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, 20 insertions, 32 deletions

diff --git a/engine/evarutil.ml b/engine/evarutil.ml
index 59ad4ef47..e8d184632 100644
--- a/engine/evarutil.ml
+++ b/engine/evarutil.ml
@@ -15,7 +15,6 @@ open Namegen
 open Pre_env
 open Environ
 open Evd
-open Sigma.Notations
 
 module RelDecl = Context.Rel.Declaration
 module NamedDecl = Context.Named.Declaration
@@ -45,8 +44,8 @@ let e_new_global evdref x =
   EConstr.of_constr (evd_comb1 (Evd.fresh_global (Global.env())) evdref x)
 
 let new_global evd x = 
-  let Sigma (c, sigma, p) = Sigma.fresh_global (Global.env()) evd x in
-  Sigma (EConstr.of_constr c, sigma, p)
+  let (evd, c) = Evd.fresh_global (Global.env()) evd x in
+  (evd, EConstr.of_constr c)
 
 (****************************************************)
 (* Expanding/testing/exposing existential variables *)
@@ -368,20 +367,17 @@ let push_rel_context_to_named_context env sigma typ =
 let default_source = Loc.tag @@ Evar_kinds.InternalHole
 
 let restrict_evar evd evk filter ?src candidates =
-  let evd = Sigma.to_evar_map evd in
   let candidates = Option.map (fun l -> List.map EConstr.Unsafe.to_constr l) candidates in
   let evd, evk' = Evd.restrict evk filter ?candidates ?src evd in
-  Sigma.Unsafe.of_pair (evk', Evd.declare_future_goal evk' evd)
+  Evd.declare_future_goal evk' evd, evk'
 
 let new_pure_evar_full evd evi =
-  let evd = Sigma.to_evar_map evd in
   let (evd, evk) = Evd.new_evar evd evi in
   let evd = Evd.declare_future_goal evk evd in
-  Sigma.Unsafe.of_pair (evk, evd)
+  (evd, evk)
 
 let new_pure_evar sign evd ?(src=default_source) ?(filter = Filter.identity) ?candidates ?(store = Store.empty) ?naming ?(principal=false) typ =
   let typ = EConstr.Unsafe.to_constr typ in
-  let evd = Sigma.to_evar_map evd in
   let candidates = Option.map (fun l -> List.map EConstr.Unsafe.to_constr l) candidates in
   let default_naming = Misctypes.IntroAnonymous in
   let naming = Option.default default_naming naming in
@@ -407,19 +403,19 @@ let new_pure_evar sign evd ?(src=default_source) ?(filter = Filter.identity) ?ca
     if principal then Evd.declare_principal_goal newevk evd
     else Evd.declare_future_goal newevk evd
   in
-  Sigma.Unsafe.of_pair (newevk, evd)
+  (evd, newevk)
 
 let new_evar_instance sign evd typ ?src ?filter ?candidates ?store ?naming ?principal instance =
   let open EConstr in
   assert (not !Flags.debug ||
             List.distinct (ids_of_named_context (named_context_of_val sign)));
-  let Sigma (newevk, evd, p) = new_pure_evar sign evd ?src ?filter ?candidates ?store ?naming ?principal typ in
-  Sigma (mkEvar (newevk,Array.of_list instance), evd, p)
+  let (evd, newevk) = new_pure_evar sign evd ?src ?filter ?candidates ?store ?naming ?principal typ in
+  evd, mkEvar (newevk,Array.of_list instance)
 
 (* [new_evar] declares a new existential in an env env with type typ *)
 (* Converting the env into the sign of the evar to define *)
 let new_evar env evd ?src ?filter ?candidates ?store ?naming ?principal typ =
-  let sign,typ',instance,subst,vsubst = push_rel_context_to_named_context env (Sigma.to_evar_map evd) typ in
+  let sign,typ',instance,subst,vsubst = push_rel_context_to_named_context env evd typ in
   let map c = subst2 subst vsubst c in
   let candidates = Option.map (fun l -> List.map map l) candidates in
   let instance =
@@ -428,27 +424,20 @@ let new_evar env evd ?src ?filter ?candidates ?store ?naming ?principal typ =
     | Some filter -> Filter.filter_list filter instance in
   new_evar_instance sign evd typ' ?src ?filter ?candidates ?store ?naming ?principal instance
 
