interface A {
  name: string;
}
interface B {
  age: number;
}

function test(): A | B {
  if (Math.random() > 0.5) {
    return {
      age: 28,
    }
  }
  
  return {
    name: 'zero'
  }
};
const target1: A & B = test();
// Type 'A | B' is not assignable to type 'A & B'
const target2: A = test();
// Type 'A | B' is not assignable to type 'A'
const target3: B = test();
// Type 'A | B' is not assignable to type 'B'