Function pickWhere

pickWhere<T extends {}, S>(
    x: T,
    predicate: (x: unknown) => x is S,
): {
    -readonly [K in string | number | symbol as T[K] extends undefined
    | S
        ? K
        : never]: T[K]
}

pickWhere<T extends {}, S>(
    x: T,
    predicate: (x: unknown) => boolean,
): {
    -readonly [K in string | number | symbol as T[K] extends undefined
    | S
        ? K
        : never]: T[K]
}