diff --git a/src/libcollections/binary_heap.rs b/src/libcollections/binary_heap.rs
index f748c8ad1eb..da461ae2d4d 100644
--- a/src/libcollections/binary_heap.rs
+++ b/src/libcollections/binary_heap.rs
@@ -573,7 +573,9 @@ impl<'a, T> Clone for Iter<'a, T> {
 }
 
 #[stable]
-impl<'a, T> Iterator<&'a T> for Iter<'a, T> {
+impl<'a, T> Iterator for Iter<'a, T> {
+    type Item = &'a T;
+
     #[inline]
     fn next(&mut self) -> Option<&'a T> { self.iter.next() }
 
@@ -582,13 +584,13 @@ impl<'a, T> Iterator<&'a T> for Iter<'a, T> {
 }
 
 #[stable]
-impl<'a, T> DoubleEndedIterator<&'a T> for Iter<'a, T> {
+impl<'a, T> DoubleEndedIterator for Iter<'a, T> {
     #[inline]
     fn next_back(&mut self) -> Option<&'a T> { self.iter.next_back() }
 }
 
 #[stable]
-impl<'a, T> ExactSizeIterator<&'a T> for Iter<'a, T> {}
+impl<'a, T> ExactSizeIterator for Iter<'a, T> {}
 
 /// An iterator that moves out of a `BinaryHeap`.
 pub struct IntoIter<T> {
@@ -596,7 +598,9 @@ pub struct IntoIter<T> {
 }
 
 #[stable]
-impl<T> Iterator<T> for IntoIter<T> {
+impl<T> Iterator for IntoIter<T> {
+    type Item = T;
+
     #[inline]
     fn next(&mut self) -> Option<T> { self.iter.next() }
 
@@ -605,13 +609,13 @@ impl<T> Iterator<T> for IntoIter<T> {
 }
 
 #[stable]
-impl<T> DoubleEndedIterator<T> for IntoIter<T> {
+impl<T> DoubleEndedIterator for IntoIter<T> {
     #[inline]
     fn next_back(&mut self) -> Option<T> { self.iter.next_back() }
 }
 
 #[stable]
-impl<T> ExactSizeIterator<T> for IntoIter<T> {}
+impl<T> ExactSizeIterator for IntoIter<T> {}
 
 /// An iterator that drains a `BinaryHeap`.
 pub struct Drain<'a, T: 'a> {
@@ -619,7 +623,9 @@ pub struct Drain<'a, T: 'a> {
 }
 
 #[stable]
-impl<'a, T: 'a> Iterator<T> for Drain<'a, T> {
+impl<'a, T: 'a> Iterator for Drain<'a, T> {
+    type Item = T;
+
     #[inline]
     fn next(&mut self) -> Option<T> { self.iter.next() }
 
@@ -628,24 +634,24 @@ impl<'a, T: 'a> Iterator<T> for Drain<'a, T> {
 }
 
 #[stable]
-impl<'a, T: 'a> DoubleEndedIterator<T> for Drain<'a, T> {
+impl<'a, T: 'a> DoubleEndedIterator for Drain<'a, T> {
     #[inline]
     fn next_back(&mut self) -> Option<T> { self.iter.next_back() }
 }
 
 #[stable]
-impl<'a, T: 'a> ExactSizeIterator<T> for Drain<'a, T> {}
+impl<'a, T: 'a> ExactSizeIterator for Drain<'a, T> {}
 
 #[stable]
 impl<T: Ord> FromIterator<T> for BinaryHeap<T> {
-    fn from_iter<Iter: Iterator<T>>(iter: Iter) -> BinaryHeap<T> {
+    fn from_iter<Iter: Iterator<Item=T>>(iter: Iter) -> BinaryHeap<T> {
         BinaryHeap::from_vec(iter.collect())
     }
 }
 
 #[stable]
 impl<T: Ord> Extend<T> for BinaryHeap<T> {
-    fn extend<Iter: Iterator<T>>(&mut self, mut iter: Iter) {
+    fn extend<Iter: Iterator<Item=T>>(&mut self, mut iter: Iter) {
         let (lower, _) = iter.size_hint();
 
         self.reserve(lower);
diff --git a/src/libcollections/bit.rs b/src/libcollections/bit.rs
index a5b8c5f3e57..5c52223bccd 100644
--- a/src/libcollections/bit.rs
+++ b/src/libcollections/bit.rs
@@ -938,7 +938,7 @@ impl Default for Bitv {
 
 #[stable]
 impl FromIterator<bool> for Bitv {
-    fn from_iter<I:Iterator<bool>>(iterator: I) -> Bitv {
+    fn from_iter<I:Iterator<Item=bool>>(iterator: I) -> Bitv {
         let mut ret = Bitv::new();
         ret.extend(iterator);
         ret
@@ -948,7 +948,7 @@ impl FromIterator<bool> for Bitv {
 #[stable]
 impl Extend<bool> for Bitv {
     #[inline]
-    fn extend<I: Iterator<bool>>(&mut self, mut iterator: I) {
+    fn extend<I: Iterator<Item=bool>>(&mut self, mut iterator: I) {
         let (min, _) = iterator.size_hint();
         self.reserve(min);
         for element in iterator {
@@ -1031,7 +1031,9 @@ pub struct Iter<'a> {
 }
 
 #[stable]
-impl<'a> Iterator<bool> for Iter<'a> {
+impl<'a> Iterator for Iter<'a> {
+    type Item = bool;
+
     #[inline]
     fn next(&mut self) -> Option<bool> {
         if self.next_idx != self.end_idx {
@@ -1050,7 +1052,7 @@ impl<'a> Iterator<bool> for Iter<'a> {
 }
 
 #[stable]
-impl<'a> DoubleEndedIterator<bool> for Iter<'a> {
+impl<'a> DoubleEndedIterator for Iter<'a> {
     #[inline]
     fn next_back(&mut self) -> Option<bool> {
         if self.next_idx != self.end_idx {
@@ -1063,10 +1065,10 @@ impl<'a> DoubleEndedIterator<bool> for Iter<'a> {
 }
 
 #[stable]
-impl<'a> ExactSizeIterator<bool> for Iter<'a> {}
+impl<'a> ExactSizeIterator for Iter<'a> {}
 
