use crate::infer::lexical_region_resolve::RegionResolutionError;
use crate::infer::{SubregionOrigin, TypeTrace};
use crate::traits::ObligationCauseCode;
-use rustc_data_structures::stable_set::FxHashSet;
+use rustc_data_structures::fx::FxHashSet;
use rustc_errors::{Applicability, ErrorGuaranteed, MultiSpan};
use rustc_hir as hir;
use rustc_hir::intravisit::Visitor;