50 Common Mistakes Rust Beginners Make: See How Many Have You Been Made?

1. Incorrect use of variable and immutable borrowing

let mut data = vec![1, 2, 3];
let x = &data[0];
data.push(4);
println!("{}", x);

Data cannot be modified when there are immutable references.

1. Forgot Processing Options

fn main() {
    let some_number = Some(5);
    let sum = some_number + 5; // 错误：Option 类型不能这样直接使用
}

Use match or if let to handle options.

let sum = if let Some(n) = some_number { n + 5 } else { 0 };

1. Expected reference instead of actual value

fn foo(x: &i32) {
    // ...
}fn main() {
    let x = 10;
    foo(x); // 错误：应传递引用而不是值
}

Pass a reference instead of a value.

foo(&x);

1. Mismatched type

fn main() {
    let flag = true;
    let number = if flag { 5 } else { "six" }; // 错误：不匹配的类型
}

Solution: Ensure that all branches return the same type.

let number = if flag { 5 } else { 6 };

1. Forgot to import traits

use std::io::Write; // 因为 Write trait 已导入fn main() {
    let mut buffer = Vec::new();
    buffer.write_all(b"hello").unwrap();
    // 现在可以正常使用 write_all 方法，因为 Write trait 已导入
}

You must import the Write trait to use its methods.

1. Trying to modify it…