2 files changed, 45 insertions, 0 deletions
diff --git a/library/core/src/slice/iter.rs b/library/core/src/slice/iter.rs
index 76b4a534e5d..f1e65930967 100644
--- a/library/core/src/slice/iter.rs
+++ b/library/core/src/slice/iter.rs
@@ -1788,6 +1788,12 @@ unsafe impl<'a, T> TrustedRandomAccessNoCoerce for ChunksMut<'a, T> {
     const MAY_HAVE_SIDE_EFFECT: bool = false;
 }
 
+#[stable(feature = "rust1", since = "1.0.0")]
+unsafe impl<T> Send for ChunksMut<'_, T> where T: Send {}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+unsafe impl<T> Sync for ChunksMut<'_, T> where T: Sync {}
+
 /// An iterator over a slice in (non-overlapping) chunks (`chunk_size` elements at a
 /// time), starting at the beginning of the slice.
 ///
@@ -2114,6 +2120,12 @@ unsafe impl<'a, T> TrustedRandomAccessNoCoerce for ChunksExactMut<'a, T> {
     const MAY_HAVE_SIDE_EFFECT: bool = false;
 }
 
+#[stable(feature = "chunks_exact", since = "1.31.0")]
+unsafe impl<T> Send for ChunksExactMut<'_, T> where T: Send {}
+
+#[stable(feature = "chunks_exact", since = "1.31.0")]
+unsafe impl<T> Sync for ChunksExactMut<'_, T> where T: Sync {}
+
 /// A windowed iterator over a slice in overlapping chunks (`N` elements at a
 /// time), starting at the beginning of the slice
 ///
@@ -2835,6 +2847,12 @@ unsafe impl<'a, T> TrustedRandomAccessNoCoerce for RChunksMut<'a, T> {
     const MAY_HAVE_SIDE_EFFECT: bool = false;
 }
 
+#[stable(feature = "rchunks", since = "1.31.0")]
+unsafe impl<T> Send for RChunksMut<'_, T> where T: Send {}
+
+#[stable(feature = "rchunks", since = "1.31.0")]
+unsafe impl<T> Sync for RChunksMut<'_, T> where T: Sync {}
+
 /// An iterator over a slice in (non-overlapping) chunks (`chunk_size` elements at a
 /// time), starting at the end of the slice.
 ///
@@ -3168,6 +3186,12 @@ unsafe impl<'a, T> TrustedRandomAccessNoCoerce for RChunksExactMut<'a, T> {
     const MAY_HAVE_SIDE_EFFECT: bool = false;
 }
 
+#[stable(feature = "rchunks", since = "1.31.0")]
+unsafe impl<T> Send for RChunksExactMut<'_, T> where T: Send {}
+
+#[stable(feature = "rchunks", since = "1.31.0")]
+unsafe impl<T> Sync for RChunksExactMut<'_, T> where T: Sync {}
+
 #[doc(hidden)]
 #[unstable(feature = "trusted_random_access", issue = "none")]
 unsafe impl<'a, T> TrustedRandomAccess for Iter<'a, T> {}
diff --git a/library/core/tests/slice.rs b/library/core/tests/slice.rs
index 6d1516958f3..0656109e9db 100644
--- a/library/core/tests/slice.rs
+++ b/library/core/tests/slice.rs
@@ -1192,6 +1192,27 @@ fn test_rchunks_exact_mut_zip() {
 }
 
 #[test]
+fn chunks_mut_are_send_and_sync() {
+    use std::cell::Cell;
+    use std::slice::{ChunksExactMut, ChunksMut, RChunksExactMut, RChunksMut};
+    use std::sync::MutexGuard;
+
+    #[allow(unused)]
+    fn assert_send_and_sync()
+    where
+        ChunksMut<'static, Cell<i32>>: Send,
+        ChunksMut<'static, MutexGuard<'static, u32>>: Sync,
+        ChunksExactMut<'static, Cell<i32>>: Send,
+        ChunksExactMut<'static, MutexGuard<'static, u32>>: Sync,
+        RChunksMut<'static, Cell<i32>>: Send,
+        RChunksMut<'static, MutexGuard<'static, u32>>: Sync,
+        RChunksExactMut<'static, Cell<i32>>: Send,
+        RChunksExactMut<'static, MutexGuard<'static, u32>>: Sync,
+    {
+    }
+}
+
+#[test]
 fn test_windows_count() {
     let v: &[i32] = &[0, 1, 2, 3, 4, 5];
     let c = v.windows(3);