class A {
  x: number;
  _x: string;
  __x: number;
  constructor() { this.x = 0; this._x = ""; this.__x = 0; }
}

class B extends A {
  foo() {
    var x: number = this.x;
    var _x: string = this._x;
    var __x: number = this.__x;
  }
}