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Add ReadonlyArray overload to Array.isArray #28916

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Add ReadonlyArray overload to Array.isArray #28916

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ef70c04
Add ReadonlyArray overload for Array.isArray()
ulrichb Dec 8, 2018
f02bdcb
Accept remaining baselines
ulrichb Dec 8, 2018
659e901
Merge remote-tracking branch 'origin/master' into IsArrayReadonlyArra…
ulrichb Jul 17, 2019
57fa898
Switch to alternative which uses conditional types instead of an over…
ulrichb Jul 17, 2019
93e902d
Use parameters instead of casting of test types
ulrichb Jul 17, 2019
5e54de0
Add additional negative tests
ulrichb Jul 17, 2019
88cd932
Fix leftover test type cast
ulrichb Jul 17, 2019
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2 changes: 1 addition & 1 deletion src/lib/es5.d.ts
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Expand Up @@ -1341,7 +1341,7 @@ interface ArrayConstructor {
(arrayLength?: number): any[];
<T>(arrayLength: number): T[];
<T>(...items: T[]): T[];
isArray(arg: any): arg is Array<any>;
isArray<T>(arg: T): arg is T extends ReadonlyArray<any> ? T : Array<any> extends T ? (T & any[]) : never;
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@laughinghan laughinghan Jan 10, 2020 •
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Suggested change
isArray<T>(arg: T): arg is T extends ReadonlyArray<any> ? T : Array<any> extends T ? (T & any[]) : never;
isArray<T>(arg: T): arg is Extract<any[], T> | Extract<[any], T> | (unknown extends T ? never : Extract<T, readonly any[]>) {
// the first two clauses, `Extract<any[], T>` and `Extract<[any], T>`,
// ensure that the type predicate will extract `B[]` out of `A | B[]`
// and `[B]` out of `A | [B]`, just like a the naive predicate `arg is any[]`
// would. The final clause is a special case if T is known to include
// a readonly array, to extract `readonly B[]` out of `A | readonly B[]`,
// and `readonly [B]` out of `A | readonly [B]`, but as a special exception
// it needs to ignore the case of T = any, because `any` is an ill-behaved
// type. See https://github.com/microsoft/TypeScript/pull/28916#issuecomment-573217751

readonly prototype: Array<any>;
}

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4 changes: 2 additions & 2 deletions ...s/baselines/reference/declarationsWithRecursiveInternalTypesProduceUniqueTypeParams.types
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Expand Up @@ -67,9 +67,9 @@ export const updateIfChanged = <T>(t: T) => {
>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; }
>Array.isArray(u) ? [] : {} : undefined[] | {}
>Array.isArray(u) : boolean
>Array.isArray : (arg: any) => arg is any[]
>Array.isArray : <T>(arg: T) => arg is T extends readonly any[] ? T : any[] extends T ? T & any[] : never
>Array : ArrayConstructor
>isArray : (arg: any) => arg is any[]
>isArray : <T>(arg: T) => arg is T extends readonly any[] ? T : any[] extends T ? T & any[] : never
>u : U
>[] : undefined[]
>{} : {}
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4 changes: 2 additions & 2 deletions tests/baselines/reference/fixSignatureCaching.types
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Expand Up @@ -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 readonly any[] ? T : any[] extends T ? T & any[] : never
>Array : ArrayConstructor
>isArray : (arg: any) => arg is any[]
>isArray : <T>(arg: T) => arg is T extends readonly any[] ? T : any[] extends T ? T & 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
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128 changes: 128 additions & 0 deletions tests/baselines/reference/isArray.errors.txt
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@@ -0,0 +1,128 @@
tests/cases/compiler/isArray.ts(21,33): error TS2339: Property 'push' does not exist on type 'readonly string[]'.
tests/cases/compiler/isArray.ts(22,33): error TS2339: Property 'push' does not exist on type 'readonly string[]'.
tests/cases/compiler/isArray.ts(28,38): error TS2345: Argument of type '10' is not assignable to parameter of type 'string'.
tests/cases/compiler/isArray.ts(36,33): error TS2339: Property 'push' does not exist on type 'readonly string[] | number[]'.
Property 'push' does not exist on type 'readonly string[]'.
tests/cases/compiler/isArray.ts(40,33): error TS2339: Property 'push' does not exist on type 'readonly string[] | number[]'.
Property 'push' does not exist on type 'readonly string[]'.
tests/cases/compiler/isArray.ts(44,38): error TS2345: Argument of type '10' is not assignable to parameter of type 'string'.
tests/cases/compiler/isArray.ts(50,33): error TS2339: Property 'push' does not exist on type 'MyReadOnlyArray<string>'.
tests/cases/compiler/isArray.ts(51,41): error TS2345: Argument of type '10' is not assignable to parameter of type 'string'.
tests/cases/compiler/isArray.ts(61,33): error TS2339: Property 'push' does not exist on type 'readonly T[]'.
tests/cases/compiler/isArray.ts(70,33): error TS2339: Property 'push' does not exist on type 'readonly [T]'.
tests/cases/compiler/isArray.ts(76,38): error TS2345: Argument of type '10' is not assignable to parameter of type 'string'.
tests/cases/compiler/isArray.ts(83,15): error TS2345: Argument of type '"str"' is not assignable to parameter of type 'string[]'.


