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<p class='location'>Trait Borrow</p><div class="sidebar-elems"><div class="block items"><a class="sidebar-title" href="#required-methods">Required Methods</a><div class="sidebar-links"><a href="#tymethod.borrow">borrow</a></div><a class="sidebar-title" href="#implementors">Implementors</a></div><p class='location'><a href='../index.html'>alloc</a>::<wbr><a href='index.html'>borrow</a></p><script>window.sidebarCurrent = {name: 'Borrow', ty: 'trait', relpath: ''};</script><script defer src="sidebar-items.js"></script></div>
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<h1 class='fqn'><span class='in-band'>Trait <a href='../index.html'>alloc</a>::<wbr><a href='index.html'>borrow</a>::<wbr><a class="trait" href=''>Borrow</a></span><span class='out-of-band'><span class='since' title='Stable since Rust version 1.0.0'>1.0.0</span><span id='render-detail'>
<a id="toggle-all-docs" href="javascript:void(0)" title="collapse all docs">
[<span class='inner'>−</span>]
</a>
</span><a class='srclink' href='../../src/core/borrow.rs.html#36-58' title='goto source code'>[src]</a></span></h1>
<pre class='rust trait'>pub trait Borrow<Borrowed> <span class="where fmt-newline">where<br> Borrowed: ?<a class="trait" href="../../core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>, </span>{
fn <a href='#tymethod.borrow' class='fnname'>borrow</a>(&self) -> &Borrowed;
}</pre><div class='docblock'><p>A trait for borrowing data.</p>
<p>In general, there may be several ways to "borrow" a piece of data. The
typical ways of borrowing a type <code>T</code> are <code>&T</code> (a shared borrow) and <code>&mut T</code>
(a mutable borrow). But types like <code>Vec<T></code> provide additional kinds of
borrows: the borrowed slices <code>&[T]</code> and <code>&mut [T]</code>.</p>
<p>When writing generic code, it is often desirable to abstract over all ways
of borrowing data from a given type. That is the role of the <code>Borrow</code>
trait: if <code>T: Borrow<U></code>, then <code>&U</code> can be borrowed from <code>&T</code>. A given
type can be borrowed as multiple different types. In particular, <code>Vec<T>: Borrow<Vec<T>></code> and <code>Vec<T>: Borrow<[T]></code>.</p>
<p>If you are implementing <code>Borrow</code> and both <code>Self</code> and <code>Borrowed</code> implement
<code>Hash</code>, <code>Eq</code>, and/or <code>Ord</code>, they must produce the same result.</p>
<p><code>Borrow</code> is very similar to, but different than, <code>AsRef</code>. See
<a href="../../book/first-edition/borrow-and-asref.html">the book</a> for more.</p>
</div>
<h2 id='required-methods' class='small-section-header'>
Required Methods<a href='#required-methods' class='anchor'></a>
</h2>
<div class='methods'>
<h3 id='tymethod.borrow' class='method'><span id='borrow.v' class='invisible'><code>fn <a href='#tymethod.borrow' class='fnname'>borrow</a>(&self) -> &Borrowed</code></span></h3><div class='docblock'><p>Immutably borrows from an owned value.</p>
<h1 id="examples" class="section-header"><a href="#examples">Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">borrow</span>::<span class="ident">Borrow</span>;
<span class="kw">fn</span> <span class="ident">check</span><span class="op"><</span><span class="ident">T</span>: <span class="ident">Borrow</span><span class="op"><</span><span class="ident">str</span><span class="op">>></span>(<span class="ident">s</span>: <span class="ident">T</span>) {
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="string">"Hello"</span>, <span class="ident">s</span>.<span class="ident">borrow</span>());
}
<span class="kw">let</span> <span class="ident">s</span> <span class="op">=</span> <span class="string">"Hello"</span>.<span class="ident">to_string</span>();
<span class="ident">check</span>(<span class="ident">s</span>);
<span class="kw">let</span> <span class="ident">s</span> <span class="op">=</span> <span class="string">"Hello"</span>;
<span class="ident">check</span>(<span class="ident">s</span>);</pre>
</div></div>
<h2 id='implementors' class='small-section-header'>
Implementors<a href='#implementors' class='anchor'></a>
</h2>
<ul class='item-list' id='implementors-list'>
<li><div class='out-of-band'><a class='srclink' href='../../src/alloc/boxed.rs.html#867-871' title='goto source code'>[src]</a></div><code>impl<T: ?<a class="trait" href="../../core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>> Borrow<T> for <a class="struct" href="../../alloc/boxed/struct.Box.html" title="struct alloc::boxed::Box">Box</a><T></code></li>
