From 954fbd3b102060ed1e2122f571a430f05a174e42 Mon Sep 17 00:00:00 2001
From: Maxime Dénès
Date: Tue, 9 May 2017 22:14:35 +0200
Subject: 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.
---
 plugins/ltac/g_class.ml4 | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

(limited to 'plugins/ltac/g_class.ml4')

diff --git a/plugins/ltac/g_class.ml4 b/plugins/ltac/g_class.ml4
index 23ce368eea..dd5307638c 100644
--- a/plugins/ltac/g_class.ml4
+++ b/plugins/ltac/g_class.ml4
@@ -102,18 +102,18 @@ let rec eq_constr_mod_evars sigma x y =
   | _, _ -> compare_constr sigma (fun x y -> eq_constr_mod_evars sigma x y) x y
 
 let progress_evars t =
-  Proofview.Goal.enter { enter = begin fun gl ->
+  Proofview.Goal.enter begin fun gl ->
     let concl = Proofview.Goal.concl gl in
     let check =
-      Proofview.Goal.enter { enter = begin fun gl' ->
+      Proofview.Goal.enter begin fun gl' ->
         let sigma = Tacmach.New.project gl' in
         let newconcl = Proofview.Goal.concl gl' in
         if eq_constr_mod_evars sigma concl newconcl
         then Tacticals.New.tclFAIL 0 (Pp.str"No progress made (modulo evars)")
         else Proofview.tclUNIT ()
-      end }
+      end
     in t <*> check
-  end }
+  end
 
 TACTIC EXTEND progress_evars
   [ "progress_evars" tactic(t) ] -> [ progress_evars (Tacinterp.tactic_of_value ist t) ]
-- 
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