congruence/univs: properly refresh (fix #4609)

In congruence, refresh universes including the Set/Prop ones so that
congruence works with cumulativity, not restricting itself to the
inferred types of terms that are manipulated but allowing them to be
used at more general types. This fixes bug #4609.

2 files changed, 60 insertions, 0 deletions

diff --git a/test-suite/bugs/closed/4069.v b/test-suite/bugs/closed/4069.v
index 21b03ce541..11289f7575 100644
--- a/test-suite/bugs/closed/4069.v
+++ b/test-suite/bugs/closed/4069.v
@@ -49,3 +49,42 @@ Lemma bar {A} n m (x : A) :
   skipn n (replicate m x) = replicate (m - n) x.
 Proof. intros. f_equal.
 (* 8.5: one goal, n = m - n *)
+Abort.
+
+Variable F : nat -> Set.
+Variable X : forall n, F (n + 1).
+
+Definition sequator{X Y: Set}{eq:X=Y}(x:X) : Y := eq_rec _ _ x _ eq.
+Definition tequator{X Y}{eq:X=Y}(x:X) : Y := eq_rect _ _ x _ eq.
+Polymorphic Definition pequator{X Y}{eq:X=Y}(x:X) : Y := eq_rect _ _ x _ eq.
+
+Goal {n:nat & F (S n)}.
+eexists.
+unshelve eapply (sequator (X _)).
+f_equal. (*behaves*)
+Undo 2.
+unshelve eapply (pequator (X _)).
+f_equal. (*behaves*)
+Undo 2.
+unshelve eapply (tequator (X _)).
+f_equal. (*behaves now *)
+Focus 2. exact 0.
+simpl.
+reflexivity.
+Defined.
+
+(* Part 2: modulo casts introduced by refine due to reductions in goals *)
+
+Goal {n:nat & F (S n)}.
+eexists.
+(*misbehaves, although same goal as above*)
+Set Printing All.
+unshelve refine (sequator (X _)); revgoals.
+2:exact 0. reflexivity.
+Undo 3. 
+unshelve refine (pequator (X _)); revgoals.
+f_equal.
+Undo 2.
+unshelve refine (tequator (X _)); revgoals.
+f_equal.
+Admitted.
\ No newline at end of file
diff --git a/test-suite/success/congruence.v b/test-suite/success/congruence.v
new file mode 100644
index 0000000000..873d2f9f7e
--- /dev/null
+++ b/test-suite/success/congruence.v
@@ -0,0 +1,21 @@
+(* Example by Jonathan Leivant, congruence and tauto up to universes *)
+Variables S1 S2 : Set.
+
+Goal @eq Type S1 S2 -> @eq Type S1 S2.
+intro H.
+tauto.
+Qed.
+
+Definition T1 : Type := S1.
+Definition T2 : Type := S2.
+
+Goal T1 = T1.
+congruence.
+Undo.
+tauto.
+Undo.
+unfold T1.
+congruence.
+Undo.
+tauto.
+Qed.