<li><div class='out-of-band'><a class='srclink' href='../../src/alloc/arc.rs.html#1853-1857' title='goto source code'>[src]</a></div><code>impl<T: ?<a class="trait" href="../../core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>> Borrow<T> for <a class="struct" href="../../alloc/arc/struct.Arc.html" title="struct alloc::arc::Arc">Arc</a><T></code></li>
<li><div class='out-of-band'><a class='srclink' href='../../src/alloc/rc.rs.html#1796-1800' title='goto source code'>[src]</a></div><code>impl<T: ?<a class="trait" href="../../core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>> Borrow<T> for <a class="struct" href="../../alloc/rc/struct.Rc.html" title="struct alloc::rc::Rc">Rc</a><T></code></li>
<li><div class='out-of-band'><a class='srclink' href='../../src/core/array.rs.html#138-142' title='goto source code'>[src]</a></div><code>impl<T> Borrow<[T]> for [T; 18]</code></li>
<li><div class='out-of-band'><a class='srclink' href='../../src/core/array.rs.html#138-142' title='goto source code'>[src]</a></div><code>impl<T> Borrow<[T]> for [T; 12]</code></li>
<li><div class='out-of-band'><a class='srclink' href='../../src/core/array.rs.html#138-142' title='goto source code'>[src]</a></div><code>impl<T> Borrow<[T]> for [T; 13]</code></li>
<li><div class='out-of-band'><a class='srclink' href='../../src/core/array.rs.html#138-142' title='goto source code'>[src]</a></div><code>impl<T> Borrow<[T]> for [T; 7]</code></li>
<li><div class='out-of-band'><a class='srclink' href='../../src/core/array.rs.html#138-142' title='goto source code'>[src]</a></div><code>impl<T> Borrow<[T]> for [T; 1]</code></li>
<li><div class='out-of-band'><a class='srclink' href='../../src/core/array.rs.html#138-142' title='goto source code'>[src]</a></div><code>impl<T> Borrow<[T]> for [T; 24]</code></li>
<li><div class='out-of-band'><a class='srclink' href='../../src/core/array.rs.html#138-142' title='goto source code'>[src]</a></div><code>impl<T> Borrow<[T]> for [T; 11]</code></li>
<li><div class='out-of-band'><a class='srclink' href='../../src/core/array.rs.html#138-142' title='goto source code'>[src]</a></div><code>impl<T> Borrow<[T]> for [T; 0]</code></li>
<li><div class='out-of-band'><a class='srclink' href='../../src/core/array.rs.html#138-142' title='goto source code'>[src]</a></div><code>impl<T> Borrow<[T]> for [T; 19]</code></li>
<li><div class='out-of-band'><a class='srclink' href='../../src/core/array.rs.html#138-142' title='goto source code'>[src]</a></div><code>impl<T> Borrow<[T]> for [T; 9]</code></li>
<li><div class='out-of-band'><a class='srclink' href='../../src/core/array.rs.html#138-142' title='goto source code'>[src]</a></div><code>impl<T> Borrow<[T]> for [T; 28]</code></li>
<li><div class='out-of-band'><a class='srclink' href='../../src/core/borrow.rs.html#85-87' title='goto source code'>[src]</a></div><code>impl<T> Borrow<T> for T <span class="where fmt-newline">where<br> T: ?<a class="trait" href="../../core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>, </span></code></li>
<li><div class='out-of-band'><a class='srclink' href='../../src/core/array.rs.html#138-142' title='goto source code'>[src]</a></div><code>impl<T> Borrow<[T]> for [T; 17]</code></li>
<li><div class='out-of-band'><a class='srclink' href='../../src/core/array.rs.html#138-142' title='goto source code'>[src]</a></div><code>impl<T> Borrow<[T]> for [T; 30]</code></li>
<li><div class='out-of-band'><a class='srclink' href='../../src/core/array.rs.html#138-142' title='goto source code'>[src]</a></div><code>impl<T> Borrow<[T]> for [T; 20]</code></li>
<li><div class='out-of-band'><a class='srclink' href='../../src/core/array.rs.html#138-142' title='goto source code'>[src]</a></div><code>impl<T> Borrow<[T]> for [T; 23]</code></li>
<li><div class='out-of-band'><a class='srclink' href='../../src/core/array.rs.html#138-142' title='goto source code'>[src]</a></div><code>impl<T> Borrow<[T]> for [T; 2]</code></li>
<li><div class='out-of-band'><a class='srclink' href='../../src/core/array.rs.html#138-142' title='goto source code'>[src]</a></div><code>impl<T> Borrow<[T]> for [T; 3]</code></li>
<li><div class='out-of-band'><a class='srclink' href='../../src/core/array.rs.html#138-142' title='goto source code'>[src]</a></div><code>impl<T> Borrow<[T]> for [T; 26]</code></li>
<li><div class='out-of-band'><a class='srclink' href='../../src/core/array.rs.html#138-142' title='goto source code'>[src]</a></div><code>impl<T> Borrow<[T]> for [T; 27]</code></li>