 #[stable]
-impl<'a> RandomAccessIterator<bool> for Iter<'a> {
+impl<'a> RandomAccessIterator for Iter<'a> {
     #[inline]
     fn indexable(&self) -> uint {
         self.end_idx - self.next_idx
@@ -1134,7 +1136,7 @@ impl Default for BitvSet {
 
 #[stable]
 impl FromIterator<uint> for BitvSet {
-    fn from_iter<I:Iterator<uint>>(iterator: I) -> BitvSet {
+    fn from_iter<I:Iterator<Item=uint>>(iterator: I) -> BitvSet {
         let mut ret = BitvSet::new();
         ret.extend(iterator);
         ret
@@ -1144,7 +1146,7 @@ impl FromIterator<uint> for BitvSet {
 #[stable]
 impl Extend<uint> for BitvSet {
     #[inline]
-    fn extend<I: Iterator<uint>>(&mut self, mut iterator: I) {
+    fn extend<I: Iterator<Item=uint>>(&mut self, mut iterator: I) {
         for i in iterator {
             self.insert(i);
         }
@@ -1792,7 +1794,9 @@ pub struct Difference<'a>(TwoBitPositions<'a>);
 pub struct SymmetricDifference<'a>(TwoBitPositions<'a>);
 
 #[stable]
-impl<'a> Iterator<uint> for SetIter<'a> {
+impl<'a> Iterator for SetIter<'a> {
+    type Item = uint;
+
     fn next(&mut self) -> Option<uint> {
         while self.next_idx < self.set.bitv.len() {
             let idx = self.next_idx;
@@ -1813,7 +1817,9 @@ impl<'a> Iterator<uint> for SetIter<'a> {
 }
 
 #[stable]
-impl<'a> Iterator<uint> for TwoBitPositions<'a> {
+impl<'a> Iterator for TwoBitPositions<'a> {
+    type Item = uint;
+
     fn next(&mut self) -> Option<uint> {
         while self.next_idx < self.set.bitv.len() ||
               self.next_idx < self.other.bitv.len() {
@@ -1849,25 +1855,33 @@ impl<'a> Iterator<uint> for TwoBitPositions<'a> {
 }
 
 #[stable]
-impl<'a> Iterator<uint> for Union<'a> {
+impl<'a> Iterator for Union<'a> {
+    type Item = uint;
+
     #[inline] fn next(&mut self) -> Option<uint> { self.0.next() }
     #[inline] fn size_hint(&self) -> (uint, Option<uint>) { self.0.size_hint() }
 }
 
 #[stable]
-impl<'a> Iterator<uint> for Intersection<'a> {
+impl<'a> Iterator for Intersection<'a> {
+    type Item = uint;
+
     #[inline] fn next(&mut self) -> Option<uint> { self.0.next() }
     #[inline] fn size_hint(&self) -> (uint, Option<uint>) { self.0.size_hint() }
 }
 
 #[stable]
-impl<'a> Iterator<uint> for Difference<'a> {
+impl<'a> Iterator for Difference<'a> {
+    type Item = uint;
+
     #[inline] fn next(&mut self) -> Option<uint> { self.0.next() }
     #[inline] fn size_hint(&self) -> (uint, Option<uint>) { self.0.size_hint() }
 }
 
 #[stable]
-impl<'a> Iterator<uint> for SymmetricDifference<'a> {
+impl<'a> Iterator for SymmetricDifference<'a> {
+    type Item = uint;
+
     #[inline] fn next(&mut self) -> Option<uint> { self.0.next() }
     #[inline] fn size_hint(&self) -> (uint, Option<uint>) { self.0.size_hint() }
 }
diff --git a/src/libcollections/btree/map.rs b/src/libcollections/btree/map.rs
index da98c19e888..13178893723 100644
--- a/src/libcollections/btree/map.rs
+++ b/src/libcollections/btree/map.rs
@@ -823,7 +823,7 @@ mod stack {
 
 #[stable]
 impl<K: Ord, V> FromIterator<(K, V)> for BTreeMap<K, V> {
-    fn from_iter<T: Iterator<(K, V)>>(iter: T) -> BTreeMap<K, V> {
+    fn from_iter<T: Iterator<Item=(K, V)>>(iter: T) -> BTreeMap<K, V> {
         let mut map = BTreeMap::new();
         map.extend(iter);
         map
@@ -833,7 +833,7 @@ impl<K: Ord, V> FromIterator<(K, V)> for BTreeMap<K, V> {
 #[stable]
 impl<K: Ord, V> Extend<(K, V)> for BTreeMap<K, V> {
     #[inline]
-    fn extend<T: Iterator<(K, V)>>(&mut self, mut iter: T) {
+    fn extend<T: Iterator<Item=(K, V)>>(&mut self, mut iter: T) {
         for (k, v) in iter {
             self.insert(k, v);
         }
@@ -949,8 +949,11 @@ enum StackOp<T> {
     Pop,
 }
 
-impl<K, V, E, T: Traverse<E> + DoubleEndedIterator<TraversalItem<K, V, E>>>
-        Iterator<(K, V)> for AbsIter<T> {
+impl<K, V, E, T> Iterator for AbsIter<T> where
+    T: DoubleEndedIterator + Iterator<Item=TraversalItem<K, V, E>> + Traverse<E>,
+{
+    type Item = (K, V);
+
     // This function is pretty long, but only because there's a lot of cases to consider.
     // Our iterator represents two search paths, left and right, to the smallest and largest
     // elements we have yet to yield. lca represents the least common ancestor of these two paths,
@@ -1015,8 +1018,9 @@ impl<K, V, E, T: Traverse<E> + DoubleEndedIterator<TraversalItem<K, V, E>>>
     }
 }
 
-impl<K, V, E, T: Traverse<E> + DoubleEndedIterator<TraversalItem<K, V, E>>>
-        DoubleEndedIterator<(K, V)> for AbsIter<T> {
+impl<K, V, E, T> DoubleEndedIterator for AbsIter<T> where
+    T: DoubleEndedIterator + Iterator<Item=TraversalItem<K, V, E>> + Traverse<E>,
+{
     // next_back is totally symmetric to next
     fn next_back(&mut self) -> Option<(K, V)> {
         loop {
@@ -1054,64 +1058,75 @@ impl<K, V, E, T: Traverse<E> + DoubleEndedIterator<TraversalItem<K, V, E>>>
 }
 
