diff --git a/phf/src/lib.rs b/phf/src/lib.rs
index 05893fd2..b81bd496 100644
--- a/phf/src/lib.rs
+++ b/phf/src/lib.rs
@@ -4,7 +4,7 @@
 //! literals, or any of the fixed-size integral types.
 #![doc(html_root_url="https://sfackler.github.io/doc")]
 #![warn(missing_docs)]
-#![feature(macro_rules, phase, globs, old_orphan_check)]
+#![feature(macro_rules, phase, globs, old_orphan_check, associated_types)]
 #![no_std]
 
 #[phase(plugin, link)]
diff --git a/phf/src/map.rs b/phf/src/map.rs
index 92c04198..a6e14e75 100644
--- a/phf/src/map.rs
+++ b/phf/src/map.rs
@@ -54,7 +54,9 @@ impl<K, V> fmt::Show for Map<K, V> where K: fmt::Show, V: fmt::Show {
     }
 }
 
-impl<K, V, Sized? T> Index<T, V> for Map<K, V> where T: Eq + PhfHash + BorrowFrom<K> {
+impl<K, V, Sized? T> Index<T> for Map<K, V> where T: Eq + PhfHash + BorrowFrom<K> {
+    type Output = V;
+
     fn index(&self, k: &T) -> &V {
         self.get(k).expect("invalid key")
     }
@@ -131,7 +133,9 @@ pub struct Entries<'a, K:'a, V:'a> {
     iter: slice::Iter<'a, (K, V)>,
 }
 
-impl<'a, K, V> Iterator<(&'a K, &'a V)> for Entries<'a, K, V> {
+impl<'a, K, V> Iterator for Entries<'a, K, V> {
+    type Item = (&'a K, &'a V);
+
     fn next(&mut self) -> Option<(&'a K, &'a V)> {
         self.iter.next().map(|&(ref k, ref v)| (k, v))
     }
@@ -141,20 +145,22 @@ impl<'a, K, V> Iterator<(&'a K, &'a V)> for Entries<'a, K, V> {
     }
 }
 
-impl<'a, K, V> DoubleEndedIterator<(&'a K, &'a V)> for Entries<'a, K, V> {
+impl<'a, K, V> DoubleEndedIterator for Entries<'a, K, V> {
     fn next_back(&mut self) -> Option<(&'a K, &'a V)> {
         self.iter.next_back().map(|e| (&e.0, &e.1))
     }
 }
 
-impl<'a, K, V> ExactSizeIterator<(&'a K, &'a V)> for Entries<'a, K, V> {}
+impl<'a, K, V> ExactSizeIterator for Entries<'a, K, V> {}
 
 /// An iterator over the keys in a `Map`.
 pub struct Keys<'a, K:'a, V:'a> {
     iter: Entries<'a, K, V>,
 }
 
-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.iter.next().map(|e| e.0)
     }
@@ -164,20 +170,22 @@ impl<'a, K, V> Iterator<&'a K> for Keys<'a, K, V> {
     }
 }
 
-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.iter.next_back().map(|e| e.0)
     }
 }
 
-impl<'a, K, V> ExactSizeIterator<&'a K> for Keys<'a, K, V> {}
+impl<'a, K, V> ExactSizeIterator for Keys<'a, K, V> {}
 
 /// An iterator over the values in a `Map`.
 pub struct Values<'a, K:'a, V:'a> {
     iter: Entries<'a, K, V>,
 }
 
-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.iter.next().map(|e| e.1)
     }
@@ -187,10 +195,10 @@ impl<'a, K, V> Iterator<&'a V> for Values<'a, K, V> {
     }
 }
 
-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.iter.next_back().map(|e| e.1)
     }
 }
 
-impl<'a, K, V> ExactSizeIterator<&'a V> for Values<'a, K, V> {}
+impl<'a, K, V> ExactSizeIterator for Values<'a, K, V> {}
diff --git a/phf/src/ordered_map.rs b/phf/src/ordered_map.rs
index 521282e4..c5be0fbe 100644
--- a/phf/src/ordered_map.rs
+++ b/phf/src/ordered_map.rs
@@ -61,7 +61,9 @@ impl<K, V> fmt::Show for OrderedMap<K, V> where K: fmt::Show, V: fmt::Show {
     }
 }
 
-impl<K, V, Sized? T> Index<T, V> for OrderedMap<K, V> where T: Eq + PhfHash + BorrowFrom<K> {
+impl<K, V, Sized? T> Index<T> for OrderedMap<K, V> where T: Eq + PhfHash + BorrowFrom<K> {
+    type Output = V;
+
     fn index(&self, k: &T) -> &V {
         self.get(k).expect("invalid key")
     }
@@ -151,7 +153,9 @@ pub struct Entries<'a, K:'a, V:'a> {
     iter: slice::Iter<'a, (K, V)>,
 }
 
-impl<'a, K, V> Iterator<(&'a K, &'a V)> for Entries<'a, K, V> {
+impl<'a, K, V> Iterator for Entries<'a, K, V> {
+    type Item = (&'a K, &'a V);
+
     fn next(&mut self) -> Option<(&'a K, &'a V)> {
         self.iter.next().map(|e| (&e.0, &e.1))
     }
@@ -161,13 +165,13 @@ impl<'a, K, V> Iterator<(&'a K, &'a V)> for Entries<'a, K, V> {
     }
 }
 
