auto arena = es.mem.exprs.alloc;
        decltype(attrs) foo = {std::move(attrs), arena};
        attrs = {};
        new (&attrs) decltype(attrs){std::move(foo), arena};

in nix_api_value.h, the EvalState argument of nix_init_path_string is not documented in the comment above. Is this a mistake? Are we intending to document every argument, and if so is that something we can check in CI?

https://github.com/NixOS/nix/blob/f4989b118bfba31f2e13504f2b950d07bf9539bb/src/libexpr-c/nix_api_value.h#L525-L532

/** @brief Set a path
 * @ingroup value_create
 * @param[out] context Optional, stores error information
 * @param[out] value Nix value to modify
 * @param[in] str the path string, copied
 * @return error code, NIX_OK on success.
 */
nix_err nix_init_path_string(nix_c_context * context, EvalState * s, nix_value * value, const char * str);