[jlarocco]

I've never heard of anybody doing it, but in theory it could work.

SBCL (and maybe others) use a "core image" to bootstrap at startup. It's not unheard of for people to build a custom core image with the packages they use a lot from the REPL. It's become less common as computers have gotten faster, and most people use systems like Quicklisp or Roswell to automatically get updates and load from source. Of course the SBCL core image is generated from the compiler source code when building it, and the dependencies are loaded and compiled from source initially, too, so there's still going to be source code files around.

You could, in theory, start with the compiled SBCL image, exclusively type code into the REPL, save the image and exit, and then restart with the new image and continue adding code via the REPL. I really doubt anybody uses that workflow exclusively, though. At the very least most people will eventually save the code they entered in the REPL into a source file once they've debugge it and got it working.

[pjmlp]

Ironically JIT caches are nothing other than core images.

Several JVM implementations, including the ART cousin, .NET, and apparently node.js is getting one as well.