Yes. The compiler kept track of which source locations were impacted by which types of "method upgrades". Was something inlined? Dead code eliminated? Converted to a direct call to an internal entry point (avoiding dispatch)? Converted to a direct slot accessor? All of those could be colored differently.

I'm thinking of writing a blog post along the lines of "So, you thought that was a function call, eh?" as Dylan treats everything as a function call at the syntax level, but can go and optimize it into something better. That'll be a pretty complicated post though with a lot of Dylan + generated code examples and I know that I lost some people today by showing C in the type system overview post.