Squash fold into ty

compiler/rustc_borrowck/src/diagnostics/region_errors.rs

@@ -14,9 +14,8 @@ use rustc_infer::infer::{NllRegionVariableOrigin, RelateParamBound};
 use rustc_middle::bug;
 use rustc_middle::hir::place::PlaceBase;
 use rustc_middle::mir::{AnnotationSource, ConstraintCategory, ReturnConstraint};
-use rustc_middle::ty::fold::fold_regions;
 use rustc_middle::ty::{
-    self, GenericArgs, Region, RegionVid, Ty, TyCtxt, TypeFoldable, TypeVisitor,
+    self, GenericArgs, Region, RegionVid, Ty, TyCtxt, TypeFoldable, TypeVisitor, fold_regions,
 };
 use rustc_span::{Ident, Span, kw};
 use rustc_trait_selection::error_reporting::InferCtxtErrorExt;

compiler/rustc_borrowck/src/lib.rs

@@ -35,8 +35,7 @@ use rustc_infer::infer::{
 };
 use rustc_middle::mir::*;
 use rustc_middle::query::Providers;
-use rustc_middle::ty::fold::fold_regions;
-use rustc_middle::ty::{self, ParamEnv, RegionVid, TyCtxt, TypingMode};
+use rustc_middle::ty::{self, ParamEnv, RegionVid, TyCtxt, TypingMode, fold_regions};
 use rustc_middle::{bug, span_bug};
 use rustc_mir_dataflow::impls::{
     EverInitializedPlaces, MaybeInitializedPlaces, MaybeUninitializedPlaces,

compiler/rustc_borrowck/src/region_infer/mod.rs

@@ -18,8 +18,7 @@ use rustc_middle::mir::{
     ReturnConstraint, TerminatorKind,
 };
 use rustc_middle::traits::{ObligationCause, ObligationCauseCode};
-use rustc_middle::ty::fold::fold_regions;
-use rustc_middle::ty::{self, RegionVid, Ty, TyCtxt, TypeFoldable, UniverseIndex};
+use rustc_middle::ty::{self, RegionVid, Ty, TyCtxt, TypeFoldable, UniverseIndex, fold_regions};
 use rustc_mir_dataflow::points::DenseLocationMap;
 use rustc_span::hygiene::DesugaringKind;
 use rustc_span::{DUMMY_SP, Span};

compiler/rustc_borrowck/src/region_infer/opaque_types.rs

@@ -5,11 +5,10 @@ use rustc_hir::def_id::LocalDefId;
 use rustc_infer::infer::outlives::env::OutlivesEnvironment;
 use rustc_infer::infer::{InferCtxt, NllRegionVariableOrigin, TyCtxtInferExt as _};
 use rustc_macros::extension;
-use rustc_middle::ty::fold::fold_regions;
 use rustc_middle::ty::visit::TypeVisitableExt;
 use rustc_middle::ty::{
     self, GenericArgKind, GenericArgs, OpaqueHiddenType, OpaqueTypeKey, Ty, TyCtxt, TypeFoldable,
-    TypingMode,
+    TypingMode, fold_regions,
 };
 use rustc_span::Span;
 use rustc_trait_selection::regions::OutlivesEnvironmentBuildExt;

compiler/rustc_borrowck/src/renumber.rs

@@ -2,8 +2,7 @@ use rustc_index::IndexSlice;
 use rustc_infer::infer::NllRegionVariableOrigin;
 use rustc_middle::mir::visit::{MutVisitor, TyContext};
 use rustc_middle::mir::{Body, ConstOperand, Location, Promoted};
-use rustc_middle::ty::fold::fold_regions;
-use rustc_middle::ty::{self, GenericArgsRef, Ty, TyCtxt, TypeFoldable};
+use rustc_middle::ty::{self, GenericArgsRef, Ty, TyCtxt, TypeFoldable, fold_regions};
 use rustc_span::Symbol;
 use tracing::{debug, instrument};
 

compiler/rustc_borrowck/src/type_check/constraint_conversion.rs

@@ -7,8 +7,9 @@ use rustc_infer::infer::{self, InferCtxt, SubregionOrigin};
 use rustc_infer::traits::query::type_op::DeeplyNormalize;
 use rustc_middle::bug;
 use rustc_middle::mir::{ClosureOutlivesSubject, ClosureRegionRequirements, ConstraintCategory};
-use rustc_middle::ty::fold::fold_regions;
-use rustc_middle::ty::{self, GenericArgKind, Ty, TyCtxt, TypeFoldable, TypeVisitableExt};
+use rustc_middle::ty::{
+    self, GenericArgKind, Ty, TyCtxt, TypeFoldable, TypeVisitableExt, fold_regions,
+};
 use rustc_span::Span;
 use rustc_trait_selection::traits::query::type_op::{TypeOp, TypeOpOutput};
 use tracing::{debug, instrument};

compiler/rustc_borrowck/src/type_check/mod.rs

@@ -24,12 +24,11 @@ use rustc_middle::mir::*;
 use rustc_middle::traits::query::NoSolution;
 use rustc_middle::ty::adjustment::PointerCoercion;
 use rustc_middle::ty::cast::CastTy;
-use rustc_middle::ty::fold::fold_regions;
 use rustc_middle::ty::visit::TypeVisitableExt;
 use rustc_middle::ty::{
     self, Binder, CanonicalUserTypeAnnotation, CanonicalUserTypeAnnotations, CoroutineArgsExt,
     Dynamic, GenericArgsRef, OpaqueHiddenType, OpaqueTypeKey, RegionVid, Ty, TyCtxt, UserArgs,
-    UserTypeAnnotationIndex,
+    UserTypeAnnotationIndex, fold_regions,
 };
 use rustc_middle::{bug, span_bug};
 use rustc_mir_dataflow::ResultsCursor;

compiler/rustc_borrowck/src/type_check/opaque_types.rs

@@ -2,10 +2,9 @@ use std::iter;
 
 use rustc_data_structures::fx::FxIndexMap;
 use rustc_middle::span_bug;
-use rustc_middle::ty::fold::fold_regions;
 use rustc_middle::ty::{
     self, GenericArgKind, OpaqueHiddenType, OpaqueTypeKey, Ty, TyCtxt, TypeSuperVisitable,
-    TypeVisitable, TypeVisitableExt, TypeVisitor,
+    TypeVisitable, TypeVisitableExt, TypeVisitor, fold_regions,
 };
 use tracing::{debug, trace};
 

compiler/rustc_borrowck/src/type_check/relate_tys.rs

@@ -10,9 +10,8 @@ use rustc_middle::mir::ConstraintCategory;
 use rustc_middle::span_bug;
 use rustc_middle::traits::ObligationCause;
 use rustc_middle::traits::query::NoSolution;
-use rustc_middle::ty::fold::FnMutDelegate;
 use rustc_middle::ty::relate::combine::{super_combine_consts, super_combine_tys};
-use rustc_middle::ty::{self, Ty, TyCtxt, TypeVisitableExt};
+use rustc_middle::ty::{self, FnMutDelegate, Ty, TyCtxt, TypeVisitableExt};
 use rustc_span::{Span, Symbol, sym};
 use tracing::{debug, instrument};
 

compiler/rustc_borrowck/src/universal_regions.rs

@@ -27,11 +27,10 @@ use rustc_hir::lang_items::LangItem;
 use rustc_index::IndexVec;
 use rustc_infer::infer::NllRegionVariableOrigin;
 use rustc_macros::extension;
-use rustc_middle::ty::fold::{TypeFoldable, fold_regions};
 use rustc_middle::ty::print::with_no_trimmed_paths;
 use rustc_middle::ty::{
     self, GenericArgs, GenericArgsRef, InlineConstArgs, InlineConstArgsParts, RegionVid, Ty,
-    TyCtxt, TypeVisitableExt,
+    TyCtxt, TypeFoldable, TypeVisitableExt, fold_regions,
 };
 use rustc_middle::{bug, span_bug};
 use rustc_span::{ErrorGuaranteed, kw, sym};

