Fix cascading message for unbound vars in pattern language.

Commit 5ab2b46a on 2011-10-06 introduced a hack for
suppressing redundant location informaton being tacked on to
an unbound variable error (in the TXR pattern language, not
TXR Lisp). This ugly hack broke along the way when uw_throw
was changed so that exception arguments are always lists,
because it still expects the exception object to be a string.
(The breaking change took place in 55cc8493, on 2015-02-06).

* match.c (do_txeval): In exception catch, exc is a list,
and not a string.

1 files changed, 4 insertions, 2 deletions

diff --git a/match.c b/match.c
index b90d342b..7a521416 100644
--- a/match.c
+++ b/match.c
@@ -1550,8 +1550,10 @@ static val do_txeval(val spec, val form, val bindings, val allow_unbound)
     }
 
     uw_catch (exc_sym, exc) {
-      if (stringp(exc) && !equal(exc, lit("")) &&
-          chr_str(exc, zero) == chr('('))
+      val msg = if3(consp(exc), car(exc), exc);
+
+      if (stringp(msg) && !equal(msg, lit("")) &&
+          chr_str(msg, zero) == chr('('))
       {
         uw_throw (exc_sym, exc);
       }