Improve string split return type of first array index

lib Update Request

Please, consider improving user experience for "".split(...) in cases when string literal is passed, which I believe most users do e.g. split(' ') or split('\n')

Configuration Check

My compilation target is ES2015 and my lib is the default.

Missing / Incorrect Definition

https://github.com/microsoft/TypeScript/blob/b70784ef8f3ba3fd21750b9acf275dd7edcc7fe7/src/lib/es5.d.ts#L460

Essentially duplicate of https://github.com/microsoft/TypeScript/issues/49635, but with https://github.com/microsoft/TypeScript/issues/49635#issuecomment-1163047914 handled:

split<T extends string | RegExp>(separator: T, limit?: number): T extends `${string}${infer U}` ? [string, ...string[]] : string[];

And this should added to param JSDoc then: Only passing `""` and `new RegExp("")` values can result in returning an empty array.

Sample Code

This is super inconvenient when used with destructure:

const [firstLine, ...restLine] = str.split('\n')
// firstLine is possibly undefined, need add exclamation marks everywhere or `as [string, ...string]` above

I also wanted to do the same for when regexp literal is passed e.g. split(/\n\r?/) as only split(new RegExp('')) can result in empty array (if I'm not mistaken), which I believe no one does, but the literal value can't be captured anyway

Documentation Link

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/split#description (note)

P.S. I remembered of this issue after https://github.com/microsoft/TypeScript/pull/49682, which significantly improved type-checking experience by using less exclamation marks

Comienza con la declaración de String.split en src/lib/es5.d.ts alrededor de la línea 460 y, después, revisa el issue relacionado #49635 y el comentario al que hace referencia. Se considera terminado cuando el tipo distingue los separadores literales no vacíos como una tupla cuyo primer elemento no está vacío, conserva los casos de arrays vacíos y documenta esos casos en el JSDoc del parámetro.