From 78d8ce7301ef5dd562ea0e06e2b316f1a8d04bf2 Mon Sep 17 00:00:00 2001
From: Jeremy Smart <jeremy3141592@gmail.com>
Date: Sat, 6 Sep 2025 01:14:31 -0400
Subject: [PATCH] add SliceIndex wrapper types Last and Clamp<Idx>

---
 library/core/src/index.rs        | 472 +++++++++++++++++++++++++++++++
 library/core/src/lib.rs          |   1 +
 library/core/src/range.rs        |  12 +
 library/core/src/slice/index.rs  |   5 +
 library/coretests/tests/index.rs |  83 ++++++
 library/coretests/tests/lib.rs   |   4 +
 6 files changed, 577 insertions(+)
 create mode 100644 library/core/src/index.rs
 create mode 100644 library/coretests/tests/index.rs

diff --git a/library/core/src/index.rs b/library/core/src/index.rs
new file mode 100644
index 0000000000000..3baefdf10cecb
--- /dev/null
+++ b/library/core/src/index.rs
@@ -0,0 +1,472 @@
+#![unstable(feature = "sliceindex_wrappers", issue = "146179")]
+
+//! Helper types for indexing slices.
+
+use crate::intrinsics::slice_get_unchecked;
+use crate::slice::SliceIndex;
+use crate::{cmp, ops, range};
+
+/// Clamps an index, guaranteeing that it will only access valid elements of the slice.
+///
+/// # Examples
+///
+/// ```
+/// #![feature(sliceindex_wrappers)]
+///
+/// use core::index::Clamp;
+///
+/// let s: &[usize] = &[0, 1, 2, 3];
+///
+/// assert_eq!(&3, &s[Clamp(6)]);
+/// assert_eq!(&[1, 2, 3], &s[Clamp(1..6)]);
+/// assert_eq!(&[] as &[usize], &s[Clamp(5..6)]);
+/// assert_eq!(&[0, 1, 2, 3], &s[Clamp(..6)]);
+/// assert_eq!(&[0, 1, 2, 3], &s[Clamp(..=6)]);
+/// assert_eq!(&[] as &[usize], &s[Clamp(6..)]);
+/// ```
+#[unstable(feature = "sliceindex_wrappers", issue = "146179")]
+#[derive(Debug)]
+pub struct Clamp<Idx>(pub Idx);
+
+/// Always accesses the last element of the slice.
+///
+/// # Examples
+///
+/// ```
+/// #![feature(sliceindex_wrappers)]
+/// #![feature(slice_index_methods)]
+///
+/// use core::index::Last;
+/// use core::slice::SliceIndex;
+///
+/// let s = &[0, 1, 2, 3];
+///
+/// assert_eq!(&3, &s[Last]);
+/// assert_eq!(None, Last.get(&[] as &[usize]));
+///
+/// ```
+#[unstable(feature = "sliceindex_wrappers", issue = "146179")]
+#[derive(Debug)]
+pub struct Last;
+
+#[unstable(feature = "sliceindex_wrappers", issue = "146179")]
+unsafe impl<T> SliceIndex<[T]> for Clamp<usize> {
+    type Output = T;
+
+    fn get(self, slice: &[T]) -> Option<&Self::Output> {
+        slice.get(cmp::min(self.0, slice.len() - 1))
+    }
+
+    fn get_mut(self, slice: &mut [T]) -> Option<&mut Self::Output> {
+        slice.get_mut(cmp::min(self.0, slice.len() - 1))
+    }
+
+    unsafe fn get_unchecked(self, slice: *const [T]) -> *const Self::Output {
+        // SAFETY: the caller ensures that the slice isn't empty
+        unsafe { slice_get_unchecked(slice, cmp::min(self.0, slice.len() - 1)) }
+    }
+
+    unsafe fn get_unchecked_mut(self, slice: *mut [T]) -> *mut Self::Output {
+        // SAFETY: the caller ensures that the slice isn't empty
+        unsafe { slice_get_unchecked(slice, cmp::min(self.0, slice.len() - 1)) }
+    }
+
+    fn index(self, slice: &[T]) -> &Self::Output {
+        &(*slice)[cmp::min(self.0, slice.len() - 1)]
+    }
+
+    fn index_mut(self, slice: &mut [T]) -> &mut Self::Output {
+        &mut (*slice)[cmp::min(self.0, slice.len() - 1)]
