Snippet 8: The assertion operator

main.dart

// If you'd like to assign a nullable expression
// to a variable that's non-nullable, you can use
// the assertion operator (the exclamation point:
// `!`). By adding `!` just after the expression,
// you tell Dart that the value won't be null,
// and it's safe to assign to a non-nullable
// variable.
//
// Note: if you're wrong, an exception will be
// thrown!
//
// Try adding exclamation points to correct the
// three broken assignments in this code:

int? couldReturnNullButDoesnt() => -3;

void main() {
  int? couldBeNullButIsnt = 1;
  List<int?> listThatCouldHoldNulls = [2, null, 4];
  
  int a = couldBeNullButIsnt;
  int b = listThatCouldHoldNulls.first;
  int c = couldReturnNullButDoesnt().abs();
  
  print('a is $a.');
  print('b is $b.');
  print('c is $c.');
}