Whoa. This is very, very cool. I love TypeScript and its type system, and started using Nix in the past few years and wished it could have something similar.

I'm the author, you may find interesting:

1. Instead of building a new checker, TypeNix maps Nix's AST directly to TypeScript's AST. The standard TS binder, type checker and LSP work almost unchanged – they never know they’re looking at Nix

2. TypeNix on all 42K nixpkgs files in 13 seconds locally. Fixed-point patterns (makeExtensible, finalAttrs) typed via class transform with `this` binding.