Fix 21732: "in" operator could widden type

src/compiler/checker.ts

@@ -21459,12 +21459,99 @@ namespace ts {
                 return !assumeTrue;
             }
 
-            function narrowByInKeyword(type: Type, literal: LiteralExpression, assumeTrue: boolean) {
-                if (type.flags & (TypeFlags.Union | TypeFlags.Object) || isThisTypeParameter(type)) {
-                    const propName = escapeLeadingUnderscores(literal.text);
+            function widdenTypeWithSymbol(type: Type, newSymbol: Symbol): Type {
+                // If type is this/any/unknown, it could not be widden.
+                if ((type.flags & TypeFlags.AnyOrUnknown) || isThisTypeParameter(type)) {
+                    return type;
+                }
+                const propName = newSymbol.escapedName;
+                // if type is intersection, we might have added type into it, and we just need to add into this type again rather than a new one.
+                // else add a new anonymous object type which contains the type and widden the origional type with it.
+                if (isIntersectionType(type)) {
+                    // try to get the first Anonymous Object type to add new type to it.
+                    const firstAnonymousObjectType: Type | undefined = type.types.find(t => isObjectType(t) && t.objectFlags & ObjectFlags.Anonymous);
+                    if (firstAnonymousObjectType && isObjectType(firstAnonymousObjectType)) {
+                        const members = createSymbolTable();
+                        members.set(propName, newSymbol);
+                        if (firstAnonymousObjectType.members) {
+                            mergeSymbolTable(members, firstAnonymousObjectType.members);
+                        }
+                        firstAnonymousObjectType.members = members;
+                        firstAnonymousObjectType.properties = getNamedMembers(members);
+                    }
+                    else {
+                        const members = createSymbolTable();
+                        members.set(propName, newSymbol);
+                        const newObjType = createAnonymousType(undefined, members, emptyArray, emptyArray, undefined, undefined);
+                        return createIntersectionType([type, newObjType]);
+                    }
+                }
+                else {
+                    const members = createSymbolTable();
+                    members.set(propName, newSymbol);
+                    const newObjType = createAnonymousType(undefined, members, emptyArray, emptyArray, undefined, undefined);
+                    // if `type` is never, just return the new anonymous object type.
+                    if (type.flags & TypeFlags.Never) {
+                        return newObjType;
+                    }
+                    return createIntersectionType([type, newObjType]);
+                }
+                return type;
+
+                // I would be very glad to create a helper file like `nodeTests.ts` if feedback positive review.
+                function isIntersectionType(type: Type): type is IntersectionType {
+                    return !!(type.flags & TypeFlags.Intersection);
+                }
+                function isObjectType(type: Type): type is ObjectType {
+                    return !!(type.flags & TypeFlags.Object);
+                }
+            }
+
+            function narrowOrWiddenTypeByInKeyword(type: Type, literal: LiteralExpression, assumeTrue: boolean) {
+                const propName = escapeLeadingUnderscores(literal.text);
+                const addSymbol = createSymbol(SymbolFlags.Property, propName);
+                addSymbol.type = unknownType;
+
+                if ((type.flags & (TypeFlags.Union | TypeFlags.Object) || isThisTypeParameter(type)) && isSomeDirectSubtypeContainsPropName(type, propName)) {
                     return filterType(type, t => isTypePresencePossible(t, propName, assumeTrue));
                 }
+                // only widden property when the type does not contain string-index/propName in any of the constituents.
+                else if (assumeTrue && !isSomeDirectSubtypeContainsPropName(type, propName) && !getIndexInfoOfType(type, IndexKind.String)) {
+                    return widdenTypeWithSymbol(type, addSymbol);
+                }
                 return type;
+
+                // This function is almost like function `getPropertyOfType`, except when type.flags contains `UnionOrIntersection`
+                // it would return the property rather than undefiend even when property is partial.
+                function isSomeDirectSubtypeContainsPropName(type1: Type, name: __String) {
+                    let prop;
+                    const type = getReducedApparentType(type1);
+                    if (type.flags & TypeFlags.Object) {
+                        const resolved = resolveStructuredTypeMembers(<ObjectType>type);
+                        const symbol = resolved.members.get(name);
+                        if (symbol && symbolIsValue(symbol)) {
+                            prop = symbol;
+                        }
+                        const functionType = resolved === anyFunctionType ? globalFunctionType :
+                            resolved.callSignatures.length ? globalCallableFunctionType :
+                                resolved.constructSignatures.length ? globalNewableFunctionType :
+                                    undefined;
+                        if (functionType) {
+                            const symbol = getPropertyOfObjectType(functionType, name);
+                            if (symbol) {
+                                prop = symbol;
+                            }
+                        }
+                        return getPropertyOfObjectType(globalObjectType, name);
+                    }
+                    if (type.flags & TypeFlags.UnionOrIntersection) {
+                        prop = getUnionOrIntersectionProperty(<UnionOrIntersectionType>type, name);
+                    }
+                    if (prop) {
+                        return true;
+                    }
+                    return false;
+                }
             }
 
