This was a really great read! I'm wrote the tree sitter grammar for the Unison programming language, and discovered I really like the work involved in pattern matching that writing tokenizers and parsers comes down to. It also gives you an in-depth understanding of how the language works that you've writing a parser for, and how tooling works.

Like if you have an AST with the ability to map onto code that is displayed in your IDE, the algorithm for an IDE to refactor a variable name is to traverse up the AST until you get to the variable's declaration and then traverse all sibling trees, changing each matching name, but stopping a traversal whenever you encounter a new binding with same name. Code folding is to identify the categories of node that are "foldable" and then you hide every child of that node. Etc. It's all tree traversal algorithms.

It gives you a deep appreciation for how powerful the tooling can be thanks to proper parsing.