 #[stable]
-impl<'a, K, V> Iterator<(&'a K, &'a V)> for Iter<'a, K, V> {
+impl<'a, K, V> Iterator for Iter<'a, K, V> {
+    type Item = (&'a K, &'a V);
+
     fn next(&mut self) -> Option<(&'a K, &'a V)> { self.inner.next() }
     fn size_hint(&self) -> (uint, Option<uint>) { self.inner.size_hint() }
 }
 #[stable]
-impl<'a, K, V> DoubleEndedIterator<(&'a K, &'a V)> for Iter<'a, K, V> {
+impl<'a, K, V> DoubleEndedIterator for Iter<'a, K, V> {
     fn next_back(&mut self) -> Option<(&'a K, &'a V)> { self.inner.next_back() }
 }
 #[stable]
-impl<'a, K, V> ExactSizeIterator<(&'a K, &'a V)> for Iter<'a, K, V> {}
+impl<'a, K, V> ExactSizeIterator for Iter<'a, K, V> {}
 
 #[stable]
-impl<'a, K, V> Iterator<(&'a K, &'a mut V)> for IterMut<'a, K, V> {
+impl<'a, K, V> Iterator for IterMut<'a, K, V> {
+    type Item = (&'a K, &'a mut V);
+
     fn next(&mut self) -> Option<(&'a K, &'a mut V)> { self.inner.next() }
     fn size_hint(&self) -> (uint, Option<uint>) { self.inner.size_hint() }
 }
 #[stable]
-impl<'a, K, V> DoubleEndedIterator<(&'a K, &'a mut V)> for IterMut<'a, K, V> {
+impl<'a, K, V> DoubleEndedIterator for IterMut<'a, K, V> {
     fn next_back(&mut self) -> Option<(&'a K, &'a mut V)> { self.inner.next_back() }
 }
 #[stable]
-impl<'a, K, V> ExactSizeIterator<(&'a K, &'a mut V)> for IterMut<'a, K, V> {}
+impl<'a, K, V> ExactSizeIterator for IterMut<'a, K, V> {}
 
 #[stable]
-impl<K, V> Iterator<(K, V)> for IntoIter<K, V> {
+impl<K, V> Iterator for IntoIter<K, V> {
+    type Item = (K, V);
+
     fn next(&mut self) -> Option<(K, V)> { self.inner.next() }
     fn size_hint(&self) -> (uint, Option<uint>) { self.inner.size_hint() }
 }
 #[stable]
-impl<K, V> DoubleEndedIterator<(K, V)> for IntoIter<K, V> {
+impl<K, V> DoubleEndedIterator for IntoIter<K, V> {
     fn next_back(&mut self) -> Option<(K, V)> { self.inner.next_back() }
 }
 #[stable]
-impl<K, V> ExactSizeIterator<(K, V)> for IntoIter<K, V> {}
+impl<K, V> ExactSizeIterator for IntoIter<K, V> {}
 
 #[stable]
-impl<'a, K, V> Iterator<&'a K> for Keys<'a, K, V> {
+impl<'a, K, V> Iterator for Keys<'a, K, V> {
+    type Item = &'a K;
+
     fn next(&mut self) -> Option<(&'a K)> { self.inner.next() }
     fn size_hint(&self) -> (uint, Option<uint>) { self.inner.size_hint() }
 }
 #[stable]
-impl<'a, K, V> DoubleEndedIterator<&'a K> for Keys<'a, K, V> {
+impl<'a, K, V> DoubleEndedIterator for Keys<'a, K, V> {
     fn next_back(&mut self) -> Option<(&'a K)> { self.inner.next_back() }
 }
 #[stable]
-impl<'a, K, V> ExactSizeIterator<&'a K> for Keys<'a, K, V> {}
+impl<'a, K, V> ExactSizeIterator for Keys<'a, K, V> {}
+
 
 #[stable]
-impl<'a, K, V> Iterator<&'a V> for Values<'a, K, V> {
+impl<'a, K, V> Iterator for Values<'a, K, V> {
+    type Item = &'a V;
+
     fn next(&mut self) -> Option<(&'a V)> { self.inner.next() }
     fn size_hint(&self) -> (uint, Option<uint>) { self.inner.size_hint() }
 }
 #[stable]
-impl<'a, K, V> DoubleEndedIterator<&'a V> for Values<'a, K, V> {
+impl<'a, K, V> DoubleEndedIterator for Values<'a, K, V> {
     fn next_back(&mut self) -> Option<(&'a V)> { self.inner.next_back() }
 }
 #[stable]
-impl<'a, K, V> ExactSizeIterator<&'a V> for Values<'a, K, V> {}
+impl<'a, K, V> ExactSizeIterator for Values<'a, K, V> {}
 
 
 impl<'a, K: Ord, V> VacantEntry<'a, K, V> {
diff --git a/src/libcollections/btree/node.rs b/src/libcollections/btree/node.rs
index 3dddcae11ce..f50650c2c8b 100644
--- a/src/libcollections/btree/node.rs
+++ b/src/libcollections/btree/node.rs
@@ -210,7 +210,9 @@ impl<T> RawItems<T> {
     }
 }
 
-impl<T> Iterator<T> for RawItems<T> {
+impl<T> Iterator for RawItems<T> {
+    type Item = T;
+
     fn next(&mut self) -> Option<T> {
         if self.head == self.tail {
             None
@@ -230,7 +232,7 @@ impl<T> Iterator<T> for RawItems<T> {
     }
 }
 
-impl<T> DoubleEndedIterator<T> for RawItems<T> {
+impl<T> DoubleEndedIterator for RawItems<T> {
     fn next_back(&mut self) -> Option<T> {
         if self.head == self.tail {
             None
@@ -1321,8 +1323,10 @@ trait TraversalImpl<K, V, E> {
 /// as no deallocation needs to be done.
 struct ElemsAndEdges<Elems, Edges>(Elems, Edges);
 
-impl<K, V, E, Elems: DoubleEndedIterator<(K, V)>, Edges: DoubleEndedIterator<E>>
-        TraversalImpl<K, V, E> for ElemsAndEdges<Elems, Edges> {
+impl<K, V, E, Elems: DoubleEndedIterator, Edges: DoubleEndedIterator>
+        TraversalImpl<K, V, E> for ElemsAndEdges<Elems, Edges>
+    where Elems : Iterator<Item=(K, V)>, Edges : Iterator<Item=E>
+{
 
     fn next_kv(&mut self) -> Option<(K, V)> { self.0.next() }
     fn next_kv_back(&mut self) -> Option<(K, V)> { self.0.next_back() }
@@ -1414,8 +1418,8 @@ pub type MutTraversal<'a, K, V> = AbsTraversal<ElemsAndEdges<Zip<slice::Iter<'a,
 pub type MoveTraversal<K, V> = AbsTraversal<MoveTraversalImpl<K, V>>;
 
