1 files changed, 5 insertions, 4 deletions
diff --git a/src/librustc/middle/infer/unify.rs b/src/librustc/middle/infer/unify.rs
index 235f3f994c6..0675cec6f69 100644
--- a/src/librustc/middle/infer/unify.rs
+++ b/src/librustc/middle/infer/unify.rs
@@ -18,6 +18,7 @@ use middle::infer::{uok, ures};
 use middle::infer::InferCtxt;
 use std::cell::RefCell;
 use std::fmt::Debug;
+use std::marker::PhantomData;
 use syntax::ast;
 use util::snapshot_vec as sv;
 
@@ -79,7 +80,7 @@ pub struct UnificationTable<K:UnifyKey> {
 /// made during the snapshot may either be *committed* or *rolled back*.
 pub struct Snapshot<K:UnifyKey> {
     // Link snapshot to the key type `K` of the table.
-    marker: marker::CovariantType<K>,
+    marker: marker::PhantomData<K>,
     snapshot: sv::Snapshot,
 }
 
@@ -92,7 +93,7 @@ pub struct Node<K:UnifyKey> {
 }
 
 #[derive(Copy)]
-pub struct Delegate<K>;
+pub struct Delegate<K>(PhantomData<K>);
 
 // We can't use V:LatticeValue, much as I would like to,
 // because frequently the pattern is that V=Option<U> for some
@@ -102,14 +103,14 @@ pub struct Delegate<K>;
 impl<K:UnifyKey> UnificationTable<K> {
     pub fn new() -> UnificationTable<K> {
         UnificationTable {
-            values: sv::SnapshotVec::new(Delegate),
+            values: sv::SnapshotVec::new(Delegate(PhantomData)),
         }
     }
 
     /// Starts a new snapshot. Each snapshot must be either
     /// rolled back or committed in a "LIFO" (stack) order.
     pub fn snapshot(&mut self) -> Snapshot<K> {
-        Snapshot { marker: marker::CovariantType::<K>,
+        Snapshot { marker: marker::PhantomData::<K>,
                    snapshot: self.values.start_snapshot() }
     }