diff --git a/infer/src/checkers/purityDomain.mli b/infer/src/checkers/purityDomain.mli
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+++ b/infer/src/checkers/purityDomain.mli
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+(*
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *)
+
+open! IStd
+
+module ModifiedParamIndices : sig
+  type t
+
+  val pp : Format.formatter -> t -> unit
+
+  val empty : t
+
+  val of_list : int list -> t
+
+  val is_empty : t -> bool
+
+  val mem : int -> t -> bool
+
+  val add : int -> t -> t
+end
+
+include AbstractDomain.S with type t = ModifiedParamIndices.t AbstractDomain.Types.top_lifted
+
+val pure : t
+(** Pure abstract state: no side-effect on parameters and global values. The return value depends
+    only on the value of parameters. *)
+
+val impure_global : t
+(** Impure abstract state: there may be side-effect on the parameters or global values. Or the
+    return value may depend on the machine state, e.g. `Math.random`. *)
+
+val impure_params : ModifiedParamIndices.t -> t
+(** Impure abstract state: there may be side-effect on the parameters, but not on global values. *)
+
+val is_pure : t -> bool
+
+val all_params_modified : (Exp.t * Typ.t) list -> ModifiedParamIndices.t
+
+type summary = t
+
+val pp_summary : Format.formatter -> t -> unit