In particular, it's missing static const List, Map, and Set initializers.

e.g.:

class Blah {
  static const List<int> ints = [1, 2]; // not found by const_finder
}

Which means --tree-shake-icons will drop things for you if you dos omething like

class Blah {
  static const List<Widget> icons = <Widget>[Icon(Icons.email), ...];
}

@alexmarkov has helped me find some missing things with the const finder implementation for this. Currently testing a fix.