[Semiapies]

That's kind of amazing.

[IanCal]

Here are some more examples, though are generally more basic errors: http://elm-lang.org/blog/compilers-as-assistants

Overall, I really like the approach of making error messages an important feature. We see them so often that improving them makes the developer experience much better, but I can imagine they're a less 'sexy' task to work on and probably much harder to get right than you'd expect.