attempt at using an object with merge function

merge_obj_stream.ts

import { labeled, pairs, mapA } from "@thi.ng/transducers";
import {
  merge,
  TransformableOpts,
  ISubscribable,
  Subscription,
} from "@thi.ng/rstream";
import { IObjectOf, Pair } from "@thi.ng/api";

type MappedSubcribable<K, V> = {
  [P in K]: ISubscribable<V>;
};

export const mergeKeyed = <K, V>(
  obj: MappedSubcribable<K, V>,
): Subscription<any, Pair<K, V>> =>
  merge({ src: mapA(([k, v]) => v.transform(labeled(k)), pairs(x)) });

mergeKeyed({ a: reactive(42), b: reactive("abc") }).map((x) => {
  switch (k) {
    case "a":
      x; // (parameter) x: Pair<"a" | "b", unknown>
    case "b":
    default:
      throw new Error("unreachable");
  }
});