5 files changed, 43 insertions, 13 deletions
diff --git a/library/core/src/iter/sources/empty.rs b/library/core/src/iter/sources/empty.rs
index 98734c527..617dfd123 100644
--- a/library/core/src/iter/sources/empty.rs
+++ b/library/core/src/iter/sources/empty.rs
@@ -22,17 +22,12 @@ pub const fn empty<T>() -> Empty<T> {
     Empty(marker::PhantomData)
 }
 
-// Newtype for use in `PhantomData` to avoid
-// > error: const-stable function cannot use `#[feature(const_fn_fn_ptr_basics)]`
-// in `const fn empty<T>()` above.
-struct FnReturning<T>(fn() -> T);
-
 /// An iterator that yields nothing.
 ///
 /// This `struct` is created by the [`empty()`] function. See its documentation for more.
 #[must_use = "iterators are lazy and do nothing unless consumed"]
 #[stable(feature = "iter_empty", since = "1.2.0")]
-pub struct Empty<T>(marker::PhantomData<FnReturning<T>>);
+pub struct Empty<T>(marker::PhantomData<fn() -> T>);
 
 #[stable(feature = "core_impl_debug", since = "1.9.0")]
 impl<T> fmt::Debug for Empty<T> {
diff --git a/library/core/src/iter/sources/from_generator.rs b/library/core/src/iter/sources/from_generator.rs
index 8e7cbd34a..4cbe731b2 100644
--- a/library/core/src/iter/sources/from_generator.rs
+++ b/library/core/src/iter/sources/from_generator.rs
@@ -1,3 +1,4 @@
+use crate::fmt;
 use crate::ops::{Generator, GeneratorState};
 use crate::pin::Pin;
 
@@ -23,14 +24,21 @@ use crate::pin::Pin;
 /// ```
 #[inline]
 #[unstable(feature = "iter_from_generator", issue = "43122", reason = "generators are unstable")]
-pub fn from_generator<G: Generator<Return = ()> + Unpin>(
-    generator: G,
-) -> impl Iterator<Item = G::Yield> {
+pub fn from_generator<G: Generator<Return = ()> + Unpin>(generator: G) -> FromGenerator<G> {
     FromGenerator(generator)
 }
 
-struct FromGenerator<G>(G);
+/// An iterator over the values yielded by an underlying generator.
+///
+/// This `struct` is created by the [`iter::from_generator()`] function. See its documentation for
+/// more.
+///
+/// [`iter::from_generator()`]: from_generator
+#[unstable(feature = "iter_from_generator", issue = "43122", reason = "generators are unstable")]
+#[derive(Clone)]
+pub struct FromGenerator<G>(G);
 
+#[unstable(feature = "iter_from_generator", issue = "43122", reason = "generators are unstable")]
 impl<G: Generator<Return = ()> + Unpin> Iterator for FromGenerator<G> {
     type Item = G::Yield;
 
@@ -41,3 +49,10 @@ impl<G: Generator<Return = ()> + Unpin> Iterator for FromGenerator<G> {
         }
     }
 }
+
+#[unstable(feature = "iter_from_generator", issue = "43122", reason = "generators are unstable")]
+impl<G> fmt::Debug for FromGenerator<G> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("FromGenerator").finish()
+    }
+}
diff --git a/library/core/src/iter/sources/once_with.rs b/library/core/src/iter/sources/once_with.rs
index d79f85c25..9309a06c8 100644
--- a/library/core/src/iter/sources/once_with.rs
+++ b/library/core/src/iter/sources/once_with.rs
@@ -1,3 +1,4 @@
+use crate::fmt;
 use crate::iter::{FusedIterator, TrustedLen};
 
 /// Creates an iterator that lazily generates a value exactly once by invoking
@@ -66,12 +67,23 @@ pub fn once_with<A, F: FnOnce() -> A>(gen: F) -> OnceWith<F> {
 ///
 /// This `struct` is created by the [`once_with()`] function.
 /// See its documentation for more.
-#[derive(Clone, Debug)]
+#[derive(Clone)]
 #[stable(feature = "iter_once_with", since = "1.43.0")]
 pub struct OnceWith<F> {
     gen: Option<F>,
 }
 
+#[stable(feature = "iter_once_with_debug", since = "1.68.0")]
+impl<F> fmt::Debug for OnceWith<F> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        if self.gen.is_some() {
+            f.write_str("OnceWith(Some(_))")
+        } else {
+            f.write_str("OnceWith(None)")
+        }
+    }
+}
+
 #[stable(feature = "iter_once_with", since = "1.43.0")]
 impl<A, F: FnOnce() -> A> Iterator for OnceWith<F> {
     type Item = A;
diff --git a/library/core/src/iter/sources/repeat_n.rs b/library/core/src/iter/sources/repeat_n.rs
index fd8d25ce1..dc61d6065 100644
--- a/library/core/src/iter/sources/repeat_n.rs
+++ b/library/core/src/iter/sources/repeat_n.rs
@@ -126,7 +126,7 @@ impl<A: Clone> Iterator for RepeatN<A> {
             // zero so it won't be dropped later, and thus it's okay to take it here.
             unsafe { ManuallyDrop::take(&mut self.element) }
         } else {
-            A::clone(&mut self.element)
+            A::clone(&self.element)
         })
     }
 
diff --git a/library/core/src/iter/sources/repeat_with.rs b/library/core/src/iter/sources/repeat_with.rs
index ab2d0472b..3f34105a3 100644
--- a/library/core/src/iter/sources/repeat_with.rs
+++ b/library/core/src/iter/sources/repeat_with.rs
@@ -1,3 +1,4 @@
+use crate::fmt;
 use crate::iter::{FusedIterator, TrustedLen};
 use crate::ops::Try;
 
@@ -71,12 +72,19 @@ pub fn repeat_with<A, F: FnMut() -> A>(repeater: F) -> RepeatWith<F> {
 ///
 /// This `struct` is created by the [`repeat_with()`] function.
 /// See its documentation for more.
-#[derive(Copy, Clone, Debug)]
+#[derive(Copy, Clone)]
 #[stable(feature = "iterator_repeat_with", since = "1.28.0")]
 pub struct RepeatWith<F> {
     repeater: F,
 }
 
+#[stable(feature = "iterator_repeat_with_debug", since = "1.68.0")]
+impl<F> fmt::Debug for RepeatWith<F> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("RepeatWith").finish_non_exhaustive()
+    }
+}
+
 #[stable(feature = "iterator_repeat_with", since = "1.28.0")]
 impl<A, F: FnMut() -> A> Iterator for RepeatWith<F> {
     type Item = A;