Add Debug implementations for libcollection structs

10 files changed, 496 insertions, 0 deletions

diff --git a/src/libcollections/binary_heap.rs b/src/libcollections/binary_heap.rs
index b7c2a708baf..fca3b7b07dd 100644
--- a/src/libcollections/binary_heap.rs
+++ b/src/libcollections/binary_heap.rs
@@ -228,6 +228,20 @@ pub struct PeekMut<'a, T: 'a + Ord> {
     sift: bool,
 }
 
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<'a, T: Ord> fmt::Debug for PeekMut<'a, T> {
+    default fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.pad("PeekMut { .. }")
+    }
+}
+
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<'a, T: Ord + fmt::Debug> fmt::Debug for PeekMut<'a, T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.pad(&format!("PeekMut({:?})", self.heap.data[0]))
+    }
+}
+
 #[stable(feature = "binary_heap_peek_mut", since = "1.12.0")]
 impl<'a, T: Ord> Drop for PeekMut<'a, T> {
     fn drop(&mut self) {
@@ -968,6 +982,22 @@ pub struct Iter<'a, T: 'a> {
     iter: slice::Iter<'a, T>,
 }
 
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<'a, T: 'a> fmt::Debug for Iter<'a, T> {
+    default fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.pad("BinaryHeap::Iter { .. }")
+    }
+}
+
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<'a, T: 'a + fmt::Debug> fmt::Debug for Iter<'a, T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_tuple("BinaryHeap::Iter")
+         .field(&self.iter.as_slice())
+         .finish()
+    }
+}
+
 // FIXME(#19839) Remove in favor of `#[derive(Clone)]`
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<'a, T> Clone for Iter<'a, T> {
@@ -1016,6 +1046,22 @@ pub struct IntoIter<T> {
     iter: vec::IntoIter<T>,
 }
 
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<T> fmt::Debug for IntoIter<T> {
+    default fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.pad("BinaryHeap::IntoIter { .. }")
+    }
+}
+
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<T: fmt::Debug> fmt::Debug for IntoIter<T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_tuple("BinaryHeap::IntoIter")
+         .field(&self.iter.as_slice())
+         .finish()
+    }
+}
+
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T> Iterator for IntoIter<T> {
     type Item = T;
@@ -1055,6 +1101,20 @@ pub struct Drain<'a, T: 'a> {
     iter: vec::Drain<'a, T>,
 }
 
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<'a, T: 'a> fmt::Debug for Drain<'a, T> {
+    default fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.pad("BinaryHeap::Drain { .. }")
+    }
+}
+
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<'a, T: 'a + fmt::Debug> fmt::Debug for Drain<'a, T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.pad(&format!("BinaryHeap::Drain({:?})", self.iter))
+    }
+}
+
 #[stable(feature = "drain", since = "1.6.0")]
 impl<'a, T: 'a> Iterator for Drain<'a, T> {
     type Item = T;
diff --git a/src/libcollections/btree/map.rs b/src/libcollections/btree/map.rs
index 4755f8a4c55..0d8b9d4677b 100644
--- a/src/libcollections/btree/map.rs
+++ b/src/libcollections/btree/map.rs
@@ -270,6 +270,20 @@ pub struct Iter<'a, K: 'a, V: 'a> {
     length: usize,
 }
 
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<'a, K: 'a, V: 'a> fmt::Debug for Iter<'a, K, V> {
+    default fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.pad("BTreeMap::Iter { .. }")
+    }
+}
+
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<'a, K: 'a + fmt::Debug, V: 'a + fmt::Debug> fmt::Debug for Iter<'a, K, V> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_list().entries(self.clone()).finish()
+    }
+}
+
 /// A mutable iterator over a BTreeMap's entries.
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct IterMut<'a, K: 'a, V: 'a> {
@@ -277,6 +291,20 @@ pub struct IterMut<'a, K: 'a, V: 'a> {
     length: usize,
 }
 
