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</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>
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