fixed #1.

But, the message in the message is defined top-level because Dart is not supported inner class.

I think it is not work the following protobuf code...

message A {
  message B { // ... (1)
    string b = 1;
  }
  B bb = 2;
}

message B {  // ... (2)
  string bbb = 1;
}

Maybe message B(1) will be overloaded as message B(2) .

Therefore I want to hear opinions of people familiar with Dart because I'm not too familiar with it...

Thx