Syntactic aware transformations of JS source code: https://www.graspjs.com/blog/2014/01/07/refactoring-javascript-with-grasp
Really impressive and very general!
Related Posts
Exploring the design space and tradeoffs of programming language syntax, and syntactic sugar vs syntactic salt:
https://cs.lmu.edu/~ray/notes/syntaxdesign/
So far, all of the people trying difftastic with huge files have been using C or C++ source code. Maybe it's more common in those communities?
(Difftastic will eventually fall back to fast, dumb, line-based diffing if you give it a multi-megabyte source file.)
Encoding a spell checker in Typescript types: https://github.com/kkuchta/TSpell
(Very impressive, though unsurprisingly it's slow)