Is immutability by default worth the hassle?

7

And keep the mut-or-not bindings? I admit I've never spent a lot of time considering that alternative universe. Does it go like so?

  • &mut coeres to &uniq or &
  • &uniq coerces to &
  • &uniq has the same move semantics and aliasing guarantees as &mut
  • You can create a &uniq from a non-mut variable
  • You can get a &'short mut out of a &'short uniq &'long mut

And then you could write

impl Env<'_> {
    fn helper(&uniq Self) {
    // ...
    *env.errors += 1;
}

fn foo(/* not mut */ env: Env<'_>) {
    env.helper();
}

But helper couldn't replace all of env or get a &mut to any field?

Interesting to think about. I guess it is a more-immutable-reference than &.