+    }
+}
+
+#[unstable(feature = "sliceindex_wrappers", issue = "146179")]
+unsafe impl<T> SliceIndex<[T]> for Clamp<range::Range<usize>> {
+    type Output = [T];
+
+    fn get(self, slice: &[T]) -> Option<&Self::Output> {
+        let start = cmp::min(self.0.start, slice.len());
+        let end = cmp::min(self.0.end, slice.len());
+        (start..end).get(slice)
+    }
+
+    fn get_mut(self, slice: &mut [T]) -> Option<&mut Self::Output> {
+        let start = cmp::min(self.0.start, slice.len());
+        let end = cmp::min(self.0.end, slice.len());
+        (start..end).get_mut(slice)
+    }
+
+    unsafe fn get_unchecked(self, slice: *const [T]) -> *const Self::Output {
+        let start = cmp::min(self.0.start, slice.len());
+        let end = cmp::min(self.0.end, slice.len());
+        // SAFETY: a range ending before len is always valid
+        unsafe { (start..end).get_unchecked(slice) }
+    }
+
+    unsafe fn get_unchecked_mut(self, slice: *mut [T]) -> *mut Self::Output {
+        let start = cmp::min(self.0.start, slice.len());
+        let end = cmp::min(self.0.end, slice.len());
+        // SAFETY: a range ending before len is always valid
+        unsafe { (start..end).get_unchecked_mut(slice) }
+    }
+
+    fn index(self, slice: &[T]) -> &Self::Output {
+        let start = cmp::min(self.0.start, slice.len());
+        let end = cmp::min(self.0.end, slice.len());
+        (start..end).index(slice)
+    }
+
+    fn index_mut(self, slice: &mut [T]) -> &mut Self::Output {
+        let start = cmp::min(self.0.start, slice.len());
+        let end = cmp::min(self.0.end, slice.len());
+        (start..end).index_mut(slice)
+    }
+}
+
+#[unstable(feature = "sliceindex_wrappers", issue = "146179")]
+unsafe impl<T> SliceIndex<[T]> for Clamp<ops::Range<usize>> {
+    type Output = [T];
+
+    fn get(self, slice: &[T]) -> Option<&Self::Output> {
+        let start = cmp::min(self.0.start, slice.len());
+        let end = cmp::min(self.0.end, slice.len());
+        (start..end).get(slice)
+    }
+
+    fn get_mut(self, slice: &mut [T]) -> Option<&mut Self::Output> {
+        let start = cmp::min(self.0.start, slice.len());
+        let end = cmp::min(self.0.end, slice.len());
+        (start..end).get_mut(slice)
+    }
+
+    unsafe fn get_unchecked(self, slice: *const [T]) -> *const Self::Output {
+        let start = cmp::min(self.0.start, slice.len());
+        let end = cmp::min(self.0.end, slice.len());
+        // SAFETY: a range ending before len is always valid
+        unsafe { (start..end).get_unchecked(slice) }
+    }
+
+    unsafe fn get_unchecked_mut(self, slice: *mut [T]) -> *mut Self::Output {
+        let start = cmp::min(self.0.start, slice.len());
+        let end = cmp::min(self.0.end, slice.len());
+        // SAFETY: a range ending before len is always valid
+        unsafe { (start..end).get_unchecked_mut(slice) }
+    }
+
+    fn index(self, slice: &[T]) -> &Self::Output {
+        let start = cmp::min(self.0.start, slice.len());
+        let end = cmp::min(self.0.end, slice.len());
+        (start..end).index(slice)
+    }
+
+    fn index_mut(self, slice: &mut [T]) -> &mut Self::Output {
+        let start = cmp::min(self.0.start, slice.len());
