Add MultidimensionalArray type

[Menecats]

MultidimensionalArray type allows you to type multidimensional array declaratively.

This is useful when a funciton returns a multidimentional array were it's dimensions depends on the input of the functions.
e.g.

function createNDimensionalGrid<Depth extends number>(depth: Depth): MultidimensionalArray<number, Depth> {
  // [...]
}

const myGrid = createNDimensionalGrid(2);
const myOtherGrid = createNDimensionalGrid(9);

myGrid[0][5] = 3;
myOtherGrid[0][1][2][3][4][5][6][7][8] = 9;

[sindresorhus]

Thanks for contributing a type. Make sure you read and follow: https://github.com/sindresorhus/type-fest/blob/main/.github/contributing.md#submitting-a-new-type

[sindresorhus]

Do we really need a separate type for readonly array? In our other types we just handle it. For example: 8f70e88

[Menecats]

I think that having the mutable version of this array is a useful option, in fact in a project that I'm currently working on I need it to be mutable.

If you prefer to have only one type definition instead of two, I've just came up with the following:

export type MultidimensionalArray<Element, Dimensions extends number, Readonly extends boolean = true> = number extends Dimensions
	? Recursive<Element, Readonly>
	: IsEqual<Dimensions, 0> extends true
		? Element
		: true extends Readonly
			? ReadonlyArray<MultidimensionalArray<Element, Subtract<Dimensions, 1>, Readonly>>
			: Array<MultidimensionalArray<Element, Subtract<Dimensions, 1>, Readonly>>;

type Recursive<T, Readonly extends boolean> = true extends Readonly
	? ReadonlyArray<Recursive<T, Readonly>>
	: Array<Recursive<T, Readonly>>;


// An example of how a user can use this type

declare const a: MultidimensionalArray<number, 3>; // Readonly
declare const b: MultidimensionalArray<number, 4, true>; // Readonly
declare const c: MultidimensionalArray<number, 5, false>; // Mutable

type MyMutableMultidimensionalArray<T, D extends number> = MultidimensionalArray<T, D, false>;
declare const d: MyMutableMultidimensionalArray<number, 6>; // Mutable

This will allow a user to specify weather or not it wants the MultidimensionalArray to be Readonly.
If you think it's a good idea I can proceed changing my pull request by removing the MultidimensionalReadonlyArray and updating the MultidimensionalArray with these changes

[sindresorhus]

Nah. I think it's better with two separate types than a boolean argument.