Drop ownership from "method position".

Normally, unowned data is automatically dropped at the end of its residing block. We can also ignore unuseful return values with ;, which is essentially a T -> () transformation. However, there are cases where we wish to drop ownership and return cleanly with a (), but don't want to involve ; (such as in closures or simple match arms). We could use [std::mem::drop] for this, but drop is a function, not a method, and would visually mar a nice chain of method calls.

Hence the [Disown] trait and its method disown. It is drop, but in "method position".

use disown::Disown;
use std::collections::HashSet;

enum Person {
    Bob,
    Sam,
}

let mut set = HashSet::new();
let person = Person::Bob;

match person {
  Person::Bob => set.insert(0).disown(),
  Person::Sam => set.insert(1).disown(),
}

HashSet::insert returns a bool, not (), and the above code would not compile without opening a pair of {} and using a ;, which doesn't look as nice.

License: MIT