Explanation

Why this crate exists

Typechecking must work before a language has registered a checker — otherwise hnl typecheck on a fresh kit produces nothing at all. The bootstrap is deliberately shallow (structure and obvious mismatches) and exists to be replaced: dependent types, instance search and handler typing live in the NBE engine.

Where it sits

This crate belongs to the engine-* family. Plugins, kits and hosts reach it through the kit's operation slot, so the engine can be swapped without touching a language definition.

See the reference for the API and the how-to guides for tasks.