鉴于 Typescript 中发现的这段（令人惊奇的）代码 ：嵌套对象的深层 keyof
type Cons<H, T> = T extends readonly any[] ?
((h: H, ...t: T) => void) extends ((...r: infer R) => void) ? R : never
: never;
type Prev = [never, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10,
11, 12, 13, 14, 15, 16, 17, 18, 19, 20, ...0[]]
type Paths<T, D extends number = 10> = [D] extends [never] ? never : T extends object ?
{ [K in keyof …typescript ×1