Rust 编码规范 V 1.0 beta

P.FMT.10 match 分支应该具有良好的可读性

【描述】

1. 当match分支右侧代码体太长无法和=>置于同一行需要使用块(block)来包裹。
2. 在match分支左侧匹配表达式前不要增加管道符(|)

【反例】

// 不符合： 与 `=>` 不同行应该用块来包裹
// 当 `match_arm_blocks=false`
fn main() {
    match lorem {
        ipsum => 
            foooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo(x),
        dolor => println!("{}", sit),
        sit => foo(
            "foooooooooooooooooooooooo",
            "baaaaaaaaaaaaaaaaaaaaaaaarr",
            "baaaaaaaaaaaaaaaaaaaazzzzzzzzzzzzz",
            "qqqqqqqqquuuuuuuuuuuuuuuuuuuuuuuuuuxxx",
        ),
    }
}

// 当 `match_arm_leading_pipes="Alaways"`
fn foo() {
    match foo {
        // 不符合： 分支左侧匹配表达式前不要加管道符
        | "foo" | "bar" => {}
        | "baz"
        | "something relatively long"
        | "something really really really realllllllllllllly long" => println!("x"),
        | "qux" => println!("y"),
        | _ => {}
    }
}

【正例】

// 当 `match_arm_blocks=true`
fn main() {
    match lorem {
        // 符合
        ipsum => { 
            foooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo(x)
        }
        dolor => println!("{}", sit),
        // 符合
        sit => foo(
            "foooooooooooooooooooooooo",
            "baaaaaaaaaaaaaaaaaaaaaaaarr",
            "baaaaaaaaaaaaaaaaaaaazzzzzzzzzzzzz",
            "qqqqqqqqquuuuuuuuuuuuuuuuuuuuuuuuuuxxx",
        ),
    }
}

// 当 `match_arm_leading_pipes="Never"`
fn foo() {

    match foo {
        // 符合
        "foo" | "bar" => {}
        "baz"
        | "something relatively long"
        | "something really really really realllllllllllllly long" => println!("x"),
        "qux" => println!("y"),
        _ => {}
    }
}

【rustfmt 配置】