{"id":45431,"date":"2023-05-05T10:30:48","date_gmt":"2023-04-15T03:40:36","guid":{"rendered":"https:\/\/www.silicloud.com\/zh\/blog\/45431-2\/"},"modified":"2024-04-30T02:43:43","modified_gmt":"2024-04-29T18:43:43","slug":"45431-2","status":"publish","type":"post","link":"https:\/\/www.silicloud.com\/zh\/blog\/45431-2\/","title":{"rendered":""},"content":{"rendered":"

\u672c\u8a18\u4e8b\u306fRust Advent Calendar 2022\u306e13\u65e5\u76ee\u306e\u8a18\u4e8b\u3067\u3059\u3002<\/p>\n

\u672c\u8a18\u4e8b\u3067\u306f\u3001\u6a19\u6e96\u7684\u306aRust\u306e\u6559\u6750\u3067\u306f\u3042\u307e\u308a\u89e6\u308c\u3089\u308c\u306a\u3044\u3001Rust\u306eUnstable(experimental)\u6a5f\u80fd\u306b\u3064\u3044\u3066\u89e3\u8aac\u3057\u3066\u3044\u304d\u307e\u3059\u3002
\n\u307e\u305a\u3001unstable\u6a5f\u80fd\u3068\u3044\u3046\u3082\u306e\u306e\u5b58\u5728\u610f\u7fa9\u304b\u3089\u8aac\u660e\u3057\u307e\u3059\u3002\u306a\u3093\u3068\u306a\u304f\u77e5\u3063\u3066\u3044\u308b\u4eba\u306f\u98db\u3070\u3057\u3066\u69cb\u3044\u307e\u305b\u3093\u3002<\/p>\n

Rust\u306f”Empowering everyone to build reliable and efficient software.”\u3068\u3044\u3046\u30ad\u30e3\u30c3\u30c1\u30b3\u30d4\u30fc\u304b\u3089\u5206\u304b\u308b\u901a\u308a\u3001\u5805\u7262\u3055\u3092\u58f2\u308a\u306e\u4e00\u3064\u3068\u3057\u3066\u304a\u308a\u3001\u5f37\u3044\u5f8c\u65b9\u4e92\u63db\u6027\u3068\u5b89\u5b9a\u6027\u3092\u4fdd\u8a3c\u3057\u307e\u3059\u3002\u3057\u304b\u3057\u3053\u306e\u30b9\u30bf\u30f3\u30b9\u306f\u958b\u767a\u306e\u9045\u6ede\u5316\u3092\u62db\u304d\u304b\u306d\u306a\u3044\u3068\u3044\u3046\u30c7\u30e1\u30ea\u30c3\u30c8\u3082\u3042\u308a\u307e\u3059\u3002
\n\u305d\u3053\u3067\u3001Rust\u306f\u30b3\u30f3\u30d1\u30a4\u30e9\u306b\u3064\u3044\u3066nightly\/beta\/stable\u306e3\u30d0\u30fc\u30b8\u30e7\u30f3\u3092\u516c\u958b\u3057\u3066\u3044\u307e\u3059\u3002nightly\u30d0\u30fc\u30b8\u30e7\u30f3\u306f\u307b\u307c\u6700\u3082\u4e0d\u5b89\u5b9a\u3067\u3001\u6700\u3082\u65e9\u304f\u6700\u65b0\u306e\u6a5f\u80fd\u3092\u8a66\u305b\u307e\u3059\u3002\u305d\u308c\u304cunstable\u6a5f\u80fd\u3067\u3059\u3002\u4e00\u822c\u306e\u30e6\u30fc\u30b6\u30fc\u306b\u3082\u4e0d\u5b89\u5b9a\u306a\u6a5f\u80fd\u3092\u516c\u958b\u3057\u3001\u30d0\u30b0\u304c\u306a\u3044\u304b\u691c\u8a3c\u3057\u3066\u3082\u3089\u304a\u3046\u3068\u3044\u3046\u8a33\u3067\u3059\u3002<\/p>\n

