());</span>
<span class="doccomment">/// assert_eq!(3, v.len());</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">///</span>
<span class="doccomment">/// `replace` allows consumption of a struct field by replacing it with another value.</span>
<span class="doccomment">/// Without `replace` you can run into issues like these:</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```compile_fail,E0507</span>
<span class="doccomment">/// struct Buffer<T> { buf: Vec<T> }</span>
<span class="doccomment">///</span>
<span class="doccomment">/// impl<T> Buffer<T> {</span>
<span class="doccomment">/// fn get_and_reset(&mut self) -> Vec<T> {</span>
<span class="doccomment">/// // error: cannot move out of dereference of `&mut`-pointer</span>
<span class="doccomment">/// let buf = self.buf;</span>
<span class="doccomment">/// self.buf = Vec::new();</span>
<span class="doccomment">/// buf</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Note that `T` does not necessarily implement [`Clone`], so it can't even clone and reset</span>
<span class="doccomment">/// `self.buf`. But `replace` can be used to disassociate the original value of `self.buf` from</span>
<span class="doccomment">/// `self`, allowing it to be returned:</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// # #![allow(dead_code)]</span>
<span class="doccomment">/// use std::mem;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # struct Buffer<T> { buf: Vec<T> }</span>
<span class="doccomment">/// impl<T> Buffer<T> {</span>
<span class="doccomment">/// fn get_and_reset(&mut self) -> Vec<T> {</span>
<span class="doccomment">/// mem::replace(&mut self.buf, Vec::new())</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`Clone`]: ../../std/clone/trait.Clone.html</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">replace</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>(<span class="ident">dest</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">T</span>, <span class="kw-2">mut</span> <span class="ident">src</span>: <span class="ident">T</span>) <span class="op">-></span> <span class="ident">T</span> {
<span class="ident">swap</span>(<span class="ident">dest</span>, <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">src</span>);
<span class="ident">src</span>
}
<span class="doccomment">/// Disposes of a value.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// While this does call the argument's implementation of [`Drop`][drop],</span>
<span class="doccomment">/// it will not release any borrows, as borrows are based on lexical scope.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This effectively does nothing for</span>
<span class="doccomment">/// [types which implement `Copy`](../../book/first-edition/ownership.html#copy-types),</span>
<span class="doccomment">/// e.g. integers. Such values are copied and _then_ moved into the function,</span>
<span class="doccomment">/// so the value persists after this function call.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This function is not magic; it is literally defined as</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// pub fn drop<T>(_x: T) { }</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Because `_x` is moved into the function, it is automatically dropped before</span>
<span class="doccomment">/// the function returns.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [drop]: ../ops/trait.Drop.html</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Basic usage:</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// let v = vec![1, 2, 3];</span>
<span class="doccomment">///</span>
<span class="doccomment">/// drop(v); // explicitly drop the vector</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Borrows are based on lexical scope, so this produces an error:</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```compile_fail,E0502</span>
<span class="doccomment">/// let mut v = vec![1, 2, 3];</span>
<span class="doccomment">/// let x = &v[0];</span>
<span class="doccomment">///</span>
<span class="doccomment">/// drop(x); // explicitly drop the reference, but the borrow still exists</span>
<span class="doccomment">///</span>
<span class="doccomment">/// v.push(4); // error: cannot borrow `v` as mutable because it is also</span>
<span class="doccomment">/// // borrowed as immutable</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">///</span>
<span class="doccomment">/// An inner scope is needed to fix this:</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// let mut v = vec![1, 2, 3];</span>
<span class="doccomment">///</span>
<span class="doccomment">/// {</span>
<span class="doccomment">/// let x = &v[0];</span>
<span class="doccomment">///</span>
<span class="doccomment">/// drop(x); // this is now redundant, as `x` is going out of scope anyway</span>
<span class="doccomment">/// }</span>
<span class="doccomment">///</span>
<span class="doccomment">/// v.push(4); // no problems</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Since [`RefCell`] enforces the borrow rules at runtime, `drop` can</span>
<span class="doccomment">/// release a [`RefCell`] borrow:</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use std::cell::RefCell;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let x = RefCell::new(1);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let mut mutable_borrow = x.borrow_mut();</span>
<span class="doccomment">/// *mutable_borrow = 1;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// drop(mutable_borrow); // relinquish the mutable borrow on this slot</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let borrow = x.borrow();</span>
<span class="doccomment">/// println!("{}", *borrow);</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Integers and other types implementing [`Copy`] are unaffected by `drop`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// #[derive(Copy, Clone)]</span>
