Syntax for Dart's assign if null operator

dart-assign-if-null.dart

void main() {  
  var middleName = middle("iAmWillShepherd");
  middleName ??= "This assignment won't happen.";
    
  print(middleName); // Logs 'S' in the console
  
  var noMiddle = middle("No middle exists");
  noMiddle ??= "This assignment will happen.";
  print(noMiddle); // This assignment will happen.
}

String? middle(String s) {
  return s.length % 2 == 0 ? null : s.substring(s.length ~/ 2, s.length ~/ 2 + 1);
}