compiler/rustc_hir_analysis/src/check/check.rs

@@ -18,18 +18,18 @@ use rustc_middle::hir::nested_filter;
 use rustc_middle::middle::resolve_bound_vars::ResolvedArg;
 use rustc_middle::middle::stability::EvalResult;
 use rustc_middle::ty::error::TypeErrorToStringExt;
-use rustc_middle::ty::fold::{BottomUpFolder, fold_regions};
 use rustc_middle::ty::layout::{LayoutError, MAX_SIMD_LANES};
 use rustc_middle::ty::util::{Discr, IntTypeExt};
 use rustc_middle::ty::{
-    AdtDef, GenericArgKind, RegionKind, TypeSuperVisitable, TypeVisitable, TypeVisitableExt,
+    AdtDef, BottomUpFolder, GenericArgKind, RegionKind, TypeSuperVisitable, TypeVisitable,
+    TypeVisitableExt, fold_regions,
 };
 use rustc_session::lint::builtin::UNINHABITED_STATIC;
 use rustc_trait_selection::error_reporting::InferCtxtErrorExt;
 use rustc_trait_selection::error_reporting::traits::on_unimplemented::OnUnimplementedDirective;
 use rustc_trait_selection::traits;
 use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt;
-use rustc_type_ir::fold::TypeFoldable;
+use rustc_type_ir::TypeFoldable;
 use tracing::{debug, instrument};
 use ty::TypingMode;
 use {rustc_attr_parsing as attr, rustc_hir as hir};

compiler/rustc_hir_analysis/src/check/compare_impl_item.rs

@@ -12,10 +12,9 @@ use rustc_hir::{self as hir, AmbigArg, GenericParamKind, ImplItemKind, intravisi
 use rustc_infer::infer::{self, InferCtxt, TyCtxtInferExt};
 use rustc_infer::traits::util;
 use rustc_middle::ty::error::{ExpectedFound, TypeError};
-use rustc_middle::ty::fold::BottomUpFolder;
 use rustc_middle::ty::util::ExplicitSelf;
 use rustc_middle::ty::{
-    self, GenericArgs, GenericParamDefKind, Ty, TyCtxt, TypeFoldable, TypeFolder,
+    self, BottomUpFolder, GenericArgs, GenericParamDefKind, Ty, TyCtxt, TypeFoldable, TypeFolder,
     TypeSuperFoldable, TypeVisitableExt, TypingMode, Upcast,
 };
 use rustc_middle::{bug, span_bug};

compiler/rustc_hir_analysis/src/collect.rs

@@ -33,9 +33,8 @@ use rustc_infer::infer::{InferCtxt, TyCtxtInferExt};
 use rustc_infer::traits::ObligationCause;
 use rustc_middle::hir::nested_filter;
 use rustc_middle::query::Providers;
-use rustc_middle::ty::fold::fold_regions;
 use rustc_middle::ty::util::{Discr, IntTypeExt};
-use rustc_middle::ty::{self, AdtKind, Const, IsSuggestable, Ty, TyCtxt, TypingMode};
+use rustc_middle::ty::{self, AdtKind, Const, IsSuggestable, Ty, TyCtxt, TypingMode, fold_regions};
 use rustc_middle::{bug, span_bug};
 use rustc_span::{DUMMY_SP, Ident, Span, Symbol, kw, sym};
 use rustc_trait_selection::error_reporting::traits::suggestions::NextTypeParamName;

compiler/rustc_hir_analysis/src/collect/item_bounds.rs

@@ -1,9 +1,9 @@
 use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
 use rustc_hir as hir;
 use rustc_infer::traits::util;
-use rustc_middle::ty::fold::shift_vars;
 use rustc_middle::ty::{
     self, GenericArgs, Ty, TyCtxt, TypeFoldable, TypeFolder, TypeSuperFoldable, TypeVisitableExt,
+    shift_vars,
 };
 use rustc_middle::{bug, span_bug};
 use rustc_span::Span;

compiler/rustc_hir_analysis/src/collect/type_of.rs

@@ -5,10 +5,9 @@ use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_hir::intravisit::VisitorExt;
 use rustc_hir::{self as hir, AmbigArg, HirId};
 use rustc_middle::query::plumbing::CyclePlaceholder;
-use rustc_middle::ty::fold::fold_regions;
 use rustc_middle::ty::print::with_forced_trimmed_paths;
 use rustc_middle::ty::util::IntTypeExt;
-use rustc_middle::ty::{self, IsSuggestable, Ty, TyCtxt, TypeVisitableExt};
+use rustc_middle::ty::{self, IsSuggestable, Ty, TyCtxt, TypeVisitableExt, fold_regions};
 use rustc_middle::{bug, span_bug};
 use rustc_span::{DUMMY_SP, Ident, Span};
 

compiler/rustc_hir_analysis/src/constrained_generic_params.rs

@@ -3,7 +3,7 @@ use rustc_middle::bug;
 use rustc_middle::ty::visit::{TypeSuperVisitable, TypeVisitor};
 use rustc_middle::ty::{self, Ty, TyCtxt};
 use rustc_span::Span;
-use rustc_type_ir::fold::TypeFoldable;
+use rustc_type_ir::TypeFoldable;
 use tracing::debug;
 
 #[derive(Clone, PartialEq, Eq, Hash, Debug)]

compiler/rustc_hir_analysis/src/delegation.rs

@@ -7,8 +7,7 @@ use std::assert_matches::debug_assert_matches;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::{DefId, LocalDefId};
-use rustc_middle::ty::fold::{TypeFoldable, TypeFolder, TypeSuperFoldable};
-use rustc_middle::ty::{self, Ty, TyCtxt};
+use rustc_middle::ty::{self, Ty, TyCtxt, TypeFoldable, TypeFolder, TypeSuperFoldable};
 use rustc_span::{ErrorGuaranteed, Span};
 use rustc_type_ir::visit::TypeVisitableExt;
 

compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_compatibility.rs

@@ -4,9 +4,8 @@ use rustc_errors::struct_span_code_err;
 use rustc_hir as hir;
 use rustc_hir::def::{DefKind, Res};
 use rustc_lint_defs::builtin::UNUSED_ASSOCIATED_TYPE_BOUNDS;
-use rustc_middle::ty::fold::BottomUpFolder;
 use rustc_middle::ty::{
-    self, DynKind, ExistentialPredicateStableCmpExt as _, Ty, TyCtxt, TypeFoldable,
+    self, BottomUpFolder, DynKind, ExistentialPredicateStableCmpExt as _, Ty, TyCtxt, TypeFoldable,
     TypeVisitableExt, Upcast,
 };
 use rustc_span::{ErrorGuaranteed, Span};

compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs

@@ -36,11 +36,10 @@ use rustc_infer::infer::{InferCtxt, TyCtxtInferExt};
 use rustc_infer::traits::ObligationCause;
 use rustc_middle::middle::stability::AllowUnstable;
 use rustc_middle::mir::interpret::LitToConstInput;
-use rustc_middle::ty::fold::fold_regions;
 use rustc_middle::ty::print::PrintPolyTraitRefExt as _;
 use rustc_middle::ty::{
     self, Const, GenericArgKind, GenericArgsRef, GenericParamDefKind, ParamEnv, Ty, TyCtxt,
-    TypeVisitableExt, TypingMode,
+    TypeVisitableExt, TypingMode, fold_regions,
 };
 use rustc_middle::{bug, span_bug};
 use rustc_session::lint::builtin::AMBIGUOUS_ASSOCIATED_ITEMS;

