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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">//! A module for working with borrowed data.</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="doccomment">/// A trait for borrowing data.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// In general, there may be several ways to "borrow" a piece of data. The</span>
<span class="doccomment">/// typical ways of borrowing a type `T` are `&T` (a shared borrow) and `&mut T`</span>
<span class="doccomment">/// (a mutable borrow). But types like `Vec<T>` provide additional kinds of</span>
<span class="doccomment">/// borrows: the borrowed slices `&[T]` and `&mut [T]`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// When writing generic code, it is often desirable to abstract over all ways</span>
<span class="doccomment">/// of borrowing data from a given type. That is the role of the `Borrow`</span>
<span class="doccomment">/// trait: if `T: Borrow<U>`, then `&U` can be borrowed from `&T`. A given</span>
<span class="doccomment">/// type can be borrowed as multiple different types. In particular, `Vec<T>:</span>
<span class="doccomment">/// Borrow<Vec<T>>` and `Vec<T>: Borrow<[T]>`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// If you are implementing `Borrow` and both `Self` and `Borrowed` implement</span>
<span class="doccomment">/// `Hash`, `Eq`, and/or `Ord`, they must produce the same result.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// `Borrow` is very similar to, but different than, `AsRef`. See</span>
<span class="doccomment">/// [the book][book] for more.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [book]: ../../book/borrow-and-asref.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">Borrow</span><span class="op"><</span><span class="ident">Borrowed</span>: <span class="question-mark">?</span><span class="ident">Sized</span><span class="op">></span> {
<span class="doccomment">/// Immutably borrows from an owned value.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use std::borrow::Borrow;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// fn check<T: Borrow<str>>(s: T) {</span>
<span class="doccomment">/// assert_eq!("Hello", s.borrow());</span>
<span class="doccomment">/// }</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let s = "Hello".to_string();</span>
<span class="doccomment">///</span>
<span class="doccomment">/// check(s);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let s = "Hello";</span>
<span class="doccomment">///</span>
<span class="doccomment">/// check(s);</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">fn</span> <span class="ident">borrow</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="kw-2">&</span><span class="ident">Borrowed</span>;
}
<span class="doccomment">/// A trait for mutably borrowing data.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Similar to `Borrow`, but for mutable borrows.</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">BorrowMut</span><span class="op"><</span><span class="ident">Borrowed</span>: <span class="question-mark">?</span><span class="ident">Sized</span><span class="op">></span> : <span class="ident">Borrow</span><span class="op"><</span><span class="ident">Borrowed</span><span class="op">></span> {
<span class="doccomment">/// Mutably borrows from an owned value.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use std::borrow::BorrowMut;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// fn check<T: BorrowMut<[i32]>>(mut v: T) {</span>
<span class="doccomment">/// assert_eq!(&mut [1, 2, 3], v.borrow_mut());</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">/// check(v);</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">fn</span> <span class="ident">borrow_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">Borrowed</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="question-mark">?</span><span class="ident">Sized</span><span class="op">></span> <span class="ident">Borrow</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">borrow</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="question-mark">?</span><span class="ident">Sized</span><span class="op">></span> <span class="ident">BorrowMut</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">borrow_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="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">Borrow</span><span class="op"><</span><span class="ident">T</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">fn</span> <span class="ident">borrow</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="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">"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="op">></span> <span class="ident">Borrow</span><span class="op"><</span><span class="ident">T</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">fn</span> <span class="ident">borrow</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="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">"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="op">></span> <span class="ident">BorrowMut</span><span class="op"><</span><span class="ident">T</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">fn</span> <span class="ident">borrow_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="kw-2">&</span><span class="kw-2">mut</span> <span class="kw-2">*</span><span class="kw-2">*</span><span class="self">self</span> }
}
</pre>
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