Implement size_hint() on all remaining Iterators

Add size_hint() to the Iterators in libextra and the Iterator in
libsyntax.

Skip deque for the moment, as it's being worked on elsewhere.

src/libextra/priority_queue.rs

@@ -186,6 +186,9 @@ pub struct PriorityQueueIterator <'self, T> {
 impl<'self, T> Iterator<&'self T> for PriorityQueueIterator<'self, T> {
     #[inline]
     fn next(&mut self) -> Option<(&'self T)> { self.iter.next() }
+
+    #[inline]
+    fn size_hint(&self) -> (uint, Option<uint>) { self.iter.size_hint() }
 }
 
 #[cfg(test)]

src/libextra/treemap.rs

@@ -196,14 +196,15 @@ impl<K: TotalOrd, V> TreeMap<K, V> {
     /// Get a lazy iterator over the key-value pairs in the map.
     /// Requires that it be frozen (immutable).
     pub fn iter<'a>(&'a self) -> TreeMapIterator<'a, K, V> {
-        TreeMapIterator{stack: ~[], node: &self.root}
+        TreeMapIterator{stack: ~[], node: &self.root, remaining: self.length}
     }
 }
 
 /// Lazy forward iterator over a map
 pub struct TreeMapIterator<'self, K, V> {
     priv stack: ~[&'self ~TreeNode<K, V>],
-    priv node: &'self Option<~TreeNode<K, V>>
+    priv node: &'self Option<~TreeNode<K, V>>,
+    priv remaining: uint
 }
 
 impl<'self, K, V> Iterator<(&'self K, &'self V)> for TreeMapIterator<'self, K, V> {
@@ -220,12 +221,18 @@ impl<'self, K, V> Iterator<(&'self K, &'self V)> for TreeMapIterator<'self, K, V
               None => {
                 let res = self.stack.pop();
                 self.node = &res.right;
+                self.remaining -= 1;
                 return Some((&res.key, &res.value));
               }
             }
         }
         None
     }
+
+    #[inline]
+    fn size_hint(&self) -> (uint, Option<uint>) {
+        (self.remaining, Some(self.remaining))
+    }
 }
 
 impl<'self, T> Iterator<&'self T> for TreeSetIterator<'self, T> {

src/libsyntax/opt_vec.rs

@@ -146,4 +146,12 @@ impl<'self, T> Iterator<&'self T> for OptVecIterator<'self, T> {
             None => None
         }
     }
+
+    #[inline]
+    fn size_hint(&self) -> (uint, Option<uint>) {
+        match self.iter {
+            Some(ref x) => x.size_hint(),
+            None => (0, Some(0))
+        }
+    }
 }