==== tests/cases/compiler/isArray.ts (12 errors) ====
interface MyArray<T> extends Array<T> { manifest: any; }
interface MyReadOnlyArray<T> extends ReadonlyArray<T> { manifest: any; }

function fn1(arg: string | string[]) {
if (Array.isArray(arg)) arg.push(""); // Should OK
}

function fn2(arg: unknown) {
if (Array.isArray(arg)) arg.push(""); // Should OK
}

function fn3(arg: object) {
if (Array.isArray(arg)) arg.push(""); // Should OK
}

function fn4(arg: {}) {
if (Array.isArray(arg)) arg.push(""); // Should OK
}

function fn5(arg: string | ReadonlyArray<string>) {
if (Array.isArray(arg)) arg.push(10); // Should FAIL
~~~~
!!! error TS2339: Property 'push' does not exist on type 'readonly string[]'.
if (Array.isArray(arg)) arg.push(""); // Should FAIL
~~~~
!!! error TS2339: Property 'push' does not exist on type 'readonly string[]'.
if (Array.isArray(arg)) arg.indexOf(""); // Should OK
if (!Array.isArray(arg)) arg.toUpperCase(); // Should OK
}

function fn6(arg: string | string[]) {
if (Array.isArray(arg)) arg.push(10); // Should FAIL
~~
!!! error TS2345: Argument of type '10' is not assignable to parameter of type 'string'.
}

function fn7(arg: boolean | number[] | string[], stringAndNumber: string & number) {
if (Array.isArray(arg)) arg.push(stringAndNumber); // Should OK
}

function fn8(arg: string | number[] | readonly string[]) {
if (Array.isArray(arg)) arg.push(10); // Should FAIL
~~~~
!!! error TS2339: Property 'push' does not exist on type 'readonly string[] | number[]'.
!!! error TS2339: Property 'push' does not exist on type 'readonly string[]'.
}

function fn9(arg: string | number[] | readonly string[]) {
if (Array.isArray(arg)) arg.push(10); // Should FAIL
~~~~
!!! error TS2339: Property 'push' does not exist on type 'readonly string[] | number[]'.
!!! error TS2339: Property 'push' does not exist on type 'readonly string[]'.
}

function fn10(arg: string | MyArray<string>) {
if (Array.isArray(arg)) arg.push(10); // Should FAIL
~~
!!! error TS2345: Argument of type '10' is not assignable to parameter of type 'string'.
if (Array.isArray(arg)) arg.push(""); // Should OK
if (Array.isArray(arg)) arg.manifest; // Should OK
}

