// Original project:

class Foo {
  x = 2;
  y = 3;
}

class Bar extends Foo {
  x;

  sum() {
    const sum = (this.x || 5) + this.y;
    console.log(sum);
  }
}

new Bar().sum(); // Logs 8 (5 + 3);

// With types:

class Foo {
  x: ?number = 2;
  y: number = 3;
}

class Bar extends Foo {
  // *

  sum() {
    const sum: number = (this.x || 5) + this.y;
    console.log(sum);
  }
}

new Bar().sum(); // Should log 8 (5 + 3);