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Rollup merge of rust-lang#72584 - CAD97:stabilize-58957, r=dtolnay
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Stabilize vec::Drain::as_slice

and add `AsRef<[T]> for Drain<'_, T>`.

Tracking issue: rust-lang#58957. Does not stabilize `slice::IterMut::as_slice` yet. cc @cuviper
This PR proposes stabilizing just the `vec::Drain::as_slice` part of that tracking issue.

My ultimate goal here: being able to use `for<T, I: Iterator<Item=T> + AsRef<[T]>> I` to refer to `vec::IntoIter`, `vec::Drain`, and eventually `array::IntoIter`, as an approximation of the set of by-value iterators that can be "previewed" as by-ref iterators. (Actually expressing that as a trait requires GAT.)
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RalfJung authored Jun 15, 2020
2 parents b220894 + 738f848 commit d190ff5
Showing 1 changed file with 8 additions and 2 deletions.
10 changes: 8 additions & 2 deletions src/liballoc/vec.rs
Original file line number Diff line number Diff line change
Expand Up @@ -2779,19 +2779,25 @@ impl<'a, T> Drain<'a, T> {
/// # Examples
///
/// ```
/// # #![feature(vec_drain_as_slice)]
/// let mut vec = vec!['a', 'b', 'c'];
/// let mut drain = vec.drain(..);
/// assert_eq!(drain.as_slice(), &['a', 'b', 'c']);
/// let _ = drain.next().unwrap();
/// assert_eq!(drain.as_slice(), &['b', 'c']);
/// ```
#[unstable(feature = "vec_drain_as_slice", reason = "recently added", issue = "58957")]
#[stable(feature = "vec_drain_as_slice", since = "1.46.0")]
pub fn as_slice(&self) -> &[T] {
self.iter.as_slice()
}
}

#[stable(feature = "vec_drain_as_slice", since = "1.46.0")]
impl<'a, T> AsRef<[T]> for Drain<'a, T> {
fn as_ref(&self) -> &[T] {
self.as_slice()
}
}

#[stable(feature = "drain", since = "1.6.0")]
unsafe impl<T: Sync> Sync for Drain<'_, T> {}
#[stable(feature = "drain", since = "1.6.0")]
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