<!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 `src/libcore/convert.rs`."> <meta name="keywords" content="rust, rustlang, rust-lang"> <title>convert.rs.html -- source</title> <link rel="stylesheet" type="text/css" href="../../normalize.css"> <link rel="stylesheet" type="text/css" href="../../rustdoc.css"> <link rel="stylesheet" type="text/css" href="../../main.css"> <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"> <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> <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"> </div> </form> </nav> <section id='main' class="content"><pre class="line-numbers"><span id="1"> 1</span> <span id="2"> 2</span> <span id="3"> 3</span> <span id="4"> 4</span> <span id="5"> 5</span> <span id="6"> 6</span> <span id="7"> 7</span> <span id="8"> 8</span> <span id="9"> 9</span> <span id="10"> 10</span> <span id="11"> 11</span> <span id="12"> 12</span> <span id="13"> 13</span> <span id="14"> 14</span> <span id="15"> 15</span> <span id="16"> 16</span> <span id="17"> 17</span> <span id="18"> 18</span> <span id="19"> 19</span> <span id="20"> 20</span> <span id="21"> 21</span> <span id="22"> 22</span> <span id="23"> 23</span> <span id="24"> 24</span> <span id="25"> 25</span> <span id="26"> 26</span> <span id="27"> 27</span> <span id="28"> 28</span> <span id="29"> 29</span> <span 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id="451">451</span> <span id="452">452</span> <span id="453">453</span> <span id="454">454</span> <span id="455">455</span> </pre><pre class="rust "> <span class="comment">// Copyright 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">//! Traits for conversions between types.</span> <span class="doccomment">//!</span> <span class="doccomment">//! The traits in this module provide a general way to talk about conversions</span> <span class="doccomment">//! from one type to another. They follow the standard Rust conventions of</span> <span class="doccomment">//! `as`/`into`/`from`.</span> <span class="doccomment">//!</span> <span class="doccomment">//! Like many traits, these are often used as bounds for generic functions, to</span> <span class="doccomment">//! support arguments of multiple types.</span> <span class="doccomment">//!</span> <span class="doccomment">//! - Implement the `As*` traits for reference-to-reference conversions</span> <span class="doccomment">//! - Implement the [`Into`] trait when you want to consume the value in the conversion</span> <span class="doccomment">//! - The [`From`] trait is the most flexible, useful for value _and_ reference conversions</span> <span class="doccomment">//! - The [`TryFrom`] and [`TryInto`] traits behave like [`From`] and [`Into`], but allow for the</span> <span class="doccomment">//! conversion to fail</span> <span class="doccomment">//!</span> <span class="doccomment">//! As a library author, you should prefer implementing [`From<T>`][`From`] or</span> <span class="doccomment">//! [`TryFrom<T>`][`TryFrom`] rather than [`Into<U>`][`Into`] or [`TryInto<U>`][`TryInto`],</span> <span class="doccomment">//! as [`From`] and [`TryFrom`] provide greater flexibility and offer</span> <span class="doccomment">//! equivalent [`Into`] or [`TryInto`] implementations for free, thanks to a</span> <span class="doccomment">//! blanket implementation in the standard library.</span> <span class="doccomment">//!</span> <span class="doccomment">//! # Generic Implementations</span> <span class="doccomment">//!</span> <span class="doccomment">//! - [`AsRef`] and [`AsMut`] auto-dereference if the inner type is a reference</span> <span class="doccomment">//! - [`From`]`<U> for T` implies [`Into`]`<T> for U`</span> <span class="doccomment">//! - [`TryFrom`]`<U> for T` implies [`TryInto`]`<T> for U`</span> <span class="doccomment">//! - [`From`] and [`Into`] are reflexive, which means that all types can</span> <span class="doccomment">//! `into` themselves and `from` themselves</span> <span class="doccomment">//!</span> <span class="doccomment">//! See each trait for usage examples.</span> <span class="doccomment">//!</span> <span class="doccomment">//! [`Into`]: trait.Into.html</span> <span class="doccomment">//! [`From`]: trait.From.html</span> <span class="doccomment">//! [`TryFrom`]: trait.TryFrom.html</span> <span class="doccomment">//! [`TryInto`]: trait.TryInto.html</span> <span class="doccomment">//! [`AsRef`]: trait.AsRef.html</span> <span class="doccomment">//! [`AsMut`]: trait.AsMut.html</span> <span class="attribute">#<span class="op">!</span>[<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">str</span>::<span class="ident">FromStr</span>; <span class="doccomment">/// A cheap reference-to-reference conversion. Used to convert a value to a</span> <span class="doccomment">/// reference value within generic code.