From 9ff01674288d3121c8fbfd28266558989e36df70 Mon Sep 17 00:00:00 2001
From: Andy Hanson <anhans@microsoft.com>
Date: Wed, 6 Dec 2017 14:11:12 -0800
Subject: [PATCH] In createNodeArray, create a fresh array

---
 src/compiler/factory.ts | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/src/compiler/factory.ts b/src/compiler/factory.ts
index ec19d2c906c12..53a4940e61c4c 100644
--- a/src/compiler/factory.ts
+++ b/src/compiler/factory.ts
@@ -21,11 +21,15 @@ namespace ts {
      * Make `elements` into a `NodeArray<T>`. If `elements` is `undefined`, returns an empty `NodeArray<T>`.
      */
     export function createNodeArray<T extends Node>(elements?: ReadonlyArray<T>, hasTrailingComma?: boolean): NodeArray<T> {
-        if (!elements || elements === emptyArray) {
-            elements = [];
+        if (elements) {
+            if (isNodeArray(elements)) {
+                return elements;
+            }
+            // elements is a ReadonlyArray, so create a fresh array before adding properties.
+            elements = elements.slice();
         }
-        else if (isNodeArray(elements)) {
-            return elements;
+        else {
+            elements = [];
         }
 
         const array = <NodeArray<T>>elements;