+        let end = cmp::min(self.0.end, slice.len());
+        (start..end).index_mut(slice)
+    }
+}
+
+#[unstable(feature = "sliceindex_wrappers", issue = "146179")]
+unsafe impl<T> SliceIndex<[T]> for Clamp<range::RangeInclusive<usize>> {
+    type Output = [T];
+
+    fn get(self, slice: &[T]) -> Option<&Self::Output> {
+        let start = cmp::min(self.0.start, slice.len() - 1);
+        let end = cmp::min(self.0.last, slice.len() - 1);
+        (start..=end).get(slice)
+    }
+
+    fn get_mut(self, slice: &mut [T]) -> Option<&mut Self::Output> {
+        let start = cmp::min(self.0.start, slice.len() - 1);
+        let end = cmp::min(self.0.last, slice.len() - 1);
+        (start..=end).get_mut(slice)
+    }
+
+    unsafe fn get_unchecked(self, slice: *const [T]) -> *const Self::Output {
+        let start = cmp::min(self.0.start, slice.len() - 1);
+        let end = cmp::min(self.0.last, slice.len() - 1);
+        // SAFETY: the caller ensures that the slice isn't empty
+        unsafe { (start..=end).get_unchecked(slice) }
+    }
+
+    unsafe fn get_unchecked_mut(self, slice: *mut [T]) -> *mut Self::Output {
+        let start = cmp::min(self.0.start, slice.len() - 1);
+        let end = cmp::min(self.0.last, slice.len() - 1);
+        // SAFETY: the caller ensures that the slice isn't empty
+        unsafe { (start..=end).get_unchecked_mut(slice) }
+    }
+
+    fn index(self, slice: &[T]) -> &Self::Output {
+        let start = cmp::min(self.0.start, slice.len() - 1);
+        let end = cmp::min(self.0.last, slice.len() - 1);
+        (start..=end).index(slice)
+    }
+
+    fn index_mut(self, slice: &mut [T]) -> &mut Self::Output {
+        let start = cmp::min(self.0.start, slice.len() - 1);
+        let end = cmp::min(self.0.last, slice.len() - 1);
+        (start..=end).index_mut(slice)
+    }
+}
+
+#[unstable(feature = "sliceindex_wrappers", issue = "146179")]
+unsafe impl<T> SliceIndex<[T]> for Clamp<ops::RangeInclusive<usize>> {
+    type Output = [T];
+
+    fn get(self, slice: &[T]) -> Option<&Self::Output> {
+        let start = cmp::min(self.0.start, slice.len() - 1);
+        let end = cmp::min(self.0.end, slice.len() - 1);
+        (start..=end).get(slice)
+    }
+
+    fn get_mut(self, slice: &mut [T]) -> Option<&mut Self::Output> {
+        let start = cmp::min(self.0.start, slice.len() - 1);
+        let end = cmp::min(self.0.end, slice.len() - 1);
+        (start..=end).get_mut(slice)
+    }
+
+    unsafe fn get_unchecked(self, slice: *const [T]) -> *const Self::Output {
+        let start = cmp::min(self.0.start, slice.len() - 1);
+        let end = cmp::min(self.0.end, slice.len() - 1);
+        // SAFETY: the caller ensures that the slice isn't empty
+        unsafe { (start..=end).get_unchecked(slice) }
+    }
+
+    unsafe fn get_unchecked_mut(self, slice: *mut [T]) -> *mut Self::Output {
+        let start = cmp::min(self.0.start, slice.len() - 1);
+        let end = cmp::min(self.0.end, slice.len() - 1);
+        // SAFETY: the caller ensures that the slice isn't empty
+        unsafe { (start..=end).get_unchecked_mut(slice) }
+    }
+
+    fn index(self, slice: &[T]) -> &Self::Output {
+        let start = cmp::min(self.0.start, slice.len() - 1);
