From aca7e2fa3bcb6b1ebe623e79578aaa7faf98a8b6 Mon Sep 17 00:00:00 2001
From: Anders Hejlsberg <andersh@microsoft.com>
Date: Tue, 8 Nov 2016 13:38:52 -0800
Subject: [PATCH] Don't include private/protected properties in keyof T

---
 src/compiler/checker.ts | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index d2d2e9f84d9..8ed8df17c68 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -5816,7 +5816,9 @@ namespace ts {
         }
 
         function getLiteralTypeFromPropertyName(prop: Symbol) {
-            return startsWith(prop.name, "__@") ? neverType : getLiteralTypeForText(TypeFlags.StringLiteral, unescapeIdentifier(prop.name));
+            return getDeclarationModifierFlagsFromSymbol(prop) & ModifierFlags.NonPublicAccessibilityModifier || startsWith(prop.name, "__@") ?
+                neverType :
+                getLiteralTypeForText(TypeFlags.StringLiteral, unescapeIdentifier(prop.name));
         }
 
         function getLiteralTypeFromPropertyNames(type: Type) {
@@ -7044,7 +7046,7 @@ namespace ts {
                             return result;
                         }
                     }
-                    else if (isGenericMappedType(target)) {
+                    if (isGenericMappedType(target)) {
                         // A type [P in S]: X is related to a type [P in T]: X if T is related to S.
                         if (isGenericMappedType(source) &&
                             isRelatedTo(getConstraintTypeFromMappedType(<MappedType>target), getConstraintTypeFromMappedType(<MappedType>source), /*reportErrors*/ false) &&