[sledge] Simplify Context.Subst.compose1

Summary: It is no longer necessary to test for constant terms.

Reviewed By: jvillard

Differential Revision: D25883720

fbshipit-source-id: 4b10740ae

sledge/src/fol/context.ml

@@ -88,16 +88,14 @@ end = struct
 
   (** compose a substitution with a mapping *)
   let compose1 ~key ~data r =
-    match (key : Trm.t) with
-    | Z _ | Q _ -> r
-    | _ when Trm.equal key data -> r
-    | _ ->
+    if Trm.equal key data then r
+    else (
       assert (
         Option.for_all ~f:(Trm.equal key) (Trm.Map.find key r)
         || fail "domains intersect: %a" Trm.pp key () ) ;
       let s = Trm.Map.singleton key data in
       let r' = Trm.Map.map_endo ~f:(norm s) r in
-        Trm.Map.add ~key ~data r'
+      Trm.Map.add ~key ~data r' )
 
   (** add an identity entry if the term is not already present *)
   let extend e s =