lib Fix Part 6/6 – Array.isArray

src/lib/es2015.iterable.d.ts

@@ -56,6 +56,20 @@ interface Array<T> {
 }
 
 interface ArrayConstructor {
+    isArray<T>(arg: T): arg is
+        T extends any ?
+            (
+                true extends false & T ? Extract<any[], T> :
+                T extends string | readonly any[] ? never :
+                T extends ArrayLike<infer U> | Iterable<infer U> ? Extract<U[], T> :
+                never
+            ) | (
+                true extends false & T ? never :
+                {} extends Required<T> ? T & any[] :
+                Extract<T, readonly any[]>
+            )
+         : never;
+
     /**
      * Creates an array from an iterable object.
      * @param iterable An iterable object to convert to an array.

src/lib/es5.d.ts

@@ -1471,7 +1471,19 @@ interface ArrayConstructor {
     (arrayLength?: number): any[];
     <T>(arrayLength: number): T[];
     <T>(...items: T[]): T[];
-    isArray(arg: any): arg is any[];
+    isArray<T>(arg: T): arg is
+        T extends any ?
+            (
+                true extends false & T ? Extract<any[], T> :
+                T extends string | readonly any[] ? never :
+                T extends ArrayLike<infer U> ? Extract<U[], T> :
+                never
+            ) | (
+                true extends false & T ? never :
+                {} extends Required<T> ? T & any[] :
+                Extract<T, readonly any[]>
+            )
+        : never;
     readonly prototype: any[];
 }
 

tests/baselines/reference/arrayDestructuringInSwitch1.types

@@ -11,9 +11,9 @@ export function evaluate(expression: Expression): boolean {
 
   if (Array.isArray(expression)) {
 >Array.isArray(expression) : boolean
->Array.isArray : (arg: any) => arg is any[]
+>Array.isArray : <T>(arg: T) => arg is T extends any ? (true extends false & T ? Extract<any[], T> : T extends string | readonly any[] ? never : T extends ArrayLike<infer U> ? Extract<U[], T> : never) | (true extends false & T ? never : {} extends Required<T> ? T & any[] : Extract<T, readonly any[]>) : never
 >Array : ArrayConstructor
->isArray : (arg: any) => arg is any[]
+>isArray : <T>(arg: T) => arg is T extends any ? (true extends false & T ? Extract<any[], T> : T extends string | readonly any[] ? never : T extends ArrayLike<infer U> ? Extract<U[], T> : never) | (true extends false & T ? never : {} extends Required<T> ? T & any[] : Extract<T, readonly any[]>) : never
 >expression : Expression
 
     const [operator, ...operands] = expression;

tests/baselines/reference/arrayTypeOfTypeOf.types

@@ -14,11 +14,11 @@ var xs2: typeof Array;
 >Array : ArrayConstructor
 
 var xs3: typeof Array<number>;
->xs3 : { (arrayLength: number): number[]; (...items: number[]): number[]; new (arrayLength: number): number[]; new (...items: number[]): number[]; isArray(arg: any): arg is any[]; readonly prototype: any[]; }
+>xs3 : { (arrayLength: number): number[]; (...items: number[]): number[]; new (arrayLength: number): number[]; new (...items: number[]): number[]; isArray<T>(arg: T): arg is T extends any ? (true extends false & T ? Extract<any[], T> : T extends string | readonly any[] ? never : T extends ArrayLike<infer U> ? Extract<U[], T> : never) | (true extends false & T ? never : {} extends Required<T> ? T & any[] : Extract<T, readonly any[]>) : never; readonly prototype: any[]; }
 >Array : ArrayConstructor
 
 var xs4: typeof Array<typeof x>;
->xs4 : { (arrayLength: number): number[]; (...items: number[]): number[]; new (arrayLength: number): number[]; new (...items: number[]): number[]; isArray(arg: any): arg is any[]; readonly prototype: any[]; }
+>xs4 : { (arrayLength: number): number[]; (...items: number[]): number[]; new (arrayLength: number): number[]; new (...items: number[]): number[]; isArray<T>(arg: T): arg is T extends any ? (true extends false & T ? Extract<any[], T> : T extends string | readonly any[] ? never : T extends ArrayLike<infer U> ? Extract<U[], T> : never) | (true extends false & T ? never : {} extends Required<T> ? T & any[] : Extract<T, readonly any[]>) : never; readonly prototype: any[]; }
 >Array : ArrayConstructor
 >x : number
 

tests/baselines/reference/declarationsWithRecursiveInternalTypesProduceUniqueTypeParams.symbols

