From cbdf02f47c1af41a985c970d50c942d3c996dcdb Mon Sep 17 00:00:00 2001
From: Andy <anhans@microsoft.com>
Date: Mon, 5 Jun 2017 18:07:55 -0700
Subject: [PATCH] Undo change and go back to making a copy of leadingComments
 and trailingComments (#16273)

---
 src/compiler/factory.ts | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/src/compiler/factory.ts b/src/compiler/factory.ts
index a83f00ce86ebc..12e8110e7bec4 100644
--- a/src/compiler/factory.ts
+++ b/src/compiler/factory.ts
@@ -2503,8 +2503,9 @@ namespace ts {
             helpers
         } = sourceEmitNode;
         if (!destEmitNode) destEmitNode = {};
-        if (leadingComments) destEmitNode.leadingComments = concatenate(leadingComments, destEmitNode.leadingComments);
-        if (trailingComments) destEmitNode.trailingComments = concatenate(trailingComments, destEmitNode.trailingComments);
+        // We are using `.slice()` here in case `destEmitNode.leadingComments` is pushed to later.
+        if (leadingComments) destEmitNode.leadingComments = addRange(leadingComments.slice(), destEmitNode.leadingComments);
+        if (trailingComments) destEmitNode.trailingComments = addRange(trailingComments.slice(), destEmitNode.trailingComments);
         if (flags) destEmitNode.flags = flags;
         if (commentRange) destEmitNode.commentRange = commentRange;
         if (sourceMapRange) destEmitNode.sourceMapRange = sourceMapRange;