Arrayable is unusable

[fregante]

Initially reported in #935 (comment)

In short:

• function castArray<T>(a: Arrayable<T>): T[] is hard to type
  Demo
• The code example in the type's source produces any[], losing the type information provided
  Demo
  

cc @Max10240 let's continue here

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[Emiyaaaaa]

Seems like a typescript bug about Array.isArray(readonly T[])
microsoft/TypeScript#17002

Maybe we can remove readonly? I think no one really want to pass a readonly array in.

[Max10240]

I agree. After all, it's called Arrayable , not ReadonlyArrayable😂

[Emiyaaaaa]

I agree. After all, it's called Arrayable , not ReadonlyArrayable😂

But the reason for adding readonly is to support "all array"(Array and readonly Array), if we remove readonly, readonly Array will can not be passed in.

[Max10240]

Yes, I know that, which is why I was fine when @sindresorhus suggested I add the readonly modifier. But not being able to work with "Array.isArray" is really a big problem, and in general, I recommend removing "readonly".