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, 8 insertions, 55 deletions

diff --git a/engine/proofview.ml b/engine/proofview.ml
index 29bb1ef39..39ef65dab 100644
--- a/engine/proofview.ml
+++ b/engine/proofview.ml
@@ -16,7 +16,6 @@
 open Pp
 open Util
 open Proofview_monad
-open Sigma.Notations
 open Context.Named.Declaration
 
 (** Main state of tactics *)
@@ -71,10 +70,8 @@ let dependent_init =
   let rec aux = function
   | TNil sigma -> [], { solution = sigma; comb = []; shelf = [] }
   | TCons (env, sigma, typ, t) ->
-    let sigma = Sigma.Unsafe.of_evar_map sigma in
-    let Sigma (econstr, sigma, _) = Evarutil.new_evar env sigma ~src ~store typ in
-    let (gl, _) = EConstr.destEvar (Sigma.to_evar_map sigma) econstr in
-    let sigma = Sigma.to_evar_map sigma in
+    let (sigma, econstr) = Evarutil.new_evar env sigma ~src ~store typ in
+    let (gl, _) = EConstr.destEvar sigma econstr in
     let ret, { solution = sol; comb = comb } = aux (t sigma econstr) in
     let entry = (econstr, typ) :: ret in
     entry, { solution = sol; comb = gl :: comb; shelf = [] }
@@ -1012,20 +1009,17 @@ let catchable_exception = function
 
 module Goal = struct
 
-  type ('a, 'r) t = {
+  type 'a t = {
     env : Environ.env;
     sigma : Evd.evar_map;
     concl : EConstr.constr ;
     self : Evar.t ; (* for compatibility with old-style definitions *)
   }
 
-  type ('a, 'b) enter =
-    { enter : 'r. ('a, 'r) t -> 'b }
-
-  let assume (gl : ('a, 'r) t) = (gl :> ([ `NF ], 'r) t)
+  let assume (gl : 'a t) = (gl :> [ `NF ] t)
 
   let env {env} = env
-  let sigma {sigma} = Sigma.Unsafe.of_evar_map sigma
+  let sigma {sigma} = sigma
   let hyps {env} = EConstr.named_context env
   let concl {concl} = concl
   let extra {sigma; self} = goal_extra sigma self
@@ -1048,7 +1042,7 @@ module Goal = struct
       tclEVARMAP >>= fun sigma ->
       try
         let (gl, sigma) = nf_gmake env sigma goal in
-        tclTHEN (Unsafe.tclEVARS sigma) (InfoL.tag (Info.DBranch) (f.enter gl))
+        tclTHEN (Unsafe.tclEVARS sigma) (InfoL.tag (Info.DBranch) (f gl))
       with e when catchable_exception e ->
         let (e, info) = CErrors.push e in
         tclZERO ~info e
@@ -1066,7 +1060,7 @@ module Goal = struct
     gmake_with info env sigma goal
 
   let enter f =
-    let f gl = InfoL.tag (Info.DBranch) (f.enter gl) in
+    let f gl = InfoL.tag (Info.DBranch) (f gl) in
     InfoL.tag (Info.Dispatch) begin
     iter_goal begin fun goal ->
       Env.get >>= fun env ->
@@ -1091,48 +1085,13 @@ module Goal = struct
     | [goal] -> begin
        Env.get >>= fun env ->
        tclEVARMAP >>= fun sigma ->
-       try f.enter (gmake env sigma goal)
+       try f (gmake env sigma goal)
        with e when catchable_exception e ->
          let (e, info) = CErrors.push e in
          tclZERO ~info e
       end
     | _ -> tclZERO NotExactlyOneSubgoal
 
-  type ('a, 'b) s_enter =
-    { s_enter : 'r. ('a, 'r) t -> ('b, 'r) Sigma.sigma }
-
-  let s_enter f =
-    InfoL.tag (Info.Dispatch) begin
-    iter_goal begin fun goal ->
-      Env.get >>= fun env ->
-      tclEVARMAP >>= fun sigma ->
-      try
-        let gl = gmake env sigma goal in
-        let Sigma (tac, sigma, _) = f.s_enter gl in
-        let sigma = Sigma.to_evar_map sigma in
-        tclTHEN (Unsafe.tclEVARS sigma) (InfoL.tag (Info.DBranch) tac)
-      with e when catchable_exception e ->
-        let (e, info) = CErrors.push e in
-        tclZERO ~info e
-    end
-    end
-
-  let nf_s_enter f =
-    InfoL.tag (Info.Dispatch) begin
-    iter_goal begin fun goal ->
-      Env.get >>= fun env ->
-      tclEVARMAP >>= fun sigma ->
-      try
-        let (gl, sigma) = nf_gmake env sigma goal in
-        let Sigma (tac, sigma, _) = f.s_enter gl in
-        let sigma = Sigma.to_evar_map sigma in
-        tclTHEN (Unsafe.tclEVARS sigma) (InfoL.tag (Info.DBranch) tac)
-      with e when catchable_exception e ->
-        let (e, info) = CErrors.push e in
-        tclZERO ~info e
-    end
-    end
-
   let goals =
     Pv.get >>= fun step ->
     let sigma = step.solution in
@@ -1156,8 +1115,6 @@ module Goal = struct
   (* compatibility *)
   let goal { self=self } = self
 
-  let lift (gl : ('a, 'r) t) _ = (gl :> ('a, 's) t)
-
 end
 
 
@@ -1281,8 +1238,4 @@ module Notations = struct
   let (>>=) = tclBIND
   let (<*>) = tclTHEN
   let (<+>) t1 t2 = tclOR t1 (fun _ -> t2)
-  type ('a, 'b) enter = ('a, 'b) Goal.enter =
-    { enter : 'r. ('a, 'r) Goal.t -> 'b }
-  type ('a, 'b) s_enter = ('a, 'b) Goal.s_enter =
-    { s_enter : 'r. ('a, 'r) Goal.t -> ('b, 'r) Sigma.sigma }
 end