class Foo {
  Foo(int a, int b) { /*...*/ }
  Foo.named(int c, int d) { /*...*/ }    // named constructor
}
class Bar extends Foo {
  Bar(int a, int b) : super(a, b);
}
class Baz extends Foo {
  Baz(int c, int d) : super.named(c, d);  
}