Petite modif dans instantiate_pf_com: ajout de test pour l'indice 0, et uniformisation des messages d'erreur wrt instantiate

git-svn-id: svn+ssh://scm.gforge.inria.fr/svn/coq/trunk@9798 85f007b7-540e-0410-9357-904b9bb8a0f7

1 files changed, 9 insertions, 5 deletions

diff --git a/proofs/evar_refiner.ml b/proofs/evar_refiner.ml
index b395c0fd9..f0e2fef68 100644
--- a/proofs/evar_refiner.ml
+++ b/proofs/evar_refiner.ml
@@ -41,12 +41,16 @@ let instantiate_pf_com n com pfts =
   let gls = top_goal_of_pftreestate pfts in
   let sigma = gls.sigma in 
   let (sp,evi) (* as evc *) = 
-    try
-      List.nth (Evarutil.non_instantiated sigma) (n-1) 
-    with Failure _ -> 
-      error "not so many uninstantiated existential variables" in 
+    let evl = Evarutil.non_instantiated sigma in
+      if (n <= 0) then
+	error "incorrect existential variable index"
+      else if List.length evl < n then
+	  error "not so many uninstantiated existential variables"
+      else
+	List.nth evl (n-1)
+  in 
   let env = Evd.evar_env evi in
   let rawc = Constrintern.intern_constr sigma env com in 
   let evd = create_evar_defs sigma in
   let evd' = w_refine sp rawc evd in
-  change_constraints_pftreestate (evars_of evd') pfts
+    change_constraints_pftreestate (evars_of evd') pfts