compiler/rustc_hir_analysis/src/hir_wf_check.rs

@@ -4,8 +4,7 @@ use rustc_infer::infer::TyCtxtInferExt;
 use rustc_infer::traits::{ObligationCause, WellFormedLoc};
 use rustc_middle::bug;
 use rustc_middle::query::Providers;
-use rustc_middle::ty::fold::fold_regions;
-use rustc_middle::ty::{self, TyCtxt, TypingMode};
+use rustc_middle::ty::{self, TyCtxt, TypingMode, fold_regions};
 use rustc_span::def_id::LocalDefId;
 use rustc_trait_selection::traits::{self, ObligationCtxt};
 use tracing::debug;

compiler/rustc_hir_typeck/src/demand.rs

@@ -6,9 +6,8 @@ use rustc_infer::infer::DefineOpaqueTypes;
 use rustc_middle::bug;
 use rustc_middle::ty::adjustment::AllowTwoPhase;
 use rustc_middle::ty::error::{ExpectedFound, TypeError};
-use rustc_middle::ty::fold::BottomUpFolder;
 use rustc_middle::ty::print::with_no_trimmed_paths;
-use rustc_middle::ty::{self, AssocItem, Ty, TypeFoldable, TypeVisitableExt};
+use rustc_middle::ty::{self, AssocItem, BottomUpFolder, Ty, TypeFoldable, TypeVisitableExt};
 use rustc_span::{DUMMY_SP, Ident, Span, sym};
 use rustc_trait_selection::infer::InferCtxtExt;
 use rustc_trait_selection::traits::ObligationCause;

compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs

@@ -21,11 +21,10 @@ use rustc_infer::infer::canonical::{Canonical, OriginalQueryValues, QueryRespons
 use rustc_infer::infer::{DefineOpaqueTypes, InferResult};
 use rustc_lint::builtin::SELF_CONSTRUCTOR_FROM_OUTER_ITEM;
 use rustc_middle::ty::adjustment::{Adjust, Adjustment, AutoBorrow, AutoBorrowMutability};
-use rustc_middle::ty::fold::TypeFoldable;
 use rustc_middle::ty::visit::{TypeVisitable, TypeVisitableExt};
 use rustc_middle::ty::{
     self, AdtKind, CanonicalUserType, GenericArgKind, GenericArgsRef, GenericParamDefKind,
-    IsIdentity, Ty, TyCtxt, UserArgs, UserSelfTy,
+    IsIdentity, Ty, TyCtxt, TypeFoldable, UserArgs, UserSelfTy,
 };
 use rustc_middle::{bug, span_bug};
 use rustc_session::lint;

compiler/rustc_hir_typeck/src/method/confirm.rs

@@ -15,9 +15,9 @@ use rustc_middle::traits::ObligationCauseCode;
 use rustc_middle::ty::adjustment::{
     Adjust, Adjustment, AllowTwoPhase, AutoBorrow, AutoBorrowMutability, PointerCoercion,
 };
-use rustc_middle::ty::fold::TypeFoldable;
 use rustc_middle::ty::{
-    self, GenericArgs, GenericArgsRef, GenericParamDefKind, Ty, TyCtxt, TypeVisitableExt, UserArgs,
+    self, GenericArgs, GenericArgsRef, GenericParamDefKind, Ty, TyCtxt, TypeFoldable,
+    TypeVisitableExt, UserArgs,
 };
 use rustc_middle::{bug, span_bug};
 use rustc_span::{DUMMY_SP, Span};

compiler/rustc_hir_typeck/src/writeback.rs

@@ -11,9 +11,10 @@ use rustc_hir::{self as hir, AmbigArg, HirId};
 use rustc_middle::span_bug;
 use rustc_middle::traits::ObligationCause;
 use rustc_middle::ty::adjustment::{Adjust, Adjustment, PointerCoercion};
-use rustc_middle::ty::fold::{TypeFoldable, TypeFolder, fold_regions};
 use rustc_middle::ty::visit::TypeVisitableExt;
-use rustc_middle::ty::{self, Ty, TyCtxt, TypeSuperFoldable};
+use rustc_middle::ty::{
+    self, Ty, TyCtxt, TypeFoldable, TypeFolder, TypeSuperFoldable, fold_regions,
+};
 use rustc_span::{Span, sym};
 use rustc_trait_selection::error_reporting::infer::need_type_info::TypeAnnotationNeeded;
 use rustc_trait_selection::solve;

compiler/rustc_infer/src/infer/canonical/canonicalizer.rs

@@ -8,9 +8,9 @@
 use rustc_data_structures::fx::FxHashMap;
 use rustc_index::Idx;
 use rustc_middle::bug;
-use rustc_middle::ty::fold::{TypeFoldable, TypeFolder, TypeSuperFoldable};
 use rustc_middle::ty::{
-    self, BoundVar, GenericArg, InferConst, List, Ty, TyCtxt, TypeFlags, TypeVisitableExt,
+    self, BoundVar, GenericArg, InferConst, List, Ty, TyCtxt, TypeFlags, TypeFoldable, TypeFolder,
+    TypeSuperFoldable, TypeVisitableExt,
 };
 use smallvec::SmallVec;
 use tracing::debug;

compiler/rustc_infer/src/infer/canonical/instantiate.rs

@@ -8,8 +8,7 @@
 
 use rustc_macros::extension;
 use rustc_middle::bug;
-use rustc_middle::ty::fold::{FnMutDelegate, TypeFoldable};
-use rustc_middle::ty::{self, GenericArgKind, TyCtxt};
+use rustc_middle::ty::{self, FnMutDelegate, GenericArgKind, TyCtxt, TypeFoldable};
 
 use crate::infer::canonical::{Canonical, CanonicalVarValues};
 

compiler/rustc_infer/src/infer/canonical/mod.rs

@@ -24,8 +24,7 @@
 pub use instantiate::CanonicalExt;
 use rustc_index::IndexVec;
 pub use rustc_middle::infer::canonical::*;
-use rustc_middle::ty::fold::TypeFoldable;
-use rustc_middle::ty::{self, GenericArg, List, Ty, TyCtxt};
+use rustc_middle::ty::{self, GenericArg, List, Ty, TyCtxt, TypeFoldable};
 use rustc_span::Span;
 
 use crate::infer::{InferCtxt, RegionVariableOrigin};

compiler/rustc_infer/src/infer/canonical/query_response.rs

@@ -13,8 +13,7 @@ use std::iter;
 use rustc_index::{Idx, IndexVec};
 use rustc_middle::arena::ArenaAllocatable;
 use rustc_middle::mir::ConstraintCategory;
-use rustc_middle::ty::fold::TypeFoldable;
-use rustc_middle::ty::{self, BoundVar, GenericArg, GenericArgKind, Ty, TyCtxt};
+use rustc_middle::ty::{self, BoundVar, GenericArg, GenericArgKind, Ty, TyCtxt, TypeFoldable};
 use rustc_middle::{bug, span_bug};
 use tracing::{debug, instrument};
 

compiler/rustc_infer/src/infer/context.rs

@@ -1,10 +1,9 @@
 ///! Definition of `InferCtxtLike` from the librarified type layer.
 use rustc_hir::def_id::DefId;
 use rustc_middle::traits::ObligationCause;
-use rustc_middle::ty::fold::TypeFoldable;
 use rustc_middle::ty::relate::RelateResult;
 use rustc_middle::ty::relate::combine::PredicateEmittingRelation;
-use rustc_middle::ty::{self, Ty, TyCtxt};
+use rustc_middle::ty::{self, Ty, TyCtxt, TypeFoldable};
 use rustc_span::{DUMMY_SP, ErrorGuaranteed, Span};
 
