Generation of nested structures with the same name results in compiler errors

[nubstick27]

There appears to be an issue with nested structures which define the same name multiple times.

Briefly, a structure such as:

mutation UpvotePost($postId: Int!) {
  upvotePost(postId: $postId) {
    ...PostDetails
  }
}

results in a generated class like:

public final class UpvotePost implements Mutation<UpvotePost.Variables> {
    public static class Data implements Operation.Data {
        public static class UpvotePost { ... }
    }
}

which has a compilation error.

[sav007]

We are going to use the same logic for resolving dup names by adding $ as suffix, so in this case we ate going to have UpvotePost$