[slazaro]

With Visual Studio, you can visually inline the definition of a function below its call by selecting "Peek Definition", which is close to what you're saying.

You can only do it one at a time, and it's for quick scanning of what the function does, though.

[timlyo]

I think Jetbrains ide's also have this. It's been a while though.

[tibbon]

Hmm, wonder if I can coax Sublime into doing that. It's a little closer to IDE-type functionality, which it's pretty weak on (refactoring is terrible for Ruby with it).