This comment was originally written by @DuVo

Here is my basic implementation. I didn't used it a lot... so many bugs can be still present :

dynamic mappify(dynamic object) {
  List seen = [];

  void checkCycle(final object) {
    for (var item in seen) {
      if (identical(item, object)) {
        throw new MapperCyclicException(object);
      }
    }
    seen.add(object);
  }

  dynamic mapFromObject(dynamic object) {
    if (object is num || object is String || object is bool || object == null) {
      return object;
    }else if (object is Map) {
      checkCycle(object);
      Map map = {};
      object.forEach((key, value) {
        map[key.toString()] = mapFromObject(value);
      });
      seen.remove(object);
      return map;
    } else if (object is Iterable) {
      checkCycle(object);
      var tmp = new List.generate(object.length, (i) => mapFromObject(object[i]), growable: false);
      seen.remove(object);
      return tmp;
    } else {
      checkCycle(object);
      Map map = {};
      InstanceMirror instanceMirror = reflect(object);
      ClassMirror classMirror = instanceMirror.type;
      for(Symbol key in classMirror.variables.keys) {
        map[MirrorSystem.getName(key)] = mapFromObject(instanceMirror.getField(key).reflectee);
      }
      for(Symbol key in classMirror.getters.keys) {
        map[MirrorSystem.getName(key)] = mapFromObject(instanceMirror.getField(key).reflectee);
      }
      seen.remove(object);
      return map;
    }
  }

  return mapFromObject(object);
}

While this is definitely possible using mirrors, as you have shown, I don't think it's something we will want in the core libraries.
A Map and a non-Map object are different things (unlike in JavaScript), and treating an plain object as a Map is really hiding a lot of mirror operations.

Seems like an obvious choice for a package, but not something I think fits in the core library.

Removed Type-Defect label.
Added Type-Enhancement, Area-Library, Triaged labels.

This comment was originally written by @DuVo

I'm not necessarily talking about adding in the core. And I am aware that a Map can't handle all information from a mirrors. But when I thought about it, it's really like the stringify method, from json.

Mirrors are no longer supported on the web.

For both web and VM our current recommendation is to use codegen. I think there are also a couple VM libraries that do this type of thing with mirrors but it's not something we plan to support in the SDK.