+        let end = cmp::min(self.0.end, slice.len() - 1);
+        (start..=end).index(slice)
+    }
+
+    fn index_mut(self, slice: &mut [T]) -> &mut Self::Output {
+        let start = cmp::min(self.0.start, slice.len() - 1);
+        let end = cmp::min(self.0.end, slice.len() - 1);
+        (start..=end).index_mut(slice)
+    }
+}
+
+#[unstable(feature = "sliceindex_wrappers", issue = "146179")]
+unsafe impl<T> SliceIndex<[T]> for Clamp<range::RangeFrom<usize>> {
+    type Output = [T];
+
+    fn get(self, slice: &[T]) -> Option<&Self::Output> {
+        (cmp::min(self.0.start, slice.len())..).get(slice)
+    }
+
+    fn get_mut(self, slice: &mut [T]) -> Option<&mut Self::Output> {
+        (cmp::min(self.0.start, slice.len())..).get_mut(slice)
+    }
+
+    unsafe fn get_unchecked(self, slice: *const [T]) -> *const Self::Output {
+        // SAFETY: a range starting at len is valid
+        unsafe { (cmp::min(self.0.start, slice.len())..).get_unchecked(slice) }
+    }
+
+    unsafe fn get_unchecked_mut(self, slice: *mut [T]) -> *mut Self::Output {
+        // SAFETY: a range starting at len is valid
+        unsafe { (cmp::min(self.0.start, slice.len())..).get_unchecked_mut(slice) }
+    }
+
+    fn index(self, slice: &[T]) -> &Self::Output {
+        (cmp::min(self.0.start, slice.len())..).index(slice)
+    }
+
+    fn index_mut(self, slice: &mut [T]) -> &mut Self::Output {
+        (cmp::min(self.0.start, slice.len())..).index_mut(slice)
+    }
+}
+
+#[unstable(feature = "sliceindex_wrappers", issue = "146179")]
+unsafe impl<T> SliceIndex<[T]> for Clamp<ops::RangeFrom<usize>> {
+    type Output = [T];
+
+    fn get(self, slice: &[T]) -> Option<&Self::Output> {
+        (cmp::min(self.0.start, slice.len())..).get(slice)
+    }
+
+    fn get_mut(self, slice: &mut [T]) -> Option<&mut Self::Output> {
+        (cmp::min(self.0.start, slice.len())..).get_mut(slice)
+    }
+
+    unsafe fn get_unchecked(self, slice: *const [T]) -> *const Self::Output {
+        // SAFETY: a range starting at len is valid
+        unsafe { (cmp::min(self.0.start, slice.len())..).get_unchecked(slice) }
+    }
+
+    unsafe fn get_unchecked_mut(self, slice: *mut [T]) -> *mut Self::Output {
+        // SAFETY: a range starting at len is valid
+        unsafe { (cmp::min(self.0.start, slice.len())..).get_unchecked_mut(slice) }
+    }
+
+    fn index(self, slice: &[T]) -> &Self::Output {
+        (cmp::min(self.0.start, slice.len())..).index(slice)
+    }
+
+    fn index_mut(self, slice: &mut [T]) -> &mut Self::Output {
+        (cmp::min(self.0.start, slice.len())..).index_mut(slice)
+    }
+}
+
+#[unstable(feature = "sliceindex_wrappers", issue = "146179")]
+unsafe impl<T> SliceIndex<[T]> for Clamp<range::RangeTo<usize>> {
+    type Output = [T];
+
+    fn get(self, slice: &[T]) -> Option<&Self::Output> {
+        (..cmp::min(self.0.end, slice.len())).get(slice)
+    }
+
+    fn get_mut(self, slice: &mut [T]) -> Option<&mut Self::Output> {
+        (..cmp::min(self.0.end, slice.len())).get_mut(slice)
+    }
+
+    unsafe fn get_unchecked(self, slice: *const [T]) -> *const Self::Output {
+        // SAFETY: a range ending before len is always valid
+        unsafe { (..cmp::min(self.0.end, slice.len())).get_unchecked(slice) }
+    }
+
