Rust類型轉換 - 彆名

type語句聲明可以以現有類型被用來給一個新的名字。類型必須有 CamelCase 名稱, 或者編譯器會提出警告。例外(異常)是原始類型： usize,f32, 等.

// `NanoSecond` is a new name for `u64`.
type NanoSecond = u64;
type Inch = u64;

// Use an attribute to silence warning.
#[allow(non_camel_case_types)]
type u64_t = u64;
// TODO ^ Try removing the attribute

// Use an attribute to silence warnings
#[allow(trivial_numeric_casts)]
fn main() {
    // `NanoSecond` = `Inch` = `u64_t` = `u64`.
    let nanoseconds: NanoSecond = 5 as u64_t;
    let inches: Inch = 2 as u64_t;

    // Note that type aliases *don't* provide any extra type safety, because
    // aliases are *not* new types
    println!("{} nanoseconds + {} inches = {} unit?",
             nanoseconds,
             inches,
             nanoseconds + inches);
}

使用彆名主要是減少輸入;例如 IoResult<T> 是類型Result<T, IoError> 的彆名.

另請參見：

屬性