             function narrowTypeByBinaryExpression(type: Type, expr: BinaryExpression, assumeTrue: boolean): Type {
@@ -21519,7 +21606,7 @@ namespace ts {
                     case SyntaxKind.InKeyword:
                         const target = getReferenceCandidate(expr.right);
                         if (isStringLiteralLike(expr.left) && isMatchingReference(reference, target)) {
-                            return narrowByInKeyword(type, expr.left, assumeTrue);
+                            return narrowOrWiddenTypeByInKeyword(type, expr.left, assumeTrue);
                         }
                         break;
                     case SyntaxKind.CommaToken:

tests/baselines/reference/conditionalTypeDoesntSpinForever.types

@@ -212,12 +212,12 @@ export enum PubSubRecordIsStoredInRedisAsA {
 >buildPubSubRecordType(Object.assign({}, soFar, {identifier: instance as TYPE}) as SO_FAR & {identifier: TYPE}) : BuildPubSubRecordType<SO_FAR & { identifier: TYPE; }>
 >buildPubSubRecordType : <SO_FAR>(soFar: SO_FAR) => BuildPubSubRecordType<SO_FAR>
 >Object.assign({}, soFar, {identifier: instance as TYPE}) as SO_FAR & {identifier: TYPE} : SO_FAR & { identifier: TYPE; }
->Object.assign({}, soFar, {identifier: instance as TYPE}) : SO_FAR & { identifier: TYPE; }
+>Object.assign({}, soFar, {identifier: instance as TYPE}) : SO_FAR & { record: unknown; } & { identifier: TYPE; }
 >Object.assign : { <T, U>(target: T, source: U): T & U; <T, U, V>(target: T, source1: U, source2: V): T & U & V; <T, U, V, W>(target: T, source1: U, source2: V, source3: W): T & U & V & W; (target: object, ...sources: any[]): any; }
 >Object : ObjectConstructor
 >assign : { <T, U>(target: T, source: U): T & U; <T, U, V>(target: T, source1: U, source2: V): T & U & V; <T, U, V, W>(target: T, source1: U, source2: V, source3: W): T & U & V & W; (target: object, ...sources: any[]): any; }
 >{} : {}
->soFar : SO_FAR
+>soFar : SO_FAR & { record: unknown; }
 >{identifier: instance as TYPE} : { identifier: TYPE; }
 >identifier : TYPE
 >instance as TYPE : TYPE
@@ -389,13 +389,13 @@ export enum PubSubRecordIsStoredInRedisAsA {
 >soFar : SO_FAR
 >"object" in soFar : boolean
 >"object" : "object"
->soFar : SO_FAR
+>soFar : SO_FAR & { identifier: unknown; }
 >"maxMsToWaitBeforePublishing" in soFar : boolean
 >"maxMsToWaitBeforePublishing" : "maxMsToWaitBeforePublishing"
->soFar : SO_FAR
+>soFar : SO_FAR & { object: unknown; identifier: unknown; }
 >"PubSubRecordIsStoredInRedisAsA" in soFar : boolean
 >"PubSubRecordIsStoredInRedisAsA" : "PubSubRecordIsStoredInRedisAsA"
->soFar : SO_FAR
+>soFar : SO_FAR & { maxMsToWaitBeforePublishing: unknown; object: unknown; identifier: unknown; }
 >{} : {}
 >{      type: soFar,      fields: () => new Set(Object.keys(soFar) as (keyof SO_FAR)[]),      hasField: (fieldName: string | number | symbol) => fieldName in soFar    } : { type: SO_FAR; fields: () => Set<keyof SO_FAR>; hasField: (fieldName: string | number | symbol) => boolean; }
 