<span class="doccomment">/// struct Foo(u8);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let x = 1;</span>
<span class="doccomment">/// let y = Foo(2);</span>
<span class="doccomment">/// drop(x); // a copy of `x` is moved and dropped</span>
<span class="doccomment">/// drop(y); // a copy of `y` is moved and dropped</span>
<span class="doccomment">///</span>
<span class="doccomment">/// println!("x: {}, y: {}", x, y.0); // still available</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`RefCell`]: ../../std/cell/struct.RefCell.html</span>
<span class="doccomment">/// [`Copy`]: ../../std/marker/trait.Copy.html</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">drop</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>(<span class="ident">_x</span>: <span class="ident">T</span>) { }
<span class="doccomment">/// Interprets `src` as having type `&U`, and then reads `src` without moving</span>
<span class="doccomment">/// the contained value.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This function will unsafely assume the pointer `src` is valid for</span>
<span class="doccomment">/// [`size_of::<U>`][size_of] bytes by transmuting `&T` to `&U` and then reading</span>
<span class="doccomment">/// the `&U`. It will also unsafely create a copy of the contained value instead of</span>
<span class="doccomment">/// moving out of `src`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// It is not a compile-time error if `T` and `U` have different sizes, but it</span>
<span class="doccomment">/// is highly encouraged to only invoke this function where `T` and `U` have the</span>
<span class="doccomment">/// same size. This function triggers [undefined behavior][ub] if `U` is larger than</span>
<span class="doccomment">/// `T`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [ub]: ../../reference/behavior-considered-undefined.html</span>
<span class="doccomment">/// [size_of]: fn.size_of.html</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use std::mem;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// #[repr(packed)]</span>
<span class="doccomment">/// struct Foo {</span>
<span class="doccomment">/// bar: u8,</span>
<span class="doccomment">/// }</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let foo_slice = [10u8];</span>
<span class="doccomment">///</span>
<span class="doccomment">/// unsafe {</span>
<span class="doccomment">/// // Copy the data from 'foo_slice' and treat it as a 'Foo'</span>
<span class="doccomment">/// let mut foo_struct: Foo = mem::transmute_copy(&foo_slice);</span>
<span class="doccomment">/// assert_eq!(foo_struct.bar, 10);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// // Modify the copied data</span>
<span class="doccomment">/// foo_struct.bar = 20;</span>
<span class="doccomment">/// assert_eq!(foo_struct.bar, 20);</span>
<span class="doccomment">/// }</span>
<span class="doccomment">///</span>
<span class="doccomment">/// // The contents of 'foo_slice' should not have changed</span>
<span class="doccomment">/// assert_eq!(foo_slice, [10]);</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"rust1"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.0.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">unsafe</span> <span class="kw">fn</span> <span class="ident">transmute_copy</span><span class="op"><</span><span class="ident">T</span>, <span class="ident">U</span><span class="op">></span>(<span class="ident">src</span>: <span class="kw-2">&</span><span class="ident">T</span>) <span class="op">-></span> <span class="ident">U</span> {
<span class="ident">ptr</span>::<span class="ident">read</span>(<span class="ident">src</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw">const</span> <span class="ident">T</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw">const</span> <span class="ident">U</span>)
}
<span class="doccomment">/// Opaque type representing the discriminant of an enum.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// See the `discriminant` function in this module for more information.</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"discriminant_value"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.21.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">Discriminant</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>(<span class="ident">u64</span>, <span class="ident">PhantomData</span><span class="op"><</span><span class="kw">fn</span>() <span class="op">-></span> <span class="ident">T</span><span class="op">></span>);
<span class="comment">// N.B. These trait implementations cannot be derived because we don't want any bounds on T.</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"discriminant_value"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.21.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">Copy</span> <span class="kw">for</span> <span class="ident">Discriminant</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"discriminant_value"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.21.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">clone</span>::<span class="ident">Clone</span> <span class="kw">for</span> <span class="ident">Discriminant</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="kw">fn</span> <span class="ident">clone</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="self">Self</span> {
<span class="kw-2">*</span><span class="self">self</span>
}
}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"discriminant_value"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.21.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">cmp</span>::<span class="ident">PartialEq</span> <span class="kw">for</span> <span class="ident">Discriminant</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="kw">fn</span> <span class="ident">eq</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">rhs</span>: <span class="kw-2">&</span><span class="self">Self</span>) <span class="op">-></span> <span class="ident">bool</span> {
