Branded exact object type TypeScript

exact.ts

interface Config {
    port: number
    log_file: string;
    log_level: 'error' | 'warning' | 'info'
}

const config = exact<Config>(['port','log_file','log_level']);
const src = {port: 1000, log_file: 'stdout', log_level: 'info', junk: 'more'} as Config
const x = config(src);
const e = entries(x);
console.log(x, e)

function exact<T extends object>(keys: UnionToTuple<keyof T> & readonly (keyof T)[]) {
    return (obj: Readonly<T>) => Object.fromEntries(keys.map(k => [k, obj[k]] as const)) as Exact<T>
}

function entries<T extends object>(obj: Exact<T>) {
    return Object.entries(obj as T) as { [K in keyof T]: [K, T[K]]}[keyof T]
}

type UnionToTuple<T> = UnionToIntersection<
  T extends never ? never : (t: T) => T
> extends (_: never) => infer W
  ? [...UnionToTuple<Exclude<T, W>>, W]
  : [];

type UnionToIntersection<U> = (
  U extends never ? never : (arg: U) => never
) extends (arg: infer I) => void
  ? I
  : never;

type Exact<T extends object> = Brand & T
type Brand = { readonly __brand?: unique symbol }