+    unsafe fn get_unchecked_mut(self, slice: *mut [T]) -> *mut Self::Output {
+        // SAFETY: a range ending before len is always valid
+        unsafe { (..cmp::min(self.0.end, slice.len())).get_unchecked_mut(slice) }
+    }
+
+    fn index(self, slice: &[T]) -> &Self::Output {
+        (..cmp::min(self.0.end, slice.len())).index(slice)
+    }
+
+    fn index_mut(self, slice: &mut [T]) -> &mut Self::Output {
+        (..cmp::min(self.0.end, slice.len())).index_mut(slice)
+    }
+}
+
+#[unstable(feature = "sliceindex_wrappers", issue = "146179")]
+unsafe impl<T> SliceIndex<[T]> for Clamp<range::RangeToInclusive<usize>> {
+    type Output = [T];
+
+    fn get(self, slice: &[T]) -> Option<&Self::Output> {
+        (..=cmp::min(self.0.last, slice.len() - 1)).get(slice)
+    }
+
+    fn get_mut(self, slice: &mut [T]) -> Option<&mut Self::Output> {
+        (..=cmp::min(self.0.last, slice.len() - 1)).get_mut(slice)
+    }
+
+    unsafe fn get_unchecked(self, slice: *const [T]) -> *const Self::Output {
+        // SAFETY: the caller ensures that the slice isn't empty
+        unsafe { (..=cmp::min(self.0.last, slice.len() - 1)).get_unchecked(slice) }
+    }
+
+    unsafe fn get_unchecked_mut(self, slice: *mut [T]) -> *mut Self::Output {
+        // SAFETY: the caller ensures that the slice isn't empty
+        unsafe { (..=cmp::min(self.0.last, slice.len() - 1)).get_unchecked_mut(slice) }
+    }
+
+    fn index(self, slice: &[T]) -> &Self::Output {
+        (..=cmp::min(self.0.last, slice.len() - 1)).index(slice)
+    }
+
+    fn index_mut(self, slice: &mut [T]) -> &mut Self::Output {
+        (..=cmp::min(self.0.last, slice.len() - 1)).index_mut(slice)
+    }
+}
+
+#[unstable(feature = "sliceindex_wrappers", issue = "146179")]
+unsafe impl<T> SliceIndex<[T]> for Clamp<ops::RangeToInclusive<usize>> {
+    type Output = [T];
+
+    fn get(self, slice: &[T]) -> Option<&Self::Output> {
+        (..=cmp::min(self.0.end, slice.len() - 1)).get(slice)
+    }
+
+    fn get_mut(self, slice: &mut [T]) -> Option<&mut Self::Output> {
+        (..=cmp::min(self.0.end, slice.len() - 1)).get_mut(slice)
+    }
+
+    unsafe fn get_unchecked(self, slice: *const [T]) -> *const Self::Output {
+        // SAFETY: the caller ensures that the slice isn't empty
+        unsafe { (..=cmp::min(self.0.end, slice.len() - 1)).get_unchecked(slice) }
+    }
+
+    unsafe fn get_unchecked_mut(self, slice: *mut [T]) -> *mut Self::Output {
+        // SAFETY: the caller ensures that the slice isn't empty
+        unsafe { (..=cmp::min(self.0.end, slice.len() - 1)).get_unchecked_mut(slice) }
+    }
+
+    fn index(self, slice: &[T]) -> &Self::Output {
+        (..=cmp::min(self.0.end, slice.len() - 1)).index(slice)
+    }
+
+    fn index_mut(self, slice: &mut [T]) -> &mut Self::Output {
+        (..=cmp::min(self.0.end, slice.len() - 1)).index_mut(slice)
+    }
+}
+
+#[unstable(feature = "sliceindex_wrappers", issue = "146179")]
+unsafe impl<T> SliceIndex<[T]> for Clamp<range::RangeFull> {
+    type Output = [T];
+
+    fn get(self, slice: &[T]) -> Option<&Self::Output> {
+        (..).get(slice)
+    }
+
+    fn get_mut(self, slice: &mut [T]) -> Option<&mut Self::Output> {
+        (..).get_mut(slice)
+    }
+