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<'a, K: 'a, V: 'a> fmt::Debug for IterMut<'a, K, V> {
+    default fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.pad("BTreeMap::IterMut { .. }")
+    }
+}
+
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<'a, K: 'a + fmt::Debug, V: 'a + fmt::Debug> fmt::Debug for IterMut<'a, K, V> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.pad(&format!("BTreeMap::IterMut({:?})", self.range))
+    }
+}
+
 /// An owning iterator over a BTreeMap's entries.
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct IntoIter<K, V> {
@@ -285,30 +313,104 @@ pub struct IntoIter<K, V> {
     length: usize,
 }
 
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<K, V> fmt::Debug for IntoIter<K, V> {
+    default fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.pad("BTreeMap::IntoIter { .. }")
+    }
+}
+
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<K: fmt::Debug, V: fmt::Debug> fmt::Debug for IntoIter<K, V> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        let range = Range {
+            front: self.front.reborrow(),
+            back: self.back.reborrow(),
+        };
+        f.debug_list().entries(range).finish()
+    }
+}
+
 /// An iterator over a BTreeMap's keys.
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct Keys<'a, K: 'a, V: 'a> {
     inner: Iter<'a, K, V>,
 }
 
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<'a, K: 'a, V: 'a> fmt::Debug for Keys<'a, K, V> {
+    default fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.pad("BTreeMap::Keys { .. }")
+    }
+}
+
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<'a, K: 'a + fmt::Debug, V: 'a + fmt::Debug> fmt::Debug for Keys<'a, K, V> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_list().entries(self.inner.clone()).finish()
+    }
+}
+
 /// An iterator over a BTreeMap's values.
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct Values<'a, K: 'a, V: 'a> {
     inner: Iter<'a, K, V>,
 }
 
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<'a, K: 'a, V: 'a> fmt::Debug for Values<'a, K, V> {
+    default fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.pad("BTreeMap::Values { .. }")
+    }
+}
+
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<'a, K: 'a + fmt::Debug, V: 'a + fmt::Debug> fmt::Debug for Values<'a, K, V> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_list().entries(self.inner.clone()).finish()
+    }
+}
+
 /// A mutable iterator over a BTreeMap's values.
 #[stable(feature = "map_values_mut", since = "1.10.0")]
 pub struct ValuesMut<'a, K: 'a, V: 'a> {
     inner: IterMut<'a, K, V>,
 }
 
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<'a, K: 'a, V: 'a> fmt::Debug for ValuesMut<'a, K, V> {
+    default fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.pad("BTreeMap::ValuesMut { .. }")
+    }
+}
+
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<'a, K: 'a + fmt::Debug, V: 'a + fmt::Debug> fmt::Debug for ValuesMut<'a, K, V> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.pad(&format!("BTreeMap::ValuesMut({:?})", self.inner))
+    }
+}
+
 /// An iterator over a sub-range of BTreeMap's entries.
 pub struct Range<'a, K: 'a, V: 'a> {
     front: Handle<NodeRef<marker::Immut<'a>, K, V, marker::Leaf>, marker::Edge>,
     back: Handle<NodeRef<marker::Immut<'a>, K, V, marker::Leaf>, marker::Edge>,
 }
 
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<'a, K: 'a, V: 'a> fmt::Debug for Range<'a, K, V> {
+    default fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.pad("BTreeMap::Range { .. }")
+    }
+}
+
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<'a, K: 'a + fmt::Debug, V: 'a + fmt::Debug> fmt::Debug for Range<'a, K, V> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_list().entries(self.clone()).finish()
+    }
+}
+
 /// A mutable iterator over a sub-range of BTreeMap's entries.
 pub struct RangeMut<'a, K: 'a, V: 'a> {
     front: Handle<NodeRef<marker::Mut<'a>, K, V, marker::Leaf>, marker::Edge>,
@@ -318,6 +420,24 @@ pub struct RangeMut<'a, K: 'a, V: 'a> {
     _marker: PhantomData<&'a mut (K, V)>,
 }
 
