fn main() {
let x = 5u32;

let y = {
let x_squared = x * x;
let x_cube = x_squared * x;

// 将此表达式赋给 `y`
x_cube + x_squared + x
};

let z = {
// 分号结束了这个表达式，于是将 `()` 赋给 `z`
2 * x;
};

println!("x is {:?}", x);
println!("y is {:?}", y);
println!("z is {:?}", z);
}