 use super::{BoundRegionConversionTime, InferCtxt, RegionVariableOrigin, SubregionOrigin};

compiler/rustc_infer/src/infer/freshen.rs

@@ -35,8 +35,9 @@ use std::collections::hash_map::Entry;
 
 use rustc_data_structures::fx::FxHashMap;
 use rustc_middle::bug;
-use rustc_middle::ty::fold::TypeFolder;
-use rustc_middle::ty::{self, Ty, TyCtxt, TypeFoldable, TypeSuperFoldable, TypeVisitableExt};
+use rustc_middle::ty::{
+    self, Ty, TyCtxt, TypeFoldable, TypeFolder, TypeSuperFoldable, TypeVisitableExt,
+};
 
 use super::InferCtxt;
 

compiler/rustc_infer/src/infer/lexical_region_resolve/mod.rs

@@ -9,10 +9,9 @@ use rustc_data_structures::graph::implementation::{
 use rustc_data_structures::intern::Interned;
 use rustc_data_structures::unord::UnordSet;
 use rustc_index::{IndexSlice, IndexVec};
-use rustc_middle::ty::fold::{TypeFoldable, fold_regions};
 use rustc_middle::ty::{
     self, ReBound, ReEarlyParam, ReErased, ReError, ReLateParam, RePlaceholder, ReStatic, ReVar,
-    Region, RegionVid, Ty, TyCtxt,
+    Region, RegionVid, Ty, TyCtxt, TypeFoldable, fold_regions,
 };
 use rustc_middle::{bug, span_bug};
 use rustc_span::Span;

compiler/rustc_infer/src/infer/mod.rs

@@ -28,14 +28,12 @@ use rustc_middle::infer::canonical::{CanonicalQueryInput, CanonicalVarValues};
 use rustc_middle::mir::ConstraintCategory;
 use rustc_middle::traits::select;
 use rustc_middle::ty::error::{ExpectedFound, TypeError};
-use rustc_middle::ty::fold::{
-    BoundVarReplacerDelegate, TypeFoldable, TypeFolder, TypeSuperFoldable, fold_regions,
-};
 use rustc_middle::ty::visit::TypeVisitableExt;
 use rustc_middle::ty::{
-    self, ConstVid, FloatVid, GenericArg, GenericArgKind, GenericArgs, GenericArgsRef,
-    GenericParamDefKind, InferConst, IntVid, PseudoCanonicalInput, Ty, TyCtxt, TyVid,
-    TypeVisitable, TypingEnv, TypingMode,
+    self, BoundVarReplacerDelegate, ConstVid, FloatVid, GenericArg, GenericArgKind, GenericArgs,
+    GenericArgsRef, GenericParamDefKind, InferConst, IntVid, PseudoCanonicalInput, Ty, TyCtxt,
+    TyVid, TypeFoldable, TypeFolder, TypeSuperFoldable, TypeVisitable, TypingEnv, TypingMode,
+    fold_regions,
 };
 use rustc_span::{Span, Symbol};
 use snapshot::undo_log::InferCtxtUndoLogs;

compiler/rustc_infer/src/infer/opaque_types/mod.rs

@@ -5,9 +5,9 @@ use rustc_middle::bug;
 use rustc_middle::traits::ObligationCause;
 use rustc_middle::traits::solve::Goal;
 use rustc_middle::ty::error::{ExpectedFound, TypeError};
-use rustc_middle::ty::fold::BottomUpFolder;
 use rustc_middle::ty::{
-    self, OpaqueHiddenType, OpaqueTypeKey, Ty, TyCtxt, TypeFoldable, TypeVisitableExt,
+    self, BottomUpFolder, OpaqueHiddenType, OpaqueTypeKey, Ty, TyCtxt, TypeFoldable,
+    TypeVisitableExt,
 };
 use rustc_span::Span;
 use tracing::{debug, instrument};

compiler/rustc_infer/src/infer/relate/higher_ranked.rs

@@ -1,9 +1,8 @@
 //! Helper routines for higher-ranked things. See the `doc` module at
 //! the end of the file for details.
 
-use rustc_middle::ty::fold::FnMutDelegate;
 use rustc_middle::ty::visit::TypeVisitableExt;
-use rustc_middle::ty::{self, Ty, TyCtxt, TypeFoldable};
+use rustc_middle::ty::{self, FnMutDelegate, Ty, TyCtxt, TypeFoldable};
 use tracing::{debug, instrument};
 
 use super::RelateResult;

compiler/rustc_infer/src/infer/resolve.rs

@@ -1,7 +1,9 @@
 use rustc_middle::bug;
-use rustc_middle::ty::fold::{FallibleTypeFolder, TypeFolder, TypeSuperFoldable};
 use rustc_middle::ty::visit::TypeVisitableExt;
-use rustc_middle::ty::{self, Const, InferConst, Ty, TyCtxt, TypeFoldable};
+use rustc_middle::ty::{
+    self, Const, FallibleTypeFolder, InferConst, Ty, TyCtxt, TypeFoldable, TypeFolder,
+    TypeSuperFoldable,
+};
 use rustc_type_ir::data_structures::DelayedMap;
 
 use super::{FixupError, FixupResult, InferCtxt};

compiler/rustc_infer/src/infer/snapshot/fudge.rs

@@ -1,8 +1,10 @@
 use std::ops::Range;
 
 use rustc_data_structures::{snapshot_vec as sv, unify as ut};
-use rustc_middle::ty::fold::{TypeFoldable, TypeFolder, TypeSuperFoldable};
-use rustc_middle::ty::{self, ConstVid, FloatVid, IntVid, RegionVid, Ty, TyCtxt, TyVid};
+use rustc_middle::ty::{
+    self, ConstVid, FloatVid, IntVid, RegionVid, Ty, TyCtxt, TyVid, TypeFoldable, TypeFolder,
+    TypeSuperFoldable,
+};
 use rustc_type_ir::visit::TypeVisitableExt;
 use tracing::instrument;
 use ut::UnifyKey;

compiler/rustc_infer/src/traits/structural_impls.rs

@@ -1,8 +1,7 @@
 use std::fmt;
 
-use rustc_middle::ty::fold::{FallibleTypeFolder, TypeFoldable};
 use rustc_middle::ty::visit::{TypeVisitable, TypeVisitor, try_visit};
-use rustc_middle::ty::{self, TyCtxt};
+use rustc_middle::ty::{self, FallibleTypeFolder, TyCtxt, TypeFoldable};
 
 use crate::traits;
 use crate::traits::project::Normalized;

compiler/rustc_lint/src/opaque_hidden_inferred_bound.rs

@@ -1,9 +1,8 @@
 use rustc_hir::{self as hir, AmbigArg};
 use rustc_infer::infer::TyCtxtInferExt;
 use rustc_macros::{LintDiagnostic, Subdiagnostic};
-use rustc_middle::ty::fold::BottomUpFolder;
 use rustc_middle::ty::print::{PrintTraitPredicateExt as _, TraitPredPrintModifiersAndPath};
-use rustc_middle::ty::{self, Ty, TypeFoldable};
+use rustc_middle::ty::{self, BottomUpFolder, Ty, TypeFoldable};
 use rustc_session::{declare_lint, declare_lint_pass};
 use rustc_span::{Span, kw};
 use rustc_trait_selection::traits::{self, ObligationCtxt};

compiler/rustc_macros/src/type_foldable.rs

@@ -38,16 +38,16 @@ pub(super) fn type_foldable_derive(mut s: synstructure::Structure<'_>) -> proc_m
                 bind.to_token_stream()
             } else {
                 quote! {
-                    ::rustc_middle::ty::fold::TypeFoldable::try_fold_with(#bind, __folder)?
+                    ::rustc_middle::ty::TypeFoldable::try_fold_with(#bind, __folder)?
                 }
             }
         })
     });
 
