std/extra: Add ExactSize for Bitv, DList, RingBuf, Option iterators

1 files changed, 3 insertions, 1 deletions

diff --git a/src/libstd/option.rs b/src/libstd/option.rs
index f99a595f2eb..dd66630187d 100644
--- a/src/libstd/option.rs
+++ b/src/libstd/option.rs
@@ -46,7 +46,7 @@ use cmp::{Eq,Ord};
 use util;
 use num::Zero;
 use iterator;
-use iterator::{Iterator, DoubleEndedIterator};
+use iterator::{Iterator, DoubleEndedIterator, ExactSize};
 use str::{StrSlice, OwnedStr};
 use to_str::ToStr;
 use clone::DeepClone;
@@ -402,6 +402,8 @@ impl<A> DoubleEndedIterator<A> for OptionIterator<A> {
     }
 }
 
+impl<A> ExactSize<A> for OptionIterator<A> {}
+
 #[cfg(test)]
 mod tests {
     use super::*;