Method try_eval_nat_value_for_pred

crates/kernel/src/whnf.rs:2079–2084

A shallow Nat evaluator for bounded native helpers. This is intentionally not used by `Nat.beq`/`Nat.ble` primitive reduction; those follow Lean and only compare WHNF'd literal-extension arguments. BitVec helpers use this narrower evaluator to avoid forcing large recursive Nat models when only a bounded width is useful.

(
    &mut self,
    e: &KExpr<M>,
  )

    }

    let ExprData::Const(rec_id, rec_us, _) = head.data() else {
      return None;
    };
    if rec_id.addr != self.prims.decidable_rec.addr || args.len() < 5 {
      return None;
    }

    let ExprData::Lam(motive_name, motive_bi, motive_dom, _, _) =
      args[1].data()