This is an excellent idea. I wrote a blog post talking about the error messages in Elm. Whilst these error messages are fantastic they aren’t short. Once you’ve been around Elm for a while, you don’t really need the full spiel. So I was suggesting a --terse flag, but this is perhaps even better. I ended the blog-post by stating " I say would propsose this, but I don’t actually think this should be done, I just don’t think it has enough bang for the buck of the involved effort." Your cli tool takes the effort from the Elm compiler, though I don’t know whether it will be difficult to maintain or not.
Anyway brilliant stuff.
Love it and I believe this can be extremely helpful. I understand your motivation to have this in a separate tool, but maybe we could take this as a PoC for an actual compiler feature?
Not sure how much effort it would be to open a PR with this feature in the compiler’s repo.