binary_heap: Forward ExactSizeIterator::is_empty

src/libcollections/binary_heap.rs

@@ -986,7 +986,11 @@ impl<'a, T> DoubleEndedIterator for Iter<'a, T> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<'a, T> ExactSizeIterator for Iter<'a, T> {}
+impl<'a, T> ExactSizeIterator for Iter<'a, T> {
+    fn is_empty(&self) -> bool {
+        self.iter.is_empty()
+    }
+}
 
 #[unstable(feature = "fused", issue = "35602")]
 impl<'a, T> FusedIterator for Iter<'a, T> {}
@@ -1022,7 +1026,11 @@ impl<T> DoubleEndedIterator for IntoIter<T> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<T> ExactSizeIterator for IntoIter<T> {}
+impl<T> ExactSizeIterator for IntoIter<T> {
+    fn is_empty(&self) -> bool {
+        self.iter.is_empty()
+    }
+}
 
 #[unstable(feature = "fused", issue = "35602")]
 impl<T> FusedIterator for IntoIter<T> {}
@@ -1057,7 +1065,11 @@ impl<'a, T: 'a> DoubleEndedIterator for Drain<'a, T> {
 }
 
 #[stable(feature = "drain", since = "1.6.0")]
-impl<'a, T: 'a> ExactSizeIterator for Drain<'a, T> {}
+impl<'a, T: 'a> ExactSizeIterator for Drain<'a, T> {
+    fn is_empty(&self) -> bool {
+        self.iter.is_empty()
+    }
+}
 
 #[unstable(feature = "fused", issue = "35602")]
 impl<'a, T: 'a> FusedIterator for Drain<'a, T> {}