-impl<'a, K, V> DoubleEndedIterator<(&'a K, &'a V)> for Entries<'a, K, V> {
+impl<'a, K, V> DoubleEndedIterator for Entries<'a, K, V> {
     fn next_back(&mut self) -> Option<(&'a K, &'a V)> {
         self.iter.next_back().map(|e| (&e.0, &e.1))
     }
 }
 
-impl<'a, K, V> RandomAccessIterator<(&'a K, &'a V)> for Entries<'a, K, V> {
+impl<'a, K, V> RandomAccessIterator for Entries<'a, K, V> {
     fn indexable(&self) -> uint {
         self.iter.indexable()
     }
@@ -177,14 +181,16 @@ impl<'a, K, V> RandomAccessIterator<(&'a K, &'a V)> for Entries<'a, K, V> {
     }
 }
 
-impl<'a, K, V> ExactSizeIterator<(&'a K, &'a V)> for Entries<'a, K, V> {}
+impl<'a, K, V> ExactSizeIterator for Entries<'a, K, V> {}
 
 /// An iterator over the keys in a `OrderedMap`.
 pub struct Keys<'a, K:'a, V:'a> {
     iter: Entries<'a, K, V>,
 }
 
-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.iter.next().map(|e| e.0)
     }
@@ -194,13 +200,13 @@ impl<'a, K, V> Iterator<&'a K> for Keys<'a, K, V> {
     }
 }
 
-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.iter.next_back().map(|e| e.0)
     }
 }
 
-impl<'a, K, V> RandomAccessIterator<&'a K> for Keys<'a, K, V> {
+impl<'a, K, V> RandomAccessIterator for Keys<'a, K, V> {
     fn indexable(&self) -> uint {
         self.iter.indexable()
     }
@@ -210,14 +216,16 @@ impl<'a, K, V> RandomAccessIterator<&'a K> for Keys<'a, K, V> {
     }
 }
 
-impl<'a, K, V> ExactSizeIterator<&'a K> for Keys<'a, K, V> {}
+impl<'a, K, V> ExactSizeIterator for Keys<'a, K, V> {}
 
 /// An iterator over the values in a `OrderedMap`.
 pub struct Values<'a, K:'a, V:'a> {
     iter: Entries<'a, K, V>,
 }
 
-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.iter.next().map(|e| e.1)
     }
@@ -227,13 +235,13 @@ impl<'a, K, V> Iterator<&'a V> for Values<'a, K, V> {
     }
 }
 
-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.iter.next_back().map(|e| e.1)
     }
 }
 
-impl<'a, K, V> RandomAccessIterator<&'a V> for Values<'a, K, V> {
+impl<'a, K, V> RandomAccessIterator for Values<'a, K, V> {
     fn indexable(&self) -> uint {
         self.iter.indexable()
     }
@@ -243,4 +251,4 @@ impl<'a, K, V> RandomAccessIterator<&'a V> for Values<'a, K, V> {
     }
 }
 
-impl<'a, K, V> ExactSizeIterator<&'a V> for Values<'a, K, V> {}
+impl<'a, K, V> ExactSizeIterator for Values<'a, K, V> {}
diff --git a/phf/src/ordered_set.rs b/phf/src/ordered_set.rs
index 115644a9..acc60a9a 100644
--- a/phf/src/ordered_set.rs
+++ b/phf/src/ordered_set.rs
@@ -116,7 +116,9 @@ pub struct Iter<'a, T:'a> {
     iter: ordered_map::Keys<'a, T, ()>,
 }
 
-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()
@@ -128,14 +130,14 @@ impl<'a, T> Iterator<&'a T> for Iter<'a, T> {
     }
 }
 
-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()
     }
 }
 
-impl<'a, T> RandomAccessIterator<&'a T> for Iter<'a, T> {
+impl<'a, T> RandomAccessIterator for Iter<'a, T> {
     #[inline]
     fn indexable(&self) -> uint {
         self.iter.indexable()
@@ -147,5 +149,4 @@ impl<'a, T> RandomAccessIterator<&'a T> for Iter<'a, T> {
     }
 }
 
-impl<'a, T> ExactSizeIterator<&'a T> for Iter<'a, T> {}
-
+impl<'a, T> ExactSizeIterator for Iter<'a, T> {}
diff --git a/phf/src/set.rs b/phf/src/set.rs
index 83fe63d1..099f985d 100644
--- a/phf/src/set.rs
+++ b/phf/src/set.rs
@@ -104,7 +104,9 @@ pub struct Iter<'a, T:'static> {
     iter: map::Keys<'a, T, ()>,
 }
 
-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()
     }
@@ -114,10 +116,10 @@ impl<'a, T> Iterator<&'a T> for Iter<'a, T> {
     }
 }
 
-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()
     }
 }
 
-impl<'a, T> ExactSizeIterator<&'a T> for Iter<'a, T> {}
+impl<'a, T> ExactSizeIterator for Iter<'a, T> {}