One thing I really like about Dart is the lack of interface objects, they are implicit. The `contract` proposal feels like having to write interfaces. The inference in Dart is really nice to work with as the compiler gets it right most of the time.

The other thing is the documentation is really easy to grok and come up to speed on:

https://dart.dev/guides/language/language-tour#generics

https://dart.dev/guides/language/sound-dart

Edit: Additionally, mocking (with Mockito-Dart) becomes trivial, which is great for unit testing:

  class Thing {
    String boo;
  }

  class MockedThing extends Mock implements Thing {}

  when(thing.boo).thenReturn('ack');