From 46561980dd8d9eaedbf7cbf67965809c9aba8bbf Mon Sep 17 00:00:00 2001
From: Nathan Shively-Sanders <293473+sandersn@users.noreply.github.com>
Date: Wed, 15 Jul 2020 14:59:03 -0700
Subject: [PATCH 1/2] Redo in-narrowing for intersections

Still need to carve out an exception for globalThis
---
 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 ef279c287581a..3fa39912292ee 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -21430,7 +21430,7 @@ 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
     }
 }
 

From 67dc93682d926ca857297591e839010ee00c20ec Mon Sep 17 00:00:00 2001
From: Nathan Shively-Sanders <293473+sandersn@users.noreply.github.com>
Date: Fri, 17 Jul 2020 08:43:18 -0700
Subject: [PATCH 2/2] exempt globalThis from `in` narrowing

---
 src/compiler/checker.ts                       |  4 +++-
 .../reference/inKeywordTypeguard.errors.txt   |  7 +++++++
 .../baselines/reference/inKeywordTypeguard.js | 15 ++++++++++++++
 .../reference/inKeywordTypeguard.symbols      | 18 +++++++++++++++++
 .../reference/inKeywordTypeguard.types        | 20 +++++++++++++++++++
 tests/cases/compiler/inKeywordTypeguard.ts    |  7 +++++++
 6 files changed, 70 insertions(+), 1 deletion(-)

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 3fa39912292ee..5c2b2d8731ac9 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -21430,7 +21430,9 @@ namespace ts {
             }
 
             function narrowByInKeyword(type: Type, literal: LiteralExpression, assumeTrue: boolean) {
-                if (type.flags & (TypeFlags.Union | TypeFlags.Object | TypeFlags.Intersection) || isThisTypeParameter(type)) {
+                if (type.flags & (TypeFlags.Union | TypeFlags.Object)
+                    || isThisTypeParameter(type)
+                    || type.flags & TypeFlags.Intersection && every((type as IntersectionType).types, t => t.symbol !== globalThisSymbol)) {
                     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 f5885acfc8835..bb7d823d99d43 100644
--- a/tests/baselines/reference/inKeywordTypeguard.errors.txt
+++ b/tests/baselines/reference/inKeywordTypeguard.errors.txt
@@ -165,4 +165,11 @@ tests/cases/compiler/inKeywordTypeguard.ts(94,26): error TS2339: Property 'a' do
             let n: never = x;
         }
     }
+    function negativeIntersectionTest() {
+        if ("ontouchstart" in window) {
+            window.ontouchstart
+        } else {
+            window.ontouchstart
+        }
+    }
     
\ No newline at end of file
diff --git a/tests/baselines/reference/inKeywordTypeguard.js b/tests/baselines/reference/inKeywordTypeguard.js
index 83499d7f54e3d..d5a11599b64bb 100644
--- a/tests/baselines/reference/inKeywordTypeguard.js
+++ b/tests/baselines/reference/inKeywordTypeguard.js
@@ -104,6 +104,13 @@ function positiveIntersectionTest(x: { a: string } & { b: string }) {
         let n: never = x;
     }
 }
+function negativeIntersectionTest() {
+    if ("ontouchstart" in window) {
+        window.ontouchstart
+    } else {
+        window.ontouchstart
+    }
+}
 
 
 //// [inKeywordTypeguard.js]
@@ -245,3 +252,11 @@ function positiveIntersectionTest(x) {
         var n = x;
     }
 }
+function negativeIntersectionTest() {
+    if ("ontouchstart" in window) {
+        window.ontouchstart;
+    }
+    else {
+        window.ontouchstart;
+    }
+}
diff --git a/tests/baselines/reference/inKeywordTypeguard.symbols b/tests/baselines/reference/inKeywordTypeguard.symbols
index ff79a4aa54efb..5ef75cbe25544 100644
--- a/tests/baselines/reference/inKeywordTypeguard.symbols
+++ b/tests/baselines/reference/inKeywordTypeguard.symbols
@@ -261,4 +261,22 @@ function positiveIntersectionTest(x: { a: string } & { b: string }) {
 >x : Symbol(x, Decl(inKeywordTypeguard.ts, 98, 34))
     }
 }
+function negativeIntersectionTest() {
+>negativeIntersectionTest : Symbol(negativeIntersectionTest, Decl(inKeywordTypeguard.ts, 104, 1))
+
+    if ("ontouchstart" in window) {
+>window : Symbol(window, Decl(lib.dom.d.ts, --, --))
+
+        window.ontouchstart
+>window.ontouchstart : Symbol(ontouchstart, Decl(lib.dom.d.ts, --, --), Decl(lib.dom.d.ts, --, --))
+>window : Symbol(window, Decl(lib.dom.d.ts, --, --))
+>ontouchstart : Symbol(ontouchstart, Decl(lib.dom.d.ts, --, --), Decl(lib.dom.d.ts, --, --))
+
+    } else {
+        window.ontouchstart
+>window.ontouchstart : Symbol(ontouchstart, Decl(lib.dom.d.ts, --, --), Decl(lib.dom.d.ts, --, --))
+>window : Symbol(window, Decl(lib.dom.d.ts, --, --))
+>ontouchstart : Symbol(ontouchstart, Decl(lib.dom.d.ts, --, --), Decl(lib.dom.d.ts, --, --))
+    }
+}
 
diff --git a/tests/baselines/reference/inKeywordTypeguard.types b/tests/baselines/reference/inKeywordTypeguard.types
index bd77a8da45ede..c5b735a51d9c1 100644
--- a/tests/baselines/reference/inKeywordTypeguard.types
+++ b/tests/baselines/reference/inKeywordTypeguard.types
@@ -321,4 +321,24 @@ function positiveIntersectionTest(x: { a: string } & { b: string }) {
 >x : never
     }
 }
+function negativeIntersectionTest() {
+>negativeIntersectionTest : () => void
+
+    if ("ontouchstart" in window) {
+>"ontouchstart" in window : boolean
+>"ontouchstart" : "ontouchstart"
+>window : Window & typeof globalThis
+
+        window.ontouchstart
+>window.ontouchstart : ((this: GlobalEventHandlers, ev: TouchEvent) => any) & ((this: Window, ev: TouchEvent) => any)
+>window : Window & typeof globalThis
+>ontouchstart : ((this: GlobalEventHandlers, ev: TouchEvent) => any) & ((this: Window, ev: TouchEvent) => any)
+
+    } else {
+        window.ontouchstart
+>window.ontouchstart : ((this: GlobalEventHandlers, ev: TouchEvent) => any) & ((this: Window, ev: TouchEvent) => any)
+>window : Window & typeof globalThis
+>ontouchstart : ((this: GlobalEventHandlers, ev: TouchEvent) => any) & ((this: Window, ev: TouchEvent) => any)
+    }
+}
 
diff --git a/tests/cases/compiler/inKeywordTypeguard.ts b/tests/cases/compiler/inKeywordTypeguard.ts
index 620aa401b252e..d20404c949a86 100644
--- a/tests/cases/compiler/inKeywordTypeguard.ts
+++ b/tests/cases/compiler/inKeywordTypeguard.ts
@@ -103,3 +103,10 @@ function positiveIntersectionTest(x: { a: string } & { b: string }) {
         let n: never = x;
     }
 }
+function negativeIntersectionTest() {
+    if ("ontouchstart" in window) {
+        window.ontouchstart
+    } else {
+        window.ontouchstart
+    }
+}