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<'a, K: 'a, V: 'a> fmt::Debug for RangeMut<'a, K, V> {
+    default fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.pad("BTreeMap::RangeMut { .. }")
+    }
+}
+
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<'a, K: 'a + fmt::Debug, V: 'a + fmt::Debug> fmt::Debug for RangeMut<'a, K, V> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        let range = Range {
+            front: self.front.reborrow(),
+            back: self.back.reborrow(),
+        };
+        f.debug_list().entries(range).finish()
+    }
+}
+
 /// A view into a single entry in a map, which may either be vacant or occupied.
 /// This enum is constructed from the [`entry`] method on [`BTreeMap`].
 ///
diff --git a/src/libcollections/btree/set.rs b/src/libcollections/btree/set.rs
index f006ba95371..d9effde7204 100644
--- a/src/libcollections/btree/set.rs
+++ b/src/libcollections/btree/set.rs
@@ -85,6 +85,22 @@ pub struct Iter<'a, T: 'a> {
     iter: Keys<'a, T, ()>,
 }
 
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<'a, T: 'a> fmt::Debug for Iter<'a, T> {
+    default fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.pad("BTreeSet::Iter { .. }")
+    }
+}
+
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<'a, T: 'a + fmt::Debug> fmt::Debug for Iter<'a, T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_tuple("BTreeSet::Iter")
+         .field(&self.iter.clone())
+         .finish()
+    }
+}
+
 /// An owning iterator over a `BTreeSet`'s items.
 ///
 /// This structure is created by the `into_iter` method on [`BTreeSet`]
@@ -96,6 +112,20 @@ pub struct IntoIter<T> {
     iter: ::btree_map::IntoIter<T, ()>,
 }
 
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<T> fmt::Debug for IntoIter<T> {
+    default fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.pad("BTreeSet::IntoIter { .. }")
+    }
+}
+
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<T: fmt::Debug> fmt::Debug for IntoIter<T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.pad(&format!("BTreeSet::IntoIter({:?})", self.iter))
+    }
+}
+
 /// An iterator over a sub-range of `BTreeSet`'s items.
 ///
 /// This structure is created by the [`range`] method on [`BTreeSet`].
@@ -106,6 +136,20 @@ pub struct Range<'a, T: 'a> {
     iter: ::btree_map::Range<'a, T, ()>,
 }
 
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<'a, T: 'a> fmt::Debug for Range<'a, T> {
+    default fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.pad("BTreeSet::Range { .. }")
+    }
+}
+
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<'a, T: 'a + fmt::Debug> fmt::Debug for Range<'a, T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.pad(&format!("BTreeSet::Range({:?})", self.iter))
+    }
+}
+
 /// A lazy iterator producing elements in the set difference (in-order).
 ///
 /// This structure is created by the [`difference`] method on [`BTreeSet`].
@@ -118,6 +162,22 @@ pub struct Difference<'a, T: 'a> {
     b: Peekable<Iter<'a, T>>,
 }
 
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<'a, T: 'a> fmt::Debug for Difference<'a, T> {
+    default fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.pad("BTreeSet::Difference { .. }")
+    }
+}
+
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<'a, T: 'a + fmt::Debug> fmt::Debug for Difference<'a, T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_tuple("BTreeSet::Difference")
+         .field(&self.clone())
+         .finish()
+    }
+}
+
 /// A lazy iterator producing elements in the set symmetric difference (in-order).
 ///
 /// This structure is created by the [`symmetric_difference`] method on
@@ -131,6 +191,22 @@ pub struct SymmetricDifference<'a, T: 'a> {
     b: Peekable<Iter<'a, T>>,
 }
 
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<'a, T: 'a> fmt::Debug for SymmetricDifference<'a, T> {
+    default fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.pad("BTreeSet::SymmetricDifference { .. }")
+    }
+}
+
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<'a, T: 'a + fmt::Debug> fmt::Debug for SymmetricDifference<'a, T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_tuple("BTreeSet::SymmetricDifference")
+         .field(&self.clone())
+         .finish()
+    }
+}
+
 /// A lazy iterator producing elements in the set intersection (in-order).
 ///
 /// This structure is created by the [`intersection`] method on [`BTreeSet`].
@@ -143,6 +219,22 @@ pub struct Intersection<'a, T: 'a> {
     b: Peekable<Iter<'a, T>>,
 }
 
