类型别名 DeepMerge<F, S>

DeepMerge: MergeInsertions<
    {
        [K in keyof F
        | keyof S]: K extends keyof S & keyof F
            ? DeepMerge<F[K], S[K]>
            : K extends keyof S ? S[K] : K extends keyof F ? F[K] : never
    },
>