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<main>
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<h1 id="rust-新版解读--167--must_use-in-async-fn"><a class="header" href="#rust-新版解读--167--must_use-in-async-fn">Rust 新版解读 | 1.67 | <code>#[must_use]</code> in <code>async fn</code></a></h1>
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<blockquote>
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<p>Rust 1.67 官方 release doc: <a href="https://blog.rust-lang.org/2023/01/26/Rust-1.67.0.html">Announcing Rust 1.67.0 | Rust Blog</a></p>
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</blockquote>
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<p>通过 <a href="https://www.rust-lang.org/tools/install">rustup</a> 安装的同学可以使用以下命令升级到 1.67 版本:</p>
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<pre><code class="language-shell">$ rustup update stable
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</code></pre>
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<p>2023新年好！大年初五更新的新版本，来看看有什么新变化~</p>
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<h2 id="must_use-作用于-async-fn-上"><a class="header" href="#must_use-作用于-async-fn-上"><code>#[must_use]</code> 作用于 <code>async fn</code> 上</a></h2>
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<p>注明了 <code>#[must_use]</code> 的 <code>async</code> 函数会把该属性应用在返回的 <code>impl Future</code> 结果上。<code>Future</code> trait 已经注明了 <code>#[must_use]</code> ，所以所有实现了 <code>Future</code> 的类型都会自动加上 <code>#[must_use]</code>。</p>
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<p>所以在 1.67 版本，编译器会警告返回值没有被使用：</p>
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<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
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</span><span class="boring">fn main() {
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</span>#[must_use]
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async fn bar() -> u32 { 0 }
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async fn caller() {
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bar().await;
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}
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<span class="boring">}</span></code></pre></pre>
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<pre><code class="language-text">warning: unused output of future returned by `bar` that must be used
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--> src/lib.rs:5:5
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5 | bar().await;
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| ^^^^^^^^^^^
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= note: `#[warn(unused_must_use)]` on by default
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</code></pre>
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<h2 id="stdsyncmpsc-实现更新"><a class="header" href="#stdsyncmpsc-实现更新"><code>std::sync::mpsc</code> 实现更新</a></h2>
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<p>标准库里的 mpsc（多生产者单消费者） 通道自从 1.0 版本就有了，这次版本更新将其实现修改成了基于 <a href="https://crates.io/crates/crossbeam-channel"><code>crossbeam-channel</code></a>。不涉及到API的变更，但是修改了一些已有的bug，提升了性能和代码可维护性。用户应该不太会感知到明显的变化。</p>
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<h2 id="others"><a class="header" href="#others">Others</a></h2>
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<p>其它更新细节，和稳定的API列表，参考<a href="https://blog.rust-lang.org/2023/01/26/Rust-1.67.0.html#stabilized-apis">原Blog</a></p>
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