4 files changed, 28 insertions, 9 deletions
diff --git a/library/core/src/iter/range.rs b/library/core/src/iter/range.rs
index dba2b2291ff..f19636fba5d 100644
--- a/library/core/src/iter/range.rs
+++ b/library/core/src/iter/range.rs
@@ -1,4 +1,5 @@
 use crate::convert::TryFrom;
+use crate::marker::Destruct;
 use crate::mem;
 use crate::ops::{self, Try};
 
@@ -522,6 +523,7 @@ macro_rules! range_incl_exact_iter_impl {
 }
 
 /// Specialization implementations for `Range`.
+#[const_trait]
 trait RangeIteratorImpl {
     type Item;
 
@@ -536,7 +538,7 @@ trait RangeIteratorImpl {
     fn spec_advance_back_by(&mut self, n: usize) -> Result<(), usize>;
 }
 
-impl<A: Step> RangeIteratorImpl for ops::Range<A> {
+impl<A: ~const Step + ~const Destruct> const RangeIteratorImpl for ops::Range<A> {
     type Item = A;
 
     #[inline]
@@ -622,7 +624,7 @@ impl<A: Step> RangeIteratorImpl for ops::Range<A> {
     }
 }
 
-impl<T: TrustedStep> RangeIteratorImpl for ops::Range<T> {
+impl<T: ~const TrustedStep + ~const Destruct> const RangeIteratorImpl for ops::Range<T> {
     #[inline]
     fn spec_next(&mut self) -> Option<T> {
         if self.start < self.end {
@@ -710,7 +712,8 @@ impl<T: TrustedStep> RangeIteratorImpl for ops::Range<T> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<A: Step> Iterator for ops::Range<A> {
+#[rustc_const_unstable(feature = "const_iter", issue = "92476")]
+impl<A: ~const Step + ~const Destruct> const Iterator for ops::Range<A> {
     type Item = A;
 
     #[inline]
@@ -820,7 +823,8 @@ range_incl_exact_iter_impl! {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<A: Step> DoubleEndedIterator for ops::Range<A> {
+#[rustc_const_unstable(feature = "const_iter", issue = "92476")]
+impl<A: ~const Step + ~const Destruct> const DoubleEndedIterator for ops::Range<A> {
     #[inline]
     fn next_back(&mut self) -> Option<A> {
         self.spec_next_back()
diff --git a/library/core/src/iter/traits/double_ended.rs b/library/core/src/iter/traits/double_ended.rs
index ed23873cdde..7a10dea500a 100644
--- a/library/core/src/iter/traits/double_ended.rs
+++ b/library/core/src/iter/traits/double_ended.rs
@@ -1,3 +1,4 @@
+use crate::marker::Destruct;
 use crate::ops::{ControlFlow, Try};
 
 /// An iterator able to yield elements from both ends.
@@ -37,6 +38,7 @@ use crate::ops::{ControlFlow, Try};
 /// ```
 #[stable(feature = "rust1", since = "1.0.0")]
 #[cfg_attr(not(test), rustc_diagnostic_item = "DoubleEndedIterator")]
+#[const_trait]
 pub trait DoubleEndedIterator: Iterator {
     /// Removes and returns an element from the end of the iterator.
     ///
@@ -131,7 +133,10 @@ pub trait DoubleEndedIterator: Iterator {
     /// [`Err(k)`]: Err
     #[inline]
     #[unstable(feature = "iter_advance_by", reason = "recently added", issue = "77404")]
-    fn advance_back_by(&mut self, n: usize) -> Result<(), usize> {
+    fn advance_back_by(&mut self, n: usize) -> Result<(), usize>
+    where
+        Self::Item: ~const Destruct,
+    {
         for i in 0..n {
             self.next_back().ok_or(i)?;
         }
@@ -181,6 +186,7 @@ pub trait DoubleEndedIterator: Iterator {
     /// ```
     #[inline]
     #[stable(feature = "iter_nth_back", since = "1.37.0")]
+    #[rustc_do_not_const_check]
     fn nth_back(&mut self, n: usize) -> Option<Self::Item> {
         self.advance_back_by(n).ok()?;
         self.next_back()
@@ -218,6 +224,7 @@ pub trait DoubleEndedIterator: Iterator {
     /// ```
     #[inline]
     #[stable(feature = "iterator_try_fold", since = "1.27.0")]
+    #[rustc_do_not_const_check]
     fn try_rfold<B, F, R>(&mut self, init: B, mut f: F) -> R
     where
         Self: Sized,
@@ -289,6 +296,7 @@ pub trait DoubleEndedIterator: Iterator {
     #[doc(alias = "foldr")]
     #[inline]
     #[stable(feature = "iter_rfold", since = "1.27.0")]
+    #[rustc_do_not_const_check]
     fn rfold<B, F>(mut self, init: B, mut f: F) -> B
     where
         Self: Sized,
@@ -344,6 +352,7 @@ pub trait DoubleEndedIterator: Iterator {
     /// ```
     #[inline]
     #[stable(feature = "iter_rfind", since = "1.27.0")]
+    #[rustc_do_not_const_check]
     fn rfind<P>(&mut self, predicate: P) -> Option<Self::Item>
     where
         Self: Sized,
diff --git a/library/core/src/iter/traits/iterator.rs b/library/core/src/iter/traits/iterator.rs
index d48760ab3eb..6fc86550b63 100644
--- a/library/core/src/iter/traits/iterator.rs
+++ b/library/core/src/iter/traits/iterator.rs
@@ -1,5 +1,6 @@
 use crate::array;
 use crate::cmp::{self, Ordering};
+use crate::marker::Destruct;
 use crate::ops::{ChangeOutputType, ControlFlow, FromResidual, Residual, Try};
 
 use super::super::try_process;
@@ -336,8 +337,10 @@ pub trait Iterator {
     /// ```
     #[inline]
     #[unstable(feature = "iter_advance_by", reason = "recently added", issue = "77404")]
-    #[rustc_do_not_const_check]
-    fn advance_by(&mut self, n: usize) -> Result<(), usize> {
+    fn advance_by(&mut self, n: usize) -> Result<(), usize>
+    where
+        Self::Item: ~const Destruct,
+    {
         for i in 0..n {
             self.next().ok_or(i)?;
         }
@@ -385,8 +388,10 @@ pub trait Iterator {
     /// ```
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
-    #[rustc_do_not_const_check]
-    fn nth(&mut self, n: usize) -> Option<Self::Item> {
+    fn nth(&mut self, n: usize) -> Option<Self::Item>
+    where
+        Self::Item: ~const Destruct,
+    {
         self.advance_by(n).ok()?;
         self.next()
     }
diff --git a/library/core/src/lib.rs b/library/core/src/lib.rs
index a8b4b23dc12..1076d357070 100644
--- a/library/core/src/lib.rs
+++ b/library/core/src/lib.rs
@@ -123,6 +123,7 @@
 #![feature(const_index_range_slice_index)]
 #![feature(const_inherent_unchecked_arith)]
 #![feature(const_int_unchecked_arith)]
+#![feature(const_intoiterator_identity)]
 #![feature(const_intrinsic_forget)]
 #![feature(const_ipv4)]
 #![feature(const_ipv6)]