Make nth on subvec throw exception for negative indices

Signed-off-by: Stuart Halloway <stu@thinkrelevance.com>

Author: jafingerhut

src/jvm/clojure/lang/APersistentVector.java

@@ -523,7 +523,7 @@ public SubVector(IPersistentMap meta, IPersistentVector v, int start, int end){
 	public Iterator iterator(){return ((PersistentVector)v).rangedIterator(start,end);}
 
 	public Object nth(int i){
-		if(start + i >= end)
+		if((start + i >= end) || (i < 0))
 			throw new IndexOutOfBoundsException();
 		return v.nth(start + i);
 	}

test/clojure/test_clojure/vectors.clj

@@ -370,3 +370,11 @@
   (are [r c1] (=vec r (filterv even? c1))
        [] [1 3 5]
        [2 4] [1 2 3 4 5]))
+
+(deftest test-subvec
+  (let [v1 (vec (range 100))
+        v2 (subvec v1 50 57)]
+    (is (thrown? IndexOutOfBoundsException (v2 -1)))
+    (is (thrown? IndexOutOfBoundsException (v2 7)))
+    (is (= (v1 50) (v2 0)))
+    (is (= (v1 56) (v2 6)))))