unstable\u6a5f\u80fd\u306fbeta\/stable\u30b3\u30f3\u30d1\u30a4\u30e9\u3067\u306f\u4f7f\u3048\u305a\u3001nightly\u7248\u30b3\u30f3\u30d1\u30a4\u30e9\u3067\u306e\u307f\u4f7f\u3048\u307e\u3059\u3002\u3057\u304b\u3082\u30c7\u30d5\u30a9\u30eb\u30c8\u3067\u306f\u4f7f\u3048\u305a\u3001#![feature(…)]\u30a2\u30c8\u30ea\u30d3\u30e5\u30fc\u30c8\u3067\u5ba3\u8a00\u3057\u306a\u3051\u308c\u3070\u306a\u308a\u307e\u305b\u3093\u3002nightly\u3067\u3042\u3063\u3066\u3082\u4e0d\u7528\u610f\u306b\u30b3\u30fc\u30c9\u304c\u58ca\u308c\u306a\u3044\u3088\u3046\u306b\u7d30\u5fc3\u306e\u6ce8\u610f\u3092\u6255\u3046Rust\u306e\u601d\u60f3\u304c\u57a3\u9593\u898b\u3048\u307e\u3059\u3002<\/p>\n

Rust\u306eunstable\u6a5f\u80fd\u306e\u4e00\u89a7\u306fThe Unstable Book\u304b\u3089\u78ba\u8a8d\u3067\u304d\u307e\u3059\u3002\u3056\u3063\u3068400\u500b\u307b\u3069\u3082\u3042\u308b\u3088\u3046\u3067\u3059\u3002\u4ee5\u4e0b\u3067\u306f\u305d\u306e\u4e2d\u306e\u4e00\u90e8\u3092\u30d4\u30c3\u30af\u30a2\u30c3\u30d7\u3057\u3066\u7d39\u4ecb\u3057\u307e\u3059\u3002<\/p>\n

\u6ce8\u76ee\u306eunstable\u6a5f\u80fd<\/h1>\n

box_patterns<\/h2>\n
#![feature(box_patterns)]<\/span>\r\n\/\/ x: Option<Box<X>><\/span>\r\nmatch<\/span> x<\/span> {<\/span>\r\n    Some<\/span>(<\/span>inner<\/span>)<\/span> =><\/span> {<\/span>\r\n        let<\/span> inner<\/span> =<\/span> *<\/span>inner<\/span>;<\/span>\r\n        ...<\/span>\r\n    }<\/span>\r\n    ...<\/span>\r\n}<\/span>\r\n\/\/ \u2193<\/span>\r\nmatch<\/span> x<\/span> {<\/span>\r\n    Some<\/span>(<\/span>box<\/span> inner<\/span>)<\/span> =><\/span> {<\/span>\r\n        ...<\/span>\r\n    }<\/span>\r\n    ...<\/span>\r\n}<\/span>\r\n<\/code><\/pre>\n
\u30d1\u30bf\u30fc\u30f3\u30de\u30c3\u30c1\u30f3\u30b0\u3067Box\u578b\u306e\u4e2d\u8eab\u3092\u53d6\u308a\u51fa\u3059\u3053\u3068\u304c\u3067\u304d\u308b\u3088\u3046\u306b\u306a\u308a\u307e\u3059\u3002ref\u30d1\u30bf\u30fc\u30f3\u3068\u4f3c\u305f\u3088\u3046\u306a\u611f\u3058\u3067\u3059\u306d\u3002<\/p>\n
box_syntax<\/h2>\n
#![feature(box_syntax)]<\/span>\r\nlet<\/span> boxed<\/span>:<\/span> Box<\/span><<\/span>Str<\/span>><\/span> =<\/span> Box<\/span>::<\/span>new<\/span>(<\/span>\"aaa\"<\/span>);<\/span>\r\n\/\/ \u2193<\/span>\r\nlet<\/span> boxed<\/span>:<\/span> Box<\/span><<\/span>str<\/span>><\/span> =<\/span> box<\/span> \"aaa\"<\/span>;<\/span>\r\n<\/code><\/pre>\n
box\u3068\u3044\u3046\u30ad\u30fc\u30ef\u30fc\u30c9\u304c\u8ffd\u52a0\u3055\u308c\u3001Box::new\u306e\u4ee3\u308f\u308a\u306b\u4f7f\u3046\u3053\u3068\u304c\u51fa\u6765\u307e\u3059\u3002