</span> <span class="doccomment">///</span> <span class="doccomment">/// `AsRef` is very similar to, but serves a slightly different purpose than,</span> <span class="doccomment">/// [`Borrow`].</span> <span class="doccomment">///</span> <span class="doccomment">/// `AsRef` is to be used when wishing to convert to a reference of another</span> <span class="doccomment">/// type.</span> <span class="doccomment">/// `Borrow` is more related to the notion of taking the reference. It is</span> <span class="doccomment">/// useful when wishing to abstract over the type of reference</span> <span class="doccomment">/// (`&T`, `&mut T`) or allow both the referenced and owned type to be treated</span> <span class="doccomment">/// in the same manner.</span> <span class="doccomment">///</span> <span class="doccomment">/// The key difference between the two traits is the intention:</span> <span class="doccomment">///</span> <span class="doccomment">/// - Use `AsRef` when goal is to simply convert into a reference</span> <span class="doccomment">/// - Use `Borrow` when goal is related to writing code that is agnostic to the</span> <span class="doccomment">/// type of borrow and if is reference or value</span> <span class="doccomment">///</span> <span class="doccomment">/// See [the book][book] for a more detailed comparison.</span> <span class="doccomment">///</span> <span class="doccomment">/// [book]: ../../book/borrow-and-asref.html</span> <span class="doccomment">/// [`Borrow`]: ../../std/borrow/trait.Borrow.html</span> <span class="doccomment">///</span> <span class="doccomment">/// **Note: this trait must not fail**. If the conversion can fail, use a</span> <span class="doccomment">/// dedicated method which returns an [`Option<T>`] or a [`Result<T, E>`].</span> <span class="doccomment">///</span> <span class="doccomment">/// [`Option<T>`]: ../../std/option/enum.Option.html</span> <span class="doccomment">/// [`Result<T, E>`]: ../../std/result/enum.Result.html</span> <span class="doccomment">///</span> <span class="doccomment">/// # Generic Implementations</span> <span class="doccomment">///</span> <span class="doccomment">/// - `AsRef` auto-dereferences if the inner type is a reference or a mutable</span> <span class="doccomment">/// reference (e.g.: `foo.as_ref()` will work the same if `foo` has type</span> <span class="doccomment">/// `&mut Foo` or `&&mut Foo`)</span> <span class="doccomment">///</span> <span class="doccomment">/// # Examples</span> <span class="doccomment">///</span> <span class="doccomment">/// Both [`String`] and `&str` implement `AsRef<str>`:</span> <span class="doccomment">///</span> <span class="doccomment">/// [`String`]: ../../std/string/struct.String.html</span> <span class="doccomment">///</span> <span class="doccomment">/// ```</span> <span class="doccomment">/// fn is_hello<T: AsRef<str>>(s: T) {</span> <span class="doccomment">/// assert_eq!("hello", s.as_ref());</span> <span class="doccomment">/// }</span> <span class="doccomment">///</span> <span class="doccomment">/// let s = "hello";</span> <span class="doccomment">/// is_hello(s);</span> <span class="doccomment">///</span> <span class="doccomment">/// let s = "hello".to_string();</span> <span class="doccomment">/// is_hello(s);</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">"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">trait</span> <span class="ident">AsRef</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="doccomment">/// Performs the conversion.</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">fn</span> <span class="ident">as_ref</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="doccomment">/// A cheap, mutable reference-to-mutable reference conversion.</span> <span class="doccomment">///</span> <span class="doccomment">/// This trait is similar to `AsRef` but used for converting between mutable</span> <span class="doccomment">/// references.</span> <span class="doccomment">///</span> <span class="doccomment">/// **Note: this trait must not fail**. If the conversion can fail, use a</span> <span class="doccomment">/// dedicated method which returns an [`Option<T>`] or a [`Result<T, E>`].</span> <span class="doccomment">///</span> <span class="doccomment">/// [`Option<T>`]: ../../std/option/enum.Option.html</span> <span class="doccomment">/// [`Result<T, E>`]: ../../std/result/enum.Result.html</span> <span class="doccomment">///</span> <span class="doccomment">/// # Generic Implementations</span> <span class="doccomment">///</span> <span class="doccomment">/// - `AsMut` auto-dereferences if the inner type is a reference or a mutable</span> <span class="doccomment">/// reference (e.g.: `foo.as_ref()` will work the same if `foo` has type</span> <span class="doccomment">/// `&mut Foo` or `&&mut Foo`)</span> <span class="doccomment">///</span> <span class="doccomment">/// # Examples</span> <span class="doccomment">///</span> <span class="doccomment">/// [`Box<T>`] implements `AsMut<T>`:</span> <span class="doccomment">///</span> <span class="doccomment">/// [`Box<T>`]: ../../std/boxed/struct.Box.html</span> <span class="doccomment">///</span> <span class="doccomment">/// ```</span> <span class="doccomment">/// fn add_one<T: AsMut<u64>>(num: &mut T) {</span> <span class="doccomment">/// *num.as_mut() += 1;</span> <span class="doccomment">/// }</span> <span class="doccomment">///</span> <span class="doccomment">/// let mut boxed_num = Box::new(0);</span> <span class="doccomment">/// add_one(&mut boxed_num);</span> <span class="doccomment">/// assert_eq!