+    unsafe fn get_unchecked(self, slice: *const [T]) -> *const Self::Output {
+        // SAFETY: RangeFull just returns `slice` here
+        unsafe { (..).get_unchecked(slice) }
+    }
+
+    unsafe fn get_unchecked_mut(self, slice: *mut [T]) -> *mut Self::Output {
+        // SAFETY: RangeFull just returns `slice` here
+        unsafe { (..).get_unchecked_mut(slice) }
+    }
+
+    fn index(self, slice: &[T]) -> &Self::Output {
+        (..).index(slice)
+    }
+
+    fn index_mut(self, slice: &mut [T]) -> &mut Self::Output {
+        (..).index_mut(slice)
+    }
+}
+
+#[unstable(feature = "sliceindex_wrappers", issue = "146179")]
+unsafe impl<T> SliceIndex<[T]> for Last {
+    type Output = T;
+
+    fn get(self, slice: &[T]) -> Option<&Self::Output> {
+        slice.last()
+    }
+
+    fn get_mut(self, slice: &mut [T]) -> Option<&mut Self::Output> {
+        slice.last_mut()
+    }
+
+    unsafe fn get_unchecked(self, slice: *const [T]) -> *const Self::Output {
+        // SAFETY: the caller ensures that the slice isn't empty
+        unsafe { slice_get_unchecked(slice, slice.len() - 1) }
+    }
+
+    unsafe fn get_unchecked_mut(self, slice: *mut [T]) -> *mut Self::Output {
+        // SAFETY: the caller ensures that the slice isn't empty
+        unsafe { slice_get_unchecked(slice, slice.len() - 1) }
+    }
+
+    fn index(self, slice: &[T]) -> &Self::Output {
+        // N.B., use intrinsic indexing
+        &(*slice)[slice.len() - 1]
+    }
+
+    fn index_mut(self, slice: &mut [T]) -> &mut Self::Output {
+        // N.B., use intrinsic indexing
+        &mut (*slice)[slice.len() - 1]
+    }
+}
diff --git a/library/core/src/lib.rs b/library/core/src/lib.rs
index 86a68e18b0af4..db059b86a8c84 100644
--- a/library/core/src/lib.rs
+++ b/library/core/src/lib.rs
@@ -292,6 +292,7 @@ pub mod cmp;
 pub mod convert;
 pub mod default;
 pub mod error;
+pub mod index;
 pub mod marker;
 pub mod ops;
 
diff --git a/library/core/src/range.rs b/library/core/src/range.rs
index a096a8ceafc87..ee8252c177652 100644
--- a/library/core/src/range.rs
+++ b/library/core/src/range.rs
@@ -629,6 +629,18 @@ impl<Idx: PartialOrd<Idx>> RangeToInclusive<Idx> {
     }
 }
 
+impl<T> From<legacy::RangeToInclusive<T>> for RangeToInclusive<T> {
+    fn from(value: legacy::RangeToInclusive<T>) -> Self {
+        Self { last: value.end }
+    }
+}
+
+impl<T> From<RangeToInclusive<T>> for legacy::RangeToInclusive<T> {
+    fn from(value: RangeToInclusive<T>) -> Self {
+        Self { end: value.last }
+    }
+}
+
 // RangeToInclusive<Idx> cannot impl From<RangeTo<Idx>>
 // because underflow would be possible with (..0).into()
 
diff --git a/library/core/src/slice/index.rs b/library/core/src/slice/index.rs
index a8147d745f3ab..40baff3f4465e 100644
--- a/library/core/src/slice/index.rs
+++ b/library/core/src/slice/index.rs
@@ -134,6 +134,11 @@ mod private_slice_index {
     impl Sealed for range::RangeFrom<usize> {}
 
     impl Sealed for ops::IndexRange {}
+
+    #[unstable(feature = "sliceindex_wrappers", issue = "146179")]
+    impl Sealed for crate::index::Last {}
+    #[unstable(feature = "sliceindex_wrappers", issue = "146179")]
+    impl<T> Sealed for crate::index::Clamp<T> where T: Sealed {}
 }
 
 /// A helper trait used for indexing operations.
