From 1a169b01458829f9420aea9c855b1ef28e5c847d Mon Sep 17 00:00:00 2001
From: Hugo Herbelin
Date: Fri, 26 May 2017 22:34:57 +0200
Subject: Fixing a subtle bug in tclWITHHOLES.

This fixes Théo's bug on eset.
---
 tactics/tacticals.ml       | 3 ++-
 test-suite/success/evars.v | 6 ++++++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/tactics/tacticals.ml b/tactics/tacticals.ml
index 66da9ee182..b3655d3735 100644
--- a/tactics/tacticals.ml
+++ b/tactics/tacticals.ml
@@ -487,6 +487,7 @@ module New = struct
 
   let check_evars env sigma extsigma origsigma =
     let rec is_undefined_up_to_restriction sigma evk =
+      if Evd.mem origsigma evk then None else
       let evi = Evd.find sigma evk in
       match Evd.evar_body evi with
       | Evd.Evar_empty -> Some (evk,evi)
@@ -500,7 +501,7 @@ module New = struct
     let rest =
       Evd.fold_undefined (fun evk evi acc ->
         match is_undefined_up_to_restriction sigma evk with
-        | Some (evk',evi) when not (Evd.mem origsigma evk) -> (evk',evi)::acc
+        | Some (evk',evi) -> (evk',evi)::acc
         | _ -> acc)
         extsigma []
     in
diff --git a/test-suite/success/evars.v b/test-suite/success/evars.v
index 4e2bf45118..4b2f7b53e1 100644
--- a/test-suite/success/evars.v
+++ b/test-suite/success/evars.v
@@ -414,4 +414,10 @@ Axiom test : forall P1 P2, P1 = P2 -> P1 -> P2.
 Import EqNotations.
 Definition test2 {A B:Type} {H:A=B} (a:A) : B := rew H in a.
 
+(* Check that pre-existing evars are not counted as newly undefined in "set" *)
+(* Reported by Théo *)
 
+Goal exists n : nat, n = n -> True.
+eexists.
+set (H := _ = _).
+Abort.
-- 
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