(*boxed_num, 1);</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">"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">trait</span> <span class="ident">AsMut</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="doccomment">/// Performs the conversion.</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">fn</span> <span class="ident">as_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="doccomment">/// A conversion that consumes `self`, which may or may not be expensive. The</span> <span class="doccomment">/// reciprocal of [`From`][From].</span> <span class="doccomment">///</span> <span class="doccomment">/// **Note: this trait must not fail**. If the conversion can fail, use</span> <span class="doccomment">/// [`TryInto`] or a dedicated method which returns an [`Option<T>`] or a</span> <span class="doccomment">/// [`Result<T, E>`].</span> <span class="doccomment">///</span> <span class="doccomment">/// Library authors should not directly implement this trait, but should prefer</span> <span class="doccomment">/// implementing the [`From`][From] trait, which offers greater flexibility and</span> <span class="doccomment">/// provides an equivalent `Into` implementation for free, thanks to a blanket</span> <span class="doccomment">/// implementation in the standard library.</span> <span class="doccomment">///</span> <span class="doccomment">/// # Generic Implementations</span> <span class="doccomment">///</span> <span class="doccomment">/// - [`From<T>`][From]` for U` implies `Into<U> for T`</span> <span class="doccomment">/// - [`into`] is reflexive, which means that `Into<T> for T` is implemented</span> <span class="doccomment">///</span> <span class="doccomment">/// # Implementing `Into`</span> <span class="doccomment">///</span> <span class="doccomment">/// There is one exception to implementing `Into`, and it's kind of esoteric.</span> <span class="doccomment">/// If the destination type is not part of the current crate, and it uses a</span> <span class="doccomment">/// generic variable, then you can't implement `From` directly. For example,</span> <span class="doccomment">/// take this crate:</span> <span class="doccomment">///</span> <span class="doccomment">/// ```compile_fail</span> <span class="doccomment">/// struct Wrapper<T>(Vec<T>);</span> <span class="doccomment">/// impl<T> From<Wrapper<T>> for Vec<T> {</span> <span class="doccomment">/// fn from(w: Wrapper<T>) -> Vec<T> {</span> <span class="doccomment">/// w.0</span> <span class="doccomment">/// }</span> <span class="doccomment">/// }</span> <span class="doccomment">/// ```</span> <span class="doccomment">///</span> <span class="doccomment">/// To fix this, you can implement `Into` directly:</span> <span class="doccomment">///</span> <span class="doccomment">/// ```</span> <span class="doccomment">/// struct Wrapper<T>(Vec<T>);</span> <span class="doccomment">/// impl<T> Into<Vec<T>> for Wrapper<T> {</span> <span class="doccomment">/// fn into(self) -> Vec<T> {</span> <span class="doccomment">/// self.0</span> <span class="doccomment">/// }</span> <span class="doccomment">/// }</span> <span class="doccomment">/// ```</span> <span class="doccomment">///</span> <span class="doccomment">/// This won't always allow the conversion: for example, `try!` and `?`</span> <span class="doccomment">/// always use `From`. However, in most cases, people use `Into` to do the</span> <span class="doccomment">/// conversions, and this will allow that.</span> <span class="doccomment">///</span> <span class="doccomment">/// In almost all cases, you should try to implement `From`, then fall back</span> <span class="doccomment">/// to `Into` if `From` can't be implemented.</span> <span class="doccomment">///</span> <span class="doccomment">/// # Examples</span> <span class="doccomment">///</span> <span class="doccomment">/// [`String`] implements `Into<Vec<u8>>`:</span> <span class="doccomment">///</span> <span class="doccomment">/// ```</span> <span class="doccomment">/// fn is_hello<T: Into<Vec<u8>>>(s: T) {</span> <span class="doccomment">/// let bytes = b"hello".to_vec();</span> <span class="doccomment">/// assert_eq!