Rust 2021版計劃於10月發佈，將帶來哪些新特性？

{"type":"doc","content":[{"type":"blockquote","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"Rust 語言的第三版，即 Rust 2021，計劃在 10 月發佈。Rust 2021 包含了一些微小的變化，儘管如此，在實際應用中，它們仍有望顯著改善 Rust 的感覺。"}]}]},{"type":"heading","attrs":{"align":null,"level":2},"content":[{"type":"text","text":"什麼是版本？"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"作爲 Rust 的更新原則， Rust1.0 的發佈確立了一個“"},{"type":"link","attrs":{"href":"https:\/\/blog.rust-lang.org\/2014\/10\/30\/Stability.html","title":null,"type":null},"content":[{"type":"text","text":"穩定前進"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"”（stability without stagnation）。從 1.0 版本開始，Rust 的規則是，一旦某個特性在穩定版上發佈，我們將保證在以後的所有版本中都支持它。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"但是，有些時候，能夠對語言做一些不向後兼容的小改動是很有用的。一個顯而易見的例子是引入一個新的關鍵字，它會使同名變量無效。比如，Rust 的第一個版本中就沒有 "},{"type":"codeinline","content":[{"type":"text","text":"async"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" 和 "},{"type":"codeinline","content":[{"type":"text","text":"await"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" 這兩個關鍵字。如果這些關鍵字在以後的版本中突然變成關鍵字，那麼就會破壞類似 "},{"type":"codeinline","content":[{"type":"text","text":"let async = 1;"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" 的代碼。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}},{"type":"strong"}],"text":"版本"},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"就是我們解決這個問題的機制。當我們想要發佈一個本來是向後不兼容的特性時，我們就把它作爲新的 Rust 版本的一部分。版本是可以選擇的，因此現有包（crate）不會看到這些更改，除非明確地將其遷移到新版本上。這就是說，除非選擇 2018 版或更新版本，即使是最新版本的 Rust 也不會把 "},{"type":"codeinline","content":[{"type":"text","text":"async"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" 作爲關鍵字。對於每個包，這個選擇都是 "},{"type":"codeinline","content":[{"type":"text","text":"Cargo.toml"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" 的一部分。"},{"type":"codeinline","content":[{"type":"text","text":"cargo new"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"創建的新包始終配置爲使用最新穩定版本。"}]},{"type":"heading","attrs":{"align":null,"level":2},"content":[{"type":"text","text":"版本不會分裂生態系統"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"對於版本來說，最重要的規則是，一個版本中的包可以與其他版本中編譯的包無縫地互操作。這樣就保證了將包遷移到一個更新版本的決策是一個“私有決策”，這個決策可以在不影響他人的情況下進行。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"對包互操作性的需求意味着對我們在一個版本中所能做的各種更改有一些限制。一般而言，一個版本中發生的更改往往是“皮毛”。但無論哪種版本，所有的 Rust 代碼最終都會被編譯成編譯器中相同的內部表示。"}]},{"type":"heading","attrs":{"align":null,"level":2},"content":[{"type":"text","text":"版本遷移很容易，並且基本上是自動化的"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"我們的目標是使包能夠輕鬆地升級到新的版本。在發佈新版本時，我們還提供了"},{"type":"link","attrs":{"href":"https:\/\/doc.rust-lang.org\/cargo\/commands\/cargo-fix.html","title":null,"type":null},"content":[{"type":"text","text":"自動遷移的工具"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"。對代碼進行一些必要的小改動，使之與新版本兼容。舉例來說，在遷移到 Rust 2018 時，它將所有稱爲 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的東西都使用了等效的"},{"type":"link","attrs":{"href":"https:\/\/doc.rust-lang.org\/rust-by-example\/compatibility\/raw_identifiers.html","title":null,"type":null},"content":[{"type":"text","text":"原始標識符語法"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"："},{"type":"codeinline","content":[{"type":"text","text":"r#async"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"但自動遷移並非十全十美：可能還是有一些情況仍然需要手動更改。該工具竭力避免更改語義，以避免影響代碼的正確性或性能。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"除了工具外，我們還維護一個版本遷移指南，其中包括版本中包含的變更。該指南將描述這些變化，併爲人們提供指導，使他們能夠了解更多。同時也會包括任何需要人們注意的邊角案例或細節。該指南既可以作爲版本的概述，也可以在人們遇到自動化工具的問題時，作爲快速故障診斷的參考。"}]},{"type":"heading","attrs":{"align":null,"level":2},"content":[{"type":"text","text":"Rust 2021 版計劃有哪些變化？"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"Rust2021 工作組在過去幾個月裏已經就新版本應該包含的內容研究了很多建議。我們很高興地公佈最終的版本變更清單。每個特性都必須滿足兩個標準才能進入這個列表。首先，它們必須得到相應的 Rust 團隊的批准。其次，它們的實施必須足夠深入，讓我們確信，它們會在計劃的里程碑之前按時完成。"}]},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"對 prelude 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作爲解決方案。和現在一樣，只增加了三項新內容："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"bulletedlist","content":[{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"std::convert::TryInto"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"std::convert::TryFrom"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"std::iter::FromIterator"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]}]}]}]},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"默認 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:("}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"這個"},{"type":"link","attrs":{"href":"https:\/\/github.com\/rust-lang\/rust\/issues\/25725","title":null,"type":null},"content":[{"type":"text","text":"問題已經存在很長時間"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"了，但是解決辦法並不像看上去那麼簡單。簡單的"},{"type":"link","attrs":{"href":"https:\/\/github.com\/rust-lang\/rust\/issues\/25725","title":null,"type":null},"content":[{"type":"text","text":"添加 trait 實現"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"將破壞已有代碼。