@@ -79,9 +79,9 @@ export const updateIfChanged = <T>(t: T) => {
 >Object.assign : Symbol(ObjectConstructor.assign, Decl(lib.es2015.core.d.ts, --, --), Decl(lib.es2015.core.d.ts, --, --), Decl(lib.es2015.core.d.ts, --, --), Decl(lib.es2015.core.d.ts, --, --))
 >Object : Symbol(Object, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
 >assign : Symbol(ObjectConstructor.assign, Decl(lib.es2015.core.d.ts, --, --), Decl(lib.es2015.core.d.ts, --, --), Decl(lib.es2015.core.d.ts, --, --), Decl(lib.es2015.core.d.ts, --, --))
->Array.isArray : Symbol(ArrayConstructor.isArray, Decl(lib.es5.d.ts, --, --))
+>Array.isArray : Symbol(ArrayConstructor.isArray, Decl(lib.es5.d.ts, --, --), Decl(lib.es2015.iterable.d.ts, --, --))
 >Array : Symbol(Array, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --), Decl(lib.es2015.core.d.ts, --, --), Decl(lib.es2015.iterable.d.ts, --, --), Decl(lib.es2015.symbol.wellknown.d.ts, --, --))
->isArray : Symbol(ArrayConstructor.isArray, Decl(lib.es5.d.ts, --, --))
+>isArray : Symbol(ArrayConstructor.isArray, Decl(lib.es5.d.ts, --, --), Decl(lib.es2015.iterable.d.ts, --, --))
 >u : Symbol(u, Decl(declarationsWithRecursiveInternalTypesProduceUniqueTypeParams.ts, 7, 23))
 >u : Symbol(u, Decl(declarationsWithRecursiveInternalTypesProduceUniqueTypeParams.ts, 7, 23))
 >[key] : Symbol([key], Decl(declarationsWithRecursiveInternalTypesProduceUniqueTypeParams.ts, 12, 80))

tests/baselines/reference/declarationsWithRecursiveInternalTypesProduceUniqueTypeParams.types

@@ -67,9 +67,9 @@ export const updateIfChanged = <T>(t: T) => {
 >assign : { <T extends {}, U>(target: T, source: U): T & U; <T extends {}, U, V>(target: T, source1: U, source2: V): T & U & V; <T extends {}, U, V, W>(target: T, source1: U, source2: V, source3: W): T & U & V & W; (target: object, ...sources: any[]): any; }
 >Array.isArray(u) ? [] : {} : undefined[] | {}
 >Array.isArray(u) : boolean
->Array.isArray : (arg: any) => arg is any[]
+>Array.isArray : { <T>(arg: T): arg is T extends any ? (true extends false & T ? Extract<any[], T> : T extends string | readonly any[] ? never : T extends ArrayLike<infer U> ? Extract<U[], T> : never) | (true extends false & T ? never : {} extends Required<T> ? T & any[] : Extract<T, readonly any[]>) : never; <T>(arg: T): arg is T extends any ? (true extends false & T ? Extract<any[], T> : T extends string | readonly any[] ? never : T extends ArrayLike<infer U> | Iterable<infer U> ? Extract<U[], T> : never) | (true extends false & T ? never : {} extends Required<T> ? T & any[] : Extract<T, readonly any[]>) : never; }
 >Array : ArrayConstructor
->isArray : (arg: any) => arg is any[]
+>isArray : { <T>(arg: T): arg is T extends any ? (true extends false & T ? Extract<any[], T> : T extends string | readonly any[] ? never : T extends ArrayLike<infer U> ? Extract<U[], T> : never) | (true extends false & T ? never : {} extends Required<T> ? T & any[] : Extract<T, readonly any[]>) : never; <T>(arg: T): arg is T extends any ? (true extends false & T ? Extract<any[], T> : T extends string | readonly any[] ? never : T extends ArrayLike<infer U> | Iterable<infer U> ? Extract<U[], T> : never) | (true extends false & T ? never : {} extends Required<T> ? T & any[] : Extract<T, readonly any[]>) : never; }
 >u : U
 >[] : undefined[]
 >{} : {}

