From bdd2b322d26419ee9944b804e580d5b039631569 Mon Sep 17 00:00:00 2001
From: Pierre-Marie Pédrot
Date: Sun, 11 Oct 2020 14:37:19 +0200
Subject: Fix #13169: vm_compute has existential crisis.

We simply use evars instance in the right order while reading back VM values.
---
 pretyping/vnorm.ml                 |  3 ++-
 test-suite/bugs/closed/bug_13169.v | 14 ++++++++++++++
 2 files changed, 16 insertions(+), 1 deletion(-)
 create mode 100644 test-suite/bugs/closed/bug_13169.v

diff --git a/pretyping/vnorm.ml b/pretyping/vnorm.ml
index 900ba0edb9..1420401875 100644
--- a/pretyping/vnorm.ml
+++ b/pretyping/vnorm.ml
@@ -218,7 +218,8 @@ and nf_evar env sigma evk stk =
     let t = List.fold_left fold concl hyps in
     let t, args = nf_args env sigma args t in
     let inst, args = Array.chop (List.length hyps) args in
-    let inst = Array.to_list inst in
+    (* Evar instances are reversed w.r.t. argument order *)
+    let inst = Array.rev_to_list inst in
     let c = mkApp (mkEvar (evk, inst), args) in
     nf_stk env sigma c t stk
   | _ ->
diff --git a/test-suite/bugs/closed/bug_13169.v b/test-suite/bugs/closed/bug_13169.v
new file mode 100644
index 0000000000..a0b564c725
--- /dev/null
+++ b/test-suite/bugs/closed/bug_13169.v
@@ -0,0 +1,14 @@
+Goal False.
+Proof.
+  set (H1:=I).
+  set (x:=true).
+  assert (H2: x = true) by reflexivity.
+  set (y:=false).
+  assert (H3: y = false) by reflexivity.
+  clearbody H1 x y.
+  eenough (H4: _ = false).
+  vm_compute in H4.
+  (* H4 now has "x:=y" in the evar context. *)
+  2: exact H3.
+  match type of H4 with y = false => idtac end.
+Abort.
-- 
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