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<'a, T: 'a> fmt::Debug for Intersection<'a, T> {
+    default fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.pad("BTreeSet::Intersection { .. }")
+    }
+}
+
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<'a, T: 'a + fmt::Debug> fmt::Debug for Intersection<'a, T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_tuple("BTreeSet::Intersection")
+         .field(&self.clone())
+         .finish()
+    }
+}
+
 /// A lazy iterator producing elements in the set union (in-order).
 ///
 /// This structure is created by the [`union`] method on [`BTreeSet`].
@@ -155,6 +247,22 @@ pub struct Union<'a, T: 'a> {
     b: Peekable<Iter<'a, T>>,
 }
 
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<'a, T: 'a> fmt::Debug for Union<'a, T> {
+    default fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.pad("BTreeSet::Union { .. }")
+    }
+}
+
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<'a, T: 'a + fmt::Debug> fmt::Debug for Union<'a, T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_tuple("BTreeSet::Union")
+         .field(&self.clone())
+         .finish()
+    }
+}
+
 impl<T: Ord> BTreeSet<T> {
     /// Makes a new `BTreeSet` with a reasonable choice of B.
     ///
diff --git a/src/libcollections/enum_set.rs b/src/libcollections/enum_set.rs
index 87bc5e59ef7..3e739fa4f95 100644
--- a/src/libcollections/enum_set.rs
+++ b/src/libcollections/enum_set.rs
@@ -220,6 +220,22 @@ pub struct Iter<E> {
     marker: marker::PhantomData<E>,
 }
 
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<E> fmt::Debug for Iter<E> {
+    default fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.pad("EnumSet::Iter { .. }")
+    }
+}
+
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<E: fmt::Debug> fmt::Debug for Iter<E> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_tuple("EnumSet::Iter")
+         .field(&self.clone())
+         .finish()
+    }
+}
+
 // FIXME(#19839) Remove in favor of `#[derive(Clone)]`
 impl<E> Clone for Iter<E> {
     fn clone(&self) -> Iter<E> {
diff --git a/src/libcollections/lib.rs b/src/libcollections/lib.rs
index 561d8860dc8..92d0d4d3c54 100644
--- a/src/libcollections/lib.rs
+++ b/src/libcollections/lib.rs
@@ -28,6 +28,7 @@
 
 #![cfg_attr(test, allow(deprecated))] // rand
 #![deny(warnings)]
+#![deny(missing_debug_implementations)]
 
 #![feature(alloc)]
 #![feature(allow_internal_unstable)]
diff --git a/src/libcollections/linked_list.rs b/src/libcollections/linked_list.rs
index 7f913d4afe4..112749d5b05 100644
--- a/src/libcollections/linked_list.rs
+++ b/src/libcollections/linked_list.rs
@@ -65,6 +65,22 @@ pub struct Iter<'a, T: 'a> {
     marker: PhantomData<&'a Node<T>>,
 }
 
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<'a, T: 'a> fmt::Debug for Iter<'a, T> {
+    default fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.pad("LinkedList::Iter { .. }")
+    }
+}
+
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<'a, T: 'a + fmt::Debug> fmt::Debug for Iter<'a, T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_tuple("LinkedList::Iter")
+         .field(&self.clone())
+         .finish()
+    }
+}
+
 // FIXME #19839: deriving is too aggressive on the bounds (T doesn't need to be Clone).
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<'a, T> Clone for Iter<'a, T> {
@@ -82,6 +98,22 @@ pub struct IterMut<'a, T: 'a> {
     len: usize,
 }
 
