Remove the Sigma (monotonous state) API.

Reminder of (some of) the reasons for removal:

- Despite the claim in sigma.mli, it does *not* prevent evar
  leaks, something like:

  fun env evd ->
  let (evd',ev) = new_evar env evd in
  (evd,ev)

  will typecheck even with Sigma-like type annotations (with a proof of
  reflexivity)

- The API stayed embryonic. Even typing functions were not ported to
  Sigma.

- Some unsafe combinators (Unsafe.tclEVARS) were replaced with slightly
  less unsafe ones (e.g. s_enter), but those ones were not marked unsafe
  at all (despite still being so).

- There was no good story for higher order functions manipulating evar
  maps. Without higher order, one can most of the time get away with
  reusing the same name for the updated evar map.

- Most of the code doing complex things with evar maps was using unsafe
  casts to sigma. This code should be fixed, but this is an orthogonal
  issue.

Of course, this was showing a nice and elegant use of GADTs, but the
cost/benefit ratio in practice did not seem good.

1 files changed, 15 insertions, 17 deletions

diff --git a/plugins/firstorder/instances.ml b/plugins/firstorder/instances.ml
index 04bca584f..e1d765a42 100644
--- a/plugins/firstorder/instances.ml
+++ b/plugins/firstorder/instances.ml
@@ -21,7 +21,6 @@ open Formula
 open Sequent
 open Names
 open Misctypes
-open Sigma.Notations
 open Context.Rel.Declaration
 
 let compare_instance inst1 inst2=
@@ -114,9 +113,7 @@ let mk_open_instance env evmap id idc m t =
   let rec aux n avoid env evmap decls =
     if Int.equal n 0 then evmap, decls else
       let nid=(fresh_id_in_env avoid var_id env) in
-      let evmap = Sigma.Unsafe.of_evar_map evmap in
-      let Sigma ((c, _), evmap, _) = Evarutil.new_type_evar env evmap Evd.univ_flexible in
-      let evmap = Sigma.to_evar_map evmap in
+      let (evmap, (c, _)) = Evarutil.new_type_evar env evmap Evd.univ_flexible in
       let decl = LocalAssum (Name nid, c) in
 	aux (n-1) (nid::avoid) (EConstr.push_rel decl env) evmap (decl::decls) in
   let evmap, decls = aux m [] env evmap [] in
@@ -126,7 +123,7 @@ let mk_open_instance env evmap id idc m t =
 
 let left_instance_tac (inst,id) continue seq=
   let open EConstr in
-  Proofview.Goal.enter { enter = begin fun gl ->
+  Proofview.Goal.enter begin fun gl ->
   let sigma = project gl in
   match inst with
       Phantom dom->
@@ -137,10 +134,10 @@ let left_instance_tac (inst,id) continue seq=
 	    [tclTHENLIST
 	       [introf;
                 (pf_constr_of_global id >>= fun idc ->
-                Proofview.Goal.enter { enter = begin fun gl ->
+                Proofview.Goal.enter begin fun gl ->
                   let id0 = List.nth (pf_ids_of_hyps gl) 0 in
                   generalize [mkApp(idc, [|mkVar id0|])]
-                end });
+                end);
 		introf;
 		tclSOLVE [wrap 1 false continue
 			    (deepen (record (id,None) seq))]];
@@ -153,7 +150,7 @@ let left_instance_tac (inst,id) continue seq=
 	  let special_generalize=
 	    if m>0 then
 	      (pf_constr_of_global id >>= fun idc ->
-		Proofview.Goal.s_enter { s_enter = begin fun gl->
+		Proofview.Goal.enter begin fun gl->
 		  let (evmap, rc, ot) = mk_open_instance (pf_env gl) (project gl) id idc m t in
 		  let gt=
 		    it_mkLambda_or_LetIn
@@ -162,8 +159,9 @@ let left_instance_tac (inst,id) continue seq=
 		    try Typing.type_of (pf_env gl) evmap gt
 		    with e when CErrors.noncritical e ->
 		      user_err Pp.(str "Untypable instance, maybe higher-order non-prenex quantification") in
-		    Sigma.Unsafe.of_pair (generalize [gt], evmap)
-                end })
+                  Proofview.tclTHEN (Proofview.Unsafe.tclEVARS evmap)
+		    (generalize [gt])
+                end)
 	    else
 	      pf_constr_of_global id >>= fun idc -> generalize [mkApp(idc,[|t|])]
 	  in
@@ -172,20 +170,20 @@ let left_instance_tac (inst,id) continue seq=
 	       introf;
 	       tclSOLVE
 		 [wrap 1 false continue (deepen (record (id,Some c) seq))]]
-  end }
+  end
 
 let right_instance_tac inst continue seq=
   let open EConstr in
-  Proofview.Goal.enter { enter = begin fun gl ->
+  Proofview.Goal.enter begin fun gl ->
   match inst with
       Phantom dom ->
 	tclTHENS (cut dom)
 	[tclTHENLIST
 	   [introf;
-            Proofview.Goal.enter { enter = begin fun gl ->
+            Proofview.Goal.enter begin fun gl ->
               let id0 = List.nth (pf_ids_of_hyps gl) 0 in
               split (ImplicitBindings [mkVar id0])
-            end };
+            end;
 	    tclSOLVE [wrap 0 true continue (deepen seq)]];
 	 tclTRY assumption]
     | Real ((0,t),_) ->
@@ -193,7 +191,7 @@ let right_instance_tac inst continue seq=
 	   (tclSOLVE [wrap 0 true continue (deepen seq)]))
     | Real ((m,t),_) ->
 	tclFAIL 0 (Pp.str "not implemented ... yet")
-  end }
+  end
 
 let instance_tac inst=
   if (snd inst)==dummy_id then
@@ -202,9 +200,9 @@ let instance_tac inst=
     left_instance_tac inst
 
 let quantified_tac lf backtrack continue seq =
-  Proofview.Goal.enter { enter = begin fun gl ->
+  Proofview.Goal.enter begin fun gl ->
   let insts=give_instances (project gl) lf seq in
     tclORELSE
       (tclFIRST (List.map (fun inst->instance_tac inst continue seq) insts))
       backtrack
-  end }
+  end