tagged_union_types_return_type_bug.ts

// THIS IS NOT WORKING!

type A = {
  type: "A";
  aprop: number;
};

type B = {
  type: "B";
  otherprops: number;
};

type U = A | B;

let zz: any = 1;
let x: U = zz;

if (x.type === "A") {
  x.aprop;
}

if (x.type === "B") {
  x.otherprops;
}

const afunc = () => ({ type: "A", aprop: 2 });
const bfunc = () => ({ type: "B", otherprops: 2 });

// function afunc(): A {
//   //if I remove A it won't work!
//   return { type: "A", aprop: 2 };
// }

// function bfunc(): B {
//   return { type: "B", otherprops: 2 };
// }

type U2 = ReturnType<typeof afunc> | ReturnType<typeof bfunc>;

let x2: U2 = zz;

if (x2.type === "A") {
  x2.aprop;
}

if (x2.type === "B") {
  x2.otherprops;
}

let a3: ReturnType<typeof afunc> = zz;
let b3: ReturnType<typeof bfunc> = zz;

a3.aprop;
b3.otherprops;