Literally that, it would throw exceptions with the compiler error. And as a sibling comment mentioned and I had forgotten -- it would allow for hotpatching code

Literally that, it would throw exceptions with the compiler error. And as a sibling comment mentioned and I had forgotten -- it would allow for hotpatching code at runtime as you fixed compiler errors. You could literally start the skeleton of a webserver and gradually add functionality to it without recompiling and it would mostly "just work". Certain changes would require the app to be restarted.