Function case

src/tests/truncate.rs:23–29

(mut before: T, after: T)

#[track_caller]
fn case<T: Flags + std::fmt::Debug>(mut before: T, after: T)
where
    T: std::fmt::Debug + PartialEq + Copy,
{
    before.truncate();
    assert_eq!(before, after, "{:?}.truncate()", before);
}