Quickly fixing bug #2996: typing functions now check when referring to

a global reference that the current (goal) env contains all the
section variables that the global reference expects to be present.

Note that the test for inclusion might be costly: everytime a
conversion happens in a section variable copied in a goal, this
conversion has to be redone when referring to a constant dependent on
this section variable.

It is unclear to me whether we should not instead give global names to
section variables so that they exist even if they are not listed in
the context of the current goal.

Here are two examples which are still problematic:
Section A.
Let B := True : Type.
Definition C := eq_refl : B = True.
Theorem D : Type.
clearbody B.
set (x := C).
unfold C in x.
(* inconsistent context *)

or

Section A.
Let B : Type.
exact True.
Qed.
Definition C := eq_refl : B = True.  (* Note that this violated the Qed. *)
Theorem D : Type.
set (x := C).
unfold C in x.
(* inconsistent context *)

1 files changed, 30 insertions, 0 deletions

diff --git a/test-suite/bugs/closed/2996.v b/test-suite/bugs/closed/2996.v
new file mode 100644
index 000000000..440cda617
--- /dev/null
+++ b/test-suite/bugs/closed/2996.v
@@ -0,0 +1,30 @@
+(* Test on definitions referring to section variables that are not any
+   longer in the current context *)
+
+Section x.
+
+  Hypothesis h : forall(n : nat), n < S n.
+
+  Definition f(n m : nat)(less : n < m) : nat := n + m.
+
+  Lemma a : forall(n : nat), f n (S n) (h n) = 1 + 2 * n.
+  Proof.
+    (* XXX *) admit.
+  Qed.
+
+  Lemma b : forall(n : nat), n < 3 + n.
+  Proof.
+    clear.
+    intros n.
+    Fail assert (H := a n).
+  Abort.
+
+  Let T := True.
+  Definition p := I : T.
+
+  Lemma paradox : False.
+  Proof.
+    clear.
+    set (T := False).
+    Fail pose proof p as H.
+  Abort.