You can actually do something similar (much more limited, it sounds like) on Java, of all things.

https://devblogs.microsoft.com/java/hot-code-replacement-for...

As long as it doesn't change the class signature, you can happily edit-save-replace code, and it jumps to the top of the method you're editing. It's basically instant, so you don't suffer the javac and JVM startup cost.

I don't think I can do the same in more dynamic languages, like Ruby or Python. Or, maybe, my IDEs don't support it (IntelliJ suite).