Rust 1.45发布！

• as 关键字默认为saturating cast

fn cast(x: f32) -> u8 {
    x as u8
}

fn main() {
let too_big = 300.0;
let too_small = -100.0;
let nan = f32::NAN;

println!("too_big_casted = {}", cast(too_big));
println!("too_small_casted = {}", cast(too_small));
println!("not_a_number_casted = {}", cast(nan));
}

too_big_casted = 255
too_small_casted = 0
not_a_number_casted = 0

• 如果不想采用as的默认转换，则需要使用unsafe方法

let x: f32 = 1.0;
let y: u8 = unsafe { x.to_int_unchecked() };

// imagine we have a procedural macro named "mac"

mac!(); // item position, this was what was stable before

// but these three are new:
fn main() {
let expr = mac!(); // expression position

match expr {
      mac!() => {} // pattern position
  }

  mac!(); // statement position
}

for ch in 'a'..='z' {
print!("{}", ch);
}
// Prints "abcdefghijklmnopqrstuvwxyz"

无船同志新博客：Shipping Const Generics in 2020

// This is a custom type which is parameterized by a `usize`
pub struct Foo<const N: usize> {
    bytes: [u8; N],
}


// This is a trait which has been implemented for arrays of
// any length.
// 通过const generic, 我们可以给任意长度的数组impl某个trait
impl<T: Debug, const N: usize> Debug for [T; N] {
}

• 普通的const泛型参数。比如，在impl <const N：usize>中，该值可按字面意义用于填充const泛型。
• 不依赖其他泛型或const generic(我理解为是二阶const generic?)，并且可以在const上下文运行的表达式（有点绕）;

let data = [1, 2, 3, 4, 5, 6];

let sum1 = data.array_chunks().map(|&[x, y]| x * y).sum::<i32>();
assert_eq!(sum1, (1 * 2) + (3 * 4) + (5 * 6));

let sum2 = data.array_chunks().map(|&[x, y, z]| x * y * z).sum::<i32>();
assert_eq!(sum2, (1 * 2 * 3) + (4 * 5 * 6));

Deno项目内部架构

luminance-0.40

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