\n……\u3068\u3044\u3046\u3060\u3051\u306e\u6a5f\u80fd\u306b\u898b\u3048\u307e\u3059\u304c\u3001\u306a\u3093\u3068\u3053\u306e\u6a5f\u80fd\u30017\u5e74\u4ee5\u4e0a\u3082unstable\u306e\u307e\u307e\u3068\u3044\u3046\u6ce5\u6cbc\u72b6\u614b\u3068\u306a\u3063\u3066\u3044\u307e\u3059\u3002
\n\u8abf\u3079\u3066\u307f\u305f\u3068\u3053\u308d\u3001box syntax\u306f\u5358\u306a\u308bBox::new\u306e\u69cb\u6587\u7cd6\u3067\u306f\u306a\u3044\u3088\u3046\u3067\u3059\u3002Box\u578b\u306f\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u3092\u30d2\u30fc\u30d7\u306b\u914d\u7f6e\u3059\u308b\u30dd\u30a4\u30f3\u30bf\u578b\u3067\u3059\u304c\u3001Box::new\u3092\u4f7f\u3046\u5834\u5408\u3001\u5f15\u6570\u3092\u4e00\u5ea6\u30b9\u30bf\u30c3\u30af\u306b\u7f6e\u304f\u5fc5\u8981\u304c\u3042\u308b\u3088\u3046\u3067\u3059\u3002\u3053\u308c\u306f\u30b9\u30bf\u30c3\u30af\u30b5\u30a4\u30ba\u304c\u5c0f\u3055\u3044\u74b0\u5883\u3067\u5927\u304d\u306a\u69cb\u9020\u4f53\u3092\u751f\u6210\u3059\u308b\u969b\u306b\u554f\u984c\u3068\u306a\u308a\u307e\u3059\u3002box\u306f\u305d\u308c\u3092\u6700\u9069\u5316\u3057\u3001\u30b9\u30bf\u30c3\u30af\u3092\u7d4c\u7531\u305b\u305a\u76f4\u63a5\u30d2\u30fc\u30d7\u306b\u914d\u7f6e\u3059\u308b\u305f\u3081\u306e\u69cb\u6587\u3068\u3044\u3046\u308f\u3051\u3067\u3059\u3002<\/p>\n
(\u3057\u304b\u3057\u3001\u305d\u308c\u306a\u3089\u3053\u306e\u6a5f\u80fd\u306f\u5358\u306b\u5185\u90e8\u5b9f\u88c5\u306e\u5909\u66f4\u3067\u3042\u308a\u3001Box::new\u3092\u5dee\u3057\u7f6e\u3044\u3066box\u3068\u3044\u3046\u69cb\u6587\u3092\u308f\u3056\u308f\u3056\u5165\u308c\u308b\u5fc5\u8981\u3082\u306a\u3044\u3088\u3046\u306a\u6c17\u3082\u3057\u307e\u3059\u3002Box::new\u306f\u95a2\u6570\u306a\u306e\u3067\u3001\u4f7f\u3048\u3066\u3057\u307e\u3046\u5834\u6240\u304c\u591a\u3044=\u6700\u9069\u5316\u3057\u306b\u304f\u3044\u306e\u304c\u554f\u984c\u306a\u306e\u3067\u3057\u3087\u3046\u304b\u3002)<\/p>\n
\u8ffd\u8a18: \u3084\u306f\u308a\u3042\u307e\u308a\u610f\u5473\u304c\u306a\u3044\u3068\u3044\u3046\u3053\u3068\u3067stable\u306b\u5165\u3089\u306a\u3044\u307e\u307e\u524a\u9664\u3068\u3044\u3046\u904b\u3073\u306b\u306a\u3063\u305f\u3088\u3046\u3067\u3059\u3002
\nhttps:\/\/github.com\/rust-lang\/rust\/pull\/108471<\/p><\/blockquote>\n
generators<\/h2>\n
