JetBrains also experimented with AST-based editing: https://www.jetbrains.com/help/mps/fast-track-to-mps.html#st...

An overview video: https://www.youtube.com/watch?v=XGm_khXZl44

I tried it, but it just was too clumsy. Sometimes refactoring/editing needs to go through phases where the AST is invalid, and MPS makes that just too clumsy.

But with AI this might be a different story.