"错误:预期的项目,发现'让'"

Question

我有一个代码转储,我在其中放置了防锈代码示例,以防我忘记了什么.我一直在error: expected item, found 'let'寻找41+线.可能是我的代码结构不正确吗？我只是将我学到的代码片段粘贴到main.rs中.我认为枚举有某种特殊的格式或地方.

我试着更改名称,认为这是名称惯例; 但这没有帮助.同样的错误.

这是转储(实际上并不大)

#[allow(dead_code)]


fn main()
{

}





/////////////////////////////////////////tutorial functoins i made

fn if_statements()
{
    //let (x, y) = (5, 10);
    let x = 5;
    let y = if x == 5 { 10 } else { 15 };
        if y == 15 {println!("y = {}", y);}
}



////////////////////////////////////////// tutoiral functions
#[allow(dead_code)]
fn add(a: i32, b: i32) -> i32
{
    a + b

}

#[allow(dead_code)]
fn crash(exception: &str) -> !
{
    panic!("{}", exception);
}


//TUPLES//
let y = (1, "hello");
let x: (i32, &str) = (1, "hello");

//STRUCTS//
struct Point {
    x: i32,
    y: i32,
}

fn structs() {
    let origin = Point { x: 0, y: 0 }; // origin: Point

    println!("The origin is at ({}, {})", origin.x, origin.y);
}

//ENUMS//
enum Character {
    Digit(i32),
    Other,
}

let ten  = Character::Digit(10);
let four = Character::Digit(4);

Answer 1

您的根本问题是let只能在函数中使用.因此,包装代码main(),并修复样式:

fn if_statements() {
    let x = 5;

    let y = if x == 5 { 10 } else { 15 };

    if y == 15 {
        println!("y = {}", y);
    }
}

#[allow(dead_code)]
fn add(a: i32, b: i32) -> i32 { a + b }

#[allow(dead_code)]
fn crash(exception: &str) -> ! {
    panic!("{}", exception);
 }

struct Point {
     x: i32,
     y: i32,
}

fn structs() {
    let origin = Point { x: 0, y: 0 };

    println!("The origin is at ({}, {})", origin.x, origin.y);
}

enum Character {
    Digit(i32),
    Other,
}

fn main() {
    let y = (1, "hello");
    let x: (i32, &str) = (1, "hello");

    let ten  = Character::Digit(10);
    let four = Character::Digit(4);
 }