(bytes, s.into());</span> <span class="doccomment">/// }</span> <span class="doccomment">///</span> <span class="doccomment">/// let s = "hello".to_string();</span> <span class="doccomment">/// is_hello(s);</span> <span class="doccomment">/// ```</span> <span class="doccomment">///</span> <span class="doccomment">/// [`TryInto`]: trait.TryInto.html</span> <span class="doccomment">/// [`Option<T>`]: ../../std/option/enum.Option.html</span> <span class="doccomment">/// [`Result<T, E>`]: ../../std/result/enum.Result.html</span> <span class="doccomment">/// [`String`]: ../../std/string/struct.String.html</span> <span class="doccomment">/// [From]: trait.From.html</span> <span class="doccomment">/// [`into`]: trait.Into.html#tymethod.into</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">trait</span> <span class="ident">Into</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>: <span class="ident">Sized</span> { <span class="doccomment">/// Performs the conversion.</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">fn</span> <span class="ident">into</span>(<span class="self">self</span>) <span class="op">-></span> <span class="ident">T</span>; } <span class="doccomment">/// Simple and safe type conversions in to `Self`. It is the reciprocal of</span> <span class="doccomment">/// `Into`.</span> <span class="doccomment">///</span> <span class="doccomment">/// This trait is useful when performing error handling as described by</span> <span class="doccomment">/// [the book][book] and is closely related to the `?` operator.</span> <span class="doccomment">///</span> <span class="doccomment">/// When constructing a function that is capable of failing the return type</span> <span class="doccomment">/// will generally be of the form `Result<T, E>`.</span> <span class="doccomment">///</span> <span class="doccomment">/// The `From` trait allows for simplification of error handling by providing a</span> <span class="doccomment">/// means of returning a single error type that encapsulates numerous possible</span> <span class="doccomment">/// erroneous situations.</span> <span class="doccomment">///</span> <span class="doccomment">/// This trait is not limited to error handling, rather the general case for</span> <span class="doccomment">/// this trait would be in any type conversions to have an explicit definition</span> <span class="doccomment">/// of how they are performed.</span> <span class="doccomment">///</span> <span class="doccomment">/// **Note: this trait must not fail**. If the conversion can fail, use</span> <span class="doccomment">/// [`TryFrom`] or a dedicated method which returns an [`Option<T>`] or a</span> <span class="doccomment">/// [`Result<T, E>`].</span> <span class="doccomment">///</span> <span class="doccomment">/// # Generic Implementations</span> <span class="doccomment">///</span> <span class="doccomment">/// - `From<T> for U` implies [`Into<U>`]` for T`</span> <span class="doccomment">/// - [`from`] is reflexive, which means that `From<T> for T` is implemented</span> <span class="doccomment">///</span> <span class="doccomment">/// # Examples</span> <span class="doccomment">///</span> <span class="doccomment">/// [`String`] implements `From<&str>`:</span> <span class="doccomment">///</span> <span class="doccomment">/// ```</span> <span class="doccomment">/// let string = "hello".to_string();</span> <span class="doccomment">/// let other_string = String::from("hello");</span> <span class="doccomment">///</span> <span class="doccomment">/// assert_eq!(string, other_string);</span> <span class="doccomment">/// ```</span> <span class="doccomment">///</span> <span class="doccomment">/// An example usage for error handling:</span> <span class="doccomment">///</span> <span class="doccomment">/// ```</span> <span class="doccomment">/// use std::io::{self, Read};</span> <span class="doccomment">/// use std::num;</span> <span class="doccomment">///</span> <span class="doccomment">/// enum CliError {</span> <span class="doccomment">/// IoError(io::Error),</span> <span class="doccomment">/// ParseError(num::ParseIntError),</span> <span class="doccomment">/// }</span> <span class="doccomment">///</span> <span class="doccomment">/// impl From<io::Error> for CliError {</span> <span class="doccomment">/// fn from(error: io::Error) -> Self {</span> <span class="doccomment">/// CliError::IoError(error)</span> <span class="doccomment">/// }</span> <span class="doccomment">/// }</span> <span class="doccomment">///</span> <span class="doccomment">/// impl From<num::ParseIntError> for CliError {</span> <span class="doccomment">/// fn from(error: num::ParseIntError) -> Self {</span> <span class="doccomment">/// CliError::ParseError(error)</span> <span class="doccomment">/// }</span> <span class="doccomment">/// }</span> <span class="doccomment">///</span> <span