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, 4 insertions, 4 deletions

diff --git a/src/test/run-pass/cmp-default.rs b/src/test/run-pass/cmp-default.rs
index 7805a2bb49e..cfba87c3f69 100644
--- a/src/test/run-pass/cmp-default.rs
+++ b/src/test/run-pass/cmp-default.rs
@@ -31,10 +31,10 @@ impl PartialEq for Int {
 }
 
 impl PartialOrd for Int {
-    fn lt(&self, other: &Int) -> bool {
+    fn partial_cmp(&self, other: &Int) -> Option<Ordering> {
         let Int(this) = *self;
         let Int(other) = *other;
-        this < other
+        this.partial_cmp(&other)
     }
 }
 
@@ -49,10 +49,10 @@ impl PartialEq for RevInt {
 }
 
 impl PartialOrd for RevInt {
-    fn lt(&self, other: &RevInt) -> bool {
+    fn partial_cmp(&self, other: &RevInt) -> Option<Ordering> {
         let RevInt(this) = *self;
         let RevInt(other) = *other;
-        this > other
+        other.partial_cmp(&this)
     }
 }