 
-impl<K, V, E, Impl: TraversalImpl<K, V, E>>
-        Iterator<TraversalItem<K, V, E>> for AbsTraversal<Impl> {
+impl<K, V, E, Impl: TraversalImpl<K, V, E>> Iterator for AbsTraversal<Impl> {
+    type Item = TraversalItem<K, V, E>;
 
     fn next(&mut self) -> Option<TraversalItem<K, V, E>> {
         let head_is_edge = self.head_is_edge;
@@ -1429,9 +1433,7 @@ impl<K, V, E, Impl: TraversalImpl<K, V, E>>
     }
 }
 
-impl<K, V, E, Impl: TraversalImpl<K, V, E>>
-        DoubleEndedIterator<TraversalItem<K, V, E>> for AbsTraversal<Impl> {
-
+impl<K, V, E, Impl: TraversalImpl<K, V, E>> DoubleEndedIterator for AbsTraversal<Impl> {
     fn next_back(&mut self) -> Option<TraversalItem<K, V, E>> {
         let tail_is_edge = self.tail_is_edge;
         self.tail_is_edge = !tail_is_edge;
diff --git a/src/libcollections/btree/set.rs b/src/libcollections/btree/set.rs
index 3e8988530e6..6512243ed1a 100644
--- a/src/libcollections/btree/set.rs
+++ b/src/libcollections/btree/set.rs
@@ -436,7 +436,7 @@ impl<T: Ord> BTreeSet<T> {
 
 #[stable]
 impl<T: Ord> FromIterator<T> for BTreeSet<T> {
-    fn from_iter<Iter: Iterator<T>>(iter: Iter) -> BTreeSet<T> {
+    fn from_iter<Iter: Iterator<Item=T>>(iter: Iter) -> BTreeSet<T> {
         let mut set = BTreeSet::new();
         set.extend(iter);
         set
@@ -446,7 +446,7 @@ impl<T: Ord> FromIterator<T> for BTreeSet<T> {
 #[stable]
 impl<T: Ord> Extend<T> for BTreeSet<T> {
     #[inline]
-    fn extend<Iter: Iterator<T>>(&mut self, mut iter: Iter) {
+    fn extend<Iter: Iterator<Item=T>>(&mut self, mut iter: Iter) {
         for elem in iter {
             self.insert(elem);
         }
@@ -560,28 +560,33 @@ impl<T: Show> Show for BTreeSet<T> {
 }
 
 #[stable]
-impl<'a, T> Iterator<&'a T> for Iter<'a, T> {
+impl<'a, T> Iterator for Iter<'a, T> {
+    type Item = &'a T;
+
     fn next(&mut self) -> Option<&'a T> { self.iter.next() }
     fn size_hint(&self) -> (uint, Option<uint>) { self.iter.size_hint() }
 }
 #[stable]
-impl<'a, T> DoubleEndedIterator<&'a T> for Iter<'a, T> {
+impl<'a, T> DoubleEndedIterator for Iter<'a, T> {
     fn next_back(&mut self) -> Option<&'a T> { self.iter.next_back() }
 }
 #[stable]
-impl<'a, T> ExactSizeIterator<&'a T> for Iter<'a, T> {}
+impl<'a, T> ExactSizeIterator for Iter<'a, T> {}
+
 
 #[stable]
-impl<T> Iterator<T> for IntoIter<T> {
+impl<T> Iterator for IntoIter<T> {
+    type Item = T;
+
     fn next(&mut self) -> Option<T> { self.iter.next() }
     fn size_hint(&self) -> (uint, Option<uint>) { self.iter.size_hint() }
 }
 #[stable]
-impl<T> DoubleEndedIterator<T> for IntoIter<T> {
+impl<T> DoubleEndedIterator for IntoIter<T> {
     fn next_back(&mut self) -> Option<T> { self.iter.next_back() }
 }
 #[stable]
-impl<T> ExactSizeIterator<T> for IntoIter<T> {}
+impl<T> ExactSizeIterator for IntoIter<T> {}
 
 /// Compare `x` and `y`, but return `short` if x is None and `long` if y is None
 fn cmp_opt<T: Ord>(x: Option<&T>, y: Option<&T>,
@@ -594,7 +599,9 @@ fn cmp_opt<T: Ord>(x: Option<&T>, y: Option<&T>,
 }
 
 #[stable]
-impl<'a, T: Ord> Iterator<&'a T> for Difference<'a, T> {
+impl<'a, T: Ord> Iterator for Difference<'a, T> {
+    type Item = &'a T;
+
     fn next(&mut self) -> Option<&'a T> {
         loop {
             match cmp_opt(self.a.peek(), self.b.peek(), Less, Less) {
@@ -607,7 +614,9 @@ impl<'a, T: Ord> Iterator<&'a T> for Difference<'a, T> {
 }
 
 #[stable]
-impl<'a, T: Ord> Iterator<&'a T> for SymmetricDifference<'a, T> {
+impl<'a, T: Ord> Iterator for SymmetricDifference<'a, T> {
+    type Item = &'a T;
+
     fn next(&mut self) -> Option<&'a T> {
         loop {
             match cmp_opt(self.a.peek(), self.b.peek(), Greater, Less) {
@@ -620,7 +629,9 @@ impl<'a, T: Ord> Iterator<&'a T> for SymmetricDifference<'a, T> {
 }
 
 #[stable]
-impl<'a, T: Ord> Iterator<&'a T> for Intersection<'a, T> {
+impl<'a, T: Ord> Iterator for Intersection<'a, T> {
+    type Item = &'a T;
+
     fn next(&mut self) -> Option<&'a T> {
         loop {
             let o_cmp = match (self.a.peek(), self.b.peek()) {
@@ -639,7 +650,9 @@ impl<'a, T: Ord> Iterator<&'a T> for Intersection<'a, T> {
 }
 
