1 files changed, 10 insertions, 8 deletions
diff --git a/catalog.ml b/catalog.ml
index 3d84af3..450966f 100755
--- a/catalog.ml
+++ b/catalog.ml
@@ -34,30 +34,32 @@ module Make(Data:DATA_SIG) = struct
 
     type 'a t = 'a sig_typ
 
+    (* Type for pure equality *)
+    type (_, _) eq = Eq : ('a, 'a) eq
 
     (** Compare two signature *)
     let eq: type a b. a sig_typ -> b sig_typ -> (a, b) T.cmp = begin fun a b ->
 
-      let cmp: type c d. c Data.typ -> d Data.typ -> ((c, d) T.cmp -> (a, b) T.cmp) -> (a, b) T.cmp =
+      let cmp: type c d. c Data.typ -> d Data.typ -> ((c, d) eq -> (a, b) T.cmp) -> (a, b) T.cmp =
         begin fun a b f -> match Data.compare_typ a b with
-        | T.Eq -> f T.Eq
+        | T.Eq -> f Eq
         | T.Lt -> T.Lt
         | T.Gt -> T.Gt
         end in
 
       match a, b with
 
-      | T1(a), T1(b) -> cmp a b (fun T.Eq -> T.Eq)
+      | T1(a), T1(b) -> cmp a b (fun Eq -> T.Eq)
 
       | T2(a, b), T2(c, d) ->
-        cmp a c (fun T.Eq ->
-          cmp b d (fun T.Eq -> T.Eq)
+        cmp a c (fun Eq ->
+          cmp b d (fun Eq -> T.Eq)
         )
 
       | T3(a, b, c), T3(d, e, f) ->
-        cmp a d (fun T.Eq ->
-          cmp b e (fun T.Eq ->
-            cmp c f (fun T.Eq -> T.Eq)
+        cmp a d (fun Eq ->
+          cmp b e (fun Eq ->
+            cmp c f (fun Eq -> T.Eq)
           )
         )