function bound(originalMethod: any, context: ClassMethodDecoratorContext): void {
  const methodName = context.name;
  context.addInitializer(function (this: any) {
    this[methodName] = this[methodName].bind(this);
  });
}

class Base {
  constructor() {
    this.init();
  }

  protected init() {

  }
}

class Foo extends Base {
  bar?: string;

  override init() {
    super.init();
    this.bar = 'hello';
  }

  @bound
  public doSomething() {

  }
}
console.log(new Foo().bar);