現在，可以編譯 "},{"type":"codeinline","content":[{"type":"text","text":"array.into_iter()"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"，因爲這個函數是隱式調用 "},{"type":"codeinline","content":[{"type":"text","text":"(&array).into_iter()"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" 的，這是因爲"},{"type":"link","attrs":{"href":"https:\/\/doc.rust-lang.org\/book\/ch05-03-method-syntax.html#wheres-the---operator","title":null,"type":null},"content":[{"type":"text","text":"方法調用語法是如何工作"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"的。增加 trait 實現會改變這個含義。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"一般情況下，我們將這種破壞（增加特性的實現） 歸結爲“次要”，這是可以接受的。但是在這種情況下，太多的代碼將被破壞。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"有很多人建議“在 Rust 2021 中只對數組實現 "},{"type":"codeinline","content":[{"type":"text","text":"IntoIterator"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"”。但是，這完全不可能。你無法在一個版本中實現某個特性，而不在另一個版本中實現，因爲版本可能是混合的。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"取而代之的是，我們決定將 trait 實現 （從 Rust1.53.0 開始） 添加到所有版本中，但是增加了一個小技巧以避免 Rust 2021 之前的混亂。從 Rust 2015 和 2018 的代碼來看，編譯器仍然像以前那樣將 "},{"type":"codeinline","content":[{"type":"text","text":"array.into_iter()"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" 解析爲 "},{"type":"codeinline","content":[{"type":"text","text":"(&array).into_iter()"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"，彷彿 trait 實現並不存在。僅在 "},{"type":"codeinline","content":[{"type":"text","text":".into_iter()"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" 方法的調用語法中才有效。這不會影響其他任何語法，例如 "},{"type":"codeinline","content":[{"type":"text","text":"for e in [1, 2, 3]"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":", "},{"type":"codeinline","content":[{"type":"text","text":"iter.zip([1, 2, 3])"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" 或 "},{"type":"codeinline","content":[{"type":"text","text":"IntoIterator::into_iter([1, 2, 3])"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"。所有版本中都會有這些特性。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"儘管這需要一點小技巧才能避免破壞，這是一種可恥的做法，但是我們很高興這個解決方案能將版本間的差異降到最低。因爲這一小技巧只存在於舊版本中，所以不會在新版本中增加複雜性。"}]},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"閉包中不相交的捕獲"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"link","attrs":{"href":"https:\/\/doc.rust-lang.org\/book\/ch13-01-closures.html","title":null,"type":null},"content":[{"type":"text","text":"閉包"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"（Closure）會自動捕獲你在其主體中引用的任何內容。例如，"},{"type":"codeinline","content":[{"type":"text","text":"|| a + 1"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" 自動捕獲周圍上下文中對 "},{"type":"codeinline","content":[{"type":"text","text":"a"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" 的引用。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"現在，這對整個結構也是適用的，即使只有一個字段。例如，"},{"type":"codeinline","content":[{"type":"text","text":"|| a.x + 1"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" 捕獲到對 "},{"type":"codeinline","content":[{"type":"text","text":"a"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" 而不僅僅是 "},{"type":"codeinline","content":[{"type":"text","text":"a.x"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" 的引用。有些時候，這就是個問題。如果某個結構中的某一字段已經被借用 （可變）或移出，那麼其他字段就無法再用於閉包，因爲這樣做會捕獲已不再可用的整個結構。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"codeblock","attrs":{"lang":null},"content":[{"type":"text","text":"let a = SomeStruct::new();\n\n\ndrop(a.x); \/\/ Move out of one field of the struct\n\n\nprintln!(\"{}\", a.y); \/\/ Ok: Still use another field of the struct\n\n\nlet c = || println!(\"{}\", a.y); \/\/ Error: Tries to capture all of `a`\nc("}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"從 Rust 2021 開始，閉包將只捕獲它們使用的字段。因此，上述示例可以正常地在 Rust 2021 中編譯。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"這種新的行爲只在新版本中激活，因爲它可以更改刪除字段的順序。有一點很重要，那就是自動遷移可以用於所有版本，它會更新你的閉包。可將 "},{"type":"codeinline","content":[{"type":"text","text":"let _ = &a;"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" 插入到閉包中，這樣就必須像之前那樣捕獲整個結構。 "}]},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"Panic 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中最知名的宏之一。但是，它也有"},{"type":"link","attrs":{"href":"https:\/\/github.com\/rust-lang\/rfcs\/blob\/master\/text\/3007-panic-plan.md","title":null,"type":null},"content":[{"type":"text","text":"一些細微的意外"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"，因爲向後兼容性，我們無法隨意更改。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"codeblock","attrs":{"lang":null},"content":[{"type":"text","text":"panic!(\"{}\", 1); \/\/ Ok, panics with the message \"1\"\npanic!(\"{}\"); \/\/ Ok, panics with the message 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不會將單個參數處理爲格式字符串。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"Rust 2021 採用了一個更加一致的 "},{"type":"codeinline","content":[{"type":"text","text":"panic!()"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" 宏，以避免出現這種混亂的情況。全新 "},{"type":"codeinline","content":[{"type":"text","text":"panic!()"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" 宏將不再接受任意的表達式作爲唯一參數。它將像 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