<span class="self">self</span>.<span class="number">0</span> <span class="op">==</span> <span class="ident">rhs</span>.<span class="number">0</span>
}
}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"discriminant_value"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.21.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">cmp</span>::<span class="ident">Eq</span> <span class="kw">for</span> <span class="ident">Discriminant</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"discriminant_value"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.21.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">hash</span>::<span class="ident">Hash</span> <span class="kw">for</span> <span class="ident">Discriminant</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="kw">fn</span> <span class="ident">hash</span><span class="op"><</span><span class="ident">H</span>: <span class="ident">hash</span>::<span class="ident">Hasher</span><span class="op">></span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">state</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">H</span>) {
<span class="self">self</span>.<span class="number">0</span>.<span class="ident">hash</span>(<span class="ident">state</span>);
}
}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"discriminant_value"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.21.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">fmt</span>::<span class="ident">Debug</span> <span class="kw">for</span> <span class="ident">Discriminant</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="kw">fn</span> <span class="ident">fmt</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">fmt</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">fmt</span>::<span class="ident">Formatter</span>) <span class="op">-></span> <span class="ident">fmt</span>::<span class="prelude-ty">Result</span> {
<span class="ident">fmt</span>.<span class="ident">debug_tuple</span>(<span class="string">"Discriminant"</span>)
.<span class="ident">field</span>(<span class="kw-2">&</span><span class="self">self</span>.<span class="number">0</span>)
.<span class="ident">finish</span>()
}
}
<span class="doccomment">/// Returns a value uniquely identifying the enum variant in `v`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// If `T` is not an enum, calling this function will not result in undefined behavior, but the</span>
<span class="doccomment">/// return value is unspecified.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Stability</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The discriminant of an enum variant may change if the enum definition changes. A discriminant</span>
<span class="doccomment">/// of some variant will not change between compilations with the same compiler.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This can be used to compare enums that carry data, while disregarding</span>
<span class="doccomment">/// the actual data:</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use std::mem;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// enum Foo { A(&'static str), B(i32), C(i32) }</span>
<span class="doccomment">///</span>
<span class="doccomment">/// assert!(mem::discriminant(&Foo::A("bar")) == mem::discriminant(&Foo::A("baz")));</span>
<span class="doccomment">/// assert!(mem::discriminant(&Foo::B(1)) == mem::discriminant(&Foo::B(2)));</span>
<span class="doccomment">/// assert!(mem::discriminant(&Foo::B(3)) != mem::discriminant(&Foo::C(3)));</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"discriminant_value"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.21.0"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">discriminant</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>(<span class="ident">v</span>: <span class="kw-2">&</span><span class="ident">T</span>) <span class="op">-></span> <span class="ident">Discriminant</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="kw">unsafe</span> {
<span class="ident">Discriminant</span>(<span class="ident">intrinsics</span>::<span class="ident">discriminant_value</span>(<span class="ident">v</span>), <span class="ident">PhantomData</span>)
}
}
<span class="doccomment">/// A wrapper to inhibit compiler from automatically calling `T`’s destructor.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This wrapper is 0-cost.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This wrapper helps with explicitly documenting the drop order dependencies between fields of</span>
<span class="doccomment">/// the type:</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```rust</span>
<span class="doccomment">/// use std::mem::ManuallyDrop;</span>
<span class="doccomment">/// struct Peach;</span>
<span class="doccomment">/// struct Banana;</span>
<span class="doccomment">/// struct Melon;</span>
<span class="doccomment">/// struct FruitBox {</span>
<span class="doccomment">/// // Immediately clear there’s something non-trivial going on with these fields.</span>
<span class="doccomment">/// peach: ManuallyDrop<Peach>,</span>
<span class="doccomment">/// melon: Melon, // Field that’s independent of the other two.</span>
<span class="doccomment">/// banana: ManuallyDrop<Banana>,</span>
<span class="doccomment">/// }</span>
<span class="doccomment">///</span>
<span class="doccomment">/// impl Drop for FruitBox {</span>
<span class="doccomment">/// fn drop(&mut self) {</span>
<span class="doccomment">/// unsafe {</span>
<span class="doccomment">/// // Explicit ordering in which field destructors are run specified in the intuitive</span>
