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<h1 id="rust-新版解读--164--重点-intofuture--cargo-优化"><a class="header" href="#rust-新版解读--164--重点-intofuture--cargo-优化">Rust 新版解读 | 1.64 | 重点: <code>IntoFuture</code> , Cargo 优化</a></h1>
<blockquote>
<p>Rust 1.64 官方 release doc: <a href="https://blog.rust-lang.org/2022/09/22/Rust-1.64.0.html">Announcing Rust 1.64.0 | Rust Blog</a></p>
</blockquote>
<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 1.64 版本:</p>
<pre><code class="language-shell">$ rustup update stable
</code></pre>
<h2 id="使用-intofuture-增强-await"><a class="header" href="#使用-intofuture-增强-await">使用 <code>IntoFuture</code> 增强 <code>.await</code></a></h2>
<p>1.64 稳定了 <code>IntoFuture</code> trait，不同于用在 <code>for ... in ...</code> 的 <code>IntoIterator</code> trait，<code>IntoFuture</code> 增强了 <code>.awiat</code> 关键字。现在 <code>.await</code> 可以 await 除了 futures 外，还可以 await 任何实现了 <code>IntoFuture</code> trait 并经此转换成 <code>Future</code> 的对象。这可以让你的 api 对用户更加优化。</p>
<p>举一个用在网络存储供应端的例子：</p>
<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span>pub struct Error { ... }
pub struct StorageResponse { ... }:
pub struct StorageRequest(bool);
impl StorageRequest {
/// 实例化一个 `StorageRequest`
pub fn new() -&gt; Self { ... }
/// 是否开启 debug 模式
pub fn set_debug(self, b: bool) -&gt; Self { ... }
/// 发送请求并接受回复
pub async fn send(self) -&gt; Result&lt;StorageResponse, Error&gt; { ... }
}
<span class="boring">}</span></code></pre></pre>
<p>通常地使用方法可能类似如下代码：</p>
<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span>let response = StorageRequest::new() // 1. 实例化
.set_debug(true) // 2. 设置一些选项
.send() // 3. 构造 future
.await?; // 4. 执行 future ，传递 error
<span class="boring">}</span></code></pre></pre>
<p>这个代码已经不错了，不过 1.64 后可以做的更好。使用 <code>IntoFuture</code> ，把第三步的 “构造 future ” 和 第四步的 “执行 future ” 合并到一个步骤里：</p>
<pre><code class="language-RUST">let response = StorageRequest::new() // 1. 实例化
.set_debug(true) // 2. 设置一些选项
.await?; // 3. 构造并执行 future ，传递 error
</code></pre>
<p>想要实现上面的效果，我们需要给 <code>StorageRequest</code> 实现 <code>IntoFuture</code> trait。<code>IntoFuture</code> 需要确定好要返回的 future，可以用下面的代码来实现：</p>
<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span>// 首先需要引入一些必须的类型
use std::pin::Pin;
use std::future::{Future, IntoFuture};
pub struct Error { ... }
pub struct StorageResponse { ... }
pub struct StorageRequest(bool);
impl StorageRequest {
/// 实例化一个 `StorageRequest`
pub fn new() -&gt; Self { ... }
/// 是否开启 debug 模式
pub fn set_debug(self, b: bool) -&gt; Self { ... }
/// 发送请求并接受回复
pub async fn send(self) -&gt; Result&lt;StorageResponse, Error&gt; { ... }
}
// 新的实现内容
// 1. 定义好返回的 future 类型
pub type StorageRequestFuture = Pin&lt;Box&lt;dyn Future&lt;Output = Result&lt;StorageResponse, Error&gt;&gt; + Send + 'static&gt;&gt;
// 2. 给 `StorageRequest` 实现 `IntoFuture`
