Expanding Record

expand.ts

const foo = {foo: 1}
const bar = {bar: 2}
const baz = {...foo, ...bar}

const merge = <X,Y>(a:X, b:Y): X&Y => ({...a, ...b})

class ExpandingRecord<A> {
  record: A;

  constructor(record: A) {
    this.record = record;
  }

  merge<B>(b: B): ExpandingRecord<A & B> {
      return new ExpandingRecord(merge(this.record, b))
  }

  result() {
      return this.record
  }
}

const initRec = new ExpandingRecord({bar: 1})
const other = {foo:2}
const second : {foo: number, blah: number} = initRec.merge({foo:2}).merge({blah:3}).result()