<span class="doccomment">/// // location – the destructor of the structure containing the fields.</span>
<span class="doccomment">/// // Moreover, one can now reorder fields within the struct however much they want.</span>
<span class="doccomment">/// ManuallyDrop::drop(&mut self.peach);</span>
<span class="doccomment">/// ManuallyDrop::drop(&mut self.banana);</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// // After destructor for `FruitBox` runs (this function), the destructor for Melon gets</span>
<span class="doccomment">/// // invoked in the usual manner, as it is not wrapped in `ManuallyDrop`.</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"manually_drop"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.20.0"</span>)]</span>
<span class="attribute">#[<span class="ident">allow</span>(<span class="ident">unions_with_drop_fields</span>)]</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Copy</span>)]</span>
<span class="kw">pub</span> <span class="ident">union</span> <span class="ident">ManuallyDrop</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>{ <span class="ident">value</span>: <span class="ident">T</span> }
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">ManuallyDrop</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="doccomment">/// Wrap a value to be manually dropped.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```rust</span>
<span class="doccomment">/// use std::mem::ManuallyDrop;</span>
<span class="doccomment">/// ManuallyDrop::new(Box::new(()));</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"manually_drop"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.20.0"</span>)]</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">new</span>(<span class="ident">value</span>: <span class="ident">T</span>) <span class="op">-></span> <span class="ident">ManuallyDrop</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="ident">ManuallyDrop</span> { <span class="ident">value</span>: <span class="ident">value</span> }
}
<span class="doccomment">/// Extract the value from the ManuallyDrop container.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```rust</span>
<span class="doccomment">/// use std::mem::ManuallyDrop;</span>
<span class="doccomment">/// let x = ManuallyDrop::new(Box::new(()));</span>
<span class="doccomment">/// let _: Box<()> = ManuallyDrop::into_inner(x);</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"manually_drop"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.20.0"</span>)]</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">into_inner</span>(<span class="ident">slot</span>: <span class="ident">ManuallyDrop</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>) <span class="op">-></span> <span class="ident">T</span> {
<span class="kw">unsafe</span> {
<span class="ident">slot</span>.<span class="ident">value</span>
}
}
<span class="doccomment">/// Manually drops the contained value.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Safety</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This function runs the destructor of the contained value and thus the wrapped value</span>
<span class="doccomment">/// now represents uninitialized data. It is up to the user of this method to ensure the</span>
<span class="doccomment">/// uninitialized data is not actually used.</span>
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"manually_drop"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.20.0"</span>)]</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">pub</span> <span class="kw">unsafe</span> <span class="kw">fn</span> <span class="ident">drop</span>(<span class="ident">slot</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">ManuallyDrop</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>) {
<span class="ident">ptr</span>::<span class="ident">drop_in_place</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">slot</span>.<span class="ident">value</span>)
}
}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"manually_drop"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.20.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">Deref</span> <span class="kw">for</span> <span class="ident">ManuallyDrop</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="kw">type</span> <span class="ident">Target</span> <span class="op">=</span> <span class="ident">T</span>;
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">deref</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="kw-2">&</span><span class="self">Self</span>::<span class="ident">Target</span> {
<span class="kw">unsafe</span> {
<span class="kw-2">&</span><span class="self">self</span>.<span class="ident">value</span>
}
}
}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"manually_drop"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.20.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">DerefMut</span> <span class="kw">for</span> <span class="ident">ManuallyDrop</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">deref_mut</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">Self</span>::<span class="ident">Target</span> {
<span class="kw">unsafe</span> {
<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>.<span class="ident">value</span>
}
}
}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"manually_drop"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.20.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>: ::<span class="ident">fmt</span>::<span class="ident">Debug</span><span class="op">></span> ::<span class="ident">fmt</span>::<span class="ident">Debug</span> <span class="kw">for</span> <span class="ident">ManuallyDrop</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="kw">fn</span> <span class="ident">fmt</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">fmt</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> ::<span class="ident">fmt</span>::<span class="ident">Formatter</span>) <span class="op">-></span> ::<span class="ident">fmt</span>::<span class="prelude-ty">Result</span> {