 #[stable]
-impl<'a, T: Ord> Iterator<&'a T> for Union<'a, T> {
+impl<'a, T: Ord> Iterator for Union<'a, T> {
+    type Item = &'a T;
+
     fn next(&mut self) -> Option<&'a T> {
         loop {
             match cmp_opt(self.a.peek(), self.b.peek(), Greater, Less) {
diff --git a/src/libcollections/dlist.rs b/src/libcollections/dlist.rs
index 68acbfcb3c3..b3d61f44563 100644
--- a/src/libcollections/dlist.rs
+++ b/src/libcollections/dlist.rs
@@ -508,7 +508,9 @@ impl<T> Drop for DList<T> {
 }
 
 #[stable]
-impl<'a, A> Iterator<&'a A> for Iter<'a, A> {
+impl<'a, A> Iterator for Iter<'a, A> {
+    type Item = &'a A;
+
     #[inline]
     fn next(&mut self) -> Option<&'a A> {
         if self.nelem == 0 {
@@ -528,7 +530,7 @@ impl<'a, A> Iterator<&'a A> for Iter<'a, A> {
 }
 
 #[stable]
-impl<'a, A> DoubleEndedIterator<&'a A> for Iter<'a, A> {
+impl<'a, A> DoubleEndedIterator for Iter<'a, A> {
     #[inline]
     fn next_back(&mut self) -> Option<&'a A> {
         if self.nelem == 0 {
@@ -543,10 +545,11 @@ impl<'a, A> DoubleEndedIterator<&'a A> for Iter<'a, A> {
 }
 
 #[stable]
-impl<'a, A> ExactSizeIterator<&'a A> for Iter<'a, A> {}
+impl<'a, A> ExactSizeIterator for Iter<'a, A> {}
 
 #[stable]
-impl<'a, A> Iterator<&'a mut A> for IterMut<'a, A> {
+impl<'a, A> Iterator for IterMut<'a, A> {
+    type Item = &'a mut A;
     #[inline]
     fn next(&mut self) -> Option<&'a mut A> {
         if self.nelem == 0 {
@@ -569,7 +572,7 @@ impl<'a, A> Iterator<&'a mut A> for IterMut<'a, A> {
 }
 
 #[stable]
-impl<'a, A> DoubleEndedIterator<&'a mut A> for IterMut<'a, A> {
+impl<'a, A> DoubleEndedIterator for IterMut<'a, A> {
     #[inline]
     fn next_back(&mut self) -> Option<&'a mut A> {
         if self.nelem == 0 {
@@ -584,7 +587,7 @@ impl<'a, A> DoubleEndedIterator<&'a mut A> for IterMut<'a, A> {
 }
 
 #[stable]
-impl<'a, A> ExactSizeIterator<&'a mut A> for IterMut<'a, A> {}
+impl<'a, A> ExactSizeIterator for IterMut<'a, A> {}
 
 /// Allows mutating a `DList` while iterating.
 #[deprecated = "Trait is deprecated, use inherent methods on the iterator instead"]
@@ -676,7 +679,9 @@ impl<'a, A> IterMut<'a, A> {
 }
 
 #[stable]
-impl<A> Iterator<A> for IntoIter<A> {
+impl<A> Iterator for IntoIter<A> {
+    type Item = A;
+
     #[inline]
     fn next(&mut self) -> Option<A> { self.list.pop_front() }
 
@@ -687,14 +692,14 @@ impl<A> Iterator<A> for IntoIter<A> {
 }
 
 #[stable]
-impl<A> DoubleEndedIterator<A> for IntoIter<A> {
+impl<A> DoubleEndedIterator for IntoIter<A> {
     #[inline]
     fn next_back(&mut self) -> Option<A> { self.list.pop_back() }
 }
 
 #[stable]
 impl<A> FromIterator<A> for DList<A> {
-    fn from_iter<T: Iterator<A>>(iterator: T) -> DList<A> {
+    fn from_iter<T: Iterator<Item=A>>(iterator: T) -> DList<A> {
         let mut ret = DList::new();
         ret.extend(iterator);
         ret
@@ -703,7 +708,7 @@ impl<A> FromIterator<A> for DList<A> {
 
 #[stable]
 impl<A> Extend<A> for DList<A> {
-    fn extend<T: Iterator<A>>(&mut self, mut iterator: T) {
+    fn extend<T: Iterator<Item=A>>(&mut self, mut iterator: T) {
         for elt in iterator { self.push_back(elt); }
     }
 }
diff --git a/src/libcollections/enum_set.rs b/src/libcollections/enum_set.rs
index ea3d8659f54..1d6caf2ccee 100644
--- a/src/libcollections/enum_set.rs
+++ b/src/libcollections/enum_set.rs
@@ -231,7 +231,9 @@ impl<E:CLike> Iter<E> {
     }
 }
 
-impl<E:CLike> Iterator<E> for Iter<E> {
+impl<E:CLike> Iterator for Iter<E> {
+    type Item = E;
+
     fn next(&mut self) -> Option<E> {
         if self.bits == 0 {
             return None;
@@ -254,7 +256,7 @@ impl<E:CLike> Iterator<E> for Iter<E> {
 }
 
 impl<E:CLike> FromIterator<E> for EnumSet<E> {
-    fn from_iter<I:Iterator<E>>(iterator: I) -> EnumSet<E> {
+    fn from_iter<I:Iterator<Item=E>>(iterator: I) -> EnumSet<E> {
         let mut ret = EnumSet::new();
         ret.extend(iterator);
         ret
@@ -262,7 +264,7 @@ impl<E:CLike> FromIterator<E> for EnumSet<E> {
 }
 
 impl<E:CLike> Extend<E> for EnumSet<E> {
-    fn extend<I: Iterator<E>>(&mut self, mut iterator: I) {
+    fn extend<I: Iterator<Item=E>>(&mut self, mut iterator: I) {
         for element in iterator {
             self.insert(element);
         }
diff --git a/src/libcollections/ring_buf.rs b/src/libcollections/ring_buf.rs
index e4c9e51a845..eb58edbe453 100644
--- a/src/libcollections/ring_buf.rs
+++ b/src/libcollections/ring_buf.rs
@@ -1151,7 +1151,9 @@ impl<'a, T> Clone for Iter<'a, T> {
 }
 
