From 43d47de74dad468be328af32c6a2776f55b10bbc Mon Sep 17 00:00:00 2001
From: Nathan Shively-Sanders <nathansa@microsoft.com>
Date: Tue, 13 Jun 2017 13:59:38 -0700
Subject: [PATCH] Add parentheses around keyof in declaration emit

When needed. Use InElementType flag to determine this.
---
 src/compiler/checker.ts | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index b7dd84f7716..338dd72d52d 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -3233,9 +3233,15 @@ namespace ts {
                         writer.writeStringLiteral(literalTypeToString(<LiteralType>type));
                     }
                     else if (type.flags & TypeFlags.Index) {
+                        if (flags & TypeFormatFlags.InElementType) {
+                            writePunctuation(writer, SyntaxKind.OpenParenToken);
+                        }
                         writer.writeKeyword("keyof");
                         writeSpace(writer);
                         writeType((<IndexType>type).type, TypeFormatFlags.InElementType);
+                        if (flags & TypeFormatFlags.InElementType) {
+                            writePunctuation(writer, SyntaxKind.CloseParenToken);
+                        }
                     }
                     else if (type.flags & TypeFlags.IndexedAccess) {
                         writeType((<IndexedAccessType>type).objectType, TypeFormatFlags.InElementType);