<span class="kw">unsafe</span> {
<span class="ident">fmt</span>.<span class="ident">debug_tuple</span>(<span class="string">"ManuallyDrop"</span>).<span class="ident">field</span>(<span class="kw-2">&</span><span class="self">self</span>.<span class="ident">value</span>).<span class="ident">finish</span>()
}
}
}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"manually_drop_impls"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.22.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>: <span class="ident">Clone</span><span class="op">></span> <span class="ident">Clone</span> <span class="kw">for</span> <span class="ident">ManuallyDrop</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="kw">fn</span> <span class="ident">clone</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="self">Self</span> {
<span class="ident">ManuallyDrop</span>::<span class="ident">new</span>(<span class="self">self</span>.<span class="ident">deref</span>().<span class="ident">clone</span>())
}
<span class="kw">fn</span> <span class="ident">clone_from</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>, <span class="ident">source</span>: <span class="kw-2">&</span><span class="self">Self</span>) {
<span class="self">self</span>.<span class="ident">deref_mut</span>().<span class="ident">clone_from</span>(<span class="ident">source</span>);
}
}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"manually_drop_impls"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.22.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>: <span class="ident">Default</span><span class="op">></span> <span class="ident">Default</span> <span class="kw">for</span> <span class="ident">ManuallyDrop</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="kw">fn</span> <span class="ident">default</span>() <span class="op">-></span> <span class="self">Self</span> {
<span class="ident">ManuallyDrop</span>::<span class="ident">new</span>(<span class="ident">Default</span>::<span class="ident">default</span>())
}
}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"manually_drop_impls"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.22.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>: <span class="ident">PartialEq</span><span class="op">></span> <span class="ident">PartialEq</span> <span class="kw">for</span> <span class="ident">ManuallyDrop</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="kw">fn</span> <span class="ident">eq</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">other</span>: <span class="kw-2">&</span><span class="self">Self</span>) <span class="op">-></span> <span class="ident">bool</span> {
<span class="self">self</span>.<span class="ident">deref</span>().<span class="ident">eq</span>(<span class="ident">other</span>)
}
<span class="kw">fn</span> <span class="ident">ne</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">other</span>: <span class="kw-2">&</span><span class="self">Self</span>) <span class="op">-></span> <span class="ident">bool</span> {
<span class="self">self</span>.<span class="ident">deref</span>().<span class="ident">ne</span>(<span class="ident">other</span>)
}
}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"manually_drop_impls"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.22.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>: <span class="ident">Eq</span><span class="op">></span> <span class="ident">Eq</span> <span class="kw">for</span> <span class="ident">ManuallyDrop</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"manually_drop_impls"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.22.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>: <span class="ident">PartialOrd</span><span class="op">></span> <span class="ident">PartialOrd</span> <span class="kw">for</span> <span class="ident">ManuallyDrop</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="kw">fn</span> <span class="ident">partial_cmp</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">other</span>: <span class="kw-2">&</span><span class="self">Self</span>) <span class="op">-></span> <span class="prelude-ty">Option</span><span class="op"><</span>::<span class="ident">cmp</span>::<span class="ident">Ordering</span><span class="op">></span> {
<span class="self">self</span>.<span class="ident">deref</span>().<span class="ident">partial_cmp</span>(<span class="ident">other</span>)
}
<span class="kw">fn</span> <span class="ident">lt</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">other</span>: <span class="kw-2">&</span><span class="self">Self</span>) <span class="op">-></span> <span class="ident">bool</span> {
<span class="self">self</span>.<span class="ident">deref</span>().<span class="ident">lt</span>(<span class="ident">other</span>)
}
<span class="kw">fn</span> <span class="ident">le</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">other</span>: <span class="kw-2">&</span><span class="self">Self</span>) <span class="op">-></span> <span class="ident">bool</span> {
<span class="self">self</span>.<span class="ident">deref</span>().<span class="ident">le</span>(<span class="ident">other</span>)
}
<span class="kw">fn</span> <span class="ident">gt</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">other</span>: <span class="kw-2">&</span><span class="self">Self</span>) <span class="op">-></span> <span class="ident">bool</span> {
<span class="self">self</span>.<span class="ident">deref</span>().<span class="ident">gt</span>(<span class="ident">other</span>)
}
<span class="kw">fn</span> <span class="ident">ge</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">other</span>: <span class="kw-2">&</span><span class="self">Self</span>) <span class="op">-></span> <span class="ident">bool</span> {
