DeepKeys

type DeepKeys<T, TDepth> = TDepth["length"] extends 5 ? never : unknown extends T ? string : T extends ReadonlyArray<any> & IsTuple<T> ?
  | AllowedIndexes<T>
  | DeepKeysPrefix<T, AllowedIndexes<T>, TDepth> : T extends any[] ? DeepKeys<T[number], [...TDepth, any]> : T extends Date ? never : T extends object ? keyof T & string | DeepKeysPrefix<T, keyof T, TDepth> : never;