'all' and TypeScript

[davetapley]

I have a list of number | undefined. I want to know if they're all number, and have it type check.

I tried all(isNotNil, data), but the types aren't narrowed (somewhat expected).
So here's what I came up with, using type predicates, works but is a bit verbose:

import { all } from 'ramda';

const hasData = (data: number | undefined): data is number =>
    data !== undefined;
const allHasData = (data: (number | undefined)[]): data is number[] =>
    all(hasData, data);

If I hover data in VSCode it shows the narrowed type correctly:

const data = [1, undefined, 3];

if (allHasData(data)) {
    console.log('All', data); // const data: number[]

} else {
    console.log('Not all', data); // const data: (number | undefined)[]
}

If I switch for either of these I get const data: (number | undefined)[] in both branches 😑

const loaded = all(isNotNil, data);
const loaded = all(hasData, data);

Is there a more terse / less explicit way to do this?