class="doccomment">/// fn open_and_parse_file(file_name: &str) -> Result<i32, CliError> {</span> <span class="doccomment">/// let mut file = std::fs::File::open("test")?;</span> <span class="doccomment">/// let mut contents = String::new();</span> <span class="doccomment">/// file.read_to_string(&mut contents)?;</span> <span class="doccomment">/// let num: i32 = contents.trim().parse()?;</span> <span class="doccomment">/// Ok(num)</span> <span class="doccomment">/// }</span> <span class="doccomment">/// ```</span> <span class="doccomment">///</span> <span class="doccomment">/// [`TryFrom`]: trait.TryFrom.html</span> <span class="doccomment">/// [`Option<T>`]: ../../std/option/enum.Option.html</span> <span class="doccomment">/// [`Result<T, E>`]: ../../std/result/enum.Result.html</span> <span class="doccomment">/// [`String`]: ../../std/string/struct.String.html</span> <span class="doccomment">/// [`Into<U>`]: trait.Into.html</span> <span class="doccomment">/// [`from`]: trait.From.html#tymethod.from</span> <span class="doccomment">/// [book]: ../../book/error-handling.html</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">trait</span> <span class="ident">From</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>: <span class="ident">Sized</span> { <span class="doccomment">/// Performs the conversion.</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">fn</span> <span class="ident">from</span>(_: <span class="ident">T</span>) <span class="op">-></span> <span class="self">Self</span>; } <span class="doccomment">/// An attempted conversion that consumes `self`, which may or may not be</span> <span class="doccomment">/// expensive.</span> <span class="doccomment">///</span> <span class="doccomment">/// Library authors should not directly implement this trait, but should prefer</span> <span class="doccomment">/// implementing the [`TryFrom`] trait, which offers greater flexibility and</span> <span class="doccomment">/// provides an equivalent `TryInto` implementation for free, thanks to a</span> <span class="doccomment">/// blanket implementation in the standard library. For more information on this,</span> <span class="doccomment">/// see the documentation for [`Into`].</span> <span class="doccomment">///</span> <span class="doccomment">/// [`TryFrom`]: trait.TryFrom.html</span> <span class="doccomment">/// [`Into`]: trait.Into.html</span> <span class="attribute">#[<span class="ident">unstable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"try_from"</span>, <span class="ident">issue</span> <span class="op">=</span> <span class="string">"33417"</span>)]</span> <span class="kw">pub</span> <span class="kw">trait</span> <span class="ident">TryInto</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>: <span class="ident">Sized</span> { <span class="doccomment">/// The type returned in the event of a conversion error.</span> <span class="kw">type</span> <span class="ident">Error</span>; <span class="doccomment">/// Performs the conversion.</span> <span class="kw">fn</span> <span class="ident">try_into</span>(<span class="self">self</span>) <span class="op">-></span> <span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">T</span>, <span class="self">Self</span>::<span class="ident">Error</span><span class="op">></span>; } <span class="doccomment">/// Attempt to construct `Self` via a conversion.</span> <span class="attribute">#[<span class="ident">unstable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"try_from"</span>, <span class="ident">issue</span> <span class="op">=</span> <span class="string">"33417"</span>)]</span> <span class="kw">pub</span> <span class="kw">trait</span> <span class="ident">TryFrom</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>: <span class="ident">Sized</span> { <span class="doccomment">/// The type returned in the event of a conversion error.</span> <span class="kw">type</span> <span class="ident">Error</span>; <span class="doccomment">/// Performs the conversion.</span> <span class="kw">fn</span> <span class="ident">try_from</span>(<span class="ident">value</span>: <span class="ident">T</span>) <span class="op">-></span> <span class="prelude-ty">Result</span><span class="op"><</span><span class="self">Self</span>, <span class="self">Self</span>::<span class="ident">Error</span><span class="op">></span>; } <span class="comment">////////////////////////////////////////////////////////////////////////////////</span> <span class="comment">// GENERIC IMPLS</span> <span class="comment">////////////////////////////////////////////////////////////////////////////////</span> <span class="comment">// As lifts over &</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">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="ident">U</span>: <span class="question-mark">?