Remove extern crate rustc_middle from rustc_trait_selection.

compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs

@@ -16,6 +16,7 @@ use rustc_infer::traits::ObligationCause;
 use rustc_infer::traits::{Obligation, PolyTraitObligation, SelectionError};
 use rustc_middle::ty::fast_reject::{DeepRejectCtxt, TreatParams};
 use rustc_middle::ty::{self, ToPolyTraitRef, Ty, TypeVisitableExt};
+use rustc_middle::{bug, span_bug};
 
 use crate::traits;
 use crate::traits::query::evaluate_obligation::InferCtxtExt;

compiler/rustc_trait_selection/src/traits/select/confirmation.rs

@@ -17,6 +17,7 @@ use rustc_middle::ty::{
     self, GenericArgs, GenericArgsRef, GenericParamDefKind, ToPolyTraitRef, ToPredicate,
     TraitPredicate, Ty, TyCtxt,
 };
+use rustc_middle::{bug, span_bug};
 use rustc_span::def_id::DefId;
 
 use crate::traits::normalize::{normalize_with_depth, normalize_with_depth_to};

compiler/rustc_trait_selection/src/traits/select/mod.rs

@@ -36,6 +36,7 @@ use rustc_infer::infer::BoundRegionConversionTime;
 use rustc_infer::infer::BoundRegionConversionTime::HigherRankedType;
 use rustc_infer::infer::DefineOpaqueTypes;
 use rustc_infer::traits::TraitObligation;
+use rustc_middle::bug;
 use rustc_middle::dep_graph::dep_kinds;
 use rustc_middle::dep_graph::DepNodeIndex;
 use rustc_middle::mir::interpret::ErrorHandled;