From a448ed995e376e87cbc0584dabda55eaaa7c53d2 Mon Sep 17 00:00:00 2001
From: herbelin
Date: Mon, 5 Apr 2010 11:21:44 +0000
Subject: Granting wish #2251 (forbidding rewriting a term reduced to an evar)

git-svn-id: svn+ssh://scm.gforge.inria.fr/svn/coq/trunk@12900 85f007b7-540e-0410-9357-904b9bb8a0f7
---
 pretyping/unification.ml                 | 2 +-
 test-suite/bugs/closed/shouldfail/2251.v | 5 +++++
 2 files changed, 6 insertions(+), 1 deletion(-)
 create mode 100644 test-suite/bugs/closed/shouldfail/2251.v

diff --git a/pretyping/unification.ml b/pretyping/unification.ml
index 22527a1b1a..ea491b9da5 100644
--- a/pretyping/unification.ml
+++ b/pretyping/unification.ml
@@ -763,7 +763,7 @@ let w_unify_to_subterm env ?(flags=default_unify_flags) (op,cl) evd =
   let rec matchrec cl =
     let cl = strip_outer_cast cl in
     (try
-       if closed0 cl
+       if closed0 cl && not (isEvar cl)
        then w_typed_unify env topconv flags op cl evd,cl
        else error "Bound 1"
      with ex when precatchable_exception ex ->
diff --git a/test-suite/bugs/closed/shouldfail/2251.v b/test-suite/bugs/closed/shouldfail/2251.v
new file mode 100644
index 0000000000..642717f4ac
--- /dev/null
+++ b/test-suite/bugs/closed/shouldfail/2251.v
@@ -0,0 +1,5 @@
+(* Check that rewrite does not apply to single evars *)
+
+Lemma evar_rewrite : (forall a : nat, a = 0 -> True) -> True.
+intros; eapply H.  (* goal is  ?30 = nil  *)
+rewrite plus_n_Sm.
-- 
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