"useSprings" return "object[]" when used in a generic hook

[soukipedia]

🤓 Question

I have the following code:

type SpringHandler<T> = (index: number) => T & { y: number, immediate: boolean };
function makeSpringsHandler<T>(config: T): SpringHandler<T>  {
  return (index: number) => ({
    ...config,
    y: 50 * index,
    immediate: false,
  });
}

type Props<T> = { items: any[], config: T };
function useNonGeneric({ items, config }: Props<{ scale: number, zIndex: number }>) {
  const [springs, setSprings] = useSprings(items.length, makeSpringsHandler(config));
  return springs;
  /**
   * Type of springs is:
   * {
   *    scale: SpringValue<number>,
   *    zIndex: SpringValue<number>,
   *    y: SpringValue<number>,
   * }[]
   */
}

function useGeneric<T>({ items, config }: Props<T>) {
  const [springs, setSprings] = useSprings(items.length, makeSpringsHandler(config));
  return springs;
  /**
   * Type of springs is: object[] which is unexpected
   * Shouldn't it be { y: SpringValue<number> & { [P in keyof T]: SpringValue<P> } }
   */
}

I don't know if it is a bug or just I misunderstand it.
i used react-spring v9.0.0-rc.3

[joshuaellis]

v9 re-writes a lot of the code from v9-rc.3, i'd recommend updating to that and going from there.