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

14 files changed, 31 insertions, 38 deletions

diff --git a/compiler/rustc_infer/src/infer/canonical/canonicalizer.rs b/compiler/rustc_infer/src/infer/canonical/canonicalizer.rs
index c47f27e871f..307110d9fbc 100644
--- a/compiler/rustc_infer/src/infer/canonical/canonicalizer.rs
+++ b/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;
diff --git a/compiler/rustc_infer/src/infer/canonical/instantiate.rs b/compiler/rustc_infer/src/infer/canonical/instantiate.rs
index c10df2ec02e..f5ee5702d09 100644
--- a/compiler/rustc_infer/src/infer/canonical/instantiate.rs
+++ b/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};
 
diff --git a/compiler/rustc_infer/src/infer/canonical/mod.rs b/compiler/rustc_infer/src/infer/canonical/mod.rs
index fb5fc3a53fe..3be07dbe208 100644
--- a/compiler/rustc_infer/src/infer/canonical/mod.rs
+++ b/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};
diff --git a/compiler/rustc_infer/src/infer/canonical/query_response.rs b/compiler/rustc_infer/src/infer/canonical/query_response.rs
index 8a61631c69c..d53f631cc07 100644
--- a/compiler/rustc_infer/src/infer/canonical/query_response.rs
+++ b/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};
 
diff --git a/compiler/rustc_infer/src/infer/context.rs b/compiler/rustc_infer/src/infer/context.rs
index eae69ec3e0f..75affa13977 100644
--- a/compiler/rustc_infer/src/infer/context.rs
+++ b/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};
diff --git a/compiler/rustc_infer/src/infer/freshen.rs b/compiler/rustc_infer/src/infer/freshen.rs
index 74c8b463fc8..f2bb66ff736 100644
--- a/compiler/rustc_infer/src/infer/freshen.rs
+++ b/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;
 
diff --git a/compiler/rustc_infer/src/infer/lexical_region_resolve/mod.rs b/compiler/rustc_infer/src/infer/lexical_region_resolve/mod.rs
index 03c4614af13..91595de97f7 100644
--- a/compiler/rustc_infer/src/infer/lexical_region_resolve/mod.rs
+++ b/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;
diff --git a/compiler/rustc_infer/src/infer/mod.rs b/compiler/rustc_infer/src/infer/mod.rs
index 537e8119ada..fa8dea064da 100644
--- a/compiler/rustc_infer/src/infer/mod.rs
+++ b/compiler/rustc_infer/src/infer/mod.rs
@@ -28,14 +28,11 @@ 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, TypeVisitableExt, TypingEnv,
+    TypingMode, fold_regions,
 };
 use rustc_span::{Span, Symbol};
 use snapshot::undo_log::InferCtxtUndoLogs;
diff --git a/compiler/rustc_infer/src/infer/opaque_types/mod.rs b/compiler/rustc_infer/src/infer/opaque_types/mod.rs
index f6ef3f40e62..3fa1923121a 100644
--- a/compiler/rustc_infer/src/infer/opaque_types/mod.rs
+++ b/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};
diff --git a/compiler/rustc_infer/src/infer/relate/generalize.rs b/compiler/rustc_infer/src/infer/relate/generalize.rs
index ce2d07f4af9..e16212955ff 100644
--- a/compiler/rustc_infer/src/infer/relate/generalize.rs
+++ b/compiler/rustc_infer/src/infer/relate/generalize.rs
@@ -5,10 +5,9 @@ use rustc_data_structures::stack::ensure_sufficient_stack;
 use rustc_hir::def_id::DefId;
 use rustc_middle::bug;
 use rustc_middle::ty::error::TypeError;
-use rustc_middle::ty::visit::MaxUniverse;
 use rustc_middle::ty::{
-    self, AliasRelationDirection, InferConst, Term, Ty, TyCtxt, TypeVisitable, TypeVisitableExt,
-    TypingMode,
+    self, AliasRelationDirection, InferConst, MaxUniverse, Term, Ty, TyCtxt, TypeVisitable,
+    TypeVisitableExt, TypingMode,
 };
 use rustc_span::Span;
 use tracing::{debug, instrument, warn};
diff --git a/compiler/rustc_infer/src/infer/relate/higher_ranked.rs b/compiler/rustc_infer/src/infer/relate/higher_ranked.rs
index a12d83db91f..2143f72a3b0 100644
--- a/compiler/rustc_infer/src/infer/relate/higher_ranked.rs
+++ b/compiler/rustc_infer/src/infer/relate/higher_ranked.rs
@@ -1,9 +1,7 @@
 //! 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, TypeVisitableExt};
 use tracing::{debug, instrument};
 
 use super::RelateResult;
diff --git a/compiler/rustc_infer/src/infer/resolve.rs b/compiler/rustc_infer/src/infer/resolve.rs
index 6ec2e0152f0..4a99c220975 100644
--- a/compiler/rustc_infer/src/infer/resolve.rs
+++ b/compiler/rustc_infer/src/infer/resolve.rs
@@ -1,7 +1,8 @@
 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, TypeVisitableExt,
+};
 use rustc_type_ir::data_structures::DelayedMap;
 
 use super::{FixupError, FixupResult, InferCtxt};
diff --git a/compiler/rustc_infer/src/infer/snapshot/fudge.rs b/compiler/rustc_infer/src/infer/snapshot/fudge.rs
index 3a47b13665d..b5d3c26b05e 100644
--- a/compiler/rustc_infer/src/infer/snapshot/fudge.rs
+++ b/compiler/rustc_infer/src/infer/snapshot/fudge.rs
@@ -1,9 +1,11 @@
 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_type_ir::visit::TypeVisitableExt;
+use rustc_middle::ty::{
+    self, ConstVid, FloatVid, IntVid, RegionVid, Ty, TyCtxt, TyVid, TypeFoldable, TypeFolder,
+    TypeSuperFoldable,
+};
+use rustc_type_ir::TypeVisitableExt;
 use tracing::instrument;
 use ut::UnifyKey;
 
diff --git a/compiler/rustc_infer/src/traits/structural_impls.rs b/compiler/rustc_infer/src/traits/structural_impls.rs
index b346e193d0b..4335073d9bc 100644
--- a/compiler/rustc_infer/src/traits/structural_impls.rs
+++ b/compiler/rustc_infer/src/traits/structural_impls.rs
@@ -1,8 +1,8 @@
 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, TypeVisitable, TypeVisitor, try_visit,
+};
 
 use crate::traits;
 use crate::traits::project::Normalized;