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, 1 insertions, 5 deletions

diff --git a/plugins/ltac/g_auto.ml4 b/plugins/ltac/g_auto.ml4
index 50e8255a6..2c2a4b850 100644
--- a/plugins/ltac/g_auto.ml4
+++ b/plugins/ltac/g_auto.ml4
@@ -15,7 +15,6 @@ open Pcoq.Prim
 open Pcoq.Constr
 open Pltac
 open Hints
-open Tacexpr
 open Names
 
 DECLARE PLUGIN "g_auto"
@@ -49,10 +48,7 @@ let eval_uconstrs ist cs =
     fail_evar = false;
     expand_evars = true
   } in
-  let map c = { delayed = fun env sigma ->
-    let Sigma.Sigma (c, sigma, p) = c.delayed env sigma in
-    Sigma.Sigma (c, sigma, p)
-  } in
+  let map c env sigma = c env sigma in
   List.map (fun c -> map (Pretyping.type_uconstr ~flags ist c)) cs
 
 let pr_auto_using_raw _ _ _  = Pptactic.pr_auto_using Ppconstr.pr_constr_expr