Revert "Revert #37106 (#38172)"

DanielRosenwasser · web-flow · commit 255b65a06bd8 · 2020-04-27T13:24:23.000-07:00
This reverts commit 84c83da.
diff --git 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
@@ -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'.
         }
     }
     
diff --git 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
     }
 }
 

Original file line number	Diff line number	Diff line change
`@@ -20555,7 +20555,7 @@ namespace ts {`
`20555`	`20555`	`}`
`20556`	`20556`
`20557`	`20557`	`function narrowByInKeyword(type: Type, literal: LiteralExpression, assumeTrue: boolean) {`
`20558`		`- if (type.flags & (TypeFlags.Union \| TypeFlags.Object) \|\| isThisTypeParameter(type)) {`
	`20558`	`+ if (type.flags & (TypeFlags.Union \| TypeFlags.Object \| TypeFlags.Intersection) \|\| isThisTypeParameter(type)) {`
`20559`	`20559`	`const propName = escapeLeadingUnderscores(literal.text);`
`20560`	`20560`	`return filterType(type, t => isTypePresencePossible(t, propName, assumeTrue));`
`20561`	`20561`	`}`
Original file line number	Diff line number	Diff line change
`@@ -318,7 +318,7 @@ function positiveIntersectionTest(x: { a: string } & { b: string }) {`
`318`	`318`	`} else {`
`319`	`319`	`let n: never = x;`
`320`	`320`	`>n : never`
`321`		`->x : { a: string; } & { b: string; }`
	`321`	`+>x : never`
`322`	`322`	`}`
`323`	`323`	`}`
`324`	`324`