Implement AbsoluteRotate for Identity.

src/structs/mat.rs

@@ -18,17 +18,13 @@ mod mat_macros;
 
 /// Special identity matrix. All its operation are no-ops.
 #[deriving(Eq, Encodable, Decodable, Clone, DeepClone, Rand, Zero, ToStr)]
-pub struct Identity {
-    unused: uint // XXX: zero-sized structures ICE when used cross-crate.
-}
+pub struct Identity;
 
 impl Identity {
     /// Creates a new identity matrix.
     #[inline]
     pub fn new() -> Identity {
-        Identity {
-            unused: 0
-        }
+        Identity
     }
 }