Non-nullable by default: how to enable the experiment?

Question

I just tried the following in DartPad:

void main() {
  int? x;
}

and get the following error:

Error compiling to JavaScript         


        

Answer 1

You enable the experiment by passing the flag --enable-experiment=non-nullable to the compiler or analyzer.

It is not a complete feature yet, so there are no promises about what it will do. Feel free to experiment, but don't use the flag for anything serious.