structural-with-classes.ts

class A {
  value: string;
  constructor(val: string) {
    this.value = val;
  }
};
class B {
  value: string;
  constructor(val: string) {
    this.value = val;
  }
};
function my_func(a: A): string {
  return a.value;
}
const b = new B("hi");
my_func(b); // still no error!