types.ts

export type NoInfer<T> = [T][T extends any ? 0 : never];

/**
 * Adapted from type-fest's PartialDeep
 */
export type PartialDeep<T> = T extends (...args: infer P) => infer R
  ? ((...args: P) => PartialDeep<R> | void) & PartialDeepObject<T> | PartialDeepObject<T> | undefined
  : T extends object
  ? T extends ReadonlyArray<infer ItemType> // Test for arrays/tuples, per https://github.com/microsoft/TypeScript/issues/35156
    ? ItemType[] extends T // Test for arrays (non-tuples) specifically
      ? readonly ItemType[] extends T // Differentiate readonly and mutable arrays
        ? ReadonlyArray<PartialDeep<ItemType | undefined>>
        : Array<PartialDeep<ItemType | undefined>>
      : PartialDeepObject<T> // Tuples behave properly
    : PartialDeepObject<T>
  : T;

export type PartialDeepObject<ObjectType extends object> = {
  [KeyType in keyof ObjectType]?: PartialDeep<ObjectType[KeyType]>;
};