Function tao_of_rust::ch03::type_infer::infer_demo

pub fn infer_demo()

类型推导

Base usage: 正常推导

fn sum(a: u32, b: i32) -> u32 {
    a + (b as u32)
}
fn infer_demo() {
    let a = 1;
    let b = 2;
    assert_eq!(sum(a, b), 3); // a和b的类型会自动推断为i32
    let elem = 5u8;
    let mut vec = Vec::new();
    vec.push(elem); // vec 类型会自动推断为 u8
    assert_eq!(vec, [5]);
}
infer_demo();

Base usage: 无法推导的情况

let x = "1";
println!("{:?}", x.parse().unwrap());

Base usage: 解决无法推导的情况

let x = "1";
println!("{:?}", x.parse::<i32>().unwrap());

Base usage: 另一种类型无法推导的情况

let a = 0;
let a_pos = a.is_positive(); // error`[E0599]`: no method named `is_positive` found for type `{integer}` in the current scope