-let new_evar_unsafe env evd ?src ?filter ?candidates ?store ?naming ?principal typ =
-  let evd = Sigma.Unsafe.of_evar_map evd in
-  let Sigma (evk, evd, _) = new_evar env evd ?src ?filter ?candidates ?store ?naming ?principal typ in
-  (Sigma.to_evar_map evd, evk)
-
 let new_type_evar env evd ?src ?filter ?naming ?principal rigid =
-  let Sigma (s, evd', p) = Sigma.new_sort_variable rigid evd in
-  let Sigma (e, evd', q) = new_evar env evd' ?src ?filter ?naming ?principal (EConstr.mkSort s) in
-  Sigma ((e, s), evd', p +> q)
+  let (evd', s) = new_sort_variable rigid evd in
+  let (evd', e) = new_evar env evd' ?src ?filter ?naming ?principal (EConstr.mkSort s) in
+  evd', (e, s)
 
 let e_new_type_evar env evdref ?src ?filter ?naming ?principal rigid =
-  let sigma = Sigma.Unsafe.of_evar_map !evdref in
-  let Sigma (c, sigma, _) = new_type_evar env sigma ?src ?filter ?naming ?principal rigid in
-  let sigma = Sigma.to_evar_map sigma in
-    evdref := sigma;
+  let (evd, c) = new_type_evar env !evdref ?src ?filter ?naming ?principal rigid in
+    evdref := evd;
     c
 
 let new_Type ?(rigid=Evd.univ_flexible) env evd = 
   let open EConstr in
-  let Sigma (s, sigma, p) = Sigma.new_sort_variable rigid evd in
-  Sigma (mkSort s, sigma, p)
+  let (evd, s) = new_sort_variable rigid evd in
+  (evd, mkSort s)
 
 let e_new_Type ?(rigid=Evd.univ_flexible) env evdref =
   let evd', s = new_sort_variable rigid !evdref in
@@ -456,7 +445,7 @@ let e_new_Type ?(rigid=Evd.univ_flexible) env evdref =
 
   (* The same using side-effect *)
 let e_new_evar env evdref ?(src=default_source) ?filter ?candidates ?store ?naming ?principal ty =
-  let (evd',ev) = new_evar_unsafe env !evdref ~src:src ?filter ?candidates ?store ?naming ?principal ty in
+  let (evd',ev) = new_evar env !evdref ~src:src ?filter ?candidates ?store ?naming ?principal ty in
   evdref := evd';
   ev
 
@@ -552,9 +541,8 @@ let rec check_and_clear_in_constr env evdref err ids global c =
             else
               let origfilter = Evd.evar_filter evi in
               let filter = Evd.Filter.apply_subfilter origfilter filter in
-              let evd = Sigma.Unsafe.of_evar_map !evdref in
-              let Sigma (_, evd, _) = restrict_evar evd evk filter None in
-              let evd = Sigma.to_evar_map evd in
+              let evd = !evdref in
+              let (evd,_) = restrict_evar evd evk filter None in
               evdref := evd;
 	    (* spiwack: hacking session to mark the old [evk] as having been "cleared" *)
 	      let evi = Evd.find !evdref evk in
@@ -723,8 +711,8 @@ let occur_evar_upto sigma n c =
 
 let judge_of_new_Type evd =
   let open EConstr in
-  let Sigma (s, evd', p) = Sigma.new_univ_variable univ_rigid evd in
-  Sigma ({ uj_val = mkSort (Type s); uj_type = mkSort (Type (Univ.super s)) }, evd', p)
+  let (evd', s) = new_univ_variable univ_rigid evd in
+  (evd', { uj_val = mkSort (Type s); uj_type = mkSort (Type (Univ.super s)) })
 
 let subterm_source evk (loc,k) =
   let evk = match k with