Restored a "feature" of unification in pre-8.3 (it was used e.g. in a

proof of Chung-Kil's Hur Heq package): conversion in "trivial_unify"
accepted evars as ordinary variables. I hope I did not invalidate some
features that would have needed restricting conversion on evar-free
terms, but since failure of conversion in presence of evars is redirected
to the main unification algorithm, I guess it is OK.
For better readibility, I also inlined and cleaned a bit trivial_unify.

git-svn-id: svn+ssh://scm.gforge.inria.fr/svn/coq/trunk@13193 85f007b7-540e-0410-9357-904b9bb8a0f7

1 files changed, 28 insertions, 0 deletions

diff --git a/test-suite/success/rewrite.v b/test-suite/success/rewrite.v
index 9bc680072..3bce52fe7 100644
--- a/test-suite/success/rewrite.v
+++ b/test-suite/success/rewrite.v
@@ -80,3 +80,31 @@ Undo.
 intros; inversion H; dependent rewrite <- H4 in H0.
 Abort.
 
+(* Test conversion between terms with evars that both occur in K-redexes and
+   are elsewhere solvable.
+
+   This is quite an artificial example, but it used to work in 8.2.
+
+   Since rewrite supports conversion on terms without metas, it
+   was successively unifying (id 0 ?y) and 0 where ?y was not a
+   meta but, because coming from a "_", an evar.
+
+   After commit r12440 which unified the treatment of metas and
+   evars, it stopped to work. Chung-Kil Hur's Heq package used
+   this feature. Solved in r13...
+*)
+
+Parameter g : nat -> nat -> nat.
+Definition K (x y:nat) := x.
+
+Goal (forall y, g y (K 0 y) = 0) -> g 0 0 = 0.
+intros.
+rewrite (H _).
+reflexivity.
+Qed.
+
+Goal (forall y, g (K 0 y) y = 0) -> g 0 0 = 0.
+intros.
+rewrite (H _).
+reflexivity.
+Qed.