tests/baselines/reference/fixSignatureCaching.types

@@ -1109,9 +1109,9 @@ define(function () {
 >Array : ArrayConstructor
 
         Array.isArray : function (value) { return Object.prototype.toString.call(value) === '[object Array]'; };
->Array.isArray : (arg: any) => arg is any[]
+>Array.isArray : <T>(arg: T) => arg is T extends any ? (true extends false & T ? Extract<any[], T> : T extends string | readonly any[] ? never : T extends ArrayLike<infer U> ? Extract<U[], T> : never) | (true extends false & T ? never : {} extends Required<T> ? T & any[] : Extract<T, readonly any[]>) : never
 >Array : ArrayConstructor
->isArray : (arg: any) => arg is any[]
+>isArray : <T>(arg: T) => arg is T extends any ? (true extends false & T ? Extract<any[], T> : T extends string | readonly any[] ? never : T extends ArrayLike<infer U> ? Extract<U[], T> : never) | (true extends false & T ? never : {} extends Required<T> ? T & any[] : Extract<T, readonly any[]>) : never
 >function (value) { return Object.prototype.toString.call(value) === '[object Array]'; } : (value: any) => boolean
 >value : any
 >Object.prototype.toString.call(value) === '[object Array]' : boolean

tests/baselines/reference/instantiationExpressions.types

@@ -61,13 +61,13 @@ function f2() {
 >Array : ArrayConstructor
 
     const A1 = Array<string>;  // new (...) => string[]
->A1 : { (arrayLength: number): string[]; (...items: string[]): string[]; new (arrayLength: number): string[]; new (...items: string[]): string[]; isArray(arg: any): arg is any[]; readonly prototype: any[]; }
->Array<string> : { (arrayLength: number): string[]; (...items: string[]): string[]; new (arrayLength: number): string[]; new (...items: string[]): string[]; isArray(arg: any): arg is any[]; readonly prototype: any[]; }
+>A1 : { (arrayLength: number): string[]; (...items: string[]): string[]; new (arrayLength: number): string[]; new (...items: string[]): string[]; isArray<T>(arg: T): arg is T extends any ? (true extends false & T ? Extract<any[], T> : T extends string | readonly any[] ? never : T extends ArrayLike<infer U> ? Extract<U[], T> : never) | (true extends false & T ? never : {} extends Required<T> ? T & any[] : Extract<T, readonly any[]>) : never; readonly prototype: any[]; }
+>Array<string> : { (arrayLength: number): string[]; (...items: string[]): string[]; new (arrayLength: number): string[]; new (...items: string[]): string[]; isArray<T>(arg: T): arg is T extends any ? (true extends false & T ? Extract<any[], T> : T extends string | readonly any[] ? never : T extends ArrayLike<infer U> ? Extract<U[], T> : never) | (true extends false & T ? never : {} extends Required<T> ? T & any[] : Extract<T, readonly any[]>) : never; readonly prototype: any[]; }
 >Array : ArrayConstructor
 
     const A2 = Array<string, number>;  // Error
->A2 : { isArray(arg: any): arg is any[]; readonly prototype: any[]; }
->Array<string, number> : { isArray(arg: any): arg is any[]; readonly prototype: any[]; }
+>A2 : { isArray<T>(arg: T): arg is T extends any ? (true extends false & T ? Extract<any[], T> : T extends string | readonly any[] ? never : T extends ArrayLike<infer U> ? Extract<U[], T> : never) | (true extends false & T ? never : {} extends Required<T> ? T & any[] : Extract<T, readonly any[]>) : never; readonly prototype: any[]; }
+>Array<string, number> : { isArray<T>(arg: T): arg is T extends any ? (true extends false & T ? Extract<any[], T> : T extends string | readonly any[] ? never : T extends ArrayLike<infer U> ? Extract<U[], T> : never) | (true extends false & T ? never : {} extends Required<T> ? T & any[] : Extract<T, readonly any[]>) : never; readonly prototype: any[]; }
 >Array : ArrayConstructor
 }
 
@@ -76,11 +76,11 @@ type T20 = typeof Array<>;  // Error
 >Array : ArrayConstructor
 
 type T21 = typeof Array<string>;  // new (...) => string[]
->T21 : { (arrayLength: number): string[]; (...items: string[]): string[]; new (arrayLength: number): string[]; new (...items: string[]): string[]; isArray(arg: any): arg is any[]; readonly prototype: any[]; }
+>T21 : { (arrayLength: number): string[]; (...items: string[]): string[]; new (arrayLength: number): string[]; new (...items: string[]): string[]; isArray<T>(arg: T): arg is T extends any ? (true extends false & T ? Extract<any[], T> : T extends string | readonly any[] ? never : T extends ArrayLike<infer U> ? Extract<U[], T> : never) | (true extends false & T ? never : {} extends Required<T> ? T & any[] : Extract<T, readonly any[]>) : never; readonly prototype: any[]; }
 >Array : ArrayConstructor
 
