A question regarding good practice and impl'ing trait methods that return a mutable reference to self.

RustQuestion4.rs

// Is it considered bad practise to do something like this?
// Or is it fine? Common even?
//
// I'm specifically referring to impl'ing a trait method for a
// struct that returns a mutable reference to itself? In my
// current situation, it seems it will save a lot of unnecessary
// impl'ing when deriving from trait "A".

#[deriving(Show)]
pub struct MyStruct<'a> { i: int }

pub trait A<'a> {
    fn get_mystruct(&'a mut self) -> &'a mut MyStruct;
    // Heaps of other fn's referring to 'get_mystruct'...
}

impl<'a> A<'a> for MyStruct<'a> {
    fn get_mystruct(&'a mut self) -> &'a mut MyStruct { self }
}

fn main() {
    let mut ms = MyStruct { i: 25 };
    println!("{}", ms);
    println!("{}", ms.get_mystruct());
}