Expose NonEmptyTuple

[tommy-mitchell]

Similar to #659, NonEmptyTuple is a convenient type to expose:

type-fest/source/internal.d.ts

Lines 90 to 93 in f63c343

	/**
	Matches any non empty tuple.
	*/
	export type NonEmptyTuple = readonly [unknown, ...unknown[]];

We could augment it to accept a generic type argument:

type NonEmptyTuple<TupleType = unknown> = readonly [TupleType, ...TupleType[]];

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[sindresorhus]

PR welcome 👍

[sindresorhus]

We could augment it to accept a generic type argument:

👍

[tommy-mitchell]

Hm, maybe it's not such a good idea? You can't use array.length checks to guard against empty arrays, and sparse arrays add a lot of edge cases: microsoft/TypeScript#38000 (SO thread)

function printFirstElement<Tuple extends NonEmptyTuple>(tuple: Tuple) {
	console.log(tuple[0]);
}

printFirstElement(['a', 'b', 'c']);
//=> 'a'

printFirstElement([]);
//=> error TS2345: Argument of type '[]' is not assignable to parameter of type 'NonEmptyTuple'.

declare const arr: string[];

if (arr.length > 0) {
	printFirstElement(arr);
	//=> error TS2345: Argument of type 'string[]' is not assignable to parameter of type 'NonEmptyTuple'.
}