From 7ce2555896536a6c9e96a8b9fd17b6563137a876 Mon Sep 17 00:00:00 2001
From: Anna Henningsen <anna@addaleax.net>
Date: Sat, 19 Aug 2017 18:29:25 +0200
Subject: stream: fix Writable instanceof for subclasses

The current custom instanceof for `Writable` subclasses previously
returned false positives for instances of *other* subclasses of
`Writable` because it was inherited by these subclasses.

Fixes: https://github.com/nodejs/node/issues/14943
PR-URL: https://github.com/nodejs/node/pull/14945
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: Timothy Gu <timothygu99@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Evan Lucas <evanlucas@me.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
---
 lib/_stream_writable.js | 2 ++
 1 file changed, 2 insertions(+)

(limited to 'lib')

diff --git a/lib/_stream_writable.js b/lib/_stream_writable.js
index 6e0eaf45b5..7de77958d5 100644
--- a/lib/_stream_writable.js
+++ b/lib/_stream_writable.js
@@ -179,6 +179,8 @@ if (typeof Symbol === 'function' && Symbol.hasInstance) {
     value: function(object) {
       if (realHasInstance.call(this, object))
         return true;
+      if (this !== Writable)
+        return false;
 
       return object && object._writableState instanceof WritableState;
     }
-- 
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