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Better typings for Array.concat(), etc. #33645

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6818576
Update baselines
jablko Feb 21, 2020
678ab4c
Better typings for Array.concat(), etc.
jablko Sep 27, 2019
6b0d950
Add tests
jablko Sep 26, 2019
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1 change: 1 addition & 0 deletions src/harness/fourslashInterfaceImpl.ts
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Expand Up @@ -954,6 +954,7 @@ namespace FourSlashInterface {
varEntry("JSON"),
interfaceEntry("ReadonlyArray"),
interfaceEntry("ConcatArray"),
typeEntry("Flatten"),
varEntry("Array"),
interfaceEntry("ArrayConstructor"),
interfaceEntry("TypedPropertyDescriptor"),
Expand Down
182 changes: 20 additions & 162 deletions src/lib/es2019.array.d.ts
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Expand Up @@ -10,106 +10,23 @@ interface ReadonlyArray<T> {
* @param thisArg An object to which the this keyword can refer in the callback function. If
* thisArg is omitted, undefined is used as the this value.
*/
flatMap<U, This = undefined> (
callback: (this: This, value: T, index: number, array: T[]) => U | ReadonlyArray<U>,
thisArg?: This
): U[]


/**
* Returns a new array with all sub-array elements concatenated into it recursively up to the
* specified depth.
*
* @param depth The maximum recursion depth
*/
flat<U>(this:
ReadonlyArray<U[][][][]> |

ReadonlyArray<ReadonlyArray<U[][][]>> |
ReadonlyArray<ReadonlyArray<U[][]>[]> |
ReadonlyArray<ReadonlyArray<U[]>[][]> |
ReadonlyArray<ReadonlyArray<U>[][][]> |

ReadonlyArray<ReadonlyArray<ReadonlyArray<U[][]>>> |
ReadonlyArray<ReadonlyArray<ReadonlyArray<U>[][]>> |
ReadonlyArray<ReadonlyArray<ReadonlyArray<U>>[][]> |
ReadonlyArray<ReadonlyArray<ReadonlyArray<U>[]>[]> |
ReadonlyArray<ReadonlyArray<ReadonlyArray<U[]>>[]> |
ReadonlyArray<ReadonlyArray<ReadonlyArray<U[]>[]>> |

ReadonlyArray<ReadonlyArray<ReadonlyArray<ReadonlyArray<U[]>>>> |
ReadonlyArray<ReadonlyArray<ReadonlyArray<ReadonlyArray<U>[]>>> |
ReadonlyArray<ReadonlyArray<ReadonlyArray<ReadonlyArray<U>>[]>> |
ReadonlyArray<ReadonlyArray<ReadonlyArray<ReadonlyArray<U>>>[]> |

ReadonlyArray<ReadonlyArray<ReadonlyArray<ReadonlyArray<ReadonlyArray<U>>>>>,
depth: 4): U[];

/**
* Returns a new array with all sub-array elements concatenated into it recursively up to the
* specified depth.
*
* @param depth The maximum recursion depth
*/
flat<U>(this:
ReadonlyArray<U[][][]> |

ReadonlyArray<ReadonlyArray<U>[][]> |
ReadonlyArray<ReadonlyArray<U[]>[]> |
ReadonlyArray<ReadonlyArray<U[][]>> |

ReadonlyArray<ReadonlyArray<ReadonlyArray<U[]>>> |
ReadonlyArray<ReadonlyArray<ReadonlyArray<U>[]>> |
ReadonlyArray<ReadonlyArray<ReadonlyArray<U>>[]> |

ReadonlyArray<ReadonlyArray<ReadonlyArray<ReadonlyArray<U>>>>,
depth: 3): U[];

/**
* Returns a new array with all sub-array elements concatenated into it recursively up to the
* specified depth.
*
* @param depth The maximum recursion depth
*/
flat<U>(this:
ReadonlyArray<U[][]> |

ReadonlyArray<ReadonlyArray<U[]>> |
ReadonlyArray<ReadonlyArray<U>[]> |

ReadonlyArray<ReadonlyArray<ReadonlyArray<U>>>,
depth: 2): U[];

/**
* Returns a new array with all sub-array elements concatenated into it recursively up to the
* specified depth.
*
* @param depth The maximum recursion depth
*/
flat<U>(this:
ReadonlyArray<U[]> |
ReadonlyArray<ReadonlyArray<U>>,
depth?: 1
): U[];
flatMap<U> (
callbackfn: (value: T, index: number, array: readonly T[]) => U,
thisArg?: any
): Flatten<U>[];

