From: Claudio Sacerdoti Coen <claudio.sacerdoticoen@unibo.it>
Date: Fri, 5 Mar 2004 15:29:20 +0000 (+0000)
Subject: List.nth not guarded by try ... with. Fixed.
X-Git-Tag: v0_0_4~43
X-Git-Url: http://matita.cs.unibo.it/gitweb/?a=commitdiff_plain;h=3fec2330f2d30d47ebca0decd30bd2a457a9cbd3;p=helm.git

List.nth not guarded by try ... with. Fixed.
---

diff --git a/helm/ocaml/cic_unification/cicMetaSubst.ml b/helm/ocaml/cic_unification/cicMetaSubst.ml
index e7b0e3661..7cf16ee53 100644
--- a/helm/ocaml/cic_unification/cicMetaSubst.ml
+++ b/helm/ocaml/cic_unification/cicMetaSubst.ml
@@ -504,14 +504,19 @@ let delift n subst context metasenv l t =
                     (*CSC: deliftato la regola per il LetIn                 *)
                     (*CSC: FALSO! La regola per il LetIn non lo fa          *)
          else
-          (match List.nth context (m-k-1) with
-            Some (_,C.Def (t,_)) ->
-             (*CSC: Hmmm. This bit of reduction is not in the spirit of    *)
-             (*CSC: first order unification. Does it help or does it harm? *)
-             deliftaux k (S.lift m t)
-          | Some (_,C.Decl t) ->
-             C.Rel ((position (m-k) l) + k)
-          | None -> raise (MetaSubstFailure "RelToHiddenHypothesis"))
+          (try
+            match List.nth context (m-k-1) with
+               Some (_,C.Def (t,_)) ->
+                (*CSC: Hmmm. This bit of reduction is not in the spirit of    *)
+                (*CSC: first order unification. Does it help or does it harm? *)
+                deliftaux k (S.lift m t)
+             | Some (_,C.Decl t) ->
+                C.Rel ((position (m-k) l) + k)
+             | None -> raise (MetaSubstFailure "RelToHiddenHypothesis")
+           with
+            Failure _ ->
+             raise (MetaSubstFailure "Unbound variable found in deliftaux")
+          )
      | C.Var (uri,exp_named_subst) ->
         let exp_named_subst' =
          List.map (function (uri,t) -> uri,deliftaux k t) exp_named_subst