empty_constructor_bodies

From the style guide:

DO use ; instead of {} for empty constructor bodies.

In Dart, a constructor with an empty body can be terminated with just a semicolon. This is required for const constructors. For consistency and brevity, other constructors should also do this.

GOOD:

class Point {
  int x, y;
  Point(this.x, this.y);
}

BAD:

class Point {
  int x, y;
  Point(this.x, this.y) {}
}