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, 7 deletions

diff --git a/tactics/hints.ml b/tactics/hints.ml
index 70e62eaba..773abb9f0 100644
--- a/tactics/hints.ml
+++ b/tactics/hints.ml
@@ -22,7 +22,6 @@ open Namegen
 open Libnames
 open Smartlocate
 open Misctypes
-open Tactypes
 open Termops
 open Inductiveops
 open Typing
@@ -34,7 +33,6 @@ open Pfedit
 open Tacred
 open Printer
 open Vernacexpr
-open Sigma.Notations
 
 module NamedDecl = Context.Named.Declaration
 
@@ -1363,11 +1361,7 @@ let add_hint_lemmas env sigma eapply lems hint_db =
   Hint_db.add_list env sigma hintlist' hint_db
 
 let make_local_hint_db env sigma ts eapply lems =
-  let map c =
-    let sigma = Sigma.Unsafe.of_evar_map sigma in
-    let Sigma (c, sigma, _) = c.delayed env sigma in
-    (Sigma.to_evar_map sigma, c)
-  in
+  let map c = c env sigma in
   let lems = List.map map lems in
   let sign = EConstr.named_context env in
   let ts = match ts with