</span><span class="ident">Sized</span><span class="op">></span> <span class="ident">AsRef</span><span class="op"><</span><span class="ident">U</span><span class="op">></span> <span class="kw">for</span> <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="ident">T</span> <span class="kw">where</span> <span class="ident">T</span>: <span class="ident">AsRef</span><span class="op"><</span><span class="ident">U</span><span class="op">></span> { <span class="kw">fn</span> <span class="ident">as_ref</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="kw-2">&</span><span class="ident">U</span> { <span class="op"><</span><span class="ident">T</span> <span class="kw">as</span> <span class="ident">AsRef</span><span class="op"><</span><span class="ident">U</span><span class="op">>></span>::<span class="ident">as_ref</span>(<span class="kw-2">*</span><span class="self">self</span>) } } <span class="comment">// As lifts over &mut</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">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="ident">U</span>: <span class="question-mark">?</span><span class="ident">Sized</span><span class="op">></span> <span class="ident">AsRef</span><span class="op"><</span><span class="ident">U</span><span class="op">></span> <span class="kw">for</span> <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="kw-2">mut</span> <span class="ident">T</span> <span class="kw">where</span> <span class="ident">T</span>: <span class="ident">AsRef</span><span class="op"><</span><span class="ident">U</span><span class="op">></span> { <span class="kw">fn</span> <span class="ident">as_ref</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="kw-2">&</span><span class="ident">U</span> { <span class="op"><</span><span class="ident">T</span> <span class="kw">as</span> <span class="ident">AsRef</span><span class="op"><</span><span class="ident">U</span><span class="op">>></span>::<span class="ident">as_ref</span>(<span class="kw-2">*</span><span class="self">self</span>) } } <span class="comment">// FIXME (#23442): replace the above impls for &/&mut with the following more general one:</span> <span class="comment">// // As lifts over Deref</span> <span class="comment">// impl<D: ?Sized + Deref, U: ?Sized> AsRef<U> for D where D::Target: AsRef<U> {</span> <span class="comment">// fn as_ref(&self) -> &U {</span> <span class="comment">// self.deref().as_ref()</span> <span class="comment">// }</span> <span class="comment">// }</span> <span class="comment">// AsMut lifts over &mut</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">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="ident">U</span>: <span class="question-mark">?</span><span class="ident">Sized</span><span class="op">></span> <span class="ident">AsMut</span><span class="op"><</span><span class="ident">U</span><span class="op">></span> <span class="kw">for</span> <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="kw-2">mut</span> <span class="ident">T</span> <span class="kw">where</span> <span class="ident">T</span>: <span class="ident">AsMut</span><span class="op"><</span><span class="ident">U</span><span class="op">></span> { <span class="kw">fn</span> <span class="ident">as_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">U</span> { (<span class="kw-2">*</span><span class="self">self</span>).<span class="ident">as_mut</span>() } } <span class="comment">// FIXME (#23442): replace the above impl for &mut with the following more general one:</span> <span class="comment">// // AsMut lifts over DerefMut</span> <span class="comment">// impl<D: ?Sized + Deref, U: ?Sized> AsMut<U> for D where D::Target: AsMut<U> {</span> <span class="comment">// fn as_mut(&mut self) -> &mut U {</span> <span class="comment">// self.deref_mut().as_mut()</span> <span class="comment">// }</span> <span class="comment">// }</span> <span class="comment">// From implies Into</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">impl</span><span class="op"><</span><span class="ident">T</span>, <span class="ident">U</span><span class="op">></span> <span class="ident">Into</span><span class="op"><</span><span class="ident">U</span><span class="op">></span> <span class="kw">for</span> <span class="ident">T</span> <span class="kw">where</span> <span class="ident">U</span>: <span class="ident">From</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> { <span class="kw">fn</span> <span class="ident">into</span>(<span class="self">self</span>) <span class="op">-></span> <span class="ident">U</span> { <span class="ident">U</span>::<span class="ident">from</span>(<span class="self">self</span>) } } <span class="comment">// From (and thus Into) is reflexive</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">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">From</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="kw">for</span> <span