Implement RFC#28: Add PartialOrd::partial_cmp

I ended up altering the semantics of Json's PartialOrd implementation.
It used to be the case that Null < Null, but I can't think of any reason
for an ordering other than the default one so I just switched it over to
using the derived implementation.

This also fixes broken `PartialOrd` implementations for `Vec` and
`TreeMap`.

RFC: 0028-partial-cmp

1 files changed, 6 insertions, 0 deletions

diff --git a/src/libcore/slice.rs b/src/libcore/slice.rs
index 63406334103..a9e7efdf05a 100644
--- a/src/libcore/slice.rs
+++ b/src/libcore/slice.rs
@@ -253,6 +253,7 @@ pub mod traits {
     use cmp::{PartialEq, PartialOrd, Eq, Ord, Ordering, Equiv};
     use iter::order;
     use collections::Collection;
+    use option::Option;
 
     impl<'a,T:PartialEq> PartialEq for &'a [T] {
         fn eq(&self, other: & &'a [T]) -> bool {
@@ -279,6 +280,11 @@ pub mod traits {
     }
 
     impl<'a, T: PartialOrd> PartialOrd for &'a [T] {
+        #[inline]
+        fn partial_cmp(&self, other: &&'a [T]) -> Option<Ordering> {
+            order::partial_cmp(self.iter(), other.iter())
+        }
+        #[inline]
         fn lt(&self, other: & &'a [T]) -> bool {
             order::lt(self.iter(), other.iter())
         }