If you want syntax highlighting, the AST is enough to generate pretty colours for the source code. If you want semantic highlighting… sure, that's another story

If you want syntax highlighting, the AST is enough to generate pretty colours for the source code. If you want semantic highlighting… sure, that's another story entirely. And even then you don't necessarily have to do as much work as the compiler itself. And don't even try to be smart with dynamically typed languages, it cannot possibly be reliable, short of actually executing the program. If your program are short enough you won't need it, and if you do need such static analysis… consider switching to a statically typed language instead.