#![feature(generators,<\/span> generator_trait)]<\/span>\r\n\r\nuse<\/span> std<\/span>::<\/span>ops<\/span>::{<\/span>Generator<\/span>,<\/span> GeneratorState<\/span>};<\/span>\r\nuse<\/span> std<\/span>::<\/span>pin<\/span>::<\/span>Pin<\/span>;<\/span>\r\n\r\nfn<\/span> main<\/span>()<\/span> {<\/span>\r\n    let<\/span> mut<\/span> generator<\/span> =<\/span> ||<\/span> {<\/span>\r\n        yield<\/span> 1<\/span>;<\/span>\r\n        return<\/span> \"foo\"<\/span>\r\n    };<\/span>\r\n\r\n    match<\/span> Pin<\/span>::<\/span>new<\/span>(<\/span>&<\/span>mut<\/span> generator<\/span>)<\/span>.resume<\/span>(())<\/span> {<\/span>\r\n        GeneratorState<\/span>::<\/span>Yielded<\/span>(<\/span>1<\/span>)<\/span> =><\/span> {}<\/span>\r\n        _<\/span> =><\/span> panic!<\/span>(<\/span>\"unexpected value from resume\"<\/span>),<\/span>\r\n    }<\/span>\r\n    match<\/span> Pin<\/span>::<\/span>new<\/span>(<\/span>&<\/span>mut<\/span> generator<\/span>)<\/span>.resume<\/span>(())<\/span> {<\/span>\r\n        GeneratorState<\/span>::<\/span>Complete<\/span>(<\/span>\"foo\"<\/span>)<\/span> =><\/span> {}<\/span>\r\n        _<\/span> =><\/span> panic!<\/span>(<\/span>\"unexpected value from resume\"<\/span>),<\/span>\r\n    }<\/span>\r\n}<\/span>\r\n<\/code><\/pre>\n
Python\u306e\u30b8\u30a7\u30cd\u30ec\u30fc\u30bf\u306e\u3088\u3046\u306a\u3053\u3068\u304c\u51fa\u6765\u308b\u3088\u3046\u306b\u306a\u308a\u307e\u3059\u3002\u3059\u306a\u308f\u3061\u3001yield\u3067\u95a2\u6570\u3092\u4e00\u6642\u4e2d\u65ad\u3057\u3066\u3001\u518d\u5ea6\u547c\u3073\u51fa\u3057\u305f\u969b\u306b\u305d\u3053\u304b\u3089\u518d\u958b\u3067\u304d\u308b\u3068\u3044\u3046\u3053\u3068\u3067\u3059\u3002
\n\u30af\u30ed\u30fc\u30b8\u30e3\u3063\u307d\u304f\u898b\u3048\u307e\u3059\u304c\u3001Generetor\u30c8\u30ec\u30a4\u30c8\u3092\u5b9f\u88c5\u3059\u308b\u5225\u306e\u30ea\u30c6\u30e9\u30eb\u3068\u3057\u3066\u6271\u308f\u308c\u308b\u3088\u3046\u3067\u3059\u3002<\/p>\n
once_cell<\/h2>\n
\u73fe\u5728\u306eRust\u306f\u3001const\u5f0f\u4ee5\u5916\u3067\u5b89\u5168\u306b\u30b0\u30ed\u30fc\u30d0\u30eb\u30c7\u30fc\u30bf\u3092\u4fdd\u7ba1\u3059\u308b\u6a19\u6e96\u7684\u306a\u65b9\u6cd5\u3092\u307b\u307c\u63d0\u4f9b\u3057\u307e\u305b\u3093\u3002\u5916\u90e8crate\u306b\u983c\u308b\u5fc5\u8981\u304c\u3042\u308a\u307e\u3059\u3002once_cell\u306f\u305d\u306e\u4e00\u3064\u3067\u3059\u3002\u9045\u5ef6\u521d\u671f\u5316\u306b\u3088\u3063\u3066\u5b9f\u884c\u6642\u307e\u3067\u78ba\u5b9a\u3057\u306a\u3044\u5024\u3067\u3082const\u306b\u30d0\u30a4\u30f3\u30c9\u3067\u304d\u308b\u3088\u3046\u306b\u306a\u308a\u307e\u3059\u3002\u672c\u6a5f\u80fd\u306fonce_cell\u3092std\u306b\u5165\u308c\u308b\u3082\u306e\u3067\u3059\u3002<\/p>\n