impl IntoFuture for StorageRequest {
type IntoFuture = StorageRequestFuture;
type Output = &lt;StorageRequestFuture as Future&gt;::Output;
fn into_future(self) -&gt; Self::IntoFuture {
Box::pin(self.send())
}
}
<span class="boring">}</span></code></pre></pre>
<p>这确实需要多写一点实现代码，不过可以给用户提供一个更简单的 api 。</p>
<p>未来，Rust 异步团队 希望能够通过给类型别名提供 <code>impl Trait</code> <a href="https://rust-lang.github.io/impl-trait-initiative/explainer/tait.html">Type Alias Impl Trait</a>，来简化定义 futures 实现 <code>IntoFuture</code> 的代码；再想办法移除 <code>Box</code> 来提升性能。</p>
<h2 id="core-和-alloc-中和-c-语言兼容的-ffi-类型"><a class="header" href="#core-和-alloc-中和-c-语言兼容的-ffi-类型"><code>core</code> 和 <code>alloc</code> 中和 C 语言兼容的 FFI 类型</a></h2>
<p>当调用 C-ABI 或者调用 C-ABI 的时候，Rust 代码通常会使用诸如 <code>c_uint</code> 或者 <code>c_ulong</code> 的类型别名来匹配目标语言里的对应类型。</p>
<p>在次之前，这些类型别名仅在 <code>std</code> 里可用，而在嵌入式或者其它仅能使用 <code>core</code> 或者 <code>alloc</code> 的场景下无法使用。</p>
<p>1.64 里在 <code>core::ffi</code> 里提供了所有 <code>c_*</code> 的类型别名，还有 <code>core::ffi::CStr</code> 对应 C 的字符串，还有仅用 <code>alloc</code> 库情况下可以用 <code>alloc::ffi::CString</code> 来对应 C 的字符串。</p>
<h2 id="可以通过-rustup-来使用-rust-analyzer"><a class="header" href="#可以通过-rustup-来使用-rust-analyzer">可以通过 rustup 来使用 rust-analyzer</a></h2>
<p>rust-analyzer 现在被加进 Rust 工具集里了。这让在各平台上下载使用 rust-analyzer 更加方便。通过 <a href="https://rust-lang.github.io/rustup/concepts/components.html">rustup component</a> 来安装：</p>
<pre><code class="language-shell">rustup component add rust-analyzer
</code></pre>
<p>目前，使用 rustup 安装的版本，需要这样启用：</p>
<pre><code class="language-shell">rustup run stable rust-analyzer
</code></pre>
<p>下一次 rustup 的发布本把会提供一个内置的代理，来运行对应版本的 rust-analyzer 。</p>
<h2 id="cargo-优化workspace-继承和多目标构建"><a class="header" href="#cargo-优化workspace-继承和多目标构建">Cargo 优化，workspace 继承和多目标构建</a></h2>
<p>当在一个 Cargo workspace 里管理多个相关的库/产品时，现在可以避免在多个库里使用相同的字段值了，比如相同的版本号，仓库链接，<code>rust-version</code>。在更新的时候也可以更容易地保持这些信息地一致性。更多细节可以参考：</p>
<ul>
<li><a href="https://doc.rust-lang.org/cargo/reference/workspaces.html#the-package-table">workspace.package</a></li>
<li><a href="https://doc.rust-lang.org/cargo/reference/workspaces.html#the-dependencies-table">workspace.dependencies</a></li>
<li><a href="https://doc.rust-lang.org/cargo/reference/specifying-dependencies.html#inheriting-a-dependency-from-a-workspace">&quot;inheriting a dependency from a workspace&quot;</a></li>
</ul>
<p>另外在构建多个目标地时候，现在可以直接传递多个 <code>--target</code> 选项给 <code>cargo build</code> 来一次性编译所有目标。也可以在 <code>.cargo/config.toml</code> 里设置一个 <code>build.target</code> 的 array 来改变默认构建时的对象。</p>
<h2 id="稳定api--others"><a class="header" href="#稳定api--others">稳定API &amp;&amp; Others</a></h2>
<p>更多稳定API列表和其它更新内容，请参考原文最后 <a href="https://blog.rust-lang.org/2022/09/22/Rust-1.64.0.html#stabilized-apis">stabilized-apis</a></p>
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