 #[stable]
-impl<'a, T> Iterator<&'a T> for Iter<'a, T> {
+impl<'a, T> Iterator for Iter<'a, T> {
+    type Item = &'a T;
+
     #[inline]
     fn next(&mut self) -> Option<&'a T> {
         if self.tail == self.head {
@@ -1170,7 +1172,7 @@ impl<'a, T> Iterator<&'a T> for Iter<'a, T> {
 }
 
 #[stable]
-impl<'a, T> DoubleEndedIterator<&'a T> for Iter<'a, T> {
+impl<'a, T> DoubleEndedIterator for Iter<'a, T> {
     #[inline]
     fn next_back(&mut self) -> Option<&'a T> {
         if self.tail == self.head {
@@ -1182,10 +1184,10 @@ impl<'a, T> DoubleEndedIterator<&'a T> for Iter<'a, T> {
 }
 
 #[stable]
-impl<'a, T> ExactSizeIterator<&'a T> for Iter<'a, T> {}
+impl<'a, T> ExactSizeIterator for Iter<'a, T> {}
 
 #[stable]
-impl<'a, T> RandomAccessIterator<&'a T> for Iter<'a, T> {
+impl<'a, T> RandomAccessIterator for Iter<'a, T> {
     #[inline]
     fn indexable(&self) -> uint {
         let (len, _) = self.size_hint();
@@ -1217,7 +1219,9 @@ pub struct IterMut<'a, T:'a> {
 }
 
 #[stable]
-impl<'a, T> Iterator<&'a mut T> for IterMut<'a, T> {
+impl<'a, T> Iterator for IterMut<'a, T> {
+    type Item = &'a mut T;
+
     #[inline]
     fn next(&mut self) -> Option<&'a mut T> {
         if self.tail == self.head {
@@ -1239,7 +1243,7 @@ impl<'a, T> Iterator<&'a mut T> for IterMut<'a, T> {
 }
 
 #[stable]
-impl<'a, T> DoubleEndedIterator<&'a mut T> for IterMut<'a, T> {
+impl<'a, T> DoubleEndedIterator for IterMut<'a, T> {
     #[inline]
     fn next_back(&mut self) -> Option<&'a mut T> {
         if self.tail == self.head {
@@ -1254,7 +1258,7 @@ impl<'a, T> DoubleEndedIterator<&'a mut T> for IterMut<'a, T> {
 }
 
 #[stable]
-impl<'a, T> ExactSizeIterator<&'a mut T> for IterMut<'a, T> {}
+impl<'a, T> ExactSizeIterator for IterMut<'a, T> {}
 
 /// A by-value RingBuf iterator
 #[stable]
@@ -1263,7 +1267,9 @@ pub struct IntoIter<T> {
 }
 
 #[stable]
-impl<T> Iterator<T> for IntoIter<T> {
+impl<T> Iterator for IntoIter<T> {
+    type Item = T;
+
     #[inline]
     fn next(&mut self) -> Option<T> {
         self.inner.pop_front()
@@ -1277,7 +1283,7 @@ impl<T> Iterator<T> for IntoIter<T> {
 }
 
 #[stable]
-impl<T> DoubleEndedIterator<T> for IntoIter<T> {
+impl<T> DoubleEndedIterator for IntoIter<T> {
     #[inline]
     fn next_back(&mut self) -> Option<T> {
         self.inner.pop_back()
@@ -1285,7 +1291,7 @@ impl<T> DoubleEndedIterator<T> for IntoIter<T> {
 }
 
 #[stable]
-impl<T> ExactSizeIterator<T> for IntoIter<T> {}
+impl<T> ExactSizeIterator for IntoIter<T> {}
 
 /// A draining RingBuf iterator
 #[unstable = "matches collection reform specification, waiting for dust to settle"]
@@ -1304,7 +1310,9 @@ impl<'a, T: 'a> Drop for Drain<'a, T> {
 }
 
 #[stable]
-impl<'a, T: 'a> Iterator<T> for Drain<'a, T> {
+impl<'a, T: 'a> Iterator for Drain<'a, T> {
+    type Item = T;
+
     #[inline]
     fn next(&mut self) -> Option<T> {
         self.inner.pop_front()
@@ -1318,7 +1326,7 @@ impl<'a, T: 'a> Iterator<T> for Drain<'a, T> {
 }
 
 #[stable]
-impl<'a, T: 'a> DoubleEndedIterator<T> for Drain<'a, T> {
+impl<'a, T: 'a> DoubleEndedIterator for Drain<'a, T> {
     #[inline]
     fn next_back(&mut self) -> Option<T> {
         self.inner.pop_back()
@@ -1326,7 +1334,7 @@ impl<'a, T: 'a> DoubleEndedIterator<T> for Drain<'a, T> {
 }
 
 #[stable]
-impl<'a, T: 'a> ExactSizeIterator<T> for Drain<'a, T> {}
+impl<'a, T: 'a> ExactSizeIterator for Drain<'a, T> {}
 
 #[stable]
 impl<A: PartialEq> PartialEq for RingBuf<A> {
@@ -1382,7 +1390,7 @@ impl<A> IndexMut<uint, A> for RingBuf<A> {
 
 #[stable]
 impl<A> FromIterator<A> for RingBuf<A> {
-    fn from_iter<T: Iterator<A>>(iterator: T) -> RingBuf<A> {
+    fn from_iter<T: Iterator<Item=A>>(iterator: T) -> RingBuf<A> {
         let (lower, _) = iterator.size_hint();
         let mut deq = RingBuf::with_capacity(lower);
         deq.extend(iterator);
@@ -1392,7 +1400,7 @@ impl<A> FromIterator<A> for RingBuf<A> {
 
 #[stable]
 impl<A> Extend<A> for RingBuf<A> {
-    fn extend<T: Iterator<A>>(&mut self, mut iterator: T) {
+    fn extend<T: Iterator<Item=A>>(&mut self, mut iterator: T) {
         for elt in iterator {
             self.push_back(elt);
         }
diff --git a/src/libcollections/slice.rs b/src/libcollections/slice.rs
index 1c1b48f8cef..92bdf0be378 100644
--- a/src/libcollections/slice.rs
+++ b/src/libcollections/slice.rs
@@ -1140,7 +1140,9 @@ struct SizeDirection {
     dir: Direction,
 }
 
-impl Iterator<(uint, uint)> for ElementSwaps {
+impl Iterator for ElementSwaps {
+    type Item = (uint, uint);
+
     #[inline]
     fn next(&mut self) -> Option<(uint, uint)> {
         fn new_pos(i: uint, s: Direction) -> uint {
@@ -1207,7 +1209,9 @@ pub struct Permutations<T> {
 }
 
