use rustc_data_structures::sync::AtomicU64;
use rustc_middle::arena::Arena;
-use rustc_middle::dep_graph::{self, DepKindStruct, SerializedDepNodeIndex};
+use rustc_middle::dep_graph::{self, DepKindStruct};
use rustc_middle::ty::query::{query_keys, query_storage, query_stored, query_values};
use rustc_middle::ty::query::{ExternProviders, Providers, QueryEngine};
use rustc_middle::ty::{self, TyCtxt};