[pxc]

> Dynamic typing and lazy evaluation don't seem to mix.

Incidentally, this is one of the things that some of the people involved with the blog post in the OP have set out to fix. A few years ago, Théophane (author of the blog post) started an experiment to add gradual typing to Nix, which eventually became the start of Nickel: https://github.com/tweag/nickel

Today, Nickel development continues at Tweag, but now they have someone else, Yann Hamdaoui, driving the implementation forward. (I assume because he's a domain expert in programming languages.) Producing helpful error messages is one of the major goals of Nickel, as a potential successor language to Nix. All of the language design decisions are documented as GitHub issues on the repo, so if the technical side of this kind of problem is interesting to you, you may enjoy browsing that.

It appears that Nickel is very close to a usable state for early experimentation. You might be interested in cloning the repo and messing around with it!