Move implementation of UnifyKey to unify_key.rs.

src/librustc/infer/type_variable.rs

@@ -453,18 +453,3 @@ impl<'tcx> ut::UnifyValue for TypeVariableValue<'tcx> {
         }
     }
 }
-
-/// Raw `TyVid` are used as the unification key for `sub_relations`;
-/// they carry no values.
-impl ut::UnifyKey for ty::TyVid {
-    type Value = ();
-    fn index(&self) -> u32 {
-        self.index
-    }
-    fn from_index(i: u32) -> ty::TyVid {
-        ty::TyVid { index: i }
-    }
-    fn tag() -> &'static str {
-        "TyVid"
-    }
-}

src/librustc/infer/unify_key.rs

@@ -12,6 +12,21 @@ pub trait ToType {
     fn to_type<'tcx>(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx>;
 }
 
+/// Raw `TyVid` are used as the unification key for `sub_relations`;
+/// they carry no values.
+impl UnifyKey for ty::TyVid {
+    type Value = ();
+    fn index(&self) -> u32 {
+        self.index
+    }
+    fn from_index(i: u32) -> ty::TyVid {
+        ty::TyVid { index: i }
+    }
+    fn tag() -> &'static str {
+        "TyVid"
+    }
+}
+
 impl UnifyKey for ty::IntVid {
     type Value = Option<IntVarValue>;
     fn index(&self) -> u32 {