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<'a, T: 'a> fmt::Debug for IterMut<'a, T> {
+    default fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.pad("LinkedList::IterMut { .. }")
+    }
+}
+
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<'a, T: 'a + fmt::Debug> fmt::Debug for IterMut<'a, T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_tuple("LinkedList::IterMut")
+         .field(self.clone())
+         .finish()
+    }
+}
+
 /// An iterator over the elements of a `LinkedList`.
 #[derive(Clone)]
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -89,6 +121,22 @@ pub struct IntoIter<T> {
     list: LinkedList<T>,
 }
 
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<T> fmt::Debug for IntoIter<T> {
+    default fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.pad("LinkedList::IntoIter { .. }")
+    }
+}
+
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<T: fmt::Debug> fmt::Debug for IntoIter<T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_tuple("LinkedList::IntoIter")
+         .field(self.clone())
+         .finish()
+    }
+}
+
 impl<T> Node<T> {
     fn new(element: T) -> Self {
         Node {
@@ -1077,6 +1125,22 @@ pub struct FrontPlace<'a, T: 'a> {
     node: IntermediateBox<Node<T>>,
 }
 
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<'a, T: 'a> fmt::Debug for FrontPlace<'a, T> {
+    default fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.pad("LinkedList::FrontPlace { .. }")
+    }
+}
+
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<'a, T: 'a + fmt::Debug> fmt::Debug for FrontPlace<'a, T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_tuple("LinkedList::FrontPlace")
+         .field(self.clone())
+         .finish()
+    }
+}
+
 #[unstable(feature = "collection_placement",
            reason = "placement protocol is subject to change",
            issue = "30172")]
@@ -1121,6 +1185,22 @@ pub struct BackPlace<'a, T: 'a> {
     node: IntermediateBox<Node<T>>,
 }
 
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<'a, T: 'a> fmt::Debug for BackPlace<'a, T> {
+    default fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.pad("LinkedList::BackPlace { .. }")
+    }
+}
+
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<'a, T: 'a + fmt::Debug> fmt::Debug for BackPlace<'a, T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_tuple("LinkedList::BackPlace")
+         .field(self.clone())
+         .finish()
+    }
+}
+
 #[unstable(feature = "collection_placement",
            reason = "placement protocol is subject to change",
            issue = "30172")]
diff --git a/src/libcollections/str.rs b/src/libcollections/str.rs
index 70cedce9a90..8dbddbb41d7 100644
--- a/src/libcollections/str.rs
+++ b/src/libcollections/str.rs
@@ -19,6 +19,7 @@
 // It's cleaner to just turn off the unused_imports warning than to fix them.
 #![allow(unused_imports)]
 
+use core::fmt;
 use core::str as core_str;
 use core::str::pattern::Pattern;
 use core::str::pattern::{Searcher, ReverseSearcher, DoubleEndedSearcher};
@@ -122,6 +123,13 @@ pub struct EncodeUtf16<'a> {
     encoder: Utf16Encoder<Chars<'a>>,
 }
 
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<'a> fmt::Debug for EncodeUtf16<'a> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.pad("EncodeUtf16 { .. }")
+    }
+}
+
 #[stable(feature = "encode_utf16", since = "1.8.0")]
 impl<'a> Iterator for EncodeUtf16<'a> {
     type Item = u16;
diff --git a/src/libcollections/string.rs b/src/libcollections/string.rs
index 5210c25b4e5..1a9849f2352 100644
--- a/src/libcollections/string.rs
+++ b/src/libcollections/string.rs
@@ -1979,6 +1979,13 @@ pub struct Drain<'a> {
     iter: Chars<'a>,
 }
 
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<'a> fmt::Debug for Drain<'a> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.pad("String::Drain { .. }")
+    }
+}
+
 #[stable(feature = "drain", since = "1.6.0")]
 unsafe impl<'a> Sync for Drain<'a> {}
 #[stable(feature = "drain", since = "1.6.0")]
diff --git a/src/libcollections/vec.rs b/src/libcollections/vec.rs
index 4b05f8062e8..4f6212a1709 100644
--- a/src/libcollections/vec.rs
+++ b/src/libcollections/vec.rs
@@ -2092,6 +2092,22 @@ pub struct Drain<'a, T: 'a> {
     vec: Shared<Vec<T>>,
 }
 