/**
* Returns a new array with all sub-array elements concatenated into it recursively up to the
* specified depth.
*
* @param depth The maximum recursion depth
*/
flat<U>(this:
ReadonlyArray<U>,
depth: 0
): U[];

/**
* Returns a new array with all sub-array elements concatenated into it recursively up to the
* specified depth. If no depth is provided, flat method defaults to the depth of 1.
*
* @param depth The maximum recursion depth
*/
flat<U>(depth?: number): any[];
flat(depth: 4): Flatten<Flatten<Flatten<Flatten<T>>>>[];
flat(depth: 3): Flatten<Flatten<Flatten<T>>>[];
flat(depth: 2): Flatten<Flatten<T>>[];
flat(depth?: 1): Flatten<T>[];
flat(depth: 0): T[];
flat(depth: number): Flatten<Flatten<Flatten<Flatten<T>>>> extends readonly any[] ? unknown[] : Flatten<Flatten<Flatten<Flatten<T>>>>[] | Flatten<Flatten<Flatten<T>>>[] | Flatten<Flatten<T>>[] | Flatten<T>[] | T[];
}

interface Array<T> {
Expand All @@ -124,80 +41,21 @@ interface Array<T> {
* @param thisArg An object to which the this keyword can refer in the callback function. If
* thisArg is omitted, undefined is used as the this value.
*/
flatMap<U, This = undefined> (
callback: (this: This, value: T, index: number, array: T[]) => U | ReadonlyArray<U>,
thisArg?: This
): U[]
flatMap<U> (
callbackfn: (value: T, index: number, array: T[]) => U,
thisArg?: any
): Flatten<U>[];

/**
* Returns a new array with all sub-array elements concatenated into it recursively up to the
* specified depth.
*
* @param depth The maximum recursion depth
*/
flat<U>(this: U[][][][][][][][], depth: 7): U[];

/**
* Returns a new array with all sub-array elements concatenated into it recursively up to the
* specified depth.
*
* @param depth The maximum recursion depth
*/
flat<U>(this: U[][][][][][][], depth: 6): U[];

/**
* Returns a new array with all sub-array elements concatenated into it recursively up to the
* specified depth.
*
* @param depth The maximum recursion depth
*/
flat<U>(this: U[][][][][][], depth: 5): U[];

/**
* Returns a new array with all sub-array elements concatenated into it recursively up to the
* specified depth.
*
* @param depth The maximum recursion depth
*/
flat<U>(this: U[][][][][], depth: 4): U[];

/**
* Returns a new array with all sub-array elements concatenated into it recursively up to the
* specified depth.
*
* @param depth The maximum recursion depth
*/
flat<U>(this: U[][][][], depth: 3): U[];

/**
* Returns a new array with all sub-array elements concatenated into it recursively up to the
* specified depth.
*
* @param depth The maximum recursion depth
*/
flat<U>(this: U[][][], depth: 2): U[];

/**
* Returns a new array with all sub-array elements concatenated into it recursively up to the
* specified depth.
*
* @param depth The maximum recursion depth
*/
flat<U>(this: U[][], depth?: 1): U[];

/**
* Returns a new array with all sub-array elements concatenated into it recursively up to the
* specified depth.
*
* @param depth The maximum recursion depth
*/
flat<U>(this: U[], depth: 0): U[];

/**
* Returns a new array with all sub-array elements concatenated into it recursively up to the
* specified depth. If no depth is provided, flat method defaults to the depth of 1.
*
* @param depth The maximum recursion depth
*/
flat<U>(depth?: number): any[];
flat(depth: 4): Flatten<Flatten<Flatten<Flatten<T>>>>[];
flat(depth: 3): Flatten<Flatten<Flatten<T>>>[];
flat(depth: 2): Flatten<Flatten<T>>[];
flat(depth?: 1): Flatten<T>[];
flat(depth: 0): T[];
flat(depth: number): Flatten<Flatten<Flatten<Flatten<T>>>> extends readonly any[] ? unknown[] : Flatten<Flatten<Flatten<Flatten<T>>>>[] | Flatten<Flatten<Flatten<T>>>[] | Flatten<Flatten<T>>[] | Flatten<T>[] | T[];
}
13 changes: 3 additions & 10 deletions src/lib/es5.d.ts
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Expand Up @@ -1081,11 +1081,7 @@ interface ReadonlyArray<T> {
* @param items Additional items to add to the end of array1.
*/
concat(...items: ConcatArray<T>[]): T[];
/**
* Combines two or more arrays.
* @param items Additional items to add to the end of array1.
*/
concat(...items: (T | ConcatArray<T>)[]): T[];
concat<U extends any[]>(...items: U): (T | Flatten<U[number]>)[];
/**
* Adds all the elements of an array separated by the specified separator string.
* @param separator A string used to separate one element of an array from the next in the resulting String. If omitted, the array elements are separated with a comma.
Expand Down Expand Up @@ -1187,6 +1183,7 @@ interface ConcatArray<T> {
join(separator?: string): string;
slice(start?: number, end?: number): T[];
}
type Flatten<T> = T extends undefined ? T : T extends ConcatArray<infer U> ? U : T;

