From 954fbd3b102060ed1e2122f571a430f05a174e42 Mon Sep 17 00:00:00 2001
From: Maxime Dénès
Date: Tue, 9 May 2017 22:14:35 +0200
Subject: 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.
---
 pretyping/cases.ml | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

(limited to 'pretyping/cases.ml')

diff --git a/pretyping/cases.ml b/pretyping/cases.ml
index efab5b9779..c3f392980a 100644
--- a/pretyping/cases.ml
+++ b/pretyping/cases.ml
@@ -32,7 +32,6 @@ open Evardefine
 open Evarsolve
 open Evarconv
 open Evd
-open Sigma.Notations
 open Context.Rel.Declaration
 
 module RelDecl = Context.Rel.Declaration
@@ -2000,10 +1999,8 @@ let prepare_predicate ?loc typing_fun env sigma tomatchs arsign tycon pred =
         let sigma,t = match tycon with
 	| Some t -> refresh_tycon sigma t
 	| None -> 
-          let sigma = Sigma.Unsafe.of_evar_map sigma in
-          let Sigma ((t, _), sigma, _) =
+          let (sigma, (t, _)) =
 	    new_type_evar env sigma univ_flexible_alg ~src:(Loc.tag ?loc @@ Evar_kinds.CasesType false) in
-          let sigma = Sigma.to_evar_map sigma in
 	    sigma, t
 	in
         (* First strategy: we build an "inversion" predicate *)
-- 
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