Borrowing with Functions

As part of borrow checking, the compiler needs to reason about how borrows flow into and out of functions. In the simplest case borrows last for the duration of the function call:

fn borrows(x: &i32) {
    dbg!(x);
}

fn main() {
    let mut val = 123;

    // Borrow `val` for the function call.
    borrows(&val);

    // Borrow has ended and we're free to mutate.
    val += 5;
}