[triyambakam]

Do you mean pass in a type?

    type NonEmptyArray<T> = [T, ...T[]];

[throwaway09432]

I mean if I have a NonEmptyArray say xs, and I then xs.map(x=>2*x), will the result of this expression be a NonEmptyArray ?

[triyambakam]

No, unfortunately it will just be number[] as the return type.