[infer] rely on driving for Procdesc.Node.equal_id

Summary: Rather than explicitly defining `equal_id`, let's rely on deriving.

Reviewed By: jvillard

Differential Revision: D19977777

fbshipit-source-id: 3729b7f69

infer/src/IR/Procdesc.ml

@@ -26,9 +26,7 @@ end
 
 (* =============== START of module Node =============== *)
 module Node = struct
-  type id = int [@@deriving compare]
-
-  let equal_id = [%compare.equal: id]
+  type id = int [@@deriving compare, equal]
 
   type destruction_kind =
     | DestrBreakStmt

infer/src/IR/Procdesc.mli

@@ -24,9 +24,7 @@ module Node : sig
   type t [@@deriving compare]
 
   (** node id *)
-  type id = private int [@@deriving compare]
-
-  val equal_id : id -> id -> bool
+  type id = private int [@@deriving compare, equal]
 
   type destruction_kind =
     | DestrBreakStmt