Stricter FixedLengthArray
FixedLengthArray could be improved to be stricter. Take this snippet for example:
const array: FixedLengthArray<number, 3> = [1, 2, 3];
array[4];The final line should not compile since index 4 doesn't exist on the array.
Instead a type something like this could be used:
type Helper<Element, Length extends number, Rest extends Element[]> = Rest['length'] extends Length ? Rest : Helper<Element, Length, [Element, ...Rest]>;
export type FixedLengthArray<Element, Length extends number> = Length extends Length ? (number extends Length ? Element[] : Helper<Element, Length, []>) : never;This uses TypeScript's tuple types directly instead of [index: number]: Element which is much safer.
Playground for current behavior
Playground for proposed behavior
sindresorhus / type-fest
A collection of essential TypeScript types
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