The dev.typeparams work is undergoing very active change, and it is much much too early to start reporting bugs against it. Contributions are welcome but filing bugs now will just be a distraction. I've CC'ed the relevant people but I'm going to close this issue. Thanks.
Thanks, but we prefer to use the issue tracker for bug reports and proposals. If you want to discuss the approach being taken on the dev.typeparams branch, I recommend using golang-dev. But it is much much too early to draw any conclusions at all based on the code being generated.