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diff --git a/plugins/ltac/evar_tactics.ml b/plugins/ltac/evar_tactics.ml
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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 Util
+open Names
+open Term
+open CErrors
+open Evar_refiner
+open Tacmach
+open Tacexpr
+open Refiner
+open Evd
+open Locus
+open Context.Named.Declaration
+open Ltac_pretype
+
+module NamedDecl = Context.Named.Declaration
+
+(* The instantiate tactic *)
+
+let instantiate_evar evk (ist,rawc) sigma =
+  let evi = Evd.find sigma evk in
+  let filtered = Evd.evar_filtered_env evi in
+  let constrvars = Tacinterp.extract_ltac_constr_values ist filtered in
+  let lvar = {
+    ltac_constrs = constrvars;
+    ltac_uconstrs = Names.Id.Map.empty;
+    ltac_idents = Names.Id.Map.empty;
+    ltac_genargs = ist.Geninterp.lfun;
+  } in
+  let sigma' = w_refine (evk,evi) (lvar ,rawc) sigma in
+  tclEVARS sigma'
+
+let evar_list sigma c =
+  let rec evrec acc c =
+    match EConstr.kind sigma c with
+    | Evar (evk, _ as ev) -> ev :: acc
+    | _ -> EConstr.fold sigma evrec acc c in
+  evrec [] c
+
+let instantiate_tac n c ido =
+  Proofview.V82.tactic begin fun gl ->
+  let sigma = gl.sigma in
+  let evl =
+    match ido with
+	ConclLocation () -> evar_list sigma (pf_concl gl)
+      | HypLocation (id,hloc) ->
+	  let decl = Environ.lookup_named_val id (Goal.V82.hyps sigma (sig_it gl)) in
+	    match hloc with
+		InHyp ->
+		  (match decl with
+                    | LocalAssum (_,typ) -> evar_list sigma (EConstr.of_constr typ)
+		    | _ -> user_err Pp.(str "Please be more specific: in type or value?"))
+	      | InHypTypeOnly ->
+		  evar_list sigma (EConstr.of_constr (NamedDecl.get_type decl))
+	      | InHypValueOnly ->
+		  (match decl with
+		    | LocalDef (_,body,_) -> evar_list sigma (EConstr.of_constr body)
+		    | _ -> user_err Pp.(str "Not a defined hypothesis.")) in
+  if List.length evl < n then
+    user_err Pp.(str "Not enough uninstantiated existential variables.");
+  if n <= 0 then user_err Pp.(str "Incorrect existential variable index.");
+  let evk,_ = List.nth evl (n-1) in
+  instantiate_evar evk c sigma gl
+  end
+
+let instantiate_tac_by_name id c =
+  Proofview.V82.tactic begin fun gl ->
+  let sigma = gl.sigma in
+  let evk =
+    try Evd.evar_key id sigma
+    with Not_found -> user_err Pp.(str "Unknown existential variable.") in
+  instantiate_evar evk c sigma gl
+  end
+
+let let_evar name typ =
+  let src = (Loc.tag Evar_kinds.GoalEvar) in
+  Proofview.Goal.enter begin fun gl ->
+    let sigma = Tacmach.New.project gl in
+    let env = Proofview.Goal.env gl in
+    let sigma = ref sigma in
+    let _ = Typing.e_sort_of env sigma typ in
+    let sigma = !sigma in
+    let id = match name with
+    | Name.Anonymous ->
+      let id = Namegen.id_of_name_using_hdchar env sigma typ name in
+      Namegen.next_ident_away_in_goal id (Termops.vars_of_env env)
+    | Name.Name id -> id
+    in
+    let (sigma, evar) = Evarutil.new_evar env sigma ~src ~naming:(Misctypes.IntroFresh id) typ in
+    Tacticals.New.tclTHEN (Proofview.Unsafe.tclEVARS sigma)
+    (Tactics.letin_tac None (Name.Name id) evar None Locusops.nowhere)
+  end
+  
+let hget_evar n =
+  let open EConstr in
+  Proofview.Goal.nf_enter begin fun gl ->
+  let sigma = Tacmach.New.project gl in
+  let concl = Proofview.Goal.concl gl in
+  let evl = evar_list sigma concl in
+  if List.length evl < n then
+    user_err Pp.(str "Not enough uninstantiated existential variables.");
+  if n <= 0 then user_err Pp.(str "Incorrect existential variable index.");
+  let ev = List.nth evl (n-1) in
+  let ev_type = EConstr.existential_type sigma ev in
+  Tactics.change_concl (mkLetIn (Name.Anonymous,mkEvar ev,ev_type,concl))
+  end