     s.bound_impl(
-        quote!(::rustc_middle::ty::fold::TypeFoldable<::rustc_middle::ty::TyCtxt<'tcx>>),
+        quote!(::rustc_middle::ty::TypeFoldable<::rustc_middle::ty::TyCtxt<'tcx>>),
         quote! {
-            fn try_fold_with<__F: ::rustc_middle::ty::fold::FallibleTypeFolder<::rustc_middle::ty::TyCtxt<'tcx>>>(
+            fn try_fold_with<__F: ::rustc_middle::ty::FallibleTypeFolder<::rustc_middle::ty::TyCtxt<'tcx>>>(
                 self,
                 __folder: &mut __F
             ) -> Result<Self, __F::Error> {

compiler/rustc_middle/src/macros.rs

@@ -59,8 +59,8 @@ macro_rules! TrivialLiftImpls {
 macro_rules! TrivialTypeTraversalImpls {
     ($($ty:ty),+ $(,)?) => {
         $(
-            impl<'tcx> $crate::ty::fold::TypeFoldable<$crate::ty::TyCtxt<'tcx>> for $ty {
-                fn try_fold_with<F: $crate::ty::fold::FallibleTypeFolder<$crate::ty::TyCtxt<'tcx>>>(
+            impl<'tcx> $crate::ty::TypeFoldable<$crate::ty::TyCtxt<'tcx>> for $ty {
+                fn try_fold_with<F: $crate::ty::FallibleTypeFolder<$crate::ty::TyCtxt<'tcx>>>(
                     self,
                     _: &mut F,
                 ) -> ::std::result::Result<Self, F::Error> {
@@ -68,7 +68,7 @@ macro_rules! TrivialTypeTraversalImpls {
                 }
 
                 #[inline]
-                fn fold_with<F: $crate::ty::fold::TypeFolder<$crate::ty::TyCtxt<'tcx>>>(
+                fn fold_with<F: $crate::ty::TypeFolder<$crate::ty::TyCtxt<'tcx>>>(
                     self,
                     _: &mut F,
                 ) -> Self {

compiler/rustc_middle/src/mir/query.rs

@@ -13,8 +13,7 @@ use rustc_span::{Span, Symbol};
 use smallvec::SmallVec;
 
 use super::{ConstValue, SourceInfo};
-use crate::ty::fold::fold_regions;
-use crate::ty::{self, CoroutineArgsExt, OpaqueHiddenType, Ty, TyCtxt};
+use crate::ty::{self, CoroutineArgsExt, OpaqueHiddenType, Ty, TyCtxt, fold_regions};
 
 rustc_index::newtype_index! {
     #[derive(HashStable)]

compiler/rustc_middle/src/ty/context.rs

@@ -49,11 +49,10 @@ use rustc_session::{Limit, MetadataKind, Session};
 use rustc_span::def_id::{CRATE_DEF_ID, DefPathHash, StableCrateId};
 use rustc_span::{DUMMY_SP, Ident, Span, Symbol, kw, sym};
 use rustc_type_ir::TyKind::*;
-use rustc_type_ir::fold::TypeFoldable;
 use rustc_type_ir::lang_items::TraitSolverLangItem;
 pub use rustc_type_ir::lift::Lift;
 use rustc_type_ir::{
-    CollectAndApply, Interner, TypeFlags, WithCachedTypeInfo, elaborate, search_graph,
+    CollectAndApply, Interner, TypeFlags, TypeFoldable, WithCachedTypeInfo, elaborate, search_graph,
 };
 use tracing::{debug, instrument};
 

compiler/rustc_middle/src/ty/erase_regions.rs

@@ -1,8 +1,9 @@
 use tracing::debug;
 
 use crate::query::Providers;
-use crate::ty::fold::{TypeFoldable, TypeFolder, TypeSuperFoldable};
-use crate::ty::{self, Ty, TyCtxt, TypeFlags, TypeVisitableExt};
+use crate::ty::{
+    self, Ty, TyCtxt, TypeFlags, TypeFoldable, TypeFolder, TypeSuperFoldable, TypeVisitableExt,
+};
 
 pub(super) fn provide(providers: &mut Providers) {
     *providers = Providers { erase_regions_ty, ..*providers };

compiler/rustc_middle/src/ty/fold.rs

@@ -1,12 +1,11 @@
 use rustc_data_structures::fx::FxIndexMap;
 use rustc_hir::def_id::DefId;
 use rustc_type_ir::data_structures::DelayedMap;
-pub use rustc_type_ir::fold::{
-    FallibleTypeFolder, TypeFoldable, TypeFolder, TypeSuperFoldable, fold_regions, shift_region,
-    shift_vars,
-};
 
-use crate::ty::{self, Binder, BoundTy, Ty, TyCtxt, TypeVisitableExt};
+use crate::ty::{
+    self, Binder, BoundTy, Ty, TyCtxt, TypeFoldable, TypeFolder, TypeSuperFoldable,
+    TypeVisitableExt,
+};
 
 ///////////////////////////////////////////////////////////////////////////
 // Some sample folders
@@ -129,7 +128,7 @@ where
             ty::Bound(debruijn, bound_ty) if debruijn == self.current_index => {
                 let ty = self.delegate.replace_ty(bound_ty);
                 debug_assert!(!ty.has_vars_bound_above(ty::INNERMOST));
-                ty::fold::shift_vars(self.tcx, ty, self.current_index.as_u32())
+                ty::shift_vars(self.tcx, ty, self.current_index.as_u32())
             }
             _ => {
                 if !t.has_vars_bound_at_or_above(self.current_index) {
@@ -169,7 +168,7 @@ where
             ty::ConstKind::Bound(debruijn, bound_const) if debruijn == self.current_index => {
                 let ct = self.delegate.replace_const(bound_const);
                 debug_assert!(!ct.has_vars_bound_above(ty::INNERMOST));
-                ty::fold::shift_vars(self.tcx, ct, self.current_index.as_u32())
+                ty::shift_vars(self.tcx, ct, self.current_index.as_u32())
             }
             _ => ct.super_fold_with(self),
         }

compiler/rustc_middle/src/ty/generic_args.rs

@@ -8,16 +8,16 @@ use std::ptr::NonNull;
 use rustc_data_structures::intern::Interned;
 use rustc_errors::{DiagArgValue, IntoDiagArg};
 use rustc_hir::def_id::DefId;
-use rustc_macros::{HashStable, TyDecodable, TyEncodable, TypeFoldable, TypeVisitable, extension};
+use rustc_macros::{HashStable, TyDecodable, TyEncodable, TypeVisitable, extension};
 use rustc_serialize::{Decodable, Encodable};
 use rustc_type_ir::WithCachedTypeInfo;
 use smallvec::SmallVec;
 
 use crate::ty::codec::{TyDecoder, TyEncoder};
-use crate::ty::fold::{FallibleTypeFolder, TypeFoldable};
 use crate::ty::visit::{TypeVisitable, TypeVisitor, VisitorResult, walk_visitable_list};
 use crate::ty::{
-    self, ClosureArgs, CoroutineArgs, CoroutineClosureArgs, InlineConstArgs, Lift, List, Ty, TyCtxt,
+    self, ClosureArgs, CoroutineArgs, CoroutineClosureArgs, FallibleTypeFolder, InlineConstArgs,
+    Lift, List, Ty, TyCtxt, TypeFoldable,
 };
 
 pub type GenericArgKind<'tcx> = rustc_type_ir::GenericArgKind<TyCtxt<'tcx>>;

