Touch the oldest completed slice when marking a burrow for liquidation, again

Author: gkaracha

src/checker.ml

@@ -499,6 +499,25 @@ let[@inline] entrypoint_mark_for_liquidation (state, burrow_id: checker * burrow
     | None -> (Ligo.failwith error_GetEntrypointOptFailureBurrowSendTezTo : LigoOp.operation) in
   let ops = [op] in
 
+  (* Touch the oldest liquidation slice (if it exists). This should help the
+   * system keep the number of liquidation slices close to linear in many
+   * occasions. *)
+  let ops, state =
+    match liquidation_auction_oldest_completed_liquidation_slice state.liquidation_auctions with
+    | None -> (ops, state)
+    | Some leaf ->
+      let ops, state_liquidation_auctions, state_burrows, state_parameters, state_fa2_state =
+        touch_liquidation_slice ops state.liquidation_auctions state.burrows state.parameters state.fa2_state leaf in
+      ( ops,
+        { state with
+          liquidation_auctions = state_liquidation_auctions;
+          burrows = state_burrows;
+          parameters = state_parameters;
+          fa2_state = state_fa2_state;
+        }
+      )
+  in
+
   assert_checker_invariants state;
   (ops, state)