Rust 1.39を早めに深掘り

Rust
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こんにちは、R&Dチームの齋藤（@aznhe21）です。 先日、Rust.Tokyoに行ってきました。この手のイベントは初めてだったんですが、なかなか楽しいものですね。 当日は「いつの間にか社の中核製品にRustが使われていた件について」という題で、 オプティムがどのような製品にRustを採用しているのかの発表もしてきました。 発表に使用した資料は下記にアップしてありますので、 もう一度見たい方、あるいは当日参加出来なかったので資料だけでも見たい、という方はぜひご覧ください！

さて、本日、日本時間11/8(金)、Rust 1.39がリリースされました。 この記事ではRust 1.39での変更点を詳しく紹介します。 なお、この記事は公式リリースノートをベースに、意訳・追記をしています。

栗ご飯とRust

ピックアップ

個人的に注目する変更点を「ピックアップ」としてまとめました。 全ての変更点を網羅したリストは変更点リストをご覧ください。

async/awaitが安定化した

全Rustacean待望の機能がついに入りました。 Rust 1.36で入ったFutureがようやく日の目を見ることになります。

これにより、非同期プログラミングが格段に楽になります。 この非同期プログラミングについては別途解説記事を書いておりますので、そちらもご覧ください！

関数の引数にも属性が書けるようになった

すべての属性ではありませんが、関数やクロージャー、あるいは関数ポインタ型（type X = fn(i32) -> i32;など）の引数の部分に、 属性が書けるようになりました。

これにより、手続きマクロと組み合わせて、引数にあらゆる情報を埋め込むことが出来るようになりました。 以下のコードは、Rustで書いたコードからTypeScriptの定義ファイルを出力する例です。

#[wasm_bindgen]
impl RustLayoutEngine {
    #[wasm_bindgen(constructor)]
    pub fn new() -> Self { Default::default() }

    // TypeScript向け：戻り値の型は`MapNode[]`
    #[wasm_bindgen(typescript(return_type = "MapNode[]"))]
    pub fn layout(
        &self, 
        // TypeScript向け：nodesの型は`MapNode[]`
        #[wasm_bindgen(typescript(type = "MapNode[]"))]
        nodes: Vec<JsValue>, 
        // TypeScript向け：edgesの型は`MapEdge[]`
        #[wasm_bindgen(typescript(type = "MapEdge[]"))]
        edges: Vec<JsValue>
    ) -> Vec<JsValue> {
        ..
    }
}

また、プラットフォームごとに異なる引数を付けるということも出来るでしょう。

fn len(
    #[cfg(windows)] slice: &[u16],
    #[cfg(not(windows))] slice: &[u8],
) -> usize {
    slice.len()
}

matchでムーブしつつ条件を書けるようになった

match式の中で、ムーブしつつifで条件を書くことが出来るようになりました。

let s = Some("hoge".to_string());
match s {
    Some(x) if x == "hoge" => {
        println!("This is hoge");
    }
    Some(x) if x == "fuga" => {
        println!("This is fuga");
    }
    Some(x) => {
        println!("Nice to meet you, {}!", x);
    }
    None => {
        println!("John Doe");
    }
}

これまでは、中身の値を持ち出したいときは参照でパターンマッチさせつつクローンするか、 所有権を奪いたいときはifで頑張って絞り込んでいくしかありませんでした。

変更点リスト

言語

コンパイラ

* RustのTierによるプラットフォームサポートの詳細はプラットフォームサポートのページを参照 ※訳注：英語ページ

ライブラリ

安定化されたAPI

Pin::into_inner

Pin<P>が保持するポインターを取り出す。

これは、内部のデータがUnpinである必要がある。 これによって、データを取り出す際に不変値のピン留めを無視することが出来る。

Instant::{checked,saturating}_duration_since

引数として与えられたInstantからの経過時間を返す。 オブジェクトよりも与えられた引数のほうが早い時間を示していた場合、 checked_duration_sinceはNoneを返し、saturating_duration_sinceはゼロを返す。

Cargo

その他

互換性メモ

関連リンク

さいごに

今回はすべてのリソースをasync/awaitに注ぎ込んだのか、それ以外の変更点は少ないリリースとなりました。 でもそれだけの価値のある機能です。これでRustが採用される事例も格段に増えるでしょう。

次のRust 1.40は12/20(金)に予定されています。 今までNightlyでしか使えなかった多くの機能が安定化されるようで、楽しみです。

オプティムでは秋と言えば食欲なエンジニアを募集しています。

ライセンス表記

  • この記事はApache 2/MITのデュアルライセンスで公開されている公式リリースノートを翻訳・追記をしています
  • 冒頭の画像中にはRust公式サイトで配布されているロゴを使用しており、 このロゴはMozillaによってCC-BYの下で配布されています
  • 冒頭の画像はいらすとやさんの画像を使っています。いつもありがとうございます

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*1:実際には定義されておらず、手続きマクロに情報を与えることだけを目的とする属性。 手続きマクロによってアイテムが処理される際に消える