Tuple type in rest arguments can not downcast?

Question

type Func<T extends Record<string, any>> = (
  ...args: {
    [K in keyof T]: [item: T[K], key: K, map: T];
  }[keyof T]
) => void;

The Func type can only accpect (item,key,map)=>void,but can't accpect (item)=>void or (item,key)=>void. How to solve this problem?

Answer 1

You could use optionals to allow fewer values in the tuple as follows:

type Func<T extends Record<string, any>> = (
  ...args: {
    [K in keyof T]: [item: T[K], key?: K, map?: T?];
  }[keyof T]
) => void;