compiler/rustc_middle/src/ty/mod.rs

@@ -68,7 +68,7 @@ pub use self::context::{
     CtxtInterners, CurrentGcx, DeducedParamAttrs, Feed, FreeRegionInfo, GlobalCtxt, Lift, TyCtxt,
     TyCtxtFeed, tls,
 };
-pub use self::fold::{FallibleTypeFolder, TypeFoldable, TypeFolder, TypeSuperFoldable};
+pub use self::fold::*;
 pub use self::instance::{Instance, InstanceKind, ReifyReason, ShortInstance, UnusedGenericParams};
 pub use self::list::{List, ListWithCachedTypeInfo};
 pub use self::opaque_types::OpaqueTypeKey;
@@ -116,7 +116,7 @@ pub mod codec;
 pub mod error;
 pub mod fast_reject;
 pub mod flags;
-pub mod fold;
+mod fold;
 pub mod inhabitedness;
 pub mod layout;
 pub mod normalize_erasing_regions;

compiler/rustc_middle/src/ty/normalize_erasing_regions.rs

@@ -11,8 +11,10 @@ use rustc_macros::{HashStable, TyDecodable, TyEncodable};
 use tracing::{debug, instrument};
 
 use crate::traits::query::NoSolution;
-use crate::ty::fold::{FallibleTypeFolder, TypeFoldable, TypeFolder};
-use crate::ty::{self, EarlyBinder, GenericArgsRef, Ty, TyCtxt, TypeVisitableExt};
+use crate::ty::{
+    self, EarlyBinder, FallibleTypeFolder, GenericArgsRef, Ty, TyCtxt, TypeFoldable, TypeFolder,
+    TypeVisitableExt,
+};
 
 #[derive(Debug, Copy, Clone, HashStable, TyEncodable, TyDecodable)]
 pub enum NormalizationError<'tcx> {

compiler/rustc_middle/src/ty/opaque_types.rs

@@ -4,8 +4,9 @@ use rustc_span::def_id::DefId;
 use tracing::{debug, instrument, trace};
 
 use crate::error::ConstNotUsedTraitAlias;
-use crate::ty::fold::{TypeFolder, TypeSuperFoldable};
-use crate::ty::{self, GenericArg, GenericArgKind, Ty, TyCtxt, TypeFoldable};
+use crate::ty::{
+    self, GenericArg, GenericArgKind, Ty, TyCtxt, TypeFoldable, TypeFolder, TypeSuperFoldable,
+};
 
 pub type OpaqueTypeKey<'tcx> = rustc_type_ir::OpaqueTypeKey<TyCtxt<'tcx>>;
 

compiler/rustc_middle/src/ty/structural_impls.rs

@@ -17,10 +17,12 @@ use rustc_type_ir::visit::{VisitorResult, try_visit};
 use super::print::PrettyPrinter;
 use super::{GenericArg, GenericArgKind, Pattern, Region};
 use crate::mir::PlaceElem;
-use crate::ty::fold::{FallibleTypeFolder, TypeFoldable, TypeSuperFoldable};
 use crate::ty::print::{FmtPrinter, Printer, with_no_trimmed_paths};
 use crate::ty::visit::{TypeSuperVisitable, TypeVisitable, TypeVisitor};
-use crate::ty::{self, InferConst, Lift, Term, TermKind, Ty, TyCtxt};
+use crate::ty::{
+    self, FallibleTypeFolder, InferConst, Lift, Term, TermKind, Ty, TyCtxt, TypeFoldable,
+    TypeSuperFoldable,
+};
 
 impl fmt::Debug for ty::TraitDef {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {

compiler/rustc_middle/src/ty/util.rs

@@ -23,11 +23,10 @@ use super::TypingEnv;
 use crate::middle::codegen_fn_attrs::CodegenFnAttrFlags;
 use crate::mir;
 use crate::query::Providers;
-use crate::ty::fold::fold_regions;
 use crate::ty::layout::{FloatExt, IntegerExt};
 use crate::ty::{
     self, Asyncness, FallibleTypeFolder, GenericArgKind, GenericArgsRef, Ty, TyCtxt, TypeFoldable,
-    TypeFolder, TypeSuperFoldable, TypeVisitableExt, Upcast,
+    TypeFolder, TypeSuperFoldable, TypeVisitableExt, Upcast, fold_regions,
 };
 
 #[derive(Copy, Clone, Debug)]

compiler/rustc_middle/src/ty/visit.rs

@@ -1,7 +1,7 @@
 use std::ops::ControlFlow;
 
 use rustc_data_structures::fx::FxIndexSet;
-use rustc_type_ir::fold::TypeFoldable;
+use rustc_type_ir::TypeFoldable;
 pub use rustc_type_ir::visit::*;
 
 use crate::ty::{self, Binder, Ty, TyCtxt, TypeFlags};

compiler/rustc_next_trait_solver/src/canonicalizer.rs

@@ -1,13 +1,12 @@
 use std::cmp::Ordering;
 
 use rustc_type_ir::data_structures::{HashMap, ensure_sufficient_stack};
-use rustc_type_ir::fold::{TypeFoldable, TypeFolder, TypeSuperFoldable};
 use rustc_type_ir::inherent::*;
 use rustc_type_ir::solve::{Goal, QueryInput};
 use rustc_type_ir::visit::TypeVisitableExt;
 use rustc_type_ir::{
     self as ty, Canonical, CanonicalTyVarKind, CanonicalVarInfo, CanonicalVarKind, InferCtxtLike,
-    Interner,
+    Interner, TypeFoldable, TypeFolder, TypeSuperFoldable,
 };
 
 use crate::delegate::SolverDelegate;

compiler/rustc_next_trait_solver/src/delegate.rs

@@ -1,8 +1,7 @@
 use std::ops::Deref;
 
-use rustc_type_ir::fold::TypeFoldable;
 use rustc_type_ir::solve::{Certainty, Goal, NoSolution};
-use rustc_type_ir::{self as ty, InferCtxtLike, Interner};
+use rustc_type_ir::{self as ty, InferCtxtLike, Interner, TypeFoldable};
 
 pub trait SolverDelegate: Deref<Target = Self::Infcx> + Sized {
     type Infcx: InferCtxtLike<Interner = Self::Interner>;

compiler/rustc_next_trait_solver/src/resolve.rs

@@ -1,8 +1,9 @@
 use rustc_type_ir::data_structures::DelayedMap;
-use rustc_type_ir::fold::{TypeFoldable, TypeFolder, TypeSuperFoldable};
 use rustc_type_ir::inherent::*;
 use rustc_type_ir::visit::TypeVisitableExt;
-use rustc_type_ir::{self as ty, InferCtxtLike, Interner};
+use rustc_type_ir::{
+    self as ty, InferCtxtLike, Interner, TypeFoldable, TypeFolder, TypeSuperFoldable,
+};
 
 use crate::delegate::SolverDelegate;
 

compiler/rustc_next_trait_solver/src/solve/assembly/mod.rs

@@ -3,11 +3,10 @@
 pub(super) mod structural_traits;
 
 use derive_where::derive_where;
-use rustc_type_ir::fold::TypeFoldable;
 use rustc_type_ir::inherent::*;
 use rustc_type_ir::lang_items::TraitSolverLangItem;
 use rustc_type_ir::visit::TypeVisitableExt as _;
-use rustc_type_ir::{self as ty, Interner, TypingMode, Upcast as _, elaborate};
+use rustc_type_ir::{self as ty, Interner, TypeFoldable, TypingMode, Upcast as _, elaborate};
 use tracing::{debug, instrument};
 
 use super::trait_goals::TraitGoalProvenVia;

