From 784d82dc1a709c4c262665a4cd4eb0b1bd1487a0 Mon Sep 17 00:00:00 2001
From: Matthieu Sozeau
Date: Mon, 13 Jun 2016 18:36:58 +0200
Subject: Univs: fix for part #2 of bug #4816.

Check that the polymorphic status of everything that
is parameterized in nested sections is coherent.
---
 library/lib.ml                |  2 +-
 test-suite/bugs/closed/4816.v | 18 ++++++++++++++++++
 2 files changed, 19 insertions(+), 1 deletion(-)
 create mode 100644 test-suite/bugs/closed/4816.v

diff --git a/library/lib.ml b/library/lib.ml
index e4617cafb6..f6b4a2458b 100644
--- a/library/lib.ml
+++ b/library/lib.ml
@@ -417,7 +417,7 @@ let add_section_variable id impl poly ctx =
   match !sectab with
     | [] -> () (* because (Co-)Fixpoint temporarily uses local vars *)
     | (vars,repl,abs)::sl ->
-       check_same_poly poly vars;
+       List.iter (fun tab -> check_same_poly poly (pi1 tab)) !sectab;
        sectab := (Variable (id,impl,poly,ctx)::vars,repl,abs)::sl
 
 let add_section_context ctx =
diff --git a/test-suite/bugs/closed/4816.v b/test-suite/bugs/closed/4816.v
new file mode 100644
index 0000000000..ef79b9869b
--- /dev/null
+++ b/test-suite/bugs/closed/4816.v
@@ -0,0 +1,18 @@
+Section foo.
+Polymorphic Universes A B.
+Constraint A <= B.
+End foo.
+(* gives an anomaly Universe undefined *)
+
+or even, a refinement of #4503:
+Require Coq.Classes.RelationClasses.
+
+Class PreOrder (A : Type) (r : A -> A -> Type) : Type :=
+{ refl : forall x, r x x }.
+
+Section foo.
+  Polymorphic Universes A.
+  Section bar.
+    Context {A : Type@{A}} {rA : A -> A -> Prop} {PO : PreOrder A rA}.
+  End bar.
+End foo.
\ No newline at end of file
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