| (disclaimer: I work on the Flutter team.) It's true that Dart is an optionally-typed system, and that type annotations are ignored at runtime. That may seem scary at first, but we built an analyzer that statically analyzes your program and gives you feedback (errors, warnings, and hints). Dart is used at Google to build very big and complex apps, and our engineers use the analyzer in their build/CI systems to check their program. The analyzer is also wired into their IDEs. So they get feedback if a method doesn't exist, or you are trying to pass a variable into a method that is expecting something else. The Dart team is also working on an optional analyzer feature called "strong mode", which does even more static checking. In strong mode, you can't write code that is incorrectly typed (but, you can still write code that is dynamically typed, if you want to). Our experience, at least internally, is that as your program matures and grows in complexity, developers appreciate the extra checks provided by strong mode. The win is that it's something you can turn on later, when you're ready. Early on in the program's development, you are probably refactoring a lot and you don't want to bother with strong mode. This scalability is a win for us. |