compiler/rustc_next_trait_solver/src/solve/assembly/structural_traits.rs

@@ -3,10 +3,12 @@
 
 use derive_where::derive_where;
 use rustc_type_ir::data_structures::HashMap;
-use rustc_type_ir::fold::{TypeFoldable, TypeFolder, TypeSuperFoldable};
 use rustc_type_ir::inherent::*;
 use rustc_type_ir::lang_items::TraitSolverLangItem;
-use rustc_type_ir::{self as ty, Interner, Movability, Mutability, Upcast as _, elaborate};
+use rustc_type_ir::{
+    self as ty, Interner, Movability, Mutability, TypeFoldable, TypeFolder, TypeSuperFoldable,
+    Upcast as _, elaborate,
+};
 use rustc_type_ir_macros::{TypeFoldable_Generic, TypeVisitable_Generic};
 use tracing::instrument;
 

compiler/rustc_next_trait_solver/src/solve/eval_ctxt/canonical.rs

@@ -12,10 +12,11 @@
 use std::iter;
 
 use rustc_index::IndexVec;
-use rustc_type_ir::fold::TypeFoldable;
 use rustc_type_ir::inherent::*;
 use rustc_type_ir::relate::solver_relating::RelateExt;
-use rustc_type_ir::{self as ty, Canonical, CanonicalVarValues, InferCtxtLike, Interner};
+use rustc_type_ir::{
+    self as ty, Canonical, CanonicalVarValues, InferCtxtLike, Interner, TypeFoldable,
+};
 use tracing::{debug, instrument, trace};
 
 use crate::canonicalizer::Canonicalizer;

compiler/rustc_next_trait_solver/src/solve/eval_ctxt/mod.rs

@@ -5,13 +5,15 @@ use derive_where::derive_where;
 use rustc_macros::{HashStable_NoContext, TyDecodable, TyEncodable};
 use rustc_type_ir::data_structures::{HashMap, HashSet, ensure_sufficient_stack};
 use rustc_type_ir::fast_reject::DeepRejectCtxt;
-use rustc_type_ir::fold::{TypeFoldable, TypeFolder, TypeSuperFoldable};
 use rustc_type_ir::inherent::*;
 use rustc_type_ir::relate::Relate;
 use rustc_type_ir::relate::solver_relating::RelateExt;
 use rustc_type_ir::search_graph::PathKind;
 use rustc_type_ir::visit::{TypeSuperVisitable, TypeVisitable, TypeVisitableExt, TypeVisitor};
-use rustc_type_ir::{self as ty, CanonicalVarValues, InferCtxtLike, Interner, TypingMode};
+use rustc_type_ir::{
+    self as ty, CanonicalVarValues, InferCtxtLike, Interner, TypeFoldable, TypeFolder,
+    TypeSuperFoldable, TypingMode,
+};
 use rustc_type_ir_macros::{Lift_Generic, TypeFoldable_Generic, TypeVisitable_Generic};
 use tracing::{instrument, trace};
 

compiler/rustc_next_trait_solver/src/solve/normalizes_to/opaque_types.rs

@@ -2,9 +2,8 @@
 //! behaves differently depending on the current `TypingMode`.
 
 use rustc_index::bit_set::GrowableBitSet;
-use rustc_type_ir::fold::fold_regions;
 use rustc_type_ir::inherent::*;
-use rustc_type_ir::{self as ty, Interner, TypingMode};
+use rustc_type_ir::{self as ty, Interner, TypingMode, fold_regions};
 
 use crate::delegate::SolverDelegate;
 use crate::solve::{Certainty, EvalCtxt, Goal, NoSolution, QueryResult, inspect};

compiler/rustc_sanitizers/src/cfi/typeid/itanium_cxx_abi/transform.rs

@@ -9,10 +9,9 @@ use std::iter;
 use rustc_hir as hir;
 use rustc_hir::LangItem;
 use rustc_middle::bug;
-use rustc_middle::ty::fold::{TypeFolder, TypeSuperFoldable};
 use rustc_middle::ty::{
     self, ExistentialPredicateStableCmpExt as _, Instance, InstanceKind, IntTy, List, TraitRef, Ty,
-    TyCtxt, TypeFoldable, TypeVisitableExt, UintTy,
+    TyCtxt, TypeFoldable, TypeFolder, TypeSuperFoldable, TypeVisitableExt, UintTy,
 };
 use rustc_span::def_id::DefId;
 use rustc_span::sym;

compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/util.rs

@@ -3,8 +3,7 @@
 
 use rustc_hir as hir;
 use rustc_hir::def_id::{DefId, LocalDefId};
-use rustc_middle::ty::fold::fold_regions;
-use rustc_middle::ty::{self, Binder, Region, Ty, TyCtxt, TypeFoldable};
+use rustc_middle::ty::{self, Binder, Region, Ty, TyCtxt, TypeFoldable, fold_regions};
 use rustc_span::Span;
 use tracing::instrument;
 

compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs

@@ -18,12 +18,14 @@ use rustc_middle::traits::SignatureMismatchData;
 use rustc_middle::traits::select::OverflowError;
 use rustc_middle::ty::abstract_const::NotConstEvaluatable;
 use rustc_middle::ty::error::{ExpectedFound, TypeError};
-use rustc_middle::ty::fold::{TypeFolder, TypeSuperFoldable};
 use rustc_middle::ty::print::{
     PrintPolyTraitPredicateExt, PrintTraitPredicateExt as _, PrintTraitRefExt as _,
     with_forced_trimmed_paths,
 };
-use rustc_middle::ty::{self, TraitRef, Ty, TyCtxt, TypeFoldable, TypeVisitableExt, Upcast};
+use rustc_middle::ty::{
+    self, TraitRef, Ty, TyCtxt, TypeFoldable, TypeFolder, TypeSuperFoldable, TypeVisitableExt,
+    Upcast,
+};
 use rustc_middle::{bug, span_bug};
 use rustc_span::{BytePos, DUMMY_SP, STDLIB_STABLE_CRATES, Span, Symbol, sym};
 use tracing::{debug, instrument};

compiler/rustc_trait_selection/src/solve/delegate.rs

@@ -8,8 +8,7 @@ use rustc_infer::infer::canonical::{
 };
 use rustc_infer::infer::{InferCtxt, RegionVariableOrigin, TyCtxtInferExt};
 use rustc_infer::traits::solve::Goal;
-use rustc_middle::ty::fold::TypeFoldable;
-use rustc_middle::ty::{self, Ty, TyCtxt, TypeVisitableExt as _};
+use rustc_middle::ty::{self, Ty, TyCtxt, TypeFoldable, TypeVisitableExt as _};
 use rustc_span::{DUMMY_SP, ErrorGuaranteed, Span};
 use rustc_type_ir::TypingMode;
 use rustc_type_ir::solve::{Certainty, NoSolution};

compiler/rustc_trait_selection/src/traits/mod.rs

@@ -32,10 +32,9 @@ pub use rustc_infer::traits::*;
 use rustc_middle::query::Providers;
 use rustc_middle::span_bug;
 use rustc_middle::ty::error::{ExpectedFound, TypeError};
-use rustc_middle::ty::fold::TypeFoldable;
 use rustc_middle::ty::visit::{TypeVisitable, TypeVisitableExt};
 use rustc_middle::ty::{
-    self, GenericArgs, GenericArgsRef, Ty, TyCtxt, TypeFolder, TypeSuperFoldable,
+    self, GenericArgs, GenericArgsRef, Ty, TyCtxt, TypeFoldable, TypeFolder, TypeSuperFoldable,
     TypeSuperVisitable, TypingMode, Upcast,
 };
 use rustc_span::def_id::DefId;

