[breaking-change] due to the removal of Copy which shouldn't have been there in the first place, as per policy set forth in #27186.
/// assert_eq!(arr[1...2], [ 1,2 ]); // RangeInclusive
/// }
/// ```
-#[derive(Copy, Clone, PartialEq, Eq)]
+#[derive(Clone, PartialEq, Eq, Hash)] // not Copy -- see #27186
#[unstable(feature = "inclusive_range", reason = "recently added, follows RFC", issue = "28237")]
pub enum RangeInclusive<Idx> {
/// Empty range (iteration has finished)