From 255b65a06bd803c96f43a44d86209a33bc35c3f4 Mon Sep 17 00:00:00 2001
From: Daniel Rosenwasser <DanielRosenwasser@users.noreply.github.com>
Date: Mon, 27 Apr 2020 13:24:23 -0700
Subject: [PATCH] Revert "Revert #37106 (#38172)"

This reverts commit 84c83da3a9cc2050997a7fd53d650d648fb128f3.
---
 src/compiler/checker.ts                                 | 2 +-
 tests/baselines/reference/inKeywordTypeguard.errors.txt | 5 +----
 tests/baselines/reference/inKeywordTypeguard.types      | 2 +-
 3 files changed, 3 insertions(+), 6 deletions(-)

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 93276c42cb3a8..44ffbd066ec2c 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -20555,7 +20555,7 @@ namespace ts {
             }
 
             function narrowByInKeyword(type: Type, literal: LiteralExpression, assumeTrue: boolean) {
-                if (type.flags & (TypeFlags.Union | TypeFlags.Object) || isThisTypeParameter(type)) {
+                if (type.flags & (TypeFlags.Union | TypeFlags.Object | TypeFlags.Intersection) || isThisTypeParameter(type)) {
                     const propName = escapeLeadingUnderscores(literal.text);
                     return filterType(type, t => isTypePresencePossible(t, propName, assumeTrue));
                 }
diff --git a/tests/baselines/reference/inKeywordTypeguard.errors.txt b/tests/baselines/reference/inKeywordTypeguard.errors.txt
index 5aa04b170426c..f5885acfc8835 100644
--- a/tests/baselines/reference/inKeywordTypeguard.errors.txt
+++ b/tests/baselines/reference/inKeywordTypeguard.errors.txt
@@ -19,10 +19,9 @@ tests/cases/compiler/inKeywordTypeguard.ts(74,32): error TS2339: Property 'a' do
 tests/cases/compiler/inKeywordTypeguard.ts(82,39): error TS2339: Property 'b' does not exist on type 'A'.
 tests/cases/compiler/inKeywordTypeguard.ts(84,39): error TS2339: Property 'a' does not exist on type 'B'.
 tests/cases/compiler/inKeywordTypeguard.ts(94,26): error TS2339: Property 'a' does not exist on type 'never'.
-tests/cases/compiler/inKeywordTypeguard.ts(103,13): error TS2322: Type '{ a: string; } & { b: string; }' is not assignable to type 'never'.
 
 
-==== tests/cases/compiler/inKeywordTypeguard.ts (18 errors) ====
+==== tests/cases/compiler/inKeywordTypeguard.ts (17 errors) ====
     class A { a: string; }
     class B { b: string; }
     
@@ -164,8 +163,6 @@ tests/cases/compiler/inKeywordTypeguard.ts(103,13): error TS2322: Type '{ a: str
             let s: string = x.a;
         } else {
             let n: never = x;
-                ~
-!!! error TS2322: Type '{ a: string; } & { b: string; }' is not assignable to type 'never'.
         }
     }
     
\ No newline at end of file
diff --git a/tests/baselines/reference/inKeywordTypeguard.types b/tests/baselines/reference/inKeywordTypeguard.types
index b15ab47d454e2..bd77a8da45ede 100644
--- a/tests/baselines/reference/inKeywordTypeguard.types
+++ b/tests/baselines/reference/inKeywordTypeguard.types
@@ -318,7 +318,7 @@ function positiveIntersectionTest(x: { a: string } & { b: string }) {
     } else {
         let n: never = x;
 >n : never
->x : { a: string; } & { b: string; }
+>x : never
     }
 }