Isn't this more or less similar to what happens when developing in Java on Eclipse? To my knowledge, Eclipse does exactly the same thing: it compiles the code in real time, it loads the AST in memory and then it uses it to provide you powerful development tools. Your "live AST modification" looks a lot like debugging Java applications in Eclipse ;) Still, this seems a great idea! Even if it forces you to a single language/IDE combination (but that cannot be helped, I guess)