diff --git a/library/coretests/tests/index.rs b/library/coretests/tests/index.rs
new file mode 100644
index 0000000000000..68e4c841e3226
--- /dev/null
+++ b/library/coretests/tests/index.rs
@@ -0,0 +1,83 @@
+use core::index::Clamp;
+use core::range;
+use core::slice::SliceIndex;
+
+macro_rules! test_clamp {
+    ($range:expr, $(($slice:expr, $other:expr)),+) => {
+        $(
+            assert_eq!(Clamp($range.clone()).get(&$slice as &[_]), $other.get(&$slice as &[_]));
+            assert_eq!(Clamp($range.clone()).get_mut(&mut $slice as &mut [_]), $other.get_mut(&mut $slice as &mut [_]));
+            unsafe {
+                assert_eq!(&*Clamp($range.clone()).get_unchecked(&$slice as &[_]), &*$other.get_unchecked(&$slice as &[_]));
+                assert_eq!(&*Clamp($range.clone()).get_unchecked_mut(&mut $slice as &mut [_]), &*$other.get_unchecked_mut(&mut $slice as &mut [_]));
+            }
+            assert_eq!(Clamp($range.clone()).index(&$slice as &[_]), $other.index(&$slice as &[_]));
+            assert_eq!(Clamp($range.clone()).index_mut(&mut $slice as &mut [_]), $other.index_mut(&mut $slice as &mut [_]));
+        )+
+    };
+}
+
+#[test]
+fn test_clamp_usize() {
+    test_clamp!(2, ([0, 1], 1), ([0, 1, 2], 2));
+}
+
+#[test]
+fn test_clamp_range_range() {
+    test_clamp!(range::Range::from(1..4), ([0, 1], 1..2), ([0, 1, 2, 3, 4], 1..4), ([0], 1..1));
+}
+
+#[test]
+fn test_clamp_ops_range() {
+    test_clamp!(1..4, ([0, 1], 1..2), ([0, 1, 2, 3, 4], 1..4), ([0], 1..1));
+}
+
+#[test]
+fn test_clamp_range_range_inclusive() {
+    test_clamp!(
+        range::RangeInclusive::from(1..=3),
+        ([0, 1], 1..=1),
+        ([0, 1, 2, 3, 4], 1..=3),
+        ([0], 0..=0)
+    );
+}
+
+#[test]
+fn test_clamp_ops_range_inclusive() {
+    test_clamp!(1..=3, ([0, 1], 1..=1), ([0, 1, 2, 3, 4], 1..=3), ([0], 0..=0));
+}
+
+#[test]
+fn test_clamp_range_range_from() {
+    test_clamp!(range::RangeFrom::from(1..), ([0, 1], 1..), ([0, 1, 2, 3, 4], 1..), ([0], 1..));
+}
+
+#[test]
+fn test_clamp_ops_range_from() {
+    test_clamp!(1.., ([0, 1], 1..), ([0, 1, 2, 3, 4], 1..), ([0], 1..));
+}
+
+#[test]
+fn test_clamp_range_to() {
+    test_clamp!(..4, ([0, 1], ..2), ([0, 1, 2, 3, 4], ..4), ([0], ..1));
+}
+
+#[test]
+fn test_clamp_range_range_to_inclusive() {
+    test_clamp!(
+        range::RangeToInclusive::from(..=4),
+        ([0, 1], ..=1),
+        ([0, 1, 2, 3, 4], ..=4),
+        ([0], ..=0)
+    );
+}
+
+#[test]
+fn test_clamp_ops_range_to_inclusive() {
+    test_clamp!(..=4, ([0, 1], ..=1), ([0, 1, 2, 3, 4], ..=4), ([0], ..=0));
+}
+
+#[test]
+fn test_clamp_range_full() {
+    test_clamp!(.., ([0, 1], ..), ([0, 1, 2, 3, 4], ..), ([0], ..));
+}
diff --git a/library/coretests/tests/lib.rs b/library/coretests/tests/lib.rs
index 5c519f3a499d2..4d0a7780fe8de 100644
--- a/library/coretests/tests/lib.rs
+++ b/library/coretests/tests/lib.rs
@@ -81,6 +81,7 @@
 #![feature(maybe_uninit_write_slice)]
 #![feature(min_specialization)]
 #![feature(never_type)]
+#![feature(new_range_api)]
 #![feature(next_index)]
 #![feature(non_exhaustive_omitted_patterns_lint)]
 #![feature(numfmt)]
@@ -93,9 +94,11 @@
 #![feature(ptr_metadata)]
 #![feature(result_option_map_or_default)]
 #![feature(slice_from_ptr_range)]
+#![feature(slice_index_methods)]
 #![feature(slice_internals)]
 #![feature(slice_partition_dedup)]
 #![feature(slice_split_once)]
+#![feature(sliceindex_wrappers)]
 #![feature(split_array)]
 #![feature(split_as_slice)]
 #![feature(std_internals)]
@@ -173,6 +176,7 @@ mod fmt;
 mod future;
 mod hash;
 mod hint;
+mod index;
 mod intrinsics;
 mod io;
 mod iter;