gistfile1.rs

fn mutate(s: &mut SomeStruct) {
    s.field += 1;
}

struct SomeStruct {
    field: i32
}

impl SomeStruct {
    fn do_something(&mut self) {
        mutate(&mut self);
    }
}

fn main() {
    let mut some_struct = SomeStruct { field: 3 };
    some_struct.do_something();
}

// [tmerr@thegibson stuff]$ rustc thing.rs
// thing.rs:12:21: 12:25 error: cannot borrow immutable local variable `self` as mutable
// thing.rs:12         mutate(&mut self);
//                                 ^~~~
//error: aborting due to previous error