Debugging and Problem Solving Expert

Tell us about a bug you encountered recently and how you solved it: see this commit. I would usually know to remove the element once used, but the cache array was discarded at the end of the function anyway and the problem only occurred if an edit within a file caused one language injection range to completely replace another's range (e.g. deleting a line when there's an equal-length line right below it), so this was very tricky and intermittent. Solved using methodical debugging process.