function fn11(arg: string | MyReadOnlyArray<string>) {
if (Array.isArray(arg)) arg.push(""); // Should FAIL
~~~~
!!! error TS2339: Property 'push' does not exist on type 'MyReadOnlyArray<string>'.
if (Array.isArray(arg)) arg.indexOf(10); // Should FAIL
~~
!!! error TS2345: Argument of type '10' is not assignable to parameter of type 'string'.
if (Array.isArray(arg)) arg.indexOf(""); // Should OK
if (Array.isArray(arg)) arg.manifest; // Should OK
}

function fn12<T>(arg: T | T[], t: T) {
if (Array.isArray(arg)) arg.push(t); // Should OK
}

function fn13<T>(arg: T | ReadonlyArray<T>, t: T) {
if (Array.isArray(arg)) arg.push(t); // Should fail
~~~~
!!! error TS2339: Property 'push' does not exist on type 'readonly T[]'.
if (Array.isArray(arg)) arg.indexOf(t); // OK
}

function fn14<T>(arg: T | [T], t: T) {
if (Array.isArray(arg)) arg.push(t); // Should OK
}

function fn15<T>(arg: T | readonly [T], t: T) {
if (Array.isArray(arg)) arg.push(t); // Should fail
~~~~
!!! error TS2339: Property 'push' does not exist on type 'readonly [T]'.
if (Array.isArray(arg)) arg.indexOf(t); // Should OK
}

function fn16<T extends string | string[]>(arg: T) {
if (Array.isArray(arg)) arg.push("10"); // Should OK
if (Array.isArray(arg)) arg.push(10); // Should fail
~~
!!! error TS2345: Argument of type '10' is not assignable to parameter of type 'string'.
}

function fn17() {
const s: Array<string | string[]> = [];
const arrs = s.filter(Array.isArray);
arrs.push(["one"]); // Should OK
arrs.push("str"); // Should fail
~~~~~
!!! error TS2345: Argument of type '"str"' is not assignable to parameter of type 'string[]'.
}

183 changes: 172 additions & 11 deletions tests/baselines/reference/isArray.js
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@@ -1,19 +1,180 @@
//// [isArray.ts]
var maybeArray: number | number[];
interface MyArray<T> extends Array<T> { manifest: any; }
interface MyReadOnlyArray<T> extends ReadonlyArray<T> { manifest: any; }

function fn1(arg: string | string[]) {
if (Array.isArray(arg)) arg.push(""); // Should OK
}

if (Array.isArray(maybeArray)) {
maybeArray.length; // OK
function fn2(arg: unknown) {
if (Array.isArray(arg)) arg.push(""); // Should OK
}
else {
maybeArray.toFixed(); // OK
}

function fn3(arg: object) {
if (Array.isArray(arg)) arg.push(""); // Should OK
}

function fn4(arg: {}) {
if (Array.isArray(arg)) arg.push(""); // Should OK
}

function fn5(arg: string | ReadonlyArray<string>) {
if (Array.isArray(arg)) arg.push(10); // Should FAIL
if (Array.isArray(arg)) arg.push(""); // Should FAIL
if (Array.isArray(arg)) arg.indexOf(""); // Should OK
if (!Array.isArray(arg)) arg.toUpperCase(); // Should OK
}

function fn6(arg: string | string[]) {
if (Array.isArray(arg)) arg.push(10); // Should FAIL
}

function fn7(arg: boolean | number[] | string[], stringAndNumber: string & number) {
if (Array.isArray(arg)) arg.push(stringAndNumber); // Should OK
}

function fn8(arg: string | number[] | readonly string[]) {
if (Array.isArray(arg)) arg.push(10); // Should FAIL
}

function fn9(arg: string | number[] | readonly string[]) {
if (Array.isArray(arg)) arg.push(10); // Should FAIL
}

function fn10(arg: string | MyArray<string>) {
if (Array.isArray(arg)) arg.push(10); // Should FAIL
if (Array.isArray(arg)) arg.push(""); // Should OK
if (Array.isArray(arg)) arg.manifest; // Should OK
}

