Thank you, this kind of design doc is exactly what I was looking for. I'm not really familiar with Microsoft's ecosystem, but I mentioned it in the blog post because I suspected that they had the most advanced technology in this domain.
From that doc, which I plan to read thoroughly:
This enables the second attribute of syntax trees. A syntax tree obtained from the parser is completely round-trippable back to the text it was parsed from. From any syntax node, it is possible to get the text representation of the sub-tree rooted at that node.
This is true with my representation too, but I don't actually attach "trivia" to trees. Instead I just have every node store a bunch of span IDs. And then if you want to reconstruct the text, then you just take min(span_ids of node) and max(span_ids of node) and then concatenate those spans.
I also think the name "lossless syntax tree" makes sense, because they are describing very specific properties that ASTs and CSTs / parse trees don't have.
They also have an immutable property which is cool. I recall that Hjelsberg had a video on this:
