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, 3 insertions, 10 deletions

diff --git a/pretyping/evarsolve.ml b/pretyping/evarsolve.ml
index de5a62726..ff0aeff75 100644
--- a/pretyping/evarsolve.ml
+++ b/pretyping/evarsolve.ml
@@ -20,7 +20,6 @@ open Retyping
 open Reductionops
 open Evarutil
 open Pretype_errors
-open Sigma.Notations
 
 let normalize_evar evd ev =
   match EConstr.kind evd (mkEvar ev) with
@@ -203,9 +202,7 @@ let restrict_evar_key evd evk filter candidates =
       let candidates = match candidates with
       | NoUpdate -> Option.map (fun l -> List.map EConstr.of_constr l) evi.evar_candidates
       | UpdateWith c -> Some c in
-      let sigma = Sigma.Unsafe.of_evar_map evd in
-      let Sigma (evk, sigma, _) = restrict_evar sigma evk filter candidates in
-      (Sigma.to_evar_map sigma, evk)
+      restrict_evar evd evk filter candidates
     end
 
 (* Restrict an applied evar and returns its restriction in the same context *)
@@ -649,9 +646,7 @@ let make_projectable_subst aliases sigma evi args =
  *)
 
 let define_evar_from_virtual_equation define_fun env evd src t_in_env ty_t_in_sign sign filter inst_in_env =
-  let evd = Sigma.Unsafe.of_evar_map evd in
-  let Sigma (evar_in_env, evd, _) = new_evar_instance sign evd ty_t_in_sign ~filter ~src inst_in_env in
-  let evd = Sigma.to_evar_map evd in
+  let (evd, evar_in_env) = new_evar_instance sign evd ty_t_in_sign ~filter ~src inst_in_env in
   let t_in_env = whd_evar evd t_in_env in
   let (evk, _) = destEvar evd evar_in_env in
   let evd = define_fun env evd None (destEvar evd evar_in_env) t_in_env in
@@ -721,10 +716,8 @@ let materialize_evar define_fun env evd k (evk1,args1) ty_in_env =
      ~status:univ_flexible (Some false) env evd (mkSort s) in
     define_evar_from_virtual_equation define_fun env evd src ty_in_env
       ty_t_in_sign sign2 filter2 inst2_in_env in
-  let evd = Sigma.Unsafe.of_evar_map evd in
-  let Sigma (ev2_in_sign, evd, _) =
+  let (evd, ev2_in_sign) =
     new_evar_instance sign2 evd ev2ty_in_sign ~filter:filter2 ~src inst2_in_sign in
-  let evd = Sigma.to_evar_map evd in
   let ev2_in_env = (fst (destEvar evd ev2_in_sign), Array.of_list inst2_in_env) in
   (evd, ev2_in_sign, ev2_in_env)