Utility type to pick keys by type

pick-keys-by-type.ts

export type Primitive = string | number | boolean | bigint | symbol | undefined | null;

export type PickKeysDeep<T, P = any> = {
    [K in keyof T]: T[K] extends object 
        ? P extends Primitive
            ? PickKeysDeep<T[K], P> 
            : K | PickKeysDeep<T[K], P>
        : P extends Primitive 
            ? P extends T[K] 
                ? K 
                : never
            : never
}[keyof T]

type Test = PickKeysDeep<{
    a: number,
    test: {
        b: {
            c: number,
            y: string
        }
        c: string
    }
}, object>

const a: Test = "a"

god forgive me