babel class fields and pipline operator

input.js

const Point = class {
  x = 0;
  y = 0;
};

const serializable = Category => class extends Category {
  toString() {
    return `[${this.x}, ${this.y}]`;
  }
};

const movable = Category => class extends Category {
  move(x, y) {
    this.x += x;
    this.y += y;
  }
};

const PointEx = Point |> serializable |> movable;
const point = new PointEx();

point.move(6, -4);
console.log(point.toString());

const { x, y } = point;
console.log(x, y);

output.js

var _temp, _ref, _Point;

function _defineProperty(obj, key, value) { if (key in obj) { Object.defineProperty(obj, key, { value: value, enumerable: true, configurable: true, writable: true }); } else { obj[key] = value; } return obj; }

const Point = (_temp = class Point {
  constructor() {
    _defineProperty(this, "x", 0);

    _defineProperty(this, "y", 0);
  }

}, _temp);

const serializable = Category => class extends Category {
  toString() {
    return `[${this.x}, ${this.y}]`;
  }

};

const movable = Category => class extends Category {
  move(x, y) {
    this.x += x;
    this.y += y;
  }

};

const PointEx = (_ref = (_Point = Point, serializable(_Point)), movable(_ref));
const point = new PointEx();
point.move(6, -4);
console.log(point.toString());
const {
  x,
  y
} = point;
console.log(x, y);

package.json

{
  "devDependencies": {
    "@babel/cli": "^7.7.7",
    "@babel/core": "^7.7.7",
    "@babel/plugin-proposal-class-properties": "^7.7.4",
    "@babel/plugin-proposal-pipeline-operator": "^7.7.7"
  },
  "scripts": {
    "build": "babel input.js -o output.js"
  },
  "babel": {
    "plugins": [
      "@babel/proposal-class-properties",
      ["@babel/proposal-pipeline-operator", {
        "proposal": "minimal"
      }]
    ]
  }
}