Dart Closure Placeholders

gistfile1.dart

final _ = placeholder;

main() {
  var list = [1, 2, 3];

  print(list.map(_ + 2).map(_ * 10));
  print(list.where(_ == 2).map(_.runtimeType));

  print(list.map((v) => v + 2).map((v) => v * 10));
  print(list.where((v) => v == 2).map((v) => v.runtimeType));
}

placeholder.dart

library placeholder;
import 'dart:mirrors';

class Placeholder {
  noSuchMethod(Invocation i) {
    var name = i.memberName;
    var pos = i.positionalArguments;
    withMirror(InstanceMirror f(InstanceMirror)) =>
            (v) => f(reflect(v)).reflectee;
    return
        i.isGetter ? withMirror((m) => m.getField(name)) :
        i.isSetter ? withMirror((m) => m.setField(name, pos.single)) :
          withMirror((m) => m.invoke(name, pos, i.namedArguments));
  }

  toString() => (v) => v.toString();
  get hashCode => (v) => v.hashCode;
  operator==(other) => (v) => v == other;
  get runtimeType => (v) => v.runtimeType;
}

final placeholder = new Placeholder() as dynamic;