class="ident">T</span> { <span class="kw">fn</span> <span class="ident">from</span>(<span class="ident">t</span>: <span class="ident">T</span>) <span class="op">-></span> <span class="ident">T</span> { <span class="ident">t</span> } } <span class="comment">// TryFrom implies TryInto</span> <span class="attribute">#[<span class="ident">unstable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"try_from"</span>, <span class="ident">issue</span> <span class="op">=</span> <span class="string">"33417"</span>)]</span> <span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>, <span class="ident">U</span><span class="op">></span> <span class="ident">TryInto</span><span class="op"><</span><span class="ident">U</span><span class="op">></span> <span class="kw">for</span> <span class="ident">T</span> <span class="kw">where</span> <span class="ident">U</span>: <span class="ident">TryFrom</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> { <span class="kw">type</span> <span class="ident">Error</span> <span class="op">=</span> <span class="ident">U</span>::<span class="ident">Error</span>; <span class="kw">fn</span> <span class="ident">try_into</span>(<span class="self">self</span>) <span class="op">-></span> <span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">U</span>, <span class="ident">U</span>::<span class="ident">Error</span><span class="op">></span> { <span class="ident">U</span>::<span class="ident">try_from</span>(<span class="self">self</span>) } } <span class="comment">////////////////////////////////////////////////////////////////////////////////</span> <span class="comment">// CONCRETE IMPLS</span> <span class="comment">////////////////////////////////////////////////////////////////////////////////</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">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">AsRef</span><span class="op"><</span>[<span class="ident">T</span>]<span class="op">></span> <span class="kw">for</span> [<span class="ident">T</span>] { <span class="kw">fn</span> <span class="ident">as_ref</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="self">self</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">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">AsMut</span><span class="op"><</span>[<span class="ident">T</span>]<span class="op">></span> <span class="kw">for</span> [<span class="ident">T</span>] { <span class="kw">fn</span> <span class="ident">as_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="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">impl</span> <span class="ident">AsRef</span><span class="op"><</span><span class="ident">str</span><span class="op">></span> <span class="kw">for</span> <span class="ident">str</span> { <span class="attribute">#[<span class="ident">inline</span>]</span> <span class="kw">fn</span> <span class="ident">as_ref</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="kw-2">&</span><span class="ident">str</span> { <span class="self">self</span> } } <span class="comment">// FromStr implies TryFrom<&str></span> <span class="attribute">#[<span class="ident">unstable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"try_from"</span>, <span class="ident">issue</span> <span class="op">=</span> <span class="string">"33417"</span>)]</span> <span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">T</span><span class="op">></span> <span class="ident">TryFrom</span><span class="op"><</span><span class="kw-2">&</span><span class="lifetime">'a</span> <span class="ident">str</span><span class="op">></span> <span class="kw">for</span> <span class="ident">T</span> <span class="kw">where</span> <span class="ident">T</span>: <span class="ident">FromStr</span> { <span class="kw">type</span> <span class="ident">Error</span> <span class="op">=</span> <span class="op"><</span><span class="ident">T</span> <span class="kw">as</span> <span class="ident">FromStr</span><span class="op">></span>::<span class="prelude-val">Err</span>; <span class="kw">fn</span> <span class="ident">try_from</span>(<span class="ident">s</span>: <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="ident">str</span>) <span class="op">-></span> <span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">T</span>, <span class="self">Self</span>::<span class="ident">Error</span><span class="op">></span> { <span class="ident">FromStr</span>::<span class="ident">from_str</span>(<span class="ident">s</span>) } } </pre> </section> <section id='search' class="content hidden"></section> <section class="footer"></section> <aside id="help" class="hidden"> <div> <h1 class="hidden">Help</h1> <div class="shortcuts"> <h2>Keyboard Shortcuts</h2> <dl> <dt>?</dt> <dd>Show this help dialog</dd> <dt>S</dt> <dd>Focus the search field</dd> 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