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, 12 insertions, 14 deletions

diff --git a/tactics/contradiction.ml b/tactics/contradiction.ml
index 5e7090ded..83c2be410 100644
--- a/tactics/contradiction.ml
+++ b/tactics/contradiction.ml
@@ -25,22 +25,20 @@ let mk_absurd_proof coq_not t =
     mkLambda (Names.Name id,t,mkApp (mkRel 2,[|mkRel 1|])))
 
 let absurd c =
-  Proofview.Goal.s_enter { s_enter = begin fun gl ->
+  Proofview.Goal.enter begin fun gl ->
     let sigma = Proofview.Goal.sigma gl in
     let env = Proofview.Goal.env gl in
-    let sigma = Sigma.to_evar_map sigma in
     let j = Retyping.get_judgment_of env sigma c in
     let sigma, j = Coercion.inh_coerce_to_sort env sigma j in
     let t = j.Environ.utj_val in
-    let tac =
+    Proofview.Unsafe.tclEVARS sigma <*>
     Tacticals.New.pf_constr_of_global (build_coq_not ()) >>= fun coqnot ->
     Tacticals.New.pf_constr_of_global (build_coq_False ()) >>= fun coqfalse ->
     Tacticals.New.tclTHENLIST [
       elim_type coqfalse;
       Simple.apply (mk_absurd_proof coqnot t)
-    ] in
-    Sigma.Unsafe.of_pair (tac, sigma)
-  end }
+    ]
+  end
 
 let absurd c = absurd c
 
@@ -54,13 +52,13 @@ let filter_hyp f tac =
     | [] -> Proofview.tclZERO Not_found
     | d::rest when f (NamedDecl.get_type d) -> tac (NamedDecl.get_id d)
     | _::rest -> seek rest in
-  Proofview.Goal.enter { enter = begin fun gl ->
+  Proofview.Goal.enter begin fun gl ->
     let hyps = Proofview.Goal.hyps (Proofview.Goal.assume gl) in
     seek hyps
-  end }
+  end
 
 let contradiction_context =
-  Proofview.Goal.enter { enter = begin fun gl ->
+  Proofview.Goal.enter begin fun gl ->
     let sigma = Tacmach.New.project gl in
     let env = Proofview.Goal.env gl in
     let rec seek_neg l = match l with
@@ -89,11 +87,11 @@ let contradiction_context =
                | None ->
                  Tacticals.New.tclZEROMSG (Pp.str"Not a negated unit type."))
 	      (Proofview.tclORELSE
-                 (Proofview.Goal.enter { enter = begin fun gl ->
+                 (Proofview.Goal.enter begin fun gl ->
                    let is_conv_leq = Tacmach.New.pf_apply is_conv_leq gl in
 	           filter_hyp (fun typ -> is_conv_leq typ t)
 		     (fun id' -> simplest_elim (mkApp (mkVar id,[|mkVar id'|])))
-                 end })
+                 end)
                  begin function (e, info) -> match e with
 	           | Not_found -> seek_neg rest
                    | e -> Proofview.tclZERO ~info e
@@ -102,7 +100,7 @@ let contradiction_context =
     in
     let hyps = Proofview.Goal.hyps (Proofview.Goal.assume gl) in
     seek_neg hyps
-  end }
+  end
 
 let is_negation_of env sigma typ t =
   match EConstr.kind sigma (whd_all env sigma t) with
@@ -111,7 +109,7 @@ let is_negation_of env sigma typ t =
     | _ -> false
 
 let contradiction_term (c,lbind as cl) =
-  Proofview.Goal.enter { enter = begin fun gl ->
+  Proofview.Goal.enter begin fun gl ->
     let sigma = Tacmach.New.project gl in
     let env = Proofview.Goal.env gl in
     let type_of = Tacmach.New.pf_unsafe_type_of gl in
@@ -134,7 +132,7 @@ let contradiction_term (c,lbind as cl) =
           | Not_found -> Tacticals.New.tclZEROMSG (Pp.str"Not a contradiction.")
           | e -> Proofview.tclZERO ~info e
         end
-  end }
+  end
 
 let contradiction = function
   | None -> Tacticals.New.tclTHEN intros contradiction_context