[ReadOnlyArray] Array.isEmptyArray does not perform type narrowing about effect HOT 2 OPEN

This is a TypeScript issue AFAIK. Refinement types are good at telling what a type is, but not good at what it isn't, unless the type you're refinining is a union. However, in this example, we're dealing subtypes of Arrays rather than unions.

EDIT: For example, we have similar kinds of code at my job:

from effect.

You can get the desired type safety at a cost of double negation (which I wouldn't trade for)

import { isNonEmptyArray } from '@effect/data/ReadonlyArray'


function foo<T>(arr: T[]) {
    if (!isNonEmptyArray(arr)) {
        return;
    }

    arr; // [T, ...T[]]
}

Or if you can live with nesting

import { isNonEmptyArray } from '@effect/data/ReadonlyArray'

function foo<T>(arr: T[]) {
    if (isNonEmptyArray(arr)) {
      arr; // [T, ...T[]]
    }

}

from effect.