nix-validation

Run `statix check .` to detect anti-patterns like bool comparisons and manual inherit, and `deadnix .` to find unused bindings. Use `statix fix .` and `deadnix -e .` to auto-apply fixes across the project.

Add treefmt-nix as a flake input, evaluate its module with `treefmt-nix.lib.evalModule`, and enable nixfmt, deadnix, and statix under `programs`. Expose the wrapper as `formatter` and the check under `checks`.

statix detects anti-patterns such as eta reduction, empty let-in, and unquoted URIs, while deadnix finds unused code like unreferenced let bindings and lambda arguments. They complement each other and are commonly run together via treefmt-nix.

deadnix flags `self` in flake outputs and module arguments used only in imports as unused. Hide `self` with a `...` pattern, prefix intentionally unused variables with `_`, or use flags like `--no-lambda-arg` to reduce noise.

Run `nix-instantiate --parse file.nix` for an instant syntax-only check without evaluation. For full evaluation including all checks, use `nix flake check`, which is slower but thorough.

Define a devShell with nixfmt, statix, and deadnix, then install a git pre-commit hook that runs these tools on staged `.nix` files. Alternatively, integrate pre-commit-hooks.nix as a flake check.