<span class="self">self</span>.<span class="ident">deref</span>().<span class="ident">ge</span>(<span class="ident">other</span>)
}
}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"manually_drop_impls"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.22.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>: <span class="ident">Ord</span><span class="op">></span> <span class="ident">Ord</span> <span class="kw">for</span> <span class="ident">ManuallyDrop</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="kw">fn</span> <span class="ident">cmp</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">other</span>: <span class="kw-2">&</span><span class="self">Self</span>) <span class="op">-></span> ::<span class="ident">cmp</span>::<span class="ident">Ordering</span> {
<span class="self">self</span>.<span class="ident">deref</span>().<span class="ident">cmp</span>(<span class="ident">other</span>)
}
}
<span class="attribute">#[<span class="ident">stable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"manually_drop_impls"</span>, <span class="ident">since</span> <span class="op">=</span> <span class="string">"1.22.0"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>: ::<span class="ident">hash</span>::<span class="ident">Hash</span><span class="op">></span> ::<span class="ident">hash</span>::<span class="ident">Hash</span> <span class="kw">for</span> <span class="ident">ManuallyDrop</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="kw">fn</span> <span class="ident">hash</span><span class="op"><</span><span class="ident">H</span>: ::<span class="ident">hash</span>::<span class="ident">Hasher</span><span class="op">></span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">state</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">H</span>) {
<span class="self">self</span>.<span class="ident">deref</span>().<span class="ident">hash</span>(<span class="ident">state</span>);
}
}
<span class="doccomment">/// A pinned reference.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// A pinned reference is a lot like a mutable reference, except that it is not</span>
<span class="doccomment">/// safe to move a value out of a pinned reference unless the type of that</span>
<span class="doccomment">/// value implements the `Unpin` trait.</span>
<span class="attribute">#[<span class="ident">unstable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"pin"</span>, <span class="ident">issue</span> <span class="op">=</span> <span class="string">"49150"</span>)]</span>
<span class="attribute">#[<span class="ident">fundamental</span>]</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">Pin</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span>: <span class="question-mark">?</span><span class="ident">Sized</span> <span class="op">+</span> <span class="lifetime">'a</span><span class="op">></span> {
<span class="ident">inner</span>: <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="kw-2">mut</span> <span class="ident">T</span>,
}
<span class="attribute">#[<span class="ident">unstable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"pin"</span>, <span class="ident">issue</span> <span class="op">=</span> <span class="string">"49150"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span>: <span class="question-mark">?</span><span class="ident">Sized</span> <span class="op">+</span> <span class="ident">Unpin</span><span class="op">></span> <span class="ident">Pin</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span><span class="op">></span> {
<span class="doccomment">/// Construct a new `Pin` around a reference to some data of a type that</span>
<span class="doccomment">/// implements `Unpin`.</span>
<span class="attribute">#[<span class="ident">unstable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"pin"</span>, <span class="ident">issue</span> <span class="op">=</span> <span class="string">"49150"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">new</span>(<span class="ident">reference</span>: <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="kw-2">mut</span> <span class="ident">T</span>) <span class="op">-></span> <span class="ident">Pin</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span><span class="op">></span> {
<span class="ident">Pin</span> { <span class="ident">inner</span>: <span class="ident">reference</span> }
}
}
<span class="attribute">#[<span class="ident">unstable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"pin"</span>, <span class="ident">issue</span> <span class="op">=</span> <span class="string">"49150"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span>: <span class="question-mark">?</span><span class="ident">Sized</span><span class="op">></span> <span class="ident">Pin</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span><span class="op">></span> {
<span class="doccomment">/// Construct a new `Pin` around a reference to some data of a type that</span>
<span class="doccomment">/// may or may not implement `Unpin`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This constructor is unsafe because we do not know what will happen with</span>
<span class="doccomment">/// that data after the reference ends. If you cannot guarantee that the</span>
<span class="doccomment">/// data will never move again, calling this constructor is invalid.</span>
<span class="attribute">#[<span class="ident">unstable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"pin"</span>, <span class="ident">issue</span> <span class="op">=</span> <span class="string">"49150"</span>)]</span>
