Even the JVM has a fair number of issues if you use class reloading to do Weird Stuff (tm), especially with advanced debugger tricks added into the mix. That's

Even the JVM has a fair number of issues if you use class reloading to do Weird Stuff (tm), especially with advanced debugger tricks added into the mix. That's one of the reasons some of the folks I know who use Scala switched in the first place. I think any hot-reloading solution for a big, complex, introspective/reflective language is going to have some warts* and places where it stops working in some scenarios. The trick is just to minimize those to where they don't get on your nerves on a daily basis. C# will hopefully get there soon. * Unless, that is the language is designed from the ground up to support code reloading. Erlang/Elixir's runtime inspection/injection/behavior alteration capability is second to none, and largely replaces the role of a true/traditional debugger. And you can do other cool stuff with it like zero-downtime in-place deployments, though that doesn't exactly come for free.