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, 4 insertions, 7 deletions

diff --git a/plugins/funind/recdef.ml b/plugins/funind/recdef.ml
index e6f199dba..ff397d2e9 100644
--- a/plugins/funind/recdef.ml
+++ b/plugins/funind/recdef.ml
@@ -42,7 +42,6 @@ open Auto
 open Eauto
 
 open Indfun_common
-open Sigma.Notations
 open Context.Rel.Declaration
 
 (* Ugly things which should not be here *)
@@ -700,11 +699,9 @@ let mkDestructEq :
     observe_tclTHENLIST (str "mkDestructEq")
      [Proofview.V82.of_tactic (generalize new_hyps);
       (fun g2 ->
-        let changefun patvars = { run = fun sigma ->
-          let redfun = pattern_occs [Locus.AllOccurrencesBut [1], expr] in
-          let Sigma (c, sigma, p) = redfun.Reductionops.e_redfun (pf_env g2) sigma (pf_concl g2) in
-          Sigma (c, sigma, p)
-        } in
+        let changefun patvars sigma =
+          pattern_occs [Locus.AllOccurrencesBut [1], expr] (pf_env g2) sigma (pf_concl g2)
+        in
 	Proofview.V82.of_tactic (change_in_concl None changefun) g2);
       Proofview.V82.of_tactic (simplest_case expr)]), to_revert
 
@@ -1357,7 +1354,7 @@ let open_new_goal build_proof sigma using_lemmas ref_ goal_name (gls_type,decomp
 			  (Proofview.V82.of_tactic e_assumption);
 		      Eauto.eauto_with_bases
 			(true,5)
-			[{ Tacexpr.delayed = fun _ sigma -> Sigma.here (Lazy.force refl_equal) sigma}]
+			[(fun _ sigma -> (sigma, (Lazy.force refl_equal)))]
 			[Hints.Hint_db.empty empty_transparent_state false]
 		      ]
 		    )