<span class="kw">pub</span> <span class="kw">unsafe</span> <span class="kw">fn</span> <span class="ident">new_unchecked</span>(<span class="ident">reference</span>: <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="kw-2">mut</span> <span class="ident">T</span>) <span class="op">-></span> <span class="ident">Pin</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span><span class="op">></span> {
<span class="ident">Pin</span> { <span class="ident">inner</span>: <span class="ident">reference</span> }
}
<span class="doccomment">/// Borrow a Pin for a shorter lifetime than it already has.</span>
<span class="attribute">#[<span class="ident">unstable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"pin"</span>, <span class="ident">issue</span> <span class="op">=</span> <span class="string">"49150"</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">borrow</span><span class="op"><</span><span class="lifetime">'b</span><span class="op">></span>(<span class="ident">this</span>: <span class="kw-2">&</span><span class="lifetime">'b</span> <span class="kw-2">mut</span> <span class="ident">Pin</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span><span class="op">></span>) <span class="op">-></span> <span class="ident">Pin</span><span class="op"><</span><span class="lifetime">'b</span>, <span class="ident">T</span><span class="op">></span> {
<span class="ident">Pin</span> { <span class="ident">inner</span>: <span class="ident">this</span>.<span class="ident">inner</span> }
}
<span class="doccomment">/// Get a mutable reference to the data inside of this `Pin`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This function is unsafe. You must guarantee that you will never move</span>
<span class="doccomment">/// the data out of the mutable reference you receive when you call this</span>
<span class="doccomment">/// function.</span>
<span class="attribute">#[<span class="ident">unstable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"pin"</span>, <span class="ident">issue</span> <span class="op">=</span> <span class="string">"49150"</span>)]</span>
<span class="kw">pub</span> <span class="kw">unsafe</span> <span class="kw">fn</span> <span class="ident">get_mut</span><span class="op"><</span><span class="lifetime">'b</span><span class="op">></span>(<span class="ident">this</span>: <span class="kw-2">&</span><span class="lifetime">'b</span> <span class="kw-2">mut</span> <span class="ident">Pin</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span><span class="op">></span>) <span class="op">-></span> <span class="kw-2">&</span><span class="lifetime">'b</span> <span class="kw-2">mut</span> <span class="ident">T</span> {
<span class="ident">this</span>.<span class="ident">inner</span>
}
<span class="doccomment">/// Construct a new pin by mapping the interior value.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// For example, if you wanted to get a `Pin` of a field of something, you</span>
<span class="doccomment">/// could use this to get access to that field in one line of code.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This function is unsafe. You must guarantee that the data you return</span>
<span class="doccomment">/// will not move so long as the argument value does not move (for example,</span>
<span class="doccomment">/// because it is one of the fields of that value), and also that you do</span>
<span class="doccomment">/// not move out of the argument you receive to the interior function.</span>
<span class="attribute">#[<span class="ident">unstable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"pin"</span>, <span class="ident">issue</span> <span class="op">=</span> <span class="string">"49150"</span>)]</span>
<span class="kw">pub</span> <span class="kw">unsafe</span> <span class="kw">fn</span> <span class="ident">map</span><span class="op"><</span><span class="lifetime">'b</span>, <span class="ident">U</span>, <span class="ident">F</span><span class="op">></span>(<span class="ident">this</span>: <span class="kw-2">&</span><span class="lifetime">'b</span> <span class="kw-2">mut</span> <span class="ident">Pin</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span><span class="op">></span>, <span class="ident">f</span>: <span class="ident">F</span>) <span class="op">-></span> <span class="ident">Pin</span><span class="op"><</span><span class="lifetime">'b</span>, <span class="ident">U</span><span class="op">></span> <span class="kw">where</span>
<span class="ident">F</span>: <span class="ident">FnOnce</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">T</span>) <span class="op">-></span> <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">U</span>
{
<span class="ident">Pin</span> { <span class="ident">inner</span>: <span class="ident">f</span>(<span class="ident">this</span>.<span class="ident">inner</span>) }
}
}
<span class="attribute">#[<span class="ident">unstable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"pin"</span>, <span class="ident">issue</span> <span class="op">=</span> <span class="string">"49150"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span>: <span class="question-mark">?</span><span class="ident">Sized</span><span class="op">></span> <span class="ident">Deref</span> <span class="kw">for</span> <span class="ident">Pin</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span><span class="op">></span> {
<span class="kw">type</span> <span class="ident">Target</span> <span class="op">=</span> <span class="ident">T</span>;
<span class="kw">fn</span> <span class="ident">deref</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="kw-2">&</span><span class="ident">T</span> {
<span class="kw-2">&</span><span class="kw-2">*</span><span class="self">self</span>.<span class="ident">inner</span>
}
}
