Download the Dart Programming Language Specification from the Ecma website:
You can find previous editions of the specification at Standard ECMA-408.
The 4th edition of the specification has fewer restrictions on Mixins. The restrictions on Mixins up until this edition were: * Mixins must inherit directly from Object * Mixins cannot contain super calls * Mixins cannot define constructors
Only the last one, Mixins cannot define constructors, remains.
Interested in learning about new features that may be added to Dart?
You can track all Dart Enhancement Proposals (DEPs) in the dart_enhancement_proposals repo on GitHub.