From 12268bef28dea57fdbe29dc87d26ef453ad5cfed Mon Sep 17 00:00:00 2001
From: Pierre-Marie Pédrot
Date: Wed, 31 Aug 2016 11:32:28 +0200
Subject: Fix bug #5043: [Admitted] lemmas pick up section variables.

We add a flag Keep Admitted Variables that allows to recover the legacy
v8.4 behaviour of admitted lemmas. The statement of such lemmas did not
depend on the current context variables.
---
 stm/lemmas.ml                 | 18 ++++++++++++++++--
 test-suite/bugs/closed/5043.v |  8 ++++++++
 theories/Compat/Coq84.v       |  4 ++++
 3 files changed, 28 insertions(+), 2 deletions(-)
 create mode 100644 test-suite/bugs/closed/5043.v

diff --git a/stm/lemmas.ml b/stm/lemmas.ml
index 1ab695a5f2..40dbe2190b 100644
--- a/stm/lemmas.ml
+++ b/stm/lemmas.ml
@@ -461,6 +461,18 @@ let start_proof_com kind thms hook =
 
 (* Saving a proof *)
 
+let keep_admitted_vars = ref true
+
+let _ =
+  let open Goptions in
+  declare_bool_option
+    { optsync  = true;
+      optdepr  = false;
+      optname  = "keep section variables in admitted proofs";
+      optkey   = ["Keep"; "Admitted"; "Variables"];
+      optread  = (fun () -> !keep_admitted_vars);
+      optwrite = (fun b -> keep_admitted_vars := b) }
+
 let save_proof ?proof = function
   | Vernacexpr.Admitted ->
       let pe =
@@ -474,7 +486,8 @@ let save_proof ?proof = function
               error "Admitted requires an explicit statement";
             let typ = Option.get const_entry_type in
             let ctx = Evd.evar_context_universe_context (fst universes) in
-            Admitted(id, k, (const_entry_secctx, pi2 k, (typ, ctx), None), universes)
+            let sec_vars = if !keep_admitted_vars then const_entry_secctx else None in
+            Admitted(id, k, (sec_vars, pi2 k, (typ, ctx), None), universes)
         | None ->
             let pftree = Pfedit.get_pftreestate () in
             let id, k, typ = Pfedit.current_proof_statement () in
@@ -483,7 +496,8 @@ let save_proof ?proof = function
             let pproofs, _univs =
               Proof_global.return_proof ~allow_partial:true () in
             let sec_vars =
-              match  Pfedit.get_used_variables(), pproofs with
+              if not !keep_admitted_vars then None
+              else match  Pfedit.get_used_variables(), pproofs with
               | Some _ as x, _ -> x
               | None, (pproof, _) :: _ -> 
                   let env = Global.env () in
diff --git a/test-suite/bugs/closed/5043.v b/test-suite/bugs/closed/5043.v
new file mode 100644
index 0000000000..4e6a0f878f
--- /dev/null
+++ b/test-suite/bugs/closed/5043.v
@@ -0,0 +1,8 @@
+Unset Keep Admitted Variables.
+
+Section a.
+  Context (x : Type).
+  Definition foo : Type.
+  Admitted.
+End a.
+Check foo : Type.
diff --git a/theories/Compat/Coq84.v b/theories/Compat/Coq84.v
index c157c5e85d..4f6118902f 100644
--- a/theories/Compat/Coq84.v
+++ b/theories/Compat/Coq84.v
@@ -72,3 +72,7 @@ Require Coq.Lists.List.
 Require Coq.Vectors.VectorDef.
 Notation " [ x ; .. ; y ] " := (cons x .. (cons y nil) ..) : list_scope.
 Notation " [ x ; .. ; y ] " := (VectorDef.cons _ x _ .. (VectorDef.cons _ y _ (nil _)) ..) : vector_scope.
+
+(** In 8.4, the statement of admitted lemmas did not depend on the section
+    variables. *)
+Unset Keep Admitted Variables.
-- 
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