use<\/span> std<\/span>::<\/span>sync<\/span>::<\/span>Lazy<\/span>;<\/span>\r\n\r\n\/\/ `BACKTRACE` implements `Deref<Target = Option<String>>` <\/span>\r\n\/\/ and is initialized on the first access<\/span>\r\nstatic<\/span> BACKTRACE<\/span>:<\/span> Lazy<\/span><<\/span>Option<\/span><<\/span>String<\/span>>><\/span> =<\/span> Lazy<\/span>::<\/span>new<\/span>(||<\/span> {<\/span>\r\n    std<\/span>::<\/span>env<\/span>::<\/span>var<\/span>(<\/span>\"RUST_BACKTRACE\"<\/span>)<\/span>.ok<\/span>()<\/span>\r\n});<\/span>\r\n<\/code><\/pre>\n
result_option_*<\/h2>\n
Option\/Result\u578b\u306b\u306f\u4fbf\u5229\u306aunstable\u30e1\u30bd\u30c3\u30c9\u304c\u5e7e\u3064\u304b\u751f\u3048\u3066\u3044\u307e\u3059\u3002\u305d\u306e\u4e00\u90e8\u3092\u7d39\u4ecb\u3057\u307e\u3059\u3002<\/p>\n
inspect<\/h3>\n
Option\u306e\u4e2d\u8eab\u3092\u8997\u304f\u3053\u3068\u304c\u3067\u304d\u307e\u3059\u3002.map(|x| {…; x})\u306eshort-hand\u3067\u3059\u3002<\/p>\n
#![feature(result_option_inspect)]<\/span>\r\n\r\nlet<\/span> x<\/span>:<\/span> Option<\/span><&<\/span>usize<\/span>><\/span> =<\/span> Some<\/span>(<\/span>1<\/span>)<\/span>.inspect<\/span>(|<\/span>x<\/span>|<\/span> println!<\/span>(<\/span>\"inner: {x}\"<\/span>));<\/span> \/\/ inner: 1<\/span>\r\n<\/code><\/pre>\n
unzip<\/h3>\n
Option<(T, U)>\u578b\u306b\u5bfe\u3057\u3066\u5b9a\u7fa9\u3055\u308c\u308b\u30e1\u30bd\u30c3\u30c9\u3067\u3001\u4e2d\u8eab\u30922\u3064\u306eOption\u306b\u5206\u89e3\u3067\u304d\u307e\u3059\u3002<\/p>\n
#![feature(unzip_option)]<\/span>\r\n\r\nlet<\/span> x<\/span> =<\/span> Some<\/span>((<\/span>1<\/span>,<\/span> \"hi\"<\/span>));<\/span>\r\nassert_eq!<\/span>(<\/span>x<\/span>.unzip<\/span>(),<\/span> (<\/span>Some<\/span>(<\/span>1<\/span>),<\/span> Some<\/span>(<\/span>\"hi\"<\/span>)));<\/span>\r\n<\/code><\/pre>\n
\u8ffd\u8a18: Rust 1.66\u3067stabilize\u3055\u308c\u307e\u3057\u305f\u3002<\/p><\/blockquote>\n
closure_lifetime_binder<\/h2>\n
fn<\/span> func<\/span>(<\/span>_<\/span>:<\/span> impl<\/span> Fn<\/span>(<\/span>&<\/span>i32<\/span>)<\/span> -><\/span> &<\/span>i32<\/span>)<\/span> {}<\/span>\r\n\r\nfn<\/span> main<\/span>()<\/span> {<\/span>\r\n    func<\/span>(<\/span>for<\/span><<\/span>'a<\/span>><\/span> |<\/span>arg<\/span>:<\/span> &<\/span>'a<\/span> i32<\/span>|<\/span> -><\/span> &<\/span>'a<\/span> i32<\/span> {<\/span> arg<\/span> });<\/span>\r\n}<\/span>\r\n<\/code><\/pre>\n
