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

10 files changed, 32 insertions, 26 deletions

diff --git a/compiler/rustc_next_trait_solver/src/canonicalizer.rs b/compiler/rustc_next_trait_solver/src/canonicalizer.rs
index 9cae7f27947..bbb4a162027 100644
--- a/compiler/rustc_next_trait_solver/src/canonicalizer.rs
+++ b/compiler/rustc_next_trait_solver/src/canonicalizer.rs
@@ -1,13 +1,11 @@
 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, TypeVisitableExt,
 };
 
 use crate::delegate::SolverDelegate;
diff --git a/compiler/rustc_next_trait_solver/src/coherence.rs b/compiler/rustc_next_trait_solver/src/coherence.rs
index 408742747c2..53290203600 100644
--- a/compiler/rustc_next_trait_solver/src/coherence.rs
+++ b/compiler/rustc_next_trait_solver/src/coherence.rs
@@ -3,8 +3,9 @@ use std::ops::ControlFlow;
 
 use derive_where::derive_where;
 use rustc_type_ir::inherent::*;
-use rustc_type_ir::visit::{TypeVisitable, TypeVisitableExt, TypeVisitor};
-use rustc_type_ir::{self as ty, InferCtxtLike, Interner};
+use rustc_type_ir::{
+    self as ty, InferCtxtLike, Interner, TypeVisitable, TypeVisitableExt, TypeVisitor,
+};
 use tracing::instrument;
 
 /// Whether we do the orphan check relative to this crate or to some remote crate.
diff --git a/compiler/rustc_next_trait_solver/src/delegate.rs b/compiler/rustc_next_trait_solver/src/delegate.rs
index 850d86d91e8..259b39e2b9e 100644
--- a/compiler/rustc_next_trait_solver/src/delegate.rs
+++ b/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>;
diff --git a/compiler/rustc_next_trait_solver/src/resolve.rs b/compiler/rustc_next_trait_solver/src/resolve.rs
index 71c87714745..992c5ddf504 100644
--- a/compiler/rustc_next_trait_solver/src/resolve.rs
+++ b/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,
+    TypeVisitableExt,
+};
 
 use crate::delegate::SolverDelegate;
 
diff --git a/compiler/rustc_next_trait_solver/src/solve/assembly/mod.rs b/compiler/rustc_next_trait_solver/src/solve/assembly/mod.rs
index bfb590e8767..384a304c4a9 100644
--- a/compiler/rustc_next_trait_solver/src/solve/assembly/mod.rs
+++ b/compiler/rustc_next_trait_solver/src/solve/assembly/mod.rs
@@ -3,11 +3,11 @@
 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, TypeVisitableExt as _, TypingMode, Upcast as _, elaborate,
+};
 use tracing::{debug, instrument};
 
 use super::trait_goals::TraitGoalProvenVia;
diff --git a/compiler/rustc_next_trait_solver/src/solve/assembly/structural_traits.rs b/compiler/rustc_next_trait_solver/src/solve/assembly/structural_traits.rs
index 93804b14125..a5142de2d39 100644
--- a/compiler/rustc_next_trait_solver/src/solve/assembly/structural_traits.rs
+++ b/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;
 
diff --git a/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/canonical.rs b/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/canonical.rs
index ce53a3968c7..ac6b521f665 100644
--- a/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/canonical.rs
+++ b/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;
diff --git a/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/mod.rs b/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/mod.rs
index e48ee71c858..0322c9e4ab0 100644
--- a/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/mod.rs
+++ b/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/mod.rs
@@ -2,16 +2,18 @@ use std::ops::ControlFlow;
 
 use derive_where::derive_where;
 #[cfg(feature = "nightly")]
-use rustc_macros::{HashStable_NoContext, TyDecodable, TyEncodable};
+use rustc_macros::{Decodable_NoContext, Encodable_NoContext, HashStable_NoContext};
 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, TypeSuperVisitable, TypeVisitable, TypeVisitableExt, TypeVisitor,
+    TypingMode,
+};
 use rustc_type_ir_macros::{Lift_Generic, TypeFoldable_Generic, TypeVisitable_Generic};
 use tracing::{instrument, trace};
 
@@ -129,7 +131,10 @@ where
 
 #[derive_where(Clone, Debug, Default; I: Interner)]
 #[derive(TypeVisitable_Generic, TypeFoldable_Generic, Lift_Generic)]
-#[cfg_attr(feature = "nightly", derive(TyDecodable, TyEncodable, HashStable_NoContext))]
+#[cfg_attr(
+    feature = "nightly",
+    derive(Decodable_NoContext, Encodable_NoContext, HashStable_NoContext)
+)]
 struct NestedGoals<I: Interner> {
     /// These normalizes-to goals are treated specially during the evaluation
     /// loop. In each iteration we take the RHS of the projection, replace it with
diff --git a/compiler/rustc_next_trait_solver/src/solve/normalizes_to/opaque_types.rs b/compiler/rustc_next_trait_solver/src/solve/normalizes_to/opaque_types.rs
index 60c20762a30..817dffa127b 100644
--- a/compiler/rustc_next_trait_solver/src/solve/normalizes_to/opaque_types.rs
+++ b/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};
diff --git a/compiler/rustc_next_trait_solver/src/solve/trait_goals.rs b/compiler/rustc_next_trait_solver/src/solve/trait_goals.rs
index 12a55664641..b72f776e5cb 100644
--- a/compiler/rustc_next_trait_solver/src/solve/trait_goals.rs
+++ b/compiler/rustc_next_trait_solver/src/solve/trait_goals.rs
@@ -5,9 +5,9 @@ use rustc_type_ir::fast_reject::DeepRejectCtxt;
 use rustc_type_ir::inherent::*;
 use rustc_type_ir::lang_items::TraitSolverLangItem;
 use rustc_type_ir::solve::CanonicalResponse;
-use rustc_type_ir::visit::TypeVisitableExt as _;
 use rustc_type_ir::{
-    self as ty, Interner, Movability, TraitPredicate, TypingMode, Upcast as _, elaborate,
+    self as ty, Interner, Movability, TraitPredicate, TypeVisitableExt as _, TypingMode,
+    Upcast as _, elaborate,
 };
 use tracing::{instrument, trace};