Consider enhancing compiler errors.

It would be nice to prefix/suffix an error like this with something like `Take a look at line 10` in bold or something. I figure this is probably doable with regexp/ansi.

<img width="631" alt="Screenshot 2021-04-05 at 18 18 45" src="https://user-images.githubusercontent.com/286476/113603092-63691500-963b-11eb-94b4-46adb384f412.png">
