Require at least one element in arrays or function arguments (RequireAtLeastOne)

[fregante]

I'm opening this issue for documentation/googlability, but it should also probably be added to https://github.com/sindresorhus/type-fest/blob/main/source/require-at-least-one.d.ts

It turns out, RequireAtLeastOne also works with arrays:

type NonEmptyArray = RequireAtLeastOne<unknown[], 0>;
export const full: NonEmptyArray = [2];
export const empty: NonEmptyArray = [];
// Type '[]' is not assignable to type 'NonEmptyArray'.
//   Property '0' is missing in type '[]' but required in type 'Required<Pick<unknown[], 0>>'.

It also works for functions:

export function atLeastOneArg(...numbers: RequireAtLeastOne<number[], 0>): number[] {
	return numbers;
}

atLeastOneArg(0);
atLeastOneArg();
// Argument of type '[]' is not assignable to parameter of type 'RequireAtLeastOne<number[], 0>'.
//  Property '0' is missing in type '[]' but required in type 'Required<Pick<number[], 0>>'.ts(2345)

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[adam-rocska]

Nice idea, but won't cover for cases like 😢

const wontWork: RequireAtLeastOne<number[], 0> = [...[], ...[1]];

[fregante]

As mentioned in #476, that's likely a non-resolvable TypeScript limitation (because it doesn't resolve the value/type deeply enough)