 #[unstable = "trait is unstable"]
-impl<T: Clone> Iterator<Vec<T>> for Permutations<T> {
+impl<T: Clone> Iterator for Permutations<T> {
+    type Item = Vec<T>;
+
     #[inline]
     fn next(&mut self) -> Option<Vec<T>> {
         match self.swaps.next() {
diff --git a/src/libcollections/str.rs b/src/libcollections/str.rs
index 129ba77d9f7..7f35e5fd1ca 100644
--- a/src/libcollections/str.rs
+++ b/src/libcollections/str.rs
@@ -181,7 +181,9 @@ pub struct Decompositions<'a> {
     sorted: bool
 }
 
-impl<'a> Iterator<char> for Decompositions<'a> {
+impl<'a> Iterator for Decompositions<'a> {
+    type Item = char;
+
     #[inline]
     fn next(&mut self) -> Option<char> {
         match self.buffer.first() {
@@ -268,7 +270,9 @@ pub struct Recompositions<'a> {
     last_ccc: Option<u8>
 }
 
-impl<'a> Iterator<char> for Recompositions<'a> {
+impl<'a> Iterator for Recompositions<'a> {
+    type Item = char;
+
     #[inline]
     fn next(&mut self) -> Option<char> {
         loop {
@@ -357,7 +361,9 @@ pub struct Utf16Units<'a> {
     encoder: Utf16Encoder<Chars<'a>>
 }
 
-impl<'a> Iterator<u16> for Utf16Units<'a> {
+impl<'a> Iterator for Utf16Units<'a> {
+    type Item = u16;
+
     #[inline]
     fn next(&mut self) -> Option<u16> { self.encoder.next() }
 
diff --git a/src/libcollections/string.rs b/src/libcollections/string.rs
index 769679ec4d4..99273d9575b 100644
--- a/src/libcollections/string.rs
+++ b/src/libcollections/string.rs
@@ -781,7 +781,7 @@ impl fmt::Show for FromUtf16Error {
 
 #[experimental = "waiting on FromIterator stabilization"]
 impl FromIterator<char> for String {
-    fn from_iter<I:Iterator<char>>(iterator: I) -> String {
+    fn from_iter<I:Iterator<Item=char>>(iterator: I) -> String {
         let mut buf = String::new();
         buf.extend(iterator);
         buf
@@ -790,7 +790,7 @@ impl FromIterator<char> for String {
 
 #[experimental = "waiting on FromIterator stabilization"]
 impl<'a> FromIterator<&'a str> for String {
-    fn from_iter<I:Iterator<&'a str>>(iterator: I) -> String {
+    fn from_iter<I:Iterator<Item=&'a str>>(iterator: I) -> String {
         let mut buf = String::new();
         buf.extend(iterator);
         buf
@@ -799,7 +799,7 @@ impl<'a> FromIterator<&'a str> for String {
 
 #[experimental = "waiting on Extend stabilization"]
 impl Extend<char> for String {
-    fn extend<I:Iterator<char>>(&mut self, mut iterator: I) {
+    fn extend<I:Iterator<Item=char>>(&mut self, mut iterator: I) {
         let (lower_bound, _) = iterator.size_hint();
         self.reserve(lower_bound);
         for ch in iterator {
@@ -810,7 +810,7 @@ impl Extend<char> for String {
 
 #[experimental = "waiting on Extend stabilization"]
 impl<'a> Extend<&'a str> for String {
-    fn extend<I: Iterator<&'a str>>(&mut self, mut iterator: I) {
+    fn extend<I: Iterator<Item=&'a str>>(&mut self, mut iterator: I) {
         // A guess that at least one byte per iterator element will be needed.
         let (lower_bound, _) = iterator.size_hint();
         self.reserve(lower_bound);
diff --git a/src/libcollections/vec.rs b/src/libcollections/vec.rs
index 7e367927421..cba2824cf9b 100644
--- a/src/libcollections/vec.rs
+++ b/src/libcollections/vec.rs
@@ -1164,7 +1164,7 @@ impl<T: PartialEq> Vec<T> {
 
 /// Deprecated: use `unzip` directly on the iterator instead.
 #[deprecated = "use unzip directly on the iterator instead"]
-pub fn unzip<T, U, V: Iterator<(T, U)>>(iter: V) -> (Vec<T>, Vec<U>) {
+pub fn unzip<T, U, V: Iterator<Item=(T, U)>>(iter: V) -> (Vec<T>, Vec<U>) {
     iter.unzip()
 }
 
@@ -1317,7 +1317,7 @@ impl<T> ops::DerefMut for Vec<T> {
 #[experimental = "waiting on FromIterator stability"]
 impl<T> FromIterator<T> for Vec<T> {
     #[inline]
-    fn from_iter<I:Iterator<T>>(mut iterator: I) -> Vec<T> {
+    fn from_iter<I:Iterator<Item=T>>(mut iterator: I) -> Vec<T> {
         let (lower, _) = iterator.size_hint();
         let mut vector = Vec::with_capacity(lower);
         for element in iterator {
@@ -1330,7 +1330,7 @@ impl<T> FromIterator<T> for Vec<T> {
 #[experimental = "waiting on Extend stability"]
 impl<T> Extend<T> for Vec<T> {
     #[inline]
-    fn extend<I: Iterator<T>>(&mut self, mut iterator: I) {
+    fn extend<I: Iterator<Item=T>>(&mut self, mut iterator: I) {
         let (lower, _) = iterator.size_hint();
         self.reserve(lower);
         for element in iterator {
@@ -1506,7 +1506,7 @@ impl<'a> fmt::Writer for Vec<u8> {
 pub type CowVec<'a, T> = Cow<'a, Vec<T>, [T]>;
 
 impl<'a, T> FromIterator<T> for CowVec<'a, T> where T: Clone {
-    fn from_iter<I: Iterator<T>>(it: I) -> CowVec<'a, T> {
+    fn from_iter<I: Iterator<Item=T>>(it: I) -> CowVec<'a, T> {
         Cow::Owned(FromIterator::from_iter(it))
     }
 }
@@ -1557,7 +1557,9 @@ impl<T> IntoIter<T> {
     pub fn unwrap(self) -> Vec<T> { self.into_inner() }
 }
 
