text: function f(v) {
    return v.x + v.x + v.y;
  }
  
  f({
    x: 1,
    y: 2
  });
  4;
  f({
    __proto__: {
      x: 1,
      y: 2
    }
  });
  4;
  f({
    __proto__: {
      x: 0,
      y: 2
    },
    x: 1
  });
  4; // Ensure there is no aliasing.
  
  var global = 1;
  f(Object.defineProperty({
    y: 2
  }, "x", {
    get: function () {
      return global++;
    }
  }));
  5;
  