tests/baselines/reference/fixSignatureCaching.errors.txt

@@ -3,7 +3,6 @@ tests/cases/conformance/fixSignatureCaching.ts(284,10): error TS2339: Property '
 tests/cases/conformance/fixSignatureCaching.ts(293,10): error TS2339: Property 'FALLBACK_PHONE' does not exist on type '{}'.
 tests/cases/conformance/fixSignatureCaching.ts(294,10): error TS2339: Property 'FALLBACK_TABLET' does not exist on type '{}'.
 tests/cases/conformance/fixSignatureCaching.ts(295,10): error TS2339: Property 'FALLBACK_MOBILE' does not exist on type '{}'.
-tests/cases/conformance/fixSignatureCaching.ts(301,17): error TS2339: Property 'isArray' does not exist on type 'never'.
 tests/cases/conformance/fixSignatureCaching.ts(330,74): error TS2339: Property 'mobileDetectRules' does not exist on type '{}'.
 tests/cases/conformance/fixSignatureCaching.ts(369,10): error TS2339: Property 'findMatch' does not exist on type '{}'.
 tests/cases/conformance/fixSignatureCaching.ts(387,10): error TS2339: Property 'findMatches' does not exist on type '{}'.
@@ -59,7 +58,7 @@ tests/cases/conformance/fixSignatureCaching.ts(981,16): error TS2304: Cannot fin
 tests/cases/conformance/fixSignatureCaching.ts(983,44): error TS2339: Property 'MobileDetect' does not exist on type 'Window & typeof globalThis'.
 
 
-==== tests/cases/conformance/fixSignatureCaching.ts (59 errors) ====
+==== tests/cases/conformance/fixSignatureCaching.ts (58 errors) ====
     // Repro from #10697
 
