`Array.isArray` does not recognize `readonly` arrays

[GauBen]

Hi TS team! I'm having an issue with the type of Array.isArray:

declare const x: readonly number[]

if (Array.isArray(x)) {
    let y = x[0]
     // ^? let y: any
}

Playground

I'm willing to open a PR if the fix is as I suggest in the playground above

[orta]

This is the wrong repo (this is for the DOM types) but you're looking at an incredibly deep rabbit hole if you want to try solve that, you can start based on links in one of my best attempts a few years back: microsoft/TypeScript#42316

[GauBen]

Thanks for the heads up! It was an interesting read but I'm not sure I should invest some more time in this. I'm closing in favor of microsoft/TypeScript#17002