<span class="attribute">#[<span class="ident">unstable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"pin"</span>, <span class="ident">issue</span> <span class="op">=</span> <span class="string">"49150"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span>: <span class="question-mark">?</span><span class="ident">Sized</span> <span class="op">+</span> <span class="ident">Unpin</span><span class="op">></span> <span class="ident">DerefMut</span> <span class="kw">for</span> <span class="ident">Pin</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span><span class="op">></span> {
<span class="kw">fn</span> <span class="ident">deref_mut</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">T</span> {
<span class="self">self</span>.<span class="ident">inner</span>
}
}
<span class="attribute">#[<span class="ident">unstable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"pin"</span>, <span class="ident">issue</span> <span class="op">=</span> <span class="string">"49150"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span>: <span class="ident">fmt</span>::<span class="ident">Debug</span> <span class="op">+</span> <span class="question-mark">?</span><span class="ident">Sized</span><span class="op">></span> <span class="ident">fmt</span>::<span class="ident">Debug</span> <span class="kw">for</span> <span class="ident">Pin</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span><span class="op">></span> {
<span class="kw">fn</span> <span class="ident">fmt</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">f</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">fmt</span>::<span class="ident">Formatter</span>) <span class="op">-></span> <span class="ident">fmt</span>::<span class="prelude-ty">Result</span> {
<span class="ident">fmt</span>::<span class="ident">Debug</span>::<span class="ident">fmt</span>(<span class="kw-2">&</span><span class="kw-2">*</span><span class="kw-2">*</span><span class="self">self</span>, <span class="ident">f</span>)
}
}
<span class="attribute">#[<span class="ident">unstable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"pin"</span>, <span class="ident">issue</span> <span class="op">=</span> <span class="string">"49150"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span>: <span class="ident">fmt</span>::<span class="ident">Display</span> <span class="op">+</span> <span class="question-mark">?</span><span class="ident">Sized</span><span class="op">></span> <span class="ident">fmt</span>::<span class="ident">Display</span> <span class="kw">for</span> <span class="ident">Pin</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span><span class="op">></span> {
<span class="kw">fn</span> <span class="ident">fmt</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">f</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">fmt</span>::<span class="ident">Formatter</span>) <span class="op">-></span> <span class="ident">fmt</span>::<span class="prelude-ty">Result</span> {
<span class="ident">fmt</span>::<span class="ident">Display</span>::<span class="ident">fmt</span>(<span class="kw-2">&</span><span class="kw-2">*</span><span class="kw-2">*</span><span class="self">self</span>, <span class="ident">f</span>)
}
}
<span class="attribute">#[<span class="ident">unstable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"pin"</span>, <span class="ident">issue</span> <span class="op">=</span> <span class="string">"49150"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span>: <span class="question-mark">?</span><span class="ident">Sized</span><span class="op">></span> <span class="ident">fmt</span>::<span class="ident">Pointer</span> <span class="kw">for</span> <span class="ident">Pin</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span><span class="op">></span> {
<span class="kw">fn</span> <span class="ident">fmt</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">f</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">fmt</span>::<span class="ident">Formatter</span>) <span class="op">-></span> <span class="ident">fmt</span>::<span class="prelude-ty">Result</span> {
<span class="ident">fmt</span>::<span class="ident">Pointer</span>::<span class="ident">fmt</span>(<span class="kw-2">&</span>(<span class="kw-2">&</span><span class="kw-2">*</span><span class="self">self</span>.<span class="ident">inner</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw">const</span> <span class="ident">T</span>), <span class="ident">f</span>)
}
}
<span class="attribute">#[<span class="ident">unstable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"pin"</span>, <span class="ident">issue</span> <span class="op">=</span> <span class="string">"49150"</span>)]</span>
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span>: <span class="question-mark">?</span><span class="ident">Sized</span> <span class="op">+</span> <span class="ident">Unsize</span><span class="op"><</span><span class="ident">U</span><span class="op">></span>, <span class="ident">U</span>: <span class="question-mark">?</span><span class="ident">Sized</span><span class="op">></span> <span class="ident">CoerceUnsized</span><span class="op"><</span><span class="ident">Pin</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">U</span><span class="op">>></span> <span class="kw">for</span> <span class="ident">Pin</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span><span class="op">></span> {}
<span class="attribute">#[<span class="ident">unstable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"pin"</span>, <span class="ident">issue</span> <span class="op">=</span> <span class="string">"49150"</span>)]</span>
<span class="kw">unsafe</span> <span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span>: <span class="question-mark">?</span><span class="ident">Sized</span><span class="op">></span> <span class="ident">Unpin</span> <span class="kw">for</span> <span class="ident">Pin</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span><span class="op">></span> {}
</pre>
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