There is one major difference between Dart and CoffeeScript: The Angular team didn't have to take a 3 month holiday to make Angular work with CoffeeScript. If Dart was just another compile-to-JS language, then they wouldn't have to bother at all.
Yet, CoffeeScript is not just a different syntax - for one, it changes declarations and scoping rules. That's a pretty big semantic change (comparison operators etc. follow).
Yet, CoffeeScript is not just a different syntax - for one, it changes declarations and scoping rules. That's a pretty big semantic change (comparison operators etc. follow).