From ae533551c29fe4fd9f8dfa214400ff44a85124b9 Mon Sep 17 00:00:00 2001
From: Filipe Silva <filipematossilva@gmail.com>
Date: Sun, 9 Jul 2017 18:50:45 +0100
Subject: [PATCH] Allow visitors to return undefined

While implementing `ts.Visitor`, it is possible to return `undefined` in order to drop a node. However, the typings do not reflect this and only allow to return `Node | Node []`.

This PR extends the typings to allow `undefined` as well.
---
 src/compiler/types.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/compiler/types.ts b/src/compiler/types.ts
index 63b50d58e4a..da69c407ac8 100644
--- a/src/compiler/types.ts
+++ b/src/compiler/types.ts
@@ -4350,7 +4350,7 @@ namespace ts {
      */
     export type Visitor = (node: Node) => VisitResult<Node>;
 
-    export type VisitResult<T extends Node> = T | T[];
+    export type VisitResult<T extends Node> = T | T[] | undefined;
 
     export interface Printer {
         /**