recursively mark all properties of a typescript type as defined

deep-complete.ts

/** private type, not exported */
declare type NonObject = undefined | null | boolean | string | number | Function;
/**
 * This type allows you to mark an object with 
 * optional properties as required.
 */
export declare type Complete<T> = {
  [K in keyof T]-?: T[K];
}
/**
 * This type allows you to mark an object with 
 * optional properties as required recursively.
 */
export declare type DeepComplete<T> = 
  T extends NonObject ? 
    T extends undefined ? never : T
    : 
    T extends Array<infer U> ? 
      DeepCompleteArray<U> 
      : 
      T extends Map<infer K, infer V> ? 
        DeepCompleteMap<K, V> 
        : 
        DeepCompleteObject<T>;

interface DeepCompleteArray<T> extends ReadonlyArray<DeepComplete<T>> { } 
interface DeepCompleteMap<K, V> extends ReadonlyMap<DeepComplete<K>, DeepComplete<V>> { }
declare type DeepCompleteObject<T> = {
    [K in keyof T]-?: DeepComplete<T[K]>;
};