As stated clearly in their CONTRIBUTING.md, this project follows the very common practice of requiring prior discussion on an issue, before submitting a pull request.
In this case, the pull request author completely ignored that process and submitted a 400+ line unsolicited pull request with no prior discussion. All of the wasted effort would have been completely avoided if the PR author bothered to post a single-sentence issue asking if the maintainers actually want this.
As for a chilling effect, the worse one I see is maintainer burnout from having to deal with PRs like this.
In this case, the pull request author completely ignored that process and submitted a 400+ line unsolicited pull request with no prior discussion. All of the wasted effort would have been completely avoided if the PR author bothered to post a single-sentence issue asking if the maintainers actually want this.
As for a chilling effect, the worse one I see is maintainer burnout from having to deal with PRs like this.