Chaining APIs for both self -> Self and &mut self methods.

let mut thing = Thing { x: 6 };
thing.set_mut(ModifyX(8));
assert_eq!(thing.x, 8);

let thing = thing.set(ModifyX(9));
assert_eq!(thing.x, 9);

Rust-modifier allows you to define modifiers just once, then use them through both set and set_mut, allowing downstream users the ability to use whichever API is most convenient.

Additionally, rust-modifier allows users to define their own modifiers, arbitrarily extending the utility of existing types.

MIT