Auto merge of #138464 - compiler-errors:less-type-ir, r=lcnr

Use `rustc_type_ir` directly less in the codebase

cc https://github.com/rust-lang/rust/issues/138449

This is a somewhat opinionated bundle of changes that will make working on https://github.com/rust-lang/rust/issues/138449 more easy, since it cuts out the bulk of the changes that would be necessitated by the lint. Namely:

1. Fold `rustc_middle::ty::fold` and `rustc_middle::ty::visit` into `rustc_middle::ty`. This is because we already reexport some parts of these modules into `rustc_middle::ty`, and there's really no benefit from namespacing away the rest of these modules's functionality given how important folding and visiting is to the type layer.
2. Rename `{Decodable,Encodable}_Generic` to `{Decodable,Encodable}_NoContext`[^why], change it to be "perfect derive" (`synstructure::AddBounds::Fields`), use it throughout `rustc_type_ir` instead of `TyEncodable`/`TyDecodable`.
3. Make `TyEncodable` and `TyDecodable` derives use `::rustc_middle::ty::codec::TyEncoder` (etc) for its generated paths, and move the `rustc_type_ir::codec` module back to `rustc_middle::ty::codec` :tada:.
4. Stop using `rustc_type_ir` in crates that aren't "fundamental" to the type system, namely middle/infer/trait-selection. This amounted mostly to changing imports from `use rustc_type_ir::...` to `use rustc_middle::ty::...`, but also this means that we can't glob import `TyKind::*` since the reexport into `rustc_middle::ty::TyKind` is a type alias. Instead, use the prefixed variants like `ty::Str` everywhere -- IMO this is a good change, since it makes it more regularized with most of the rest of the compiler.

[^why]: `_NoContext` is the name for derive macros with no additional generic bounds and which do "perfect derive" by generating bounds based on field types. See `HashStable_NoContext`.

I'm happy to cut out some of these changes into separate PRs to make landing it a bit easier, though I don't expect to have much trouble with bitrot.

r? lcnr

11 files changed, 14 insertions, 25 deletions

diff --git a/compiler/rustc_borrowck/src/diagnostics/region_errors.rs b/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
index 55b6367f35f..6b11f1a3681 100644
--- a/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
+++ b/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;
diff --git a/compiler/rustc_borrowck/src/lib.rs b/compiler/rustc_borrowck/src/lib.rs
index 7ae7936a2a2..07b3f3477a8 100644
--- a/compiler/rustc_borrowck/src/lib.rs
+++ b/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,
diff --git a/compiler/rustc_borrowck/src/region_infer/mod.rs b/compiler/rustc_borrowck/src/region_infer/mod.rs
index bb209a95711..a80d74d9e37 100644
--- a/compiler/rustc_borrowck/src/region_infer/mod.rs
+++ b/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};
diff --git a/compiler/rustc_borrowck/src/region_infer/opaque_types.rs b/compiler/rustc_borrowck/src/region_infer/opaque_types.rs
index 54f9e82dbb8..04839448596 100644
--- a/compiler/rustc_borrowck/src/region_infer/opaque_types.rs
+++ b/compiler/rustc_borrowck/src/region_infer/opaque_types.rs
@@ -5,11 +5,9 @@ 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,
+    TypeVisitableExt, TypingMode, fold_regions,
 };
 use rustc_span::Span;
 use rustc_trait_selection::regions::OutlivesEnvironmentBuildExt;
diff --git a/compiler/rustc_borrowck/src/renumber.rs b/compiler/rustc_borrowck/src/renumber.rs
index e355d2b415b..ff92b4168a8 100644
--- a/compiler/rustc_borrowck/src/renumber.rs
+++ b/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};
 
diff --git a/compiler/rustc_borrowck/src/type_check/constraint_conversion.rs b/compiler/rustc_borrowck/src/type_check/constraint_conversion.rs
index 8dff40ba6ac..6fbe1db6330 100644
--- a/compiler/rustc_borrowck/src/type_check/constraint_conversion.rs
+++ b/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};
diff --git a/compiler/rustc_borrowck/src/type_check/liveness/mod.rs b/compiler/rustc_borrowck/src/type_check/liveness/mod.rs
index f17ad23f4bf..b7a21cf48c8 100644
--- a/compiler/rustc_borrowck/src/type_check/liveness/mod.rs
+++ b/compiler/rustc_borrowck/src/type_check/liveness/mod.rs
@@ -4,8 +4,7 @@ use rustc_middle::mir::visit::{TyContext, Visitor};
 use rustc_middle::mir::{Body, Local, Location, SourceInfo};
 use rustc_middle::span_bug;
 use rustc_middle::ty::relate::Relate;
-use rustc_middle::ty::visit::TypeVisitable;
-use rustc_middle::ty::{GenericArgsRef, Region, RegionVid, Ty, TyCtxt};
+use rustc_middle::ty::{GenericArgsRef, Region, RegionVid, Ty, TyCtxt, TypeVisitable};
 use rustc_mir_dataflow::ResultsCursor;
 use rustc_mir_dataflow::impls::MaybeInitializedPlaces;
 use rustc_mir_dataflow::move_paths::MoveData;
diff --git a/compiler/rustc_borrowck/src/type_check/mod.rs b/compiler/rustc_borrowck/src/type_check/mod.rs
index d2eb7a52f78..94a5538ea3f 100644
--- a/compiler/rustc_borrowck/src/type_check/mod.rs
+++ b/compiler/rustc_borrowck/src/type_check/mod.rs
@@ -24,12 +24,10 @@ 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,
+    Dynamic, GenericArgsRef, OpaqueHiddenType, OpaqueTypeKey, RegionVid, Ty, TyCtxt,
+    TypeVisitableExt, UserArgs, UserTypeAnnotationIndex, fold_regions,
 };
 use rustc_middle::{bug, span_bug};
 use rustc_mir_dataflow::ResultsCursor;
diff --git a/compiler/rustc_borrowck/src/type_check/opaque_types.rs b/compiler/rustc_borrowck/src/type_check/opaque_types.rs
index 94b3d0c2bbf..8bab979a724 100644
--- a/compiler/rustc_borrowck/src/type_check/opaque_types.rs
+++ b/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};
 
diff --git a/compiler/rustc_borrowck/src/type_check/relate_tys.rs b/compiler/rustc_borrowck/src/type_check/relate_tys.rs
index 59e2eee41d3..02a41469c97 100644
--- a/compiler/rustc_borrowck/src/type_check/relate_tys.rs
+++ b/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};
 
diff --git a/compiler/rustc_borrowck/src/universal_regions.rs b/compiler/rustc_borrowck/src/universal_regions.rs
index cfac9b36832..f8e086b2bb7 100644
--- a/compiler/rustc_borrowck/src/universal_regions.rs
+++ b/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};