How to stop Dart demoting doubles to ints

Question

I want to use doubles in my code but Dart converts them to ints (or dynamic).

I have tried to cast them using 'as' or .toDouble() but they do not stay as doubles:

(in dartpad)

main() {
  print ((1.0 as double).runtimeType);
  print (1.0.toDouble().runtimeType);
}

(output)

int
int

I would have expected the output of these statements to be 'double'. If I change the value to 1.1 I get a double out.