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, 5 deletions

diff --git a/tactics/leminv.ml b/tactics/leminv.ml
index 83f3da30a..87d815fc8 100644
--- a/tactics/leminv.ml
+++ b/tactics/leminv.ml
@@ -27,7 +27,6 @@ open Declare
 open Tacticals.New
 open Tactics
 open Decl_kinds
-open Proofview.Notations
 open Context.Named.Declaration
 
 module NamedDecl = Context.Named.Declaration
@@ -261,7 +260,7 @@ let add_inversion_lemma_exn na com comsort bool tac =
 (* ================================= *)
 
 let lemInv id c =
-  Proofview.Goal.enter { enter = begin fun gls ->
+  Proofview.Goal.enter begin fun gls ->
   try
     let clause = mk_clenv_from_env (pf_env gls) (project gls) None (c, pf_unsafe_type_of gls c) in
     let clause = clenv_constrain_last_binding (EConstr.mkVar id) clause in
@@ -274,12 +273,12 @@ let lemInv id c =
 	 user_err ~hdr:"LemInv"
 	   (str "Cannot refine current goal with the lemma " ++
 	      pr_leconstr_env (pf_env gls) (project gls) c)
-  end }
+  end
 
 let lemInv_gen id c = try_intros_until (fun id -> lemInv id c) id
 
 let lemInvIn id c ids =
-  Proofview.Goal.enter { enter = begin fun gl ->
+  Proofview.Goal.enter begin fun gl ->
     let hyps = List.map (fun id -> pf_get_hyp id gl) ids in
     let intros_replace_ids =
       let concl = Proofview.Goal.concl gl in
@@ -292,7 +291,7 @@ let lemInvIn id c ids =
     in
     ((tclTHEN (tclTHEN (bring_hyps hyps) (lemInv id c))
         (intros_replace_ids)))
-  end }
+  end
 
 let lemInvIn_gen id c l = try_intros_until (fun id -> lemInvIn id c l) id