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<'a, T: 'a> fmt::Debug for Drain<'a, T> {
+    default fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.pad("Vec::Drain { .. }")
+    }
+}
+
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<'a, T: 'a + fmt::Debug> fmt::Debug for Drain<'a, T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_tuple("Vec::Drain")
+         .field(&self.iter.as_slice())
+         .finish()
+    }
+}
+
 #[stable(feature = "drain", since = "1.6.0")]
 unsafe impl<'a, T: Sync> Sync for Drain<'a, T> {}
 #[stable(feature = "drain", since = "1.6.0")]
@@ -2162,6 +2178,22 @@ pub struct PlaceBack<'a, T: 'a> {
     vec: &'a mut Vec<T>,
 }
 
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<'a, T: 'a> fmt::Debug for PlaceBack<'a, T> {
+    default fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.pad("Vec::PlaceBack { .. }")
+    }
+}
+
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<'a, T: 'a + fmt::Debug> fmt::Debug for PlaceBack<'a, T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_tuple("Vec::PlaceBack")
+         .field(&self.vec.as_slice())
+         .finish()
+    }
+}
+
 #[unstable(feature = "collection_placement",
            reason = "placement protocol is subject to change",
            issue = "30172")]
diff --git a/src/libcollections/vec_deque.rs b/src/libcollections/vec_deque.rs
index fea2d111f47..dfbfb240f46 100644
--- a/src/libcollections/vec_deque.rs
+++ b/src/libcollections/vec_deque.rs
@@ -1866,6 +1866,22 @@ pub struct Iter<'a, T: 'a> {
     head: usize,
 }
 
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<'a, T: 'a> fmt::Debug for Iter<'a, T> {
+    default fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.pad("VecDeque::Iter { .. }")
+    }
+}
+
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<'a, T: 'a + fmt::Debug> fmt::Debug for Iter<'a, T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_tuple("VecDeque::Iter")
+         .field(&self.clone())
+         .finish()
+    }
+}
+
 // FIXME(#19839) Remove in favor of `#[derive(Clone)]`
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<'a, T> Clone for Iter<'a, T> {
@@ -1938,6 +1954,22 @@ pub struct IterMut<'a, T: 'a> {
     head: usize,
 }
 
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<'a, T: 'a> fmt::Debug for IterMut<'a, T> {
+    default fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.pad("VecDeque::IterMut { .. }")
+    }
+}
+
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<'a, T: 'a + fmt::Debug> fmt::Debug for IterMut<'a, T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_tuple("VecDeque::IterMut")
+         .field(&self.clone())
+         .finish()
+    }
+}
+
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<'a, T> Iterator for IterMut<'a, T> {
     type Item = &'a mut T;
@@ -2004,6 +2036,22 @@ pub struct IntoIter<T> {
     inner: VecDeque<T>,
 }
 
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<T> fmt::Debug for IntoIter<T> {
+    default fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.pad("VecDeque::IntoIter { .. }")
+    }
+}
+
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<T: fmt::Debug> fmt::Debug for IntoIter<T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_tuple("VecDeque::IntoIter")
+         .field(&self.clone())
+         .finish()
+    }
+}
+
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T> Iterator for IntoIter<T> {
     type Item = T;
@@ -2047,6 +2095,22 @@ pub struct Drain<'a, T: 'a> {
     deque: Shared<VecDeque<T>>,
 }
 
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<'a, T: 'a> fmt::Debug for Drain<'a, T> {
+    default fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.pad("VecDeque::Drain { .. }")
+    }
+}
+
+#[stable(feature = "collection_debug", since = "1.15.0")]
+impl<'a, T: 'a + fmt::Debug> fmt::Debug for Drain<'a, T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_tuple("VecDeque::Drain")
+         .field(&self.clone())
+         .finish()
+    }
+}
+
 #[stable(feature = "drain", since = "1.6.0")]
 unsafe impl<'a, T: Sync> Sync for Drain<'a, T> {}
 #[stable(feature = "drain", since = "1.6.0")]