Dart factory 构造函数语法问题

Question

class Father {
  String name;
  Father(this.name);
  // 下面两行，是等效的吗？是什么语法，官方文档具体页面有没有？
  factory Father.born(String name) = Son;
  factory Father.born2(String name) => Son(name);
}

class Son extends Father {
  Son(String name): super(name);
}


main(List<String> args) {
  var son1 = Father.born('name1');
  var son2 = Father.born2('name2');
  print(son1.name);
  print(son2.name);
}