     (function (define, undefined) {
@@ -371,8 +370,6 @@ tests/cases/conformance/fixSignatureCaching.ts(983,44): error TS2339: Property '
         isArray = 'isArray' in Array
             ? function (value) { return Object.prototype.toString.call(value) === '[object Array]'; }
             : Array.isArray;
-                    ~~~~~~~
-!!! error TS2339: Property 'isArray' does not exist on type 'never'.
 
         function equalIC(a, b) {
             return a != null && b != null && a.toLowerCase() === b.toLowerCase();

tests/baselines/reference/fixSignatureCaching.symbols

@@ -825,7 +825,9 @@ define(function () {
 >value : Symbol(value, Decl(fixSignatureCaching.ts, 299, 20))
 
         : Array.isArray;
+>Array.isArray : Symbol(ArrayConstructor.isArray, Decl(lib.es5.d.ts, --, --))
 >Array : Symbol(Array, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+>isArray : Symbol(ArrayConstructor.isArray, Decl(lib.es5.d.ts, --, --))
 
     function equalIC(a, b) {
 >equalIC : Symbol(equalIC, Decl(fixSignatureCaching.ts, 300, 24))

tests/baselines/reference/fixSignatureCaching.types

@@ -1110,7 +1110,7 @@ define(function () {
 
         Array.isArray : function (value) { return Object.prototype.toString.call(value) === '[object Array]'; };
 >Array.isArray : (arg: any) => arg is any[]
->Array : ArrayConstructor
+>Array : ArrayConstructor & { isArray: unknown; }
 >isArray : (arg: any) => arg is any[]
 >function (value) { return Object.prototype.toString.call(value) === '[object Array]'; } : (value: any) => boolean
 >value : any
@@ -1127,9 +1127,9 @@ define(function () {
 >'[object Array]' : "[object Array]"
 
     isArray = 'isArray' in Array
->isArray = 'isArray' in Array        ? function (value) { return Object.prototype.toString.call(value) === '[object Array]'; }        : Array.isArray : any
+>isArray = 'isArray' in Array        ? function (value) { return Object.prototype.toString.call(value) === '[object Array]'; }        : Array.isArray : (value: any) => boolean
 >isArray : any
->'isArray' in Array        ? function (value) { return Object.prototype.toString.call(value) === '[object Array]'; }        : Array.isArray : any
+>'isArray' in Array        ? function (value) { return Object.prototype.toString.call(value) === '[object Array]'; }        : Array.isArray : (value: any) => boolean
 >'isArray' in Array : boolean
 >'isArray' : "isArray"
 >Array : ArrayConstructor
@@ -1150,9 +1150,9 @@ define(function () {
 >'[object Array]' : "[object Array]"
 
         : Array.isArray;
->Array.isArray : any
->Array : never
->isArray : any
+>Array.isArray : (arg: any) => arg is any[]
+>Array : ArrayConstructor
+>isArray : (arg: any) => arg is any[]
 
     function equalIC(a, b) {
 >equalIC : (a: any, b: any) => boolean

tests/baselines/reference/inKeywordTypeguard.errors.txt

@@ -5,8 +5,8 @@ tests/cases/compiler/inKeywordTypeguard.ts(16,11): error TS2339: Property 'a' do
 tests/cases/compiler/inKeywordTypeguard.ts(27,11): error TS2339: Property 'b' does not exist on type 'AWithOptionalProp | BWithOptionalProp'.
   Property 'b' does not exist on type 'AWithOptionalProp'.
 tests/cases/compiler/inKeywordTypeguard.ts(42,11): error TS2339: Property 'b' does not exist on type 'AWithMethod'.
-tests/cases/compiler/inKeywordTypeguard.ts(49,11): error TS2339: Property 'a' does not exist on type 'never'.
-tests/cases/compiler/inKeywordTypeguard.ts(50,11): error TS2339: Property 'b' does not exist on type 'never'.
+tests/cases/compiler/inKeywordTypeguard.ts(49,11): error TS2339: Property 'a' does not exist on type '(AWithMethod | BWithMethod) & { c: unknown; }'.
+tests/cases/compiler/inKeywordTypeguard.ts(50,11): error TS2339: Property 'b' does not exist on type '(AWithMethod | BWithMethod) & { c: unknown; }'.
 tests/cases/compiler/inKeywordTypeguard.ts(52,11): error TS2339: Property 'a' does not exist on type 'AWithMethod | BWithMethod'.
   Property 'a' does not exist on type 'BWithMethod'.
 tests/cases/compiler/inKeywordTypeguard.ts(53,11): error TS2339: Property 'b' does not exist on type 'AWithMethod | BWithMethod'.
@@ -18,11 +18,10 @@ tests/cases/compiler/inKeywordTypeguard.ts(72,32): error TS2339: Property 'b' do
 tests/cases/compiler/inKeywordTypeguard.ts(74,32): error TS2339: Property 'a' does not exist on type 'B'.
 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; }
 
@@ -86,10 +85,10 @@ tests/cases/compiler/inKeywordTypeguard.ts(103,13): error TS2322: Type '{ a: str
         if ("c" in x) {
             x.a();
               ~
-!!! error TS2339: Property 'a' does not exist on type 'never'.
+!!! error TS2339: Property 'a' does not exist on type '(AWithMethod | BWithMethod) & { c: unknown; }'.
             x.b();
               ~
-!!! error TS2339: Property 'b' does not exist on type 'never'.
+!!! error TS2339: Property 'b' does not exist on type '(AWithMethod | BWithMethod) & { c: unknown; }'.
         } else {
             x.a();
               ~
@@ -153,8 +152,6 @@ tests/cases/compiler/inKeywordTypeguard.ts(103,13): error TS2322: Type '{ a: str
             if ("a" in this) {
             } else {
                 let y = this.a;
-                             ~
-!!! error TS2339: Property 'a' does not exist on type 'never'.
             }
         }
     }

tests/baselines/reference/inKeywordTypeguard.symbols

@@ -236,6 +236,9 @@ class UnreachableCodeDetection {
         } else {
             let y = this.a;
 >y : Symbol(y, Decl(inKeywordTypeguard.ts, 93, 15))
+>this.a : Symbol(UnreachableCodeDetection.a, Decl(inKeywordTypeguard.ts, 88, 32))
+>this : Symbol(UnreachableCodeDetection, Decl(inKeywordTypeguard.ts, 86, 1))
+>a : Symbol(UnreachableCodeDetection.a, Decl(inKeywordTypeguard.ts, 88, 32))
         }
     }
 }

tests/baselines/reference/inKeywordTypeguard.types

@@ -146,13 +146,13 @@ function negativeTestClassesWithMemberMissingInBothClasses(x: AWithMethod | BWit
         x.a();
 >x.a() : any
 >x.a : any
->x : never
+>x : (AWithMethod | BWithMethod) & { c: unknown; }
 >a : any
 
         x.b();
 >x.b() : any
 >x.b : any
->x : never
+>x : (AWithMethod | BWithMethod) & { c: unknown; }
 >b : any
 
     } else {
@@ -290,10 +290,10 @@ class UnreachableCodeDetection {
 
         } else {
             let y = this.a;
->y : any
->this.a : any
->this : never
->a : any
+>y : string
+>this.a : string
+>this : this
+>a : string
         }
     }
 }