The core implementation is defined directly in Dart2Js, Dartium, and dev_compiler.
Contributing and Filing Bugs
Please file bugs and features requests on the Github issue tracker.
We also love and accept community contributions, from API suggestions to pull requests. Please file an issue before beginning work so we can discuss the design and implementation. We are trying to create issues for all current and future work, so if something there intrigues you (or you need it!) join in on the discussion.
All we require is that you sign the Google Individual Contributor License Agreement.