range.c: return nil for empty range

* range.c (range_last): return nil for empty range, or in the case the
  predecessor is smaller than the begin.  [Bug #8739]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@42407 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 9 insertions, 2 deletions

diff --git a/range.c b/range.c
index c805848abd..007625469e 100644
--- a/range.c
+++ b/range.c
@@ -891,8 +891,15 @@ range_last(int argc, VALUE *argv, VALUE range)
 	VALUE e = RANGE_END(range);
 	if (!EXCL(range)) return e; /* inclusive, the end is the last */
 	/* exclusive, the last is previous to the end */
-	if (FIXNUM_P(e) || rb_obj_is_kind_of(e, rb_cNumeric))
-	    return rb_int_pred(e);
+	if (FIXNUM_P(e) || rb_obj_is_kind_of(e, rb_cNumeric)) {
+	    VALUE pred = rb_int_pred(e);
+	    if (!r_lt(RANGE_BEG(range), pred)) {
+		/* TODO: what should be returned, or should raise an
+		 * exception? */
+		pred = Qnil;
+	    }
+	    return pred;
+	}
 
 	/* fallback to Array */
     }