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+(************************************************************************)
+(*         *   The Coq Proof Assistant / The Coq Development Team       *)
+(*  v      *   INRIA, CNRS and contributors - Copyright 1999-2018       *)
+(* <O___,, *       (see CREDITS file for the list of authors)           *)
+(*   \VV/  **************************************************************)
+(*    //   *    This file is distributed under the terms of the         *)
+(*         *     GNU Lesser General Public License Version 2.1          *)
+(*         *     (see LICENSE file for the text of the license)         *)
+(************************************************************************)
+
+open Constr
+open Univ
+
+(** {6 Constraints for type inference}
+
+    When doing conversion of universes, not only do we have =/<= constraints but
+    also Lub constraints which correspond to unification of two levels which might
+    not be necessary if unfolding is performed.
+
+    UWeak constraints come from irrelevant universes in cumulative polymorphism.
+*)
+
+type t =
+  | ULe of Universe.t * Universe.t
+  | UEq of Universe.t * Universe.t
+  | ULub of Level.t * Level.t
+  | UWeak of Level.t * Level.t
+
+val is_trivial : t -> bool
+
+module Set : sig
+  include Set.S with type elt = t
+
+  val pr : t -> Pp.t
+
+  val subst_univs : universe_subst_fn -> t -> t
+end
+
+type 'a accumulator = Set.t -> 'a -> 'a option
+type 'a constrained = 'a * Set.t
+type 'a constraint_function = 'a -> 'a -> Set.t -> Set.t
+
+val enforce_eq_instances_univs : bool -> Instance.t constraint_function
+
+(** With [force_weak] UWeak constraints are turned into equalities,
+   otherwise they're forgotten. *)
+val to_constraints : force_weak:bool -> UGraph.t -> Set.t -> Constraint.t
+
+(** [eq_constr_univs_infer_With kind1 kind2 univs m n] is a variant of
+    {!eq_constr_univs_infer} taking kind-of-term functions, to expose
+    subterms of [m] and [n], arguments. *)
+val eq_constr_univs_infer_with :
+  (constr -> (constr, types, Sorts.t, Univ.Instance.t) kind_of_term) ->
+  (constr -> (constr, types, Sorts.t, Univ.Instance.t) kind_of_term) ->
+  UGraph.t -> 'a accumulator -> constr -> constr -> 'a -> 'a option