[frankpf]

TypeScript has ADTs, non-nullable types and the tooling is one of the best (great autocomplete, support for refactorings, incremental compilation, yarn is a great package manager, etc).

Its type system is also one of the most advanced in mainstream languages, being inferior only to Scala and Haskell.

In comparison, Dart doesn't have ADTs or non-nullable types. For a new language, I consider this very underwhelming.

I'm considering using Flutter for a new project because it seems to be a great platform, but having to use Dart instead of TypeScript is a step backwards.