applied pull request with thanks https://github.com/JetBrains/kotlin/pull/46

libraries/stdlib/src/kotlin/JUtil.kt

@@ -172,6 +172,14 @@ val <T> List<T>.last : T?
       return if (s > 0) this.get(s - 1) else null
     }
 
+/**
+ * Returns the index of the last item in the list or -1 if the list is empty
+ *
+ * @includeFunctionBody ../../test/ListTest.kt lastIndex
+ */
+val <T> List<T>.lastIndex : Int
+    get() = this.size - 1
+
 /**
  * Returns the first item in the list
  *