-impl<T> Iterator<T> for IntoIter<T> {
+impl<T> Iterator for IntoIter<T> {
+    type Item = T;
+
     #[inline]
     fn next<'a>(&'a mut self) -> Option<T> {
         unsafe {
@@ -1591,7 +1593,7 @@ impl<T> Iterator<T> for IntoIter<T> {
     }
 }
 
-impl<T> DoubleEndedIterator<T> for IntoIter<T> {
+impl<T> DoubleEndedIterator for IntoIter<T> {
     #[inline]
     fn next_back<'a>(&'a mut self) -> Option<T> {
         unsafe {
@@ -1614,7 +1616,7 @@ impl<T> DoubleEndedIterator<T> for IntoIter<T> {
     }
 }
 
-impl<T> ExactSizeIterator<T> for IntoIter<T> {}
+impl<T> ExactSizeIterator for IntoIter<T> {}
 
 #[unsafe_destructor]
 impl<T> Drop for IntoIter<T> {
@@ -1638,7 +1640,9 @@ pub struct Drain<'a, T> {
     marker: ContravariantLifetime<'a>,
 }
 
-impl<'a, T> Iterator<T> for Drain<'a, T> {
+impl<'a, T> Iterator for Drain<'a, T> {
+    type Item = T;
+
     #[inline]
     fn next(&mut self) -> Option<T> {
         unsafe {
@@ -1672,7 +1676,7 @@ impl<'a, T> Iterator<T> for Drain<'a, T> {
     }
 }
 
-impl<'a, T> DoubleEndedIterator<T> for Drain<'a, T> {
+impl<'a, T> DoubleEndedIterator for Drain<'a, T> {
     #[inline]
     fn next_back(&mut self) -> Option<T> {
         unsafe {
@@ -1695,7 +1699,7 @@ impl<'a, T> DoubleEndedIterator<T> for Drain<'a, T> {
     }
 }
 
-impl<'a, T> ExactSizeIterator<T> for Drain<'a, T> {}
+impl<'a, T> ExactSizeIterator for Drain<'a, T> {}
 
 #[unsafe_destructor]
 impl<'a, T> Drop for Drain<'a, T> {
diff --git a/src/libcollections/vec_map.rs b/src/libcollections/vec_map.rs
index 172fd56ed39..bf0c8f10e5f 100644
--- a/src/libcollections/vec_map.rs
+++ b/src/libcollections/vec_map.rs
@@ -546,7 +546,7 @@ impl<V: fmt::Show> fmt::Show for VecMap<V> {
 
 #[stable]
 impl<V> FromIterator<(uint, V)> for VecMap<V> {
-    fn from_iter<Iter: Iterator<(uint, V)>>(iter: Iter) -> VecMap<V> {
+    fn from_iter<Iter: Iterator<Item=(uint, V)>>(iter: Iter) -> VecMap<V> {
         let mut map = VecMap::new();
         map.extend(iter);
         map
@@ -555,7 +555,7 @@ impl<V> FromIterator<(uint, V)> for VecMap<V> {
 
 #[stable]
 impl<V> Extend<(uint, V)> for VecMap<V> {
-    fn extend<Iter: Iterator<(uint, V)>>(&mut self, mut iter: Iter) {
+    fn extend<Iter: Iterator<Item=(uint, V)>>(&mut self, mut iter: Iter) {
         for (k, v) in iter {
             self.insert(k, v);
         }
@@ -581,7 +581,9 @@ impl<V> IndexMut<uint, V> for VecMap<V> {
 macro_rules! iterator {
     (impl $name:ident -> $elem:ty, $($getter:ident),+) => {
         #[stable]
-        impl<'a, V> Iterator<$elem> for $name<'a, V> {
+        impl<'a, V> Iterator for $name<'a, V> {
+            type Item = $elem;
+
             #[inline]
             fn next(&mut self) -> Option<$elem> {
                 while self.front < self.back {
@@ -614,7 +616,7 @@ macro_rules! iterator {
 macro_rules! double_ended_iterator {
     (impl $name:ident -> $elem:ty, $($getter:ident),+) => {
         #[stable]
-        impl<'a, V> DoubleEndedIterator<$elem> for $name<'a, V> {
+        impl<'a, V> DoubleEndedIterator for $name<'a, V> {
             #[inline]
             fn next_back(&mut self) -> Option<$elem> {
                 while self.front < self.back {
@@ -713,32 +715,38 @@ pub struct IntoIter<V> {
 }
 
 #[stable]
-impl<'a, V> Iterator<uint> for Keys<'a, V> {
+impl<'a, V> Iterator for Keys<'a, V> {
+    type Item = uint;
+
     fn next(&mut self) -> Option<uint> { self.iter.next() }
     fn size_hint(&self) -> (uint, Option<uint>) { self.iter.size_hint() }
 }
 #[stable]
-impl<'a, V> DoubleEndedIterator<uint> for Keys<'a, V> {
+impl<'a, V> DoubleEndedIterator for Keys<'a, V> {
     fn next_back(&mut self) -> Option<uint> { self.iter.next_back() }
 }
 
 #[stable]
-impl<'a, V> Iterator<&'a V> for Values<'a, V> {
+impl<'a, V> Iterator for Values<'a, V> {
+    type Item = &'a V;
+
     fn next(&mut self) -> Option<(&'a V)> { self.iter.next() }
     fn size_hint(&self) -> (uint, Option<uint>) { self.iter.size_hint() }
 }
 #[stable]
-impl<'a, V> DoubleEndedIterator<&'a V> for Values<'a, V> {
+impl<'a, V> DoubleEndedIterator for Values<'a, V> {
     fn next_back(&mut self) -> Option<(&'a V)> { self.iter.next_back() }
 }
 
 #[stable]
-impl<V> Iterator<(uint, V)> for IntoIter<V> {
+impl<V> Iterator for IntoIter<V> {
+    type Item = (uint, V);
+
     fn next(&mut self) -> Option<(uint, V)> { self.iter.next() }
     fn size_hint(&self) -> (uint, Option<uint>) { self.iter.size_hint() }
 }
 #[stable]
-impl<V> DoubleEndedIterator<(uint, V)> for IntoIter<V> {
+impl<V> DoubleEndedIterator for IntoIter<V> {
     fn next_back(&mut self) -> Option<(uint, V)> { self.iter.next_back() }
 }