[abathur]

There's some prospect of Nickel (https://github.com/tweag/nickel) meeting this need, though haven't tried it and can't really vouch.

Typing might be really helpful for building your own layers up, but I don't know if it can meaningfully help with problems around consuming existing Nix ~APIs.

[evanjrowley]

Another new contender in the typed Nix space if Garn, which allows one to interact with Nix via TypeScript: https://news.ycombinator.com/item?id=38112416