diff --git a/src/libextra/dlist.rs b/src/libextra/dlist.rs
index b8ba7e58f2a..88159ce5552 100644
--- a/src/libextra/dlist.rs
+++ b/src/libextra/dlist.rs
@@ -25,7 +25,7 @@
 use std::cast;
 use std::ptr;
 use std::util;
-use std::iterator::{FromIterator, Invert};
+use std::iterator::{FromIterator, Extendable, Invert};
 
 use container::Deque;
 
@@ -541,11 +541,17 @@ impl<A> DoubleEndedIterator<A> for ConsumeIterator<A> {
 impl<A, T: Iterator<A>> FromIterator<A, T> for DList<A> {
     fn from_iterator(iterator: &mut T) -> DList<A> {
         let mut ret = DList::new();
-        for iterator.advance |elt| { ret.push_back(elt); }
+        ret.extend(iterator);
         ret
     }
 }
 
+impl<A, T: Iterator<A>> Extendable<A, T> for DList<A> {
+    fn extend(&mut self, iterator: &mut T) {
+        for iterator.advance |elt| { self.push_back(elt); }
+    }
+}
+
 impl<A: Eq> Eq for DList<A> {
     fn eq(&self, other: &DList<A>) -> bool {
         self.len() == other.len() &&
diff --git a/src/libextra/priority_queue.rs b/src/libextra/priority_queue.rs
index dd24a2a9eb9..1c92a4f34e5 100644
--- a/src/libextra/priority_queue.rs
+++ b/src/libextra/priority_queue.rs
@@ -16,7 +16,7 @@ use std::clone::Clone;
 use std::unstable::intrinsics::{move_val_init, init};
 use std::util::{replace, swap};
 use std::vec;
-use std::iterator::FromIterator;
+use std::iterator::{FromIterator, Extendable};
 
 /// A priority queue implemented with a binary heap
 #[deriving(Clone)]
@@ -191,20 +191,27 @@ impl<'self, T> Iterator<&'self T> for PriorityQueueIterator<'self, T> {
 }
 
 impl<T: Ord, Iter: Iterator<T>> FromIterator<T, Iter> for PriorityQueue<T> {
-    pub fn from_iterator(iter: &mut Iter) -> PriorityQueue<T> {
-        let (lower, _) = iter.size_hint();
-
+    fn from_iterator(iter: &mut Iter) -> PriorityQueue<T> {
         let mut q = PriorityQueue::new();
-        q.reserve_at_least(lower);
-
-        for iter.advance |elem| {
-            q.push(elem);
-        }
+        q.extend(iter);
 
         q
     }
 }
 
+impl<T: Ord, Iter: Iterator<T>> Extendable<T, Iter> for PriorityQueue<T> {
+    fn extend(&mut self, iter: &mut Iter) {
+        let (lower, _) = iter.size_hint();
+
+        let len = self.capacity();
+        self.reserve_at_least(len + lower);
+
+        for iter.advance |elem| {
+            self.push(elem);
+        }
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use sort::merge_sort;
diff --git a/src/libextra/ringbuf.rs b/src/libextra/ringbuf.rs
index 90f37cbf526..92183f22d3b 100644
--- a/src/libextra/ringbuf.rs
+++ b/src/libextra/ringbuf.rs
@@ -16,7 +16,7 @@
 use std::num;
 use std::uint;
 use std::vec;
-use std::iterator::{FromIterator, Invert, RandomAccessIterator};
+use std::iterator::{FromIterator, Invert, RandomAccessIterator, Extendable};
 
 use container::Deque;
 
@@ -325,14 +325,21 @@ impl<A: Eq> Eq for RingBuf<A> {
 
 impl<A, T: Iterator<A>> FromIterator<A, T> for RingBuf<A> {
     fn from_iterator(iterator: &mut T) -> RingBuf<A> {
-        let mut deq = RingBuf::new();
-        for iterator.advance |elt| {
-            deq.push_back(elt);
-        }
+        let (lower, _) = iterator.size_hint();
+        let mut deq = RingBuf::with_capacity(lower);
+        deq.extend(iterator);
         deq
     }
 }
 
+impl<A, T: Iterator<A>> Extendable<A, T> for RingBuf<A> {
+    fn extend(&mut self, iterator: &mut T) {
+        for iterator.advance |elt| {
+            self.push_back(elt);
+        }
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
diff --git a/src/libextra/treemap.rs b/src/libextra/treemap.rs
index 8c7ace56412..6148e14b79f 100644
--- a/src/libextra/treemap.rs
+++ b/src/libextra/treemap.rs
@@ -15,7 +15,7 @@
 
 use std::num;
 use std::util::{swap, replace};
-use std::iterator::FromIterator;
+use std::iterator::{FromIterator, Extendable};
 
 // This is implemented as an AA tree, which is a simplified variation of
 // a red-black tree where red (horizontal) nodes can only be added
@@ -753,29 +753,39 @@ fn remove<K: TotalOrd, V>(node: &mut Option<~TreeNode<K, V>>,
 }
 
 impl<K: TotalOrd, V, T: Iterator<(K, V)>> FromIterator<(K, V), T> for TreeMap<K, V> {
-    pub fn from_iterator(iter: &mut T) -> TreeMap<K, V> {
+    fn from_iterator(iter: &mut T) -> TreeMap<K, V> {
         let mut map = TreeMap::new();
-
-        for iter.advance |(k, v)| {
-            map.insert(k, v);
-        }
-
+        map.extend(iter);
         map
     }
 }
 
+impl<K: TotalOrd, V, T: Iterator<(K, V)>> Extendable<(K, V), T> for TreeMap<K, V> {
+    #[inline]
+    fn extend(&mut self, iter: &mut T) {
+        for iter.advance |(k, v)| {
+            self.insert(k, v);
+        }
+    }
+}
+
 impl<T: TotalOrd, Iter: Iterator<T>> FromIterator<T, Iter> for TreeSet<T> {
     pub fn from_iterator(iter: &mut Iter) -> TreeSet<T> {
         let mut set = TreeSet::new();
-
-        for iter.advance |elem| {
-            set.insert(elem);
-        }
-
+        set.extend(iter);
         set
     }
 }
 
+impl<T: TotalOrd, Iter: Iterator<T>> Extendable<T, Iter> for TreeSet<T> {
+    #[inline]
+    fn extend(&mut self, iter: &mut Iter) {
+        for iter.advance |elem| {
+            self.insert(elem);
+        }
+    }
+}
+
 #[cfg(test)]
 mod test_treemap {