Testing combining typescript interfaces

interface-tests.ts

// base
export interface MyThing {
  name: string;
}

// first type of calcs for base
export interface MyThingCalcA {
  calcA: number;
}

// second type of calcs for base
export interface MyThingCalcB {
  calcB: number;
}

// used to extend an object with calcs
export interface CalcThing<T> {
  calculated: T;
}

// My Thing with various calculations attached
export interface MyThingCalculated<T extends MyThingCalcA | MyThingCalcB> extends MyThing, CalcThing<T>{
}

// option 1a: Insert object, return calcs only
export function useThingInAndCalcOnlyOut(thing: MyThing): MyThingCalcA {
  return { calcA: 123 };
}

// option 1b: Multi calcs returned
export function useThingInAndMultiCalcOut(thing: MyThing): MyThingCalcA & MyThingCalcB {
  return { calcA: 123, calcB: 321 };
}

// option 2a: Insert object, return object with calcs attached
export function useThingInAndFullCalcOut(thing: MyThing): MyThingCalculated<MyThingCalcB> {
  return { ...thing, calculated: {calcB: 123} };
}

// option 2b: Insert object, return object with multiple calcs attached 
export function useThingInAndFullMultiCalcOut(thing: MyThing): MyThingCalculated<MyThingCalcA & MyThingCalcB> {
  return { ...thing, calculated: {calcA: 123, calcB: 321} };
}

// -- Testing
// const x = useThingInAndFullMultiCalcOut({name: 'test'});
// x.name;
// x.calculated.calcA;
// x.calculated.calcB;