function fn11(arg: string | MyReadOnlyArray<string>) {
if (Array.isArray(arg)) arg.push(""); // Should FAIL
if (Array.isArray(arg)) arg.indexOf(10); // Should FAIL
if (Array.isArray(arg)) arg.indexOf(""); // Should OK
if (Array.isArray(arg)) arg.manifest; // Should OK
}

function fn12<T>(arg: T | T[], t: T) {
if (Array.isArray(arg)) arg.push(t); // Should OK
}

function fn13<T>(arg: T | ReadonlyArray<T>, t: T) {
if (Array.isArray(arg)) arg.push(t); // Should fail
if (Array.isArray(arg)) arg.indexOf(t); // OK
}

function fn14<T>(arg: T | [T], t: T) {
if (Array.isArray(arg)) arg.push(t); // Should OK
}

function fn15<T>(arg: T | readonly [T], t: T) {
if (Array.isArray(arg)) arg.push(t); // Should fail
if (Array.isArray(arg)) arg.indexOf(t); // Should OK
}

function fn16<T extends string | string[]>(arg: T) {
if (Array.isArray(arg)) arg.push("10"); // Should OK
if (Array.isArray(arg)) arg.push(10); // Should fail
}

function fn17() {
const s: Array<string | string[]> = [];
const arrs = s.filter(Array.isArray);
arrs.push(["one"]); // Should OK
arrs.push("str"); // Should fail
}


//// [isArray.js]
var maybeArray;
if (Array.isArray(maybeArray)) {
maybeArray.length; // OK
function fn1(arg) {
if (Array.isArray(arg))
arg.push(""); // Should OK
}
function fn2(arg) {
if (Array.isArray(arg))
arg.push(""); // Should OK
}
function fn3(arg) {
if (Array.isArray(arg))
arg.push(""); // Should OK
}
function fn4(arg) {
if (Array.isArray(arg))
arg.push(""); // Should OK
}
function fn5(arg) {
if (Array.isArray(arg))
arg.push(10); // Should FAIL
if (Array.isArray(arg))
arg.push(""); // Should FAIL
if (Array.isArray(arg))
arg.indexOf(""); // Should OK
if (!Array.isArray(arg))
arg.toUpperCase(); // Should OK
}
function fn6(arg) {
if (Array.isArray(arg))
arg.push(10); // Should FAIL
}
function fn7(arg, stringAndNumber) {
if (Array.isArray(arg))
arg.push(stringAndNumber); // Should OK
}
function fn8(arg) {
if (Array.isArray(arg))
arg.push(10); // Should FAIL
}
function fn9(arg) {
if (Array.isArray(arg))
arg.push(10); // Should FAIL
}
function fn10(arg) {
if (Array.isArray(arg))
arg.push(10); // Should FAIL
if (Array.isArray(arg))
arg.push(""); // Should OK
if (Array.isArray(arg))
arg.manifest; // Should OK
}
function fn11(arg) {
if (Array.isArray(arg))
arg.push(""); // Should FAIL
if (Array.isArray(arg))
arg.indexOf(10); // Should FAIL
if (Array.isArray(arg))
arg.indexOf(""); // Should OK
if (Array.isArray(arg))
arg.manifest; // Should OK
}
function fn12(arg, t) {
if (Array.isArray(arg))
arg.push(t); // Should OK
}
function fn13(arg, t) {
if (Array.isArray(arg))
arg.push(t); // Should fail
if (Array.isArray(arg))
arg.indexOf(t); // OK
}
function fn14(arg, t) {
if (Array.isArray(arg))
arg.push(t); // Should OK
}
function fn15(arg, t) {
if (Array.isArray(arg))
arg.push(t); // Should fail
if (Array.isArray(arg))
arg.indexOf(t); // Should OK
}
function fn16(arg) {
if (Array.isArray(arg))
arg.push("10"); // Should OK
if (Array.isArray(arg))
arg.push(10); // Should fail
}
else {
maybeArray.toFixed(); // OK
function fn17() {
var s = [];
var arrs = s.filter(Array.isArray);
arrs.push(["one"]); // Should OK
arrs.push("str"); // Should fail
}
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