compiler/rustc_trait_selection/src/traits/project.rs

@@ -13,9 +13,8 @@ use rustc_infer::traits::{ObligationCauseCode, PredicateObligations};
 use rustc_middle::traits::select::OverflowError;
 use rustc_middle::traits::{BuiltinImplSource, ImplSource, ImplSourceUserDefinedData};
 use rustc_middle::ty::fast_reject::DeepRejectCtxt;
-use rustc_middle::ty::fold::TypeFoldable;
 use rustc_middle::ty::visit::TypeVisitableExt;
-use rustc_middle::ty::{self, Term, Ty, TyCtxt, TypingMode, Upcast};
+use rustc_middle::ty::{self, Term, Ty, TyCtxt, TypeFoldable, TypingMode, Upcast};
 use rustc_middle::{bug, span_bug};
 use rustc_span::sym;
 use rustc_type_ir::elaborate;

compiler/rustc_trait_selection/src/traits/query/normalize.rs

@@ -7,9 +7,10 @@ use rustc_data_structures::stack::ensure_sufficient_stack;
 use rustc_infer::traits::PredicateObligations;
 use rustc_macros::extension;
 pub use rustc_middle::traits::query::NormalizationResult;
-use rustc_middle::ty::fold::{FallibleTypeFolder, TypeFoldable, TypeSuperFoldable};
 use rustc_middle::ty::visit::{TypeSuperVisitable, TypeVisitable, TypeVisitableExt};
-use rustc_middle::ty::{self, Ty, TyCtxt, TypeVisitor, TypingMode};
+use rustc_middle::ty::{
+    self, FallibleTypeFolder, Ty, TyCtxt, TypeFoldable, TypeSuperFoldable, TypeVisitor, TypingMode,
+};
 use rustc_span::DUMMY_SP;
 use tracing::{debug, info, instrument};
 

compiler/rustc_trait_selection/src/traits/query/type_op/mod.rs

@@ -3,8 +3,7 @@ use std::fmt;
 use rustc_errors::ErrorGuaranteed;
 use rustc_infer::traits::PredicateObligations;
 use rustc_middle::traits::query::NoSolution;
-use rustc_middle::ty::fold::TypeFoldable;
-use rustc_middle::ty::{ParamEnvAnd, TyCtxt};
+use rustc_middle::ty::{ParamEnvAnd, TyCtxt, TypeFoldable};
 use rustc_span::Span;
 
 use crate::infer::canonical::{

compiler/rustc_trait_selection/src/traits/query/type_op/normalize.rs

@@ -3,8 +3,7 @@ use std::fmt;
 use rustc_middle::traits::ObligationCause;
 use rustc_middle::traits::query::NoSolution;
 pub use rustc_middle::traits::query::type_op::{DeeplyNormalize, Normalize};
-use rustc_middle::ty::fold::TypeFoldable;
-use rustc_middle::ty::{self, Lift, ParamEnvAnd, Ty, TyCtxt, TypeVisitableExt};
+use rustc_middle::ty::{self, Lift, ParamEnvAnd, Ty, TyCtxt, TypeFoldable, TypeVisitableExt};
 use rustc_span::Span;
 
 use crate::infer::canonical::{CanonicalQueryInput, CanonicalQueryResponse};

compiler/rustc_ty_utils/src/implied_bounds.rs

@@ -6,8 +6,7 @@ use rustc_hir::def::DefKind;
 use rustc_hir::def_id::LocalDefId;
 use rustc_middle::bug;
 use rustc_middle::query::Providers;
-use rustc_middle::ty::fold::fold_regions;
-use rustc_middle::ty::{self, Ty, TyCtxt};
+use rustc_middle::ty::{self, Ty, TyCtxt, fold_regions};
 use rustc_span::Span;
 
 pub(crate) fn provide(providers: &mut Providers) {

compiler/rustc_ty_utils/src/ty.rs

@@ -5,8 +5,9 @@ use rustc_hir::def::DefKind;
 use rustc_index::bit_set::DenseBitSet;
 use rustc_middle::bug;
 use rustc_middle::query::Providers;
-use rustc_middle::ty::fold::fold_regions;
-use rustc_middle::ty::{self, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable, TypeVisitor, Upcast};
+use rustc_middle::ty::{
+    self, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable, TypeVisitor, Upcast, fold_regions,
+};
 use rustc_span::DUMMY_SP;
 use rustc_span::def_id::{CRATE_DEF_ID, DefId, LocalDefId};
 use rustc_trait_selection::traits;

compiler/rustc_type_ir/src/binder.rs

@@ -859,7 +859,7 @@ impl<'a, I: Interner> ArgFolder<'a, I> {
         if self.binders_passed == 0 || !val.has_escaping_bound_vars() {
             val
         } else {
-            ty::fold::shift_vars(self.cx, val, self.binders_passed)
+            ty::shift_vars(self.cx, val, self.binders_passed)
         }
     }
 
@@ -867,7 +867,7 @@ impl<'a, I: Interner> ArgFolder<'a, I> {
         if self.binders_passed == 0 || !region.has_escaping_bound_vars() {
             region
         } else {
-            ty::fold::shift_region(self.cx, region, self.binders_passed)
+            ty::shift_region(self.cx, region, self.binders_passed)
         }
     }
 }

compiler/rustc_type_ir/src/lib.rs

@@ -25,7 +25,7 @@ pub mod data_structures;
 pub mod elaborate;
 pub mod error;
 pub mod fast_reject;
-pub mod fold;
+mod fold;
 #[cfg_attr(feature = "nightly", rustc_diagnostic_item = "type_ir_inherent")]
 pub mod inherent;
 pub mod ir_print;
@@ -66,6 +66,7 @@ pub use canonical::*;
 pub use codec::*;
 pub use const_kind::*;
 pub use flags::*;
+pub use fold::*;
 pub use generic_arg::*;
 pub use infer_ctxt::*;
 pub use interner::*;

compiler/rustc_type_ir_macros/src/lib.rs

@@ -93,7 +93,7 @@ fn type_foldable_derive(mut s: synstructure::Structure<'_>) -> proc_macro2::Toke
                 bind.to_token_stream()
             } else {
                 quote! {
-                    ::rustc_type_ir::fold::TypeFoldable::try_fold_with(#bind, __folder)?
+                    ::rustc_type_ir::TypeFoldable::try_fold_with(#bind, __folder)?
                 }
             }
         })
@@ -105,9 +105,9 @@ fn type_foldable_derive(mut s: synstructure::Structure<'_>) -> proc_macro2::Toke
     s.filter(|bi| !has_ignore_attr(&bi.ast().attrs, "type_foldable", "identity"));
     s.add_bounds(synstructure::AddBounds::Fields);
     s.bound_impl(
-        quote!(::rustc_type_ir::fold::TypeFoldable<I>),
+        quote!(::rustc_type_ir::TypeFoldable<I>),
         quote! {
-            fn try_fold_with<__F: ::rustc_type_ir::fold::FallibleTypeFolder<I>>(
+            fn try_fold_with<__F: ::rustc_type_ir::FallibleTypeFolder<I>>(
                 self,
                 __folder: &mut __F
             ) -> Result<Self, __F::Error> {

src/librustdoc/clean/auto_trait.rs

@@ -2,8 +2,7 @@ use rustc_data_structures::fx::{FxIndexMap, FxIndexSet, IndexEntry};
 use rustc_hir as hir;
 use rustc_infer::infer::region_constraints::{Constraint, RegionConstraintData};
 use rustc_middle::bug;
-use rustc_middle::ty::fold::fold_regions;
-use rustc_middle::ty::{self, Region, Ty};
+use rustc_middle::ty::{self, Region, Ty, fold_regions};
 use rustc_span::def_id::DefId;
 use rustc_span::symbol::{Symbol, kw};
 use rustc_trait_selection::traits::auto_trait::{self, RegionTarget};