<li><div class='out-of-band'><a class='srclink' href='../../src/core/array.rs.html#138-142' title='goto source code'>[src]</a></div><code>impl<T> Borrow<[T]> for [T; 29]</code></li>
<li><div class='out-of-band'><a class='srclink' href='../../src/core/borrow.rs.html#95-97' title='goto source code'>[src]</a></div><code>impl<'a, T> Borrow<T> for &'a T <span class="where fmt-newline">where<br> T: ?<a class="trait" href="../../core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>, </span></code></li>
<li><div class='out-of-band'><a class='srclink' href='../../src/core/borrow.rs.html#100-102' title='goto source code'>[src]</a></div><code>impl<'a, T> Borrow<T> for &'a mut T <span class="where fmt-newline">where<br> T: ?<a class="trait" href="../../core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>, </span></code></li>
<li><div class='out-of-band'><a class='srclink' href='../../src/core/array.rs.html#138-142' title='goto source code'>[src]</a></div><code>impl<T> Borrow<[T]> for [T; 15]</code></li>
<li><div class='out-of-band'><a class='srclink' href='../../src/core/array.rs.html#138-142' title='goto source code'>[src]</a></div><code>impl<T> Borrow<[T]> for [T; 14]</code></li>
<li><div class='out-of-band'><a class='srclink' href='../../src/core/array.rs.html#138-142' title='goto source code'>[src]</a></div><code>impl<T> Borrow<[T]> for [T; 4]</code></li>
<li><div class='out-of-band'><a class='srclink' href='../../src/core/array.rs.html#138-142' title='goto source code'>[src]</a></div><code>impl<T> Borrow<[T]> for [T; 21]</code></li>
<li><div class='out-of-band'><a class='srclink' href='../../src/core/array.rs.html#138-142' title='goto source code'>[src]</a></div><code>impl<T> Borrow<[T]> for [T; 31]</code></li>
<li><div class='out-of-band'><a class='srclink' href='../../src/core/array.rs.html#138-142' title='goto source code'>[src]</a></div><code>impl<T> Borrow<[T]> for [T; 5]</code></li>
<li><div class='out-of-band'><a class='srclink' href='../../src/core/array.rs.html#138-142' title='goto source code'>[src]</a></div><code>impl<T> Borrow<[T]> for [T; 25]</code></li>
<li><div class='out-of-band'><a class='srclink' href='../../src/core/array.rs.html#138-142' title='goto source code'>[src]</a></div><code>impl<T> Borrow<[T]> for [T; 22]</code></li>
<li><div class='out-of-band'><a class='srclink' href='../../src/core/array.rs.html#138-142' title='goto source code'>[src]</a></div><code>impl<T> Borrow<[T]> for [T; 10]</code></li>
<li><div class='out-of-band'><a class='srclink' href='../../src/core/array.rs.html#138-142' title='goto source code'>[src]</a></div><code>impl<T> Borrow<[T]> for [T; 6]</code></li>
<li><div class='out-of-band'><a class='srclink' href='../../src/core/array.rs.html#138-142' title='goto source code'>[src]</a></div><code>impl<T> Borrow<[T]> for [T; 16]</code></li>
<li><div class='out-of-band'><a class='srclink' href='../../src/core/array.rs.html#138-142' title='goto source code'>[src]</a></div><code>impl<T> Borrow<[T]> for [T; 8]</code></li>
<li><div class='out-of-band'><a class='srclink' href='../../src/core/array.rs.html#138-142' title='goto source code'>[src]</a></div><code>impl<T> Borrow<[T]> for [T; 32]</code></li>
<li><div class='out-of-band'><a class='srclink' href='../../src/alloc/borrow.rs.html#28-35' title='goto source code'>[src]</a></div><code>impl<'a, B: ?<a class="trait" href="../../core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>> Borrow<B> for <a class="enum" href="../../alloc/borrow/enum.Cow.html" title="enum alloc::borrow::Cow">Cow</a><'a, B> <span class="where fmt-newline">where<br> B: <a class="trait" href="../../alloc/borrow/trait.ToOwned.html" title="trait alloc::borrow::ToOwned">ToOwned</a>,<br> <B as <a class="trait" href="../../alloc/borrow/trait.ToOwned.html" title="trait alloc::borrow::ToOwned">ToOwned</a>>::<a class="type" href="../../alloc/borrow/trait.ToOwned.html#associatedtype.Owned" title="type alloc::borrow::ToOwned::Owned">Owned</a>: 'a, </span></code></li>
<li><div class='out-of-band'><a class='srclink' href='../../src/alloc/slice.rs.html#1923-1927' title='goto source code'>[src]</a></div><code>impl<T> Borrow<[T]> for <a class="struct" href="../../alloc/vec/struct.Vec.html" title="struct alloc::vec::Vec">Vec</a><T></code></li>
<li><div class='out-of-band'><a class='srclink' href='../../src/alloc/str.rs.html#178-183' title='goto source code'>[src]</a></div><code>impl Borrow<str> for <a class="struct" href="../../alloc/string/struct.String.html" title="struct alloc::string::String">String</a></code></li>
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