\u30af\u30ed\u30fc\u30b8\u30e3\u3067\u30e9\u30a4\u30d5\u30bf\u30a4\u30e0\u6307\u5b9a\u304c\u51fa\u6765\u308b\u3088\u3046\u306b\u306a\u308a\u307e\u3059\u3002for\u3092\u4f7f\u3046\u306e\u306f\u3061\u3087\u3063\u3068\u6c17\u6301\u3061\u60aa\u3044\u3067\u3059\u306d\u3002\u307e\u3042impl ~ for\u3067\u3082\u4f7f\u308f\u308c\u3066\u3044\u307e\u3059\u304c\u3002<\/p>\n
concat_idents<\/h2>\n
let<\/span> foo_1<\/span> =<\/span> 1<\/span>;<\/span>\r\nlet<\/span> foo_2<\/span> =<\/span> 2<\/span>;<\/span>\r\nassert!<\/span>(<\/span>concat_idents!<\/span>(<\/span>foo<\/span>,<\/span> _1<\/span>)<\/span> ==<\/span> 1<\/span>);<\/span>\r\nassert!<\/span>(<\/span>concat_idents!<\/span>(<\/span>foo<\/span>,<\/span> _2<\/span>)<\/span> ==<\/span> 2<\/span>);<\/span>\r\n<\/code><\/pre>\n
\u8b58\u5225\u5b50\u3092\u7d50\u5408\u3059\u308b\u3053\u3068\u304c\u51fa\u6765\u307e\u3059\u3002\u30de\u30af\u30ed\u3092\u4f5c\u308b\u3068\u304d\u306b\u306f\u5f79\u306b\u7acb\u3064\u304b\u3082\u3057\u308c\u307e\u305b\u3093\u3002\u304c\u3001\u500b\u4eba\u7684\u306b\u306f\u3053\u306e\u3088\u3046\u306a\u3053\u3068\u3092\u3059\u308b\u306a\u3089\u3070\u914d\u5217\u304bconst function\u3092\u4ee3\u308f\u308a\u306b\u4f7f\u3063\u305f\u307b\u3046\u304c\u826f\u3044\u3068\u611f\u3058\u307e\u3059\u3002<\/p>\n
\u6700\u8fd1\u5b89\u5b9a\u5316\u3055\u308c\u305f\u6a5f\u80fd<\/h1>\n
\u6700\u8fd1(ver 1.62~)\u5b89\u5b9a\u5316\u3055\u308c\u305f\u6a5f\u80fd\u306e\u4e2d\u3067\u500b\u4eba\u7684\u306b\u4fbf\u5229\u3060\u3068\u611f\u3058\u305f\u3082\u306e\u3092\u30d4\u30c3\u30af\u30a2\u30c3\u30d7\u3057\u307e\u3059\u3002<\/p>\n
const_panic<\/h2>\n
const\u6587\u8108\u3067panic\u304c\u51fa\u6765\u307e\u3059\u3002\u305f\u3060\u3057\u307e\u3060formatting\u306f\u51fa\u6765\u307e\u305b\u3093\u3002<\/p>\n
#[repr(u8)]<\/span>\r\nenum<\/span> E<\/span> {<\/span>\r\n    A<\/span> =<\/span> 1<\/span>,<\/span>\r\n    B<\/span> =<\/span> 2<\/span>,<\/span>\r\n    ...<\/span>\r\n}<\/span>\r\n\r\nimpl<\/span> E<\/span> {<\/span>\r\n    const<\/span> fn<\/span> from_byte<\/span>(<\/span>b<\/span>:<\/span> u8<\/span>)<\/span> -><\/span> E<\/span> {<\/span>\r\n        match<\/span> b<\/span> {<\/span>\r\n            1<\/span> =><\/span> E<\/span>::<\/span>A<\/span>,<\/span>\r\n            ...<\/span>\r\n            _<\/span> =><\/span> panic!<\/span>(<\/span>\"invalid input\"<\/span>),<\/span>\r\n        }<\/span>\r\n    }<\/span>\r\n}<\/span>\r\n<\/code><\/pre>\n
let_else<\/h2>\n
