As soon as they have the code required to analyze your code, they aren't small, and as soon as they run that code they aren't fast. OTOH if that's the functiona

As soon as they have the code required to analyze your code, they aren't small, and as soon as they run that code they aren't fast. OTOH if that's the functionality you want, use eclipse, intellij (or a variant like RubyMine), and buy a beefy computer with an SSD. Eclipse isn't slow on my machine. EDIT: Now that I look at your two requirements, that's not at all hard for a language like C or java. I recall having this in 1993 on the OS/2 version of SlickEdit. vim or emacs will handle this no problem. If you want a GUI, Visual SlickEdit will do it, and for a whole bunch of languages on every OS.