 type T22 = typeof Array<string, number>;  // Error
->T22 : { isArray(arg: any): arg is any[]; readonly prototype: any[]; }
+>T22 : { isArray<T>(arg: T): arg is T extends any ? (true extends false & T ? Extract<any[], T> : T extends string | readonly any[] ? never : T extends ArrayLike<infer U> ? Extract<U[], T> : never) | (true extends false & T ? never : {} extends Required<T> ? T & any[] : Extract<T, readonly any[]>) : never; readonly prototype: any[]; }
 >Array : ArrayConstructor
 
 declare class C<T> {

tests/baselines/reference/isArray.types

@@ -5,9 +5,9 @@ var maybeArray: number | number[];
 
 if (Array.isArray(maybeArray)) {
 >Array.isArray(maybeArray) : boolean
->Array.isArray : (arg: any) => arg is any[]
+>Array.isArray : <T>(arg: T) => arg is T extends any ? (true extends false & T ? Extract<any[], T> : T extends string | readonly any[] ? never : T extends ArrayLike<infer U> ? Extract<U[], T> : never) | (true extends false & T ? never : {} extends Required<T> ? T & any[] : Extract<T, readonly any[]>) : never
 >Array : ArrayConstructor
->isArray : (arg: any) => arg is any[]
+>isArray : <T>(arg: T) => arg is T extends any ? (true extends false & T ? Extract<any[], T> : T extends string | readonly any[] ? never : T extends ArrayLike<infer U> ? Extract<U[], T> : never) | (true extends false & T ? never : {} extends Required<T> ? T & any[] : Extract<T, readonly any[]>) : never
 >maybeArray : number | number[]
 
     maybeArray.length; // OK

tests/baselines/reference/isArrayConformance.js

@@ -0,0 +1,107 @@
+//// [isArrayConformance.ts]
+function f1(a: any) {
+	if (Array.isArray(a)) {
+		a; // Expected: any[]
+	}
+}
+
+function f2(a: unknown) {
+	if (Array.isArray(a)) {
+		a; // Expected: any[]
+	}
+}
+
+function f3(a: string | readonly string[] | number[]) {
+	if (Array.isArray(a)) {
+		var b: readonly string[] | number[] = a; // OK
+		a[0]; // Expected: string | number
+	}
+}
+
+function f4<T extends string | readonly string[] | number[]>(a: T) {
+	if (Array.isArray(a)) {
+		var b: readonly string[] | number[] = a; // OK
+		a[0]; // Expected: string | number
+	}
+}
+
+// Repro from #41808
+
+function f5<T extends string | undefined | string[]>(a: T) {
+	if (Array.isArray(a)) {
+		a[0]; // Expected: string
+	}
+}
+
+function f6(a: (number[] | null | "loading")[]) {
+	a.filter(Array.isArray); // Expected: number[][]
+}
+
+function f7(a: {} | null) {
+	if (Array.isArray(a)) {
+		a; // Expected: any[]
+	}
+}
+
+function f8<T extends ArrayLike<number> | Iterable<boolean> | readonly string[] | null>(a: T) {
+	if (Array.isArray(a)) {
+		var b: readonly string[] | number[] | boolean[] = a; // OK
+		a[0]; // Expected: string | number | boolean
+	}
+}
+
+function f9(a: number | null) {
+	if (Array.isArray(a)) {
+		a; // Expected: never
+	}
+}
+
+
+//// [isArrayConformance.js]
+function f1(a) {
+    if (Array.isArray(a)) {
+        a; // Expected: any[]
+    }
+}
+function f2(a) {
+    if (Array.isArray(a)) {
+        a; // Expected: any[]
+    }
+}
+function f3(a) {
+    if (Array.isArray(a)) {
+        var b = a; // OK
+        a[0]; // Expected: string | number
+    }
+}
+function f4(a) {
+    if (Array.isArray(a)) {
+        var b = a; // OK
+        a[0]; // Expected: string | number
+    }
+}
+// Repro from #41808
+function f5(a) {
+    if (Array.isArray(a)) {
+        a[0]; // Expected: string
+    }
+}
+function f6(a) {
+    a.filter(Array.isArray); // Expected: number[][]
+}
+function f7(a) {
+    if (Array.isArray(a)) {
+        a; // Expected: any[]
+    }
+}
+function f8(a) {
+    if (Array.isArray(a)) {
+        var b = a; // OK
+        a[0]; // Expected: string | number | boolean
+    }
+}
+function f9(a) {
+    if (Array.isArray(a)) {
+        a; // Expected: never
+    }
+}