[lalos]

My guess is that the rust human error format is derived from some raw format that could easily be propagated to any other UX/UI and right now we are only familiar with the CLI format. I doubt they are keeping the state with a string of "^^^^" rather than just some 'error_starts_at_char: 8' and then some pretty print function prints the ^.

[estebank]

With --error-format=json you can get both the underlying encoded tree as well as the cli output within a field. The later is useful for tools that don't want to do anything special beyond presenting the output inline. All the pieces are there, there just hasn't been anyone with all of interest, expertise and time to work on it.