interface Array<T> {
/**
Expand Down Expand Up @@ -1215,11 +1212,7 @@ interface Array<T> {
* @param items Additional items to add to the end of array1.
*/
concat(...items: ConcatArray<T>[]): T[];
/**
* Combines two or more arrays.
* @param items Additional items to add to the end of array1.
*/
concat(...items: (T | ConcatArray<T>)[]): T[];
concat<U extends any[]>(...items: U): (T | Flatten<U[number]>)[];
/**
* Adds all the elements of an array separated by the specified separator string.
* @param separator A string used to separate one element of an array from the next in the resulting String. If omitted, the array elements are separated with a comma.
Expand Down
29 changes: 29 additions & 0 deletions tests/baselines/reference/arrayConcat2.js
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Expand Up @@ -6,6 +6,24 @@ a.concat('Hello');

var b = new Array<string>();
b.concat('hello');

const expected1: undefined = undefined as Flatten<undefined>;

// #19535

let [actual2] = (undefined as unknown as string[][]).concat([""]);
const expected2: string | string[] = actual2;
actual2 = undefined as unknown as string | string[];

// #26378

let [actual3] = [""].concat([1]);
const expected3: string | number = actual3;
actual3 = undefined as unknown as string | number;

// #26976

[].concat([""]);


//// [arrayConcat2.js]
Expand All @@ -14,3 +32,14 @@ a.concat("hello", 'world');
a.concat('Hello');
var b = new Array();
b.concat('hello');
var expected1 = undefined;
// #19535
var actual2 = undefined.concat([""])[0];
var expected2 = actual2;
actual2 = undefined;
// #26378
var actual3 = [""].concat([1])[0];
var expected3 = actual3;
actual3 = undefined;
// #26976
[].concat([""]);
42 changes: 42 additions & 0 deletions tests/baselines/reference/arrayConcat2.symbols
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Expand Up @@ -21,3 +21,45 @@ b.concat('hello');
>b : Symbol(b, Decl(arrayConcat2.ts, 5, 3))
>concat : Symbol(Array.concat, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))

const expected1: undefined = undefined as Flatten<undefined>;
>expected1 : Symbol(expected1, Decl(arrayConcat2.ts, 8, 5))
>undefined : Symbol(undefined)
>Flatten : Symbol(Flatten, Decl(lib.es5.d.ts, --, --))

// #19535

let [actual2] = (undefined as unknown as string[][]).concat([""]);
>actual2 : Symbol(actual2, Decl(arrayConcat2.ts, 12, 5))
>(undefined as unknown as string[][]).concat : Symbol(Array.concat, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
>undefined : Symbol(undefined)
>concat : Symbol(Array.concat, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))

const expected2: string | string[] = actual2;
>expected2 : Symbol(expected2, Decl(arrayConcat2.ts, 13, 5))
>actual2 : Symbol(actual2, Decl(arrayConcat2.ts, 12, 5))

actual2 = undefined as unknown as string | string[];
>actual2 : Symbol(actual2, Decl(arrayConcat2.ts, 12, 5))
>undefined : Symbol(undefined)

// #26378

let [actual3] = [""].concat([1]);
>actual3 : Symbol(actual3, Decl(arrayConcat2.ts, 18, 5))
>[""].concat : Symbol(Array.concat, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
>concat : Symbol(Array.concat, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))

const expected3: string | number = actual3;
>expected3 : Symbol(expected3, Decl(arrayConcat2.ts, 19, 5))
>actual3 : Symbol(actual3, Decl(arrayConcat2.ts, 18, 5))

actual3 = undefined as unknown as string | number;
>actual3 : Symbol(actual3, Decl(arrayConcat2.ts, 18, 5))
>undefined : Symbol(undefined)

// #26976

[].concat([""]);
>[].concat : Symbol(Array.concat, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
>concat : Symbol(Array.concat, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))

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