Inspection, unresolved variable on this.* in javascript class Follow

Hi

I have a following class (in ES6).

class Foo {
  constructor()
  {
    this._bar = '1';
  }
  
  foobar() {
    this.e = this._bar; // this._bar is marked as unresolved variable 
  }
}

My problem is, that Webstorm marks this.bar in method foobar as unresolved variable.
The only solution that I've found is to mark the _bar as property, but I do not like that, since _bar should stay "private" and not to be displayed in documentation

/**
 * @class Foo
 * @property {string} _bar
 */
class Foo {
  constructor()
  {
    this._bar = '1';
  }

  foobar() {
    this.e = this._bar;
  }
}