x<\/span>:<\/span> Result<\/span><<\/span>Option<\/span><<\/span>X<\/span>>><\/span>\r\nif<\/span> let<\/span> Ok<\/span>(<\/span>Some<\/span>(<\/span>inner<\/span>))<\/span> =<\/span> x<\/span> {<\/span> inner<\/span> }<\/span> else<\/span> {<\/span> todo!<\/span>()<\/span> };<\/span>\r\n\/\/ \u2193<\/span>\r\nlet<\/span> Ok<\/span>(<\/span>Some<\/span>(<\/span>inner<\/span>))<\/span> =<\/span> x<\/span> else<\/span> {<\/span> todo!<\/span>()<\/span> };<\/span> \r\n<\/code><\/pre>\n
else\u5185\u306f\u767a\u6563\u3059\u308b\u9805(!\u578b\u306e\u9805\u3002panic!\u3084\u7121\u9650\u30eb\u30fc\u30d7\u306a\u3069\u901a\u5e38\u306e\u5024\u3092\u8fd4\u3055\u306a\u3044)\u3067\u306a\u304f\u3066\u306f\u306a\u308a\u307e\u305b\u3093\u3002<\/p>\n
derive_default_enum<\/h2>\n
#[derive(Default)]<\/span>\r\nenum<\/span> Type<\/span> {<\/span>\r\n   Int<\/span>,<\/span>\r\n   Bool<\/span>,<\/span>\r\n   ...<\/span>\r\n   #[default]<\/span>\r\n   Illegal<\/span>,<\/span>\r\n}<\/span>\r\n\r\nfn<\/span> main<\/span>()<\/span> {<\/span>\r\n   let<\/span> mut<\/span> v<\/span> =<\/span> vec!<\/span>[<\/span>Type<\/span>::<\/span>Int<\/span>];<\/span>\r\n   v<\/span>.resize_with<\/span>(<\/span>3<\/span>,<\/span> Default<\/span>::<\/span>default<\/span>);<\/span>\r\nassert_eq!<\/span>(<\/span>v<\/span>,<\/span> [<\/span>Type<\/span>::<\/span>Int<\/span>,<\/span> Type<\/span>::<\/span>Illegal<\/span>,<\/span> Type<\/span>::<\/span>Illegal<\/span>]);<\/span>\r\n}<\/span>\r\n<\/code><\/pre>\n
enum\u306e\u9078\u629e\u80a2\u306e\u4e00\u3064\u306b#[default]\u5c5e\u6027\u3092\u3064\u3051\u308b\u3068\u3001Default::default()\u3067\u305d\u308c\u3092\u8fd4\u3059\u3088\u3046\u306b\u306a\u308a\u307e\u3059\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"
\u672c\u8a18\u4e8b\u306fRust Advent Calendar 2022\u306e13\u65e5\u76ee\u306e\u8a18\u4e8b\u3067\u3059\u3002 \u672c\u8a18\u4e8b\u3067\u306f\u3001\u6a19\u6e96\u7684\u306aRust […]<\/p>\n","protected":false},"author":10,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-45431","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"yoast_head":"\n- Blog - Silicon Cloud<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.silicloud.com\/zh\/blog\/45431-2\/\" \/>\n<meta property=\"og:locale\" content=\"zh_CN\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:description\" content=\"\u672c\u8a18\u4e8b\u306fRust Advent Calendar 2022\u306e13\u65e5\u76ee\u306e\u8a18\u4e8b\u3067\u3059\u3002 \u672c\u8a18\u4e8b\u3067\u306f\u3001\u6a19\u6e96\u7684\u306aRust […]\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.silicloud.com\/zh\/blog\/45431-2\/\" \/>\n<meta property=\"og:site_name\" content=\"Blog - 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